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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.

This study introduces a novel approach for analyzing thin film interference spectra by employing a micro-spectrometer equipped with a spectral chip. Focusing on zinc oxide (ZnO) thin films prepared via the sol–gel method, this research aims to explore the films’ physical properties through spectral analysis. After obtaining the interference spectrum of the ZnO thin films, the peak positions within the spectrum were cataloged. Mathematical simulation was used to adjust the refractive index and thickness of the films to match the simulated interference peak positions with the observed peak positions. The thickness of the prepared ZnO film was estimated to be 4.9 μm and its refractive index at 80 °C was estimated to be 1.96. In addition, the measurement system was used to detect environmental changes, including temperature changes and gas exposure. It was observed that the optical characteristics of ZnO films exhibit marked variations with temperature shifts, enabling the establishment of a temperature calibration curve based on spectral feature displacement. In addition, experiments using a variety of gases showed that NO2 and gaseous isopropanol significantly affect the interference spectrum of ZnO, with the peak of the interference spectrum shifted by 2.3 nm and 5.2 nm, respectively, after injection of the two gases. This indicates that interferometric spectroscopy can serve as an effective tool for ZnO monitoring, capable of selectively detecting specific gases.

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. [ABSTRACT FROM AUTHOR]

This study introduces a novel approach for analyzing thin film interference spectra by employing a micro-spectrometer equipped with a spectral chip. Focusing on zinc oxide (ZnO) thin films prepared via the sol–gel method, this research aims to explore the films' physical properties through spectral analysis. After obtaining the interference spectrum of the ZnO thin films, the peak positions within the spectrum were cataloged. Mathematical simulation was used to adjust the refractive index and thickness of the films to match the simulated interference peak positions with the observed peak positions. The thickness of the prepared ZnO film was estimated to be 4.9 μm and its refractive index at 80 °C was estimated to be 1.96. In addition, the measurement system was used to detect environmental changes, including temperature changes and gas exposure. It was observed that the optical characteristics of ZnO films exhibit marked variations with temperature shifts, enabling the establishment of a temperature calibration curve based on spectral feature displacement. In addition, experiments using a variety of gases showed that NO2 and gaseous isopropanol significantly affect the interference spectrum of ZnO, with the peak of the interference spectrum shifted by 2.3 nm and 5.2 nm, respectively, after injection of the two gases. This indicates that interferometric spectroscopy can serve as an effective tool for ZnO monitoring, capable of selectively detecting specific gases. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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.

Biological component of cells, protein has been effectively studied and investigated using biological sensors. Photonic crystal-based sensor is highly sensitive optical nanostructure it can be manipulated to affect the motion of photon for users' application. In the proposed work microcavity based photonic crystal biosensor has been designed and investigated for its different optical sensing evaluation parameters such as transmission efficiency, sensitivity, Q factor and peak resonant wavelengths. Sensor is designed and analyzed for early detection of colon cancer tissues in blood. Radius of defect micropillar has been increased from 0.16 µm to 0.19 µm. High Quality factor 10232 has been achieved with the micro pillar radius of 0.17 µm and sensitivity 700nm/RIU. Similarly, radius of 0.16 µm, 0.18 µm and 0.19 µm has attained quality factor and sensitivity such as 5324, 7232, 8343 and 111 nm/RIU, 320 nm/RIU and 340 nm/RIU respectively. Compared other work in literature, proposed work has shown better sensing capability. Designed sensor has shown remarkable output and feasibility for future fabrication.

Quantitative in vivo measurement helps physicians determine abnormal tissue size or resection margin accurately. Herein, in vivo 3D imaging of abnormal features during endoscopic operation using a light switching microprojector is reported. The microprojector features rotational offset microlens arrays and a customized illumination fiber bundle fully integrated through a single illumination channel of a clinical endoscope. The illumination channel switches white light into structured laser patterns on demand. The 3D profiles are precisely extracted by calculating the distortion of uniform structured patterns on a target surface. The 3D endoscope allows the precise measurement of the size and volume of polyp phantoms within 7.70% and 13.33% errors, respectively. The experimental results show the accurate measurements of abnormal ex vivo human abnormal tissue and in vivo volume changes in the inflated stomach wall of an anesthetized pig. The microprojector can provide a new opportunity for in vivo 3D endoscopic imaging and biometric applications.

