This PDF file contains the front matter associated with SPIE Proceedings Volume 11088, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

The sensitive detection of infrared (IR) radiation is a essential task in today’s modern world. The sensitivity of the state-of-the-art uncooled thermal infrared detectors is still several orders of magnitude above the fundamental photon noise limit. Thermal detectors based on temperature sensitive micro- and nanomechanical resonators are a promising approach to obtain improved thermal IR detectors. Here, we present an uncooled infrared detector based on a 1 mm×1 mm large nanoelectromechanical drum resonator made of 50 nm thick low-stress silicon nitride (SiN). The detector features a titanium nitride absorber with an absorptivity of ∼30% over the entire mid-IR range. The detector drum is driven at its resonance frequency by means of a phase-locked loop. Absorbed IR radiation results in an observable detuning of the drum’s oscillation frequency. We measured an Allan deviation of σ_A = 5.5 × 10⁻⁷ at room temperature at a noise bandwidth of 25 Hz. With a responsivity of R = 343 W⁻¹ this results in a sensitivity defined as noise equivalent power (NEP) of NEP = 320 pW/rtHz for an IR beam at a wavelength of 9.5 µm. For this measurement, the IR beam focus spot diameter was equal to the drum size. The drum’s responsivity improves by a factor of ten for a focal spot size smaller than ∼ 100 μm. For smaller spots the responsivity remains constant. Based on this analysis we predict a sensitivity of ∼ 30 pW/rtHz for an IR spot size smaller than 100 μm. The detector can be improved further by e.g. optimizing the tensile pre-stress to a lower value or by improving the absorptivity.

Infrared multispectral imaging with curved focal plane array (FPA) is attracting great interest with increasing demand for sensitive, low-cost and scalable devices that can distinguish coincident spectral information and achieve wide field of view, low aberrations, and simple imaging optics at the same time. However, the widespread use of such detectors is still limited by the high cost of epitaxial semiconductors like HgCdTe, InSb, and InGaAs. In contrast, the solution-processability, mechanical flexibility and wide spectral tunability of colloidal quantum dots (CQDs) have inspired various inexpensive, high-performance optoelectronic devices covering important atmospheric windows from short-wave infrared (SWIR, 1.5 – 2.5 μm) to mid-wave infrared (MWIR 3 – 5 μm). Here, a potential route leading to infrared electronic eyes with multispectral imaging capability is demonstrated by exploring HgTe CQDs photovoltaic detectors. At room temperature, the HgTe CQDs detectors demonstrate detectivity D* up to 6 × 10¹⁰ Jones in SWIR and 6.5 × 10⁸ Jones in MWIR. At cryogenic temperature, the MWIR D* becomes BLIP and increases to 1 × 10¹¹ Jones. Besides high D* , the HgTe CQDs detector shows fast response with rise time below 300 ns. By stacking CQDs with different energy gaps or coupling CQDs with tunable optical filters, dual-band and multi-band infrared detection can be achieved in wide spectral ranges. Finally, infrared images are captured with flexible HgTe CQDs detectors at varying bending curvatures, showing a practical approach to sensitive infrared electronic eyes beyond the visible range.

One of the most fascinating properties of metallic metamaterial resonators is their ability to concentrate large electric fields into sub-wavelength regions of space. This property was already highlighted in the seminal paper of J. Pendry, where the concept of metamaterials was first introduced [1]. We recently showed that this property, together with antenna effects can be very beneficial for infrared quantum detectors [2], such as quantum well infrared detectors (QWIPs) and quantum cascade detectors (QCD). For such devices thermally activated dark current imposes cryogenic cooling, which limits their applications. The combination of the absorbing region with metallic metamaterial allows a substantial increase of the light absorption area with respect to the electrical area of the device. As a consequence, the thermal dark current is reduced and the high temperature detectivity is strongly enhanced. I will present our recent implementation of this concept with QWIP detectors operating at \lambda~9µm, that were processed in a metamaterial of double-metal patch antenna arrays . In this case, we not only achieve room temperature operation, but also benefit from the intrinsic high speed of QWIP detectors to obtain heterodyne receivers in the GHz band [3]. In a second part, I will discuss THz metamaterial resonators that were specially designed for intersubband detectors [4], and that would allow further improvements of the detector performance. Reference: [1] J. B. Pendry et al. IEEE Trans. Microw. Theory Techn. 47, 2075 (1999). [2] D. Palaferri et al. New J. Phys. 18, 113016 (2016). [3] D. Palaferri et al. Nature 556, 85 (2018). [4] A. Mottaghizadeh et al. Opt. Express 25, 28718 (2017).

