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JMEMS Letters A Liquid Optical Phase Shifter With an Embedded Electrowetting Actuator
Abstract
We demonstrate an electrowetting-based liquid optical phase shifter. The phase shifter consists of two immiscible liquid layers with different refractive indices. Sandwiched between the two liquids is a rigid membrane that moves freely along the optical axis and is supported by a compliant surround. When applied with a pressure, the thicknesses of both liquid layers change, which induces a difference in optical path, resulting in a phase shift. A miniaturized electrowetting-based actuator is used to produce hydraulic pressure. A multi-layered SU8 bonded structure was fabricated. A phase shift of 171° was observed when the device was incorporated in the Mach-Zehnder interferometer and driven with 100 V. [2016-0201]
... In 2017, A. O. Ashtiani proposed an electrowetting driven liquid tunable optical phase shifter composed of multi-layer SU-8. The device can achieve a phase shift of 171°with a response time of 110 ms by applying 100 V voltage [22,23]. In 2019, Qiong-Hua Wang reported an optofluidic variable optical path modulator based on electrowetting, which is used in an imaging system to compensate the back focal length. ...
... where n 1 and n 2 are the refractive indices of insulating liquid and conductive liquid, respectively, h 1 and h 2 are the heights of the two liquids in the inner chamber. When the voltage is applied to the planar electrode, the wettability of the conductive liquid changes due to electrowetting effect, and the insulating droplet is squeezed inward [22,25]. Since the overall volume of the droplet must remain constant, this squeezing means that the contact angle of the insulating droplet increases. ...
... According to the Eq. (3), the relative variation of the phase can be written as [22]: ...
In this paper, an optofluidic phase modulator based on electrowetting is presented. The modulator consists of an inner and outer chamber. Two immiscible liquids are filled into the chambers, and a transparent sheet is fixed between the liquid-liquid interface to obtain a flat interface. By applying different voltages to the modulator, the flat interface moves up and down leading to the change of optical path length. Consequently, the variation of the optical path in the proposed modulator exploits the ability to alter the optical phase. To prove the concept, a prototype of the phase modulator is fabricated in experiment, and the ability of phase modulation is detected. Our proposed modulator performs optical phase shift up to ∼6.68 π driven with 150 V. Widespread applications of such an optofluidic phase modulator is foreseeable.
... Microfluidic controlling technology plays a critical role in micro-total analysis systems or lab-on-a-chip systems. [1][2][3] The controllable adjustment of the microfluidic can be realized by various methods, including thermal, [4] mechanical force, [5] dielectrowetting, [6][7][8] electrowetting, [9][10][11][12][13][14][15][16][17][18][19] and so on. Electrowetting technology has been found numerous potential applications in prism, [11,12] liquid lens, [13] displays, [14] labon-a-chip, [15] and light valve. ...
In this paper, an optofluidic phase modulator based on dielectrowetting is designed and fabricated to adjust the optical phase. Two liquids are filled in the device, and a transparent sheet is employed at the liquid interface to keep the interface flat. When different voltages are applied to the modulator, the flat interface moves up and down, leading to the variation of the optical phase. A theoretical model is constructed to predict the optical phase shift quantitatively, and the phase regulation ability is also tested experimentally. Our modulator realizes continuous adjustment of the optical phase in a certain range by the operation of voltage adjustment. When the voltage is increased to 150 V, the optical phase modulation range of our proposed modulator can reach 9.366 π.
A 2×2 optofluidic switch chip with an air shutter is proposed. It has a simple structure, small volume, small crosstalk, large extinction ratio, small polarization-dependent loss, and broad operation waveband (400-1700 nm). This 2×2 switch chip has good scalability and can form a number of optical switches by using different microfluidic driving technologies. The research results show that the microchannel width has great influence on the switch performances in "on" state, where the comprehensive performances of the optical switch are the best at 4.0 μm width. By replacing the original symmetrical structure with an optimized semi-tapered structure, the switch performances are further improved. After the structure and parameters are optimized, for 1310 nm wavelength, the insertion losses of the proposed switch are 0.41 dB in "on" state and 0.15 dB in "off" state, the extinction ratios are 52.5 dB in "on" state and 28.3 dB in "off" state, and the crosstalks are -28.8 dB in "on" state and -52.6 dB in "off" state.