Abstract Conventional pain assessment methods such as patients’ self-reporting restrict the possibility of easy pain monitoring while pain serves as an important role in clinical practice. Here we report a pain assessment method via 3D face reading camera assisted by dot pattern illumination. The face reading camera module (FRCM) consists of a stereo camera and a dot projector, which allow the quantitative measurement of facial expression changes without human subjective judgement. The rotational offset microlens arrays (roMLAs) in the dot projector form a uniform dense dot pattern on a human face. The dot projection facilitates evaluating three-dimensional change of facial expression by improving 3D reconstruction results of non-textured facial surfaces. In addition, the FRCM provides consistent pain rating from 3D data, regardless of head movement. This pain assessment method can provide a new guideline for precise, real-time, and continuous pain monitoring.

Biological component of cells, protein has been effectively studied and investigated using biological sensors. Photonic crystal-based sensor is highly sensitive optical nanostructure it can be manipulated to affect the motion of photon for users' application. In the proposed work microcavity based photonic crystal biosensor has been designed and investigated for its different optical sensing evaluation parameters such as transmission efficiency, sensitivity, Q factor and peak resonant wavelengths. Sensor is designed and analyzed for early detection of colon cancer tissues in blood. Radius of defect micropillar has been increased from 0.16 µm to 0.19 µm. High Quality factor 10232 has been achieved with the micro pillar radius of 0.17 µm and sensitivity 700nm/RIU. Similarly, radius of 0.16 µm, 0.18 µm and 0.19 µm has attained quality factor and sensitivity such as 5324,7232,8343 and 111 nm/RIU, 320 nm/RIU and 340 nm/RIU respectively. Compared other work in literature, proposed work has shown better sensing capability. Designed sensor has shown remarkable output and feasibility for future fabrication. [ABSTRACT FROM AUTHOR]

In this work, vertical micromirrors that are fabricated using deep etching of silicon followed by metal sputtering are studied. Physical parameter extraction methodology, image processing, machine learning and discrete element analysis are used to extend the easy-to-take scanning electron microscope images into 3-D topographical information, that are usually obtained using atomic force microscope and transmission electron microscope. The experimental results show that vertical micromirrors surface quality has a granular nature showing degraded performance and a different optical response with respect to the bulk metal. A physical model is developed and validated by comparing the measured reflectivity of the fabricated micromirrors with a multi-layer reflectivity optical model based on the effective medium theory fed by the extracted physical parameters. In agreement with the experimental results, the model predicts a reflectivity of about 60 % for a sputtered aluminum thickness of 50 nm, compared to 97.5% reflectivity predicted by the bulk metal model. [2021-0154] [ABSTRACT FROM AUTHOR]

Conventional pain assessment methods such as patients' self-reporting restrict the possibility of easy pain monitoring while pain serves as an important role in clinical practice. Here we report a pain assessment method via 3D face reading camera assisted by dot pattern illumination. The face reading camera module (FRCM) consists of a stereo camera and a dot projector, which allow the quantitative measurement of facial expression changes without human subjective judgement. The rotational offset microlens arrays (roMLAs) in the dot projector form a uniform dense dot pattern on a human face. The dot projection facilitates evaluating three-dimensional change of facial expression by improving 3D reconstruction results of non-textured facial surfaces. In addition, the FRCM provides consistent pain rating from 3D data, regardless of head movement. This pain assessment method can provide a new guideline for precise, real-time, and continuous pain monitoring. [ABSTRACT FROM AUTHOR]

Abstract Implementing 3D surface imaging camera systems into miniaturized devices for a variety of 3D applications such as movement recognition, object sensing, and 3D endoscopy has received great attention over the past decade. Recently, various MEMS techniques enabled the fabrication of key optical elements for 3D surface imaging with compact size, reasonable cost, and high yield. This article will overview the principles of major categories of 3D surface imaging techniques and their applications using optical MEMS devices for compact 3D surface imaging camera.

