pISSN 0374-4914 eISSN 2289-0041

## Research Paper

New Physics: Sae Mulli 2015; 65: 757-762

Published online August 31, 2015 https://doi.org/10.3938/NPSM.65.757

## Measurement of the Thermal Lens Effect in Liquid Samples

Hyunki KIM, Jaeran LEE, Sok Won KIM*

Department of Physics, University of Ulsan, Ulsan 680-749, Korea

Correspondence to:sokkim@ulsan.ac.kr

Received: April 30, 2015; Revised: June 8, 2015; Accepted: June 12, 2015

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

### Abstract

When a high-power laser beam is focused into an absorbing medium, the medium is locally expanded. The phenomenon of the changing angle of convergence and divergence according to changes in the refraction of light caused by the variation in the density in the expanded region is called the thermal lens effect. The measurement methods for the thermal lens effect can be divided into a single-beam method and a dual-beam method that uses pump and probe beams. In this study, the thermal lens effect in liquids such as ethanol and methanol was measured by using a single-beam method. A Nd:YVO$_{4}$ laser beam was used as the light source, and the intensity variation of the beam transmitted through the cell that contained liquid samples was measured by using several lenses with different focal lengths as the cell was moved $\pm$3.0 cm from the focal point. The result showed that the thermal lens effect was clearly produced in ethanol and methanol that the effects for both liquids were quite similar.

Keywords: Thermal lens, Thermal expansion, Z-scan