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Waveguide Up-conversion Lasers using Evanescent Wave Coupling

IP.com Disclosure Number: IPCOM000116080D
Original Publication Date: 1995-Aug-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 112K

Publishing Venue

IBM

Related People

Lenth, W: AUTHOR [+2]

Abstract

Disclosed is a device configuration for up-conversion waveguide lasers in which the active laser medium is in the form of a doped bulk crystal or glass substrate on which is placed a thin film, planar or ridge optical waveguide. The system is pumped by launching a pump beam in the guide and exciting the laser-active substrate by the evanescent field of this pump light that penetrates into the substrate. Using this scheme a much wider range of materials is available for device fabrication than would be the case if the waveguide itself was required to consist of the laser-active medium. Examples of materials suitable for this application are given.

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Waveguide Up-conversion Lasers using Evanescent Wave Coupling

      Disclosed is a device configuration for up-conversion waveguide
lasers in which the active laser medium is in the form of a doped
bulk crystal or glass substrate on which is placed a thin film,
planar or ridge optical waveguide.  The system is pumped by launching
a pump beam in the guide and exciting the laser-active substrate by
the evanescent field of this pump light that penetrates into the
substrate.  Using this scheme a much wider range of materials is
available for device fabrication than would be the case if the
waveguide itself was required to consist of the laser-active medium.
Examples of materials suitable for this application are given.
Waveguide up-conversion lasers can potentially provide compact,
low-cost, low-threshold sources of coherent radiation in the
blue/green spectral region with applications in optical data storage
and medical technology.

      Up-conversion lasers have been demonstrated to be efficient
sources of blue/green coherent light in bulk crystals at low
temperatures (1-6) and in long (~1m) glass fibers at room
temperature.  A waveguide in conjunction with a crystalline material
can potentially combine the advantages of compact size, high peak
stimulated emission cross-sections, and better thermal properties of
a crystal with the high excitation density and longer gain length
that can be obtained in a guided configuration.  This is particularly
advantageous for up-conversion lasers given their nonlinear pumping
scheme.  The fabrication of active crystalline waveguides is
difficult, however.  Proposed here is the use of an active substrate
consisting of a bulk laser material and applying a waveguiding
structure to the surface of this material for the purpose of pumping
it via a laser beam launched into the guide.  The waveguide need not
be a single crystal material and it does not contain the active
dopant ions.  This simplifies greatly the fabrication and allows a
wide range of laser media to be used that could not themselves be
fabricated in a waveguide geometry.

      In this invention, it is proposed to deposit one or more
laser-inactive waveguide layer(s) such as Al(2)O(3),
Ta(2)O(5)/SiO(2), PbF(2) or LaF(3) on a rare-earth doped
up-conversion laser material so that the pump and laser fields guided
by the top layer extend into the laser-active substrate which acts as
the absorber of the pump light and as the laser gain medium.  The
refractive index of the guiding layer must be greater than that of
the substrate.  In this concept, the up-conversion laser material and
the waveguide layer are separated and can be optimized almost
independently.  There are many optical materials with refractive
indexes suited for waveguide formation on several types of rare-earth
doped fluoride crystals which are particularly attractive laser
materials due to their fairly narrow linewidth, high peak absorption
and emission cross secti...