Terahertz-wave detector on silicon carbide platform

We developed a novel terahertz-wave detector fabricated on a SiC platform implementing an InP/InGaAs Fermi-level managed barrier (FMB) diode. The FMB diode epi-layers were transferred on a SiC substrate, and a waveguide coupler and filters were monolithically integrated with an FMB diode. Then, fabricated detector chip was assembled in a fundamental mixer module with a WR-3 rectangular-waveguide input port. It exhibited a minimum noise equivalent power as low as 3e-19 W/Hz at around 300 GHz for a local oscillator power of only 30 microwatts.

Direct limits for scalar field dark matter from a gravitational-wave detector

The nature of dark matter remains unknown to date, although several candidate particles are being considered in a dynamically changing research landscape1. Scalar field dark matter is a prominent option that is being explored with precision instruments, such as atomic clocks and optical cavities2–8. Here we describe a direct search for scalar field dark matter using a gravitational-wave detector, which operates beyond the quantum shot-noise limit. We set new upper limits on the coupling constants of scalar field dark matter as a function of its mass, by excluding the presence of signals that would be produced through the direct coupling of this dark matter to the beam splitter of the GEO600 interferometer. These constraints improve on bounds from previous direct searches by more than six orders of magnitude and are, in some cases, more stringent than limits obtained in tests of the equivalence principle by up to four orders of magnitude. Our work demonstrates that scalar field dark matter can be investigated or constrained with direct searches using gravitational-wave detectors and highlights the potential of quantum-enhanced interferometry for dark matter detection.

Modelling a mechanical antenna for a calibrator for interferometric gravitational wave detector using finite elements method

Interferometric gravitational wave detectors (IGWD) are a very complex detector, the need to lock the detector in a dark fringe condition besides the vibrations that affect the mirrors, creates the necessity of using active suspension systems. These active systems make the system reach the desired sensitivity but make the calibration of such detectors much more difficult. To solve this problem a calibrator is proposed, a resonant mass gravitational wave detector could be used to detect the same signal in a narrower band and use the measured amplitude to calibrate the IGWD, as resonant mass gravitational wave detectors are easily calibrated. This work aims to design the mechanical antenna of such a calibrator. The main difficulty is to design the calibrator is the frequencies required to make the detection. These massive detectors usually were made in frequencies close to 1 kHz and the frequency range to operate for better sensitivity is around 100 Hz. The antenna is modelled in finite elements method and a design of such an antenna is presented.

Obtaining the frequencies of Schenberg detector sphere using finite element modelling

The resonant-mass gravitational wave detector SCHENBERG is a spherical detector that operates with a central frequency close to 3200 Hz and a bandwidth around 200 Hz. It has a spherical mass that works as an antenna whose weight is 1150 kg and is connected to the outer environment by a suspension system designed to attenuate local noise due to seism as well as other sources; the sphere is suspended by its center of mass. When a gravitational wave passes by the detector, the antenna is expected to vibrate. This motion should be monitored by six parametric microwave transducers whose output signals will be digitally analyzed. In order to determine the detector performance better, it is necessary to obtain the vibration frequencies of the sphere with a better precision. To achieve such a goal the sphere with the holes to mount the transducers and the central hole from which the sphere is suspended is simulated in a finite element method program when the gravity is applied to the sphere and the deformation is kept. After that the vibration normal modes of the sphere are calculated and they are compared to the experimental results.

Obtaining the sensitivity of a calibrator for interferometric gravitational wave

Interferometric gravitational wave detectors (IGWD) are a very complex detector, the need to lock the detector in a dark fringe condition besides the vibrations that affect the mirrors, creates the necessity of using active suspension systems. These active systems make the system reach the desired sensitivity but make the calibration of such detectors much more difficult. To solve this problem a calibrator is proposed, a resonant mass gravitational wave detector could be used to detect the same signal in a narrower band and use the measured amplitude to calibrate the IGWD, as resonant mass gravitational wave detectors are easily calibrated. This work aims to obtain the expected sensitivity of such a calibrator by using lumped modelling in such mechanical detectors. The calibrator is modelled as a spring mass system and the sensitivity curve is presented calculated in by a matlab program. The curve shows that using state of art parameters for the detector the final sensitivity is close to the quantum limit and can be used to calibrate the IGWDs.

Theoretical Study on Characteristics of Glow Discharged Neon Gas and Its Interaction With Terahertz Waves

Discharge gases have been used to detect terahertz (THz) waves, however, there are few relevant theoretical studies. The neon glow discharge model is established by COMSOL Multiphysics software, the characteristics of glow discharged neon and the interaction of the discharged gas with THz waves were investigated. The results show that with the increase of THz wave’s frequency, the transmittance increases, the change of plasma discharge characteristics caused by THz wave can be used for THz wave detection. The results provide a theoretical basis for the development of cheap, room temperature THz wave detector with fast response speed, and high sensitivity.

A Semi-Empirical Approach to Gas Flow Velocity Measurement by Means of the Thermal Time-of-Flight Method

This paper presents a method of measuring gas flow velocity based on the thermal time-of-flight method. The essence of the solution is an analysis of the time shift and the shape of voltage signals at the transmitter and at a temperature wave detector. The measurements used a probe composed of a wave transmitter and a detector, both in the form of thin tungsten wires. A rectangular signal was used at the wave transmitter. The time-of-flight of the wave was determined on the basis of the time shift of two selected characteristic points of the voltage waveform at the transmitter and the wave detector. To obtain the correct velocity indication, a correction in the form of a simple power function was applied. From the measurements performed, the relative uncertainty of the method was obtained, from approx. 4% of the measured value at an inflow velocity of 6.5 cm/s to 1% for an inflow velocity of 50 cm/s and higher.