We report a longwave infrared quantum dot infrared photodetector working at room temperature (RT) (298K). A
photoresponsivity and photodetectivity of 0.02A/W and 9.0x106 cmHz1/2/W was achieved at 298K with a low bias
voltage of -0.1V. The RT QDIP avoids bulk and heavy cryogenic cooling systems and thus enables the development
of ultra-compact IR sensing and imaging systems.
We report a voltage-tunable multispectral quantum dot infrared photodetector with
integrated carbon-nanotube based flexible electronics. Such integrated photodetection
and flexible electronics would not only enhance the detectors functionalities, but also
reduce the time delay by performing image processing locally, making it promising for
adaptive multi-spectral photodetection and sensing.
We report a longwave infrared quantum dot infrared photodetector working at room
temperature (RT) (298K). A high photoresponsivity and photodetectivity of 0.02A/W and
9.0x106 cmHz1/2/W were achieved at 298K with a low bias voltage of -0.1V. The RT
QDIP avoids bulk and heavy cryogenic cooling systems and thus enables the
development of ultra-compact IR sensing and imaging systems.
We report a very longwave Infrared (> 14 μm) quantum dot photodetector working at 77 K. Very longwave
infrared (VLWIR) detection at a cut-off wavelength of 15.3 μm was achieved through QD size engineering.
Peak specific photodetectivity D* of 3.3x108 cmHz1/2/W. A large photoresponsivity of 0.93 A/W and high
photoconductive gain of 62.4 were demonstrated at a bias voltage of V = 3.7 V at T = 77 K. The low-bias
and liquid nitrogen temperature performance demonstration based on InAs-GaAs material systems
indicates that the QDIP technology is promising for VLWIR sensing and imaging.
We propose a new smart photodetector with adaptive multi-spectral polarization sensing and signal
processing capabilities. The smart photodetector consists of a voltage-tunable multi-spectral polarimetric
quantum dot infrared photodetector and high-speed (>5.6GHz) flexible electronics printed on the QDIP.
Such integrated photodetection and on-chip processing would not only greatly enhance the detectors
functionalities, but also substantially reduce the time delay by performing image processing locally.
A voltage-tunable multispectral 320×256 infrared imaging focal plane array (FPA) is reported. The multispectral FPA is
based on InAs/GaAs quantum dots infrared photodetectors (QDIP) with different capping layers (i.e. GaAs and In0.20Ga0.80As), corresponding to the extended middle-wave infrared (EMIR, 5-8 μm) and long-wave infrared (LWIR, 8-
12 μm) detection bands, respectively. The FPA shows a sensitivity of 8.2 mV/C a noise equivalent temperature
difference of 172 mK at the FPA operating temperature of 67 K. Thermal images were obtained at both the EMIR and
the LWIR bands at a low FPA bias of -0.7V. Voltage-tunable multispectral imaging was also achieved. Since each of the
detection spectral of the QD FPA can be individually tuned by engineering its QD capping layer, this approach offers
greater flexibility in designing detection spectrum of a multispectral FPA.
A monolithically integrated wire grid polarizer and quantum dot infrared photodetector is reported. The photodetector array is integrated with a single large area aluminum wire grid polarizer that was fabricated using standard photolithographic procedures. The polarizer has period of 4μm and a 50% duty cycle. The device has an extinction ratio of 3dB for normal incidence long wavelength infrared radiation.
A hyper-spectral quantum dot infrared photodetector (QDIP) based on doublecavity
comb filter is reported. The hyperspectral QDIP uses a double cavity comber filter
and a novel transparent conductive carbon nanotube (CNT) thin-film network as the
electrode. By tuning the bias of the transparent electrode coated on the membrane, the
cavity length and corresponding passband of the filter can be changed accordingly with
low optical loss. Such MEMS-based hyper-spectral QDIP would also enable quick
spectral scan of IR characteristics of chemical and biological materials.
A high-speed flexible transistor made with an ultrapure carbon nanotube (CNT) solution is reported. The carrier transport layer of the CNT-based flexible transistor is formed at room temperature by dispensing a tiny droplet of an electronics-grade CNT solution. Ultra high field-effect mobility of ~ 48,000 cm2/(V×s) has been demonstrated on a thin-film field effect transistor (TFT). A simple trans-impedance voltage follower circuit was made using the CNT-TFT on a transparency film. The circuit exhibited a high modulation speed of 312 MHz and a large current-carrying capacity beyond 20 mA. The transparency and the sheet resistance of the CNT-film were also characterized at different wavelengths. The ink-jet printing-compatible process would enable mass production of large-area electronic circuits on virtually any desired flexible substrate at low cost and high throughput.
A voltage-tunable multi-band quantum dot infrared focal plane array (FPA) is reported. The FPA consists of a 320x256 quantum dot infrared photodetector (QDIP) array hybridized to a readout integrated circuit (ROIC). Each of the QDIP pixels consists of vertically-stacked InAs quantum dots layers with three different capping layers for
multi-band (SWIR, MWIR, and LWIR) absorption. By tuning the bias voltage, the FPA is capable of detecting infrared bands individually or simultaneously. High photodetectivity values of greater than 2.3×1010cmHz1/2/W were obtained for the various detection bands. Voltage-controllable detection band selection enables real-time image contrast enhancement and discrimination.
We present an electrically-controllable multi-spectral quantum dot infrared photodetector (QDIP). The QDIP consists of vertically-stacked InAs quantum dots layers with two different capping layers for MWIR and LWIR absorption, respectively. The multi-spectral QDOP is capable of simultaneously detecting multi-spectral normal incidence through inter-subband transitions in the three-dimensional (3-D) confined quantum dot nanostructures. The QDIP showed multi-color IR detection bands centered at 5.6μm, 7.7 μm and 10.0μm, respectively. By tuning the bias voltage, the detection band can be individual turned on. High photodetectivity of > 2.3×1010cmHz1/2/W were obtained for these IR detection bands. The voltage-controllable detection band selection enables real-time system reconfiguration to focus on the band of interest. The vertically-stacked device structure allows easy construction of focal plane arrays (FPA).
An all-optical nonlinear threshold gate based on weakly-coupled, high-order
microring resonators were investigated using the transmission matrix formalism. A Kerr
nonlinear enhancement factor of exceeding 2.5x103 can be obtained at the ring-coupling
coefficient of 0.02. Simulation results show that the nonlinear optical threshold gate has a
sharp optical intensity-dependant switching property with a low switching threshold (>
80%) of -10dBm.
A thermo-optically tunable fiber ring laser has been constructed. The laser is based on a polymer-spaced Fabry-Pérot (F-P) étalon with a cavity length of 470-µm and an ultra-low polarization-dependent loss (PDL) of <0.1 dB. A wavelength tuning range of ~1.4 nm and a high wavelength stability of ~0.02 nm have been demonstrated without involving any moving mechanical parts. Such a nonmechanical tunable fiber laser structure leads to a reduced device size and allows easy device packaging due to the ultra-low PDL of the wavelength tuning element.
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