Many industrial applications require a different wavelength than the fundamental output from commercially available lasers. Nonlinear optical devices, such as harmonic generators, convert near-infrared output wavelength, thus providing radiation in the visible and ultraviolet spectrum. In the present paper most attention has been concentrated on the beam characteristics of the fundamental and second-harmonic radiations. We have compared the focusability of laser beams at the fundamental and second-harmonic wavelengths.
The behavior of an electrooptic Q-switch in a high-average-power lsaer is presented. The linear optical absorption of laser radiation produces thermal gradient and consequent thermally-induced birefringence in the electrooptic crystal which disturbs Pockels cell performance. Depolarization losses of the resonator caused by thermally-induced birefringence in the KD*P crystals are experimentally measured.
This paper describes the development and performance of an optical parametric oscillator based on KTP crystal and pumped by a flashlamp-pumped Q-switched Nd:YAG laser at 1.064 micrometers . The effect of an optical resonator configuration on OPO performance has been investigated experimentally. A comparison between plane-parallel, stable and unstable resonators in both energy conversion and output beam divergence was also performed and the results are discussed. In summary, we have demonstrated a compact low threshold source for the near IR in a configuration of an intracavity optical parametric oscillator based on the noncritically phase-matched KTP crystal placed inside the resonator of a multi-transverse-mode Nd:YAG laser. The 1.57 micrometers output energy of 40 mJ was achieved with a stable, short cavity KTP OPO. The overall efficiency of 0.55 percent was obtained from operating approximately 2 times above oscillation threshold. The dependence of output pulse energy on flashlamp input energy was not changed within the range of 5-50 Hz.
The radiation at around 1.5 micrometer has been extensively investigated over the last few years for eye-safe applications. This paper describes the development and performance of a pulsed solid-state laser based on nonlinear frequency conversion of the Nd:KGd(WO4)2 fundamental radiation into the near-infrared region of the spectrum. Neodymium-doped potassium gadolinium tungstate Nd:KGd(WO4)2 (Nd:KGW) possesses a combination of spectral and lasing characteristics uniquely favorable for laser operation. The explanation for the high efficiency which can be achieved with this material follows from high effective stimulated- emission cross section of laser transition. Also, in contrast to Nd:YAG, Nd:KGW is an efficient Raman medium. In the present paper most attention has been concentrated on the self- conversion of the laser wavelength at 1.351 micrometer to the first Stokes line at 1.538 micrometer. In conclusion, we have demonstrated a compact low-threshold source for the near-IR in configuration of an intra-cavity solid-state Raman laser based on a flashlamp-pumped Nd:KGW laser crystal. The small size and high efficiency of this laser makes it an attractive source for a large number of applications such as communications and optical atmospheric studies.
The radiation at around 1.5 micrometers has been extensively investigated over the last few years for eye-safe applications. This paper describes the development and performance of a pulsed solid-state laser based on nonlinear frequency conversion of the Nd:KGd(WO4)2 fundamental radiation into the near-infrared region of the spectrum. Neodymium-doped potassium gadolinium tungstate Nd:KGd(WO4)2 (Nd:KGW) possesses a combination of spectral and lasing characteristics uniquely favorable for laser operation. The explanation for the high efficiency which can be achieved with this material follows from high effective stimulated-emission cross section of laser transition. Also, in contrast to Nd:YAG, Nd:KGW is an efficient Raman medium. In the present paper most attention has been concentrated on the self-conversion of the laser wavelength at 1.351 micrometers to the first Stokes line at 1.538 micrometers . In conclusion, we have demonstrated a compact low-threshold source for the near-IR in a configuration of an intra-cavity solid-state Raman laser based on a flashlamp-pumped Nd:KGW laser crystal. The small size and high efficiency of this laser makes it an attractive source for a large number of applications such as communications and optical atmospheric studies.
The behavior of an electro-optic Q-switch in high-average- power laser is presented. Absorption of laser radiation produces heating of the electrooptic crystal which degrades the laser performance. A large increase in output energy stability is achieved by employing a switching voltage pulse of the special temporal shape to the Pockels cell. The optimum pulse waveform has been calculated to reduce the Q- switching intracavity loss to zero at the instant a laser pulse occurs. We have compared the laser performance with the conventional rectangular pulse shape and the calculated one. The experiments have demonstrated that at the novel shape of pulse the permissible temperature range of the laser performance without adjustment of switching voltage was extended by a factor of 2 - 2.5.
The results of investigation and development method for multi-cascade pulsed solid-state lasers optical schemes are represented. The analysis of processes for lasers with active and passive Q-switch was made. It is shown the variation of output laser parameters versus the inter- cascade coupling.
The model LT-4Z electro-optical Q-switched flashlamp-pumped Nd:YAG laser is designed for hydrospheric studies. The laser generates a pulse of light in the blue-green region of the visible spectrum (532 nm), where the absorption of sea water is minimized, at pulse repetition rate of 100 - 500 Hz. This model is especially optimized for operation in airborne hydrography system. In this paper we describe the performance of a laser for complex airborne system which requires the conflicting specifications of high efficiency, small size, short pulsewidth, and high average power.
A novel laser cavity design was proposed to compensate for thermally induced stress birefringence in cylindrical laser rods. The use of this optical schematic of the cavity allows lasers to operate efficiently at high average power levels. Experimentally a Nd:YAG oscillator has been operated in an electro-optically Q-switched mode giving 55 mJ linearly polarized output pulses at a pulse repetition rate of 500 Hz. Other features of the laser design include the ability to produce second and third harmonics with high efficiency.
Currently flashlamp-pumped Nd:YAG lasers operate at a pulse repetition rate of 10...50 Hz. However, some applications call for increasing pulse repetition rate up to 300...500 Hz. Lasers with high repetition rates may be of practical interest to use in hydrography, lidars, locators, and bathimetric systems. We present the design and the performance of a compact high repetition-rate Nd:YAG oscillator pumped by single flashlamp in electro-optical Q- switched operation with second harmonic generation (SHG).
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