High power or miniaturized laser systems are limited by the laser damage resistance of optical components, particularly
of nonlinear crystals. The laser damage of optical components depends on many factors such as wavelength, frequency,
pulse duration, spot-size,... Moreover, in nonlinear crystals, the anisotropy of physical parameters may cause anisotropy
of the Laser Induced Damage Threshold (LIDT). Thus, the LIDT may depend on polarization or propagation direction of
the laser beam. The aim of this paper is to discuss the laser damage results of two nonlinear crystals: KTiOPO4 (KTP)
and RbTiOPO4 (RTP). In general, due to its higher effective electro-optic coefficients, RTP is more used for electrooptic
applications, whereas KTP is popular for second harmonic generation. Laser damage tests in KTP and RTP reveal
that for both crystals the LIDT depends on the polarization. The laser damage tests were carried out at 1064nm with a
nanosecond Nd:YAG laser. The tests were performed with the polarization and the propagation direction of the light
along a principal crystal axis, and all configurations were tested with a parallel beam (waist diameter 75μm). As they
belong to the same crystal family, RTP and KTP crystals have similar nonlinear optical properties. This work also
reveals that the laser resistance of KTP and RTP is very close. Functional laser damage tests of RTP for Pockels cell
applications and SHG-cut KTP were performed too. We also discuss the influence of second harmonic generation on the
LIDT.
The laser damage probability of nonlinear optical crystals depends on many different factors. In addition to the fabrication process (crystal growth, cutting, polishing, coating) the damage threshold of non-linear crystals is influenced by the usage of the crystal. The anisotropy of material properties like the complex refractive index, the mechanical yield strength and the polarizability may cause anisotropy of the Laser Induced Damage Threshold (LIDT). The LIDT may depend on the propagation direction or the polarization of the light. Anisotropy in the LIDT has in fact been observed in different crystals. The dependency of the KDP-LIDT on the propagation direction and its independence on the polarization direction reported by Burnham et al. is an example that is not yet fully understood. For KTP it has been evidenced by Hu et al. that the grey-tracking threshold is polarization dependent. In this contribution we discuss the bulk laser damage resistance of two isomorphous non-linear crystals: KTiOPO4 (KTP) and RbTiOPO4 (RTP). All tests are performed using a nanosecond laser at 1064nm wavelength. For both crystals all polarization and propagation directions parallel to the principal axes have been tested. In addition we investigated two typical devices: two types of Pockels cells in RTP and a SHG-cut crystal in KTP. The results are analyzed on the basis of an anisotropic sensitivity of the crystal to the electric field and the efficiency of second harmonic generation.
Lasers for space applications require miniaturized high power components that can be operated at low voltages.
RbTiOPO4 (RTP) is a highly efficient electro-optical material, which is used in particular for the realization of low
voltage and high repetition rate Pockels cells. RTP can be operated in two crystal orientations (x-cut and y-cut). In both
cases, the incoming linear polarization is oriented at 45o to the z-direction. In this study, laser damage is investigated in
RTP crystals. More precisely, we focus on the correlation between the laser damage characteristics and the used crystal
orientation. The laser damage tests were carried out at 1064 nm with a standard 6 ns Q-switched Nd:YAG laser and the
polarization was oriented as for Pockels cell operation at 45o to the z-axis of the crystals. This work reveals that the
Laser Induced Damage Threshold (LIDT) is two times higher for x-cut than for y-cut RTP crystals. Reflection and
transmission measurements show that this LIDT anisotropy can not be explained by an evident loss mechanism like
Stimulated Raman Scattering (SRS).
The aim of this work is to introduce the RTP material and point out its main fields of application for solid-state lasers, both in non-linear optics and electro-optics. The paper reviews the performance of the RTP crystals for visible and infrared frequency conversion. This review ends by covering the properties of RTP for electro-optics.
The aim of this work is to introduce the RTP material (a KTP isomorph) and point out its main fields of application for solid-state lasers, both in non-linear optics and electro-optics.
In order to cover all the range of applications in which RTP can be used, the paper reviews the performance (efficiency, tolerance, walk-off, damage threshold) of the RTP crystals as frequency-doubling crystals (Second Harmonic Generation) for green and yellow lasers. In addition, red output was obtained with RTP in a frequency-mixing experiment, and an OPO (Optical Parametric Oscillation) pumped at 1064nm yielded an eye-safe wavelength at 1.62 μm.
For both operations, we present data related to RTP's optical and physical properties as well as comparison with other suitable non linear crystals. With the help of the Photothermal Common-path Interferometer (a technique developed in order to measure very precisely all kinds of absorption), we give an assessment of RTP's sensitiveness to green-induced absorption ("grey-track").
This review ends by covering the properties of RTP for electro-optics. We present a complete study based on measurements in house and comparative data of other non linear crystals available on the market.
The aim of this survey is to compare the performance of different nonlinear crystals used as optical parametric oscillator material when pumped at 1064nm with short pulse and low repetition rate Nd:YAG laser. Signal and Idler wavelengths have been monitored and slope efficiency viewgraphs as well as other relevant parameters displayed. Some experiments with KTP used as monolithic OPO have been performed and discussed in this paper.
The walkoff-compensated (WOC) twin-crystal device enables to reduce the aperture effects in critically phase-matched parametric generation. In that device, instead of using a monolithic bulk crystal of length 21c, two identically-cut crystals of length lc are disposed in tandem such that the relative sign of the walkoff angle (rho) in the first and second items are opposite, while keeping unchanged the relative sign of their non-linear effective susceptibilities through a proper orientation of their optic axes. Applied to KTiOPO4 (KTP) for type-II (oeo) second-harmonic generation (SHG) of a color center laser, the 2 X lc twin- crystal device leads to a conversion efficiency 3.5 times higher than that of a 21c single bulk crystal. The same WOC technique has been applied successfully in the type-I (ooe) SHG of a CO2 laser using an AgGaSe2 (AGSE) device. The extension of the WOC method to a periodical structure composed of N twin-device stacks is considered. We report the first demonstration of the SHG efficiency enhancement of such a structure, which is made of four KTP plate optically contacted in the WOC configuration.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.