Littrow-type external-cavity diode laser with a triangular prism for suppression of the lateral shift of output beam

We demonstrate a Littrow-type external-cavity diode laser with an additional triangular prism united to a diffraction grating. In this configuration, while the laser wavelength can be tuned by rotating the grating that constitutes an external cavity, the prism outside the cavity compensates for the lateral shift of the output beam. It is estimated that the lateral shift of the output beam is only 2 μm over the tuning range of 12.91 nm. In fact, the output beam was coupled into a single-mode fiber with constant efficiency over the wavelength range without any adjustment of the coupling optics.