Controlled Azimuthal Emission from a Microfluidic Fiber Laser

Technology #15001

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FIG. 1 is a prior art cylindrical structure supporting high-Q whispering-gallery modes.  FIG. 2 is a schematic illustration of an embodiment of the radially emitting fiber laser invention disclosed herein.FIG. 3 is a perspective view of a drawn preform used to make the fiber laser according to one embodiment of the invention.FIG. 4 includes SEM micrographs of the laser fiber structure of an embodiment of the invention.FIG. 5 is a schematic illustration of the microfluidic system used to transport the gain medium within the fiber laser disclosed herein.  FIG. 6 is a plot of plug position versus time for gain medium motion within the fiber.
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Inventors
Professor John Joannopoulos
Department of Physics, MIT
External Link (web.mit.edu)
Professor Yoel Fink
Department of Materials Science and Engineering, MIT
External Link (dmse.mit.edu)
Ofer Shapira
Research Laboratory of Electronics, MIT
Fabien Sorin
Department of Materials Science and Engineering, MIT
Alexander Stolyarov
Lincoln Laboratory, MIT
Lei Wei
Research Laboratory of Electronics, MIT
Managed By
Dave Sossen
MIT Technology Licensing Officer
Patent Protection

Microfluidic radial fiber laser utilizing an external polarizer to modulate its azimuthal intensity distributio

US Patent 8,442,078
Publications
Microfluidic directional emission control of an azimuthally polarized radial fibre laser
Nature Photonics, PUBLISHED ONLINE: 11 MARCH 2012

Microfluidic directional emission control of an azimuthally polarized radial fiber laser.

Applications

Applications of this invention range from flexible multidirectional displays to minimally invasive directed light delivery systems for medical applications.

Problem Addressed

Lasers with cylindrical symmetric polarization states are predominantly based on whispering-gallery modes, characterized by high angular momentum and dominated by azimuthal emission. This results in limited control over the output coupling and diffraction-limited quality factors. Therefore, there is a need for a coherent light source which allows full control over output coupling, zero angular momentum and the potential for scalability without compromising the quality factor.

Technology

The invention includes an optical fiber with a cavity containing a microfluidic gain medium bounded by a composite structure of alternating layers of high and low index materials which forms an axially invariant, rotationally symmetrical photonic bandgap cavity. The optical fiber has a microfluidic channel containing liquid crystal modulators in the fiber cladding extending in an axial direction and a pair of electrodes which flanks the microfluidic channel. An electrical potential across the pair of electrodes will change the linearly polarized state of light emitted from the cavity. Finally, the external linear polarizer surrounding the fiber will modulate  the polarized wavefront emanating from the fiber core, leading to a laser with a dynamically controlled intensity distribution spanning the full azimuthal angular range.

Advantages

  • It allows for full control over output coupling and the potential for scalability to small volumes without compromising the quality factor.
  • The shorter cavity length of these radial modes allows for a larger free spectral range and consequently higher finesse than whispering-gallery modes.