Power Amplification of a Phased Array Steered Laser Beam
- Paper number
IAC-07-C3.1.07
- Author
Mr. Christian Schaefer, Kobe University, Japan
- Coauthor
Dr. Nobuyuki Kaya, Kobe University, Japan
- Coauthor
- Coauthor
Dr. Osamu Matoba, Kobe University, Japan
- Year
2007
- Abstract
Laser Power Transmission (LPT) is considered since more than 10 years as a method for beaming energy over large distances in space. Several applications were proposed in the past ranging from powering satellites during their earth-eclipse or a lunar station during night from earth to a satellite power network or even to short range power links like planetary rover missions. Since beam steering is extremely critical in all applications, it is necessary to implement a reliable steering device. In the last few years, laser beam steering by optical phased arrays (OPA) that are completely non-mechanical devices, were proposed and demonstrated for satellite optical communication and for LPT. OPAs steer a laser beam in that way that a beam experiences a spatial phase shift in form of a phase-ramp by passing through the device. The slope of that phase-ramp determines the deflected angle. We focus in this paper on the most frequently used OPA that is a spatial light modulator (SLM) based on twisted nematic liquid crystals. It provides a very high resolution in steering a beam by a moderate response time. Since the efficiency is limited to about 50The first method is based on a laser gain medium, which acts as a traveling wave amplifier. A beam passing through the amplifying medium experiences a power gain exponentially rising with the length of the medium. Therefore, even a very small size media can lead to a high gain. We present results of an experiment using a laser dye as medium, which is pumped by a green laser. The second method is applying photorefractive two-wave mixing. In here, the laser beam is initially split into a weak and a strong beam. The weak beam passes through the SLM and is recombined with the strong beam inside a photorefractive crystal. The combined strong beam now carries the spatial information of the phased array and can be steered freely. Pros and Cons of these two methods are discussed in this paper based on experimental data. Furthermore, an outlook is given for implementing the devices into a retro-directive laser tracking system. δ
- Abstract document
- Manuscript document
IAC-07-C3.1.07.pdf (🔒 authorized access only).
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