On-axis laser receiver wavelength demultiplexer with integral immersion lensed detectors
First Claim
1. A method for receiving high frequency signals transmitted through free space, comprising:
- passing one or more optical signals, the one or more optical signals containing data and being composed of radiation of a plurality of differing wavelengths, through a diffractive optical element to form a plurality of signal segments, each signal segment having a different mean wavelength;
passing a portion of a beam comprising each of said one or more optical signals through a phase retarder that is provided separately from said diffractive optical element, wherein said portion of said beam passed through the phase retarder comprises an area of the beam that is less than a total area of the beam in cross-section, wherein said phase retarder has an area that is less than an area of said diffractive optical element, wherein a first portion of the optical signal is passed through said phase retarder, wherein the first portion of the optical signal has a different phase than a second portion of the optical signal that is not passed through the phase retarder, anddetecting data in each of said plurality of signal segments at or near a different spatial focal point, wherein a portion of said plurality of said detected signal segments has passed through said phase retarder.
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Accused Products
Abstract
The present invention is directed to a laser communication receiver for wireless optical communication. A laser communication receiver includes a diffractive optical element to permit detectors at different spatial locations to detect different wavelengths of the optical signal. An immersion lens may be employed to focus the optical signal to a spot size smaller than the photoactive area of the detector. In one detector configuration, the optical signal is folded by a reflective surface and focused on a plurality of stacked detectors. The present invention further provides a method of manufacturing a detector and immersion lens assembly that provides a high degree of alignment between the lens and the corresponding detector.
93 Citations
73 Claims
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1. A method for receiving high frequency signals transmitted through free space, comprising:
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passing one or more optical signals, the one or more optical signals containing data and being composed of radiation of a plurality of differing wavelengths, through a diffractive optical element to form a plurality of signal segments, each signal segment having a different mean wavelength; passing a portion of a beam comprising each of said one or more optical signals through a phase retarder that is provided separately from said diffractive optical element, wherein said portion of said beam passed through the phase retarder comprises an area of the beam that is less than a total area of the beam in cross-section, wherein said phase retarder has an area that is less than an area of said diffractive optical element, wherein a first portion of the optical signal is passed through said phase retarder, wherein the first portion of the optical signal has a different phase than a second portion of the optical signal that is not passed through the phase retarder, and detecting data in each of said plurality of signal segments at or near a different spatial focal point, wherein a portion of said plurality of said detected signal segments has passed through said phase retarder. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for receiving high frequency signals transmitted through free space, comprising:
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dividing an optical signal, the optical signal containing data and being composed of radiation of a plurality of differing wavelengths, into a plurality of signal segments, each signal segment having a different mean wavelength; passing a portion of one of the divided optical signal and the optical signal through a phase retarder, wherein said portion is a partial cross section of the one of the divided optical signal and the optical signal; reflecting said divided signals towards a plurality of spaced apart detectors; reducing the spot size of the signal segments using an immersion lens that is integral to each of the plurality of detectors; and detecting, with said plurality of spaced apart detectors data in each of said plurality of signal segments, wherein each of said spaced apart detectors is located substantially at a different focal point, the focal points being at different positions along a common optical axis, and wherein, and wherein each said focal points receives at least some of said portion of one of the divided optical signal and the optical signal passed through said phase retarder. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. An apparatus for receiving an optical signal transmitted through free space, the optical signal being composed of radiation of a plurality of wavelengths, comprising:
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at least one diffractive optical element for focusing a beam of radiation of different wavelengths at different corresponding focal points and thereby creating a focused beam of radiation, wherein said focal points are at different positions along the optical axis of said optical element, wherein said focal points are at different positions along the has a diameter that is greater than a Fresnel scale for said plurality of wavelengths and a distance from a transmitter, and wherein said focal points encompass a first area comprising a first spot size or greater; a phase retarder, wherein less than an entire cross section of one of said beam of radiation of different wavelengths and said focused beam of radiation is passed through said phase retarder; and a plurality of detectors, each detector being located at or near a different one of the focal points and receiving the radiation focused on the focal point corresponding to the detector, wherein each of the plurality of detectors has a photoactive area equal to a second area that is less than said first area, wherein each of said plurality of detectors is associated with a focusing element comprising an immersion lens that reduces the spot size of incident radiation to no more than said second area, and wherein a portion of said radiation focused on a focal point of at least two of said detectors has passed through said phase retarder. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. An apparatus for receiving an optical signal transmitted through free space, the optical signal containing data, comprising:
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a first holographic element for focusing radiation including a number of different wavelengths, wherein each wavelength is focused to a different point; a phase retarder having an area that is less than an area of the first holographic element, wherein the phase retarder has a maximum radius that is no greater than 80% of a radius of the first holographic element; a number of detectors; and a number of second lenses, wherein one of said second lenses is located between the first holographic element and an associated detector, the second lens reducing a spot size of the focused radiation after passing through the second lens, wherein at least some radiation passed through said phase retarder is passed through each of said second lenses. - View Dependent Claims (35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45)
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46. A method for receiving high frequency signals transmitted through free space, comprising:
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first passing an optical signal, the optical signal containing data, through a first lens comprising a diffractive optical element provided as part of a receiver to form focused radiation having a first mean wavelength, wherein said first lens subtends at least about 50 microradians of a beam comprising the optical signal, and wherein at the receiver the optical signal has an angle of divergence of at least 20 microradians, and wherein less than an entire cross-section of the beam comprising the optical signal containing data is passed through a phase retarder that is provided in addition to the diffractive optical element; second passing the focused radiation through a second lens to form converging radiation having a second mean wavelength, the first mean wavelength being different than the second mean wavelength; and detecting data in the convergent radiation at a plurality of detectors, wherein at least some radiation received at each of said detectors has passed through said phase retarder, and wherein at least some radiation received at each of said detectors has not passed through said phase retarder. - View Dependent Claims (47, 48, 49, 50, 51, 52, 53, 54, 55)
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56. An apparatus for receiving an optical signal, the optical signal containing data, comprising:
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a first optical element for focusing a set of different optical wavelengths in the optical signal at different locations along a first optical axis of said first optical element; a second optical element for retarding a phase of a portion of said optical signal; a reflective surface for reflecting the focused set of different optical signals and a plurality of detectors forming a reflected set of different optical signals; and a number of detectors, wherein for each detector there is an associated immersion lens, wherein the immersion lens of each detector is positioned to receive one of the reflected optical signals, the immersion lenses being located along the first optical axis, and wherein each detector receives at some of said at least a portion of said optical signal passed through said phase retarder. - View Dependent Claims (57, 58, 59, 60, 61, 62, 63, 64, 65)
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66. A method for receiving an optical signal transmitted through free space, comprising:
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first passing the optical signal, the optical signal containing data, through a first lens to form a plurality of signal segments, each corresponding to a different median wavelength, wherein the first lens is a diffractive optical element; second passing a portion comprising less than an entire area of a cross-section of the optical signal through a phase retarder; reflecting the plurality of signal segments off a reflective surface to form reflected radiation; and detecting data in the reflected radiation at or near an optical focal point for each of the signal segments, wherein a portion of each of said signal segments has passed through said phase retarder; wherein the optical signal has a beam size that is less than a size of an inner scale in the vicinity of the source transmitter, and wherein passing a portion of the optical signal through a phase retarder reduces smear in the signal segments. - View Dependent Claims (67, 68, 69, 70, 71, 72, 73)
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Specification