Robust 17 W single-pass second-harmonic-generation at 532 nm and relative-intensity-noise investigation

Abstract

We demonstrate a 17 W single-frequency, low-intensity-noise green source at 532 nm, by single-pass second-harmonic generation of a 50 W continuous-wave fiber laser in a 30 mm MgO-doped periodically-poled stoichiometric lithium tantalate crystal. The maximum conversion efficiency is about 37%. A nearly Gaussian beam ( M 2 &lt;<!-- 1.15 at 15 W) and low wavefront distortion are obtained. The system shows stable behavior over 100 h of uninterrupted operation. The evolution of the relative-intensity-noise transfer from the fundamental to the second harmonic is theoretically and experimentally investigated with high resolution.

High power continuous laser at 461 nm based on a compact and high-efficiency frequency-doubling linear cavity

“…The SH component shows an excess of noise in the acoustic band on a plateau at -105 dBc/Hz extending till 10 kHz, then it rolls off with a general 𝑓 −1 trend. The doubling process adds excess intensity noise in the whole Fourier frequency range, as already observed in previously published works based on resonant doubling cavities [24,25] but not in single pass systems [26]. The strong focusing of the fundamental mode on the crystal, imposed to obtain a high conversion efficiency, produces as a side-effect the multi-lobe cross-section of the frequency doubled beam, whose intensity is well described by a sinc 2 function; the central lobe of the output beam contains more than 90% of the power, and we correct its aspect ratio using two cylindrical lenses to improve the single mode fiber injection efficiency.…”

Fiber based high power low noise single frequency lasers and applications

“…Again, low noise sources are necessary in modern physics, laser pumping and industrial applications. We have been able to demonstrate up to 17 W of low noise green radiation at 532nm by efficient single pass doubling (see Fig 1 (c)) and develop a model of the SHG intensity noise transfer in the saturation regime [6]…”

Fiber-Interferometric Second Harmonic Generator with Dual-Color Standard Quantum-limited Noise Performance

“…While SHG for instance is theoretically able to suppress input fluctuations even beyond the standard quantum-limit (SQL) under certain conditions [27][28][29][30], the narrow parameter space and high requirements regarding system stability and alignment often not allow the successful implementation for many experimental setups. To the contrary, the vast majority of recent experimental studies report a strong amplification of the input RIN by up to 6 dB and a broadband increase in RIN spectral density, usually explained with the quadratic dependence of the SHG power stability on pump power fluctuations [31][32][33][34][35].…”