Today flexibility means to produce reasonably priced customized products of high quality that can be quickly delivered to customers. The article analyses issues related to physic, able to generating defects, affecting the reliability limits for MEMS (Micro-Electro-Mechanical Systems). The MEMS industry is currently at a much more vulnerable position than it appears, regardless of how wonderful its future may look like. A full understanding of the physics and statistics of the defect generation is required to investigate the ultimate reliability limitations for nanodevices. Biggest challenge: cost effective, high volume production.

This research work is targeting to demonstrate that micromirror arrays can also be fabricated successfully on flexible substrates—not only on glass substrates. The paper reports on the technological data of a successful process on a flexible substrate for curvilinear surfaces. Polyethylene naphthalate substrate was selected for its low cost, strong resistance against chemicals which are used in fabrication process and sufficient optical transmission for the visible and near infrared spectrum. Finally, electrostatic actuation of the fabricated micromirror structures is proven experimentally. [ABSTRACT FROM AUTHOR]

This paper presents a performance analysis of different microcantilever shapes integrated with the optical MEMS system in different fluid mediums. Microcantilevers such as rectangular, trapezoidal, and triangle profile are coupled with optical sensing layers. Here, the concept of integration of optical sensing layer with different shapes of microcantilever is novel. The cantilever is designed and developed in CAD tools. Numerical analysis of different shapes of microcantilever was carried out with the help of Ansys Workbench. Optimal design of the regular microcantilever is considered during the analysis. The pressure is applied to the free end of the cantilever in the range of 100 to 250 kPa. The complete photonic sensing layer is analyzed with the help of an finite difference time domain (FDTD) tool called MIT Electromagnetic Equation Propagation (MEEP). The transmission spectrum is obtained for each microcantilever model. The pressure‐induced refractive index is calculated for the equivalent maximum stress generated. The result shows that a remarkable Q factor was obtained for rectangular, trapezoidal, and triangular profile microcantilevers with an optical system. Triangular and rectangular profiles have shown remarkable contribution over quality factor for air mediums such as 10 120, 1300, respectively. High pressure sensitivity of 1.92 nm/kPa was obtained for rectangular microcantilever in air. Least sensitivity of 0.16 nm/kPa was obtained for triangle microcantilever in the water medium. The proposed work successfully distinguishes various shapes of microcantilever in terms of sensitivity and Q factor. It is having tremendous application in sensing biofluids and in device miniaturization. [ABSTRACT FROM AUTHOR]

For the first time, a CAOS (i.e., Coded Access Optical Sensor) spectrometer is demonstrated. The design implemented uses a reflective diffraction grating and a time-frequency CAOS mode operations Digital Micromirror Device (DMD) in combination with a large area point photo-detector to enable highly programmable linear High Dynamic Range (HDR) spectrometry. Experiments are conducted with a 2850 K color temperature light bulb source and visible band color bandpass and high-pass filters as well as neutral density (ND) attenuation filters. A ~369 nm to ~715 nm input light source spectrum is measured with a designed ~1 nm spectral resolution. Using the optical filters and different CAOS modes, namely, Code Division Multiple Access (CDMA), Frequency Modulation (FM)-CDMA and FM-Time Division Multiple Access (TDMA) modes, measured are improving spectrometer linear dynamic ranges of 28 dB, 50 dB, and 96.2 dB, respectively. Applications for the linear HDR CAOS spectrometer includes materials inspection in biomedicine, foods, forensics, and pharmaceuticals. [ABSTRACT FROM AUTHOR]

