Massachusetts Institute of Technology

United States of America As Represented by the Secretary of the Air Force

Wilfrid B Veldkamp

Gary J Swanson

James R Leger

Michael W Farn

Richard J Becherer

Miles L Scott

Optical apparatus for dispersing a visible light spectrum into primary color bands and directing each color band into a specific pixelated cell of a passive display. The apparatus includes an array of refractive microlenses arranged parallel to the plane of the passive display such as a liquid crystal display and a diffraction grating arranged parallel and in close proximity to the lens array. The microlenses focus visible light onto the display while the diffraction grating separates the visible light into primary color bands in different diffraction orders such that the colors are directed to and transmitted through the corresponding specific pixelated cells.

Diffractive microstructures for color separation and fusing

The method utilizes high resolution lithography, mask aligning, and reactive ion etching. In particular, at least two binary amplitude masks are generated. A photoresist layer on an optical element substrate is exposed through the first mask and then etched. The process is then repeated for the second and subsequent masks to create a multistep configuration. The resulting optical element is highly efficient.

High-efficiency, multilevel, diffractive optical elements

A high-efficiency, diffractive optical element having at least one surface including multilevel steps, the steps determined by calculating equiphase boundaries utilizing a disclosed equation and algorithm. The optical element can be adapted to correct for chromatic and/or spherical aberration, and can be used in UV lithographic apparatus.

A detector array including a substrate having an array of diffractive lenses formed on the top side of the substrate and an array of sensor elements formed on the backside of the substrate. The sensor elements within the sensor array are oriented on the backside so that each sensor is aligned to receive light from a corresponding diffractive lens of the lens array. The detector array may also include a second substrate having an array of diffractive elements formed on one of its surfaces, the second substrate being disposed above and in proximity to the top side of the other substrate so that the elements on the second substrate are substantially aligned with corresponding sensor elements and diffractive lenses on the other substrate.

Optically coupled focal plane arrays using lenslets and multiplexers

The high diffraction efficiency regime of binary gratings occurs at periodicities on the order of a wavelength in order to produce grating which diffract radiation with efficiencies of greater than 90%, a fabrication procedure is disclosed which uses halographic and very large scale integration techniques which allow fine control over the periodicity and depth parameters to produce binary planar optical elements having a ratio of .lambda./T greater than one (where .lambda. equals the wavelength of an illuminating wavefront, and T equals the grating periodicity). Additionally, the disclosed process produces high optical quality diffractive elements with phase precision of as high as .lambda./100. These diffractive elements include laser beam multiplexers, beam profile shapers, and binary lenses which are lossless optical transfer functions.

Method of fabricating high efficiency binary planar optical elements

A diffractive lenslet array receives light from multiple lasers. The lenslet array is spaced apart from a partially reflecting mirror by a distance Z=nd.sup.2 /.lambda. where n is an integer or half integer, .lambda. is the laser wavelength and d is the spacing of the lenslets in the array. In a preferred embodiment the apparatus is a unitary design in which the lenslets are etched into one surface of a substrate and a parallel surface is coated to form the partially reflecting mirror. The lenslets abut one another to produce a fill factor (percentage of array containing light) close to one and each of the lenslets is a multistep diffractive lens. Diffractive speading over a round trip distance from lasers to mirror and back again causes feedback light from a single lenslet to couple into adjacent lenslets. The light from all the lenslets is coupled back into the laser waveguides efficiently only when the wavefront at each of the lenslets is flat, that is, when the phase of the feedback is uniform across a lenslet. Uniformity is achieved when the separation between lenslet array and mirror is the Talbot self-imaging condition set forth above.

Coherent beam combining of lasers using microlenses and diffractive

The disclosed apparatus includes a diffraction grating illuminated by a plurality of lasers. Apparatus is provided for summing the plurality of lasers coherently by, (a) phase locking the plurality of lasers and by, (b) diffracting the plurality of beams into a single beam. The diffraction grating has a configuration to generate upon illumination substantially equal intensities of diffraction orders corresponding to the number of lasers while suppressing higher unwanted orders. The phase locking can be accomplished by a single master laser, or by a cavity mirror to generate reference beams. Then, the output beams of the plurality of lasers propagating in the reverse direction are coherently superimposed by that grating. It is preferred that the diffraction grating be binary. Both one and two-dimensional diffraction grating arrays are disclosed. In one embodiment, the phase of the plurality of lasers is locked together by means of a separate injection lock laser, in another embodiment the grating is part of a multielement cavity. In a preferred embodiment, the binary grating is a periodic pattern, where the structure of the periodicity is determined by the number of laser beams. Then, an injection lock laser illuminates that grating and locks together the phases of the plurality of lasers whose beams are to be added. Or, alternatively, a mirror is substituted for the injection lock laser and it provides the illumination beam to the grating which then generates the plurality of beams.

Apparatus and method for coherently adding laser beams

The intensity profile of a beam of electromagnetic waves such as a laser beam is shaped by means of a diffraction grating and/or prism in the beam path. In one embodiment, beams exhibiting Gaussian energy intensity profiles undergo an energy redistribution to approximately uniform profiles. A reflective or transmissive surface relief grating is employed with phase steps generally periodic except at the pattern center where a pattern phase reversal occurs. Prisms are cut and oriented relative to the incoming beam to operate at the Brewster's angle for compressing or expanding the beam with minimum losses.

Method and apparatus for shaping electromagnetic beams

A system to achieve heterodyne detection of optical (i.e., infrared, visible and ultraviolet) signal wavefront is disclosed. The system employs a holographic phase grating that, when illuminated by laser radiation, will generate a plurality of wavefronts each of which has a predetermined spatial distribution of amplitude and phase. The grating is part of an optical local oscillator that includes a laser that illuminates the holographic phase grating. The system further includes a mechanism to receive an optical-signal wavefronts and combine this wavefront with a plurality of local-oscillator wavefronts to provide combined optical wave fields that are applied as input to an array of discrete detector elements; each detector of the array optimally mixes the one local-oscillator wavefront directed to it with the optical-signal wavefront and generates therefrom an electrical output with optimum detection efficiency and with optimum amplitude and fixed phase relationships to the outputs of the other detectors of the array. The optical heterodyne array detection system produces detection of a plurality of optical-signal, spatial-resolution elements simultaneously.

Growing community of inventors

Lexington, MA, United States of America

Wilfrid B Veldkamp