Image restoration through thin turbid layers by correlation with a known object.

A method to recover the image of an object behind thin turbid layers is developed by wavefront shaping technique. The optimized wavefront is generated by modulating the scattering light of a known object with a spatial light modulator. A Pearson Correlation Coefficient is introduced as a cost function for the optimization. A beam scanning method based on optical memory effect is proposed to further enlarge the Field-of-View (FOV). The experimental results show good fidelity and large FOV of the recovered image.

Surface Modification of Cyclic-Olefin-Copolymer (COC)-Based Microchannels for the Large-Scale Industrial Production of Droplet Microfluidic Devices.

The copolymers of cycloolefin (COC), a type of thermoplastic material, have been widely used for the large-scale industrial fabrication of droplet microfluidic devices, which is often performed using hot-embossing or injection-molding techniques. The generation of droplets and the uniformity of droplet sizes are significantly affected by the surface wettability of COC during fabrication and the pressure stability of the employed fluid pump during operation. In order to alleviate the effects of undesirable surface wettability and pressure variation on the generation of droplets in COC-based devices, a simple surface modification procedure was applied to hydrophobically modify the surfaces of COC-based microchannels for large-scale industrial production. The surface modification procedure consisted of an oxygen plasma treatment of the polymer surface followed by a solution-phase reaction in fluorocarbon solvent. The experimental results demonstrate that following the proposed surface modification, the COC droplet microfluidic devices could stably generate microvolume water droplets with a small coefficient of variation, even if the pressure of the dispersed phase (water) fluctuated. The durability test results regarding the modified surfaces show that the hydrophobicity of the modified COC surfaces could be sustained for up to four months, deteriorating with time thereafter. Our study can provide a potential solution useful in and guidance for the large-scale industrial production of droplet microfluidic devices for various applications, including polymerase chain reaction and single-cell analysis.

Spectral control of broadband light through random media by wavefront shaping.

A random medium can serve as a controllable arbitrary spectral filter with spectral resolution determined by the inverse of the interaction time of the light in the medium. We use wavefront shaping to implement an arbitrary spectral response at a particular point in the scattered field. We experimentally demonstrate this technique by selecting either a narrow band or dual bands with a width of 5.5 nm each.

Polarization control of multiply scattered light through random media by wavefront shaping.

We show that the polarization state of coherent light propagating through an optically thick multiple scattering medium can be controlled by wavefront shaping, that is, by controlling only the spatial phase of the incoming field with a spatial light modulator. Any polarization state of light at any spatial position behind the scattering medium can be attained with this technique. Thus, transforming the random medium to an arbitrary optical polarization component becomes possible.

High- sensitivity bilayer nanofiber film based on polyvinyl alcohol/sodium alginate/polyvinylidene fluoride for pork spoilage visual monitoring and preservation.

A colorimetric bilayer film for pork freshness detection and preservation was developed using electrospinning technique. The bilayer film consisted of a layer with polyvinyl alcohol - sodium alginate - alizarin as sensor layer and a layer with polyvinylidene fluoride - vanillin as antibacterial layer. The water contact angle of bilayer film was larger than the single colorimetric layer. The color sensitivity to the ammonia of the bilayer film was higher, with an ΔE value of 47.99. The film could display color shifts from yellow to purple with the naked eye is critical for checking pork freshness. In addition, the bilayer film exhibited sensitive antibacterial activity, with an inhibition zone against S. aureus (8.3 mm) and E. coli (14.7 mm), respectively. Finally, the bilayer film was applied to freshness monitoring of pork. The film displayed significant color changes and prolonged the pork shelf life by 24 h at 25 °C.

Phase controlled beam combining with nonlinear frequency conversion.

A phase controlled beam combining via nonlinear optical conversion is proposed and demonstrated. This process involves the combining of the fields at the second harmonic frequency generated by non-collinear input fields. The arrangement of the excitation configuration allows the generated second-harmonic light waves to propagate collinearly, with phases coherently correlated. The manipulation of the conversion efficiency is then possible with the phase control of the input fields. The combined second-harmonic fields are shown to be conveniently and robustly variable from zero to a maximum value that greatly exceeds the second-harmonic field generated by a single laser beam. By using a self-adaptive control algorithm, it is possible to optimize the output without prior knowledge on each beamlet property. Either the second-harmonic output beam profile or the total second-harmonic output power can be optimized with the control algorithm.