Paper
10 May 2007 The reflective properties of a volume Bragg grating exposed to a high power laser beam
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Abstract
The material in which a volume Bragg grating is made will always have some absorption at the grating's design wavelength. Thus, when exposed to a high power laser beam the grating will absorb some power, be heated such that a temperature gradient is formed and, consequently, become distorted. We developed an accurate model to calculate the reflection of a high power laser beam by a volume Bragg grating that experiences such distortion. We used the beam propagation method (BPM) to calculate the laser beam propagation in the grating numerically, and the BPM calculations are iterated to account for the counter propagation of the laser beam in the volume Bragg grating. We devised a new method to assure convergence in the iteration of the BPM calculations when the grating diffraction strength is very large. We also established a new formulation of the wave equation to include the grating period distortion in the BPM formulation. The surface distortion and temperature induced background index change are also included in the model. This model has been validated to be correct and very accurate. We applied it to calculate the reflection of a high power laser beam by a distorted volume Bragg grating which has large diffraction strength. Our calculation shows that a small amount of grating structure distortion could introduce significant changes of both the phase and intensity patterns of the reflected laser beam. Understanding such changes is critical to the application of volume Bragg grating to high power laser systems.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Hong Shu and Michael Bass "The reflective properties of a volume Bragg grating exposed to a high power laser beam", Proc. SPIE 6552, Laser Source Technology for Defense and Security III, 655206 (10 May 2007); https://doi.org/10.1117/12.714166
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KEYWORDS
Distortion

Fiber Bragg gratings

Reflection

Diffraction gratings

High power lasers

Beam propagation method

Laser beam propagation

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