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Planar optical elements have attracted widespread attentions because of their precise light modulation. Liquid crystals (LCs) are well known for their applications in the current displaying field, and show great potential in planar optical elements with the development and innovation of LC micro-operation technology. However, previous researches on LC elements mainly involved only one type of optical manipulation, which inevitably limited the functional diversity. In this work, we propose a multifunctional LC element which integrates the surface display into a binary-phase focusing lens by controlling the complex amplitude of the incident light. The light modulation of the anisotropic LC molecule satisfies a sinusoidal variation, which can be regarded as the combination of a continuous amplitude modulation and a binary phase modulation. The element with millimeter size is then fabricated, and the experimental measurements agree well with our design with a high-definition surface pattern and high-quality optical focusing/imaging performance. Furthermore, as the complex amplitude modulation changes from sine to cosine function after rotating the sample by 45°, a bifocal lens with two different focal lengths is also demonstrated. We expect the proposed multifunctional LC elements can find applications in information multiplexing, image displaying, etc.

In this Letter, transverse and longitudinal liquid crystal bifocal lenses (LCBLs) are proposed to continuously control the relative intensity of two foci through a simple polarization control. The modulation of a LCBL comes from the geometric phase control and is designed through the principle of holography, where the object wave is a light field from two foci respectively formed by the left-circular polarized (LCP) and right-circular polarized (RCP) light, and the reference wave is the incident plane wave. Constructed millimeter-scale LCBLs are verified experimentally, and the foci are precisely formed at the preset plane. Besides, the relative intensity can be easily controlled with different weights of LCP and RCP light. The proposed strategy overcomes the shortcomings of previous bifocal lenses, such as a complex design method, a long optimization time, and an unchangeable relative intensity, and it is expected to find potential applications in parallel optical processing and optical interconnections.

Optical super-oscillatory lenses based on planar micro/nano structures have been demonstrated as promising alternatives for shaping wavefronts of light and realizing super-resolution images in a NA-limited optical system. However, as the super-oscillatory foci originated from the delicate interference of the light, the change of the parameters might destroy the hotspots, such as the incident wavelength. Here, a multiwavelength achromatic super-oscillatory metasurface (ASOM) is proposed through simultaneously controlling distinct wavelength-dependent wavefronts. The constructed multiwavelength ASOM is then verified numerically, and the foci are precisely formed at the same axial plane for the design wavelengths with resolution beyond the diffraction limit. We expect that our proposed multiwavelength controllable method will give more freedom for the designs of planar and lightweight components, which would be useful in optical applications, such as data storage, super-resolution imaging, holography, etc.

Benefiting from the memory effect (ME) for speckle intensity correlations, only one single-shot speckle pattern can be used for the high-quality recovery of objects. However, ME gives a restriction to the field of view (FOV) for imaging with scattering media. Objects beyond the ME region cannot be recovered and produce unwanted speckle patterns, which cause reduction in the speckle contrast and recovery quality. Nevertheless, all the spatial information from a large object is embedded in a single speckle image. Here, we extract the spatial information from these unavoidable speckle patterns and enlarge the FOV of the imaging system with scattering media. Regional point spreading functions, which are fixed and only need to be recorded once for all-time use, are employed to recover corresponding spatial regions of an object by deconvolution. Then, an automatic weighted averaging in an iterative process is performed to obtain the object with significantly enlarged FOV. Our results present an important advancement of imaging techniques with strongly scattering media.

Multispectral imaging plays an important role in many applications, from astronomical imaging and earth observation to biomedical imaging. However, current technologies are complex with multiple alignment-sensitive components and spatial and spectral parameters predetermined by manufacturers. Here, we demonstrate a single-shot multispectral imaging technique that gives flexibility to end users with a very simple optical setup, thanks to spatial correlation and spectral decorrelation of speckle patterns. These seemingly random speckle patterns are point spread functions (PSFs) generated by light from point sources propagating through a strongly scattering medium. The spatial correlation of PSFs allows image recovery with deconvolution techniques, while the spectral decorrelation allows them to play the role of tunable spectral filters in the deconvolution process. Our demonstrations utilizing optical physics of strongly scattering media and computational imaging present a cost-effective approach for multispectral imaging with many advantages.

A cylindrically symmetric plano-concave lens based on a one-dimensional (1D) Thue-Morse photonic quasicrystal (PQC) is proposed. Subwavelength focusing characteristics with an incident cylindrical vector beam are investigated. Numerical results reveal that the lens can exhibit polarization-independent, high-resolution, and low-side-lobe characteristics, simultaneously for near-field and non-near-field. Furthermore, the lens can achieve perfect focusing and size-independent characteristics with equal-proportion scaling of the size of the lens at the corresponding center frequency. The focusing mechanisms of the lens are explained by analyzing the transmission spectrum, dispersion relation of a 1D periodic photonic crystal, and transmission spectrum of the 1D Thue-Morse PQC.