5TH International Congress on Technology - Engineering & Science - Kuala Lumpur - Malaysia (2018-02-01)

Study On The Photomechanical Effects Caused By Short Pulse Width Lasers

Introduction: Studies have shown that when a laser is irradiated to a medium, it is accompanied by mechanical action as well as heat [1,2]. In the case of low laser intensity and long exposure time, photochemical, photothermal stimulation occurs, and at higher laser intensities and short exposure times, photomechanical effects such as plasma phenomena occur. In order to obtain a photomechanical effect without damaging the medium by laser energy, a pulsed laser with short irradiation time (ms~ns) is required. For this, a pulsed laser with short irradiation time (Brilliant b, Quantel) was used to conduct the study on photomechanical effect detection. Methods: Figure 1 is a conceptual diagram of the setup used in the experiment. The laser used in the experiment was an Nd:YAG laser with a wavelength of 1064 nm, and the frequency was doubled and the green wavelength of 532 nm was used. An artificial composite (collagen film) was used as a medium to induce the photomechanical effect and an in vitro experiment was performed. A piezo sensor was attached to the back of the artificial composite and fixed to a 3-axis translate stage equipped with a micrometer, and for the output of the sensor during pulsed laser irradiation, the size of signal was analyzed by storing it on PC using A/D board. The baseline was determined based on the data before laser irradiation and peak detection (baseline to negative peak max) was performed. Results & Conclusion: The piezo sensor has a property of outputting an output signal according to the degree of deformation due to a physical change due to an external force. Figure 2 shows the result of measuring the photomechanical effect by adjusting the thickness of the artificial composite by 4 stages and varying the power of the laser 6 steps (0.01W, 0.05W, 0.07W, 0.1W, 0.12W, 0.15W). As the thickness of the artificial composite increased, the sensor output signal decreased and the sensor output signal increased as the laser power increased. In other words, the photomechanical effect induced by the laser could be measured by using the piezo sensor, and the effect of the change of the medium thickness and the laser power was detected. In the future, it is planned to perform studies on the mechanical effects of laser pulse width variation which could not be detected due to the functional limitations of the laser.
Han-Byeol OH, Ji-Sun KIM, Jin-Young BAEK, Jae-Hoon JUN