Characterization of talbot-cavity quantum cascade lasers

Abstract

Quantum Cascade Lasers (QCLs) are effective sources of laser emissions in the mid-infrared spectral region (MIR), operating on the principle of quantum well intersubband transitions. Talbot Cavity QCLs are QCLs implemented with the concept of the Talbot Effect, and this paper studies the parameters that were identified and expected to affect the output transmission level of the Talbot Cavity QCLs, and hence characterize the Talbot Cavity QCLs. The parameters that were studied include the number of laser ridges, the varying of the Talbot Cavity length, the ridge-to-ridge spacing, the facet material as well as the introduction of defects into the Talbot Cavity. The simulations of the Talbot Cavity QCLs were conducted on the software Lumerical FDTD. It was observed that increasing the number of laser ridges optimizes the far-field transmission output. It was observed that by varying the Talbot Cavity length, the output transmission levels for the in-phase, out-of-phase and supermodes will recombine at certain points in the propagation approximated by the Talbot Effect equation. Increasing the ridge-to-ridge spacing resulted in better supermode discrimination but lower output transmission level. The transmission output level was observed to be lower for the configuration with the perfect absorber facet material as compared to the configuration with the mirror facet material. The results from the introduction of defects into the Talbot Cavity would provide useful information in determining the position of the defects that could be introduced into the physical Talbot Cavity to suppress undesirable supermodes of propagation and optimize a desired mode of propagation.