External-cavity tunable mid-infrared laser using off-band surface- emitting Bragg grating coupler

An external-cavity laser using an integrated two-segment design allows broad and continuous wavelength tuning with independent control of power and wavelength. The laser has a gain segment and a surface-emitting Bragg grating segment that was designed to be off-band for zero reflection inside the cavity, and with a strong free-space coupling to an external mirror to form a linear cavity. Wavelength control was achieved with a combination of coarse and broad wavelength tuning (140 nm) with the external mirror, and continuous, fine wavelength tuning via current- induced phase shift in the Bragg grating. Separate controls of the two segments allowed wavelength fine tuning without power variation and vice versa. The concept was applied to a 7 µm laser, and is applicable to other wavelength. ©2005 American Institute of Physics