General Dynamics Corporation, Electronics Division

Tacan Corporation

General Dynamics Corp., Electronics Divn.

General Dynamics Corporation

Eric M Bradley

Ronald F Mathis

An array of diode lasers selected to emit at certain fixed wavelengths is assembled to temperature stabilzed Bragg reflectors to assure maintenance of the selected wavelength within 1 .ANG.. One laser is included in the array for each wavelength at which absorption will occur within a photochemically active optical storage medium. Each temperature stabilized laser is focussed by a lens onto an optical storage medium containing photoactive chemical components containing guest and hose molecules, as is known in the art. Light emitted by each laser will be used to burn a pit for each bit of data at the locations of the storage medium. One or more photodetectors located on the opposite side of the sotrage medium to detect the presence or absence of a hole with respect to the selected wavelength with which the hole was initially burned. A similar device is available with a temperature stabilized tunable laser which accurately controls the selected wavelength withing 1 .ANG..

Optical data storage using temperature stabilizer lasers

An integral waveguide is formed in the epitaxial layers as a continuation of a diode laser. The waveguide runs away from the laser active region. Light is coupled out of the laser and its integral waveguide into a dielectric waveguide which runs parallel and adjacent to the integral waveguide. Processing to form the temperature-stabilized Bragg grating, therefore, need not be performed on the laser substrate directly adjacent to the active area, but can be done some distance away to avoid damage to the laser's active area.

Method of monolithic temperature-stabilization of a laser diode by

A dielectric film is deposited on a glass substrate which is transparent to the emission wavelength of a grating coupled surface emitting laser. The dielectric film has a continuously varying refractive index with thickness, usually in the form of a sine wave. The rugate filter is assembled to overlie the second order grating of the laser so that a peak wavelength .lambda..sub.p is reflected back into the second order grating which couples the light into the laser. By reflecting light at the peak wavelength back into the laser, the laser is caused to emit at the desired wavelength. Since the rugate filter selectively reflects light within a narrow band of the desired wavelength, the laser emits light within the same narrow band which can be set to any wavelength by choosing the rugate filter's grating period. The use of a rugate filter separately assembled from the laser permits the creation of a matrix of filters, each filter fabricated to select a discrete wavelength so that a single array of surface emitting lasers can emit at multiple distinct stabilized wavelengths according to the filters in the matrix.

Hybrid rugate filter assembly for temperature stabilized emission of

A glass film is deposited over the second order grating of a grating coupled surface emitting laser. The glass film has a continuously varying refractive index with thickness, usually in the form of or similar to a sine wave. The rugate filter is assembled to overlie the second order grating of the laser so that a peak wavelength .lambda..sub.p is reflected back into the second order grating which couples the light into the laser. Be reflecting light at the peak wavelength back into the laser, the laser is caused to emit at the desired wavelength. Since the rugate filter selectively reflects light within a narrow band of the desired wavelength, the laser emits light within the same narrow band. The use of a surface emitting laser facilitates summing of the output light of several adjacent lasers within a monolithic array to provide high power output.

Rugate filter on grating coupled surface emitting laser array

The rugate filter comprises a glass film which is deposited on one or both end facets of a diode laser. The glass film has a continuously varying refractive index with thickness, usually in the form of a sine wave or a 'windowed' sine wave. Such a film may be deposited by ion-assisted co-deposition techniques in which the concentration of the higher refractive index material is periodically varied according to the period required to produce the desired filter. The glass of which the rugate filter is formed has an average refractive index which does not vary with temperature by more than 10.sup.-6 /.degree.C. By reflecting light at the peak wavelength back into the laser, the laser is caused to emit at the desired wavelength. Since the rugate filter selectively reflects light within a narrow band of the desired wavelength, the laser emits light within a narrow peak on the order of 10 .ANG. or less.

Rugate filter on diode laser for temperature stabilized emission

The present invention proposes a dielectric waveguide formed on a substrate of ultra-low thermal expansion glass which is assembled with a commercially available diode laser to create a temperature stabilized laser. The waveguide comprises multiple dielectric films which have equal and opposite temperature induced changes in refractive index with respect to each other into which is formed a Bragg grating, the grooves of which are sufficiently shallow to allow penetration of light into the waveguide of 1 mm to 1 cm. This provides a signal which is both narrowband and frequency stable so that the optical signal can be guaranteed to remain in a given narrow frequency band. The dielectric layers are deposited using ion assisted deposition (IAD) to provide uniform, high density films with reduced index-temperature coefficients and increased density, resulting in a waveguide with near-zero temperature variations in refractive index. After fabrication, the waveguide is assembled to the diode laser, creating a temperature stabilized laser which operates within 1 .ANG. of the target wavelength over the temperature range from 20.degree. C. to 70.degree. C. In one embodiment a temperature stabilized laser is used to pump a Nd:YAG laser providing a stable, high power optical signal.

