Method of measurement of thickness of uniaxial anisotropic crystals and thermal control of Bessel beam transformation

We propose a method of polarization-based measurement of thickness and birefringence of uniaxial crystal X-cuts, which consists in measuring the spectral transmittance of a "polarizer-crystal-analyzer" structure. With use of X-cuts of a congruent lithium niobate with a nominal thickness of 1.052 mm, the validity of the method is experimentally confirmed and recommendations on its practical use are made. A possibility to control the Bessel beam conversion in CaCO$_3$ crystal via changing its thickness is shown. The controlled conversion of a zero-order Bessel beam into a second-order vortex Bessel beam due to effect of the thermal linear expansion of a crystal by heating is experimentally investigated.