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Compact Blue Light Source Based on Waveguide Frequency Doubling of Semiconductor Diode Laser

IP.com Disclosure Number: IPCOM000115644D
Original Publication Date: 1995-Jun-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 95K

Publishing Venue

IBM

Related People

Kozlovsky, W: AUTHOR [+4]

Abstract

This invention discloses a practical means for integrating a semiconductor diode laser with a frequency doubling waveguide. A frequency doubling waveguide using the technique of "quasi-phasematching" typically has a bandwidth for efficient second harmonic generation of 1 Angstrom for a 1-cm-long waveguide. Hence, frequency stability of the laser diode must be insured by preventing the destabilizing effects of optical feedback, and the wavelength of the laser must be precisely tuned and maintained within the phasematching band.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Compact Blue Light Source Based on Waveguide Frequency Doubling of
Semiconductor Diode Laser

      This invention discloses a practical means for integrating a
semiconductor diode laser with a frequency doubling waveguide.  A
frequency doubling waveguide using the technique of
"quasi-phasematching" typically has a bandwidth for efficient second
harmonic generation of 1 Angstrom for a 1-cm-long waveguide.  Hence,
frequency stability of the laser diode must be insured by preventing
the destabilizing effects of optical feedback, and the wavelength of
the laser must be precisely tuned and maintained within the
phasematching band.

      This invention addresses these problems as follows: (1)
Destabilization of the laser diode due to optical feedback is
eliminated by anti-reflection coating both the laser diode facet and
the waveguide input facet.  The reflectivity necessary to cause
lasing is provided by Fig. 1 either (a) a reflective coating on the
output facet of the waveguide, (b) an external mirror or grating, (c)
the distributed reflection from the periodic refractive index
variations of the quasi-phasematched waveguide or (d) a separate
grating reflector integrated on the same substrate as the frequency
doubling waveguide.  In the latter three cases, the output facet of
the waveguide is also anti-reflection-coated.

      The wavelength of the laser is tuned to coincide with the
phasematching wavelength of the frequency doubling waveguide using
temperature tuning.  Both the laser diode chip and the waveguide chip
are affixed to a common submount.  Since the temperature tuning rates
of laser wavelength and the phasematching wavelength are different,
there is some temperature at which the two coincide.  Thus, by
adjusting the temperature of the common submount, the laser
wavelength can be tuned to the phasematching wavelength.

      For stable blue output, it is necessary to generate some servo
signal indicative of the difference between the laser w...