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"Optical MEMS."
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Fundamentals of micro-optics
\"From optical fundamentals to advanced applications, this comprehensive guide to micro-optics covers all the key areas for those who need an in-depth introduction to micro-optic devices, technologies, and applications. Topics covered range from basic optics, optical materials, refraction, and diffraction, to micro-mirrors, micro-lenses, diffractive optics, optoelectronics, and fabrication. Advanced topics, such as tunable and nano-optics, are also discussed. Real-world case studies and numerous worked examples are provided throughout, making complex concepts easier to follow, whilst an extensive bibliography provides a valuable resource for further study. With exercises provided at the end of each chapter to aid and test understanding, this is an ideal textbook for graduate and advanced undergraduate students taking courses in optics, photonics, micro-optics, microsystems, and MEMs. It is also a useful self-study guide for research engineers working on optics development\"-- Provided by publisher.
Book
Grasping Force Control for a Robotic Hand by Slip Detection Using Developed Micro Laser Doppler Velocimeter
The purpose of this paper is to show the feasibility of grasping force control by feeding back signals of the developed micro-laser Doppler velocimeter (μ-LDV) and by discriminating whether a grasped object is slipping or not. LDV is well known as a high response surface velocity sensor which can measure various surfaces—such as metal, paper, film, and so on—thus suggesting the potential application of LDV as a slip sensor for grasping various objects. However, the use of LDV as a slip sensor has not yet been reported because the size of LDVs is too large to be installed on a robotic fingertip. We have solved the size problem and enabled the performance of a feasibility test with a few-millimeter-scale LDV referred to as micro-LDV (μ-LDV) by modifying the design which was adopted from MEMS (microelectromechanical systems) fabrication process. In this paper, by applying our developed μ-LDV as a slip sensor, we have successfully demonstrated grasping force control with three target objects—aluminum block, wood block, and white acrylic block—considering that various objects made of these materials can be found in homes and factories, without grasping force feedback. We provide proofs that LDV is a new promising candidate slip sensor for grasping force control to execute target grasping.
Journal Article
Applied Digital Optics
Miniaturization and mass replications have begun to lead the optical industry in the transition from traditional analog to novel digital optics. As digital optics enter the realm of mainstream technology through the worldwide sale of consumer electronic devices, this timely book aims to present the topic of digital optics in a unified way. Ranging from micro-optics to nanophotonics, and design to fabrication through to integration in final products, it reviews the various physical implementations of digital optics in either micro-refractives, waveguide (planar lightwave chips), diffractive and hybrid optics or sub-wavelength structures (resonant gratings, surface plasmons, photonic crystals and metamaterials). Finally, it presents a comprehensive list of industrial and commercial applications that are taking advantage of the unique properties of digital optics. Helps optical engineers review and choose the appropriate software tools to design, model and generate fabrication files. Gives product managers access to an exhaustive list of applications available in today’s market for integrating such digital optics, as well as where the next potential application of digital optics might be. Provides a broad view for technical marketing managers in all aspects of digital optics, and how such optics can be classified. Explains the numerical implementation of optical design and modelling techniques. Enables micro-optics foundries to integrate the latest fabrication and replication techniques, and accordingly fine tune their own fabrication processes. Supplementary book material is available at www.applieddigitaloptics.com Applied Digital Optics is aimed primarily at optical engineers and product development and technical marketing managers; it is also of interest to graduate-level photonics students and micro-optic foundries.
eBook
Miniaturized 3D Depth Sensing-Based Smartphone Light Field Camera
The miniaturization of 3D depth camera systems to reduce cost and power consumption is essential for their application in electrical devices that are trending toward smaller sizes (such as smartphones and unmanned aerial systems) and in other applications that cannot be realized via conventional approaches. Currently, equipment exists for a wide range of depth-sensing devices, including stereo vision, structured light, and time-of-flight. This paper reports on a miniaturized 3D depth camera based on a light field camera (LFC) configured with a single aperture and a micro-lens array (MLA). The single aperture and each micro-lens of the MLA serve as multi-camera systems for 3D surface imaging. To overcome the optical alignment challenge in the miniaturized LFC system, the MLA was designed to focus by attaching it to an image sensor. Theoretical analysis of the optical parameters was performed using optical simulation based on Monte Carlo ray tracing to find the valid optical parameters for miniaturized 3D camera systems. Moreover, we demonstrated multi-viewpoint image acquisition via a miniaturized 3D camera module integrated into a smartphone.
