This PDF file contains the front matter associated with SPIE Proceedings Volume 9270 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

We have investigated 1.3-μm InGaAsP strained multi-quantum-well (MQW) lasers on InP substrate for direct modulation applications using the commercial laser simulator PIC3D. The physical mechanisms affecting the laser dynamic characteristics such as nonradiative recombination losses and vertical electron leakage effect are considered in our simulation. The number of wells is optimized because increasing the number of QWs can decrease the nonradiative recombination losses and increase the modal differential gain, nevertheless, the carrier distribution between wells become more non-uniform with too many QWs numbers resulting in uneven simulated recombination rate and increasing Auger recombination. The influence of barrier height is analyzed and a tradeoff has to be determined because too high barriers results in more nonuniform carrier distribution in the active regions, increasing the Auger recombination rate severely while the vertical current leakage outside the QWs will increase dramatically at lower barrier height. The 1.3-μm FP laser with the MQWs of 6 wells, 1.15 Q barriers bandgap and 8 wells, 1.1 Q barrier bandgaps is fabricated and characterized. The FP laser with MQWs structures composed of 8 compressive strain quantum wells and 9 barriers with the optimized bandgap 1.1 Q shows better properties. The threshold current is around 19 mA and the resonance frequency of 9.5 GHz and 3-dB bandwidth in excess of 13.3 GHz at 120 mA injection current. This modulation frequency is suitable for 10 Gbits/s optical data transmission.

We report systematic modelling of 1310 nm InGaAsP/InP electroabsorption modulators. The modulator is a reverse biased p-i-n diode, in which the MQW structure is composed of several InGaAsP/InGaAsP quantum wells. By a 3D finite element software PICS3D, we have comprehensively investigated the internal physical mechanism of the modulator, which includes the red shift of the absorption edge with the reverse bias and the absorption intensity, which could be derived from the normalized overlap integral between the energy levels for the electrons and the holes. The absorption spectrum on wavelength and the reverse bias voltage is analyzed, which provide us with both the extinction ratio and the transimision loss for a special operating wavelength. Key design parameters such as barrier height and quantum well width are optimized for extinction ratio, and confirmed by parallel experimental studies. What’s more, the RF performance has been investigated in detail. The junction capacitance, the series resistance and the parasitic capacitance (mostly the bonding pad) are studied systematically. A ridge structure model is analyzed for high speed performance, in which the important parameters, such as the ridge width, the cavity length, the area of the bonding pad and the thickness of polyimide (or BCB) under the bonding pad, are optimized for over 20GHz 3dB bandwidth. The cavity length is optimized by making compromise between the extinction ratio and the RF performance. In conclusion, the design parameter space of the 1310nm InGaAsP/InP EAM have been systematically explored. Our work should provide a firm basis for 1310nm InGaAsP/InP EAM device design optimization for optical datacom applications.

To realize high-efficiency organic light-emitting diodes (OLEDs), it is essential to boost out-coupling efficiency. Here we review our latest reports upon light manipulation for OLEDs by integrating a dual-side bio-inspired deterministic quasi-periodic moth’s eye nanostructure with broadband anti-reflective and quasi-omnidirectional properties. Light out-coupling efficiency of OLEDs with stacked triple emission units is over 2 times that of a conventional device, resulting in drastic increase in external quantum efficiency and current efficiency to 119.7% and 366 cd A^-1 without introducing spectral distortion and directionality. Theoretical calculations furthermore clarify that the improved device performance is primarily attributed to the effective extraction of the waveguide and surface plasmonic modes of the confined light over all the emission wavelengths and viewing-angles.

A 1.2-GHz gated infrared single-photon detector based on InGaAs/InP avalanche photodiode (APD) is designed. The APD is working in Geiger mode, gated by 1.2-GHz pseudo-sine wave signal, cooled by a 4-stage Peltier cooler with fancooling. A group of simple 9^th order Bessel LC low-pass filters are used to suppress the transient response of the APD by 60 dB. The typical detection efficiency, dark-count probability and afterpulse probability of the detector were 15.1%, 3.76×10^-6 /gate and 1.26%, respectively. The detector is based on commercially available inexpensive devices and can be manufactured easily.

Quantum dots (QDs) have numerous applications in optoelectronics due to their unique optical properties. Novel hybrid organic light-emitting diodes (OLEDs) containing QDs as an active emissive layer are being extensively developed. The performance of QD–OLED depends on the charge transport properties of the active layer and the degree of localization of electrons and holes in QDs. Therefore, the type and the density of the ligands on the QD surface are very important. We have fabricated OLEDs with a CdSe/ZnS QD active layer. These OLEDs contain hole and electron injection layers consisting of poly(9-vinyl carbazole) and ZnO nanoparticles, respectively. The energy levels of these materials ensure efficient injection of charge carriers into the QD emissive layer. In order to enhance the charge transfer to the active QD layer and thereby increase the OLED efficiency, the QD surface ligands (tri-n-octyl phosphine oxide, TOPO) were replaced with a series of aromatic amines and thiols. The substituents were expected to enhance the charge carrier mobility in the QD layer. Surprisingly, the devices based on the original TOPO-coated QDs were found to have the best performance, with a maximum brightness of 2400 Cd/m² at 10 V. We assume that this was due to a decrease in the charge localization within QDs when aromatic ligands are used. We conclude that the surface ligands considerably affect the performance of QD–OLEDs, efficient charge localization in QD cores being more important for good performance than a high charge transfer rate.

We report a flexible amorphous Lanthanide doped In-Zn-O (IZO) thin-film transistor (TFT) backplane on polyimide (PI) substrate. In order to de-bond the PI film from the glass carrier easily after the flexible AMOLED process, a special inorganic film is deposited on the glass before the PI film is coated. The TFT exhibited a field-effect mobility of 6.97 cm²V^-1 s^-1, a subthreshold swing of 0.248 V dec-1, and an I_on/I_off ratio of 5.19×107, which is sufficient to drive the OLEDs.

