A New All-Optical Imaging Scheme based on QWIP technology

Proceedings of SPIE, 1995

2004

Research done by the Infrared Photonics team at Pacific Northwest National Laboratory (PNNL) is focused on developing miniaturized integrated optics and optical fiber processing methods for mid-wave infrared (MWIR) and long-wave infrared (LWIR) sensing applications by exploiting the unique optical and material properties of chalcogenide glass. PNNL has developed thin-film deposition capabilities, direct laser writing techniques, infrared photonic device demonstration, holographic optical element design and fabrication, photonic device modeling, and advanced optical metrology-all specific to chalcogenide glass. Chalcogenide infrared photonics provides a pathway to quantum cascade laser (QCL) transmitter miniaturization. The high output power, small size, and superb stability and modulation characteristics of QCLs make them amenable for integration as transmitters into ultra-sensitive, ultraselective point sampling and remote short-range chemical sensors that are particularly useful for nuclear nonproliferation missions. During FY 2006, PNNL's Infrared Photonics research team made measurable progress exploiting the extraordinary optical and material properties of chalcogenide glass to develop miniaturized integrated photonic components. The culmination of this development effort led to the first reported demonstration of a MWIR single-mode waveguide in chalcogenide glass coupled to a QCL source. Improvements were made to the chalcogenide glass thin film deposition system, including the installation of a 192 square foot, Class 10,000 clean room. It is anticipated that these improvements will lead to the routine production of low-loss, optical-quality chalcogenide thin films required for the photonic component development effort. Traditional and direct-write lithography processes were developed for chalcogenide glass that will provide the capability to fabricate etched ridge waveguide structures with index modulation provided by direct-laser written Bragg grating structures. Chalcogenide optical fiber processing methods are being developed using a Vytran large core optical fiber fusion splicer. This work will provide a unique capability to process infrared optical fibers to produce tapered QCL laser couplers, fiber splitters and combiners, and fiber-to-fiber fusion splicing. Custom asphere lens designs were developed to efficiently collect the highly divergent QCL emission and refocus into both chalcogenide optical fibers and thin-film waveguides. These lenses were sent offsite for fabrication using single-point diamond turning methods and then characterized using the suite of LWIR optical metrology tools developed at PNNL. The Infrared Photonics research is positioned to develop chalcogenide-based infrared photonic components such as waveguides, beam splitters, multiplexers, couplers, beam shapers, Bragg reflectors, long-period gratings, hybrid lenses, and optical fibers. The integration of these photonic components and optical fibers along with the QCL source will provide a compact laser transmitter, meeting the needs for a variety of infrared sensing missions.

APL Photonics, 2021

Recent work on mid-infrared (MIR) detection through the process of non-degenerate two-photon absorption (NTA) in semiconducting materials has shown that wide-field MIR imaging can be achieved with standard Si cameras. While this approach enables MIR imaging at high pixel densities, the low nonlinear absorption coefficient of Si prevents fast NTA-based imaging at lower illumination doses. Here we overcome this limitation by using InGaAs as the photosensor. Taking advantage of the much higher nonlinear absorption coefficient of this direct bandgap semiconductor, we demonstrate high-speed MIR imaging up to 500 fps with under 1 ms exposure per frame, enabling 2D or 3D mapping without preor post-processing of the image.

Infrared Physics & Technology, 2018

Polarization sensitive quantum well infrared photodetector (QWIP) focal plane arrays (FPAs) with 30 and 15 µm pitch sizes are fabricated with wire grid polarizers monolithically integrated on the pixels. High polarization contrast is achieved for pixels with 30 µm pitch size, 0.58±0.05 depending on the grating orientation, with good spatial homogeneity (standard deviation below 0.01). The polarization contrast drops to 0.30±0.05 for 15 µm pixel pitch. Influence of the grating orientation on the optical responsivity and the polarization contrast has been evaluated showing the strongest impact for +45° orientations. The fabricated FPAs exhibit temporal and spatial Noise Equivalent (NE) Degree of Linear Polarization (DoLP) of 0.03% and 0.23%, respectively, setting the resolution limit of DoLP to 0.4%. Capability of the fabricated FPAs to image polarimetric signatures in the dynamic scenes with high frame rate has been demonstrated.

Infrared Technology and Applications XXXII, 2006

Performance of quantum LWIR/MWIR photo-detectors is limited by dark-thermal current. Common approach is to reduce the thermal current by cooling the devices to cryogenic temperatures, preventing dark-thermal excitation of carriers disturbing the IR detection process. Sirica presents a new approach enabling quantum IR detection at room temperature. Instead of cooling the device, the free carriers are heated. Once their temperature is much higher than that of the device material lattice, heat transfer from the cold lattice to the hot free carriers is not possible due to thermodynamic laws. Heat transfer from hot carriers to the lattice is prevented by selecting a media where free carriers remain hot for long enough time (longer than their expected recombination lifetime). Thus, the device material lattice and hot free carriers are thermodynamically uncoupled and the device appears "cool" at room temperature. The hot carriers are then excited by IR photons to generate electron-hole pairs which are further converted to visible or NIR photons detectable by commercial visible CMOS/CCD sensors, a process known as "energy up-conversion". The energy required for up conversion is provided by an external low power light source. The new media required for effective light conversion is made of all silicon-based materials and offers the following benefits: (a) essentially nonequilibrium free carriers; (b) strong free carrier absorption of IR radiation; and (c) effective visible/near IR luminescence originating from the IR excited carriers. The theoretical model underlying the device and experimental results showing photo-induced free carrier IR absorption and IR-induced photoluminescence are presented.

