Microfluidic directional emission control of an azimuthally polarized radial fiber laser.
Applications of this invention range from flexible multidirectional displays to minimally invasive directed light delivery systems for medical applications.
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.
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.
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