The invention relates to a laser device for emitting waves in a frequency range belonging to the terahertz range, characterized in that it includes the following, in combination: a wave guide (1) extending longitudinally along an axis A-A'; a superconducting coil (4) arranged coaxially to the wave guide (1) and arranged at a first end (112) of the wave guide (1); a p-Ge p-doped germanium crystal (3) arranged inside the coil (4) such that the turns of the superconducting coil (4) at least partially surround said p-Ge crystal (3); a cooling means (7) containing a coolant, the superconducting coil (4) and the p-Ge crystal (3) being arranged in the cooling means (7), and the wave guide (1) partially extending outside the cooling means (7); and a means (13) for removing the coolant from the wave guide

We study the broadband photovoltaic response of field effect transistors on terahertz radiation. A simple physical analytical model of the response is developed. It is based on plasma density perturbation in the transistor channel by the incoming terahertz radiation. The model shows how the non-resonant detection signal is related to static (dc) transistor characteristics. We analyze loading effects related to capacitive, inductive, and resistive coupling of the detector to the read-out circuit as a function of modulation frequencies and loading resistors. As we show, the proposed physical model completed by loading effects fully describes the experimental results on the non-resonant sub-terahertz detection by all studied III-V (GaAs, GaN) and silicon based transistors. Field effect transistors were recently proposed as the best terahertz detecting pixels for fabrication of low cost focal plane arrays for terahertz imaging. This article gives prospects for electrical simulation of these transistors and their optimal integration in the focal plane arrays.

Field Effect Transistors for Terahertz Detection and Emission

THz detection by plasma wave mechanism in InGaAs HEMTs is studied in high/quantizing magnetic fields regime. The correlation between the photovoltaic response and magnetoresistance is revealed. It allows to explain the nature of strong oscillations observed in the transistor Terahertz photoresponse.

Resonant frequencies of the two-dimensional plasma in field effect transistors (FETs) increase with the reduction of the channel dimensions and can reach the THz range for nanometer size devices. Nonlinear properties of the electron plasma in the transistor channel can lead to the detection and emission of THz radiation. The excitation of plasma waves by sub-THz and THz radiation was experimentally demonstrated at cryogenic as well as at room temperatures. We present an overview of experimental results on THz detection by FETs discussing possibilities of improvement of their performance and application for THz room temperature imaging. We present also recent results on THz emission from GaN/AlGaN-based FETs

We evaluate the optical performance of AlGaN/GaN MISFETs as a non-resonant sub-terahertz, room temperature detector. The single-pixel responsivity and the noise equivalent power are determined. The efficiency of the detection is demonstrated by the room temperature imaging of different solutions of acetone in cyclohexane..

We review a few recent results concerning the physics and applications of FETs as Terahertz detectors and emitters. Particulary we stress results concerning dependance of THz detection and emission on high/quantizing magnetic fields and the geometry of the FETs channel.