Massachusetts Institute of Technology

Other

James R Leger

Gary J Swanson

William C Goltsos

Tso Yee Fan

Antonio Sanchez-Rubio

James N Walpole

Wilfrid B Veldkamp

Richard C Williamson

Ivars Melngailis

Joseph L Horner

Michael K Holz

Miles L Scott

A lens system for use with a linearly arrayed light beam including a first optical element for receiving and redirecting different portions of the linearly arrayed light beam to different locations on an imaginary plane so as to generate a two-dimensional pattern of light beams on the imaginary plane; and a second optical element located at the imaginary plane and aligned with the two-dimensional pattern of light beams for redirecting each of the light beams of the two-dimensional pattern of light beams to any arbitrary direction.

Method and apparatus for efficient concentration of light from laser

Apparatus and method for scaling solid-state devices to higher power using multiple sources each of which are separately collimated, followed by focusing of the pump radiation into gain medium colinear to laser mode using a moderated focus. A modularized system is also described.

Multiple-laser pump optical system

An optical element for converting a uniform beam of light of wavelength .lambda. into an array of illuminated spots, the optical element including a phase plate made of an array of constant phase zones; and an image plane disposed parallel to and at a preselected distance from the phase plate, the preselected distance being selected so that illuminating the phase plate with uniform coherent illumination of wavelength .lambda. produces the array of illuminated spots on the image plane, the spot array having a fill factor in at least one dimension that is less than 1/2.

Array illuminator using a binary optics phase plate

An apparatus for generating a coherent combined laser beam including an array of laser elements for generating a Fresnel diffraction pattern in a plane at a distance D from the laser array, the Fresnel diffraction pattern having a non-uniform phase distribution, D being at least as large as the distance at which the beams generated by the laser array begin to substantially overlap; and an array of phase corrector elements located in the plane for reducing the degree of non-uniformity in the phase distribution; and a partially reflecting mirror for forming a resonant cavity for the laser array.

Optical device for laser coupling and coherent beam combining

An apparatus for coherent beam combining of lasers and for lateral mode control is disclosed, comprising a miniature Talbot cavity having at least a first and second surface. The first surface is to receive light from said lasers, and the second surface contains a reflecting mirror. In one embodiment, the mirror spaced apart from said first surface by a distance Z=nd.sup.2 /.lambda. where n is a nonnegative integer, .lambda. is the laser wavelength, and d is the laser aperture spacing. In this embodiment, the mirror is divided into reflecting and non-reflecting portions, the reflecting portions patterned to reflect only that portion of the light from said lasers having a half-period shift corresponding to a fundamental lateral mode. In another embodiment, the mirror is spaced apart from the first surface by a distance Z, such that nd.sup.2 /.lambda.&lt;Z&lt;(n+1)d.sup.2 /.lambda., where n is a nonnegative integer, .lambda. is the laser wavelength, and d is the laser aperture spacing. In both embodiments, a lenslet array may be place to receive the light from the lasers, the lenslet array being separated from the mirror by the distance Z.

Miniature Talbot cavity for lateral mode control of laser array

A technique for coherent aperture filling by amplitude phase exchange is described which suppresses the far field side lobes of an array of lasers. The power contained in these side lobes is transferred to the central lobe so that it contains greater than 90% of the total array power. This is achieved by a field transformation which generates from the uniform phase and varying amplitude distribution of the input array a varying phase modulation with nearly uniform, i.e., aperture filled, amplitude distribution in the output beam. Far-field grating lobes from the nonuniformity in phase are then suppressed by an additional phase correcting element matched to compensate the phase modulation. In a preferred embodiment, the field transformation element, including a single step binary phase shifter flanked by a pair of lenses in an a focal imaging configuration, is followed by a binary phase grating for phase compensation.

Coherent aperture filling of an array of lasers

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

A binary phase-only optical correlation system incorporating therein a binary phase-only filter. The binary phase-only optical filter is made by mathematically generating preselected phase-only information by a fast Fourier Transform technique. This generated phase-only information is binarized into a function having two values. This binarized function is utilized to produce a mask which in turn is used in conjunction with an appropriate optical substrate to produce the binary phase-only filter. The manufacture of the binary phase-only filter is substantially easier than the production of a phase-only filter yet virtually the same correlation results when the binary phase-only filter when it is used in an optical correlation system.

Binary phase-only optical correlation system

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.

Growing community of inventors

Groton, MA, United States of America

James R Leger