Analysis of the thermal lens effect induced by a vector flat-top beam

In this work, we present a theoretical model describing the temperature and refractive index variation profiles induced in a medium excited by a vector flat-top beam, generated through the incoherent superposition of the fundamental Gaussian mode (LG 00 ) and the annular mode (LG 01 ). This composite beam profile is compared to the individual contributions of the LG 00 and LG 01 modes. The analysis highlights the influence of the spatial intensity distribution on the thermal and optical response of the medium, particularly on the radial gradient of the refractive index. The results show that the vector flat-top beam induces a more uniform refractive index variation in the central region, with a moderate but spatially extended radial gradient; effectively combining key advantages of both Gaussian and annular profiles. Compared to pure LG 00 and LG 01 beams, this configuration offers improved control of the thermal lens effect and may improve sensitivity in photothermal detection systems, while providing better spatial stability.