Narrow-linewidth tunable semiconductor lasers based on dual-lens external-cavity structure

A narrow-linewidth tunable laser based on a unique dual-lens external-cavity structure was reported, in which a thermally-tuned 50 GHz etalon was utilized to provide standard ITU-grid wavelengths and a PZT-actuated tunable Fabry-Pérot filter to select wavelength. In experiment, the laser wavelength could be tuned from 1525 to 1580 nm, covering the whole C band. And it measured a linewidth of 37.5 kHz, an output power >50 mW at the 400 mA pump current, a SMSR > 50 dB and a tuning speed <3 ms. The performance is superior to the requirements of coherent communication applications and the reported planar waveguide-based counterparts. Moreover, the dual-lens structure bears other merits such as high positioning tolerance and potential for ultra-narrow linewidth. It may have a wide application after miniaturization and standard packaging.