Thermal lensing characterization of a high-radiance 946nm planar waveguide laser

Abstract

Abstract:We present the characterization of the in-plane thermal lens in a quasi-four-level Nd:YAG planar waveguide (PW) laser configured for high-radiance operation with an external stable-cavity. Our approach utilises the measurement of the laser's output irradiance distribution at the near-and far-field positions concurrently in order to obtain the "real time" beam propagation parameter and thus beam quality factor, M 2 . Coupled with the knowledge of the intra-cavity-thermallens-dependent beam sizes at an intra-cavity beam waist, the power dependent effective thermal lens focal length was characterized. A thermal lens focal length of >450 mm was obtained at all incident pump powers up to the maximum level of 87 W. This characterization enabled the build of a 29 W 946 nm PW laser with a record output radiance of 4.3 TWm -2 sr -1 .