Widely Tunable Coupled Mid-IR Diode Lasers With Side Mode Suppression Ratio Above 40 dB

A novel tunable coupled lasers structure utilizing the Vernier effect and the light coupling mechanism is successfully demonstrated in the wavelength range of 2.35 – $2.39~\mu $ m. The coupling effect between two active S-bend and straight waveguide lasers can enable both a wide tuning range and a very high side mode suppression ratio (SMSR) by choosing an appropriate separation gap between these two lasers. With a separation gap of $5~\mu $ m, a wide tuning range of 40 nm and a stable SMSR of above 40 dB was achieved. Employing a simple structure, this regrowth-free and easily manufactured laser configuration is a highly promising solution for trace-gas sensing applications.