Tunable External Cavity Laser With a Liquid-Crystal Subwavelength Resonant Grating Filter as Wavelength-Selective Mirror

We demonstrate a tunable external cavity laser consisting of a voltage-tuned liquid-crystal cladded subwavelength resonant grating filter placed directly in front of a semiconductor laser gain chip. The filter acts as a tunable wavelength-selective mirror. As the applied voltage to the filter changes from 0 to 22 V, the laser wavelength demonstrates a tuning range of 7 nm, which may be further increased. As the laser has simple cavity design and no moving parts, it can be low cost and easy to fabricate and assemble.