Analogue holographic wavefront sensor: a performance analysis

Abstract

The efficiency of laser communications systems is significantly limited by atmospheric effects. Notably challenging scenarios like a long horizontal path or strong scintillation lead to high failure rates of the electro-optical systems. Adaptive optics (AO) methods and components developed for astronomical applications cannot fulfill these higher requirements. The so-called Holographic Wavefront Sensor (HWFS) is a promising alternative for measuring the wavefront deformation of a laser beam. The basic elements of the HWFS are a diffraction pattern and a fast photodetector like a photodiode array. With these components the aberrations present in the beam are measured directly. In this paper we present an optical setup to verify two important features of the sensor type experimentally: high measurement speed and the sensor’s response on present scintillation. Measurements with the HWFS were performed at a bandwidth of 11 kHz for a single aberration and of 2.5 kHz for 6 aberrations simultaneously. Furthermore we operated the HWFS in a closed-loop adaptive optics system with a bandwidth of 600 Hz. We show that the wavefront correction based on the HWFS measurements is insensitive to dynamic partial intensity fluctuations of the laser beam.