This PDF file contains the front matter associated with SPIE Proceedings Volume10536, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

We demonstrate the extension of the wavelength range of InP- and GaSb-based buried tunnel junction VCSELs using type-II quantum wells. The InP-based devices emit at 2.5 μm and operate in continuous-wave (CW) up to 20°C, with a maximum single-mode output power above 500 μW. They exhibit a continuous electro-thermal tuning range of 5.2 nm. The GaSb-based devices emit up to 4 μm and operate in CW and pulsed mode until -7°C and 45°C, respectively. The maximum single-mode CW output power is 175 μW. A mode-hop free electro-thermal tuning of ~19 nm is achieved. These VCSELs are highly promising for gas sensing applications.

III-V/silicon photonic integrated circuits (ICs) promise to enable low cost and miniature optical sensors for trace-gas detection, bio-sensing and environmental monitoring. A lot of these applications can benefit from the availability of photonic ICs beyond the telecommunication wavelength range. The 2 μm wavelength range is of interest for spectroscopic detection of many important gases and blood constituents. In this contribution we will present 2 μmwavelength-range III-V/silicon photonic ICs consisting of tunable laser sources, photodetectors and silicon waveguide circuits. Silicon waveguides with a loss of ~0.5 dB/cm are obtained in a well-established silicon photonics platform. Based on the waveguides, low insertion loss (2-3 dB) and low crosstalk (25-30 dB) arrayed waveguide gratings (AWGs) are realized for the 2.3 μm wavelength range. Active opto-electronic components are integrated on the photonic IC by the heterogeneous integration of an InP-based type-II epitaxial layer stack on silicon. III-V-on-silicon 2.3 μm range distributed feedback (DFB) lasers can operate up to 25 °C in continuous-wave regime and shows an output power of 3 mW. By varying the silicon grating pitch, a DFB laser array with broad wavelength coverage from 2.28 μm to 2.43 μm is achieved. III-V-on-silicon photodetectors with the same epitaxial layer stack exhibit a responsivity of 1.6 A/W near 2.35 μm. In addition, we also report a 2 μm range GaSb/silicon hybrid external cavity laser using a silicon photonic IC for wavelength selective feedback. A wavelength tuning over 58 nm and side mode suppression ratio better than 60 dB is demonstrated.

Mid-infrared (MIR) spectroscopy is a reliable tool for the identification of gaseous and liquid mixtures due to their unique and inherent absorption spectra. Quantum Cascade (QC) Lasers and Interband Cascade Lasers are modern reliable sources to penetrate the MIR spectral range. To increase the functionality of QC devices we designed and optimized a QC material that can be used as a QC laser and as a QC detector for the very same MIR wavelength, respectively. Switching from laser to detector is achieved by biasing the semiconductor (lasing mode) or operate it without any electric field applied (detecting mode), respectively. Due to this functionality increase the on-chip integration of a designable QC light source, an interaction zone and a QC detector is now feasible and has been demonstrated recently. In this talk we present improved bi-functional QC material for the integration and further development of sensor systems, as well as different cavity concepts for gas and liquid sensing scenarios. Proof of concept sensing examples to demonstrate the integrated sensor systems will be given. Multi mode and single mode lasers made from bi-functional materials show comparable performance to regular state of the art QC lasers and no performance drop due to the additional detection functionality. While QC lasers are already accepted within the scientific community, QC detectors still need to be further promoted. Thus, in addition to the improvement of the bi-functional QC material, we demonstrated a single period quantum cascade photo-detector with a responsivity of up to 1.3 A/W.

Chalcogenide glasses are matchless materials as soon as mid, and even far, infrared technologies are concerned. Indeed they present transparency which extend from the UV to the far infrared depending of their composition. This exceptional transparency, associated with suitable viscosity/temperature dependence is a favorable context to seize the opportunity to develop innovative optical fibers, especially for mid-infrared sensing. Different families of optical fibers have been designed including tapered fibers, doped optical fibers, single mode fibers and microstructured fibers, depending on the targeted applications. The most promising application for such devices is related to the mid-IR sensing. This spectral range cover the domain where are located the main IR signatures of molecules and biomolecules. Thus, thanks to selenide glass fibers, Fiber Evanescent Wave Spectroscopy have been carried out to get some fruitful information in biology and medicine for example for early stage diagnosis or food safety. Alternatively, some special fibers have been prepared from rare earth doped selenide and sulfide glasses. These luminescent fibers, re-emitting light in the mid-infrared, were used to detect and monitor gaseous CO2. This work has been led in the frame a work program aiming at fighting against global warming by storing CO2 into geological underground sites. The Darwin mission of the European Space Agency also offered an exciting frame to develop innovative fibers. The motivation is to detect exo planet on which sign of life are possible. To achieve this goal, a new family of glasses, exclusively based on tellurium, have been developed suitable for CO2 detection at and beyond 15 micrometers. Single mode fibers working beyond this spectral domain have been developed on purpose and characterized.

We are developing midwave infrared (mid-IR) quantum cascade lasers (QCLs) and interband cascade lasers (ICLs) bonded to silicon. The heterogeneous integration of mid-IR photonic devices with silicon promises to enable low-cost, compact sensing and detection capabilities that are compatible with existing silicon photonic and electronic technologies. The first Fabry-Perot QCLs on silicon were bonded to pre-patterned silicon-on-nitride-on-insulator (SONOI) substrates. Lateral tapers in the III-V mesas transferred the optical mode from the hybrid III-V/Si active region into the passive silicon waveguides, with feedback provided by reflections from both the III-V tapers and the polished passive silicon facets. Lasing was observed at   4.8 m with threshold current densities as low as 1.6 kA/cm2 when operated in pulsed mode at T = 20 ºC. The first mid-IR DFB lasers integrated on silicon employed gratings patterned into the silicon waveguides before bonding. Over 200 mW of pulsed power was generated at room temperature, and operated to 100 °C with T0 = 199 K. Threshold current densities were measured below 1 kA/cm2.The grating imposed considerable wavelength selectivity and 22 nm of thermal tuning, even though the emission was not spectrally pure. Ongoing research focuses on flip-chip bonding to improve heat sinking for continuous-wave operation, and arrayed waveguide gratings for beam combining. ICLs have also been bonded to silicon and the GaSb substrate has been chemically removed with an InAsSb etch-stop layer. Tapered ICL ridges designed for lasing in a hybrid III-V/Si mode have been processed above passive silicon waveguides patterned on SOI. A goal is to combine the power generated by arrays of QCLs and ICLs residing on the same chip into a single, high-quality output beam.