Device for compensating for thermal instabilities of laser diodes

At least one optical resonator having a selected optical processing property is formed upon a substrate. Various property resonators may be stacked upon one another so as to share a common optical axis. A resonator typically has a pair of multilayer dielectric or semiconductor mirrors formed on opposite ends of an optical cavity with the mirrors formed in a plane parallel to the substrate surface. Temperature and mechanical stability superior to current technology is thus achievable in the structure. Additional combinations of mirrors, cavities and gratings may be formed in conjunction with the resonator.

Optical resonator structures

A semiconductor diode laser is aligned to a waveguide with two sections, a first section being a passive low-loss waveguide and a second section being a Bragg grating. The first section works to increase the total cavity length l of the laser by about 1 to 2 cm. The lengthening of the cavity reduces the longitudinal mode spacing .DELTA..lambda. according to the equation .DELTA..lambda.=.lambda..sup.2 /2nl, and provides a higher average output power level because it is substantially immune to mode hop-induced fluctuations. The second section causes the output to be centered at the desired wavelength depending on the grating spacing. An array of diode lasers with an array of waveguides as described above provides a high power source with a controlled bandwidth. The high power laser array with stabilized output wavelength is used to pump a solid state laser crystal.

High power laser array with stable wavelength

An apparatus for generating a variable wavelength optical signal. The apparatus includes a signal generator for generating an optical signal. A reflector receives a portion of the optical signal and an electrical tuning signal. The reflector is responsive to the optical and tuning signals, reflecting a selected spectral component of the optical signal back to the signal generator. The generator receives the selected spectral component and responds by stabilizing the wavelength of its output at the wavelength of the spectral component.

Wavelength tunable diode laser

An optical modulator for generating an amplitude modulated optical signal. A signal generator generates an optical signal that is optically coupled to a tunable filter which shares a common optical axis with the signal generator. The tunable filter wavelength response varies in response to an electrical input control signal thereby providing an output amplitude modulated optical signal. An optical isolator is located between and shares a common optical axis with the signal generator and the tunable filter. The optical isolator is for preventing optical signals originating at the filter, traveling toward the signal generator, from impinging on the signal generator.

Wide linear dynamic range optical modulator

An array of optical RF bandpass filters which is fabricated from planar waveguides on a single substrate. The array of filters receives an input of frequency multiplexed optical signals and separates the intensity modulated optical signal of the desired frequency from signals at other frequencies. Each bandpass filter comprises a resonant cavity formed from a segment of a planar optical waveguide with mirrors deposited at each end. By using ultra high purity CVD techniques common in the optical fiber industry, material absorption is dramatically reduced. Much thicker waveguides are grown than those conventionally fabricated, allowing the use of refractive index differences between waveguide and cladding which are much smaller than those normally used in planar waveguides. To enable the fabrication of a monolithic array of filters having differing center frequencies, the substrate is cut at an angle so that resonant cavities of different lengths are formed.

Monolithic array of fiber optic bandpass filters

The feedback control loop for temperature stabilization of a tunable diode laser consists of a series of lenses or gratings and a detector array disposed in the optical path. The lenses or gratings of the feedback loop are formed in a planar optical waveguide which is temperature stabilized, being fabricated from a plurality of dielectric materials which have approximately equal and opposite changes in refractive index with temperature. Light from a tunable diode laser is input into the loop and is collimated, deflected, and focused onto a portion of the detector array depending on the wavelength of the light. Each detector within the array corresponds to a given wavelength. The detector converts the detected wavelength into an electrical signal which is fed back to the laser phase control to provide tuning to the desired channel.

Monolithic temperature stabilized optical tuning circuit for channel

A laser fabricated from a substrate having top and bottom surfaces. A first stack of mirror layers of alternating different refractive indices are formed upon the substrate top surface. An active layer defining a mesa is formed on top of the first stack of mirror layers. A second stack of alternating different refractive indices mirror layers are formed upon the active layer mesa. A current confinement layer is formed about the side of the active laser mesa. A first contact is formed upon the substrate bottom surface while a second contact is formed upon a portion of said active layer remote from the active layer mesa.

Surface emitting laser

A semiconductor laser for emitting light transverse to the direction of current injection. The laser is fabricated from a substrate having planar top and bottom surfaces and an aperture formed therebetween. An optical cavity, formed upon the substrate top surface and aligned with the aperture, has co-planar top and bottom surfaces with dielectric mirrors formed thereupon. Contacts are formed adjacent the optical cavity for conducting current through the optical cavity in a direction substantially parallel to the optical cavity top and bottom surfaces. Current confinement layers are disposed in intimate contact with the optical cavity for confining current flowing in the optical cavity along a predetermined path extending between the contacts.

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San Diego, CA, United States of America

Eric M Bradley