Coherent light generators – Particular beam control device – Modulation
Patent
2000-02-18
2000-12-05
Scott, Jr., Leon
Coherent light generators
Particular beam control device
Modulation
372 13, 372 12, 372 34, 372100, 372 66, 372 39, 372 32, H01S 310
Patent
active
061576603
ABSTRACT:
The present invention relates to apparatus for providing orthogonally polarized light beams for use in precision metrology applications such as in the measurement of length or length changes using interferometric techniques. An input beam is introduced to a multifaceted anisotropic optically active acousto-optical crystal for travel through an interactive region where it experiences two acoustic beams that diffract it via small angle Bragg diffraction to form two orthogonally polarized internal beam components that are separated by a small angle of divergence and subsequently become external beam components available outside of the acousto-optical crystal for use in anticipated downstream applications. The acousto-optical crystal preferably is a uniaxial crystal comprising TeO.sub.2. The degree of overlap or spatial separation between the energy flux profiles of the orthogonally polarized, external beam components may be controlled by refracting properties of the acousto-optical crystal, its birefringence, the acoustical and optical properties of the acousto-optical crystal, the length of the physical path of travel experienced by the emergent beam through the acousto-optical crystal and external birefringent elements. Thermal compensation may be provided via the control of the frequency of the first and second oscillators and/or the properties of the external birefringent elements.
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Caufield Francis J.
Jr. Leon Scott
Zygo Corporation
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