Free-space quasi-phase matched second harmonic generation in crystalline quartz

TL;DR

This paper demonstrates high-efficiency second-harmonic generation in quartz using free-space quasi-phase matching with multiple passes, achieving significant enhancement over single-pass methods.

Contribution

It presents experimental validation of free-space quasi-phase matching in quartz with multi-pass configuration, significantly improving conversion efficiency.

Findings

Achieved 0.027% conversion efficiency in 62 passes.

Generated 1 μJ of second harmonic from 3.7 mJ pump pulse.

Efficiency enhancement factor of over 1000 compared to single pass.

Abstract

We report experimental results on second-harmonic generation in a z-cut quartz crystal under conditions of free-space quasi-phase matching in a multi-pass cell. In a 62-pass configuration, an efficiency of 0.027% or 1.4x10-4 %/MW/cm2 was achieved, delivering 1 uJ of the second harmonic at 3.7 mJ pump pulse. This corresponds to an enhancement factor of more than 1000 in conversion efficiency as compared to a single pass. The generated second-harmonic beam demonstrates high beam quality M2=1.1 and linear polarization. The scaling of the output power with the number of passes is in good agreement with the calculated values. Further increasing the pump intensity, number of passes, and amount of plates opens the way to scaling the conversion efficiency to values on the order of tens of percent.