22 research outputs found
Antenna-Coupled Microcavity Enhanced THz Photodetectors
Plasmonic THz photodetectors have been realized in this work, by implementing the active region of a 5 THz quantum well detector with an antenna-coupled microcavity array. Our results demonstrate a clear improvement in responsivity, polarization insensitivity and background limited performance
Room-Temperature operation of a quantum well mid-infrared detector embedded in nano-antennae array at critical optical coupling
We present the first room temperature photodection of hundreds on nanowatts using a quantum well mid-infrared detector at 9ÎŒm, with a background-limited temperature of 82K and a corresponding background-limited specific detectivity of 1.4Ă1010 cmHz1/2/W. The photonic architecture consists of an array of double metal nano-antennae and allows to reduce the dark current and increase the absorbed electromagnetic field inside the active region, so to prove a high temperature photoresponse
Mixing Properties of Room Temperature PatchâAntenna Receivers in a MidâInfrared (λ â 9 ”m) Heterodyne System
A roomâtemperature midâinfrared (λ = 9 ”m) heterodyne system based on highâperformance unipolar optoelectronic devices is presented. The local oscillator (LO) is a quantum cascade laser (QCL), while the receiver is an antenna coupled quantum well infrared photodetector optimized to operate in a microcavity configuration. Measurements of the saturation intensity show that these receivers have a linear response up to very high optical power, an essential feature for heterodyne detection. By providing an accurate passive stabilization of the LO, the heterodyne system reaches at room temperature the record value of noise equivalent power (NEP) of 30 pW at 9 ”m and in the GHz frequency range. Finally, it is demonstrated that the injection of microwave signal into the receivers shifts the heterodyne beating over the large bandwidth of the devices. This mixing property is a unique valuable function of these devices for signal treatment in compact QCLâbased systems
High sensitivity 9ÎŒm metamaterial Infrared QC detectors at 300K
Quantum Cascade Detectors are promising devices for high-temperature mid-infrared detection. The responsivity, related to its photovoltaic working principle, still suffers from lower responsivity respect to a photoconductive device such as QWIP. Here, we demonstrate that inserting a QCD detector in a photonic metamaterial made of patch-antenna microcavities, we can boost light-matter interaction reaching responsivity value in the order of 50mA/W at room temperature, the highest value reported in the literature
Patch antenna terahertz photodetectors
We report on the implementation of 5 THz quantum well photodetector exploiting a patch antenna cavity array. The benefit of our plasmonic architecture on the detector performance is assessed by comparing it with detectors made using the same quantum well absorbing region, but processed into a standard 45° polished facet mesa. Our results demonstrate a clear improvement in responsivity, polarization insensitivity, and background limited performance. Peak detectivities in excess of 5âĂâ1012 cmHz1/2/W have been obtained, a value comparable with that of the best cryogenic cooled bolometers
Room-temperature nine-”m-wavelength photodetectors and GHz-frequency heterodyne receivers
Room-temperature operation is essential for any optoelectronics technology that aims to provide low-cost, compact systems for widespread applications. A recent technological advance in this direction is bolometric detection for thermal imagingÂč, which has achieved relatively high sensitivity and video rates (about 60 hertz) at room temperature. However, owing to thermally induced dark current, room-temperature operation is still a great challenge for semiconductor photodetectors targeting the wavelength band between 8 and 12 micrometresÂČ, and all relevant applications, such as imaging, environmental remote sensing and laser-based free-space communicationÂł,âŽ,â”, have been realized at low temperatures. For these devices, high sensitivity and high speed have never been compatible with high-temperature operationâ¶,â·. Here we show that a long-wavelength (nine micrometres) infrared quantum-well photodetectorâž fabricated from a metamaterial made of sub-wavelength metallic resonatorsâč,Âčâ°,ÂčÂč,ÂčÂČ exhibits strongly enhanced performance with respect to the state of the art up to room temperature. This occurs because the photonic collection area of each resonator is much larger than its electrical area, thus substantially reducing the dark current of the deviceÂčÂł. Furthermore, we show that our photonic architecture overcomes intrinsic limitations of the material, such as the drop of the electronic drift velocity with temperatureÂčâŽ,Âčâ”, which constrains conventional geometries at cryogenic operationâ¶. Finally, the reduced physical area of the device and its increased responsivity allow us to take advantage of the intrinsic high-frequency response of the quantum detectorâ· at room temperature. By mixing the frequencies of two quantum-cascade lasersÂčⶠon the detector, which acts as a heterodyne receiver, we have measured a high-frequency signal, above four gigahertz (GHz). Therefore, these wide-band uncooled detectors could benefit technologies such as high-speed (gigabits per second) multichannel coherent data transferÂčâ· and high-precision molecular spectroscopyÂčâž
Noise characterization of patch antenna THz photodetectors
Current noise fluctuations have been investigated in terahertz (THz) quantum well photodetectors embedded in antenna-coupled photonic architectures and compared with standard substrate-coupled mesa detectors. The noise measurements give a value of the photoconductive gain that is in excellent agreement with that extracted from previous responsivity calibrations. Moreover, our results confirm that the noise equivalent power (NEP) of the antenna-coupled devices is of the order of 0.2 pW/Hz0.5. This low NEP value and the wide band frequency response (âŒGHz) of the detectors are ideal figures for the development of heterodyne receivers that are, at present, a valuable technological solution to overcome the current limitation of THz sensors
Long-wavelength infrared photovoltaic heterodyne receivers using patch-antenna quantum cascade detectors
Quantum cascade detectors (QCDs) are unipolar infrared devices where the transport of the photoexcited carriers takes place through confined electronic states, without an applied bias. In this photovoltaic mode, the detector's noise is not dominated by a dark shot noise process, and therefore, performances are less degraded at high temperature with respect to photoconductive detectors. This work describes a 9âÎŒm QCD embedded into a patch-antenna metamaterial, which operates with state-of-the-art performances. The metamaterial gathers photons on a collection area, Acoll, much larger than the geometrical area of the detector, improving the signal to noise ratio up to room temperature. The background-limited detectivity at 83âK is 5.5 Ă 1010âcm Hz1/2 Wâ1, while at room temperature, the responsivity is 50âmA/W at 0âV bias. A patch antenna QCD is an ideal receiver for a heterodyne detection setup, where a signal at a frequency of 1.4âGHz and Tâ=â295âK is reported as demonstration of uncooled 9âÎŒm photovoltaic receivers with a GHz electrical bandwidth. These findings guide the research toward uncooled IR quantum limited detection
Mixing properties of room temperature patch-antenna receivers in a mid-infrared ( 9m) heterodyne system
A room-temperature mid-infrared (9 um) heterodyne system based on high-performance unipolar optoelectronic devices is presented. The local oscillator (LO) is a quantum cascade laser, while the receiver is an antenna coupled quantum well infrared photodetector optimized to operate in a microcavity configuration. Measurements of the saturation intensity show that these receivers have a linear response up to very high optical power, an essential feature for heterodyne detection. By an accurate passive stabilization of the local oscillator and minimizing the optical feed-back the system reaches, at room temperature, a record value of noise equivalent power of 30 pW at 9um. Finally, it is demonstrated that the injection of microwave signal into our receivers shifts the heterodyne beating over the bandwidth of the devices. This mixing property is a unique valuable function of these devices for signal treatment