For the first time, demonstrated is the active-mode CAOS (i.e., Coded Access Optical Sensor) camera. The design demonstrated uses a hybrid approach to both optical device engagement and time-frequency CAOS mode operations. Specifically, time-frequency modulation of both the target illumination light source and the Digital Micromirror Device (DMD) combine to deliver the Frequency Modulation (FM)-Code Division Multiple Access (CDMA) mode of the CAOS camera. Using a 39.6 Klux white light 32 kHz FM LED source combined with a 1 kHz bit rate 4096 bits Walsh sequence CDMA code via the DMD, achieved is 58 $ \times $ 70 CAOS pixels near 60 dB linear Dynamic Range (DR) imaging of a 36 patch calibrated high DR white light target. Applications for the active-mode CAOS camera are numerous and include indoor full spectrum food inspection and photography where a linear DR camera can play an important role for accurate analysis and color image recovery. [ABSTRACT FROM AUTHOR]

Miniaturized spectrometers are attracting widespread interest due to the rising demand for portable spectroscopic applications. While the chip-scale spectrometers are widely investigated using silicon photonics technology, few research have addressed the need for a mid-infrared (MIR) integrated chip-scale spectrometer due to the lack of an effective reconfigurable photonics approach. In this paper, we present a novel solution using silicon photonics MEMS technology in the MIR region (3.6–5 µm wavelength range). We adopt a computational spectrometry scheme using the digitalized control of cascaded MEMS-tunable waveguide couplers. The MEMS waveguide couplers are operated in digital on/off mode, thus making the device immune to driving voltage fluctuations and robust for on-chip field sensing applications. Moreover, a comprehensive numerical analysis method is discussed to systematically evaluate the performance of the computational spectrometer, including its resolution and operational bandwidth. As a proof-of-concept, a chip-scale spectrometer realized by seven cascaded MEMS-actuated waveguide coupler is demonstrated. The sparse spectral reconstruction is demonstrated in the wavelength range from 3.65 to 4.1 µm and the dual-peaks reconstruction results indicate a resolution of 8 nm. Besides, response time and power consumption of the proposed device are experimentally characterized. Benefitting from good scalability, the spectral resolution can be further improved by increasing the number of waveguide coupler stages. The proposed work has the potential to realize lab-on-a-chip applications with advances in MIR silicon photonics. © 2001 Elsevier Science. All rights reserved. • A mid-infrared digitalized MEMS-enabled computational spectrometer on the SOI platform is proposed. • The proposed spectrometer features a series of individually controlled MEMS-tunable waveguide couplers operating in a digital on/off mode in a single chip. • The proposed spectrometer demonstrates a broad working bandwidth with relatively high spectral resolution. • The proposed spectrometer demonstrates low power consumption and good scalability. [ABSTRACT FROM AUTHOR]

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.

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Imaging applications based on microlens arrays (MLAs) have a great potential for the depth sensor, wide field-of-view camera and the reconstructed hologram. However, the narrow depth-of-field remains the challenge for accurate, reliable depth estimation. Multifocal microlens array (Mf-MLAs) is perceived as a major breakthrough, but existing fabrication methods are still hindered by the expensive, low-throughput, and dissimilar numerical aperture (NA) of individual lenses due to the multiple steps in the photolithography process. This paper reports the fabrication method of high NA, Mf-MLAs for the extended depth-of-field using single-step photolithography assisted by chemical wet etching. The various lens parameters of Mf-MLAs are manipulated by the multi-sized hole photomask and the wet etch time. Theoretical and experimental results show that the Mf-MLAs have three types of lens with different focal lengths, while maintaining the uniform and high NA irrespective of the lens type. Additionally, we demonstrate the multi-focal plane image acquisition via Mf-MLAs integrated into a microscope.

3D imaging of a biological sample provides information about cellular and subcellular structures that are important in cell biology and related diseases. However, most 3D imaging systems, such as confocal and tomographic microscopy systems, are complex and expensive. Here, we developed a quasi-3D imaging tool that is compatible with most conventional microscopes by integrating micromirrors and microchannel structures on coverslips to provide bidirectional imaging. Microfabricated micromirrors had a precisely 45° reflection angle and optically clean reflective surfaces with high reflectance over 95%. The micromirrors were embedded on coverslips that could be assembled as a microchannel structure. We demonstrated that this simple disposable device allows a conventional microscope to perform bidirectional imaging with simple control of a focal plane. Images of microbeads and cells under bright-field and fluorescent microscopy show that the device can provide a quick analysis of 3D information, such as 3D positions and subcellular structures.

