Polarization insensitive tunable optical filters
AssigneeMicron Optics, Inc.
InventorRobert H. Cormack
Life of this patent
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Abstract
A polarization insensitive tunable optical filter system combines an interference filter or the like with a quarter wave plate and a retro-reflector. The retro-reflector is situated and aligned to intercept light reflected from the filter, and the quarter wave plate is disposed between the filter and the retro-reflector. Hence, the pass signal reflected off the filter a first time passes through the quarter wave plate a first time, reflects off of the retro-reflector, passes through the quarter wave plate a second time, and reflects off of the filter a second time.
Claims18
A polarization independent tunable optical filter system comprising:
- a filter of the type which reflects a pass signal and transmits a drop signal according to frequency, tunable by rotation with respect to the input beam;
- and
- a retro reflector assembly situated and aligned to intercept light reflected from the filter, the retro reflector assembly including:
- a quarter wave plate, and
- a retro reflector element,
- wherein the pass signal reflected off the filter a first time passes through the quarter wave plate a first time, reflects off of the retro reflector, passes through the quarter wave plate a second time, and reflects off of the filter a second time.
A polarization independent tunable optical filter system comprising:
- filter means for reflecting a pass signal and transmitting a drop signal according to frequency;
- and
- retro-reflector means situated and aligned to intercept and reflect light reflected from the filter means, the retro-reflector means including:
- means for rotating the polarization of light by 90°, and
- means for reflecting light back to the filter means,
- wherein the pass signal reflected off the filter means a first time reflects from the retro-reflector means, and reflects off of the filter means a second time.
The method for filtering unpolarized light comprising the steps of:
- reflecting a pass signal off of a filter and transmitting a drop signal through the filter according to frequency;
- rotating the reflected pass signal by 90°;
- reflecting the rotated signal off of the filter a second time;
- and
- providing the rotated and twice reflected signal as a pass output signal.
Dependencies are inferred from the claim text.