Design and fabrication of a quantum cascade laser with a chirped sampling grating

Abstract

We demonstrate a quantum cascade laser (QCL) with a chirped sampling grating by altering the sampling duty cycle along the cavity. The chirped sampling grating structure, with an asymmetric coupling coefficient, can be realized by holographic exposure combined with optical photolithography. We simulated and compared three different types of sampling structures; the QCLs with a 1.5 mm chirped region and 0.5 mm uniform region can achieve an average output-power ratio of 1.71 between the front and rear facets. The proposed chirped sampling grating structure is helpful in realizing a single-mode QCL with improved power efficiency and low fabrication cost.