Phase-based wavelength measurement apparatus
AssigneeChromaplex, Inc.
InventorRobert Frankel
Life of this patent
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Abstract
A laser wavelength meter determines the unknown wavelength of a laser by measuring the phase difference between two orthogonally polarized beams derived from the laser. The orthogonally polarized beams propagate along two optical paths of different length as defined, for example, by a polarizing beam splitter or a stepped reflector with a defined step height. An in situ reference laser of known wavelength allows calculation and monitoring of the path difference between the two optical paths.
Claims13
Wavemeter for measuring an unknown wavelength of an optical beam, comprising:
- a reference beam of a known wavelength having two orthogonally circularly polarization directions;
- a polarizing beam splitter receiving said orthogonally polarized reference beam and defining an interferometer with a difference in an optical path length between said two orthogonally circularly polarized directions;
- a first analyzer receiving from the polarizing beam splitter a combined reference beam with said path length difference, said first analyzer determining the path length difference from an intensity measurement of said two orthogonally circularly polarization directions of said combined reference beam;
- a polarizer converting the optical beam of the unknown wavelength into two orthogonally circularly polarized beams, with the two orthogonally circularly polarized beams of the unknown wavelength traversing in the polarizing beam splitter an optical path that is substantially identical to an optical path of the reference beam in the polarizing beam splitter, and
- a second analyzer that receives from the polarizing beam splitter a combined beam of the unknown wavelength with said path length difference, said second analyzer determining the unknown wavelength from an intensity measurement of said two orthogonally circularly polarization directions of said combined beam of the unknown wavelength and said path length difference determined by the reference beam.
Method for determining an unknown wavelength of an optical beam, comprising:
- propagating in an polarizing beam splitter two orthogonally circularly polarized beams produced from a reference beam, said two orthogonally circularly polarized beams traversing different optical paths having different path lengths;
- determining a difference in said optical path lengths for said reference beam;
- generating from the optical beam of unknown wavelength two orthogonally circularly polarized beams;
- propagating in the polarizing beam splitter the two orthogonally circularly polarized beams produced from the optical beam along said different optical paths traversed by the reference beam;
- determining a phase shift between the propagated two orthogonally circularly polarized beams produced from the optical beam;
- and
- determining the unknown wavelength of the optical beam from the determined phase shift and the difference in the optical path lengths.
Dependencies are inferred from the claim text.