Electromechanical wavelength tuning of double-membrane photonic crystal cavities

We present a method for tuning the resonant wavelength of photonic crystal cavities (PCCs) around 1.55 um. Large tuning of the PCC mode is enabled by electromechanically controlling the separation between two parallel InGaAsP membranes. A fabrication method to avoid sticking between the membranes is discussed. Reversible red/blue shifting of the symmetric/anti-symmetric modes has been observed, which provides clear evidence of the electromechanical tuning, and a maximum shift of 10 nm with < 6 V applied bias has been obtained.Comment: 9 pages, 3 figure

The effects of arcjet operating condition and constrictor geometry on the plasma plume

Measurements of plasma number density and electron temperature were obtained in the plumes of lab arcjet thrusters using electrostatic probes of both spherical and cylindrical geometry. The two arcjet thrusters used had different constrictor and/or nozzle geometries and operated on mixtures of nitrogen, hydrogen, and ammonia to simulate the decomposition products of hydrazine and ammonia. An increase in the measured electron density was observed for both geometries with increasing arc power at a constant mass flow rate and with increasing mass flow rate at a constant arc current. For a given operating condition, the electron number density decreased exponentially off centerline and followed an inverse distance squared relationship along the thrust axis. Typical measured electron temperatures ranged from 0.1 to 0.2 eV

Development and Packaging of Microsystems Using Foundry Services

Micro-electro-mechanical systems (MEMS) are a new and rapidly growing field of research. Several advances to the MEMS state of the art were achieved through design and characterization of novel devices. Empirical and theoretical model of polysilicon thermal actuators were developed to understand their behavior. The most extensive investigation of the Multi-User MEMS Processes (MUMPs) polysilicon resistivity was also performed. The first published value for the thermal coefficient of resistivity (TCR) of the MUMPs Poly 1 layer was determined as 1.25 x 10(exp -3)/K. The sheet resistance of the MUMPs polysilicon layers was found to be dependent on linewidth due to presence or absence of lateral phosphorus diffusion. The functional integration of MEMS with CMOS was demonstrated through the design of automated positioning and assembly systems, and a new power averaging scheme was devised. Packaging of MEMS using foundry multichip modules (MCMs) was shown to be a feasible approach to physical integration of MEMS with microelectronics. MEMS test die were packaged using Micro Module Systems MCM-D and General Electric High Density Intercounect and Chip-on-Flex MCM foundries. Xenon difluoride (XeF2) was found to be an excellent post-packaging etchant for bulk micromachined MEMS. For surface micromachining, hydrofluoric acid (HF) can be used

Nanomechanical single-photon routing

The merger between integrated photonics and quantum optics promises new opportunities within photonic quantum technology with the very significant progress on excellent photon-emitter interfaces and advanced optical circuits. A key missing functionality is rapid circuitry reconfigurability that ultimately does not introduce loss or emitter decoherence, and operating at a speed matching the photon generation and quantum memory storage time of the on-chip quantum emitter. This ambitious goal requires entirely new active quantum-photonic devices by extending the traditional approaches to reconfigurability. Here, by merging nano-optomechanics and deterministic photon-emitter interfaces we demonstrate on-chip single-photon routing with low loss, small device footprint, and an intrinsic time response approaching the spin coherence time of solid-state quantum emitters. The device is an essential building block for constructing advanced quantum photonic architectures on-chip, towards, e.g., coherent multi-photon sources, deterministic photon-photon quantum gates, quantum repeater nodes, or scalable quantum networks.Comment: 7 pages, 3 figures, supplementary informatio

A closed-loop digitally controlled MEMS gyroscope with unconstrained Sigma-Delta force-feedback

In this paper, we describe the system architecture and prototype measurements of a MEMS gyroscope system with a resolution of 0.025 degrees/s/root Hz. The architecture makes extensive use of control loops, which are mostly in the digital domain. For the primary mode both the amplitude and the resonance frequency are tracked and controlled. The secondary mode readout is based on unconstrained Sigma Delta force-feedback, which does not require a compensation filter in the loop and thus allows more beneficial quantization noise shaping than prior designs of the same order. Due to the force-feedback, the gyroscope has ample dynamic range to correct the quadrature error in the digital domain. The largely digital setup also gives a lot of flexibility in characterization and testing, where system identification techniques have been used to characterize the sensors. This way, a parasitic direct electrical coupling between actuation and readout of the mass-spring systems was estimated and corrected in the digital domain. Special care is also given to the capacitive readout circuit, which operates in continuous time

Design and analysis of a high-gain and robust multi-DOF electro-thermally actuated MEMS gyroscope

