Electrowetting-actuated optical switch based on total internal reflection

Optofluidic modulator based on thermoplasmonically controlled liquid-liquid interface

We report a thermoplasmonically actuated optical modulator based on a liquid-liquid interface decorated with self-assembled Au nanoparticles (Au NPs). The system comprises heptane (top layer) and water (bottom layer), and an Au NPs array at their interfaces. Focused excitation with the plasmonic wavelength (532 nm) generates a localized temperature rise at the interface (ΔT=3.2±0.7^∘C), resulting in a thermocapillary flow. We optimized the temperature gradient and the heptane layer thickness so that the resulting thermocapillary flow leads to the formation of a "self-healing hole" at the irradiating zone, which we exploited as an all-optical modulator. A signal beam (655 nm) positioned through the top layer, parallel to the interface, gives a maximum output when the layer is intact (no-hole situation, ON state) and a minimum output when the hole is present (OFF state). Nearly 100% optical modulation is achieved in a reversible manner, highlighting the potential of responsive and reconfigurable fluid-fluid interfaces for optical applications.

Thermo-Optical Switching Effect Based on a Tapered Optical Fiber and Higher Alkanes Doped with ZnS:Mn

The paper investigates the effect of thermo-optic switching resulting from the hybrid combination of a tapered optical fiber (TOF) with alkanes doped with nanoparticles of zinc sulfide doped with manganese (ZnS:Mn NP). Presented measurements focused on controlling losses in an optical fiber by modification of a TOF cladding by the alkanes used, characterized by phase change. Temperature changes cause power transmission changes creating a switcher or a sensor working in an ON-OFF mode. Phase change temperatures and changes in the refractive index of the alkane used directly affected power switching. Alkanes were doped with ZnS:Mn NPs to change the hysteresis observed between ON-OFF modes in pure alkanes. The addition of nanoparticles (NPs) reduces the difference between phase changes due to improved thermal conductivity and introduces extra nucleating agents. Results are presented in the wide optical range of 550-1200 nm. In this investigation, hexadecane and heptadecane were a new cladding for TOF. The higher alkanes were doped with ZnS: Mn NPs in an alkane volume of 1 wt.% and 5 wt.%. The thermo-optic effect can be applied to manufacture a thermo-optic switcher or a temperature threshold sensor.

1550 nm infrared/visible light switchable liquid optical switch

In this paper, a liquid optical switch is proposed, and the 1550 nm infrared/visible switching function based on hydraulic control can be realized. An infrared light switch cavity, a visible light cavity and a liquid control cavity are stacked to form the main framework of the device. The glycerol, dyed liquid, and transparent liquid are filled in the cavities, respectively. Two elastic films are fabricated between the cavities for controlling the liquid volume of the cavities. With such a structure, in the initial state, the 1550 nm infrared light and visible light are absorbed by the glycerol and dyed liquid, respectively. The device shows infrared light-off and visible light-off states. When the elastic film is actuated by the liquid pressure, the shape of the elastic film can be changed. Once the elastic film touches to the substrate, a light channel can be formed so that the infrared light or visible light can pass through it. It shows infrared light-on or visible light-on states. In this way, the device can be worked as an infrared light and visible light switchable optical switch. The experiments show that the device can obtain the optical attenuation from ∼1.02 dB to ∼18.24 dB for 1550 nm infrared light optical switch and ∼0.66 dB to ∼8.70 dB @ λ=450 nm; ∼0.62 dB to ∼8.74 dB @ λ=532 nm; ∼0.77 dB to ∼9.00 dB @ λ=633 nm for visible light optical switch. The device has potential applications in the fields of optical fiber communications, variable optical attenuators, and light shutters.

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

An optical switch based on an electrowetting prism coupled to a multimode fiber has demonstrated a large extinction ratio with speeds up to 300 Hz. Electrowetting prisms provide a transmissive, low power, and compact alternative to conventional free-space optical switches, with no moving parts. The electrowetting prism performs beam steering of ±3° with an extinction ratio of 47 dB between the ON and OFF states and has been experimentally demonstrated at scanning frequencies of 100-300 Hz. The optical design is modeled in Zemax to account for secondary rays created at each surface interface (without scattering). Simulations predict 50 dB of extinction, in good agreement with experiment.

Variable aperture with graded attenuation combined with adjustable focal length lens

In this paper, we demonstrate a variable aperture with graded attenuation combined with adjustable focal length lens actuated by hydraulic control. Two cylindrical chambers and a middle substrate are stacked to form the device body. An elastic film is fabricated in the middle substrate like a sandwich. In the initial state, the dyed liquid is fully covered on the elastic film. The variable aperture shows the state of the maximum optical attenuation. When the bottom chamber is injected with liquid, the elastic film can form a convex surface. The dyed liquid will be pushed to the side wall of the chamber by the raised elastic film and the optical attenuation can be varied by changing the volume of the injected liquid. The proposed device can achieve both the variable attenuator function and the variable-focus lens function. The experiments show that the variable aperture can obtain dynamic attenuation ranges from 33.01 dB to 0.71 dB, and the zoom liquid lens can reach 2.9☓magnifying power. The device can be applied in imaging systems and fiber-optic communications.

Enhanced Thermo-Optical Switching of Paraffin-Wax Composite Spots under Laser Heating

Thermo-optical switches are of particular significance in communications networks where increasingly high switching speeds are required. Phase change materials (PCMs), in particular those based on paraffin wax, provide wealth of exciting applications with unusual thermally-induced switching properties, only limited by paraffin's rather low thermal conductivity. In this paper, the use of different carbon fillers as thermal conductivity enhancers for paraffin has been investigated, and a novel structure based on spot of paraffin wax as a thermo-optic switch is presented. Thermo-optical switching parameters are enhanced with the addition of graphite and graphene, due to the extreme thermal conductivity of the carbon fillers. Differential Scanning Calorimetry (DSC) and Scanning electron microscope (SEM) are performed on paraffin wax composites, and specific heat capacities are calculated based on DSC measurements. Thermo-optical switching based on transmission is measured as a function of the host concentration under conventional electric heating and laser heating of paraffin-carbon fillers composites. Further enhancements in thermo-optical switching parameters are studied under Nd:YAG laser heating. This novel structure can be used in future networks with huge bandwidth requirements and electric noise free remote aerial laser switching applications.

Large extinction ratio optical electrowetting shutter

A large extinction ratio optical shutter has been demonstrated using electrowetting liquids. The device is based on switching between a liquid-liquid interface curvature that produces total internal reflection and one that does not. The interface radius of curvature can be tuned continuously from 9 mm at 0 V to -45 mm at 26 V. Extinction ratios from 55.8 to 66.5 dB were measured. The device shows promise for ultracold chip-scale atomic clocks.