Interband cascade lasers

TLDR

ICLs combine diode laser photon generation with quantum cascade multi‑stage design to enhance current efficiency. This review surveys the current status of midwave infrared interband cascade lasers. The review covers theoretical active‑region design, MBE growth, device processing (broad‑area, narrow‑ridge, DFB), and experimental performance of pulsed and continuous‑wave ICLs. ICLs exhibit far lower threshold drive powers than QCLs across 3–6 µm, making them preferred for portable mid‑IR spectroscopy, with room‑temperature thresholds as low as 29 mW, output powers over 400 mW, and efficiencies up to 18 %.

Abstract

We review the current status of interband cascade lasers (ICLs) emitting in the midwave infrared (IR). The ICL may be considered the hybrid of a conventional diode laser that generates photons via electron–hole recombination, and an intersubband-based quantum cascade laser (QCL) that stacks multiple stages for enhanced current efficiency. Following a brief historical overview, we discuss theoretical aspects of the active region and core designs, growth by molecular beam epitaxy, and the processing of broad-area, narrow-ridge, and distributed feedback (DFB) devices. We then review the experimental performance of pulsed broad area ICLs, as well as the continuous-wave (cw) characteristics of narrow ridges having good beam quality and DFBs producing output in a single spectral mode. Because the threshold drive powers are far lower than those of QCLs throughout the λ = 3–6 µm spectral band, ICLs are increasingly viewed as the laser of choice for mid-IR laser spectroscopy applications that do not require high output power but need to be hand-portable and/or battery operated. Demonstrated ICL performance characteristics to date include threshold current densities as low as 106 A cm−2 at room temperature (RT), cw threshold drive powers as low as 29 mW at RT, maximum cw operating temperatures as high as 118 °C, maximum cw output powers exceeding 400 mW at RT, maximum cw wallplug efficiencies as high as 18% at RT, maximum cw single-mode output powers as high as 55 mW at RT, and single-mode output at λ = 5.2 µm with a cw drive power of only 138 mW at RT.