© 2018 by the authors. This paper presents the design and analysis of a multi degree of freedom (DOF) electro-thermally actuated non-resonant MEMS gyroscope with a 3-DOF drive mode and 1-DOF sense mode system. The 3-DOF drive mode system consists of three masses coupled together using suspension beams. The 1-DOF system consists of a single mass whose motion is decoupled from the drive mode using a decoupling frame. The gyroscope is designed to be operated in the flat region between the first two resonant peaks in drive mode, thus minimizing the effect of environmental and fabrication process variations on device performance. The high gain in the flat operational region is achieved by tuning the suspension beams stiffness. A detailed analytical model, considering the dynamics of both the electro-thermal actuator and multi-mass system, is developed. A parametric optimization is carried out, considering the microfabrication process constraints of the Metal Multi-User MEMS Processes (MetalMUMPs), to achieve high gain. The stiffness of suspension beams is optimized such that the sense mode resonant frequency lies in the flat region between the first two resonant peaks in the drive mode. The results acquired through the developed analytical model are verified with the help of 3D finite element method (FEM)-based simulations. The first three resonant frequencies in the drive mode are designed to be 2.51 kHz, 3.68 kHz, and 5.77 kHz, respectively. The sense mode resonant frequency is designed to be 3.13 kHz. At an actuation voltage of 0.2 V, the dynamically amplified drive mode gain in the sense mass is obtained to be 18.6 μm. With this gain, a capacitive change of 28.11 f F and 862.13 f F is achieved corresponding to the sense mode amplitude of 0.15 μm and 4.5 μm at atmospheric air pressure and in a vacuum, respectively

Dual Q-switched laser outputs from a single lasing medium using an intracavity MEMS micromirror array

An intracavity array of individually controlled microelectromechanical system scanning micromirrors was used to actively Q-switch a single side-pumped Nd:YAG gain medium. Two equal power independent laser outputs were simultaneously obtained by separate actuation of two adjacent micromirrors with a combined average output power of 125 mW. Pulse durations of 28 ns FWHM at 8.7 kHz repetition frequency and 34 ns FWHM at 7.9 kHz repetition frequency were observed for the two output beams with beam quality factors M2 of 1.2 and 1.1 and peak powers of 253 W and 232 W, respectively

MEMS micromirrors for imaging applications

Strathclyde theses - ask staff. Thesis no. : T13478Optical MEMS (microelectromechanical systems) are widely used in various applications. In this thesis, the design, simulation and characterisation of two optical MEMS devices for imaging applications, a varifocal micromirror and a 2D scanning micromirror, are introduced. Both devices have been fabricated using the commercial Silicon-on-Insulator multi-users MEMS processes (SOIMUMPs), in the 10 m thick Silicon-on-Insulator (SOI) wafer. Optical MEMS device with variable focal length is a critical component for imaging system miniaturisation. In this thesis, a thermally-actuated varifocal micromirror (VFM) with 1-mm-diameter aperture is introduced. The electrothermal actuation through Joule heating of the micromirror suspensions and the optothermal actuation using incident laser power absorption have been demonstrated as well as finite element method (FEM) simulation comparisons. Especially, the optical aberrations produced by this VFM have been statistically quantified to be negligible throughout the actuation range. A compact imaging system incorporating this VFM has been demonstrated with high quality imaging results. MEMS 2D scanners, or scanning micromirrors, are another type of optical MEMS which have been widely investigated for applications such as biomedical microscope imaging, projection, retinal display and optical switches for telecommunication network, etc. For large and fast scanning motions, the actuation scheme to scan a micromirror in two axes, the structural connections and arrangement are fundamental. The microscanner introduced utilises two types of actuators, electrothermal actuators and electrostatic comb-drives, to scan a 1.2-mm-diameter gold coated silicon micromirror in two orthogonal axes. With assistance of FEM software, CoventorWare, the structure optimisation of actuators and flexure connections are presented. The maximum optical scan angles in two axes by each type of actuator individually and by actuating the two at the same time have been characterised experimentally. By programming actuation signals, the microscanner has achieved a rectangular scan pattern with 7° 10° angular-scan-field at a line-scan rate of around 1656 Hz.Optical MEMS (microelectromechanical systems) are widely used in various applications. In this thesis, the design, simulation and characterisation of two optical MEMS devices for imaging applications, a varifocal micromirror and a 2D scanning micromirror, are introduced. Both devices have been fabricated using the commercial Silicon-on-Insulator multi-users MEMS processes (SOIMUMPs), in the 10 m thick Silicon-on-Insulator (SOI) wafer. Optical MEMS device with variable focal length is a critical component for imaging system miniaturisation. In this thesis, a thermally-actuated varifocal micromirror (VFM) with 1-mm-diameter aperture is introduced. The electrothermal actuation through Joule heating of the micromirror suspensions and the optothermal actuation using incident laser power absorption have been demonstrated as well as finite element method (FEM) simulation comparisons. Especially, the optical aberrations produced by this VFM have been statistically quantified to be negligible throughout the actuation range. A compact imaging system incorporating this VFM has been demonstrated with high quality imaging results. MEMS 2D scanners, or scanning micromirrors, are another type of optical MEMS which have been widely investigated for applications such as biomedical microscope imaging, projection, retinal display and optical switches for telecommunication network, etc. For large and fast scanning motions, the actuation scheme to scan a micromirror in two axes, the structural connections and arrangement are fundamental. The microscanner introduced utilises two types of actuators, electrothermal actuators and electrostatic comb-drives, to scan a 1.2-mm-diameter gold coated silicon micromirror in two orthogonal axes. With assistance of FEM software, CoventorWare, the structure optimisation of actuators and flexure connections are presented. The maximum optical scan angles in two axes by each type of actuator individually and by actuating the two at the same time have been characterised experimentally. By programming actuation signals, the microscanner has achieved a rectangular scan pattern with 7° 10° angular-scan-field at a line-scan rate of around 1656 Hz