Advances in dielectric metalenses in the visible which correct spherical aberration, coma and chromatic aberrations will be presented. The latter have been corrected at multiple wavelengths, in a LED bandwidth and broadband across the visible. Multifunctional components such as metalenses for chiral imaging, ultracompact spectrometers and axicons to create arbitrary Bessel beams will be presented along with broadband high efficiency holograms in the visible and spin-to-total angular momentum converters that create complex helical beams.

We have recently studied the physics and functionalities of metasurfaces in both reflective and transmissive geometries, with passive and actively tunable functionalities. In the first part, we first present a complete phase diagram to understand/predict the diversified and fascinating functionalities of metasurfaces in metal-insulator-metal (MIM) configuration [1], based on which we combined graphene with metasurface to achieve wide-range active THz phase modulation [2]. We next describe our recent efforts to realize tunable metasurfaces in the microwave regime to realize dynamically-controllable functionalities [3]. In the second part, we will describe our recent efforts to realize surface-plasmon-polariton (SPP) meta-couplers with very high efficiencies, based on gradient metasurfaces [4]. Finally, we show that 100%-efficiency photonic spin-Hall effect (PSHE) can be realized in geometric-phase metasurfaces with meta-atoms satisfying certain criterions, which help us design microwave metasurfaces exhibiting nearly 100% PSHE efficiency in both reflection and transmission geometries [5]. References [1] C. Qu et al., Phys. Rev. Lett. 115, 235503 (2015) [2] Z. Q. Miao et al., Phys. Rev. X 5, 041027 (2015). [3] H. X. Xu et al., Sci. Rep. 6 27503 (2016); Sci. Rep. 6 38255 (2016); Appl. Phys. Lett. 109, 193506 (2016) [4] W. J. Sun et al., Light: Science & Applications 5, 16003 (2016). [5] W. J. Luo et al., Adv. Opt. Mater. 3, 1102 (2015); Phys. Rev. Appl. (2017).

Metamaterials are artificially structured materials that have unconventional physical phenomena not found in nature materials. Metasurfaces, the two-dimensional equivalent of metamaterials, are periodic arrays of sub-wavelength engineered structures. Very recently, we have witnessed the rapid development of plasmonic and dielectric metasurfaces, which can enable flexible manipulation of structured light when meeting the structured metasurfaces. In this talk, we will review our recent research progress in plasmonic and dielectric metasurfaces on different platforms (metal, silicon, silica, fiber) for structured light manipulation: 1) broadband generation of orbital angular momentum (OAM) carrying vector beams using rectangular aperture array metasurfaces; 2) N-fold OAM multicasting using V-shaped antenna array metasurfaces; 3) design and fabrication of efficient reflective metasurfaces for the generation of OAM modes at 2 μm; 3) design and fabrication of metasurfaces on optical fiber facet for the generation of linearly polarized (LP) modes, linearly and circularly polarized OAM modes at 632.8 nm and 1550 nm; 4) design and fabrication of elliptical array all-dielectric metasurfaces for OAM modes generation and communications.

To generate Cherenkov radiation (CR) in natural medium, the electron energy threshold is higher than hundreds of keV. Even though various approaches were adopted, the high-energy electrons as high as tens of keV is still required in experiment. Here we proposed to eliminate the threshold of electron energy to generate CR with the help of hyperbolic metamaterial (HMM). The analytical and simulation results indicate that, even though electron energy is lower than 0.1keV, the CR could be obtained in HMM in a visible and near-infrared frequency region. Further, the on-chip integrated threshold-less CR source, consisted with a planar electron emitter, Au-SiO₂ multilayers HMM, and periodic metal nano-slits, has been realized. It is demonstrated that, with low-energy electrons (0.25-1.4keV), the CR is generated covering λ0=500~900nm. The electron energy generating CR experimentally is two~three orders of magnitude lower than that in natural media and artificial structures. As we know, this is the first on-chip integrated free electron light source benefiting from the threshold-less CR. Although less than 1% of the light energy could be coupled to free space, the total output light power still reaches 200nW, which is two orders of magnitude higher than free electron light source by using other nanostructures.

Silicon photonics is being considered as the future photonic platform for low power consumption optical communications. However, silicon is a centrosymmetric crystal, i.e. silicon doesn’t have Pockels effect. Nevertheless, breaking the crystal symmetry of silicon can be used to overcome this limitation. In this work, the crystal modification is achieved by depositing a SiN high-stress overlayer. Recent results on high-speed measurements will be presented and discussed. Both charge effects and Pockels effect induced under an electric field will be also analyzed.