In this paper, we propose a light intensity and field of view (FOV) controlled adaptive fluidic iris. A 90° twisted-nematic liquid crystal (TNLC) cell and two orthogonal polarizers are attached on the substrate. When a voltage is applied to TNLC, it can change the phase of the incident light, leading to change in the light intensity. A black mask is then placed in the middle of the chamber; when changing the hydraulic pressure from the inlet and outlet, the black mask can move within the chamber. It is equivalent to changing the iris position along the optical axis. The iris, therefore, can control the FOV in an optical system. The experiments show that the device can control the light intensity from 100% to 0% by applying a voltage of 9 V on the TNLC cell. The proposed device can be applied in imaging systems and optical attenuators.
A high speed focus control microelectromechanical systems (MEMS) mirror with a step response time of 100 μsec and small-displacement bandwidth of 25 kHz is reported for a 3 mm diameter, electrostatically actuated SU-8 membrane mirror. The dominant effect limiting the mirror bandwidth is viscous air damping, and the innovation we describe is the use of a perforated counter-electrode backplate that facilitates air flow underneath the membrane. We have adopted a model, originally developed for a MEMS microphone, to engineer the damping characteristics and design the air hole patterns. Cryogenic deep silicon etching creates through-wafer perforations in the backplate, and fabricated devices achieve wide-bandwidth actuation. The design approach, fabrication process, and dynamic characterization of the MEMS mirrors are shown. Finally, the focus control mirror is used in a confocal microscope for fast axial focus scanning to provide x-z cross-sectioned in vivo images.
A technique called optical coherence tomography (OCT) has been developed
for noninvasive cross-sectional imaging in biological systems. OCT uses
low-coherence interferometry to produce a two-dimensional image of
optical scattering from internal tissue microstructures in a way that is
analogous to ultrasonic pulse-echo imaging. OCT has longitudinal and
lateral spatial resolutions of a few micrometers and can detect
reflected signals as small as ~10-10 of the incident optical
power. Tomographic imaging is demonstrated in vitro in the peripapillary
area of the retina and in the coronary artery, two clinically relevant
examples that are representative of transparent and turbid media,
respectively.
This paper describes a method for fabricating micronozzles using low-temperature wafer-level adhesive bonding with SU-8. The influence of different parameters on the bonding of structured wafers has been investigated. The surface energies of bonded wafers are measured to be in the range of 0.42–0.56 J m−2, which are comparable to those of some directly bonded wafers. Converging–diverging nozzle structures with throat widths as small as 3.6 µm are formed in an SU-8 film bonded with another SU-8 intermediate layer to produce sealed micronozzles. A novel interconnection technique is developed to interface and test the micronozzles with a macroscopic fluid delivery system to demonstrate the feasibility of the fabrication process. Leakage test results show that this low-temperature wafer bonding process is a viable MEMS fabrication technique for microfluidic applications.
The current status of lithium-niobate external-modulator
technology is reviewed with emphasis on design, fabrication, system
requirements, performance, and reliability. The technology meets the
performance and reliability requirements of current 2.5-, 10-, and
40-Gb/s digital communication systems, as well as CATV analog systems.
The current trend in device topology is toward higher data rates and
increased levels of integration. In particular, multiple high-speed
modulation functions, such as 10-Gb/s return-to-zero pulse generation
plus data modulation, have been achieved in a single device
Introduction Fundamental Concepts Advantages of PSI Methods of Phase Shifting Detecting the Wavefront Phase Data Collection PSI Algorithms Phase Shift Calibration Error Sources Detectors and Spatial Sampling Quality Functions Phase Unwrapping Aspheres and Extended Range PSI Techniques Other Analysis Methods Computer Processing and Output Implementation and Applications Future Trends for PSI
In this paper, we introduce an electrode design for electrohydrodynamically actuated liquid microlenses. The effective electrode areal density radially increases which results in centering of the liquid tunable microlens with a planar device structure. A model was developed to demonstrate the centering mechanism of the liquid microlens. 3D electrostatic simulation was conducted and validity of the idea was examined. A simple fabrication process was developed that uses a surface modified SU-8 as the insulator. The focal length of the microlens was measured to vary from 10.1 mm to 5.8 mm as the voltage varied from zero to 100 V.