A hetero-barrier rectifier, Fermi-level managed barrier (FMB) diode, was developed for broadband and low-noise THzwave detection. The FMB diode has a very low barrier height of 100 meV or less, which is essential for attaining low noise-equivalent power detection under a zero-biased condition. The fabricated module integrating a high-gain preamplifier could detect signals in a wide frequency range from 160 GHz to 1.4 THz with a very low noise equivalent power (NEP) of 3 × 10^-12 W√Hz at 300 GHz in the square-law detection mode. For the heterodyne detection, an FMB diode module integrating a broadband trans-impedance amplifier was fabricated, exhibiting an intermediate frequency bandwidth of 11 GHz. Using this module, an extremely low NEP of 1.1 × 10^-18 W/Hz was achieved with a very low local oscillator power of 6 × 10^-6 W at around 300 GHz.

The deeply depleted graphene-insulator-semiconductor (D2GOS) junction has been shown to be a promising device structure for photon detection, due to its high responsivity, signal to noise ratio and ability for direct readout of individual pixels. One of the unique advantages of this architecture is its ease of exchangeability to other semiconductor absorber material, with the major caveat of realizing a functional device is to be able to deplete the semiconductor in the graphene-insulator-semiconductor (GOS) stack. This allows the opportunity to design GOS junctions to selective absorption cutoffs by choosing bulk semiconductors with the appropriate bandgaps. In this work, recent progress in demonstrating the D2GOS detectors across the mid-Infrared to gamma ray spectrum is discussed, using a variety of semiconductor absorbers (InSb, InAs, InGaAs, Si, and CdZnTe), along with the challenges associated with working with each absorber type. It is shown that the semiconductor/insulator interface defect density and graphene mobility are the two critical determinants in improving the D2GOS junction’s integration lifetime, responsivity and signal to noise ratio. Reduction of defects the semiconductor/insulator interface are demonstrated by employing surface passivation of the semiconductor through the deposition of a thin high-quality oxide, specific to each semiconductor. This is shown to dramatically reduce the dark charge generation in the device, resulting in improvements in integration lifetime, responsivity and signal to noise ratio. Finally, the device performance between 77 K and 300 K are compared, demonstrating an increase in performance at lower temperatures, due to further reduction of dark charge generation. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Graphene-based photodetectors have attracted strong interest for realizing optoelectronic devices, including photodetectors. Here we report a simple fabrication of graphene-germanium quantum dots for broadband light detection from visible to infrared region. The photodetectors show an improved responsivity and response speed. Specifically, the fabricated germanium quantum dots on graphene photodetector shows a responsivity of 1,500 A/W at room temperature and the response time is as fast as ~ 1 ms. These results address key challenges for broadband photodetectors from visible to infrared region, and are promising for the development of graphene-based optoelectronic applications.

