There is generally an important performance gap between theoretical and experimental results of optical designs. In theoretical results, all factors seem to be perfect but experimental results are highly affected from real factors such as production criteria, atmospheric conditions, experimental environment etc. Therefore, a certain number of practical tests have to be done in field in order to change parameters to compensate for these factors. In case of laser optical designs, some specific tests are done in order to make the needed laser spot size which is achieved in analysis software to the practical spot size. Generally, manual inspection of the spot after each test by an expert or complex spot analysis tools are required. However, these methods are generally over-complex for simple spot size calculations. In this work, we propose a method to inspect and measure laser spot size on a material remotely using a camera and an analysis software we developed. Using the proposed image processing pipeline in the software, the laser spot image on the material is captured from the camera and processed in order to give a final spot size value in pixels. This method provides an easy, flexible and effective spot size calculation and experimental comparison. In addition, our work includes a comparison of two different processing techniques for calculating spot size. Using our proposed method, we got fast and accurate practical results in comparison with tests which are done using manual inspection or expensive tools.
This paper presents the effects of M2 (M square) factor of the laser source on steel materials in terms of spot size, duration of exposure and power density. Generally, laser sources are modelled as a Gaussian beam. M2 factor is known as the beam quality factor and it represents the degree of variation of a laser beam from an ideal Gaussian beam. It determines how well a laser beam will focus or diverge. According to ISO 11146-1, M2 is defined as BPP (Beam Parameter Product) divided by λ/π. It is also related to beam waist and divergence angle. A perfect beam would be a single mode TEM00 laser beam. Single mode fibers have smaller core diameter. It means that it can focus more easily than multi mode fiber laser can. In this study damage effects of CW lasers, which have 1070 nm wavelength, on 1 mm thick steel target plate are examined. Effects of using two different M2 values at different output powers are investigated experimentally and the results are discussed. These results will help compare the theory with experimental results.
This paper presents the effect of laser ablation parameters on optical limiting properties of silver nanoparticles. The current applications of lasers such as range finding, guidance, detection, illumination and designation have increased the potential of damaging optical imaging systems or eyes temporary or permanently. The applications of lasers introduce risks for sensors or eyes, when laser power is higher than damage threshold of the detection system. There are some ways to protect these systems such as neutral density (nd) filters, shutters, etc. However, these limiters reduce the total amount of light that gets into the system. Also, response time of these limiters may not be fast enough to prevent damage and cause precipitation in performance due to deprivation of transmission or contrast. Therefore, optical limiting filters are needed that is transparent for low laser intensities and limit or block the high laser intensities. Metal nanoparticles are good candidates for such optical limiting filters for ns pulsed lasers or CW lasers due to their high damage thresholds. In this study we investigated the optical limiting performances of silver nanoparticles produced by laser ablation technique. A high purity silver target immersed in pure water was ablated with a Nd:YAG nanosecond laser at 532 nm. The effect of altering laser power and ablation time on laser ablation efficiency of nanoparticles was investigated experimentally and optimum values were specified. Open aperture Zscan experiment was used to investigate the effect of laser ablation parameters on the optical limiting performances of silver nanoparticles in pure water. It was found that longer ablation time decreases the optical limiting threshold. These results are useful for silver nanoparticles solutions to obtain high performance optical limiters.