In this paper, we report developments of electro-optical PCBs (EO-PCB) with low-loss (<0.05dB/cm) polymer waveguides. Our results shows successful fabrication of complex waveguide structures part of hybrid EO-PCBs utilizing production scale process on standard board panels. Test patterns include 90° bends of varying radii (40mm – 2mm), waveguide crossing with varied crossing angles (90°-20°), cascaded bends with varying radii, splitters and tapered waveguides. Full ranges of geometric configurations are required to meet practical optical routing functions and layouts. Moreover, we report results obtained to realize structures to integrate optical connectors with waveguides. Experimental results are shown for MT in-plane and 90° out-of-plane optical connectors realized with coupling loss < 2dB and < 2.5 dB, respectively. These connectors are crucial to realize efficient light coupling from/to TX/RX chip-to-waveguide and within waveguide-to-fiber connections in practical optical PCBs. Furthermore, we show results for fabricating electrical interconnect structures e.g. tracing layers, vias, plated vias top/bottom and through optical layers. Process compatibility with accepted practices and production scale up for high volumes are key concerns to meet the yield target and cost efficiency. Results include waveguide characterization, transmission loss, misalignment tolerance, and effect of lamination. Critical link metrics are reported.

Basic characteristics of wavelength locked Fabry-Perot laser diode (FP-LD) are analyzed and results are presented by the simulation of a theoretical model of the FP-LD. We use fourth-order Runge-Kutta to solve the rate equation of injection locked FP-LD which has been studied by many researchers. But most of the research are either focused only on wavelength detuning or on the modes of injected beam. Hence we analyze the effect of wavelength detuning, modes of injected beam, injected power on the FP-LD. With these analysis we can conclude the required wavelength detuning, mode for injection, required injected beam power and others depending upon applications. We model FP-LD theoretically and analyze output spectrum without injection locking which contains photon number of each mode and carrier density along with gain spectrum. We added the injected beam term to the rate equation in one or more modes to obtain the spectrum of wavelength locked FP-LD. Injection locked phenomena is observed with sufficient on/off contrast ratio. Various parameters such as wavelength detuning, injected beam power, bias current, and injected modes are changed to analyze output power and spectrum. Analysis on hysteresis width is also done by changing the wavelength detuning, and injected mode number to see the effect on hysteresis width which is important to find proper wavelength detuning, injected power and mode of injected beam required for the different application such as switching, memory and others. The analysis will help to find effective parameters to meet the demand of power effective optical devices for future optical networking system.

We have proposed and demonstrated a nanosecond square-wave fiber laser working in the 1060nm band. The passively mode-locked fiber laser based on the nonlinear optical loop mirror has a peak power clamping effect which leads to the generation of nanosecond square-wave pulses. To investigate the spectrum width of the nanosecond square-wave pulse laser, we added couplers with different coupling ratio to the bidirectional ring of the figure-8 fiber laser and analyzed the laser output. The results show that a higher output coupling ratio leads to stronger peak power clamping effect, and the peak power of the square-wave pulse gets lower and the corresponding spectrum band width is narrower.

In this paper, the performance study on the tunable multiwavelength erbium-doped fiber laser is conducted, which is based on combination of Lyot birefringence fiber filter and nonlinear fiber loop mirror. The method to achieve its optimal working is introduced in detail. The parameters choice based on the best tunability is analyzed from three different perspectives: gain medium, nonlinear effect and comb filter, respectively. All the experimental results will be given through several panels of comparison experiments. The optimal performance will finally be achieved by setting appropriate parameters. The study in this paper will further improve the function of tunable fiber filter.

A stable mode-locked fiber laser employing graphene as a saturable absorber is presented. One monolayer graphene can obtain mode-locking when the cavity is around 12m, but when the cavity decreases to 6m, no stable pulses can be formed. In order to solve this problem, cascade of two monolayer graphenes is used and stable mode locked pulses with a frequency of 44.53MHz, a bandwidth of 2.4nm, a pulse width of 43.89ps and an average power of 19.10mW have been directly obtained from the laser. Our results show the atomic-layer graphene may be a promising satrurable absorber for stable pulses formation of fiber laser.

Serving as a frequency selective device, comb filter is a very important component to the multiwavelength erbium-doped fiber laser. There are all kinds of comb filters, among which the Mach–Zehnder interferometer (MZI) is the commonly used one. Since each types of Mach–Zehnder interferometers have its output features, then the study of its influence to the output characteristics of multiwavelength erbium-doped fiber laser is necessary. In this paper, the filtering properties of three basic Mach–Zehnder interferometer are discussed, including single-pass MZI, dual-pass MZI, dual-pass MZI with a optical isolator embedded into the second loop. Furthermore, the working principle and tunable operation of the tunable modified dual-pass MZI are analyzed. Above all, the influence of the four types of MZI to the output characteristics of multiwavelength erbium-doped fiber laser is experimentally studied. The results of this paper are helpful to understand the working principle of these comb filters and improve the output performance of multiwavelength erbium-doped fiber laser.

Active multi-spectral detection technology is used to acquire the information of the targets，such as spectrum, distance, intensity, and location and so on. So the active multi-spectral detection technology becomes one of the main trends of development of detection system in the future. Based on the analyzing the theory of streak tube lidar active multi-spectral detection system, we design a wavelength conversion circuit which can be applied to implement wavelength conversion in the streak tube lidar in the active multi-spectral detection. Through the O-E-O conversion mode, the wavelength of laser echo signal which contains the target information is transformed into another wavelength which represents the spectral peak response wavelength of the stripe tube photocathode. The simulation results show that when the input laser echo signal wavelength is 1.55um, and the after-converted wavelength is 0.85um , the photon conversion efficiency can reach 2.2×106 ,the signal to noise ratio can reach 19.3dB. And when the target distance or the signal bandwidth increases, the signal to noise ratio(SNR) will decrease accordingly.