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.

In this paper, a novel vibratory optical MEMS gyroscope is proposed, which is composed of an optical sensing system, an electrostatic comb-drive actuator, and a mass-spring system with 2 degrees of freedom and a decoupling frame. The optical sensing system consists of a laser diode light source, a tunable photonic crystal, a photodetector, and integrated waveguides. The sensitive element of the proposed gyroscope has been designed with separated primary and secondary resonance frequencies to increase the operating bandwidth. Simulation results show that the functional characteristics of the proposed gyroscope are as follows: an operating frequency of 1830 Hz, a sense mode resonance frequency of 2330 Hz, an operating bandwidth of 200 Hz, a mechanical sensitivity of 0.14 nm/(°/s), an optical sensitivity of 0.051 nm/(°/s), and a measurement range of ±500 °/s. [ABSTRACT FROM AUTHOR]

A free space cross-connection of the optical signals using an optical micro/nano-electro-mechanical system(OMEMS/ONEMS) is designed and simulated using the commercial software called MATLAB and OPTI-WAVE programs, in which a nonlinear micro-ring device known as a Panda-ring resonator is used to form the cross connection of two different sources, the whispering gallery modes (WGM) of those two wavelengths are multiplexed, where bandwidth capacity of the dense wavelength multiplexing can reach the Big data link criteria, in which the capacity link is up 40 PB (Petra bytes). The design device material is the AlGaAsP/InP, from which the WGM beams of the cross connection is generated within each center ring device by controlling the two coupled nonlinear side ring parameters. The cross connection of the multi-light nodes are generated and the cross-connection performed. The triple Panda-ring is embedded by the light photo-detector and source, from which the ring three input signals are modulated and input into the system and multiplexed with the previous cross connection sources. The cross-connection among the input signals via the WGMs and input signals from ring three can emerge, where finally, the cross-connected signals of them can be generated and seen at the center rings, i.e. WGM nodes and the output ports, which is allowed to have the high capacity transmission, where the use of the internet of things (IoT) is plausible. [ABSTRACT FROM AUTHOR]

Optomechanical SiN nano-oscillators in high-finesse Fabry–Perot cavities can be used to investigate the interaction between mechanical and optical degree of freedom for ultra-sensitive metrology and fundamental quantum mechanical studies. In this paper, we present a nano-oscillator made of a high-stress round-shaped SiN membrane with an integrated on-chip 3-D acoustic shield properly designed to reduce mechanical losses. This oscillator works in the range of 200 kHz to 5 MHz and features a mechanical quality factor of $Q\simeq 10^{7}$ and a Q-frequency product in excess of $6.2 \times 10^{12}$ Hz at room temperature, fulfilling the minimum requirement for quantum ground-state cooling of the oscillator in an optomechanical cavity. The device is obtained by MEMS deep reactive-ion etching (DRIE) bulk micromachining with a two-side silicon processing on a silicon-on-insulator wafer. The microfabrication process is quite flexible such that additional layers could be deposited over the SiN membrane before the DRIE steps, if required for a sensing application. Therefore, such oscillator is a promising candidate for quantum sensing applications in the context of the emerging field of quantum technologies. [2018-0186] [ABSTRACT FROM AUTHOR]

