Abstract
In this work, quantum cascade lasers (QCLs) based on strain compensation combined with two-phonon resonance design are presented. Distributed feedback (DFB) laser emitting at ~ 4.76 μm was fabricated through a standard buried first-order grating and buried heterostructure (BH) processing. Stable single-mode emission is achieved under all injection currents and temperature conditions without any mode hop by the optimized antireflection (AR) coating on the front facet. The AR coating consists of a double layer dielectric of Al2O3 and Ge. For a 2-mm laser cavity, the maximum output power of the AR-coated DFB-QCL was more than 170 mW at 20 °C with a high wall-plug efficiency (WPE) of 4.7% in a continuous-wave (CW) mode.
Highlights
Mid-infrared quantum cascade lasers (QCLs) [1] are one of the most promising light sources for many commercial applications
The laser spectrum just above threshold indicates that the device operates on the fundamental mode and we can clearly get the stopband of the fundamental mode when the current is 285 mA
The threshold voltage (Vth) of 13.2–14.2 V was measured over the temperature range of 20–90 °C
Summary
Mid-infrared quantum cascade lasers (QCLs) [1] are one of the most promising light sources for many commercial applications. These practical applications such as gas sensing, free-space communication, and high-resolution spectroscopy [2–5] would require QCL with high power, improved single-mode reliability, and low cost. Since the first distributed feedback (DFB)-QCL was demonstrated in 1997 [6], the performance of these devices has been made strong improvements with the demonstration of room temperature continuous-wave (CW) operation with high power across the mid-infrared region [7–10]. Due to the same amount of loss in two band-edge modes, stable single-mode operation cannot be guaranteed [11].
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