The leakage light of an electro-optic modulator (EOM) induced by its finite extinction ratio (ER) may degrade the performance of Brillouin optical time domain reflectometer sensing system, especially for long distance measurement. In this letter, the configuration of a high ER probe pulse generator assisted by synchronous optical switch has been presented. A dual pulses interferometric method was also proposed to determine the dynamic ER value (DER) of the generated probe pulse. Contrast experiments have been performed to verify the effect of the proposed method in a BOTDR system and the results have shown that the performance of a long distance BOTDR sensing system can be improved observably with the proposed high ER probe pulse generator. At the end of a 48.5km sensing fiber, the maximum uncertainty of temperature measurement has been reduced from 5.2℃ to 0.8℃ with 25m spatial resolution after we improved the extinction ratio of probe pulse from 35dB to 65dB.

Compared to scanner imaging ladar, non-scanning LADAR plays a more prominent role in the militarily imaging scenarios. Non-scanning LADAR has many advantages, such as structure simplicity, high reliability, imaging efficiency and etc. However the range accuracy is low. This paper proposes a technique to use a designed delay line module in the APD array LADAR systems, which could significantly improve the range accuracy in all channels. A semiconductor laser is used as light source. A 5×5 APD array detector is adopted as the sensitive unit. A 25 channel parallel amplifier circuit is designed to process the signal with bandwidth 240 MHz . Field Programmable Gate Array (FPGA) is used to process these 25 signals paralleled, with a delay line module designed, to significant improve the ranging accuracy .The clock frequency of FPGA is 400MHz with accuracy 2.5ns. The delay lines module are used to measure part of pulse flying time, which is shorter than the clock cycle and could not be directly measured by the clock, and that is the cause of the ranging accuracy. Every delay cell is 46picoseconds , total timing accuracy is less than 500picoseconds. By using above technique, a short distance imaging experiment is presented and get the 5 ×5 pixels range image. The result is analyzed together with the factors, which influence the accuracy of ranging image, it shows the ranging accuracy of each pixel is 10cm. And some advanced methods are proposed to improve the accuracy of the system in the future.

A compact microfluidic refractive index sensor fabricated by drilling hole in the middle section of a fiber Bragg grating (FBG) is reported herein. The laser-drilled hole provides a microfluidic channel for the aqueous sample to pass through while at the same time permits coupling of the interrogating light to detect the target analyte. The reported sensor takes advantage of the fact that a small phase shift in the central region of the grating will result in a very sharp peak in the FBG stop-band. The phase shift can be related to a range of possible perturbations inside the microfluidic channel, including passage of cells, beads and a shift in the concentration of certain fluidic component. The amount of wavelength shift of the peak in the FBG stop-band represents the change in the refractive index inside the microfluidic channel. Simulation results indicate very favorable sensor signal characteristics such as large wavelength shift and sharp reflection dips. The reported microfluidic phase shift FGB sensor could be a good candidate for portable flow cytometry applications.

In this paper, a new integral imaging method is proposed for depth extraction in an optical tweezer system. A mutual coherence algorithm of stereo matching are theoretically analyzed and demonstrated feasible by virtual simulation. In our design, optical tweezer technique is combined with integral imaging in a single microscopy system by inserting a lens array into the optical train. On one hand, the optical tweezer subsystem is built based on the modulated light field from a solid laser, and the strong focused beam forms a light trap to capture tiny specimens. On the other hand, through parameters optimization, the microscopic integral imaging subsystem is composed of a microscope objective, a lens array (150x150 array with 0.192mm unit size and 9mm focal length) and a single lens reflex (SLR). Pre-magnified by the microscope objective, the specimens formed multiple images through the lens array. A single photograph of a series of multiple sub-images has recorded perspective views of the specimens. The differences between adjacent sub-images have been analyzed for depth extraction with the mutual coherence algorithm. The experimental results show that the axial resolution can reach to 1μm ^-1 and lateral resolution can reach to 2 μm ^-1.

A closed-loop resonator integrated optic gyro (RIOG) scheme based on triangular wave phase modulation is proposed. Only one integrated optic modulator (IOM) is employed. Triangular wave is applied on the IOM to modulate the passing light wave, and the feedback serrodyne wave is superimposed upon the triangular wave to compensate the resonant frequency-difference. The experimental setup is established and the related measurements are performed. The results show that the proposed scheme can realize the closed-loop RIOG employing an IOM, which has the advantage of miniature size. A bias stability of 0.39 deg/s (10 s integration time) over 1 hour is achieved. Moreover, good linearity and large dynamic range are also experimental demonstrated.

The wavelength swept laser (WSL) is a promising optical source in optical coherence tomography, optical fiber sensor, and optical beat source generation. It is demonstrated by employing a narrowband wavelength-scanning filter, such as a fast rotating polygonal-scanner-filter, a diffraction grating on a galvo-scan mirror, or a fiber Fabry-Perot tunable filter (FFP-TF). In this manuscript, we present our researches on the dynamic fiber-optic sensors. Two kinds of WSLs are used to demonstrate the dynamic measurement in the fiber-optic sensors. One is the WSL using a polygon-scanner-based wavelength filter and the other is the Fourier domain mode-locked (FDML) WSL using a FFP-TF. The dynamic fiber Bragg grating (FBG) sensor interrogation up to 2 kHz by using the WSL with a polygonscanner- based wavelength filter is reported. And by using the FDML WSL with a FFP-TF, we demonstrate a resonance FBG sensor interrogation. As another application of the WSL, we successfully measure a dynamic modulation frequency of the applied electric field using a nematic liquid crystal Fabry-Perot etalon.