In published literature, it is widely reported that the plasma treatment and funtionalization with Octadecyltrichlorosilane (OTS) self-assembled monolayer (SAM) can individually alter the wetting properties of SU8 surface. A combination of the two approaches gives better results and the synergism of the two approaches produces a superhydrophobic SU8 surface, which is presented in this work. We have investigated various composition of plasma for treatment of SU8 surfaces and permuted the treated SU8 surfaces with deposition of OTS SAM. In all such synergized experiments, we obtained water contact angle higher than 150°, which is much higher than the one that can be obtained with individual application of the two approaches. The combined approach presented in this work is suitable for bulk production of superhydrophobic surface, and is a mask-less process, which makes it cost effective. The surface topography, wetting, and chemical properties of SU8 surfaces were characterized using the contact angle goniometry, atomic force microscopy, FTIR, Raman, and XPS spectra. The superhydrophobic SU8 surfaces were observed to be stable even after five months. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41934.
This paper presents an all-fiber, fully-optically controlled, optical-path length modulator based on highly absorbing optical fiber. The modulator utilizes a high-power 980 nm pump diode and a short section of vanadium-co-doped single mode fiber that is heated through absorption and a non-radiative relaxation process. The achievable path length modulation range primarily depends on the pump's power and the convective heat-transfer coefficient of the surrounding gas, while the time response primarily depends on the heated fiber's diameter. An absolute optical length change in excess of 500 µm and a time-constant as short as 11 ms, were demonstrated experimentally. The all-fiber design allows for an electrically-passive and remote operation of the modulator. The presented modulator could find use within various fiber-optics systems that require optical (remote) path length control or modulation.
We discuss a refined, hybrid rf/optical technique for studying sub‐Doppler saturated absorption/dispersion resonances with excellent precision and symmetry. Sensitivity is limited mainly by fundamental noise in the signal. Resonance profiles obtained in I 2 are in remarkable agreement with theory. The method promises a new level of accuracy for laser locking to an optical resonance.
This paper deals with electrowetting (EW) and electrowetting-on-dielectric (EWOD) principles applied to microfluidic devices. EW and EWOD are principles that can control wettability of liquids on solid surfaces using electric potential. While EW is controlling wettability of a certain electrolyte on a metal electrode by varying electric energy across the electrical double layer (EDL), EWOD applies to virtually any aqueous liquid by varying electric energy across the thin dielectric film between the liquid and conducting substrate. These driving mechanisms have many advantages. By electrically changing the wettability of each of the electrode patterns on a surface, a liquid on these electrodes can be shaped and driven along the active electrodes, making microfluidics extremely simple both for device fabrication and operation. It is also worth noting that, driven by surface tension, the mechanism becomes more effective as the size of the device becomes smaller. This paper describes fundamental concepts and the proof-of-concept experiments, modeling and design, microfabrication processes, and initial testing results for the microfluidic devices based on the EW and EWOD principles.
We have developed ultrashort pulse generation by the electrooptic
modulation method, where continuous-wave laser light of any wavelength
can be converted to trains of ultrashort optical pulses with a variable
and high repetition frequency by means of an electrooptic phase
modulator for the generation of deeply chirped light, and an optical
group-delay-dispersion circuit or an optical synthesizer for the
compression of the chirped light. Adopting the technologies of domain
inversion and guided-wave optics to this electrooptic modulation method,
it will be possible to realize integrated ultrashort optical pulse
generators
We developed a tunable wedge prism by electrowetting actuation. Our prism can shift the field of view to the left or to the right and is useful for small cameras and endoscopes because its field of view can be changed without the need for large instruments. It consists of two plates that face each other, and a liquid is sandwiched between them. The liquid and plates form a wedge when the angle between the plates is changed. We used electrowetting to change the angle between the plates. The wedge prism is small because the liquid driven by electrowetting works as a prism. In addition, the prism produces a clear field of view because its optical flatness is determined by the flatness of the plates.