Phase Compensation for High Power Lasers Using Refracting Gas Prisms
Final rept. 1 May 1977-31 Oct 1978
WASHINGTON UNIV SEATTLE COLL OF ENGINEERING
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Laser beams propagating through the atmosphere are subject to considerable phase distortion due to variations of the air density. The beams emitted by high-power lasers can also be distorted due to density variations inside the laser cavity. One of the main applications of active optics is the compensation of these wavefront distortions in order to enhance the intensity of a laser beam on a distant target. A new method of phase compensation using the refractive properties of gas jets is being investigated as an alternative method for phase front control. Gases of different optical properties index of refraction with sufficient optical depth are placed in the path of the laser so that passage through the gas elements produces phase shifts in the beam itself. Actively changing the gas index of refraction using flow will permit the control necessary to achieve phase compensation. The geometry required to bring about localized phase compensation in the laser beam is possible by using independent jets of gas each with its own dither and feedback circuiting as is done with conventional COAT technology. By replacing the solid array elements by jets of gas of varying refractive index, the power handling capacity of the COAT system can be raised to very high levels while maintaining a frequency response in the kilocycle range. This is the essence of the fluid COAT idea. Coherent Adaptive Optical Techniques.