Sensing of Dynamic Light-Liquid Interaction with Dual Beam Thermal Lens Spectroscopy

Here we show dynamic wave-front sensing as a temperature-induced index of refraction changes for thermalization processes in liquids. Light-liquid interaction is analyzed with the help of visible image changes of a diffraction patterns response. The images were analyzed for studying dynamic of thermophysical properties of organic compounds using a pump-probe thermal lens spectroscopic system. The optical system is a dual femtosecond pulsed laser, using infrared as a pump and probing with visible light. The colinear infrared and visible light beams were focused on the cell of colorless liquids. The transmission of the visible light of the probe exhibited divergence, producing a ring pattern projected onto a screen and captured with a digital camera. The technique reported here allowed us to observe well-defined diffraction patterns from water, colorless organic compounds, and binary mixtures. Visibility and the number of rings depended on the laser power, dimensions of the cell, free convection, initial temperature conditions, and the light absorption of the liquid material.