Bell Telephone Laboratories

At&t Bell Laboratories

Richard C Miller

Bertram Schwartz

Louis A Koszi

Richard W Dixon

Robert Guido Chemelli

William Baxter Joyce

Bernard Collins De Loach, Jr

Dwight Dexter Cook

Semiconductor light emitting devices, lasers and LEDs, are described in which the current flow channel is narrower near the top surface of the device and wider at its bottom near the active region. Also, described are several attenuation masks for fabricating the channels of these devices by particle bombardment.

Method of forming current confinement channels in semiconductor devices

Current confinement in semiconductor light emitting devices

A system (FIG. 1) for interrogating the ON-OFF status of an electrical switch (31) comprises a semiconductor body (4) containing a PN junction and means (5) for electrically connecting an auxiliary switch (32) coupled to the interrogated switch, or alternately (FIG. 2) the interrogated switch (32), across the PN junction. Light (7) of a first wavelength incident on the semiconductor body causes light of a second wavelength (11) to be emitted from the body when the switch is open (OFF), whereas no light is emitted from the body when the switch is closed (ON). Therefore, photoelectric detection of the emission vs. non-emission of light of the second wavelength from the semiconductor body indicates the OFF vs. ON status of the switch.

Optical system for interrogation of the status of a switch

The tracking problems of prior art optical monitoring (e.g., feedback stabilization) schemes are substantially alleviated by positioning a photodiode (PD 130) directly in the light path of the optical source (100) to be stabilized. The active (light-absorbing) layer (104) of the PD samples (absorbs) only a small portion of the light beam (140) emanating from the source and converts that portion to a photocurrent used in a feedback loop (120, 101) to control the excitation supplied to the source. The remaining, major portion (140') of the beam is transmitted unabsorbed through the PD active layer to utilization means (e.g., through an optical fiber 108 to a remote receiver). Advantageously, in one embodiment the PD is a double heterostructure (DH) in which the photocurrent is linearly related to the beam intensity. The use of discrete or integrated lens means (110, 110', 164, 166) to enhance coupling from the source to PD is described. In addition, tandem DH-PDs (150, 152) are also described which perform both detection, for demodulating encoded information at one optical frequency, and sampling, for feedback stabilization at another optical frequency.

Optical monitoring photodiode system

Disclosed is an apparatus for recording optical information by means of laser machining of holes on a recording medium. The optical components include a solid state laser, means for converting the light emanating from the laser into a circular beam, and an optical fiber with a graded index of refraction for focusing the light onto the recording medium. The components are mounted on a support arm which is deflected at a rate sufficient to achieve line scan of the medium, while frame scan is achieved by translating either the support arm or the film in a direction essentially perpendicular to the plane of deflection. Means may also be included for displaying the printed information on a screen.

Recording apparatus utilizing small optical components

In a micrographics system of the type in which holes are machined in a thin film by means of a laser (see, for example, reissue U.S. Pat. No. 28,375 of D. Maydan, M. I. Cohen and R. E. Kerwin, granted Mar. 25, 1975), it is advantageous that the laser be a solid-state unit of the stripe-geometry double-heterostructure type. But the optical output beam of such a laser typically exhibits astigmatism and an elliptical cross-section. To assure high-quality machining of the film, it is important that the astigmatic nature of the beam be corrected and, in addition, that the beam be converted to one having a circular cross-section. As described herein, this is accomplished by means of an inexpensive and easily adjustable compact array of optical components that are relatively insensitive to beam-steering and to certain filamentation effects that may occur in the laser.

Growing community of inventors

Summit, NJ, United States of America

Richard C Miller