International Business Machines Corporation

Binoptics Corporation

Wilfried Lenth

Alex A Behfar

William P Risk, Iii

William J Kozlovsky

Daniel Rugar

Christoph S Harder

Gary C Bjorklund

Heinz P Meier

Franklin M Schellenberg

Anthony G Dewey

Jean-Claude J Baumert

A method and structure for producing lasers having good optical wavefront characteristics, such as are needed for optical storage includes providing a laser wherein an output beam emerging from the laser front facet is essentially unobstructed by the edges of the semiconductor chip in order to prevent detrimental beam distortions. The semiconductor laser structure is epitaxially grown on a substrate with at least a lower cladding layer, an active layer, an upper cladding layer, and a contact layer. Dry etching through a lithographically defined mask produces a laser mesa of length land width b. Another sequence of lithography and etching is used to form a ridge structure with width w on top of the mesa. The etching step also forming mirrors, or facets, on the ends of the laser waveguide structures. The length land width bof the chip can be selected as convenient values equal to or longer than the waveguide length land mesa width b, respectively. The waveguide length and width are selected so that for a given defect density D, the yield Yis larger than 50%.

Low cost InGaAlN based lasers

A method and structure for producing lasers having good optical wavefront characteristics, such as are needed for optical storage includes providing a laser wherein an output beam emerging from the laser front facet is essentially unobstructed by the edges of the semiconductor chip in order to prevent detrimental beam distortions. The semiconductor laser structure is epitaxially grown on a substrate with at least a lower cladding layer, an active layer, an upper cladding layer, and a contact layer. Dry etching through a lithographically defined mask produces a laser mesa of length land width b. Another sequence of lithography and etching is used to form a ridge structure with width won top of the mesa. The etching step also forming mirrors, or facets, on the ends of the laser waveguide structures. The length land width bof the chip can be selected as convenient values equal to or longer than the waveguide length land mesa width b, respectively. The waveguide length and width are selected so that for a given defect density D, the yield Yis larger than 50%.

Low cost InGaAIN based lasers

A semiconductor laser apparatus comprises a DC power supply coupled with an RF source which generates a low-amplitude RF current which is injected into a diode laser source. An optical beam shaping system processes the laser beam and directs it to a nonlinear resonator having a plurality of longitudinal resonator frequencies with a fundamental spatial mode. The nonlinear resonator uses a phase-matched, second harmonic generation (SHG) process to generate a second laser beam by frequency doubling the central carrier frequency of the diode laser source, and further reflects a portion of the incident laser beam to an electronic resonance locking system. The electronic resonance locking system has a photodetector to receive the reflected portion of the incident beam from the resonator and generates an RF signal arising from the difference in phase shifts or amplitude losses experienced by the RF sidebands. An RF mixer receives the RF signal from the photodetector and an input from the RF source to generate an error signal as a feedback signal which is supplied to the diode laser source for tuning the laser injection current.

Diode laser frequency doubling using nonlinear crystal resonator with

An apparatus and method is described for detecting focus errors in an optical head by positioning a prism in the optical path of a return light beam reflected from an optical recording medium. The prism reduces the beam in one dimension by a factor of M and concurrently increases the divergence/convergence angle associated with a focus-error of the beam by a factor of M in this dimension, thereby desirably enhancing the focus error signal by a factor of M.sup.2. A focus error is detected by a segmented photodetector having inner and outer photosensitive regions. The photodetector generates an electrical signal indicative of the focus error from the difference in light intensities at the inner and outer regions. The photodetector preferably is segmented in such manner as to also provide a track error signal.

Focus-error detection using prism-enhanced spot size monitoring

A laser diode produces a laser beam having a carrier frequency component and a sideband frequency component. An optical resonator receives the laser beam and substantially couples the carrier frequency component and substantially rejects the sideband frequency component. An electronic locking system receives the rejected sideband frequency component and adjusts the laser diode to lock the carrier frequency component to the resonator frequency. A laser control controls the allocation of power between the carrier frequency and the sideband frequency component such that the resonator output may be controlled and pulsed.

Laser system and method

Apparatus and method for producing coherent blue-green-light radiation having a wavelength of essentially 490-500 nm. A diode laser, such as a strained-layer InGaAs/GaAs diode laser, provides a 980-1,000 nm beam, and a nonlinear crystal of KTP produces coherent radiation by noncritically phase-matched second-harmonic generation (SHG) of said beam. The beam preferably has a wavelength of essentially 994 nm for generating radiation having a wavelength of essentially 497 nm. The crystal is disposed within an optical resonator and the frequency of the laser is locked to that of the resonator. Alternatively, two diode lasers are oriented to provide orthogonally polarized beams each with a wavelength of 980-1,000 nm but within essentially 1 nm of each other, and the KTP crystal is oriented with its a- and c-axis parallel to the orthogonally polarized beams. The KTP crystal may have an associated optical waveguide along which the beam is propagated to enhance SHG efficiency.

Miniature blue-green laser source using second-harmonic generation

A laser diode with a low reflectivity output facet provides infrared light to a nonlinear crystal resonator such that a portion of the infrared light is converted to blue light. A mirror is located on the opposite side of the nonlinear crystal resonator from the laser. The mirror allows the blue light to pass, but reflects the infrared light exiting the resonator back through the resonator and into the laser diode. The laser diode is thereby locked at the resonance frequency of the nonlinear crystal resonator.

Laser system and method using a nonlinear crystal resonator

A process and apparatus are disclosed for producing a beam of coherent radiation at essentially 459 nm by mixing, in a nonlinear crystal consisting essentially of KTP, two laser beams, one at essentially 1064 nm and the other at essentially 808 nm. The 1064 nm radiation is derived from a Nd:YAG laser that consists of an input mirror, an output mirror and a Nd:YAG crystal, and contains also the KTP crystal. The Nd:YAG laser is pumped by an essentially 808 nm semiconductor diode laser beam, which passes through the input mirror and through the KTP crystal into the Nd:YAG laser crystal where it is absorbed. The 1064 nm radiation oscillating inside the Nd:YAG laser resonator is mixed either with the said 808 nm pump beam or with 808 nm radiation provided by a second semiconductor diode laser whose light is coupled with the 1064 nm beam using a beamsplitter. The essentially 459 nm beam passes through the output mirror to a utilization device.

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Santa Cruz, CA, United States of America

Wilfried Lenth