High extinction ratio, low insertion loss, optical switch based on an electrowetting prism

Dielectric elastomer-driven liquid prism enabling two-dimensional beam control

In this paper, a dielectric elastomer (DE)-driven liquid prism enabling two-dimensional beam control is proposed. The proposed liquid prism consists of a flexible driver and a liquid cavity. The glass plate is driven by DE to change the tilt angle of the liquid-solid interface for beam steering and field of view (FOV) tuning. The maximum optical deflection angle of 8.13° and response time of 76.77 ms were measured, the variable FOV capability was also verified. The proposed liquid prism can be used in beam modulation, microscope systems.

Fabrication and characterization of a two-dimensional individually addressable electrowetting microlens array

We demonstrate a two-dimensional, individually tunable electrowetting microlens array fabricated using standard microfabrication techniques. Each lens in our array has a large range of focal tunability from -1.7 mm to -∞ in the diverging regime, which we verify experimentally from 0 to 75 V for a device coated in Parylene C. Additionally, each lens can be actuated to within 1% of their steady-state value within 1.5 ms. To justify the use of our device in a phase-sensitive optical system, we measure the wavefront of a beam passing through the center of a single lens in our device over the actuation range and show that these devices have a surface quality comparable to static microlens arrays. The large range of tunability, fast response time, and excellent surface quality of these devices open the door to potential applications in compact optical imaging systems, transmissive wavefront shaping, and beam steering.

Electrically Tunable Lenses for Imaging and Light Manipulation

Optofluidics seamlessly combines optics and microfluidics together to construct novel devices for microsystems, providing flexible reconfigurability and high compatibility. By taking advantage of mature electronic fabrication techniques and flexible regulation of microfluidics, electrically actuated optofluidics has achieved fantastic optical functions. Generally, the optical function is achieved by electrically modulating the interfaces or movements of microdroplets inside a small chamber. The high refractive index difference (~0.5) at the interfaces between liquid/air or liquid/liquid makes unprecedented optical tunability a reality. They are suitable for optical imaging devices, such as microscope and portable electronic. This paper will review the working principle and recent development of electrical optofluidic devices by electrowetting and dielectrophoresis, including optical lens/microscope, beam steering and in-plane light manipulation. Some methods to improve the lens performance are reviewed. In addition, the applications of electrical microfluidics are also discussed. In order to stimulate the development of electrically controlled liquid lens, two novel designs derived from electrowetting and dielectrophoresis are introduced in this paper.

Adaptive liquid lens with a tunable field of view

In this paper, we demonstrate an adaptive liquid lens with a tunable field of view (FOV). The proposed liquid lens consists of an actuator and a lens chamber, the annular sheet is just placed on the liquid-liquid (L-L) interface in order to change the curvature and steer the tilt angle of the interface. Different from the conventional FOV adjustable lens combined with a liquid lens and a liquid prism, the proposed lens requires only one L-L interface to achieve the focal length change and FOV deflection. Moreover, the proposed lens reduces aberrations while maintaining high resolution. The experiments show that the optical power range is -27 m^-1 to 30 m^-1. It can realize the FOV deflection while tuning the focal length, with an angular resolution of 37"05. The proposed lens can be applied to telescopic system and microscopic system.

Spectrally tunable liquid resonator based on electrowetting

We present a tunable on-chip liquid resonator in conjunction with a tapered fiber coupling scheme. The resonator consists of a glycerol droplet submerged within an immiscible liquid bath, which mitigates the effects of environmental fluctuations. The platform is fabricated using standard semiconductor techniques, which enable the future integration of photonic components for an on-chip liquid resonator device. The liquid resonator maintains its high Q-factor on chip (10⁵) due to surface tension forming an atomically smooth liquid-liquid interface. Higher Q-factor resonance modes experienced linewidth broadening due to the random excitation of thermal capillary vibrations. Spectral tuning is demonstrated using the electrowetting effect, increasing the surface's wettability and an expansion in the droplet diameter. A maximum spectral tuning of 1.44 nm ± 5 pm is observed by applying 35 V. The tuning range is twice the free spectral range (FSR) of 0.679 nm measured at a pumping wavelength range of 770-775 nm. A 2D axisymmetric finite-element simulation shows resonance modes in good agreement with experimentally measured spectra and with predicted tuning speeds of 20 nm/s.

Compact, broadband, and low-loss multimode optical switch based on phase-change material for mode division multiplexing systems

Mode-division multiplexing (MDM) technology is one of the suitable approaches to increase data transmission capacity in photonic integrated circuits. Multimode optical switches play an important role in MDM interconnection networks. In this article, we present a multimode on-off optical switch using Ge₂Sb₂Se₄Te₁ phase-change material for the first two TE modes (TE0 and TE1) and the first two TM modes (TM0 and TM1) in a wide wavelength range between 100 nm to around 1550 nm. The 3D finite-difference time-domain simulations indicate that for each propagating mode across the bandwidth, the insertion loss and extinction ratio are less than 0.80 dB and more than 20.21 dB, respectively. The proposed switch has a compact footprint of 10.7µm×3µm. The presented switch also tolerates a ±20nm change in the waveguide width, a ±10nm silicon waveguide height deflection, and a ±5nm GSST thickness variation with an insertion loss lower than 0.91 dB and an extinction ratio higher than 19.04 dB.

Optical-Switch-Enabled Microfluidics for Sensitive Multichannel Colorimetric Analysis

The implementation of colorimetric analysis within microfluidic environments engenders significant benefits with respect to reduced sample and reagent consumption, system miniaturization, and real-time measurement of flowing samples. That said, conventional approaches to colorimetric analysis within microfluidic channels are hampered by short optical pathlengths and single-channel configurations, which lead to poor detection sensitivities and low analytical throughputs. Although the use of multiplexed light source/photodetector modules allows for multichannel analysis, such configurations significantly increase both instrument complexity and cost. To address these issues, we present a four-channel colorimetric measurement scheme within an optical-switch-enabled microfluidic chip (OSEMC) fabricated by two-photon stereolithography. The integration of optical switches enables sequential signal readout from each detection channel, and thus, only a single light source and a photodetector are required for operation. Optical switches can be controlled in a bespoke manner by changing the medium in the switch channel between a "light-transmitting" fluid and a "light-blocking" fluid using pneumatic microvalves. Such optical switches are characterized by fast response times (approximately 200 ms), tunable switching frequencies (between 0.1 and 1.0 Hz studied), and excellent stability. Operational performance demonstrates both good sensitivity and reproducibility through the colorimetric analysis of nitrite and ammonium samples using four detection channels. Furthermore, the use of OSEMC for parallel and real-time analysis of flowing samples is investigated via characterization of the adsorption kinetics of tartrazine on activated charcoal and the catalytic reaction kinetics of horseradish peroxidase (HRP).