Abstract
A set of parallel microfluidic channels behaving as a diffraction grating operating in the Raman-Nath regime has been fabricated and studied. The diffraction efficiency of such structure can be tuned by selecting a liquid with a particular refractive index and/or optical anisotropy. Alternatively the optical properties of the liquid can be characterised by measuring the diffraction efficiency and the state of polarization of the diffracted beam. In this work, the microfluidic channels under study have been filled with penicillin molecules dissolved in water. Due to the chirality of the penicillin, the liquid has been found to have circular birefringence of 2.14 × 10-7. The addition of the anisotropic liquid modifies the polarization properties of the microfluidic diffraction grating. The diffraction efficiency of the grating has been characterised for different probe beam wavelengths and states of polarization. Currently the diffraction efficiency of the device is low - 1.7%, but different approaches for its improvement have been discussed.
Highlights
Optical components made of glass, plastic and other materials like lenses, mirrors, windows, beamsplitters, prisms, gratings, polarization gratings, holograms and others show permanent characteristics, such as focal length, dispersion, diffraction efficiency and more.In the literature attempts have been shown to fabricate permanent gratings that can be used as waveplates
Regarding the polarization gratings attempts have been carried out to fabricate them with tunable or programmable characteristics. Their properties when probed with polarized light can be changed at will. These polarization gratings are based on nematic liquid crystals that respond to voltage
Reference [22] reports on the fabrication of polarization gratings by utilizing liquid crystal cells patterned by an Atomic Force Microscope (AFM) stylus
Summary
Optical components made of glass, plastic and other materials like lenses, mirrors, windows, beamsplitters, prisms, gratings, polarization gratings, holograms and others show permanent characteristics, such as focal length, dispersion, diffraction efficiency and more. Regarding the polarization gratings attempts have been carried out to fabricate them with tunable or programmable characteristics That is, their properties when probed with polarized light can be changed at will. Their properties when probed with polarized light can be changed at will These polarization gratings are based on nematic liquid crystals that respond to voltage. Reference [22] reports on the fabrication of polarization gratings by utilizing liquid crystal cells patterned by an Atomic Force Microscope (AFM) stylus. The use of high voltages and a cumbersome fabrication process including a lengthily processing time with the AFM stylus make these devices impractical Another approach to fabricate polarization gratings is reported in Refs.
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