Successful isolation of single layer of graphene from graphite by mechanical exfoliation method, attracted a great attention due to its unique structural, optical, mechanical and electronic properties. This makes the graphene as a promising material in many possible applications such as energy-storage, sensing, electronic, optical devices and polymer composite materials. High quality of reduced graphene oxide (rGO) material was prepared by chemical reduction method at 100°C. The structural and optical properties of the rGO sheets were characterized by FT-IR, micro Raman, powder XRD and UV-vis-NIR techniques. FT-IR reveals the absence of oxygen functional groups on rGO due to the reduction process. Powder XRD shows the broad peak at 2θ=24.3° corresponding to interlayer spacing 3.66Å which is smaller than the graphene oxide (GO). UV-vis-NIR of rGO displays the absorption peak at 271 nm indicates the reduction of GO and the restoration of C=C bonds in the rGO sheets. The cladding removed and rGO coated poly-methyl methacrylate (PMMA) optical fiber is used for methanol and ethanol vapors detection in the concentration ranging from 0 to 500 ppm at room temperature. The spectral characteristics along with output intensity modulation of cladding removed and rGO coated fiber optic sensor reveal the potential of methanol and ethanol vapor sensing properties.

This paper designs and implies a high precision FBG demodulation system which based on F-P etalon. In order to reduce the influence of the temperature drift effect, the peristaltic effect, and the nonlinear effect of F-P filter in traditional tunable filter method, F-P etalon is added as dynamical calibration and wavelength reference. Meanwhile segmentation demodulation which uses ASE spectral characteristics is applied to achieve high accuracy of the center wavelength of FBG. The experiment shows that the stability, resolution are 0.65pm, 0.23pm, respectively. Key words: fiber optics; fiber Bragg grating sensor system; tunable Fabry-Perot filter; F-P etalon; spectrum segmentation demodulation

Electrowetting is a phenomenon that can control the surface tension of liquid when a voltage is applied. This paper introduces the fabrication method of liquid lens array by the electrowetting phenomenon. The fabricated 23 by 23 lens array has 1mm diameter size with 1.6 mm interval distance between adjacent lenses. The diopter of each lens was - 24~27 operated at 0V to 50V. The lens array chamber fabricated by Deep Reactive-Ion Etching (DRIE) is deposited with IZO and parylene C and tantalum oxide. To prevent water penetration and achieve high dielectric constant, parylene C and tantalum oxide (ε = 23 ~ 25) are used respectively. Hydrophobic surface which enables the range of contact angle from 60 to 160 degree is coated to maximize the effect of electrowetting causing wide band of dioptric power. Liquid is injected into each lens chamber by two different ways. First way was self water-oil dosing that uses cosolvent and diffusion effect, while the second way was micro-syringe by the hydrophobic surface properties. To complete the whole process of the lens array fabrication, underwater sealing was performed using UV adhesive that does not dissolve in water. The transient time for changing from concave to convex lens was measured <33ms (at frequency of 1kHz AC voltage.). The liquid lens array was tested unprecedentedly for integral imaging to achieve more advanced depth information of 3D image.

In this paper, we proposed and demonstrated a simple ChG waveguide structure, guided by low refractive-index strips on the surfaces of planar ChG films. Theoretical analysis shows that it supports quasi-TE mode transmission in 1.5μm band with high nonlinearity. Samples of this surface guiding ChG waveguides are fabricated. Its transmission properties are measured by the cut-off method, showing a waveguide attenuation of 0.67dB/mm and a coupling loss with optical fibers of ~8dB/facet. It provides a simple way to realize high quality ChG waveguides, which has great potential in developing nonlinear photonic devices.

In this paper we review our work on birefringence compensated arrayed waveguide grating. We elaborate on a birefringence compensation technique based on angled star couplers in arrayed waveguide grating (AWG) and discuss several demonstrations both in low-index-contrast and high-index-contrast material systems. A 16-channel AWG with 100GHz channel spacing for DWDM application is designed and fabricated in silica-based low-index-contrast waveguide. The experimental results confirm that the polarization-dependent wavelength shift (PDλ) can be tuned by varying the incident/diffraction angle at the star couplers and a birefringence-free property can be achieved without additional fabrication process as compared to conventional AWG. A further validation of this technique is demonstrated in high-index-contrast silicon-on-insulator waveguide, in combination with different diffraction orders for TE and TM polarizations. A birefringence compensated silicon nanowire AWG for CWDM optical interconnects is designed and fabricated. The theoretical and experimental results show that the PDλ can be reduced from 380–420nm to 0.5–3.5 nm, below 25% of the 3 dB bandwidth of the channel response in the wavelength range of 1500 to 1600nm.

In this paper, the 1×5 optical splitters (OSs) based on 2D rod-type silicon photonic crystal embed cascaded self-collimation (SC) ring resonators (CSCRR) was proposed. The 1×5 OSs consist of eight beam splitters, which are formed by varying the radii of the rod. With self-collimation effect, we can manipulate the light’s propagation in the OSs. Here we consider TM modes. Utilizing multiple-beam interference theory, the theoretical transmission spectra at different outputs were analysed. These transmission spectra can help us to set the radii of eight slitters properly, for we can control the light coming out from five ports with the light-intensity ratio we need. Meanwhile these outputs’ transmission spectra were investigated by the finite-difference time-domain (FDTD) method. The simulative results have an agreement with the theoretical prediction. The 1×5 OSs will have practical applications in photonic integrated circuits.

