External cavity tunability of some NIR semiconductor lasers

In this paper, tunability of four near-infrared semiconductor lasers which typically lase at 783nm, 808 nm, 892 nm and 980 nm is studied. Both Littrow (wavelength dependent beam direction setup) and Littman (wavelength independent beam direction setup) configurations have been used for single mode tuning. In addition, the tunability of 783 nm laser in dual mode tuning is studied in both Littrow and Litman configurations. The wavelength and the power of the output beam of the laser have been measured. In all four cases, Littrow configuration shows a little better tuning range. In both Littrow and Littman configurations, the wavelengths near the main wavelength of the laser had more power. The highest achieved power of these lasers in the Littrow setup was more than that of the Littman setup. Moreover, the tuning speed and effect of tuning on the bandwidth of the laser were investigated.