Hollow-core photonic crystal fiber (HC-PCF) has been proved to be a versatile platform for lab-on-a-fiber applications. By filling the fiber with various gases, liquids or solid materials, the light-matter interaction could be greatly enhanced. Many novel optical phenomena that are unattainable in free-space could be easily identified inside the fiber. Such a platform offers a promising route for creating compact, integrable and biocompatible all-fiber multifunctional optical devices. Here, we review our recent progress in developing a novel HC-PCF coined "hollow-core negative curvature fiber" (NCF) that could provide light guidance at spectral ranges covering from UV, visible, NIR to MIR. These NCFs show attributes of low transmission loss, octave-spanning transmission bandwidth, high damage threshold and single modeness. As a proof-of-concept demonstration for lab-on-a-fiber applications, we filled one of the fibers with ethanol (refractive index 1.36) to form a liquid-core anti-resonant fiber. At a low volume of 1 μL, Raman signal from ethanol was observed at a pump power of 2 mW. Such a high performance NCF opens a window for applications in fiber-enhanced spectroscopy, biochemical sensing and nano-plasmonics.

The “Lab-on-Fiber” technology is an emerging research field which basically envisages the integration of functionalized materials and devices at micro- and nano-scale (i.e. the ‘labs’) with optical fibers, aimed to develop a novel generation of advanced “all-in-fiber” miniaturized probes, exploitable in many strategic sectors ranging from optical processing to environmental monitoring, life science, safety and security. The key concept is to transform an inert optical fiber into a multifunctional sensor where ultra compact labs are developed and ‘shrinked’ into a single optical fiber, thus destructively enlarging the conventional optical fiber sensors functionalities. Fusing the world of highly functionalized materials at nano- and microscale within a single optical fiber is providing the implementation of miniaturized and advanced “all-in-fiber” technological platforms as sophisticate multifunction sensing and actuating systems. At the same time, Microgels (MGs) are increasingly receiving attention by the photonics community as direct sensing materials for environmentally responsive systems. MGs are colloidal stable hydrogel particles that can be functionalized to respond to changes in temperature, pH, ionic strength, metal ions, antigens, and the presence of a number of biomolecules. Integration of smart responsive microgel with optical fiber is now opening a new route to the ”microgel photonics” technology focused on the development of novel advanced and multiresponsive optical probes with enhanced functionalities, especially exploitable for biosensing applications. The talk will address perspectives and challenges of this promising technological vision which can be in turn considered as a new relevant milestone in the Lab on Fiber Technology roadmap.

Smart functional fiber devices are indispensable for optical fiber based communication and sensing systems, in which the integration of fiber structure with smart semiconductor materials is essential. Among various choices, the colloidal quantum dot (CQD) is of great interests and its advantages includes: (a) the concentration of the photo-excited electrons can be relatively high due to the quantum confinement in the CQD, which means the refractive index of CQD could be altered with less power consumption; (b) CQD is a nanoscale dispersion solution thus the functional material can be deposited conformally on fiber, silicon chips or other complex structure surface; (c) CQD is a highly tunable material, and the chemical composition and operation wavelength can be specially designed for any wavelength window. In this work, we developed a platform to deposit the CQD with fiber structures for smart sensing and communication applications. First, we construct optical fiber antennas for gas sensing, in which the CQD conformally coated on the fiber surface behave like olfactory receptors. The gas molecules adsorbed on the quantum dots change the local carrier concentration in quantum dot solids, which leads to a change in their refractive index. This interaction of gas molecules with quantum dots could be transformed into optical signals through the optical fiber antennae. Owing to the large surface area, highly tunable physical and chemical properties of colloidal quantum dots, combined with the versatile fiber microstructure, the optical fiber antennae with quantum dots offer a new degree of freedom to precise, real-time and large-scale gas monitoring. Second, by using the light-excited carriers in CQD, a light controlled fiber device has been achieved as a delayed interferometric comb filter. The transmission spectrum can be easily tailored by mW-scale optical power. This device was applied in a 50 km standard single mode fiber (SSMF) based communication system with 12.5 Gbs On-Off-Keying (OOK) direct modulation for chirp management and dispersion compensation to achieve the error-free transmission.

This talk reviews the light-based physical, chemical and biological sensing approaches developed at the Institute for Photonics and Advanced Sensing (IPAS) and the Centre for Nanoscale BioPhotonics (CNBP) at Adelaide University utilizing microstructured optical fibers made of new materials, surfaces and structures. Suspended-, exposed- and hollow-core microstructured fibers offer important benefits compared to traditional techniques such as small sample volumes, high sensitivity, distributed or localised sensing, remote sensing, field-deploying capability, multiplexing. Depending on the intended application, a host of sensing modalities have been utilized including labelled fluorescence techniques, and label-free methods such as surface plasmon resonance, fiber Bragg gratings, interferometry and Raman scattering. The use of various functionalization techniques adds specificity to both ions and molecules to be sensed and enables re-usability of sensors.

Electric excitation of plasmonic guided modes in integrated circuits is important for the development of compact optical signal processing components as well integrated bio- and chemical sensing applications. Surface plasmons in purely metallic nanostructures are typically excited by external illumination or high-energy (keV) electron beams. Low-energy inelastic electron tunnelling is an alternative way to excite surface plasmons in ambient environment with the advantages of high compactness and background free operation, and has been widely investigated using metal-insulator-metal structures and in scanning tunnelling microscopy. Recently, it has been demonstrated that optical antennas or molecules can be used to strongly enhance the electron-photon conversion efficiency and/or control the related light emission on chip scale, opening up opportunities for the practical application of tunnelling-electron-driven plasmonic devices and components. At the same time, the tunnelling behavior is extremely sensitive to the immediate property change of a medium placed in the tunnel path, which holds great opportunities for the development of tunnelling-based devices for the dynamical control of plasmons or the detections of environmental changes with high sensitivity. Here we will discuss hot-electron excitation in electrically-driven plasmonic nanorod metamaterials and their applications for light emission and gas sensing, including hydrogen and oxygen gases. Electrically-driven plasmonic nanorod metamaterials comprise a fertile platform merging photonics, electronics and chemistry, opening up opportunities for developing electron tunnelling-based nanoscale devices for light generation and modulators and chemical sensing.