A series-coupled double-ring resonator with asymmetric radii is analyzed to achieve a filter response with a large free spectral range (FSR), a narrow passband of tens of MHz and a small shape factor simultaneously for use in microwave photonic channelizer. By introducing difference to the two radii, based on the vernier effect, the FSR of the resonator filter can be extended while maintaining the narrow passband and the small shape factor. A filter response with a FSR of 29.444 GHz, a 3-dB bandwidth of 96 MHz and a shape factor of 3.17 is realized by numerical analysis.

With the increasing demand for information, integrated silicon photonics technology has been highly valued. Among them, silicon on insulator (SOI) has advantages of low cost, process maturity, and IC technology compatible, making it to be one of the most competitive integrated optoelectronic platforms. However, due to its highly polarization-dependent performance, polarization-selective devices are essential on SOI platform. In this paper, we analyze the critical guiding condition of SOI waveguide as well as the hybrid plasmonic waveguide (HPW). Based on the different critical guiding condition for both polarizations, we propose several polarization-selective devices on SOI platform, including polarizer, polarization beam splitter (PBS) and polarization rotator. In this paper, an ultracompact and broadband TE-pass polarizer based on HPW is proposed. In addition, an asymmetrical coupling based polarization beam splitter is designed. Simulation results show that the designed devices have excellent optical properties, and the sizes of the devices achieve a great breakthrough.

Visible light communication (VLC) has been regarded as a promising solution in short-range intelligent communication system. Nowadays, the research is focused on integrating the multi-input multi-output (MIMO) technique in the VLC system, to achieve a larger transmission capacity and stronger transmission reliability. However, one important issue should be addressed due to the use of MIMO technology: the multipath inter-symbol interference. The multipath intersymbol interference comes from the reflection of the signal in the room and channel crosstalk between different channels. In this paper, we propose a novel optical system used in the MIMO VLC system to reduce multipath interference dramatically. Signals from different LEDs can be separated by using parabolic lens plated with reflecting film. This structure can reduce the reflection effect effectively as well. We present the simulation results to observe the distribution of optical power on the imaging plane for various receiving positions and low correlation between all channels. We can find that the optical power density becomes stronger than non-imaging system and the interference is sharply decreased, thus the SNR and BER are also optimized. Analysis about the optical system is given in this paper.

The fine manipulations of cylindrical vector beams (CVBs) based on metallic microstructures, such as sub-wavelength focusing, have entered many interdisciplinary areas, and the important applications have been found in many fields including optical micromanipulation, super-resolution imaging, micro-machining and so on. But so far, the sub-wavelength focusing of azimuthally polarized beams is encountered, since the manipulation mechanisms rely heavily on the excitation of surface plasmon polaritons, which brings the polarization limitation. We theoretically investigated the focusing behavior of CVBs in 1D metallic photonic crystals (MPCs). The simulation results show that a 1D MPC plano-concave lens can focus cylindrical vector beams into scale of sub-wavelength. The negative refraction at the interface between the air and the 1D MPC is analyzed at the frequencies corresponding to the second photonic band, which makes the 1D MPC has the ability to focus higher Fourier components of light beams. The cylindrical plano-concave structure is constructed to focus the radially and azimuthally polarized beams simultaneously. The behavior is demonstrated by Finite Element Method (FEM). The shape of focusing field can be tailored, by changing the polarization ratio of the incident beams. In addition, the effective sub-wavelength focusing phenomenon can also be realized in variety of wave ranges, by choosing the proper materials and adjusting the parameters. We believe that it’s the first time to realize the simultaneous sub-wavelength focusing of radially and azimuthally polarized beams, the application of which is quite promising in broad prospects.

In traditional dimming control system using pulse width modulation (PWM) combined with M-QAM OFDM scheme, OFDM signal is only transmitted during “on” period. To guarantee the communication quality, reduction of duty cycle will cause increased symbol rate or added LED power. This means system BER performance degradation and power consumption. In order to solve the defects of the traditional dimming scheme, we propose a new dimming control scheme in indoor visible light communication, which combines OFDM signal and multi-pulse position modulation (MPPM) light pulse well with each other. By means of dividing traditional PWM pulses into MPPM pulses with the same duty cycle, the pattern effect of MPPM pulses is utilized, which makes excess signal transmission possible. Simulation results show that when reducing the brightness of LED the achievable symbol rate using dimming control patterns is not higher than the traditional PWM scheme and the LED power is also reduced, which satisfies both system reliability and energy effectiveness under constant high data rate and BER less than 10^-3.

Internet Of Things (IOT) drives a significant increase in the extent and type of sensing technology and equipment. Sensors, instrumentation, control electronics, data logging and transmission units comprising such sensing systems will all require to be powered. Conventionally, electrical powering is supplied by batteries or/and electric power cables. The power supply by batteries usually has a limited lifetime, while the electric power cables are susceptible to electromagnetic interference. In fact, the electromagnetic interference is the key issue limiting the power supply in the strong electromagnetic radiation area and other extreme environments. The novel alternative method of power supply is power over fiber (PoF) technique. As fibers are used as power supply lines instead, the delivery of the power is inherently immune to electromagnetic radiation, and avoids cumbersome shielding of power lines. Such a safer power supply mode would be a promising candidate for applications in IOT. In this work, we built up optically powered active sensing system, supplying uninterrupted power for the remote active sensors and communication modules. Also, we proposed a novel maximum power point tracking technique for photovoltaic power convertors. In our system, the actual output efficiency greater than 40% within 1W laser power. After 1km fiber transmission and opto-electric power conversion, a stable electric power of 210mW was obtained, which is sufficient for operating an active sensing system.

