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CONVERSION OF PULSED GAIN GUIDED LASERS TO CW INDEX GUIDED LASERS BY CONTROLLED THERMAL HEATING

IP.com Disclosure Number: IPCOM000025529D
Original Publication Date: 1985-Dec-31
Included in the Prior Art Database: 2004-Apr-04
Document File: 2 page(s) / 104K

Publishing Venue

Xerox Disclosure Journal

Abstract

Recently, it has been observed that lasers designed to be gain guided in nature may exhibit index guiding attributes at high duty cycle or continuous wave (CW) operation. It is theorized that one or more regions of high resistance exist adjacent to or in proximity to the active region of the laser. Because of these high resistance regions, local heating causes the bandgap outside or near the active region to decrease and, consequently, the index of refraction decreases. The decrease in bandgap reduces current spreading and the decrease in refractive index produces index guiding, so long as the optical of the propagating radiation of the laser penetrates the region in which the refractive index has changed.

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XEROX DISCLOSURE JOURNAL

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CONVERSION OF PULSED GAIN GUIDED Proposed Classification LASERS TO CW INDEX GUIDED LASERS U.S. CI. 372/45
BY CONTROLLED THERMAL HEATING Int. C1. HOls 3/19 Robert D. Burnharn
Harlan Chung

DOUBLE HETEROSTRUCTURE LASER 10

22 26 24 I 22

I I

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FIG. I

Recently, it has been observed that lasers designed to be gain guided in nature may exhibit index guiding attributes at high duty cycle or continuous wave (CW) operation. It is theorized that one or more regions of high resistance exist adjacent to or in proximity to the active region of the laser. Because of these high resistance regions, local heating causes the bandgap outside or near the active region to decrease and, consequently, the index of refraction decreases. The decrease in bandgap reduces current spreading and the decrease in refractive index produces index guiding, so long as the optical of the propagating radiation of the laser penetrates the region in which the refractive index has changed.

Shown in Figure 1 in enlarged form is a conventional double heterostructure gain guided laser 10 comprising, for example, substrate 12 of n-GaAs upon which are epitaxially deposited cladding layer 14 of n-Gal-yAlyAs, active region 16 of GaAs cladding layer 18 of p-Gal-xA1xAs and cap layer 20 of pf-GaAs. A proton implant 22 is formed through cap layer 20 into cladding layer 18 delineating a

Volume 10 Number 6 November/December 1985 363

PROTON lMPLANT CLADDING LAYER

RESISTIVE LAYER

- SUBSTRATE

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CONVERSION OF PULSED GAIN GUIDED LASERS TO CW INDEX GUIDED LASERS BY CONTROLLED THERMAL HEATING (Cont'd)

contact stripe 24. Conventional metal contacts 26 and 28 are provided respectively on the top surface of cap layer 20 and the bottom surface of substrate 12.

We propose the proper location of formed higher resistive layers or regions, such as region 30 in laser 10, to provide an index guiding structure in the crystal body of gai...