Surface plasmon (SP) resonance with light waves and/or excitons can be used to enhance the emission efficiencies of light-emitting materials and devices. This approach was experimentally demonstrated by our group for enhancing the visible emission from InGaN/GaN quantum wells (QWs). Exciton–SP coupling increases the spontaneous emission rates of the excited states, causes a relative reduction in nonradiative relaxation, and ultimately increases the internal quantum efficiencies (IQEs) of such devices. This method has the potential to enable the development of high-efficiency lightemitting diodes (LEDs), eventually leading to the replacement of fluorescent lights with solid-state light sources. Next important challenge is to extend this method into UV and IR wavelength regions. We found that Al is very useful for wider tuning of the plasmonic resonance from the deep UV to the visible wavelength region. The plasmonic tuning at the IR regions were also discussed by using tantalum nanoparticle. These tunable plasmonics over the UV-IR range should bring new possibilities of applications to plasmonics and lead to new class of several smart photonic and optoelectronic applications.

The ever-growing demands to compute information, store, and communicate generate a continuous driving force for transformative photonic technologies. On chip photonic integrated circuits (PICs) founded a roadmap for scaling down photonic modules to meet the challenges of bandwidth enhancement and power reduction. However, it also produces an even critical need for state-of-the-art devices and better materials. Lately, the material group of transparent conductive oxides (TCO) has appealed attentions for on-chip photonic components. In specific, indium tin oxide (ITO) has been found to have active large refractive index variations, which creates possibilities to realize high speed Electro-Optic (E-O) modulation of sub-diffraction device scales. This ITO based tapered plasmonic waveguide devices will combine the large E-O absorption effects of ITO with the localized SPPs and the ultra-strong optical field confinement. In this paper, we design the device which is fabricated on commercial silicon-on-insulator (SOI) platform integrated with a 3μm long, 300nm wide gold plasmonic slot waveguide, which can dynamically switch the optical transmission from high absorption mode by enhanced plasmonic E-O absorption to low loss mode. The active E-O modulation region consists of a metal-HfO₂-ITO capacitor that can electrically switch the ITO into ENZ with ultra-high modulation strength of 2.62dB/μm in simulation and 3.5dB extinction ratio in experiment. We also demonstrated the EA modulator a relative uniform E-O modulation within 1530~1600nm wavelength.

The fields of nanophotonics, plasmonics and optical metamaterials have enabled unprecedented ways to control the flow light at both the micro- and nanometer length scales, unfolding new optical phenomena, with a potential to reshape the existing optical technologies and create new ones. In this presentation, emerging plasmonic, metamaterial and metasurfaces concepts as well as material platforms will be discussed with the focus on practical photonic technologies for communication, quantum optics, bio-medical and energy applications.

Metasurface has recently become very appealing for wavefront control due to its simplicity in fabrication. Its high resolution in constructing a desired wavefront makes it a potential medium to create holographic images and ultrathin carpet cloaks for both electromagnetic and acoustic waves. In this work, we investigate how the holographic or projection principle can be utilized to achieve illusion effect in order to turn a particular object and source into a target configuration, with a close relationship to external cloaking in the framework of transformation optics. Our framework designs the required metasurface based on interference between the fields of the original and the target configurations. Such a metasurface then cancels the scattered field of the original object and projects the desired field of the target object at the same time. We discuss how an external cloak and a source or object shifter are possible through such a scheme. Possible experiments in both optics and elastic waves will also be discussed.

Over the last decades, the internet traffic has been rapidly growing resulting in Terabits per second aggregate data throughputs. We have also been witnessing that the electronic signal processing the way it is known today is approaching its limitations due to a grooving manifestation of the electronic bottleneck. It is believed that the ultra-fast signal processing based on all-optical integrated devices (passive, active or both) could play an important role in communication systems of the future. In this paper we discuss integrated devices, approaches and techniques we have developed and demonstrated towards achieving these ambitious goals and leading also to improve the scalability of optical networks such as Optical Code Division Multiple Access (OCDMA), namely: all-optical ultrafast demultiplexers, self-clocked all-optical time gates, all-optical thresholders, filters, AWGs, tunable optical delay lines, and devices for dispersion management.

Surface Plasmon polaritons have long been utilized to enhance and confine optical fields at the nanoscale. They have been proven effective in the control and enhancement of optical processes at metal-dielectric boundaries with a variety of applications including nonlinear optics. In this paper we review the application of plasmonic metasurfaces to enhance non-linear processes on semiconductors, crystals, 2-D materials (graphene) and in the metal itself forming the metasurface. We consider applications such as harmonic generation, the generation of vortex beams, and the enhancement of nonlinear processes in 2D materials (graphene).

As datacom link speeds approach 100 Gb/s per lane, higher complexity modulation formats such as PAM-4, PAM-8, and discrete multi-tone (DMT) have become favored by some despite their frequent need for forward-error correction (FEC) adding unnecessary latency. In this talk, we will describe a new optical-domain equalization scheme that leverages photonic integration to extend bandwidth without adding latency. We will describe our work using an IC-driven segmented electrode Mach Zehnder modulator that exploits this unique feed-forward equalization to generate 60-Gb/s on-off keyed (OOK) non-return-to-zero (NRZ) transmission with BER < 10^-12. The approach can deliver high link bandwidths with ultra-low latencies.

Luxtera and TSMC have jointly developed a new generation 100Gbps/λ-capable silicon photonics platform in a commercial 300 mm CMOS line. We present process details and the performance of the photonic device library.

We discuss microwave signal processing (MSP) using on-chip passive silicon photonic devices. By using the through port of a self-coupled micro-resonator (SCMR), a microwave photonic notch filter is achieved with a tuning range over 20 GHz and a maximum rejection ratio of 25 dB. Through frequency extracting from an optical frequency comb using the drop ports of SCMRs, photonic generation of 39-GHz and 29-GHz MMW signals are achieved. A photonic RF phase shifter based on a single micro-disk resonator can provide a phase-shift approaching 2π.

