Laser Beam Steering Control System for Free-Space Line of Sight Optical Communication

Abstract

The paper describes a beam steering control system for a propagating laser beam, which is essential in free-space optical link. The tilt of the laser beam is measured with an indigenously developed Shack-Hartmann Wavefront Sensor (SHWFS) and dynamically compensated using a piezo-driven tip-tilt mirror. The system uses a commercial frame grabber and a CCD camera, which are less expensive. Spatial sampling of the beam with a 10 × 10 microlens array, Zernike Polynomial decomposition up to 4th order and real-time display of tilt-map are carried out. Tilt measurement to an accuracy of 2 pradians has been achieved. Experimental results of wavefront measurements using our SHWFS as well as tilt compensation are presented.

Indexing terms:

• Free-space optical communication
• Optical satellite communication
• Shack-Hartmann wavefront sensor
• Adaptive optics

Additional information

Notes on contributors

A R Ganesan

AR Ganesan received his PhD in Physics from the Indian Institute of Technology, Madras, India in the year 1989. His areas of research include holography, speckle metrology, applied optics, laser instrumentation, interferometry, optical communication and adaptive optics. He had been a post doctoral fellow at the Institute of Advanced Studies, University of Malaya, Malaysia during 1989–91. He was an Assistant Professor at Alabama A&M University, Huntsville, USA during 1991–92. He is a recipient of Alexander von Humboldt Fellowship from Germany during 1992–1994. He has published around 50 papers and is a reviewer for a few international journals in Optics. He is a Fellow of the Optical Society of India and member of many professional bodies. He has handled several projects sponsored by various agencies. Currently he is an Assistant Professor in the Department of Physics, National Institute of Technology, Tiruchirappalli, India. He is heading the research group working on the areas of Adaptive Optics and Photonics Instrumentation.

P Arulmozhivarman

P Arulmozhivarman received his MSc Applied Physics degree from Bharathidasan University, Tiruchirappalli, India in the year 1997. His area of research include laser instrumentation, interferometry and adaptive optics. From 1997 to 2000 he was a Lecturer in Electronics & Instrumentation Engineering in Shanmuga College of Engineering (SASTRA University), Thanjavur, India. From 2000 to 2002 he was a project officer in DRDO sponsored project, at Department of Physics, Regional Engineering College, Tiruchirappalli, India. He is now a doctoral student at the Department of Physics, National Institute of Technology, Tiruchirappalli, India. His current work focuses on investigations in Optical wavefront sensing and control.

D Mohan

D Mohan obtained his MTech degree in Applied Optics from IIT Delhi and currently heading adaptive optics group at IRDE, Dehra Dun. He has worked in the field of holography and optical image processing. He is presently engaged in the design & development of adaptive optics system for imaging application. He has published over 20 research papers in national & international journals. He is fellow of The Optical Society of India, Member of Indian Laser Association & Instrument Society of India.

A K Gupta

AK Gupta obtained his MTech & PhD in Applied Optics from IIT, Delhi. He is currently heading Photonics Division at IRDE, Dehradun. He has worked on the design & development of laser based system for metrological application, laser guidance technology and laser proximity sensors. He is presently engaged in the latest areas of Photonics like Optical Image Processing, Adaptive Optics, Integrated Optics & Holography. He was awarded Monbusho fellowship during 1984–86. He has published more than 30 papers in national and international journals. He is fellow of the Optical Society of India, Member of Indian Laser Association, Indian Science Congress & SPIE.