For a space downlink laser communication system with an EDFA as a power amplifier, the performance of its BER deteriorates because the EDFA’s characteristics are badly impacted by space radiation. As is investigated in this paper, small divergence-angle, lower than 30μrad, assures that the BER is lower than10^-20 although the increase of radiation dose from 0Gy to 250Gy leads to 20 orders of magnitude increase of the BER. Such perfection results from our selection of optimal parameters. In the case of zenith angle, the BER increases smoothly when the zenith angle is lower than 10 degrees. After the point of 10 degrees, however, the BER starts its linearly fast increase. Increasing the radiation dose makes the BER increase and such evolution trend more smooth. Moreover, the increase of receiving diameter leads to linear reduce of BER. It is interesting to note that the evolution becomes nonlinear in region of low receiving diameter when we change the divergence-angle to a higher value 60μrad. Besides, suffering radiation makes the non-linearity mentioned above more apparent. Another try to change the zenith angle to higher value 45° does not show obvious nonlinear effect but it worsens the performance of BER quite a lot. Commonly, the impact of radiation will reach its saturation when the dose of radiation continues to increase. The work will benefit the design of practical space laser communication system with EDFAs.

In this presentation, we propose and experimentally demonstrate a novel optical generation of microwave and millimeter wave signals by using asymmetric fiber Bragg grating Fabry-Perot cavity fiber laser, dual-wavelength emission can be achieved with wavelength separation of 0.68nm corresponding to the millimeter wave signal at 85GHz. By appropriately adjusting the operation temperature of intracavity fiber Bragg grating, the frequency of millimeter wave signal generated can be tunable. Our experimental results demonstrate the new concept of optical generation of microwave and millimeter wave signals by using asymmetric fiber Bragg grating Fabry-Perot cavity dual-wavelength fiber laser and the technical feasibility.

Optical properties of (1-x)Pb(Zn_1/3Nb_2/3)O₃-xPbTiO₃ (PZN-xPT, x=5%, 9% and 12%) single crystals have been comprehensively investigated. The PZN-xPT single crystals used in this study were grown using a high temperature flux method. Refractive indices (n_ij) were measured by the Brewster’s angles (θB=tan^-1n) at different wavelengths. Dispersion equations of refractive indices were obtained. After poled along [001] direction, the transmittance of PZN–12%PT single crystal is more than 65% from 0.5 to 5.8 μm, which is much higher than that of PZN–5%PT and PZN-9%PT single crystals. PZN–12%PT has a tetragonal phase, its spontaneous polarization PS is along [001] direction. After poling, it could form a single domain structure. Orientation and temperature dependences of the electro-optic coefficient were investigated at He-Ne laser by the Senarmont compensator method. Large effective electro-optic coefficient (γc = 430 pm/V) was observed in [001]-poled PZN-9%PT crystal. More importantly, γc of tetragonal PZN-12%PT is about 130 pm/V, which is almost unchanged in a temperature range -20~80 °C. The γc of PZN-xPT single crystals are much higher than that of widely used electro-optic crystal LiNbO₃ (γc = 20 pm/V). These excellent optical properties make the PZNxPT single crystals promising candidates for electro-optic modulation applications.

Thanks to the development in epitaxial growth, chip fabrication and packaging of LEDs, emission spectral of the device is capable of covering the visible spectrum. Therefore, Light-emitting diode (LED) is currently undergoing a growing interest in many applications, such as lighting. Besides lighting, LEDs offer a wide range of potential applications including display. In contrast with LCD, LEDs display has better contrast ratio, higher response rate etc which makes LEDs along with other self-illumination technologies an ideal candidate in making display panel. Due to the popularization of HD and Ultra HD standard, display panel with better image quality is needed which means the number of pixels of the panel needs to be increased while the size of each pixel needs to be minimized. In this paper, we describe the design and fabrication of a colour tuneable and addressable LED micro display based on a 16×16 and 32×32 LED matrixes with typical pixel size of 0.7 and 0.5mm respectively.

Based on the studies of the GaAs photocathode, the surface model of the InGaAs photocathode is investigated and the energy distributions of electrons reaching the band bending region, reaching the surface and emitting into vacuum are calculated. We use the quantum efficiency formula to fit the experimental curves, and obtain the performance parameters of the photocathode and the surface barrier parameters. The results show that the electron escape probability is seriously influenced by energy distribution and plays an important role in the research of high quantum efficiency as well. After the theoretical calculation, the energy range of electrons crossing the BBR broaden, the peak of the electron energy distribution shifts forward to low energy, the number of low energy electrons increases obviously; The surface barriers of the InGaAs photocathode is similar to that of the GaAs photocathode. The height of barrier II not only decreases the number of electrons, but also makes the width of electron energy distribution narrow. The prepared transmission-mode InGaAs photocathode contains 20% InAs and 80% GaAs. This combination of InGaAs photocathodes is widely used in the weak light detection field, such as night vision technology, forest fire prevention and harsh climate monitoring.

Measurement for spin velocity is an important method for identification of space debris from functioning crafts as the obtained light curve shows periodic signatures, which helps to identify the debris from functioning space craft. In this paper, space debris of different spin velocities, different altitudes, and different surface materials (Al2O3, TiO2) are both theoretically analyzed and simulated with a ray tracing method by Tracepro. In the ray tracing simulation, light is presented by a visible way as light rays, and only some basic laws of geometrical optics are needed. Simulation results show light curves have periodic signatures which can be used for spin velocity measurement. And spin velocities obtained from active illumination and passive illumination are different, which may have some reference value in the practical engineering.

In this paper, a ring cavity passively mode-locked fiber laser using a semiconductor saturable absorber mirror as saturable absorber and a fiber Bragg grating as dispersion compensator, is proposed and experimentally demonstrated, its output performance is discussed. Stable mode-locking spectrum with 3dB bandwidth of 3.2nm, center wavelength of 1555.8nm and average output power of 0.32mW is observed at the pump power of 110mW. The pulse repetition rate is 25 MHz, as determined by the cavity length of ~8m in case of the output sech2 transform-limited pulse, the output pulses duration of 0.79ps and single pulse energy of 12.64pJ are obtained.

