High average power harmonic generation

Abstract

High average power frequency conversion using solid-state nonlinear materials is discussed. Recent laboratory experience and new developments in design concepts show that current technology, a few tens of watts, may be extended by several orders of magnitude. For example, using KD*P, efficient doubling (> 70 percent) of Nd:YAG at average powers approaching 100 KW is possible; for doubling to the blue or UV regions the average power may approach 1 MW. Configurations using segmented apertures permit essentially unlimited scaling of average power. High average power is achieved by configuring the nonlinear material as a set of thin plates with a large ratio of surface area to volume, and cooling the exposed surfaces with a flowing gas. The design and material fabrication of such a harmonic generator is well within current technology. F INTRODUCTION REQUENCY conversion is a useful technique for extending the utility of high power lasers. It utilizes the nonlinear optical response of an optical medium in intense light fields to generate new frequencies. Frequency doubling, tripling, and quadrupling generate a single harmonic from a given fundamental high power source. The closely related processes of sum and difference frequency generate also generate a single new wavelength, but require two high power sources. These techniques have been used to generate high power radiation in all spectral regions, from the UV to the far-IR. Optical parametric oscillators and amplifiers generate two waves of lower frequency. They are capable of 'generating a range of wavelengths from a single .frequency source, in some cases spanning the entire visible, and near-infrared regions. The materials used for frequency conversion are often also suitable for other devices, such as electrooptic Manuscript

Analytic and experimental investigations on influence of harmonic generation on acousto-optical modulation

“…Θ SHG , Θ THG , Θ* SHG and Θ* THG are calculated using the stated parameters and Eqs. (6), (8), (11), and (13). Due to missing delay compensation, the experimentally obtained values for Θ THG and Θ* THG are significantly lower than the calculated values as of neglection of group velocity delay.…”

“…The intensity of the second harmonic beam I SHG (x,y) can be expressed by Eq. (5) [10,11], where L is the interaction length, d eff the effective non-linear coefficient (with m/V as unit), ε 0 the dielectric constant (ε 0 = 8.854 10 −12 F/m), ω = 2π c 0 /λ FUN the angular frequency and Ζ = Ζ 0 /n the impedance (Z 0 = 377 Ω). The intensity profile I FUN (x,y) is equivalent to Eq.…”

“…Calculated values for Θ SHG, Θ* SHG, Θ THG and Θ* THG are expected to be higher than experimentally derived values due to neglection of walkoff, dephasing, group velocity delay and other effects. It has to be noted that there are more detailed ways to calculate SHG and THG conversion efficiencies such as [11,12]. However, for anticipated usage, the formulas stated proved to be more than adequate.…”

Compact, Efficient, Low-cost Lasers (CELL) Project: Final Report

“…Conversion to the second and third harmonics is accomplished via a cascaded 4-crystal design, 54 two DKDP crystals each for second and third harmonic conversion, as shown in Fig. 15.…”

All-Poly-Crystalline Ceramics Nd:YAG/Cr4+:YAG Monolithic Micro-Lasers with Multiple-Beam Output

“…where d= k/(c g  g ), and the coefficient k is given by the second-harmonic generation theory (Eimerl, 1987;Honea et al, 1998). The green pulse energy is 2 () (1 )ln This was the first passively Q-switched Nd:YAG-Cr 4+ :YAG laser intra-cavity frequency doubled with LBO nonlinear crystal.…”