1,045 research outputs found
Efficiency of evanescent excitation and collection of spontaneous Raman scattering near high index contrast channel waveguides
info:eu-repo/semantics/publishe
High index contrast photonic platforms for on-chip Raman spectroscopy
Nanophotonic waveguide enhanced Raman spectroscopy (NWERS) is a sensing technique that uses a highly confined waveguide mode to excite and collect the Raman scattered signal from molecules in close vicinity of the waveguide. The most important parameters defining the figure of merit of an NWERS sensor include its ability to collect the Raman signal from an analyte, i.e. "the Raman conversion efficiency" and the amount of "Raman background" generated from the guiding material. Here, we compare different photonic integrated circuit (PIC) platforms capable of on-chip Raman sensing in terms of the aforementioned parameters. Among the four photonic platforms under study, tantalum oxide and silicon nitride waveguides exhibit high signal collection efficiency and low Raman background. In contrast, the performance of titania and alumina waveguides suffers from a strong Raman background and a weak signal collection efficiency, respectively
Single mode waveguide platform for spontaneous and surface-enhanced on-chip Raman spectroscopy
We review an on-chip approach for spontaneous Raman spectroscopy and surface-enhanced Raman spectroscopy based on evanescent excitation of the analyte aswell as evanescent collection of the Raman signal using complementary metal oxide semiconductor (CMOS)-compatible single modewaveguides. The signal is either directly collected fromthe analyte molecules or via plasmonic nanoantennas integrated on top of thewaveguides. Flexibility in the design of the geometry of the waveguide, and/or the geometry of the antennas, enables optimization of the collection efficiency. Furthermore, the sensor can be integrated with additional functionality (sources, detectors, spectrometers) on the same chip. In this paper, the basic theoretical concepts are introduced to identify the key design parameters, and some proof-of-concept experimental results are reviewed
Diamond Integrated Optomechanical Circuits
Diamond offers unique material advantages for the realization of micro- and
nanomechanical resonators due to its high Young's modulus, compatibility with
harsh environments and superior thermal properties. At the same time, the wide
electronic bandgap of 5.45eV makes diamond a suitable material for integrated
optics because of broadband transparency and the absence of free-carrier
absorption commonly encountered in silicon photonics. Here we take advantage of
both to engineer full-scale optomechanical circuits in diamond thin films. We
show that polycrystalline diamond films fabricated by chemical vapour
deposition provide a convenient waferscale substrate for the realization of
high quality nanophotonic devices. Using free-standing nanomechanical
resonators embedded in on-chip Mach-Zehnder interferometers, we demonstrate
efficient optomechanical transduction via gradient optical forces. Fabricated
diamond resonators reproducibly show high mechanical quality factors up to
11,200. Our low cost, wideband, carrier-free photonic circuits hold promise for
all-optical sensing and optomechanical signal processing at ultra-high
frequencies
Monolithic Integration of a Plasmonic Sensor with CMOS Technology
Monolithic integration of nanophotonic sensors with CMOS detectors can transform the laboratory based nanophotonic sensors into practical devices with a range of applications in everyday life. In this work, by monolithically integrating an array of gold nanodiscs with the CMOS photodiode we have developed a compact and miniaturized nanophotonic sensor system having direct electrical read out. Doing so eliminates the need of expensive and bulky laboratory based optical spectrum analyzers used currently for measurements of nanophotonic sensor chips. The experimental optical sensitivity of the gold nanodiscs is measured to be 275 nm/RIU which translates to an electrical sensitivity of 5.4 V/RIU. This integration of nanophotonic sensors with the CMOS electronics has the potential to revolutionize personalized medical diagnostics similar to the way in which the CMOS technology has revolutionized the electronics industry
Integrated nanophotonic waveguide-based devices for IR and Raman gas spectroscopy
On-chip devices for absorption spectroscopy and Raman spectroscopy have been developing rapidly in the last few years, triggered by the growing availability of compact and affordable tunable lasers, detectors, and on-chip spectrometers. Material processing that is compatible with mass production has been proven to be capable of long low-loss waveguides of sophisticated designs, which are indispensable for high-light–analyte interactions. Sensitivity and selectivity have been further improved by the development of sorbent cladding. In this review, we discuss the latest advances and challenges in the field of waveguide-enhanced Raman spectroscopy (WERS) and waveguide infrared absorption spectroscopy (WIRAS). The development of integrated light sources and detectors toward miniaturization will be presented, together with the recent advances on waveguides and cladding to improve sensitivity. The latest reports on gas-sensing applications and main configurations for WERS and WIRAS will be described, and the most relevant figures of merit and limitations of different sensor realizations summarized
Nanophotonic waveguide enhanced Raman spectroscopy of biological submonolayers
Characterizing a monolayer of biological molecules has been a major
challenge. We demonstrate nanophotonic wave-guide enhanced Raman spectroscopy
(NWERS) of monolayers in the near-infrared region, enabling real-time
measurements of the hybridization of DNA strands and the density of
sub-monolayers of biotin-streptavidin complex immobilized on top of a photonics
chip. NWERS is based on enhanced evanescent excitation and collection of
spontaneous Raman scattering near nanophotonic waveguides, which for a one
centimeter silicon nitride waveguide delivers a signal that is more than four
orders of magnitude higher in comparison to a confocal Raman microscope. The
reduced acquisition time and specificity of the signal allows for a
quantitative and real-time characterization of surface species, hitherto not
possible using Raman spectroscopy. NWERS provides a direct analytic tool for
monolayer research and also opens a route to compact microscope-less
lab-on-a-chip devices with integrated sources, spectrometers and detectors
fabricated using a mass-producible CMOS technology platform
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