  We demonstrate a novel microcavity-based photon up-conversion using second
harmonic generation (SHG) from a polar nematic fluid media doped with a laser
dye. The present idea is based on coherent light generation via simultaneous
frequency doubling and stimulated emission (lasing) inside a microcavity. The
polar nematic fluid equips very high even-order optical nonlinearity due to the
polar symmetry and large dipole moment along the molecular long axis. At the
same time, its inherent fluidic nature allows us to easily functionalize the
media just by doping, in the present case, with an emissive laser dye. Our
demonstrated system exhibits a giant nonlinear optical response to input light,
while enabling spectral narrowing and multiple-signal output of up-converted
light, that is not attainable though the simple SH-conversion of input light.
Furthermore, susceptibility of the liquid crystal offers dynamic modulation
capabilities under external stimulus, such as signal switching with electric
field application or wavelength tuning through temperature variation. Such a
brand-new type of simple coherent flexible up-conversion system must be
promising as a new principle for easy-accessible and down-scalable wavelength
conversion devices.
