Jae-Cheul Lee

TEM 00 -mode and single-longitudinal-mode laser operation with a cholesteric liquid-crystal laser end mirror

We describe the unique properties of a cholesteric liquid crystal as a laser end mirror. We show how it gives rise to TEM(00)-mode operation as well as single-longitudinal-mode operation of a solid-state laser resonator.

High-repetition-rate Cr:Nd:GSGG active-mirror amplifier

We have designed, constructed, and operated a 3.8-cm clear-aperture Cr:Nd:GSGG active-mirror amplifier. We believe this to be the first active mirror that uses a crystalline host and the largest-aperture Cr:Nd:GSGG amplifier yet reported. We have measured a small-signal gain of 1.6. The wave front has been measured and found to be less than three waves of defocus at repetition rates of up to 10 Hz. Surface displacements were measured and compared with theory. Depolarization was less than 2.5% at maximum power at any location in the clear aperture.

Effects of substrate and deposition method onto the mirror scattering.

The effect of surface roughness onto the mirror scattering has been studied. Five kinds of substrates with different surface roughness were fabricated. On those substrates, dielectric multilayer coating for high reflectivity was deposited by ion-beam sputtering (IBS) and by electron-beam (EB) evaporation. Total integrated scattering (TIS) measurement setup was built for the evaluation of deposited samples. Most of the IBS mirrors showed lower scattering than the EB mirrors, which were deposited on the similar substrates in surface roughness. The ratio of substrate TIS to mirror TIS was defined for evaluation. It increased abruptly at approximately 2A in surface roughness, which indicated that to make low-loss mirrors, the substrate roughness should be less than 2A in rms.

Retro-Self-Focusing and Pinholing Effect in a Cholesteric Liquid Crystal

Abstract In this paper, we show theoretically that a cholesteric liquid crystal exhibits a retro-self-focusing effect and a pinholing effect under the Gaussian intensity distribution of an incident optical field. The retro-self-focusing effect is a result of pitch dilation due to intense optical radiation. We confirm these theoretical predictions by experiment.

Design and construction of 1064-nm liquid-crystal laser cavity end mirrors

We describe the design and construction of cholesteric liquid‐crystal elements for laser cavity end mirror applications and we give the Jones matrix [J. Opt. Soc. Am. 31, 488 (1941)] representation of these devices.

Liquid-Crystal Materials for High Peak-Power Laser Applications

Abstract This is a brief review of materials and device-development issues related to the application of liquid-crystal technology to multikilojoule, high peak-power lasers.

Effects of Anchoring Under Intense Optical Fields in a Cholesteric Liquid Crystal

Abstract In this paper, we show theoretically how the anchoring conditions at the substrate-cholesteric liquid crystal fluid interface affect the pitch change of a cholesteric liquid crystal in an intense optical field. Strong anchoring at both cell interfaces gives rise to pitch dilation and contraction, while strong input side/weak output-side anchoring results in pitch dilation only. Weak input-sidelstrong output-side an-choring creates pitch contraction.

Gain squaring in a Cr:Nd:GSGG active-mirror amplifier using a cholesteric liquid crystal mirror

The small-signal gain of a Cr:Nd:GSGG active-mirror amplifier has been squared using a passive, 10- mu m-thick, cholesteric liquid-crystal selective reflection mirror. This double/double-pass configuration was easy to align and solved difficulties, such as polarization leakage and back-reflection coupling, which had plagued previous multipass schemes. The mechanism for this gain squaring is explained in terms of the optical properties of cholesteric liquid crystals. >

Nd:YAG Laser With Cholesteric Liquid Crystal Cavity Mirrors

Lasing mechanisms for a laser resonator with cholesteric liquid crystal end mirrors were investigated. The effective radius of curvature of a cholesteric liquid crystal mirror was measured. The slope efficiency of a CLC-dielectric resonator was measured and compared with a flat-flat dielectric resonator with or without a pinhole for a Gaussian output.

Laser beam apodizer utilizing gradient-index optical effects in cholesteric liquid crystals

Laser beam apodization has been a goal of solid state laser programs since the early 1970s. Apodization is the shaping of the spatial beam profile to increase the fill factor through the gain medium. This allows more energy to be extracted and also reduces linear and nonlinear edge diffraction effects that cause self-focusing spikes. Here, the fabrication of laser beam apodizers (or soft apertures) with large clear apertures using cholesteric liquid crystals is described. A soft edge profile is achieved by filling a cell with two separate cholesteric liquid crystal mixtures with different selective reflection bands. The fluidlike property of liquid crystals allows them to mix at the interface. In this overlap region, the reflectivity changes as a function of position. This concept is applied to the fabrication of two devices: (1) a one-dimensional beam apodizer with a clear aperture that can be mechanically adjusted by sliding two complementary devices relative to each other and (2) a circular beam apodizer.