Narrow bandwidth spectral beam combining of cm bar in a short external resonator based on rhombic prism combinations

Abstract

A novel narrow bandwidth spectral beam combining structure of cm bar with a short external resonator based on rhombic prism combinations is proposed and demonstrated. A pair of rhombic prism combinations are employed between the LDA and the transform lens in the external resonator, which consists of a rectangular quartz plate in the middle and two quartz rhombic prisms on either side in opposite orientations in each combination. The beam emitted from a standard cm bar is segmented and rearranged, and spectral beam combining is carried out along the slow axis. A spectral bandwidth of about 5.46 nm is obtained by employing a transform lens with a short focal length of 150 mm, which is only about 1/3 of that of the conventional spectral beam combining, and a narrow spectral bandwidth of 1.14 nm is obtained when a 5x de-magnifying telescope is employed in the above external resonator, the distance between LDA and diffraction grating is 500 mm while that between LDA and output coupler is 650 mm. This novel structure provides a compact external resonator scheme for narrow bandwidth spectral beam combining.