Coherent beam combination using self-phase locked stimulated Brillouin scattering phase conjugate mirrors with a rotating wedge for high power laser generation.

Sangwoo Park,Hwihyeong Lee,Hong Jin Kong,Heekyung Ahn,Seongwoo Cha,Kil Sung Churn,Jungsuk Oh

doi:10.1364/oe.24.008641

Abstract

The self-phase locking of a stimulated Brillouin scattering-phase conjugate mirror (SBS-PCM) allows a simple and scalable coherent beam combination of existing lasers. We propose a simple optical system composed of a rotating wedge and a concave mirror to overcome the power limit of the SBS-PCM. Its phase locking ability and the usefulness on the beam-combination laser are demonstrated experimentally. A four-beam combination is demonstrated using this SBS-PCM scheme. The relative phases between the beams were measured to be less than λ/24.7.

Highlights

A high-power laser with a pulse width of several ns, a repetition rate exceeding 10 Hz, and a power level of more than 1 kW has many applications in both scientific and industrial fields [1]
The self-phase locking of a stimulated Brillouin scattering-phase conjugate mirror (SBS-PCM) allows a simple and scalable coherent beam combination of existing lasers
We propose a simple optical system composed of a rotating wedge and a concave mirror to overcome the power limit of the SBS-PCM

Summary

Introduction

A high-power laser with a pulse width of several ns, a repetition rate exceeding 10 Hz, and a power level of more than 1 kW has many applications in both scientific and industrial fields [1]. In 2001, Yoshida et al showed that the input power limit of the SBS-PCM can be increased by continuously moving a focal spot inside the medium using a rotating wedge [16] In this way, the heat load is distributed to a large volume and the reflectivity and fidelity can be improved significantly. The SBS-PCM with the rotating wedge in Yoshida’s scheme is not self-phase-locking and cannot be utilized in a coherent beam-combination laser. There was remaining path length fluctuation of 1 to 3 λ after the alignment depending on the rotating-wedge/SBS-cell combination. We surmised that this was due to the surface irregularity of the optics and the gap in the ball bearing of the rotating wedge mount

Experimental setup and results

Conclusion