QWIP Focal Plane Arrays Research Articles

Grating-free high-x InP/InxGa1-xAs mid-wavelength infrared QWIP focal plane array

Grating-free high-x InP/InxGa1-xAs mid-wavelength infrared QWIP focal plane array

Compact on-chip THz circular polarization detectors with high discrimination based on chiral plasmonic antennas

THz circular polarization detection is an important technology in many applications of THz waves. With the ongoing miniaturization of optoelectronic systems, there is an increasing demand for compact on-chip THz circular polarization detectors. Here, we propose what we belive to be a novel device of this kind based on the composite structure of quantum well (QW) infrared detection material sandwiched by a chiral plasmonic antenna array and a metal plane. Due to the circular polarization dependent light coupling discrimination provided by the cavity enhanced chiral antenna and the second polarization selection of the QWs, a circular polarization extinction ratio as high as 25 is achieved, surpassing all reported on-chip THz circular polarization detectors. Due to the field enhancement at the QWs, the absorption for the principle circular polarization is 15 times higher than a standard reference. The absorption peak can be tuned over the range from 6.41 to 6.56 THz, while considerable absorption enhancement and high circular polarization discrimination are preserved even under non-normal incidence. Our proposed device's structure is compatible with the QWIP focal plane array and has far-reaching application prospects opens a new avenue to the development of high-performance compact on-chip THz circular polarization detectors.

Effect of the grating shape on the response spectrum of quantum well infrared detector focal plane array

For the most commonly used GaAs/ AlGaAs quantum well infrared detector (QWIP), normal incident absorption is not possible due to the transition rules. QWIP requires gratings to achieve high absorption quantum efficiency and the shape of the grating affects the peak response wavelength. In order to reduce the impact of other processes on the spectrum, we manufactured 320 × 256 n-type QWIP focal plane array (FPA) was fabricated based on GaAs/AlxGa1−xAs. 160 × 256 were concave gratings and 160 × 256 were convex gratings. Three-dimensional(3D) model was first exploited and the response spectrum of two gratings were calculated by the finite difference time domain (FDTD). The test result indicated that concave grating response wavelength was 11.2μm, convex grating response wavelength was 10.3μm. The operable pixel factor of the QWIP FPA was 99.494%, the average responsivity was 17.95 mV/K. In addition, we obtained infrared images based on QWIP FPA.

Modulation transfer function of QWIP and superlattice focal plane arrays

Modulation transfer function (MTF) is the ability of an imaging system to faithfully image a given object. The MTF of an imaging system quantifies the ability of the system to resolve or transfer spatial frequencies. In this paper we will discuss the detail MTF measurements of a 1024×1024pixel multi-band quantum well infrared photodetector and 320×256pixel long-wavelength InAs/GaSb superlattice infrared focal plane arrays.

Material considerations for third generation infrared photon detectors

In the paper, issues associated with the development and exploitation of materials used in fabrication of third generation infrared photon detectors are discussed. In this class of detectors two main competitors, HgCdTe photodiodes and quantum well photoconductors are considered. The performance figures of merit of state-of-the-art HgCdTe and QWIP focal plane arrays (FPAs) are similar because the main limitations come from the readout circuits. The metallurgical issues of the epitaxial layers such as uniformity and number of defected elements are the serious problems in the case of long wavelength infrared (LWIR) and very LWIR (VLWIR) HgCdTe FPAs. It is predicted that superlattice based InAs/GaInSb system grown on GaSb substrate seems to be an alternative to HgCdTe with good spatial uniformity and an ability to span cutoff wavelength from 3 to 25μm. In this context the material properties of type II superlattices are considered more in detail.

Dual-band QWIP focal plane array for the second and third atmospheric windows

We report on the development and status of a dual-band QWIP FPA with 384 × 288 pixels and 40 μm pitch for the 3–5 μm (mid-wavelength infrared, MWIR) and 8–12 μm (long-wavelength infrared, LWIR) spectral bands. The array is based on a photovoltaic “low-noise” QWIP for the LWIR and a photoconductive QWIP for the MWIR and allows for simultaneous integration of both bands on each pixel. Array histograms indicate a noise-equivalent temperature difference as low as 17 mK for the MWIR band and 43 mK for the LWIR band at an integration time of 7.6 ms. In addition, we have investigated test devices with different gratings, geometries, and sizes and discuss some tradeoffs for dual-band diffraction gratings.

Effect of finite pixel size on optical coupling in QWIPs

We study the optical coupling in quantum well photodetectors, focusing on finite size effects. We introduced a finite-element model of the detector and we show experimentally that the optical coupling efficiency is strongly dependent on the pixel size and that in very small detectors diffraction dominates the grating coupling. A 640 × 512 QWIP focal plane array was characterized to show that the optical response of thinned samples may depend on the substrate thickness noticeably. These results are in much closer agreement with predictions obtained with our model than using standard techniques.

QWIP – not only for night vision: development and production of QWIP focal plane arrays at ACREO

QWIP – not only for night vision: development and production of QWIP focal plane arrays at ACREO

Standardized high performance readout integrated circuits enable rapid development of QWIP imaging systems

This paper describes standardized high performance 320 by 256 (ISC9705 or ‘Standard 320’) and 640 by 512 (ISC9803 or ‘Standard 640’) readout integrated circuits (ROICs) for detectors such as InSb, InGaAs, and QWIP, including presentation of focal plane array (FPA) test results for QWIP FPAs fabricated on the ISC9705 and ISC9803 ROICs. The availability of detector interface layout databases, complete test results for each die, and off-the-shelf imaging electronics enable rapid development of imaging systems using QWIP detector arrays. The ROICs are intended to support a wide range of systems through flexibility and advanced modes of operation, and include features such as high-detector bias, programmable gain and signal ‘skimming’ to improve the performance of QWIP FPAs fabricated with these devices. The ROICs also support such advanced features as dynamic image transposition, dynamic windowing, multiple high-speed output configurations, and flexible snapshot integration. These arrays are part of the Indigo Systems family of standard ROICs that share a common architecture and electrical interface.