System and method for limiting effective coherence length of solid-state laser in holographic recording

Abstract

The present invention relates to a system and method for limiting the effective coherence length of a solid-state laser in holographic recording. The effective coherence length of a single-frequency,solid-state laser is limited to reduce the spurious, secondary holograms in conjunction with a holographic recording. The wavelength of the laser is varied or scanned with high precision over a very small wavelength range. In an embodiment, the temperature of the laser's resonant cavity optical bench is altered, thereby causing the dimension of the cavity to change and the emission wavelength to move in a controlled manner. The changing wavelength is monitored at high resolution, and a feedback control loop updates the temperature set-point to keep the monitored laser wavelength moving at a desired rate of change through a desired range. As the wavelength of the laser is scanned, the phase of the holographic interference pattern is locked at a position of maximum coherence / contrast withinthe holographic film aperture.

Description

technical field [0001] The present disclosure generally relates to holographic optical elements, and more particularly, the present disclosure relates to an apparatus and method for controlling the effective coherence length of a single frequency solid-state laser in conjunction with holographic optical element exposure. Background technique [0002] The coherence length of a laser is a measure of the propagation length of the laser's beam above which the coherence degrades significantly. For the purpose of holographic recording, the laser beam is split along two paths and recombined to form an interference pattern in the holographic film. If the beam splitter splits the beam power equally, and the two optical path lengths after the beam splitter are exactly equal, then 100% contrast fringes will be formed at the holographic film. If the two path lengths are not equal beyond the coherence length, the fringe contrast is significantly degraded. In the example of the F15E two...

AI Technical Summary

Problems solved by technology

[0016] Modern solid-state lasers are inherently single-frequency long coherence length devices, but there is no known system or method for reducing the coherence of large-aperture holographic exposures

Unlike argon-ion lasers, solid-state devices do not have etalons that can be removed to limit coherence without fundamentally changing the existing large and expensive exposure hardware infrastructure.

Images