2,857 research outputs found
Endoscopic optical coherence tomography with a flexible fiber bundle
We demonstrate in vivo endoscopic optical coherence tomography (OCT) imaging
in the forward direction using a flexible fiber bundle. In comparison to
current conventional forward looking probe schemes, our approach simplifies the
endoscope design by avoiding the integration of any beam steering components in
the distal probe end due to 2D scanning of a focused light beam over the
proximal fiber bundle surface. We describe the challenges that arise when OCT
imaging with a fiber bundle is performed, such as multimoding or
cross-coupling. The performance of different fiber bundles with varying
parameters such as numerical aperture, core size and core structure was
consequently compared and artifacts that degrade the image quality were
described in detail. Based on our findings, we propose an optimal fiber bundle
design for endoscopic OCT imaging
Electrically packaged silicon-organic hybrid (SOH) I/Q-modulator for 64 GBd operation
Silicon-organic hybrid (SOH) electro-optic (EO) modulators combine small
footprint with low operating voltage and hence low power dissipation, thus
lending themselves to on-chip integration of large-scale device arrays. Here we
demonstrate an electrical packaging concept that enables high-density
radio-frequency (RF) interfaces between on-chip SOH devices and external
circuits. The concept combines high-resolution
printed-circuit boards with technically simple metal wire bonds and is amenable
to packaging of device arrays with small on-chip bond pad pitches. In a set of
experiments, we characterize the performance of the underlying RF building
blocks and we demonstrate the viability of the overall concept by generation of
high-speed optical communication signals. Achieving line rates (symbols rates)
of 128 Gbit/s (64 GBd) using quadrature-phase-shiftkeying (QPSK) modulation and
of 160 Gbit/s (40 GBd) using 16-state quadrature-amplitudemodulation (16QAM),
we believe that our demonstration represents an important step in bringing SOH
modulators from proof-of-concept experiments to deployment in commercial
environments
Optomechanical transduction of an integrated silicon cantilever probe using a microdisk resonator
Sensitive transduction of the motion of a microscale cantilever is central to
many applications in mass, force, magnetic resonance, and displacement sensing.
Reducing cantilever size to nanoscale dimensions can improve the bandwidth and
sensitivity of techniques like atomic force microscopy, but current optical
transduction methods suffer when the cantilever is small compared to the
achievable spot size. Here, we demonstrate sensitive optical transduction in a
monolithic cavity-optomechanical system in which a sub-picogram silicon
cantilever with a sharp probe tip is separated from a microdisk optical
resonator by a nanoscale gap. High quality factor (Q ~ 10^5) microdisk optical
modes transduce the cantilever's MHz frequency thermally-driven vibrations with
a displacement sensitivity of ~ 4.4x10^-16 m\sqrt[2]{Hz} and bandwidth > 1 GHz,
and a dynamic range > 10^6 is estimated for a 1 s measurement.
Optically-induced stiffening due to the strong optomechanical interaction is
observed, and engineering of probe dynamics through cantilever design and
electrostatic actuation is illustrated
Design and Optimize a Two Color Fourier Domain Pump Probe Optical Coherence Tomography System
Molecular imaging using fluorescence spectroscopy-based techniques is
generally inefficient due to the low quantum yield of most naturally occurring
biomolecules. Current fluorescence imaging techniques tag these biomolecules
chemically or through genetic manipulation, increasing the complexity of the system. A
technique capable of imaging these biomolecules without modifying the chromophore
and/or its environment could provide vital biometric parameters and unique insights into
various biological processes at a molecular level.
Pump probe spectroscopy has been used extensively to study the molecular
properties of poorly fluorescing biomolecules, because it utilizes the known absorption
spectrum of these chromophores. Optical Coherence Tomography (OCT) is an optical
imaging modality that harnesses the power of low coherence interferometry to measure
the 3-D spatially resolved reflectivity of a tissue sample. We plan to develop a new
molecular imaging modality that combines these techniques to provide 3-D, highresolution
molecular images of various important biomolecules. The system uses a Fourier domain OCT setup with a modified sample arm that
combines the "pump" and "probe" beams. The pump beam drives the molecules from
the ground state to excited state and the probe interrogates the population change due to
the pump and is detected interferometrically. The pump and the probe beam
wavelengths are optimized to maximize absorption at the pump wavelength and
maximize the penetration depth at the probe wavelength. The pump-probe delay can be
varied to measure the rate at which the excited state repopulates the ground state, i.e., the
ground state recovery time. The ground state recovery time varies for different
chromophores and can potentially be used to identify different biomolecules.
The system was designed and optimized to increase the SNR of the PPOCT
signals. It was tested by imaging hemoglobin and melanin samples and yielded
encouraging results. Potential applications of imaging hemoglobin using this technique
include the mapping of tissue microvasculature and measuring blood-oxygen saturation
levels. These applications could be used to identify hypoxic areas in tissue. Melanin
imaging can provide means of demarcation of melanoma in various organs such as skin,
eye and intestines
LASER Tech Briefs, Spring 1994
Topics in this Laser Tech Brief include: Electronic Components and Circuits. Electronic Systems, Physical Sciences, Materials, Mechanics, Fabrication Technology, and books and reports
Hybrid integration methods for on-chip quantum photonics
The goal of integrated quantum photonics is to combine components for the generation, manipulation, and detection of nonclassical light in a phase-stable and efficient platform. Solid-state quantum emitters have recently reached outstanding performance as single-photon sources. In parallel, photonic integrated circuits have been advanced to the point that thousands of components can be controlled on a chip with high efficiency and phase stability. Consequently, researchers are now beginning to combine these leading quantum emitters and photonic integrated circuit platforms to realize the best properties of each technology. In this paper, we review recent advances in integrated quantum photonics based on such hybrid systems. Although hybrid integration solves many limitations of individual platforms, it also introduces new challenges that arise from interfacing different materials. We review various issues in solid-state quantum emitters and photonic integrated circuits, the hybrid integration techniques that bridge these two systems, and methods for chip-based manipulation of photons and emitters. Finally, we discuss the remaining challenges and future prospects of on-chip quantum photonics with integrated quantum emitters. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen
Spectral Interferometry with Frequency Combs
In this review paper, we provide an overview of the state of the art in linear interferometric techniques using laser frequency comb sources. Diverse techniques including Fourier transform spectroscopy, linear spectral interferometry and swept-wavelength interferometry are covered in detail. The unique features brought by laser frequency comb sources are shown, and specific applications highlighted in molecular spectroscopy, optical coherence tomography and the characterization of photonic integrated devices and components. Finally, the possibilities enabled by advances in chip scale swept sources and frequency combs are discussed
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