Further leaps in astronomy demand new detector materials and devices reaching the fundamental detection limit1. Superconducting hot-electron bolometer (S-HEB) mixers form the baseline for modern astronomical receivers above 1 THz. In these, the wave beating between the Local Oscillator (LO) and the THz signal causes temperature oscillations in a metal around the transition temperature, at the Intermediate Frequency (IF), enabling read-out through changes in electrical resistance R (resistive read-out) as long as the temperature can follow the signal modulation. Despite huge efforts, the instantaneous bandwidth in practical niobium nitride (NbN)-based S-HEB mixers does not exceed 4-5GHz, limited by the electron temperature relaxation rates. The search for new materials lead to MgB2 devices,2 where 11 GHz bandwidths and a 1000K noise temperature are possible but at the expense of high LO power requirements, which is particularly detrimental for array applications. Beyond superconducting materials, charge-neutral graphene has been discussed as an ideal platform for terahertz bolometric direct detectors due to its small heat capacity and weak electron-phonon coupling. However, absence of large-area graphene homogeneously doped to Dirac point hinders any prospects for practical detectors in astronomy and other sensing applications. Furthermore, negligible temperature dependent resistance has kept this approach as not acceptable for bolometric mixers where voltage read-out is required. Here we investigate graphene that is doped to the Dirac point by assembly of molecular dopants on its surface with a high uniformity across the wafer2. With the resistance dominated by quantum localization, and thermal relaxation of carriers governed by electron diffusion, we demonstrate a graphene bolometric terahertz mixer with a gain bandwidth (presently) of 9 GHz (relaxation time 20 ps) and a mixer noise temperature of 475 K. We conclude that with the present quality of graphene, optimization of the device layout will result in a mixer noise temperature as low as 36 K and a gain bandwidth exceeding 20 GHz, with a Local Oscillator power of < 100 pW for operation temperatures <1K. Given the scalability of the material and in conjunction with emerging quantum-limited amplifiers in the GHz domain, we envisage large arrays of quantum–limited sensors in the THz domain for radio astronomy, potentially surpassing superconductor-based heterodyne detectors. References [1] M. Rowan-Robinson, “Astronomy. Probing the cold universe” Science 325, 546–7 (2009). [2] E. Novoselov and S. Cherednichenko, “Low noise terahertz MgB2 hot-electron bolometer mixers with an 11 GHz bandwidth” Appl. Phys. Lett. 110, 032601 (2017).

We present a cross-modality super-resolution microscopy method based on the generative adversarial network (GAN) framework. Using a trained convolutional neural network, our method takes a low-resolution image acquired with one microscopic imaging modality, and super-resolves it to match the resolution of the image of the same sample captured with another higher resolution microscopy modality. This cross-modality super-resolution method is purely data-driven, i.e., it does not rely on any knowledge of the image formation model, or the point-spread-function. First, we demonstrated the success of our method by super-resolving wide-field fluorescence microscopy images captured with a low-numerical aperture (NA=0.4) objective to match the resolution of images captured with a higher NA objective (NA=0.75). Next, we applied our method to confocal microscopy to super-resolve closely spaced nano-particles and Histone3 sites within HeLa cell nuclei, matching the resolution of stimulated emission depletion (STED) microscopy images of the same samples. Our method was also verified by super-resolving the diffraction-limited total internal reflection fluorescence (TIRF) microscopy images, matching the resolution of TIRF-SIM (structured illumination microscopy) images of the same samples, which revealed endocytic protein dynamics in SUM159 cells and amnioserosa tissues of a Drosophila embryo. The super-resolved object features in the network output show strong agreement with the ground truth SIM reconstructions, which were synthesized using 9 diffraction-limited TIRF images, each with structured illumination. Other than resolution enhancement, our method also offers an extended depth-of-field and improved signal-to-noise ratio (SNR) in the network inferred images compared against the corresponding ground truth images.

Imaging transient dynamics of materials and light-matter interaction at the nanoscale is of great interest to the study of condensed phase dynamics and to the field of nano-photonics. However, optical interrogation of the ultrafast dynamics of nanostructures has not been demonstrated as they are diffraction limited. Furthermore, optical methods are limited due to the low scattering of nanostructures and the strong background reflection. Accordingly, The ultrafast imaging of laser induced nanostructure melting was demonstrated via femtosecond x-ray diffraction imaging which provided relatively high temporal (~10 ps) and high spatial (~10 nm) resolution. However, this technique suffers from the inherent difficulty of using a femtosecond X-ray laser source and the damaging nature of the femtosecond X-ray laser probe required for single-shot imaging. Consequently, X-ray pump-probe imaging was never used to image the re-solidification dynamics of surface structures. On the other hand, cryo-electron microscopy achieved sub-nanometer resolution for single particles, however, it requires experiments to be performed in vacuum with highly specialized and costly instrumentation. Here, we we employ a time-resolved variant of ultramicroscopy that we recently developed to study the ultrafast dynamics of laser ablated surfaces. The technique is non-destructive and allows us to compare the transient image with the initial/final image. Accordingly, we determine the characteristic times for melting and re-solidification of nanostructures using optical wavelengths. We also study the formation and melting of Si nanostructures and image, for the first time, the process of non-thermal melting which occurs on the sub-picosecond time scale.