In this paper, we investigate a hybrid optomechanical system consisting of two cavities, which one of them is an optomechanical cavity that includes an optical parametric amplifier (OPA) and the other is a traditional cavity which contains an atomic medium. Hamiltonian of the system is written in a rotating frame with a rotation frequency of the frequency of input field to the system. Using Heisenberg-Langevin equations of motion, the dynamics of the system is described. Applying the steady-state conditions leads to a system of equations of the mean values of the operators of the system. The stability condition of the system is satisfied numerically and behavior of optomechanical cavity is investigated in different situations to find the effect of changing of the parameters of the system on the type of its stability. We show proposed system has the capability of tristable behavior, where, the gain coefficient of OPA acts as a switch in changing the bistability of the system to a tristable manner. The building block of the tristability in this system can be figured out as the enhanced nonlinearity of the system due to the presence of OPA. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Additive manufacturing using photocurable polymers is one method to answer the increased demand of ceramic structures with complicated morphology by fabricating ceramic parts with high resolution and good surface quality. We introduce here a new method to fabricate SiOC ceramic structures by utilizing a simple physical blend between two different preceramic polysiloxanes, one providing photosensitive acrylate groups while the other one a high ceramic yield. Different blend ratios have been realized and respectively optimized concerning the printing additives and setting times to fabricate exact replications of highly complex polysiloxane structures by Digital Light Processing. After pyrolysis, a uniform, homogenous shrinkage was observed yielding dense, pore- as well as crack-free SiOC ceramics. By adjusting the ratio between the different polysiloxanes, parameters such as the ceramic yield, shrinkage, chemical composition and resolution after pyrolysis could be tailored in a wide range of values. [ABSTRACT FROM AUTHOR]

In this paper, we report the analysis, fabrication, and characterization of metallized slotted micromirrors for optical MEMS applications. A scalar model for the transmittance of the micromirror with a vertical slit using Gaussian beam analysis is developed and a closed-form expression is obtained. Detailed finite difference time domain simulation is carried out for the micromirror transmittance to understand the effect of polarization and bench mark the developed model for slit width-to-wavelength ratios in the range 0 to 8. A MEMS chip is designed comprising fiber grooves and variable slit micromirror controlled by a comb-drive actuator. The chip is fabricated using deep reactive ion etching of silicon-on-insulator substrate with 100-μm device layer height. The motion of the actuator is characterized using an opto-mechanical technique and the transmittance of the micromirror for different incident polarizations is extracted versus the slit width and compared with the theoretical predictions showing good agreement. [ABSTRACT FROM AUTHOR]

We develop an optical ring resonator with tunable coupling coefficients for use in wavelength division multiplexing routers. The coupling coefficients of the resonator are precisely tuned by the utilization of an electrostatic comb drive microelectromechanical system (MEMS) actuator. The MEMS actuator has the ability to accurately adjust gap spacing between cavity and waveguide. Moreover, integration of MEMS actuator with optical ring resonators overcomes the optical lithography challenges for patterning the small gap between cavity and waveguide. Different finite-element (FE) method simulations have been carried out in order to study the mechanical and optical operating characteristics of the ring resonator. The movable microring resonator can be displaced 1.33 μm with less than 3 V actuation voltage in 850 μs to control the transferred optical power and bandwidth of the resonator. Optical simulations show extinction ratios as high as 17 dB for the device with 90-nm gap spacing and 21.5 dB for the device with 60-nm gap spacing, respectively. In addition, the bandwidth of the filter is adjustable from 0.3 to 0.65 nm. [ABSTRACT FROM AUTHOR]

A miniature methane sensor composed of a long ultra-low loss waveguide and a micro-ring resonator filter is proposed with high sensitivity and good selectivity. This sensor takes advantage of the evanescent field to implement methane concentration detection at a near infrared band (1650 nm). In the sensor, two waveguides, a strip waveguide and a slot waveguide, are specially designed and discussed based on three common semiconductor materials, including silica, silicon nitride, and silicon. Through simulations and numerical calculations, we determine that for the strip waveguide, the optimal evanescent field ratio (EFR) is approximately 39.8%, while the resolution is 32.1 ppb using a 15-cm waveguide length. For the slot waveguide, the optimal EFR is approximately 61.6%, and the resolution is 20.8 ppb with a 15-cm waveguide length. [ABSTRACT FROM AUTHOR]

