Carrier Leakage and Mirror Loss in Interband Cascade Lasers

Abstract

This study investigates the effect of laser facet reflectivity modification on the leakage current and internal efficiency for interband cascade lasers (ICLs) emitting in mid-infrared region. Mid-infrared region of the spectrum (3µm to 5µm) is comprised of two atmospheric transmission windows as well as several absorption bands of greenhouse gasses and water and offers applications in free-space communications, sensing, and biomedical fields. Interband cascade lasers with continuous wave (CW) room-temperature (RT) power of exceeding 500mW [2] as well as quantum cascade lasers (QCL) can be employed for such applications. Extensive research has been dedicated to band structure engineering in order to increase carrier confinement in the active quantum wells of cascade lasers. However, they are still suffering from low characteristic temperatures of threshold current and slope efficiency, which have been linked to the existence of alternative paths that allow the carriers to escape the active region and lower the device efficiency [3]. For this study, single- and multi-layer material combinations suitable for mid-infrared anti-reflection (AR) coatings including Ta2O5, ZrO2 and Al2O3 single layer AR coatings and ZnS-YF3 and ZnS-SiO2 and TiO2-SiO2 double layer AR coatings have been applied to ICL devices and the laser performance was measured before and after the coating.