S.J. Barrington

Photosensitivity of lead germanate glass waveguides grown by pulsed laser deposition.

We report very large photoinduced refractive-index changes Dn, of the order of ~10(2), in lead germanate glass waveguides grown by pulsed-laser deposition. The magnitude of Dn was derived from measurements of diffraction efficiency for gratings written by exposure to 244-nm light through a phase mask, whereas the sign of Dn was determined from ellipsometric data. Results are shown for films grown under oxygen pressures ranging from 1 chi 10(-2) to 6 chi 10(-2)mbars (1.33mbars=1 Torr).

The effect of particulate density on performance of Nd:Gd3Ga5O12 waveguide lasers grown by pulsed laser deposition

We have successfully grown a range of waveguiding layers of Nd:Gd3Ga5O12 (Nd:GGG) on Y3Al5O12 by pulsed laser deposition for purposes of studying the effects of particulates on waveguiding and lasing performance. We have found that particulates have a detrimental effect on lasing threshold for the range of particulate densities studied, and can increase lasing thresholds from as low as 2.5 up to 167 mW. We have also shown that the detrimental effect of particulates in waveguides becomes less significant with increasing waveguide thickness.

Growth and characterization of pulsed laser deposited lead germanate glass optical waveguides

AbstractLead germanate thin films have been grown on BK7 and silica substrates, using pulsed excimer laser deposition(PLD) at wavelengths of 193 and 248 nm, from a bulk lead germanate target under various partial pressures of oxygen.The films produced vary in colour from brown, through clear, to yellow, and a parametric study has been undertaken ofthe film properties as a function of the growth conditions. The measured losses of the lead germanate films grown onglass substrates varied from ˘2.5 to 7 dB cm y1 depending on the oxygen partial pressure used. O 1999 Elsevier ScienceB.V. All rights reserved. 1. IntroductionPulsed laser deposition (PLD) has been exten-sively researched within the past decade as acomparatively fast, easy, and flexible technique forgrowing thin films of a wide range of materials [1].Amorphous, polycrystalline, and single crystallayers are routinely grown, depending on experi-mental parameters that include target composi-tion, substrate temperature, target–substratedistance, and the presence of an ambient gas, of-ten oxygen, at moderately low partial pressures.Recent successes in crystalline growth by PLDhave permitted the demonstration of e†cient la-sing action in 2–10 lm thick layers of gadoliniumgallium garnet, GGG, grown on YAG [2,3], andalso Ti:sapphire, grown on undoped sapphire [4].The losses reported in Ref. [3], of 0.3–0.5dB cm

Resolution considerations in electro-optic, single interface deflectors

We discuss the maximum theoretical resolution of a single interface, electro-optically controllable beam deflector in domain-engineered LiNbO3 and report on experimental results for implementation of devices optimized either for maximum resolution or for maximum deflection angle. For the resolution optimized device we observed approximately 50 resolvable spots for a +/- 1250-V range, which to our knowledge is a report of one of the highest ratios of resolution per volt from a solid-state electro-optic beam deflector.

Power scaling of continuous-wave adaptive gain-grating laser resonators

We demonstrate a power-scaling strategy in a continuous-wave adaptive phase-conjugate oscillator power amplifier (PCO-PA) system that actively corrects, via phase-conjugation, for thermally induced phase-distortions introduced by a power-amplifier (PA) placed in the output arm of the phase conjugate oscillator (PCO). Phase-conjugation is achieved by saturable gain four-wave mixing in a PCO Nd:YVO4 amplifier. Single-longitudinal mode phase-conjugate (PC) outputs of almost 11.5 W with an Mx2=1.4, My2=1.2 have so far been achieved with a PCO operating at 6 W PC output, a power gain of two through the PA. The saturable gain four-wave mixing that takes place in the PCO-PA system has been modelled and the results can be used to predict how best to proceed with further increasing the PC output power from such a system.

Photosensitive Lead Germanate Glass Waveguides Grown by Pulsed Laser Deposition

Photosensitivity in (predominantly) germanium doped fibres and planar waveguide structures is the subject of intense current interest. Permanent refractive index gratings, written using UV light from either pulsed or C.W. laser sources, can be produced by interferometric exposure, yielding Delta(n) values ranging from 10-5 to 10-3. Additional techniques such as hydrogen loading, or flame brushing, can further increase this value to ~10-2. In this paper, we report our studies of planar waveguides of lead germanate glass, grown by Pulsed Laser Deposition. The films are grown under various partial pressures of oxygen, and show distinct and systematic differences in colour, waveguide loss and photosensitivity. We interpret our results in the context of induced oxygen vacancies produced during the growth.

Domain-engineered lithium niobate as a medium for an integrated solid-state two-dimensional color laser scanning system.

A recently proposed alternative to conventional prism-type electro-optic solid-state deflectors is the single interface deflector. Whereas these deflectors are comparable in performance to prism-type deflectors, they are far simpler in construction. This simplicity obviously has the advantages that it reduces fabrication time and cost and allows for easier optimization. Less obviously, but more advantageously, the simplified geometry provides, for the first time to our knowledge, the ability to achieve a completely solid-state two-dimensional beam deflector. We also detail how the two-dimensional deflector can be further augmented by the addition of intensity and color switching to the device.

Electro-optic solid state beam deflection: resolution considerations and 2-D implementation

Here we analyze the achievable resolution for a single interface deflector. It can be seen that with a suitably sized device, significant resolution can be attained from a single interface deflector. This would be the first ever report to our knowledge of a 2D EO solid state beam deflector.

Power-scaling continuous-wave adaptive laser resonators

Summary from only given. Self-adaptive gain grating lasers have previously been demonstrated that can actively correct for thermally induced phase distortions. Here we discuss the power-scaling of such a resonator which operates at 6 W in its basic form. Our first attempts using a power amplifier in the output arm have lead to almost 12 W of single longitudinal mode output with a beam quality of M/sup 2/ = 1.3.

Efficient adaptive self-starting Nd:YVO/sub 4/ gain grating laser oscillator

Summary from only given. Self adaptive laser resonators based on laser induced gain gratings have successfully demonstrated correction of thermally induced aberrations in solid-state lasers. This technique has recently been shown to produce distortion corrected beams in a diode pumped, injected seeded system in Nd:YVO/sub 4/. This paper describes the first characterization of a fully self-starting, high power Nd:YVO/sub 4/ self adaptive laser without the requirement of an external seed source.