The rapid development of integrated photonic circuits demands for a technique to extract the magnitude and phase responses of the optical devices with ultrahigh resolution. Several methods, such as the modulation phase-shift approach and the interferometry approach, were proposed, which have a resolution of tens or hundreds of MHz. However, the bandwidth of the narrowest fiber Bragg grating (FBG) fabricated to date is below 9 MHz, and the Q-value of the optical micro-resonators has reached 6×10^10. To obtain sub-MHz measurement resolution, an optical vector analysis (OVA) based on microwave photonics to measure the phase and magnitude responses of the optical devices was proposed. With the electrical-to-optical and optical-to-electrical conversions, the relatively low-resolution laser wavelength sweeping in the optical domain can be replaced by ultrahigh resolution microwave frequency sweeping in the electrical domain. The measurement resolution of the OSSB-based OVA reaches 78 kHz in experiment and several hertz in theory. In this paper, the most recent works for extending the measurement range, increasing the measurement accuracy and enlarging the dynamic ranges of the microwave-photonics-based OVA are reviewed. An optical frequency comb (OFC) is used to extend the measurement range by segmental measurement, and the measurement errors caused by the high-order sidebands are eliminated by introducing a frequency shift to the optical carrier or adding a phase change to the sidebands in the left and right sides of the optical carrier. A prototype of the OVA was built, which was used for high-fineness devices fabrication, high-precision optical sensing, and on-chip optical signal processing. The prospective of this technique is discussed.

We develop the photonic approaches to manipulate microwave signals for applications such as wireless access networks, radar and warfare systems. Three system architectures are presented for the photonic manipulation of phase, frequency and modulation of microwave signals, respectively. We propose and experimentally demonstrate a simple and flexible photonic approach to implement single sideband modulation (SSB) modulation based on optical spectral filtering. The high order birefringent filter is realized through the cascaded Solc and Lyot Sagnac loops. The periodical response of the filter spectrum allows both the carrier wavelength and optical carrier to sideband ration (OCSR) to be tunable. SSB modulation over a frequency range from 5 to 40 GHz and tunable OCSR ranging from -9.174 to 34.408 dB are obtained. A frequency-multiplied and phase-shifted microwave signal is simultaneously realized by using birefringence effects in the high nonlinear fiber. The microwave signal at doubled- or quadrupled-frequency with a full 2π phase shift is obtained over a frequency range from 10 GHz to 30 GHz. We also experimentally demonstrate a novel approach to implement light controlled microwave frequency multiplication and single sideband (SSB) modulation simultaneously. By properly choosing operational parameters of the orthogonal polarized pump light to stimulate the nonlinear birefringent effect in highly nonlinear fiber, the frequency octupled microwave signal with the frequency up to 144 GHz can be generated. The SSB modulation with simultaneous suppression of the −1st and the +2nd order sidebands suppressed is also observed, and the SSB modulation from 10 to 40 GHz with OCSR ranging from −8.7 to 26.7 dB is experimentally demonstrated. The proposed techniques are vital to overcome the electronic bottlenecks, which will satisfy the worldwide demand for higher data rate and broadband transmission.

Microwave photonic systems have huge potential for both existing and future applications, including radar, radiofrequency sensing and modern wireless communications due to their distinct advantages in terms of ultra-wide bandwidth, flexible tunability, and immunity to electromagnetic interference. There is a strong research trend in microwave photonic systems towards integration and miniaturization, resulting in multiple radio frequency functions on a single chip which is both compact and light weight. Thus integrated microwave photonics has attracted a lot of attentions and achieves significant improvements in last ten years. In this paper, we will review some research progresses on silicon-based integrated microwave photonics in our group, including highly efficient micro heater on silicon photonic chip, chip-scale microwave waveform generation, on-chip true time delay, and microwave photonic processing and measurement. Our schemes are all fabricated on silicon-on-insulator chips and have advantages of compactness and capability to integrate with electronic units. These chips may motivate the great application potentials in silicon-based integrated microwave photonics.

Waveguide Bragg grating (WBG) devices on silicon constitute a particularly attractive solution for optical and microwave photonics (MWP) signal processing, thanks to their flexibility in producing arbitrarily defined amplitude and phase responses, by directly acting on perturbations of the grating profile, together with their high compactness compared to other integrated photonic filters. This talk will give a brief overview of advances in the field of integrated WBGs applied to microwave photonics and optical signal processing, with emphasis on a number of recent demonstrations. Examples of applications include THz‐bandwidth optical pulse shapers, wideband tunable RF filters, broadband true‐time‐delay lines and phase shifters, and instantaneous frequency measurement systems on‐chip.

Optomechanical crystals (also referred to as photonic–phononic crystals or phoxonic crystals) exploit the simultaneous photonic and phononic bandgaps in periodic nanostructures. They have been utilized to colocalize, couple, and transduce optical and mechanical (acoustic) waves for nonlinear interactions and precision measurements. Devices that involve standing or traveling acoustic waves of high frequencies usually have advantages in many applications. Here, we review recent progress in nano-optomechanical devices where the acoustic wave oscillates at microwave frequencies. We focus on our development of an optomechanical crystal cavity and a phoxonic crystal waveguide with special features. The development of near-infrared optomechanical crystal cavities has reached a bottleneck in reducing the mechanical modal mass. This is because the reduction of the spatial overlap between the optical and mechanical modes results in a reduced optomechanical coupling rate. With a novel optimization strategy, we have successfully designed an optomechanical crystal cavity in gallium nitride with the optical mode at the wavelength of 393.03 nm, the mechanical mode at 14.97 GHz, the mechanical modal mass of 22.83 fg, and the optomechanical coupling rate of 1.26 MHz. Stimulated Brillouin scattering (SBS) has been widely exploited for applications of optical communication, sensing, and signal processing. A recent challenge of its implementation in silicon waveguides is the weak per-unit-length SBS gain. Taking advantage of the strong optomechanical interaction, we have successfully engineered a phoxonic crystal waveguide structure, where the SBS gain coefficient is greater than 3×10⁴ W⁻¹ m⁻¹ in the entire C band with the highest value beyond 10^{6 W−1} m⁻¹, which is at least an order of magnitude higher than the existing demonstrations.

