Abstract
We review the history, development, design principles, experimental operating characteristics, and specialized architectures of interband cascade lasers for the mid-wave infrared spectral region. We discuss the present understanding of the mechanisms limiting the ICL performance and provide a perspective on the potential for future improvements. Such device properties as the threshold current and power densities, continuous-wave output power, and wall-plug efficiency are compared with those of the quantum cascade laser. Newer device classes such as ICL frequency combs, interband cascade vertical-cavity surface-emitting lasers, interband cascade LEDs, interband cascade detectors, and integrated ICLs are reviewed for the first time.
Highlights
The type-II interband cascade laser (ICL) has recently gained acceptance as an important coherent optical source for the mid-wave infrared spectral band
It is useful to view the waveguide as constructed from the following basic building blocks: (1) the active core, (2) n-doped optical claddings, most commonly comprised of InAs/AlSb short-period superlattices (SLs), bulk alloys such as AlGaAsSb provide an alternative [74,75], and n-InAs may be employed when the ICL is grown on an InAs substrate [76]; (3) lightly n-doped GaSb separate-confinement layers (SCLs); and (4) transition SLs that separate the other three regions from each other, and from the GaSb substrate/buffer and n+-InAs(Sb) top contact
This is not the case for a quantum cascade detector (QCD) processed in parallel with a QCL, due to the “extraction” subband lying about one optical phonon energy below the lower lasing level to provide rapid depopulation following a stimulated emission event
Summary
The type-II interband cascade laser (ICL) has recently gained acceptance as an important coherent optical source for the mid-wave infrared spectral band (mid-IR, defined here as spanning 3–6 μm). It combines a relatively long upper-level lifetime, characteristic of semiconductor interband transitions, with the voltage-efficient cascading scheme originally introduced for the quantum cascade laser (QCL, which employs intersubband transitions to produce light). The most pervasive application involves the sensing of trace gases such as methane, carbon dioxide, carbon monoxide, formaldehyde, etc., in ambient air [1] While this typically requires cw emission into a single spectral mode, low output powers on the order of 1 mW are generally sufficient. Following a discussion of the mechanisms limiting ICL performance at different mid-IR wavelengths, we offer some thoughts on the prospects for future improvements
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