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Obtaining Uniform Polarization From GaAs Laser Arrays

IP.com Disclosure Number: IPCOM000075869D
Original Publication Date: 1971-Dec-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Shelton, CF: AUTHOR [+2]

Abstract

Light from GaAs laser arrays is normally not polarized in a unique plane. Instead, the polarization varies in orientation among all of the lasers. Discussed below is a method of fabrication of laser arrays which yields a unique plane of polarization for every laser.

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Obtaining Uniform Polarization From GaAs Laser Arrays

Light from GaAs laser arrays is normally not polarized in a unique plane. Instead, the polarization varies in orientation among all of the lasers. Discussed below is a method of fabrication of laser arrays which yields a unique plane of polarization for every laser.

Fig. 1 shows one configuration. One end of the array is cut in the form of a 90 degrees "rooftop." In optical contact with the rooftop is a material whose refractive index lies between 0.71 and 0.72 of the refractive index of GaAs (i.e. an absolute index between about 2.48 and 2.52). For this range of indices there is a narrow range of angles for light incident on one face of the rooftop, which will permit propagation of laser light through the structure without excessive losses. This range can be identified by examining Fig. 2, which is a plot of the reflection coefficient as a function of angle of incidence for light incident on such a structure. At 45 degrees incidence, the perpendicular component (R1) of polarization is 70% reflected and after looping around the rooftop, 50% passes back through the cavity. The parallel component (R11) is 50% reflected, and only 25% gets back into the cavity. This represents a 2:1 discrimination in reflectivity for the most probable direction of the light beam. At 44 degrees or 46 degrees incidence, the ratio is about 2.2:1 and at 43 degrees or 47 degrees, the ratio is about 2.7:1. Beyond this angle neither pola...