We propose germanium-rich silicon germanium waveguides as a basic building block for polarization insensitive circuitry on silicon. In this work a detailed study of SiGe waveguides geometries is performed to find optimal parameters to simultaneously obtain low polarization sensitivity and single mode operation at λ=1.55μm. The polarization dependence of the effective index, group index and dispersion coefficient is investigated. Optimized geometries are tolerant to fabrication errors and can be realized with the current state of the art CMOS technology. As a next step polarization insensitive multimode interference structures have been designed.
We propose germanium-rich silicon-germanium (SiGe) as a new platform for optical interconnects. The platform viability is experimentally and theoretically investigated through the realization of main building blocks of passive circuitry. Germanium-rich Si1-xGex guiding layer on a graded SiGe layer is used to experimentally show 12μm radius bends by light confinement tuning at a wavelength of 1550nm. As a next step, Mach Zehnder interferometer with 10 dB extinction ratio is demonstrated. High Ge content of the proposed platform allows the coupling with Ge-based active devices, relying on a high quality epitaxial growth. Hence, the integration on Silicon of high speed and low power consumption Ge-rich active components is possible, despite the high lattice mismatch between silicon and germanium.
We experimentally and theoretically investigate the use of silicon germanium (SiGe) on silicon substrate as a new platform for optical interconnects. The system composed of Germanium (Ge) rich Si1-xGex guiding layer on a graded SiGe layer is showed to be suitable for the realization of all main building blocks of passive optical circuitry. We show experimentally at a wavelength of 1550nm that sharp 12μm radius bends can be obtained by light confinement tuning. Mach-Zehnder interferometer with more than 10 dB extinction ratio is also demonstrated. Moreover, Ge-rich Si1-xGex based passive components are very interesting for their native integration with Ge-rich active optical devices. Hence, by using this new platform for optical integrated circuits, lattice mismatch between silicon and germanium is no longer a major constraint for the integration of Ge-rich active photonic components on silicon.
We report on the developments of Ge/SiGe quantum well (QW) waveguide modulators operating at 1.3 μm. First we studied QW structures grown on a 13-μm SiGe buffer on bulk silicon. Light was directly coupled and propagated in the active region. Using a 3-μm wide and 50-μm long modulator, an extinction ratio larger than 4 dB was obtained for a drive voltage lower than 5 V in a 15 nm wavelength range. Then simulations were performed to evaluate the performances of an integrated modulator on silicon on insulator (SOI) platform. An eigenmode expension method was used to model the vertical optical coupling between SOI waveguide and Ge/SiGe devices. It is shown that a reduction of the thickness of the buffer leads to a significant improvement in the performances (extinction ratio, insertion loss) and footprint of the waveguide-integrated devices.
We report different experimental results showing the large potential of Ge/SiGe quantum well structures as a promising
solution forlow power consumption and large bandwidth optical modulators in silicon photonics technology. First, high
speed operation of such a Ge/SiGe multiple quantum well (MQW) electro-absorption modulator is reported, with 23
GHz bandwidth demonstrated from a 3 μm wide and 90 μm long Ge/SiGe MQW waveguide. Then the flexibility to shift
the absorption band edge from 1.42 to 1.3 μm is illustrated by strain engineering of the Ge wells. Finally electrorefraction by Quantum Confined Stark Effect (QCSE) is demonstrated, opening the route towards phase modulators
based on Ge/SiGe MQWs.
High speed Ge multiple quantum well (MQWs) electro-absorption (EA) modulator is reported. Device development
procedures from the epitaxial growth of high quality Ge MQWs by LEPECVD technique, fabrication, and
characterization of optoelectronic device are described.
Room temperature direct gap electroluminescence (EL) from a Ge/Si0.15Ge0.85 MQW waveguide was experimentally
studied. The dependence of the EL intensity on the injection current and temperature was measured. The direct gap EL
from Ge/SiGe MQWs was shown to be transverse-electric (TE) polarized, confirming that the EL originates from
recombination with a HH state.
