We report on the development of single-frequency VCSELs (vertical-cavity surface-emitting lasers) for sensing the position of a moving MEMS (micro-electro-mechanical system) object with resolution much less than 1nm. Position measurement is the basis of many different types of MEMS sensors, including accelerometers, gyroscopes, and pressure sensors. Typically, by switching from a traditional capacitive electronic readout to an interferometric optical readout, the resolution can be improved by an order of magnitude with a corresponding improvement in MEMS sensor performance. Because the VCSEL wavelength determines the scale of the position measurement, laser wavelength (frequency) stability is desirable. This paper discusses the impact of VCSEL amplitude and frequency noise on the position measurement.
Reducing battery materials to nano-scale dimensions may improve battery performance while maintaining the use of
low-cost materials. However, we need better characterization tools with atomic to nano-scale resolution in order to
understand degradation mechanisms and the structural and mechanical changes that occur in these new materials during
battery cycling. To meet this need, we have developed a micro-electromechanical systems (MEMS)-based platform for
performing electrochemical measurements using volatile electrolytes inside a transmission electron microscope (TEM).
This platform uses flip-chip assembly with special alignment features and multiple buried electrode configurations. In
addition to this platform, we have developed an unsealed platform that permits in situ TEM electrochemistry using ionic
liquid electrolytes. As a test of these platform concepts, we have assembled MnO2 nanowires on to the platform using
dielectrophoresis and have examined their electrical and structural changes as a function of lithiation. These results
reveal a large irreversible drop in electronic conductance and the creation of a high degree of lattice disorder following
lithiation of the nanowires. From these initial results, we conclude that the future full development of in situ TEM
characterization tools will enable important mechanistic understanding of Li-ion battery materials.
We demonstrate chemical/biological sensor arrays based on high quality factor evanescent microring waveguide
resonators in a process that is compatible with CMOS fabrication, glass microfluidic integration, and robust surface
chemistry ligand attachment. We cancel out any fluctuations due to liquid temperature variations through a
differential dual sensor design. Using laser locking servo techniques we attain detection sensitivities in the ng/ml
range. This combination of silicon photonic sensors, robust packaging, high sensitivity and arrayed design is capable
of providing a platform for multiplexed chem-bio sensing of molecules suspended in solution.
We present the theory of operation along with detailed device designs and initial experimental results of a new class of
uncooled thermal detectors. The detectors, termed microphotonic thermal detectors, are based on the thermo-optic effect
in high quality factor (Q) micrometer-scale optical resonators. Microphotonic thermal detectors do not suffer from
Johnson noise, do not require metallic connections to the sensing element, do not suffer from charge trapping effects,
and have responsivities orders of magnitude larger than microbolometer-based thermal detectors. For these reasons,
microphotonic thermal detectors have the potential to reach thermal phonon noise limited performance.
A novel fabrication strategy has produced optical microring-resonator-based thermal detectors. The detectors are based
on the thermo-optic effect and are thermally isolated from a silicon wafer substrate so as to maximize the temperature
excursion for a given amount of incident radiation and minimize the impact of thermal phonon noise. The combination
of high-Q, thermal isolation, and lack of Johnson noise offers thermal microphotonic detectors the potential to achieve
significantly greater room temperature sensitivity than standard bolometric techniques. Several batch fabrication
strategies were investigated for producing thermal microphotonic detectors using waveguide materials such as LPCVD
Silicon Nitride (Si3N4) on Oxide and Silicon on Insulator (SOI). Fabrication challenges and loss reduction strategies will
be presented along with some initial infrared detection results.
The large refractive index difference between silicon nitride and silicon dioxide allows silicon nitride/dioxide waveguides to have a small mode size and low radiation bending loss. Low radiation bending loss enables high quality (Q) factor microring resonators. In this paper, we will present a record high quality factor microring resonator using silicon nitride and silicon dioxide on a silicon wafer. The microring resonator was fabricated using a deep UV photolithography and etching process. The microring resonator was critically coupled to a straight waveguide. An intrinsic quality factor of 240,000 has been measured. We will also present our result of using on-chip high-Q microring resonators for liquid phase chemical sensing application.
Optical waveguide propagation loss due to sidewall roughness, material impurity and inhomogeneity has been the focus of many studies in fabricating planar lightwave circuits (PLC's) In this work, experiments were carried out to identify the best fabrication process for reducing propagation loss in single mode waveguides comprised of silicon nitride core and silicon dioxide cladding material. Sidewall roughness measurements were taken during the fabrication of waveguide devices for various processing conditions. Several fabrication techniques were explored to reduce the sidewall roughness and absorption in the waveguides. Improvements in waveguide quality were established by direct measurement of waveguide propagation loss. The lowest linear waveguide loss measured in these buried channel waveguides was 0.1 dB/cm at a wavelength of 1550 nm. This low propagation loss along with the large refractive index contrast between silicon nitride and silicon dioxide enables high density integration of photonic devices and small PLC's for a variety of applications in photonic sensing and communications.
The large refractive index contrast between silicon nitride and silicon dioxide allows silicon nitride/dioxide planar waveguides to have a small mode size and low radiation bending loss compared with doped silicon dioxide waveguides. Small waveguide bend with low radiation loss can help make small integrated planar lightwave circuits (PLCs), and also high-Q waveguide ring resonators. This presentation will talk about the design, fabrication and characterization of low loss silicon nitride/dioxide planar waveguide devices including waveguide bend, waveguide cross, and leaky mode waveguide polarizer. The key contribution of this work is the use of the lateral mode interference (LMI) 3dB splitter to accurately measure the loss of the planar lightwave circuit devices. We will also talk about the waveguide ring resonators with silicon nitride/dioxide materials. The application for photonic biochemical sensors will also be discussed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.