We present a programmable universal Si₃N₄ optical filter that can be reconfigured to various filter functions. The basic compositive structure is the Mach-Zehnder interferometer (MZI) with each arm coupled with a ring resonator. The input and output couplers in the MZI and the ring couplers are all tunable with coupling ratio varying from zero to one, making the device highly flexible. We theoretically investigate six configurations using the transfer function, revealing that the device can produce versatile filtering shape. Experimental demonstration of three configurations agree with the theoretical prediction. With a careful control of the ring coupling ratio, the filter can successfully generate sub-GHz passband that allows for high spectral-resolution microwave signal processing.

Non-dispersive infrared (NDIR) gas sensing technique analyses a target gas based on its characteristic absorption wavelengths in the infrared spectrum. In an NDIR gas sensor, infrared radiation from a broadband source passes through and interacts with the sample gases in a chamber. Due to the lack of pixel level spectral selectivity, the optical detector in the NDIR gas sensor has to pair with a bandpass filter to selectively detect the attenuation to the infrared energy caused by the target gas. To measure multiple target gases at the same time, one can simply implement many pairs of “bandpass filter + infrared detector”. However, this inevitably increases the overall size and complexity of the gas sensor. In this paper, we propose using narrowband plasmonic metamaterial absorber (PMA) to introduce pixel level spectral selectivity to infrared detectors and thus eliminating the requirement of separate bandpass filters. By inserting the PMA integrated narrowband detector array into the NDIR gas sensor, multiple gases can be analyzed with significantly reduced device footprint. When fully developed, the proposed device platform should be very useful in infrared spectroscopy.

Electro-Photonics combines the best of both electronics and optics to tackle the challenges of next generation optical communication networks in terms of capacity, flexibility, and energy efficiency. The optimal sharing of the processing work load between the electrical and optical domain brings considerable benefits to communication system complexity, performance, and construction as well as operational cost. As a key technology, photonic integrated circuits (PICs) play a critical role for the implementation of signal processing in the optical domain, serving for signal generation, switching, and acquisition. PICs point to advancing of network devices such as transmitters, receivers, and switches with desirable features of large bandwidth, high stability, precise control, easy tuning, and potential for low-cost fabrication by enabling miniaturization of complex optical systems on a chip scale. In this paper, we review the PIC research progress of the Monash Electro-Photonics Laboratory and its major contributions to the fields of optical communications and microwave photonics. We focus on applications in optical orthogonal frequency division multiplexing (O-OFDM), Nyquist wavelength division multiplexing (N-WDM), optical pulse manipulation, and programmable optical processors. The results of these works underline not only hardware fabrication capability and performance improvement for electrophotonics, but, more importantly, a new engineering paradigm that stimulates innovations in information and communication technologies.

The development of smart photonic networks has been developing for a long time in order to utilize the bandwidth/channels optimally and flexibly. As the link capacity increases dramatically by introducing advanced multiplexing technologies, the development of smart photonic networks is even becoming more important and more complicated. The key for the realization of smart photonic networks is reconfigurable photonic integrated devices and circuits. As silicon photonics has been developed as an excellent platform for PICs in the past years, in this paper we gives a review of our recent work on reconfigurable photonic integrated devices and circuits on silicon for wavelengthdivision-multiplexing (WDM), mode-division-multiplexing (MDM), as well as hybrid WDM-MDM systems. It includes (1) 2×2 optical switches, and (2) monolithically-integrated reconfigurable optical add-drop multiplexers (ROADMs).

CMOS nonlinear platforms are desirable for their ease of integration with CMOS electronics and large-scale manufacturability. A continuum of CMOS materials spanning from silicon dioxide to amorphous silicon exist. We have developed ultra-silicon-rich nitride possesses a large linear and nonlinear refractive index while still maintaining a sufficiently large bandgap to preclude two photon absorption at the telecommunications wavelength. We discuss recent developments of nonlinear optical signal processing leveraging the ultra-silicon-rich nitride platform. Optical parametric gain of up to 42.5dB is demonstrated, as well as supercontinuum generation. Enhanced optical nonlinearity using photonic crystal waveguides is also demonstrated, with the slow light effect enabling a nonlinear parameter of 1.97 × 10⁴ (Wm)⁻¹.

Surface-enhanced infrared absorption (SEIRA) is capable of identifying molecular fingerprints by resonant detection of infrared vibrational modes through the coupling with plasmonic modes of metallic nanostructures. However, SEIRA for on-chip gas sensing is still not very successful due to the intrinsically weak light-matter interaction between photons and gas molecules and the technical challenges in accumulating sufficient gas species in the vicinity of the spatially localized enhanced electric field, namely the “hot-spots”, generated through plasmonics. In this paper, we present a suspended silicon nitride (Si3N4) nano-membrane device by integrating plasmonic nano-patch gold antennas with metal-organic framework (MOF), which can largely adsorb carbon dioxide (CO2) through its nanoporous structure. Unlike conventional SEIRA sensing relying on highly localized hot-spots of plasmonic nanoantennas or nanoparticles, the device reported in this paper engineered the coupled surface plasmon polaritons in the metal-Si3N4 and metal-MOF interfaces to achieve strong optical field enhancement across the entire MOF film. We successfully demonstrated on-chip gas sensing of CO2 with more than 1,800× enhancement factors within a 2.7 μm thin film, and the detection limit was estimated to be about 52 ppm. This work proved the feasibility of developing a new type of on-chip SEIRA gas sensing using hybrid plasmonic-MOF nano-devices with miniaturized size and ultra-high sensitivity.

