15,413 research outputs found
Self-Assembled Conjugated Organic/Polymer Microcavities for Optical Resonators and Lasers
Optical microcavities play an important role for the next-generation light technology.
Recently, we succeeded in fabricating spherical microcavities from Ï-conjugated
polymers (CPs) by simple self-assembly process (Fig. 1).[1] We found that the
microcavities show whispering gallery mode (WGM) resonant photoluminescence
(PL) upon focused laser excitation, where PL generated inside the sphere is confined
via total internal reflection at the polymer/air interface.[2â8] The resonance occurs
when the wavelength of the light is an integer multiple of the circumference of the
microsphere. The CP-based microcavities have benefits to the conventional
microcavities in the following points: [1] simple and low-energy fabrication process to
obtain well-defined microspheres, [2] the microcavities function as both cavity and
emitter, [3] the microcavities have high refractive index and photoabsorptivity, and [4]
potent use for electrically-driven WGM and laser oscillation. In this presentation,
recent results on the fundamentals
of the self-assembly of the CPs,
resonant PL from the CP
microspheres, intra- and
intersphere light energy
conversion, and the future
prospects to realize light-,
electrically-, and chemically-driven
WGM and lasing will be presented.Universidad de MĂĄlaga. Campus de Excelencia Internacional AndalucĂa Tech
Polariton Condensation and Lasing
The similarities and differences between polariton condensation in
microcavities and standard lasing in a semiconductor cavity structure are
reviewed. The recent experiments on "photon condensation" are also reviewed.Comment: 23 pages, 6 figures; Based on the book chapter in Exciton Polaritons
in Microcavities, (Springer Series in Solid State Sciences vol. 172), V.
Timofeev and D. Sanvitto, eds., (Springer, 2012
Theoretical and experimental study of stimulated and cascaded Raman scattering in ultra-high-Q optical microcavities
Stimulated Raman scattering (SRS) in ultra-high-Q surface-tension-induced
spherical and chip-based toroid microcavities is considered both theoretically
and experimentally. These microcavities are fabricated from silica, exhibit
small mode volume (typically 1000 ) and possess whispering-gallery
type modes with long photon storage times (in the range of 100 ns),
significantly reducing the threshold for stimulated nonlinear optical
phenomena. Oscillation threshold levels of less than 100 % -Watts of
launched fiber pump power, in microcavities with quality factors of 100 million
are observed. Using a steady state analysis of the coupled-mode equations for
the pump and Raman whispering-gallery modes, the threshold, efficiencies and
cascading properties of SRS in UHQ devices are derived. The results are
experimentally confirmed in the telecommunication band (1550nm) using tapered
optical fibers as highly efficient waveguide coupling elements for both pumping
and signal extraction. The device performance dependence on coupling, quality
factor and modal volume are measured and found to be in good agreement with
theory. This includes analysis of the threshold and efficiency for cascaded
Raman scattering. The side-by-side study of nonlinear oscillation in both
spherical microcavities and toroid microcavities on-a-chip also allows for
comparison of their properties. In addition to the benefits of a wafer-scale
geometry, including integration with optical, electrical or mechanical
functionality, microtoroids on-a-chip exhibit single mode Raman oscillation
over a wide range of pump powers.Comment: 12 pages, 15 figure
Demonstration of ultra-high-Q small mode volume toroid microcavities on a chip
Optical microcavities confine light spatially and temporally and find
application in a wide range of fundamental and applied studies. In many areas,
the microcavity figure of merit is not only determined by photon lifetime (or
the equivalent quality-factor, Q), but also by simultaneous achievement of
small mode volume V . Here we demonstrate ultra-high Q-factor small mode volume
toroid microcavities on-a-chip, which exhibit a Q/V factor of more than
. These values are the highest reported to date for any
chip-based microcavity. A corresponding Purcell factor in excess of 200 000 and
a cavity finesse of is achieved, demonstrating that toroid
microcavities are promising candidates for studies of the Purcell effect,
cavity QED or biochemical sensingComment: 4 pages, 3 figures, Submitted to Applied Physics Letter
Resonant self-pulsations in coupled nonlinear microcavities
A novel point of view on the phenomenon of self-pulsations is presented,
which shows that they are a balanced state formed by two counteracting
processes: beating of modes and bistable switching. A structure based on two
coupled nonlinear microcavities provides a generic example of system with
enhanced ability to this phenomenon. The specific design of such structure in
the form of multilayered media is proposed, and the coupled mode theory is
applied to describe its dynamical properties. It is emphasized that the
frequency of self-pulsations is related to the frequency splitting between
resonant modes and can be adjusted over a broad range.Comment: 5 pages, 4 figure
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