A micro scanning mirror is an optical device used to scan laser beams which can be used for Light Detection and Ranging (LiDAR) in applications like unmanned driving or Unmanned Aerial Vehicle (UAV). The MEMS scanning mirror's light-weight and low-power make it a useful device in LiDAR applications. However, the MEMS scanning mirror's small aperture limits its application because it is too small to deflect faint receiving light. In this paper, we present a Ti-alloy-based electromagnetic micro scanning mirror with very large-aperture (12 mm) and rapid scanning frequency (1.24 kHz). The size of micro-scanner's mirror plate reached 12 mm, which is much larger than familiar MEMS scanning mirror. The scanner is designed using MEMS design method and fabricated by electro-sparking manufacture method. As the experimental results show, the resonant frequency of the micro scanning mirror is 1240 Hz and the optical scanning angle can reach 26 degrees at resonance frequency when the actuation current is 250 mApp. [ABSTRACT FROM AUTHOR]

An ultrasonic probe consisting of two optical fiber-based miniaturized transducers for wideband ultrasound emission and detection is employed for the characterization of in vitro biological tissues. In the probe, ultrasound generation is obtained by thermoelastic emission from patterned carbon films in Micro-Opto-Mechanical-System (MOMS) devices mounted on the tip of an optical fiber, whereas acousto-optical detection is performed in a similar way by a miniaturized polymeric interferometer. The microprobe presents a wide, flat bandwidth that is a very attractive feature for ultrasonic investigation, especially for tissue characterization. Thanks to the very high ultrasonic frequencies obtained, the probe is able to reveal different details of the object under investigation by analyzing the ultrasonic signal within different frequencies ranges, as shown by specific experiments performed on a patterned cornstarch flour sample in vitro. This is confirmed by measurements executed to determine the lateral resolution of the microprobe at different frequencies of about 70 μm at 120 MHz. Moreover, measurements performed with the wideband probe in pulsed-echo mode on a histological finding of porcine kidney are presented, on which two different spectral signal processing algorithms are applied. After processing, the ultrasonic spectral features show a peculiar spatial distribution on the sample, which is expected to depend on different ultrasonic backscattering properties of the analyzed tissues. [ABSTRACT FROM AUTHOR]

Optical microelectromechanical system pressure sensors working on the principle of extrinsic Fabry-Perot (FP) interferometer are designed and fabricated for pressure range of 1-bar absolute. Anodic bonding of silicon with glass is performed under atmospheric pressure to form FP cavity. This process results in entrapment of gas in the sealed microcavity. The effect of trapped gas is investigated on sensor characteristics. A closed-loop solution is derived for the deflection of the diaphragm of a sealed microcavity pressure sensor. Phenomenon of "suppression of span" is brought out. The sensors are tested using white light interferometry technique. The residual pressure of the trapped gas is estimated from the experiments. The developed model has been used to estimate the deflection sensitivity of the free diaphragm and the extent of suppression of span after bonding. [ABSTRACT FROM AUTHOR]

The design and CMOS-compatible fabrication of stacked dielectric membranes are presented. The structures are intended for use as airgap-based interference filters operating in the UV-visible spectrum. In optical filters, maximizing the fill-factor, i.e. the ratio of the active area to the total area of the filter, is essential, which calls for minimum dimensions of the anchoring pillars and the openings that are required for the fabrication of the structures. This requirement necessitates the fabrication of large area free- standing membranes. Maintaining flatness over such a large area (> 1000μ m 2 ) membrane, as required by the optical application (deformation< λ/10), is challenging. While the thickness of the free-standing membrane is defined by the optical specification, the residual stress is the main force acting on the structure. Although an overall tensile residual stress can effectively stretch the membrane, the presence of a residual stress gradient causes the membrane to deform. Furthermore, a high residual stress results in the rupture of the membrane. These challenges in the fabrication of airgap-dielectric Bragg gratings are discussed. Higher-order optical designs were investigated to simultaneously satisfy both the mechanical and optical requirements. Bragg reflectors with one and two periods have been fabricated and characterized. The preliminary results are presented. [ABSTRACT FROM AUTHOR]