The linewidth enhancement factor of intersubband lasers: From a two-level limit to gain without inversion conditions

Thelinewidth enhancement ( α factor) due to fluctuations in therefractive index induced by carrier fluctuations of intersubband lasers was initially expected to be zero. However, values ranging from −0.5 to 3 have been found experimentally. This paper resolves this controversy showing that counter rotating terms, usually ignored in simulations, are the actual fundamental origin of nonzero α at peak gain even without the inclusion of nonparabolicity and manybody effects, which are however nee ded to explain negative values. For laser without inversion conditions, significant as a potential out of the boxsolution for the elusive room temperature operation of terahertz lasers, α is found to be larger, but still at the same order of magnitude of conventional inverted medium lasers, thus ensuring their applicability to a huge number of spectroscopic applications that require sharp laserlinewidths.

Source: Applied Physics Letters - November 28, 2016 Category: Physics Authors: M. F. Pereira Source Type: research