We present the terahertz (THz) near-field microscope, in which a flexible sapphire fiber serves as a scanning probe. High refractive index of sapphire at THz frequencies allows for a strong confinement of guided modes in a fiber core, and, thus, for a sub-wavelength resolution THz imaging. In turn, low THz-wave absorption in sapphire allows for guiding the THz waves in a fiber over tens of centimeters with rather high energy efficiency. The developed THz microscope operates in a transmission mode and uses a backward wave oscillator, as a continuous-wave THz source with the output wavelength of λ = 1200 µm, a Golay cell, as a detector of THzwave intensity, and a 300 µm-diameter flexible sapphire fiber with at input and output ends, as a scanning probe. In our THz microscope arrangement, the input end of a sapphire fiber is mounted on a motorized translation stage, which yield two- or even three-dimensional imaging of electromagnetic field formed at the shadow side of an object; while the output fiber end is rigidly fixed in front of the detector aperture. The experimental setup was applied for imaging of representative test objects, and the observed results demonstrated its advanced spatial resolution of ~ λ=4, which is beyond the Abbe diffraction limit. In our opinion, the sub-wavelength spatial resolution, along with a high energy throughout, open a wide range of the developed THz microscope applications in material science, non-destructive testing, and biophotonics.

Many applications in high energy astrophysics, particle physics or medical imaging demand covering a large detection area with fast photosensors sensible to near-UV light. The use of Silicon photomultipliers (SIPMs) for such applications is restricted due to their sensitivity to unwanted wavelengths and mainly due to their limited physical area, increasing the cost and readout complexity of a camera. We propose to solve these drawbacks by building a Light-Trap, a low-cost pixel consisting on a SiPM attached to a PMMA disk doped with a wavelength shifter (WLS). Light in the near-UV band absorbed by the WLS is optically trapped inside the disk volume until it reaches the SiPM. The pixel collects photons over a much larger area than standard SiPMs, while being sensitive only in a desired wavelength range, which can be selected to match the application requirements. We introduce the Light-Trap principles and discuss results from laboratory measurements and Monte Carlo simulations.

Photonic-electronic integration is a key technology to master data traffic growth and therefore an enabler of future network technologies. At IHP, a unique silicon-based photonic-electronic integration technology, photonic BiCMOS, has been developed. Photonic BiCMOS is a planar technology co-integrating monolithically on a single substrate high-speed RF frontend electronics with high-speed photonic devices such as broadband germanium detectors, modulators, and SOI nanowaveguide integrated optics. High RF capability of this electronic photonic integrated circuit (ePIC) technology is enabled by SiGe heterojunction bipolar transistors (HBTs). In this paper we give an overview about IHP’s work in ePIC technology development with focus on the integration of a waveguide-coupled germanium p-i-n photo diode with very high -3 dB bandwidth and advancements in the photonic BiCMOS technology.

Optical metasurface refers to a kind of nanostructured material with sub-wavelength thickness and on-demand optical properties, which are not possible for natural materials. By rationally engineering the metasurface structures, one could achieve new capabilities for the manipulation of light, e.g., ultra-thin flat lenses, waveplates and holographic plates. Yet, the optical efficiency and performance of most metasurface-based devices are yet to improve to meet the requirements for real-world applications. In this talk, I will present our research on highly efficient on-chip integratable metasurface devices for ultra-compact polarimetric detection and imaging devices. I will discuss about our approach to realize highly efficient broadband hybrid metasurfaces (based on integrated dielectric and plasmonic metasurfaces) for phase and polarization control of light in near infrared wavelength (1.2-1.7 µm). We have theoretically investigated and experimentally demonstrated circular polarization (CP) detection with CP extinction ratio (defined as the ratio between the transmission of CP light with desired handedness and that of CP light with the other handedness) of 30 and transmission efficiency over 80%. I will also discuss about another approach of realizing highly efficient plasmonic metasurfaces for phase and polarization control of light in mid-infrared wavelength (2-12 µm). Despite the high ohmic loss of plasmonic metasurfaces, I will show that by rationally designing the metasurface structure, it is possible to realize highly efficient plasmonic devices with superior performance. As a proof-of-concept demonstration, we have designed and experimentally demonstrated CP polarization filters with transmission efficiency >85% and CP extinction ratio >50 at 4 µm (bandwidth > 600 nm for CP extinction ratio> 10). The total thickness of the metasurface structure is less than 1/10 of the operational wavelength. Last but not the least, I will present our recent progress on chip-integration of metasurface devices for full-stokes polarimetric detection and imaging.