There exist limitations of conventional quantum efficiency models for both reflection-mode (r-mode) and transmission-mode (t-mode) exponential-doped GaAs photocathodes in some cases. The revised quantum efficiency models of the r-mode and t-mode photocathodes are solved from the one-dimensional continuity equations, wherein the built-in electric field in the GaAs layer and the electrons generated from the AlGaAs layer are considered. According to the revised models, the effects of some relational performance parameters are analyzed, such as the thicknesses of GaAs layer and AlGaAs layer, and the interface recombination velocity on the quantum efficiency for t-mode and r-mode photocathodes in combination with the conventional models. The results show that the main contribution of photoelectrons generated from AlGaAs layer to quantum efficiency in the shortwave (i.e. high incident photon energy) region, depends on the factors including cathode thickness and interface recombination velocity.

The finite-difference time-domain (FDTD) method, which solves time-dependent Maxwell’s curl equations numerically, has been proved to be a highly efficient technique for numerous applications in electromagnetic. Despite the simplicity of the FDTD method, this technique suffers from serious limitations in case that substantial computer resource is required to solve electromagnetic problems with medium or large computational dimensions, for example in high-index optical devices. In our work, an efficient wavelet-based FDTD model has been implemented and extended in a parallel computation environment, to analyze high-index optical devices. This model is based on Daubechies compactly supported orthogonal wavelets and Deslauriers-Dubuc interpolating functions as biorthogonal wavelet bases, and thus is a very efficient algorithm to solve differential equations numerically. This wavelet-based FDTD model is a high-spatial-order FDTD indeed. Because of the highly linear numerical dispersion properties of this high-spatial-order FDTD, the required discretization can be coarser than that required in the standard FDTD method. In our work, this wavelet-based FDTD model achieved significant reduction in the number of cells, i.e. used memory. Also, as different segments of the optical device can be computed simultaneously, there was a significant gain in computation time. Substantially, we achieved speed-up factors higher than 30 in comparisons to using a single processor. Furthermore, the efficiency of the parallelized computation such as the influence of the discretization and the load sharing between different processors were analyzed. As a conclusion, this parallel-computing model is promising to analyze more complicated optical devices with large dimensions.

The integration of optical devices and electronic integrated circuits (IC) is a main issue for optoelectronic convergence. In this work, a CMOS post-backend process flow is proposed to potentially achieve a 3-D monolithic optoelectronic integrated chip. The proposed integrated chip is composed of an IC die as electronic layer and a waveguide device layer as photonic layer above electronic layer. The photonic layer is fabricated by CMOS post-backend process with a temperature blow 450 ºC, which would do no harm to the performance of the CMOS ICs. We also fabricated Si3N4 mircoring add-drop filters on a bulk Si wafer. The cross-section of the waveguide is 400 nm × 1 μm, and the radius of microring is 30μm. Measured results match well with numerical simulations.

While monolithic integration especially based on InP appears to be quite an expensive solution for optical devices, hybrid integration solutions using cheaper material platforms are considered powerful competitors because of the high freedom of design, yield optimization and relative cost-efficiency. Among them, the polymer planar-lightwave circuit (PLC) technology is regarded attractive as polymer offers the potential of fairly simple and low-cost fabrication, and of low-cost packaging. In our work, polymer PLC was fabricated by using the standard reactive ion etching (RIE) technique, while other active and passive devices can be integrated on the polymer PLC platform. Exemplary polymer waveguide devices was a 13-channel arrayed waveguide grating (AWG) chip, where the central channel cross-talk was below -30dB and the polarization dependent frequency shift was mitigated by inserting a half wave plate. An optical 900 hybrid was also realized with one 2×4 multi-mode interferometer (MMI). The excess insertion losses are below 4dB for the C-band, while the transmission imbalance is below 1.2dB. When such an optical hybrid was integrated vertically with mesa-type photodiodes, the responsivity of the individual PD was around 0.06 A/W, while the 3 dB bandwidth reaches 24 ~ 27 GHz, which is sufficient for 100Gbit/s receivers. Another example of the hybrid integration was to couple the polymer waveguides to fiber by applying fiber grooves, whose typical loss value was 0.2 dB per-facet over a broad spectral range from 1200-1600 nm.

Benefit from the attractive features such as compact volume, thin and lightweight, the imaging systems based on microlens array have become an active area of research. However, current imaging systems based on microlens array have insufficient imaging quality so that it cannot meet the practical requirements in most applications. As a result, the post-digital image processing for image reconstruction from the low-resolution sub-image sequence becomes particularly important. In general, the post-digital image processing mainly includes two parts: the accurate estimation of the motion parameters between the sub-image sequence and the reconstruction of high resolution image. In this paper, given the fact that the preprocessing of the unit image can make the edge of the reconstructed high-resolution image clearer, the low-resolution images are preprocessed before the post-digital image processing. Then, after the processing of the pixel rearrange method, a high-resolution image is obtained. From the result, we find that the edge of the reconstructed high-resolution image is clearer than that without preprocessing.

Optical micro-cavity structures, which can confine light in a small mode volume with high quality factors, have become an important platform not only for optoelectronic applications with densely integrated optical components, but also for fundamental studies such as cavity quantum electrodynamics and nonlinear optical processes. Micro-cavity lasers with directional emission feature are becoming a promising resonator for the compact laser application. In this paper, we presented the limason-shaped cavity laser with large device size, and fabricated this type of micro-cavity laser with quantum cascade laser material. The micro-cavity laser with large device size was fabricated by using InP based InGaAs/InAlAs quantum cascade lasers material at about 10um emitting wavelength, and the micro-cavity lasers with the large device size were manufactured and characterized with light output power, threshold current, and the far-field pattern.

