Adaptive compensation of thermally induced aberrations in Faraday isolator by means of a DKDP crystal

摘要

In this paper we describe adaptive compensation of thermal lens in a Faraday isolator using a DKDP crystal. Thermal lens measurements were made with a modification of the Hartmann sensor - a 2D scanning Hartmann sensor. This device proved to be convenient and adequate for thermal lens measurements. Our experiments showed that a DKDP crystal does not influence the isolation ratio of Faraday isolator and efficiently compensates thermal lens. The negative effect produced by the thermal lens is estimated as the quantity of power losses from the original beam mode (Gaussian mode in our experiments). Without compensation the losses were measured to be about 5% for 50W of radiation power and were compensated to less than 1% by a negative thermal lens in a few millimeters thick DKDP crystal. Numerical extrapolation of experimental data to a higher powers range showed that for the power up to 200W, power losses can be made less than 5%.