We present several integrated technologies on Silicon, from visible to mid-infrared, for particulate matter and gas detection. We present new concepts to detect in the visible particulate matter with a high sensitivity and a discrimination of both particle sizes and refractive indices. For gas detection, mid-infrared technologies developments include on one hand, microhotplate thermal emitters, as a cheap solution for gas sensing, eventually enhanced by plasmonics, and on the other hand quantum cascade lasers-based photoacoustic sensors, for high precision measurement, and for which the integration on Silicon is pushed forward for a reduction of costs.

Experimental investigations of the effects of colouring of a beam traversing a different light-scattering medium based on liquid crystals are presented. It is shown that the result of colouring of the beam at the output of the medium depends on the magnitudes of the phase delays of the singly forward scattered partial signals. Spectral investigation of the effects of colouring has been carried out using nematic liquid crystals with carbon nanotubes in comparison wihs a solution of liquid crystal in a polymer matrix which was previously investigated. The amplitude ratio of the non-scattered and the singly forward scattered interfering components significantly affects the colour intensity. It has further been established that the spectral content of the illuminating beam strongly influences the colour of the resulting radiation. Due to the injection of carbon nanotubes, a significant increase of colouring effect has been achieved, as rell as the sensitivity of the liquid crystal to the control electric field has increased.

Paper contains results of investigation of nanosheets by modificated DLS technique. The modified method of dynamic light scattering is based on an additional estimation of the stochastization and complexity of the radiation scattered at different angles for the horizontal and vertical polarization of the input beam. It is shown that both the stochastization and the complexity of the fluctuations of scattered field depend on the angle of scattering and polarization of the laser beam and allow us to qualitatively evaluate the sphericity of the particles. To quantify the chaos and complexity, the Lyapunov's maximal index and correlation exponent of fluctuations of the intensity of the field of scattered coherent optical radiation was used, respectively.

In this paper, a low-cost diaphragm based Fiber Bragg Grating (FBG) pressure sensor design for ocean applications is presented. The pressure with different thickness of copper diaphragms have been measured. A single bare FBG is mounted on top of the circular diaphragm so that maximum pressure is exerted at center of the diaphragm and it will cause the diaphragm lateral shape variation so that a strain will develop on FBG. In order to measure the pressure variation a compact design is made by using stainless steel disks and rubber “O” rings with closed air cavity setup. The pressure in static freshwater column ranging from 0 to 0.04 Mpa was gauged, using closed air cavity setup. In addition to that, another “T” shaped design, for testing has been made with solid stainless steel tube with open air cavity setup for an extended range of pressure sensing. By using an oil pressure pump and open air cavity setup, the value of pressure ranged from 0 to 0.5 Mpa with the step size of 0.01 Mpa. In both setups same thickness of copper material is used to measure the pressure and to compare the results. Furthermore, a range of experiments are carried out to test both the setups. Experimental results indicated that the pressure sensitivities in closed air cavity setup are 0.2286 and 24.95 nm/Mpa with linearity 96.29% and in open air cavity setup is 5.458 and 16.22 nm/Mpa with linearity 99.34% achieved. Open air cavity setup is more sensitive than closed air cavity method and also reported good linearity comparatively with closed air cavity method. The repeatability of the sensor has been tested 3 times and showed less hysteresis. This type of pressure sensor could be used to measure static and dynamic pressure sensing in oceanography, gas and liquid environments.