Journal Article
SiNx/SiO2-Based Fabry–Perot Interferometer on Sapphire for Near-UV Optical Gas Sensing of Formaldehyde in Air
Fabry–Perot interferometers (FPIs), comprising foundry-compatible dielectric thin films on sapphire wafer substrates, were investigated for possible use in chemical sensing. Specifically, structures comprising two vertically stacked distributed Bragg reflectors (DBRs), with the lower DBR between a sapphire substrate and a silicon-oxide (SiO2) resonator layer and the other DBR on top of this resonator layer, were investigated for operation in the near-ultraviolet (near-UV) range. The DBRs are composed of a stack of nitride-rich silicon-nitride (SiNx) layers for the higher index and SiO2 layers for the lower index. An exemplary application would be formaldehyde detection at sub-ppm concentrations in air, using UV absorption spectroscopy in the 300–360 nm band, while providing spectral selectivity against the main interfering gases, notably NO2 and O3. Although SiNx thin films are conventionally used only for visible and near-infrared optical wavelengths (above 450 nm) because of high absorbance at lower wavelengths, this work shows that nitride-rich SiNx is suitable for near-UV wavelengths. The interplay between spectral absorbance, transmittance and reflectance in a FPI is presented in a comparative study between one FPI design using stoichiometric material (Si3N4) and two designs based on N-rich compositions, SiN1.39 and SiN1.49. Spectral measurements confirm that if the design accounts for phase penetration depth, sufficient performance can be achieved with the SiN1.49-based FPI design for gas absorption spectroscopy in near-UV, with peak transmission at 330 nm of 64%, a free spectral range (FSR) of 20 nm and a full-width half-magnitude spectral resolution (FWHM) of 2 nm.
Journal Article
Review of sensing and actuation technologies - from optical MEMS and nanophotonics to photonic nanosystems
Entering the era of the Internet of Things (IoT) and fifth-generation (5G) mobile networks, the demand for compact, cost-effective, and high-performance sensors and actuators is skyrocketing. Optical technologies as complements to conventional electrical technologies provide a versatile platform to construct sensors and actuators for widespread applications, showing advantages of high data rate, strong multiplexing capability, fast response, low crosstalk, and immunity to electromagnetic interference. In this paper, we provide a comprehensive review of the development progress of optical sensing and actuation technologies. Their applications in optical detectors, optical sensors (further divided into physical and chemical/biological sensors), and optical communication/computing/imaging are presented. For each category of the applications, progress is introduced following the technology evolution trend from optical microelectromechanical systems (MEMS) and nanophotonics to photonic nanosystems. Future development directions of optical sensing/actuation technologies are also proposed.
Journal Article
Scanning Micromirror Platform Based on MEMS Technology for Medical Application
This topical review discusses recent development and trends on scanning micromirrors for biomedical applications. This also includes a biomedical micro robot for precise manipulations in a limited volume. The characteristics of medical scanning micromirror are explained in general with the fundamental of microelectromechanical systems (MEMS) for fabrication processes. Along with the explanations of mechanism and design, the principle of actuation are provided for general readers. In this review, several testing methodology and examples are described based on many types of actuators, such as, electrothermal actuators, electrostatic actuators, electromagnetic actuators, pneumatic actuators, and shape memory alloy. Moreover, this review provides description of the key fabrication processes and common materials in order to be a basic guideline for selecting micro-actuators. With recent developments on scanning micromirrors, performances of biomedical application are enhanced for higher resolution, high accuracy, and high dexterity. With further developments on integrations and control schemes, MEMS-based scanning micromirrors would be able to achieve a better performance for medical applications due to small size, ease in microfabrication, mass production, high scanning speed, low power consumption, mechanical stable, and integration compatibility.
