Terahertz single-photon detectors based on quantum wells

The paper presents the experimental results of studying the dynamics of electron energy relaxation in structures made of thin (d ≈ 6 nm) disordered superconducting vanadium nitride (VN) films converted to a resistive state by high-frequency radiation and transport current. Under conditions of quasi-equilibrium superconductivity and temperature range close to critical (~ Tc), a direct measurement of the energy relaxation time of electrons by the beats method arising from two monochromatic sources with close frequencies radiation in sub-THz region (ω ≈ 0.140 THz) and sources in the IR region (ω ≈ 193 THz) was conducted. The measured time of energy relaxation of electrons in the studied VN structures upon heating of THz and IR radiation completely coincided and amounted to (2.6–2.7) ns. The studied response of VN structures to IR (ω ≈ 193 THz) picosecond laser pulses also allowed us to estimate the energy relaxation time in VN structures, which was ~ 2.8 ns and is in good agreement with the result obtained by the mixing method. Also, we present the experimentally measured volt-watt responsivity (S~) within the frequency range ω ≈ (0.3–6) THz VN HEB detector. The estimated values of noise equivalent power (NEP) for VN HEB and its minimum energy level (δE) reached NEP@1MHz ≈ 6.3 × 10–14 W/√Hz and δE ≈ 8.1 × 10–18 J, respectively.

In this paper a dual laser acousto-optical diffraction technique is described that provides an absolute calibration of a CO2 laser coherent scattering apparatus and other heterodyne receivers. Rather than directly detecting the sound pressure of the acoustic field or the power diffracted from the CO2 laser beam, the sound pressure is measured with the heterodyne detection of acousto-optical diffraction from a He-Ne laser beam. Noise equivalent power (NEP) measurement of the heterodyne receiver for the CO2 laser scattering apparatus and the studies of the detector bias and local oscillator power dependence of NEP values are performed by this technique. The measured minimum NEP value (6.8×10−20 W/Hz) is very close to the quantum noise limit.

A hybrid antenna consisting of a patch cavity and a metal grating is designed in this work. This antenna can effectively localize and enhance the intensity of the electric field inside a quantum well photodetector (QWP). The optical properties of the designed antenna are theoretically investigated, and it is found that the electric field can be increased by a factor of ∼104 in the infrared region (6–10 μm) and ∼105 in the terahertz (THz) region (100 μm). These enhancements can greatly improve the performance of QWPs. In the THz region, it is theoretically estimated that the hybrid antenna can increase the working temperature of the detector to 195 K, and the noise equivalent power is theoretically estimated to be as low as ∼10−18 W/Hz0.5 at T = 4 K and ∼10−15 W/Hz0.5 at room temperature, T = 300 K. These results are of great significance for applications of QWPs.

This paper describes a CMOS rail-to-rail class AB operational amplifier designed to have extremely low output impedance and large current-drive capability. The amplifier uses an innovative output stage, having both source follower and common source stages working simultaneously throughout the output common-mode range. The source follower ensures low output impedance, which enables it to drive relatively large load capacitors, while the common-source gain stage provides high current drive. Furthermore, the circuit is fully functional with supplies as low as 1.5 V. The amplifier is capable of driving a maximum output current of /spl plusmn/7 mA with only 140 /spl mu/A of total quiescent current, making it power efficient, and thus appropriate for low voltage battery-powered applications.

The Ocean Color and Temperature Scanner (OCTS) is a piece of observation equipment that measures ocean color and temperature from a scientific satellite. The OCTS is equipped with two focal plane assemblies: one observes ocean color in the range of visible to near infrared, and the other measures ocean temperature in the infrared region. We report here results of the so-called break boad model of the latter focal plane assembly. This focal plane assembly contains four infrared detectors that are cooled to 100 K by radiational cooling. We have evaluated this cooled focal plane assembly, and have confirmed that it has satisfied such NEP (noise equivalent power) values, registration accuracy and power consumption as are required in view of the OCTS performance characteristics.

This letter presents a G-band detector in a 45 nm silicon-on-insulator CMOS technology. The measured detector responsivity is 3 kV/W at 170-180 GHz with a 3 dB bandwidth of 150-210 GHz. The detector results in a Noise-Equivalent-Power (NEP) of 8-10 pW/Hz1/2 at a bias current of 50-200 μA for an IF of 10 MHz and is well matched with an input return loss > 10 dB at 167-194 GHz. The responsivity and NEP values are close to the best SiGe detectors, and show that advanced CMOS nodes are suitable for ~ 200 GHz imaging arrays.

Optoelectronic properties comparison of 10 and 20 multi quantum wells Ga0.952In0.048N0.016As0.984/GaAs p-i-n photodetector for 1.0 μm wavelength

This paper presents floating gate MOSFET (FGMOS)-based second generation differential voltage current conveyor (DVCCII) at low voltage levels. In analog circuit design, the FGMOS transistors are very often used in low voltage circuits, where the reduction obtained in the transistor apparent threshold voltage is of great importance. The given circuit provides very high input impedance at its Y-terminals, low output impedance at X-terminal and high impedance at Z-terminals and consumes less power. This circuit is a powerful building block, especially for applications demanding differential or floating inputs. The circuit behavior has been verified using PSpice simulations for 0.5 μm technology and indicates the excellent performance.

