A Sodium laser guide star coupling efficiency measurement method

TL;DR

This paper introduces a method for measuring the coupling efficiency of a 20W sodium laser used in adaptive optics, enabling better optimization of laser parameters for improved guide star brightness in astronomical observations.

Contribution

The paper presents a novel measurement method for coupling efficiency of sodium lasers, aiding in the optimization process for adaptive optics systems.

Findings

Field tests conducted from 2013-2015 demonstrate the method's effectiveness.

Coupling efficiency measurement helps optimize laser parameters.

Improved guide star brightness through better laser tuning.

Abstract

Large telescope's adaptive optics (AO) system requires one or several bright artificial laser guide stars to improve its sky coverage. The recent advent of high power sodium laser is perfect for such application. However, besides the output power, other parameters of the laser also have significant impact on the brightness of the generated sodium laser guide star mostly in non-linear relationships. When tuning and optimizing these parameters it is necessary to tune based on a laser guide star generation performance metric. Although return photon flux is widely used, variability of atmosphere and sodium layer make it difficult to compare from site to site even within short time period for the same site. A new metric, coupling efficiency is adopted in our field tests. In this paper, we will introduce our method for measuring the coupling efficiency of a 20W class pulse sodium laser for AO application during field tests that were conducted during 2013-2015.