Coupling of electromagnetic energy from macroscale external light sources to nanometer-scale volumes associated with plasmonic and dielectric nanoantennas is utilized for excitation of Raman scattering on nanoparticles, excitation of semiconductor quantum dots, and resonant optical absorption. These phenomena are used in the context of detection of biomolecules for applications that include disease diagnostics from single-droplet test samples derived from bodily fluids.

Diamond’s nitrogen-vacancy (NV) center has been shown as a promising candidate for sensing applications and quantum computing because of its long electron spin coherence time and its ability to be found, manipulated and read out optically. An integrated photonics platform in diamond would be useful for NV-based magnetometry and quantum computing, in which NV centers are optically linked for long-range quantum entanglement due to the integration and stability provided by monolithic optical waveguides. Surface microchannels in diamond would be a great benefit for sensing applications, where NV centers could be used to probe biomolecules. In this work, we applied femtosecond laser writing to form buried 3D optical waveguides in diamond. By engineering the geometry of the type II waveguide, we obtained single mode guiding from visible to the infrared wavelengths. Further, we demonstrate the first Bragg waveguide in bulk diamond with narrowband reflection. We show the formation of single, high quality NV centers on demand in ultrapure diamond using a single pulse from a femtosecond laser. With these building blocks in place, we fabricated an integrated quantum photonic circuit containing optical waveguides coupled to NV centers deterministically placed within the waveguide. The single NVs were excited and their emission collected by the optical waveguides, allowing easy interfacing to standard optical fibers. We also report high aspect ratio surface microchannels, which we will integrate with laser-written NVs and waveguides, paving the way for ultrasensitive, nanoscale resolution biosensors.

We review our recent developments of the trimming techniques for correcting the operating point of ring resonator and Mach-Zehnder Interferometers (MZIs). This technology has been employed to fine-tune the effective index of waveguides, and therefore the operating point of photonic devices, enabling permanent correction of optical phase error induced by fabrication variations. Large resonance wavelength shift of ring resonators was demonstrated, and the shift can be tuned via changing the laser power used for annealing. A higher accuracy trimming technique with a scanning laser was also demonstrated to fine-tune the operating point of integrated MZIs. The effective index change of the optical mode is up to 0.19 in our measurements, which is approximately an order of magnitude improvement compared to previous work, whilst retaining similar excess optical loss.

Polarization-dependent periodic nanostructures inside various materials are successfully photoinduced by ultrafast laser pulses. These periodic nanostructures in various materials can be empirically classified into the following three types: (1) structural deficiency, (2) strained structure, (3) partial phase separation. Such self-assembled nanostructures exhibit not only optical anisotropy but also intriguing electric, thermal, and magnetic properties. We demonstrate new possibilities for functionalization of common materials ranging from an eternal 5D optical storage, a polarization imaging, to a thermoelectric conversion, based on the indicated phenomena.

Silicon photonics is considered as a promising technology to overcome the difficulties of the existing digital and analog optical communication systems, such as low integration, high cost, and high power consumption. Silicon optical modulator, as a component to transfer data from electronic domain to optical one, has attracted extensive attentions in the past decade. In this paper, I will review our efforts in developing high-speed silicon Mach-Zehnder optical modulators with large optical bandwidths. Firstly, I will introduce how to optimize the modulation efficiency, optical loss, electro-optical bandwith of the silicon optical modulator. The fabricated silicon Mach-Zehnder optical modulator has an electro-optical bandwidth of up to 39.8 GHz. When the device is optically biased at the quadrature pont, it has the dynamic extinction ratios of 6.5 dB, 5.9 dB and 5.2 dB at the speeds of 40 Gbps, 50 Gbps and 64 Gbps for OOK modulation. Secondly, I will introduce two types of silicon PAM-4 optical modulator. One is driven by a PAM-4 electrical signal and the other is driven by two binary electrical signals with different peak-to-peak voltages. Both two devices can generate PAM-4 optical signals at the speed of over 30 Gbaud in the wavelength of 1525-1565 nm. The corresponding bit error rates could reach as low as ~10−6, which is below the hard-decision forward error correction threshold of 3.8×10-3. Finally, I will introduce a silicon 16-QAM optical modulator, which is based on four Mach-Zehnder modulators driven by four binary electrical signals. With the simple electrical driving configuration, the device generates a 16-QAM optical signal at 20 Gbaud with an error vector magnitude of 13.7%.

Invited Talk

Increased traffic demands within and between data centers now necessitate low-cost and low-power systems with per-wavelength bit rates beyond what can be easily achieved using conventional on/off keying. We review spectrally efficient links based on direct detection, Stokes vector detection, coherent detection and deferentially coherent detection for data center applications. We show that limited spectral efficiency and power margin will inhibit scaling of direct detection-compatible formats beyond 100 Gbit/s. Stokes vector receivers can provide higher spectral efficiency without requiring a local oscillator laser, but require power-hungry analog-to-digital converters (ADCs) and digital signal processing (DSP). Similarly, existing DSP-based coherent systems designed for long-haul transmission may be excessively complex and power-hungry for short-reach data center links. We present low-power DSP-free coherent and differentially coherent alternatives that avoid high-speed ADCs and DSP and achieve similar performance to their DSP-based counterparts in intra-data center links and dispersion- compensated inter-data center links.

