InAs/GaSb Broken-Gap Heterostructure Laser for Terahertz Spectroscopic Sensing Application

A completely new type of solid-state laser device is presented that offers the potential for achieving significantly increased levels of terahertz (THz) frequency output power at relatively high operating temperatures. Specifically, a double-barrier GaSb/InAs/GaSb heterostructure device concept is introduced that simultaneously leverages resonant electron injection and interband tunneling electron depletion to realize electron-population inversion, while at the same time mitigating the scattering effects that degrade the lasing process. Here, the main innovations are the ability to spatially separate the upper and lower electron populations using the quantum confinement of the double-barrier conduction band well and the valence-band (VB) well (i.e., of the second barrier), respectively, and the depopulation of the VB well by heavy hole interband tunneling. A theoretical analysis of the radiative and nonradiative transition rates based upon a multiband Kane model formalism is used to confirm the large available optical gain and to estimate the lasing output power at very long wavelengths. Therefore, this study establishes the initial foundation for a solid-state THz laser that can provide significant levels of output power below 1 THz. Furthermore, the inherently high spectral purity and natural tunability offered by this novel laser technology will be instrumental in future spectroscopic analysis of nanoscale biological and/or organic systems that are well known to possess unique spectral signatures at very long wavelengths.