Carbon nanotube (CNT) networks are identified as potential substitute and surpass the conventional indium doped tin oxide (ITO) in transparent conducting electrodes, thin-film transistors, solar cells, and chemical sensors. Among them, CNT based gas sensors gained more interest because of its need in environmental monitoring, industrial control, and detection of gases in warfare or for averting security threats. The unique properties of CNT networks such as high surface area, low density, high thermal conductivity and chemical sensitivity making them as a potential candidate for gas sensing applications. Commercial unsorted single walled carbon nanotubes (SWCNT) were purified by thermal oxidation and acid treatment processes and dispersed in organic solvent N-methyl pyrolidone using sonication process in the absence of polymer or surfactant. Optically transparent SWCNT networks are realized on glass substrate by coating the dispersed SWCNT with the help of dynamic spray coating process at 200ºC. The SWCNT random network was characterized by scanning electron microscopy and UV-vis-NIR spectroscopy. Gas sensing property of transparent film towards ammonia vapor is studied at room temperature by measuring the resistance change with respect to the concentration in the range 0-1000 ppm. The sensor response is increased logarithmically in the concentration range 0 to 1000 ppm with the detection limit 0.007 ppm. The random networks are able to detect ammonia vapor selectively because of the high electron donating nature of ammonia molecule to the SWCNT. The sensor is reversible and selective to ammonia vapor with response time 70 seconds and recovery time 423 seconds for 62.5 ppm with 90% optical transparency at 550 nm.

Chalcogenide microstructured fibers (MOFs) have great advantages for supercontinuum (SC) generation in mid-infrared (MIR) region, because they possess the properties of high nonlinearity and wide transmission window, simultaneously. The nonlinear parameters of chalcogenide MOFs can be higher by several tens or hundreds than those of silica, fluoride and tellurite fibers depending on the material components and fiber structures. Chalcogenide MOF can be transparent from visible up to the infrared region of 12 or 15 μm depending on the compositions. In this paper, we demonstrate the SC generation in two kinds of suspended-core chalcogenide MOFs with different material components and fiber structures. One is an As₂S₃ MOF with three-hole structure (Fiber I). The other is an As₂S₅ MOF with four-hole structure (Fiber II). For Fiber I, the SC range of 3020 nm (from 1510 to 4530 nm) were obtained in a 2.4 cm fiber, when pumped by the wavelength at 2500 nm. The SC extends to the wavelengths longer than 4 μm. For Fiber II, the SC range of 4280 nm (from 1370 to 5650 nm) is generated in a 4.8 cm fiber when pumped by the wavelength at 2300 nm, which covers more than two octaves. Compared to the SC generated in Fiber I, the SC spectral range in Fiber II has been increased by more than 1200 nm due to the better transmission property of the As₂S₅ glass; the SC extends to the wavelengths longer than 5 μm.

The mid-IR supercontinuum (SC) light source is in demand for many chemical, biological, medical, and astronomical applications. It is of great significance to develop a mid-IR SC light source whose spectrum is wide and flat. We obtained ultra-broadband mid-IR SC by using a piece of fluoride glass through filamentation. Though the SC generation by filamentation needs a powerful laser chain to be the pump source, it has some advantages in comparison with that based on fiber. First, the optical path length in the glass can be very short due to the adopted high pump power. The negative influence of accumulated loss can be reduced greatly, so the transparent range of glass is much larger than fiber. Secondly, it is convenient in light-coupling, and the coupling efficiency can be high. In comparison with it, the coupling of the small core (usually the core is small to ensure a high nonlinearity) mid-IR glass fiber is troublesome. Thirdly, the glass piece is cost-effective, and can be fabricated easily. We obtained a SC spectrum covering 0.2-8.0 μm by using a 32mm-thick fluoride glass sample. The 3 dB bandwidth covers 1.15-4.76 μm. The 20 dB bandwidth spans from 0.39 to 7.4 μm. The glass thickness, optical path, and pump conditions are optimized to enable the SC to be as wide as possible. This work shows that the SC generation through filamentation in bulk glass can be an effective way to obtain an ultra-broadband mid-IR light source, which will find various applications in mid-IR regions.

Now more and more digital optical rotary encoders with a serial output code are widely adopted. In this regard there is a need of an assessment of precision characteristics of such converters. As means of calibration and checking of such sensors the dynamic laser goniometer with the ring laser as a reference angular sensor is used. In the report the technique of an estimation of precision characteristics of angular optical encoders with a serial output code is considered.

A mode-locked Er-doped fiber laser using graphene-covered-microfiber (GCMF) as saturable absorber is demonstrated. The GCMF has excellent interaction between the propagating light and graphene film via its large evanescent field. By improving the side-pump power and adjusting the PC, we successfully achieved pulse trains with a repetition rate of 1.7 MHz, which matches well with the length of the cavity. The pulse width was 380 fs. By tuning pump power and polarization states in the laser cavity, stable Q-switching, Q-switched mode-locking and continuous-wave mode-locking can be achieved in our experiments.

In order to combine LED lighting with optical communication system well, an effective coding design plugged in a time interval which is selected through theoretical calculation is proposed in the paper. In this way a stable environment for illumination will be provided and the brightness will be improved. Results of the experiment verify that the coding design is effective.

In this study, we quantitatively investigate the influence of phosphor to the thermal properties of white LEDs. We find that although the junction temperature of white LEDs is higher than corresponding blue LEDs, due to the high thermal conductivity of the phosphor, it will help to improve the thermal dissipation and lower the thermal resistance of white LEDs. Based on this, a heat transfer model has been proposed, which has also been confirmed by simulation analysis. While for white LEDs with remote phosphors, although the lower junction temperature can help to improve performance and reliability, the thermal resistance has not been improved. The heat generated by phosphors is isolated by the silicone and this would increase the phosphor temperature and lead to a different degradation mechanism after a long time stress.