Experimental study of the laser-induced absorption effect and the nature of color centers in potassium titanyl phosphate crystal

Abstract

We present the results of the experimental study of laser-induced absorption (LIA) in KTiOPO4 crystal (KTP) under the action of laser radiation of wavelengths 0.37-0.44, 0.53, and 0.68-0.88 /m. Nw data are obtamed on the nature of the colour centers in KTP. The relationship is established between the LIA effect and laser damage threshold of the crystals. The influence is outlined of the LIA effect on the process of frequency doubling in KTP crystal.

Optical studies of laser-induced gray-tracking in KTP

“…The gray-tracking susceptibility is greater when the 532-nm beam polarization is parallel to the axis. This result corroborates previous measurements performed with a probe beam at 532 nm [6] and with white light [9]. Furthermore, our work indicates that this effect is higher for than for .…”

“…Gray-tracking induced by a laser is classically studied on the basis of several types of experiments: visual observation of the darkening, observation of second-harmonic beam distortion during 1064-nm SHG [3], [4], optical transmission coefficient measurement by the beam which creates the damage [6] or by a probe beam during laser exposure [1], [2], [7], optical transmission or absorption spectra [2], [8]- [11], and electronspin-resonance (ESR) spectra [6], [8] measured before and after laser irradiation. From these experiments, some properties of the laser-induced gray-tracking have been determined: damage leads to a decrease in optical transmission over the entire visible range from 400 to 700 nm [2], [9], [11] with a magnitude which is a nonlinear function of the intensity of the laser beam creating the damage [2], [12]; the graytracking threshold, expressed as the laser peak intensity above which the damage is observed, is a decreasing exponential function of the -switch frequency [4]; a laser beam with a polarization parallel to the polar axis of KTP, i.e., the binary axis ( ), creates more damage than a beam polarized orthogonally to the axis [6], [9]; the time constant, usually a few minutes at room temperature, is dependent on the intensity of the laser beam until the level of gray-tracking reaches the Manuscript received July 6, 1998;revised November 6, 1998 asymptotic value [6], [7], [10], [12]. After the termination of laser exposure, the relaxation of the damage depends on the focusing conditions of the exposure beam, usually more than one year for strong focusing [4] and few hours for weak focusing [12] at room temperature.…”

Review on Gray Track Effects on Potassium Titanyl Phosphate Single Crystals

“…Focus of many investigators is to recover the KTP from gray tracking to produce assured product for industrial use, To do so the core cause of gray track should be known, though various susceptibility is feasible, general believe is that defects that trap photo induced electron and holes is the primary engender, the defect mentioned is trapping sites, Optical absorption and electron paramagnetic resonance [EPR] studies can be opted to identify the trapping sites. Few investigators worked on in it namely Roelofs [4] described four distinct Ti 3+ through EPR Spectral study in electrically induced or annealing in a hydrogen atmosphere in flux grown crystal, flowingly Andreev and Asimov found the same effect in X-ray irradiation at room temperature also Andreev [5] demonstrated the same using Laser beam. Likely the application themselves efficient to produce trapping sites.…”

Site selective substitution Pt for Ti in KTiOPO4:Ga crystals revealed by electron paramagnetic resonance

“…32 one Pt 3þ center, Pt(A), and two Pt þ centers, Pt(B) and Pt(C), were described in details. 36 It was found also that EPR signal depends on kind of irradiation (light, x-and c-rays), as well as on growth technique.…”