We demonstrate surface-emitting distributed-feedback (DFB) quantum cascade (QC) lasers - operating in the midinfrared
- with double-slit 2nd order DFB gratings which are implemented via the sole patterning of the top metallic
layer, directly at the top of the active region. The small-slit design allows one to reduce the high plasmonic losses which
would be induced by a standard 2nd order grating. The devices operate at room temperature, in pulsed mode, and exhibit
single mode emission at 7.2 μm wavelength. The device far-field consists of an almost single-lobed emission with a low
divergence (<1 degree) in the grating direction. This result shows that sub-wavelength patterning of the top metallization
layer of mid-infrared surface-plasmon QC lasers allows one to reduce the losses even for higher-order DFB grating
devices.
Transdermal drug delivery is a novel alternative painless way to inject medicine and therapic agents through skin. Our study investigates an array of out-of-plane microneedles to pierce the permeability barrier without reaching the nerves in the deeper layers. To the best of our knowledge, the skin behavior during the insertion of a microneedle array through its different layers has not up to now been fully dealt with. In this paper, we assume skin to be similar to a stratified material, and approximate it as composed of three layers: the stratum corneum is described by a linear isotropic material model while a hyperelastic material model (Ogden) is used for the two deeper layers. The choice of the model is all the more important since we work at a microscopic scale. We prove that differences exist between the insertion of one microneedle and the insertion of an array of microneedles in terms of the skin deformation and value of the insertion force due to the interaction among microneedles. We simulate the insertion of a micro needles array using a finite element method and the results show a relation between the microneedle diameter, the array density and the microneedle length. Our arrays of microneedles are fabricated by deep reacting ion etching (DRIE) and coated by titanium out of biocompatibility concerns. In this paper, the dimensions of the microneedles are: 500 microns in length, 30-60 microns in inner channel diameter and 100-150 microns in outer diameter in order to be in agreement with our analytically analysis. Some experimental validations are given.
The growing place of electronics devices in our society increases the demand of small devices such as RF filters, time references and oscillators. The aim of this work concerns the design and characterization of a new kind of crystalline silicon microresonator fabricated using a DRIE (Deep Reactive Ion Etching) technique. This device can be fabricated by IC compatible techniques. This kind of microresonators is electrostatically actuated and uses a contour or Lamé mode as fundamental mode of vibration. Its size gives the resonant frequency and behavior. The mechanical characterization of one microresonator is carried out using an optical bench set-up. The first results obtained on a device show a high Q factor in air close to 1000 at the resonant frequency of 10.3 MHz.
One of the authors has proposed an electrostatically driven torsional resonator with two degrees of freedom (TDF). The main characteristic of the TDF resonator, in which the electrode gap does not directly affect to inconsistencies between low voltage driving and a large range of motion, is reported. The TDF structure is also beneficial for achieving high Q values. However, size reduction was difficult because of the limitations of the fabrication process. In this study, the TDF resonator is miniaturized by the UV-LIGA (UV exposed lithography and electroplated structure) process. The process and the frequency characteristics of the resonator are reported.
This paper deals with a work in progress concerning the fabrication of an insect-like microrobot. Thermal actuation has been chosen to move this microrobot, because of their large motions and their interesting density of energy. An integrated structure was chosen. Compliant thermal micro- actuators have been studied, fabricated and experimented. The characterization and modeling of these actuators have been done. Then, microlegs were modelized and designed with two degrees of freedom for each leg. The design of the microlegs and the operating cycle are given in this paper. Then the various stages of the microfabrication process are precisely described the microlegs are constituted of two thermal bimorphs connected together with a microbeam. Several microlegs are fabricated on one silicone wafer and bonded on a printed board to allow their activation. Their experimentation allows to give the results of each of the two degrees of freedom concerning the motions of these microlegs. Based on the results of these first experiments, the second generation of microlegs was conceived, made and tested, with the aim of decreasing the energy consumption. Then the next step will be the microfabrication of a new type of microlegs, before the whole structure of the microrobot including their legs in a monolithic way on one single silicon wafer.
We report in this paper the study of a new metallic microresonator realized by UV-LIGA technique. This kind of device is excited electrostatically and takes advantage of the contour modes or Lame-modes of the structure. Design methods of such device are presented and simulated with a Finite Element Program. Details on the microfabrication process are also presented. The vibration modes are detected with an optical bench set-up and preliminary electrical results are presented. A comparison between experiments and numerical predictions are finally 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.