Multi-channel interference widely tunable laser with back-emission for high-precision wavelength control

We present a multi-channel interference (MCI) widely tunable laser with back-emission for precise wavelength control, offering a tuning range over 50 nm with a frequency precision of ±0.1 GHz at 30°C. The fabricated laser consistently maintains a side-mode suppression ratio (SMSR) greater than 43 dB across the entire tuning range, with a threshold current varying between 21 and 37 mA. Utilizing a 2 × 2 multimode interference (MMI) coupler instead of the dual-port multimode interference reflector (MIR) for beam splitting, the device reduces output loss, boosts power, and significantly improves slope efficiency by 25%. Wavelength locking is achieved through back-emission light, ensuring wavelength stability within ±1.5 pm over 20 h of continuous operation. The laser remains lockable even when the semiconductor optical amplifier (SOA) is turned off, making it ideal for applications that require continuous and high-precision ranging.