As data centers are becoming the nerve system of the modern information society, transmission of massive data to meet future demands requires continuous advancement in fiber-optic data link technology for data center networks. Advanced modulation formats with high spectral efficiency, such as DPQPSK, m-QAM, PAM etc. have been broadly used recently to improve the performance of high speed, large capacity fiber-optic links for telecom and datacom. These modulation formats will be reviewed for the needs of data center networks which require large throughputs with low cost, both in dollars and in watts. Alternative multi-dimensional polarization-based modulation formats, such as PolSK (Polarization Shift Keying) and SVM (Stokes Vector Modulation) will be explored for data center applications. Polarization-based modulation formats can provide 2-D, 3-D, or even 4-D symbol spaces using direct detection, which provide a possible way to improve data rate with low cost devices and components. Fundamental issues of polarization-based multi-dimensional modulation techniques will be evaluated and performance of Stokes vector receiver designs will be analyzed.

With the growing number of autonomous vehicles equipped with pulsed scanning LIDAR operating close to each other at the same time, one pulsed scanning LIDAR might receive laser pulses from other pulsed scanning LIDAR. The reception of unwanted laser pulses from other pulsed scanning LIDAR is called mutual interference. Due to Lambertian reflectance of the laser pulse, a mixture of incoherent laser pulses arrives at each pixel from different paths apart from the direct path. This effects cause significant distortions in the estimation of depth, especially near corners and convex areas of the scene. We proposed a new pulsed scanning LIDAR, which measures a scene without mutual interference. The emitted pulse of each pixel is modulated pulses by direct sequence optical code division multiple access (DS-OCDMA) techniques. The modulated pulses include unique device identification number (ID), the pixel position in the line, and checksum. It emits the modulated pulse, and receives the return light to the detector. We modeled the entire of the pulsed scanning LIDAR operation in the RSoft OptSim and validated the results obtained in modeling and simulation.

In this work we show preliminary advance in the development of a low-cost wrist wearable that measures levels of oxygen saturation levels in blood (SpO₂) and physical activity simultaneously. For the monitoring of SpO₂, we use pulse oximetry (a non invasive technique) by backscattering detection at the wrist. The device consists in an optoelectronics layer based on two light-emitting diodes (650nm and 960 nm) and a photodiode, a 3-axis gyroscope, a 3-axis accelerometer and a microcontroller capable of data processing and data transmission via bluetooth. In addition to, our sensor allows to save data for later analysis.

Light Detection And Ranging (LIDAR) offers univocal means of data capturing in remote sensing. It can collect intensity and distance data during day and night alike, albeit with limitations in accuracy due to weather conditions. Owing to weather conditions, factors affecting the performance of LIDAR intensity data include rain, haze, fog and snow. The effect of weather is twofold: scattering by aerosol and absorption by the presence of water drops. The prime objective of this research is to investigate how fog conditions deteriorate the quality of LIDAR intensity data. Experiment is carried out using Velodyne HDL-64E with 905nm wavelength. For experiment fog is classified into stable fog type 1 and stable fog type 2 categories based on the International Visibility Code (IVC). Since, theoretical approaches based on microphysical models are very complex and time consuming; hence, atmospheric attenuation of laser beam is calculated using empirical model which is based on visibility range estimate. Analysis is performed in order to discuss the results with respect to the effect on intensity data. The experiment is carried out with various levels of fog to view the impact of water droplets concentration and size on the accuracy of LIDAR data. The results show that fog attenuates the LIDAR laser pulse drastically, resulting in low contrast image thus making it difficult to detect objects in the intensity data.

Recent developments in versatile polymer-based technologies and hybrid integration processes offer a flexible and cost-efficient alternative for creating very complex photonic components and integrated circuits. The fast and efficient test, optimization and verification of new ideas requires an automated and reproducible simulation and design process supporting flexible layout-driven and layout-aware schematic-driven methodologies. Targeting very complex designs, even small fabrication tolerances of one building block could make a huge difference on the performance and manufacturability of the whole structure. To reduce risk of failure and to make performance predictions by virtual prototyping reliable, the simulation model of each single building block needs to be working correctly based not only on the appropriate mathematical and physical equations, but also on adequate information provided by the foundry where the final structure will be manufactured.

The PolyPhotonics Berlin consortium targets to address these design challenges and establish a new versatile integration platform combining polymer with Indium-Phosphide and thin-film filter based technologies for numerous photonics applications in the global communications and sensing market. In this paper we will present our methodologies for modelling and prototyping optical elements including hybrid coupling techniques, and compare them with exemplary characterization data obtained from measurements of fabricated devices and test structures. We will demonstrate how the seamless integration between photonic circuit and foundry knowledge enable the rapid virtual prototyping of complex photonic components and integrated circuits.

Transparent conductive oxides (TCOs) are getting increasing attention due to their unique epsilon-near-zero (ENZ) effect. The optical properties of TCOs can be dramatically changed from dielectric-like to metallic-like by controlling the carrier concentration in the telecommunication wavelengths, resulting in a near zero permittivity. The carrier concentration can be electrically manipulated when TCOs are built in a metal-oxide-semiconductor structure. With applied electrical bias, an accumulation layer forms at the oxide/TCO interface. When the accumulation layer meets ENZ condition, optical field is concentrated in the very thin accumulation layer, and thus the light-matter interaction is greatly enhanced. Such property makes TCOs wonderful materials for building active electro-optical devices. To data, several TCOs based devices configurations have been reported, such as metal-insulator-metal (MIM) waveguide based modulator, Si waveguide based plasmonic MOS modulator, PlasMOStor, and TCOs based tunable metasurfaces. Here, we design and demonstrate a TCOs based tunable subwavelength grating for surface normal modulation in the telecommunication wavelengths. The device combines the TCOs MOS structure with plasmonic grating filter. When applying voltage, the light-matter interaction in the active TCOs region is further enhanced by the surface-plasmon resonances coupled guided-mode resonances (GMRs), which enables high efficient modulation for both transmission and reflection mode with only 10nm thick TCOs layer. At peak wavelength (~1.55 μm), the simulated modulation depth achieves as high as 32% for transmission mode and 56% for reflection mode.