Abstract: We report the results of our study on the noise performance of a fast THz detector based on the repurpose of hot electron bolometer mixer (HEB). Instead of operating with an elevated bath temperature, microwave power is injected into the HEB device, which enhances the sensitivity of the detector and at the same time provide a mechanism for reading out impedance changes of the device induced by the modulated incident THz radiation [1]. We have demonstrated an improvement of the detector’s optical noise equivalent power (NEP). Furthermore, by introducing a homodyne readout scheme based on a room temperature microwave mixer, the dynamic range of the detector is increased. The HEB devices used in this work were made of 4 nm thick NbN film. The detector chips were installed into a waveguide mixer block fitted with a corrugated horn, mounted on the cold plate of a liquid helium cryostat. The HEBs were operated at a bath temperature of 4.2 K. The signal beam was terminated on black bodies at ambient and liquid nitrogen temperatures. A chopper wheel placed in front of the cryostat window operating at a frequency of 1.48 kHz modulated the input load temperature of the detector. A cold mesh filter, centered at 830 GHz, was used to define the input signal power bandwidth. Microwave was injected through a broadband directional coupler inside the cryostat. Our experiments were mostly conducted at a pump frequency of 1.5 GHz. The reflected microwave power from the HEB device was fed into a cryogenic low noise amplifier (LNA). The output of the LNA was connected to the RF input port of a room temperature microwave mixer, which beat the reflected signal from the HEB using a copy of the original 1.5 GHz injection signal in a homodyne demodulation scheme. The amplitude of the detected power was measured by a lock-in amplifier, which was synchronized to the chopper frequency. Preliminary results yield an optical NEP of ~1 pW/ Hz 1/2 which corresponds to an improvement of a factor of 3 compared to [1], driven mainly by a lowering of the system noise floor. The dynamic range was also increased by similar amount. References 1. A. Shurakov et al. “A Microwave Pumped Hot Electron Bolometric Direct Detector,” submitted on Oct 18, 2013 to Appl. Phys. Let.

Abstract: The high resolution THz gas spectrometer consists of a synthesizer based on Gunn generator with a semiconductor superlattice frequency multiplier as a radiation source, and an NbN hot electron bolometer in a direct detection mode as a THz radiation receiver was presented. The possibility of application of a quantum cascade laser as a local oscillator for a heterodyne receiver which is based on an NbN hot electron bolometer mixer is shown. The ways for further developing of the THz spectroscopy were outlined.

Abstract: Demand for efficient terahertz radiation detectors resulted in intensive study of the carbon nanostructures as possible solution for that problem. In this work we investigate the response to sub-terahertz radiation of detectors with sensor elements based on CVD graphene as well as its derivatives – carbon nanotubes (CNTs). The devices are made in configuration of field effect transistors (FET) with asymmetric source and drain (vanadium and gold) contacts and operate as lateral Schottky diodes. We show that at 300K semiconducting CNTs show better performance up to 300GHz with responsivity up to 100V/W, while quasi-metallic CNTs are shown to operate up to 2.5THz. At 300 K graphene detector exhibit the room-temperature responsivity from R = 15 V/W at f = 129 GHz to R = 3 V/W at f = 450 GHz. We find that at low temperatures (77K) the graphene lateral Schottky diodes responsivity rises with the increasing frequency of the incident sub-THz radiation. We interpret this result as a manifestation of a plasmonic effect in the devices with the relatively long plasmonic wavelengths. The obtained data allows for determination of the most promising directions of development of the technology of nanocarbon structures for the detection of THz radiation.

Abstract: We show the design, a history of development as well as the most successful and promising approaches for QPICs realization based on hybrid nanophotonic-superconducting devices, where one of the key elements of such a circuit is a waveguide integrated superconducting single-photon detector (WSSPD). The potential of integration with fluorescent molecules is discussed also.

Abstract: We present data of quantum detector tomography for the samples specifically optimized for this problem. Using this method, we take results of hot-spot correlation length of 17 ± 2 nm.

Abstract: We present our latest generation of superconducting single-photon detectors (SSPDs) patterned from 4-nm-thick NbN films, as meander-shaped  0.5-mm-long and  100-nm-wide stripes. The SSPDs exhibit excellent performance parameters in the visible-to-near-infrared radiation wavelengths: quantum efficiency (QE) of our best devices approaches a saturation level of  30% even at 4.2 K (limited by the NbN film optical absorption) and dark counts as low as 2x10^-4 Hz. The presented SSPDs were designed to maintain the QE of large-active-area devices, but, unless our earlier SSPDs, hampered by a significant kinetic inductance and a nanosecond response time, they are characterized by a low inductance and GHz counting rates. We have designed, simulated, and tested the structures consisting of several, connected in parallel, meander sections, each having a resistor connected in series. Such new, multi-element geometry led to a significant decrease of the device kinetic inductance without the decrease of its active area and QE. The presented improvement in the SSPD performance makes our detectors most attractive for high-speed quantum communications and quantum cryptography applications.

Abstract: We present a novel concept of photon number resolving detector based on 120-nm-wide superconducting stripes made of 4-nm-thick NbN film and connected in parallel (PNR-SSPD). The detector consisting of 5 strips demonstrate a capability to resolve up to 4 photons absorbed simultaneously with the single-photon quantum efficiency of 2.5% and negligibly low dark count rate.

Abstract: This document provides supplementary information to “Spectrally multiplexed single-photon detection with hybrid superconducting nanophotonic circuits", DOI:10.1364/optica.4.000557. Here we detail the on-chip spectrometer design, its characterization and the experimental setup we used. In addition, we present a detailed report concerning the characterization of the superconducting nanowire single photon detectors. In the final sections, we describe sample preparation and characterization of the nanodiamonds containing silicon vacancy color centers.