High-temperature terahertz quantum-cascade lasers: design optimization and experimental results

Abstract

Objectives. Terahertz quantum-cascade lasers (THz QCLs) are compact solid-state lasers pumped by electrical injection to generate radiation in the range from 1.2 to 5.4 THz. The THz QCL operating frequency band contains absorption lines for a number of substances that are suitable for biomedical and environmental applications. In order to reduce the size and cost of THz QCLs and simplify the use of THz sources in these applications, it is necessary to increase the operating temperature of lasers.Methods. To calculate electron transport in THz QCLs, we used a system of balance equations based on wave functions with reduced dipole moments of tunnel-bound states.Results. As a result of the calculations, an original band design with a period based on three GaAs/Al0.18Ga0.82As quantum wells (QWs) and a gain maximum at about 3.3 THz was proposed. Based on the developed design, a THz QCL was fabricated, including the growth of a laser structure by molecular beam epitaxy, postgrowth processing to form strip lasers with a double metal waveguide, as well as an assembly of lasers mounted on a heat sink. The developed THz QCLs was capable of lasing at temperatures of up to 125 K as predicted by the performed calculations. We also studied band designs based on two GaAs/AlxGa1–xAs QWs having varying aluminum contents in the barrier layers (x = 0.20, 0.25, and 0.30).Conclusions. The calculated temperature dependences of the peak gain for two-QW designs with x > 0.2 confirm the possibility of creating THz QCLs operating at temperatures above 200 K. Thus, we have proposed two-QW band designs that outperform existing high-temperature designs in terms of maximum operating temperature.

Active coplanar transmission line based on double-barrier GaAs/AlAs resonant tunneling diodes

“…Considerable progress has been achieved in the generation of frequencies from 100 GHz to 1 THz with the use of multipliers, Gunn diodes [3], and high-electron-mobility transistors [4]. The operating parameters (temperature and output radiation power) of quantum cascade lasers with operating frequencies from 1.5 to 5 THz are improving constantly [5,6]. Resonant tunneling diodes (RTDs), which have the capacity to operate at room temperature and achieve emission frequencies in excess of 1 THz, are another type of promising microwave and THz radiation sources.…”

Terahertz wave rectification in a ferroelectric triglycine sulfate single crystal

“…The development of modern laser and terahertz (THz) technologies have led to a significant expansion of the field of practical applications of nonlinear optical effects in the field of (opto)electronics and photonics [1][2][3]. An approach based on controlling the properties of nonlinear optical systems by varying the intensity of the excitation radiation opens up new prospects for creating high-speed energy-efficient devices in electronics and photonics [2].…”