1,521 research outputs found
Ideality in a fiber-taper-coupled microresonator system for application to cavity quantum electrodynamics
The ability to achieve near lossless coupling between a waveguide and a resonator is fundamental to many quantum-optical studies as well as to practical applications of such structures. The nature of loss at the junction is described by a figure of merit called ideality. It is shown here that under appropriate conditions ideality in excess of 99.97% is possible using fiber-taper coupling to high-Q silica microspheres. To verify this level of coupling, a technique is introduced that can both measure ideality over a range of coupling strengths and provide a practical diagnostic of parasitic coupling within the fiber-taper-waveguide junction
Photonic Crystal Nanocavities and Waveguides
Fabrication of optical structures has evolved to a precision which allows us to control light within etched nanostructures. Nano-optic cavities can be used for efficient and flexible concentration of light in small volumes, and control over both emission wavelength and frequency. Conversely, if a periodic pattern is defined in the top semitransparent metal layer by lithography, it is possible to efficiently couple out the light out of a semiconductor and to simultaneously enhance the spontaneous emission rate. Here we demonstrate the use of photonic crystals for efficient light localization and light extraction
Adiabatic self-tuning in a silicon microdisk optical resonator
We demonstrate a method for adiabatically self-tuning a silicon microdisk resonator. This mechanism is not only able to sensitively probe the fast nonlinear cavity dynamics, but also provides various optical functionalities like pulse compression, shaping, and tunable time delay
Photonic Crystals and their Applications to Efficient Light Emitters
When combined with high index contrast slabs in which light can be efficiently guided, microfabricated two-dimensional photonic bandgap mirrors provide us with the geometries needed to confine and concentrate light into extremely small volumes and to obtain very high field intensities. Fabrication of optical structures has now evolved to a precision which allows us to control light within such etched nanostructures. Sub-wavelength nano-optic cavities can be used for efficient and flexible control over both emission wavelength and frequency, and nanofabricated optical waveguides can be used for efficient coupling of light between devices. The reduction of the size of optical components leads to their integration in large numbers and the possibility to combine different functionalities on a single chip. We show uses of such crystals in functional nonlinear optical devices, such as lasers, modulators, add/drop filters, polarizers and detectors
Use of combinatorial analysis for the study of new material for solar cells applications
This paper presents a combinatorial method for the deposition and
characterization of new metallic precursors for photovoltaic materials.
Onedimensional thin film alloy “libraries” were electrodeposited on Mo-coated
glass. The library elements were deposited in two consecutive baths and then
heated in a reducing atmosphere to promote interdiffusion of the elements. At
the end of this process, the libraries possessed a composition gradient along
their lengths, with single elements at their two opposite ends and one or more
alloys and/or a solid state solution in between. This continuous range of
compositions can therefore be considered a collection of specific precursors
that can be interrogated by examining their corresponding locations, with the
crystallographic structure along the library changing in accordance with the
phase diagram for the metals. The libraries were then sulphurised or selenised
by heating in a sulphur-rich or selenium rich atmosphere; this converted the
metallic precursors in a continuous range of materials, candidates for potential
solar cells absorbers. The libraries were analysed by X-ray diffraction and
energy dispersive X-ray spectrometry. The X-ray diffraction results show phase
changes across the libraries, which can be correlated with the original
precursor concentration at that particular p
A proposal for highly tunable optical parametric oscillation in silicon micro-resonators
We propose a novel scheme for continuous-wave pumped optical parametric oscillation (OPO) inside silicon micro-resonators. The proposed scheme not only requires a relative low lasing threshold, but also exhibits extremely broad tunability extending from the telecom band to mid infrared
An optical fiber-taper probe for wafer-scale microphotonic device characterization
A small depression is created in a straight optical fiber taper to form a
local probe suitable for studying closely spaced, planar microphotonic devices.
The tension of the "dimpled" taper controls the probe-sample interaction length
and the level of noise present during coupling measurements. Practical
demonstrations with high-Q silicon microcavities include testing a dense array
of undercut microdisks (maximum Q = 3.3x10^6) and a planar microring (Q =
4.8x10^6).Comment: 8 pages, 5 figures, for high-res version see
http://copilot.caltech.edu/publications/index.ht
Measurement of spontaneous emission from a two-dimensional photonic band gap defined microcavity at near-infrared wavelengths
An active, photonic band gap-based microcavity emitter in the near infrared is demonstrated. We present direct measurement of the spontaneous emission power and spectrum from a microcavity formed using a two-dimensional photonic band gap structure in a half wavelength thick slab waveguide. The appearance of cavity resonance peaks in the spectrum correspond to the photonic band gap energy. For detuned band gaps, no resonances are observed. For devices with correctly tuned band gaps, a two-time enhancement of the extraction efficiency was demonstrated compared to detuned band gaps and unpatterned material
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