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Browse Prior Art Database

Laser Diode Angular Orientation Sensing Technique

IP.com Disclosure Number: IPCOM000103056D
Original Publication Date: 1990-May-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 44K

Publishing Venue

IBM

Related People

Luecke, F: AUTHOR

Abstract

Disclosed is a method for sensing the angular orientation of a diode laser chip without requiring that power be applied to the diode laser.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

Laser Diode Angular Orientation Sensing Technique

      Disclosed is a method for sensing the angular orientation of a
diode laser chip without requiring that power be applied to the diode
laser.

      As shown in the figure, a diode laser assembly consists of a
laser chip bonded to a base and sealed behind a glass window. A power
monitor photodiode is mounted behind the laser chip to sense the
light emerging from the back facet of the laser. This detector is
placed at a large angle with respect to the laser, to reduce feedback
of light.

      To sense the alignment of the chip, the light from an external
HeNe alignment laser is directed toward the diode laser; the
direction of the light reflected from the exit facet of the chip
indicates the chip's angular orientation.

      The diode laser cover window also reflects the alignment
laser's light in a direction nominally the same as that of the diode
laser itself.  These two beams are easily distinguishable due to the
existence of a distinctive Fraunhofer diffraction pattern only in the
beam reflected from the diode laser chip, due to the small size of
the chip.

      The light from the alignment laser also may reflect from the
face of the monitor diode, but that reflection is distinguishable by
its large angle: the laser chip position may vary by a few degrees,
while the monitor diode is angled about 15 degrees off axis.

      Disclosed anonymously.