GaSb diode lasers tunable around 2.6 <b> <i>μ</i> </b>m using silicon photonics resonators or external diffractive gratings

Abstract

We report two tunable diode laser configurations emitting around 2.6 μm, where the gain is provided by a high-gain GaSb-based reflective semiconductor optical amplifier. The lasers are driven in pulsed mode at 20 °C, with a pulse width of 1 μs and 10% duty cycle to minimize heating effects. To demonstrate the broad tuning and high output power capability of the gain chip, an external cavity diode laser configuration based on using a ruled diffraction grating in a Littrow configuration is demonstrated. The laser shows a wide tuning range of 154 nm and a maximum average output power on the order of 10 mW at 2.63 μm, corresponding to a peak power of 100 mW. For a more compact and robust integrated configuration, we consider an extended-cavity laser design where the feedback is provided by a silicon photonics chip acting as a reflector. In particular, the integrated tuning mechanism is based on utilizing the Vernier effect between two thermally tunable micro-ring resonators. In this case, a tuning range of around 70 nm is demonstrated in a compact architecture, with an average power of 1 mW, corresponding to a peak power of 10 mW.