Novel high-voltage (HV), low-impedance voltage multipliers are described, which are capable of operating at high pulse repetition frequencies (PRF). Pulse generation is actively initiated by a HV thyratron operating below 40 kV and in the socalled RADAR mode for long life. The multiplier stages are switched with a high-performance, multi-winding, saturable-core inductor. This concept’ permits the construction of high-PRF megavolt pulsers with low output impedance (5 to 50 R) for use in high-energy accelerators, e-guns, X-ray generators and other pulsed power devices. Voltage risetimes in the 20 ns to 50 ns range are possible. Various multiplier configurations are discussed, including Marx banks, multistage LC-inverters and spiral generators. Results of computer simulations of sample pulsers are presented. A reliable 4-stage LC-inverter has been built, which generates 100 kV, 1.2 kA pulses at 200 hertz. It drives a low-impedance e-gun diode which is part of an X-ray generator.

This letter presents several configurations of terahertz (THz) pixel structures with different bow-tie antennas and field-effect transistor (FET)-based detectors, implemented in a 0.15-μm standard CMOS technology, operating at a radiation frequency range of 0.85-1 THz for CMOS imaging applications. The innovative FET detector structures are investigated for higher power coupling efficiency with the integrated antennas, aiming to improve the THz detection behavior in terms of responsivity and noise equivalent power. Experimental THz characterization of the fabricated structures provides the guidelines for the future implementation of THz imaging arrays. Images of concealed metallic objects are acquired in a single-pixel mode under continuous THz illumination.

This paper investigates terahertz detectors fabricated in a low-cost 130 nm silicon CMOS technology. We show that the detectors consisting of a nMOS field effect transistor as rectifying element and an integrated bow-tie coupling antenna achieve a record responsivity above 5 kV/W and a noise equivalent power below 10 pW/Hz(0.5) in the important atmospheric window around 300 GHz and at room temperature. We demonstrate furthermore that the same detectors are efficient for imaging in a very wide frequency range from ~0.27 THz up to 1.05 THz. These results pave the way towards high sensitivity focal plane arrays in silicon for terahertz imaging.

Indium doped silicon (Si:In) material has been used to fabricate the detector elements for an infrared (IR) radiometer array. The array will be employed in experiments on a spaceborne platform, where a low radiation background (fiDg < 109 cm^-2sec^-1) and a low operating temperature (T < 20 K) is provided. The performance of the Si:In detectors has been characterized prior to the assembly of the array. Test results will be presented for the spectral responsivity, the linearity, the frequency behaviour, the noise equivalent power values and the cross talk.

Resonant excited carriers in quantum well will relax to the ground states and cannot escape from quantum wells to form photocurrent. However, it was recently observed that most of the photo-excited carriers in InGaAs/GaAs quantum wells within a p-n junction escape from quantum wells and form photocurrent rather than relax to the ground state of the quantum wells. The absorption coefficient of multiple quantum wells is also enhanced by a p-n junction. According to the phenomenon, a novel photon detector based on interband transition of strained InGaAs/GaAs quantum wells was fabricated. Without an anti-reflection layer, the external quantum efficiency up to 31% with only 100 nm absorption thickness was measured, corresponding an absorption coefficient of 3.7×10 4 cm -1 that is obviously higher than previously reported values. The room temperature detectivity of the device was 1.43×10 13 cm Hz 1/2 W -1 . For strained InAsSb/GaSb quantum wells material system, the detector showed a narrow response range from 2.1 μm to 3.0 μm with a peak around 2.6 μm at 200 K and a wide response range from 3.5 μm to 5.7 μm. The photon detectors based on interband transition show great potential applications in infrared detection operating at high temperature.

Enhancing electromagnetic coupling to achieve interaction between light and matter is imperative to develop high-performance terahertz devices. Here, we report an ultrasensitive terahertz detector based on the quasi-one-dimensional, low-energy Dirac Fermions in the topological semimetal-TaNiTe5, integrated with an asymmetric bow-tie antenna to enhance field localization and directional light coupling. The device operates via photothermoelectric (PTE) effect, enabling self-powered, homo/heterodyne dual-mode detection across from millimeter to terahertz band. It achieves room-temperature operation at 0.435 THz with a responsivity of 0.77 A/W, a noise equivalent power (NEP) below 9.71 pW·Hz1/2, a specific detectivity (D*) of 1.03 × 1011 Jones, and a response time less than 20 ns. Furthermore, owing to the unique electronic band structure and excellent carrier dynamics characteristics of the semimetal-TaNiTe5, the device enables heterodyne mixing with a radio frequency (RF) bandwidth exceeds 108 GHz, accompanied by intermediate frequency (IF) bandwidth >26.5 GHz. Leveraging its excellent performance, we demonstrate its potential for sub-THz communications and high-quality imaging in terms of encrypted data-information exchange. Our work establishes a strategy for achieving chip-level integration with versatile abilities for communication, and imaging at terahertz band.

All-dielectric resonant waveguide based quantum well infrared photodetectors for hyperspectral detection