RESUMEN
Chiral liquid crystals (CLCs) self-assemble into a helical structure and can efficiently reflect circularly polarized light with corresponding handedness. Utilizing a curved glass substrate and polymerization of photoaligned CLCs, the operation of focusing and diffraction of incident light can be performed efficiently by a single component. When focusing and diffraction in a planar CLC cell are combined between two glass plates, the imaging suffers from astigmatism in the resulting spectrum. In this work, we demonstrate the operation of a spectrometer with low astigmatism using a polymerized CLC layer on a curved substrate. Two samples are fabricated, and the resulting components are operating in the wavelength range of 500-650 nm. Numerical optical modeling is used to minimize transverse aberrations and obtain a highly linear mapping on a camera sensor. In this way, it is demonstrated that a single reflective thin-film optical CLC component with a thickness of only a few micrometers can be used to realize a compact and efficient spectrometer.
RESUMEN
Flat optics based on chiral liquid crystal (CLC) can be achieved using holographic polarization recording with the help of a photoalignment technique to vary the orientation of the optical axis in a thin CLC layer. A variety of reflective diffractive optical components with high efficiency and polarization selectivity can be realized employing this technique. In this work we discuss the use of CLC diffractive lenses in a spectrometer. The functionalities of two mirrors and a linear grating used in a traditional spectrometer are combined into a single holographic CLC component. Circularly polarized light entering through the slit can be reflected and projected onto a linear detector by the CLC component, with over 90% efficiency. This excellent optical functionality can be achieved with a micrometer thin CLC layer, offering the opportunity for device integration.