Infrared Physics & Technology, 2007

This paper presents the design, fabrication and characterization of a QWIP photodetector capable of detecting simultaneously infrared radiation within near infrared (NIR), mid wavelength infrared (MWIR) and long wavelength infrared (LWIR). The NIR detection was achieved using interband transition while MWIR and LWIR were based on intersubband transition in the conduction band. The quantum well structure was designed using a computational tool developed to solve self-consistently the Schrö dinger-Poisson equation with the help of the shooting method. Intersubband absorption in the sample was measured for the MWIR and LWIR using Fourier transform spectroscopy (FTIR) and the measured peak positions were found at 5.3 lm and 8.7 lm which agree well with the theoretical values obtained 5.0 lm and 9.0 lm for the two infrared bands which indicates the accuracy of the self-consistent model. The photodetectors were fabricated using a standard photolithography process with exposed middle contacts to allow separate bias and readout of signals from the three wavelength bands. The measured photoresponse gave three peaks at 0.84 lm, 5.0 lm and 8.5 lm wavelengths with approximately 0.5 A/W, 0.03 A/W and 0.13 A/W peak responsivities for NIR, MWIR and LWIR bands, respectively. This work demonstrates the possibility of detection of widely separated wavelength bands using interband and intersubband transitions in quantum wells.

Infrared Physics & Technology, 2001

A two stack two color quantum well infrared photodetector (QWIP) for simultaneously detection of LWIR and near infrared (NIR) radiation is demonstrated. The LWIR sensor is based on a regular GaAs/AlGaAs QWIP, while the NIR sensor is based on a strained InGaAs/GaAs quantum wells structure. Optical and electrical measurements of the NIR detector and the inclusive device are presented and discussed.

Abstract: The authors propose a single heterojunction InAs/InAsSb photovoltaic detector for application in the mid-infrared region at room temperature. A closed form physics-based analytical model of the device has been developed for characterisation of the device. Numerical computations have been carried out on the basis of the model for a Pþ-InAs=n0-InAs0:88Sb0:12=nþ-InAs0:88Sb0:12 heterojunction photodetector to explore the potential of the device for possible non-telecommunication applications in the 2:5–4:5 mm wavelength region. The present model takes into account the effects of radiative recombination, Auger recombination, surface recombination and tunnelling at the hetero-interface on the detectivity of the device. The model enables the performance of the device to be optimised in terms of detectivity, responsivity and quantum efficiency. The model also provides useful design guidelines for fabrication of single heterojunction InAsSb photovoltaic detectors grown on InAs substrates. It has been observed that the doping concentration in the lightly doped active region, surface recombination and tunnelling at the hetero-interface strongly influence the performance of the InAs=InAs0:88Sb0:12 detectors.

Comptes Rendus Physique, 2003

Standard GaAs/AlGaAs QWIPs (Quantum Well Infrared Photodetector) are now well established for long wave infrared (LWIR) detection. The main advantage of this technology is the duality with the technology of commercial GaAs devices. The realization of large FPAs (up to 640 × 480) drawing on the standard III-V technological process has already been demonstrated. The second advantage widely claimed for QWIPs is the so-called band-gap engineering, allowing the custom design of the quantum structure to fulfill the requirements of specific applications such as multispectral detection. QWIP technology has been growing up over the last ten years and now reaches an undeniable level of maturity. As with all quantum detectors, the thermal current, particularly in the LWIR range, limits the operating temperature of QWIPs. It is very crucial to achieve an operating temperature as high as possible and at least above 77 K in order to reduce volume and power consumption and to improve the reliability of the detection module. This thermal current offset has three detrimental effects: noise increase, storage capacitor saturation and high sensitivity of FPAs to fluctuations in operating temperature. For LWIR FPAs, large cryocoolers are required, which means volume and power consumption unsuitable for handheld systems. The understanding of detection mechanisms has led us to design and realize high performance 'standard' QWIPs working near 77 K. Furthermore, a new in situ skimmed architecture accommodating this offset has already been demonstrated. In this paper we summarize the contribution of THALES Research & Technology to this progress. We present the current status of QWIPs in France, including the latest performances achieved with both standard and skimmed architectures. We illustrate the potential of our QWIPs through features of Thales Optronique's products for third thermal imager generation. To cite this article: E.

2010

This work describes infrared (IR) photon detector techniques based on novel semiconductor device concepts and detector designs. The aim of the investigation was to examine alternative IR detection concepts with a view to resolve some of the issues of existing IR detectors such as operating temperature and response range. Systems were fabricated to demonstrate the following IR detection concepts and determine detector parameters: (i) Near-infrared (NIR) detection based on dye-sensitization of nanostructured semiconductors, (ii) Displacement currents in semiconductor quantum dots (QDs) embedded dielectric media, (iii) Split-off band transitions in GaAs/AlGaAs heterojunction interfacial workfunction internal photoemission (HEIWIP) detectors. A far-infrared detector based on GaSb homojunction interfacial workfunction internal photoemission (HIWIP) structure is also discussed. Device concepts, detector structures, and experimental results discussed in the text are summarized below.