Tunable external-cavity semiconductor laser using monolithically integrated tapered amplifier and grating coupler for collimation

A novel lensless tunable external-cavity laser using monolithically integra ted tapered amplifier, grating coupler (GC) and an external half mirror is proposed and demonstrated in this letter, It can be fabricated by a simple process and emits a collimated output beam. By making use of wavelength dis persion of the GC, the lasing wavelength can be angle tuned, Wavelength tun ing over a wide range of 21.5 nm by 4.5 degrees device rotation and an 84-m W output power were achieved under continuous-wave operation, A well-collim ated output beam with a divergence angle as small as 0.3 degrees was mainta ined over the entire tuning range.