Entity

Time filter

Source Type


Panahibakhsh S.,Amirkabir University of Technology | Panahibakhsh S.,Laser and Optics Research Institute | Jelvani S.,Laser and Optics Research Institute | Maleki M.H.,Laser and Optics Research Institute | And 2 more authors.
Optics and Lasers in Engineering | Year: 2014

This paper presents the effect of XeCl laser irradiation on Nd:YAG single crystal samples with various number of pulses at different repetition rates and laser fluences. Effects of the irradiation on the optical and structural properties of the crystal are analyzed by UV-vis-NIR spectroscopy. Annihilation of some point defects of the crystal structure is observed following laser irradiation at a fluence of 100 mJ cm-2 with 100 and 500 pulses. Increasing the laser fluence and pulse numbers leads to saturation and new defects are found to be formed in the crystal. Additional absorption spectra of the irradiated samples show that oxygen vacancies in the Nd:YAG crystals are removed during the low-dose irradiation. The laser irradiation is compared to the thermal annealing process for Nd:YAG crystal modification. Additional absorption spectrum of an annealed sample reveals that induced negative absorption band at 236 nm is correlated with the annihilation of the oxygen vacancy center. Our results also demonstrate that XeCl laser treatment has several advantages upon annealing at high temperatures in the Nd:YAG crystal quality improvement. Thus, the present work can give a new approach to modify Nd:YAG crystals to be used in a wide variety of solid-state laser engineering. © 2014 Elsevier Ltd. Source


Panahibakhsh S.,Laser and Optics Research Institute | Panahibakhsh S.,Amirkabir University of Technology | Jelvani S.,Laser and Optics Research Institute | Maleki M.H.,Laser and Optics Research Institute | And 2 more authors.
Optical and Quantum Electronics | Year: 2015

A thin disc Nd:YAG crystal sample was irradiated with 500 pulses of XeCl laser (Formula presented.) at (Formula presented.) laser fluence and 25 Hz repetition rate. The UV–Vis–NIR and additional absorption spectra of the sample showed that optical transmission of the Nd:YAG crystal increased in ultraviolet and visible regions due to elimination of some oxygen vacancies of the crystal following the irradiation. Increase in laser damage threshold of the Nd:YAG crystal sample subsequent to annihilation of oxygen vacancies was obtained by the laser damage threshold experiment. The laser damage thresholds of the irradiated and un-irradiated crystals were measured using 30 ns, 1,064 nm single longitudinal mode, TEM00 pulses of a passively Q-switched Nd:YAG laser. The laser damage threshold of the irradiated crystal (after dividing by √3 to scale for pulse duration of 10 ns) was obtained to be (Formula presented.). It is nearly five times as high as that of un-irradiated Nd:YAG crystal, which was found to be (Formula presented.). © 2014, Springer Science+Business Media New York. Source


Panahibakhsh S.,Laser and Optics Research Institute | Panahibakhsh S.,Amirkabir University of Technology | Jelvani S.,Laser and Optics Research Institute | Maleki M.H.,Laser and Optics Research Institute | And 2 more authors.
European Physical Journal Plus | Year: 2014

A Nd:YAG crystal sample was irradiated by 200 pulses of ArF excimer laser at 35mJ/cm^2 laser fluence and 1Hz repetition rate. The optical absorption of the Nd:YAG crystal was decreased in the whole spectral range of the ultraviolet visible near-infrared region after ArF laser irradiation and some oxygen vacancies of the Nd:YAG crystal were removed according to its additional absorption spectrum. A laser-induced damage threshold (LIDT) measurement of the ArF laser treated crystal was performed by linearly polarized 30ns, 1064nm single longitudinal mode, TEM00 laser pulses. The LIDT of the ArF-laser-irradiated crystal was found to be 302±35 J/cm^2, about three times higher than the LIDT of the unirradiated crystal. Thus, the laser-treated Nd:YAG crystal is preferred to apply as the laser amplifier medium, due to the possibility of further laser amplification caused by the higher damage threshold of the amplifier medium. © 2014, Società Italiana di Fisica and Springer-Verlag Berlin Heidelberg. Source


Bananej A.,Laser and Optics Research Institute | Bananej A.,K. N. Toosi University of Technology | Hassanpour A.,K. N. Toosi University of Technology | Razzaghi H.,Laser and Optics Research Institute | And 2 more authors.
Optics and Laser Technology | Year: 2010

Monolayer ZrO2 and TiO2 films were prepared on BK7 glass by physical vapor deposition (PVD) and were subsequently annealed for 1 h at 300 °C. By using the transmission spectra of two samples and the envelope method, the refractive index dispersion and extinction coefficients have been calculated. Laser induced damage threshold (LIDT) measurement shows that despite slight differences between the extinction coefficients of the two samples, the LIDT parameter of the ZrO2 film is greater than that of the TiO 2 film. This fact leads us to consider thermal conductivity as an important parameter for interpreting the LIDT difference. According to our theoretical analysis, as a consequence of increase in the number of thermal barriers along poorer film, its thermal conductivity, and hence LIDT, decreased, which is in agreement with our experimental results. The measured porosity of the two samples shows higher porosity for TiO2 single layer, which is in agreement with atomic force (AFM) images. The gradual and smooth damage morphology of ZrO2 observed in optical images implies higher thermal conductivity than TiO2. © 2010 Elsevier Ltd. All rights reserved. Source

Discover hidden collaborations