Room temperature continuous wave, monolithic tunable THz sources based on highly efficient mid-infrared quantum cascade lasers.

Quanyong Lu,Donghai Wu,Saumya Sengupta,Manijeh Razeghi,Steven Slivken

doi:10.1038/srep23595

Abstract

A compact, high power, room temperature continuous wave terahertz source emitting in a wide frequency range (ν ~ 1–5 THz) is of great importance to terahertz system development for applications in spectroscopy, communication, sensing, and imaging. Here, we present a strong-coupled strain-balanced quantum cascade laser design for efficient THz generation based on intracavity difference frequency generation. Room temperature continuous wave emission at 3.41 THz with a side-mode suppression ratio of 30 dB and output power up to 14 μW is achieved with a wall-plug efficiency about one order of magnitude higher than previous demonstrations. With this highly efficient design, continuous wave, single mode THz emissions with a wide frequency tuning range of 2.06–4.35 THz and an output power up to 4.2 μW are demonstrated at room temperature from two monolithic three-section sampled grating distributed feedback-distributed Bragg reflector lasers.

Highlights

A compact, high power, room temperature continuous wave terahertz source emitting in a wide frequency range (ν ~ 1–5 THz) is of great importance to terahertz system development for applications in spectroscopy, communication, sensing, and imaging
We design and demonstrate a broadband, strong-coupled, strain-balanced quantum cascade lasers (QCLs) active region design with a large nonlinear susceptibility for high power continuous wave (CW) THz emission in a wide frequency range based on difference-frequency generation (DFG)
Continuous, single mode emission at 3.41 THz with a side-mode suppression ratio (SMSR) of 30 dB and output power of 14 μW is achieved, and continuous wave electrical tuning of 2.06–4.35 THz with a THz power up to 4.2 μW is demonstrated from two monolithic three-section sampled grating distributed feedback-distributed Bragg reflector (SGDFB-DBR) lasers

Summary

Introduction

A compact, high power, room temperature continuous wave terahertz source emitting in a wide frequency range (ν ~ 1–5 THz) is of great importance to terahertz system development for applications in spectroscopy, communication, sensing, and imaging. Room temperature continuous wave emission at 3.41 THz with a side-mode suppression ratio of 30 dB and output power up to 14 μW is achieved with a wall-plug efficiency about one order of magnitude higher than previous demonstrations. Resonant tunnelling diodes and Schottky diode-based frequency multipliers have demonstrated very promising compact electronic terahertz sources[2,3,4] This category of THz sources has limited bandwidth, poor power efficiency and low output power level beyond 1 THz. Passive optical down-conversion to THz frequencies in bulk nonlinear materials with external pumping sources has been able to produce very high THz power at room temperature[5]. The rather high threshold current density of the device prevented its CW operation

Methods

Results

Conclusion