Journal Article
Maintaining Transparency of a Heated MEMS Membrane for Enabling Long-Term Optical Measurements on Soot-Containing Exhaust Gas
Ensuring optical transparency over a wide spectral range of a window with a view into the tailpipe of the combustion engine, while it is exposed to the harsh environment of soot-containing exhaust gas, is an essential pre-requisite for introducing optical techniques for long-term monitoring of automotive emissions. Therefore, a regenerable window composed of an optically transparent polysilicon-carbide membrane with a diameter ranging from 100 µm up to 2000 µm has been fabricated in microelectromechanical systems (MEMS) technology. In the first operating mode, window transparency is periodically restored by pulsed heating of the membrane using an integrated resistor for heating to temperatures that result in oxidation of deposited soot (600–700 °C). In the second mode, the membrane is kept transparent by repelling soot particles using thermophoresis. The same integrated resistor is used to yield a temperature gradient by continuous moderate-temperature heating. Realized devices have been subjected to laboratory soot exposure experiments. Membrane temperatures exceeding 500 °C have been achieved without damage to the membrane. Moreover, heating of membranes to ΔT = 40 °C above gas temperature provides sufficient thermophoretic repulsion to prevent particle deposition and maintain transparency at high soot exposure, while non-heated identical membranes on the same die and at the same exposure are heavily contaminated.
Journal Article
Homogeneity of Electro-Mechanical and Optical Characteristics in Ring-Shaped MEMS Shutter Arrays with Subfield Addressing for Interference Microscopy
We present a MEMS array-based approach for micro-irises called “ring shutter”, utilizing subfield addressing for applications in advanced micro-optics, such as interference microscopy. This experimental study is focused on investigating the homogeneity of electro-mechanical and optical characteristics within and between subfields of a lab demonstrator device. The characterization aims to ensure crosstalk-free and swift optical performance, as demonstrated in a previous study. For this purpose, the transmission in the initial state, actuation voltages, and response dynamics are measured for each electrode and the entire device, and the results are thoroughly compared. The measurements are conducted by expanding an existing optical actuation setup via tailored 3D-printed apertures, to isolate selected rings and zones. Evaluation of measurement data confirms the stable and crosstalk-free operation of the ring shutter. Both angular and radial homogeneity are robust and follow the expectations in the experiment. While transmission, actuation voltage and closing time slightly rise (up to 25%) with increased radial position represented by five discrete ring sections, the characteristics for different angular zones remain nearly constant. Response times are measured below 40 µs, actuation voltages do not exceed 60 V, and the overall transmission of the ring shutter yields 53.6%.
Journal Article
Suspended Silicon Waveguide with Sub-Wavelength Grating Cladding for Optical MEMS in Mid-Infrared
Mid-infrared (MIR) photonics are generating considerable interest because of the potential applications in spectroscopic sensing, thermal imaging, and remote sensing. Silicon photonics is believed to be a promising solution to realize MIR photonic integrated circuits (PICs). The past decade has seen a huge growth in MIR PIC building blocks. However, there is still a need for the development of MIR reconfigurable photonics to enable powerful on-chip optical systems and new functionalities. In this paper, we present an MIR (3.7~4.1 μm wavelength range) MEMS reconfiguration approach using the suspended silicon waveguide platform on the silicon-on-insulator. With the sub-wavelength grating claddings, the photonic waveguide can be well integrated with the MEMS actuator, thus offering low-loss, energy-efficient, and effective reconfiguration. We present a simulation study on the waveguide design and depict the MEMS-integration approach. Moreover, we experimentally report the suspended waveguide with propagation loss (−2.9 dB/cm) and bending loss (−0.076 dB each). The suspended waveguide coupler is experimentally investigated. In addition, we validate the proposed optical MEMS approach using a reconfigurable ring resonator design. In conclusion, we experimentally demonstrate the proposed waveguide platform’s capability for MIR MEMS-reconfigurable photonics, which empowers the MIR on-chip optical systems for various applications.
Journal Article