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Transient ionizing radiation fields have been observed to cause substantial optical loss in undoped LiNbO3 crystals operating at 1.06 microns. This loss is slow to recover and makes the selection of this material for Q-switch applications in radiation environments unfeasible. We have studied the effects of Mg doping on the radiation response of LiNbO3 crystals and have investigated the optical luminescence of doped and undoped samples. Our results indicate a strong correlation between crystal defects, formed primarily during crystal growth, and the radiation-induced optical loss exhibited by these materials. These findings have enabled us to produce radiation-hard LiNbO3 crystals for use in high gamma-field environments.

Injection of high power, multi-mode laser profiles into a fiber optic delivery system requires controlling a number of injection parameters to maximize throughput and minimize concerns for optical damage both at the entrance and exit faces of the fiber optic. A simple method for simultaneously achieving a compact fiber injection geometry and control of these injection parameters, independent of the input source characteristics, is provided by a refractive lenslet array and simple injection lens configuration. Design criteria together with analytical and experimental results for the refractive lenslet array and short focal length injection lens are presented. This arrangement provides a uniform spatial intensity distribution at the fiber injection plane to a large degree independent of the source mode structure, spatial profile, divergence, size, and/or alignment to the injection system. This technique has application to a number of laser systems where uniform illumination of a target or remote delivery of high peak power is desired.

Industrial, military, medical, and research and development applications of lasers frequently require a beam with a specified irradiance distribution in some plane. A common requirement is a laser profile that is uniform over some cross-section. Such applications include laser/material processing, laser material interaction studies, fiber injection systems, optical data image processing, lithography, medical applications, and military applications. Laser beam shaping techniques can be divided into three areas: apertured beams, field mappers, and multi-aperture beam integrators. An uncertainty relation exists for laser beam shaping that puts constraints on system design. In this paper the authors review the basics of laser beam shaping and present applications and limitations of various techniques.

It has been demonstrated that x rays alone can be used to pump a 1061 nm Cr,Nd:GSGG laser. Lasing action has been observed when the laser rod absorbs greater than 27 krad of 2 MeV x rays. The laser cavity consists of a corner cube and an output mirror with a reflectivity of 67%. The x rays are delivered in a 20 ns pulse, and laser action is observed several microseconds after the x ray pulse. This delay suggests that chromium is important in the laser pumping process since it is known that an excited chromium ion takes about 10 microseconds to transfer its energy to a neodymium ion.

It has been demonstrated that X-rays alone can be used to pump a 1,061 nm Cr,Nd:GSGG laser. Lasing action has been observed when the laser rod absorbs greater than 27 krad of 2 MeV X-rays. The laser cavity consists of a corner cube and a output mirror with a reflectivity of 67%. The X-rays are delivered in a 20 ns pulse, and laser action is observed several {micro}s after the X-ray pulse. This delay suggests that chromium is important in the laser pumping process since it is known that an excited chromium ion takes about 10 {micro}s to transfer its energy to a neodymium ion.