We proposed and demonstrated an integrated high energy efficient and high linearly polarized InGaN/GaN green LED grown on (0001) oriented sapphire with combined metasurface polarizing converter and polarizer system. It is different from those conventional polarized light emissions generated with plasmonic metallic grating in which at least 50% high energy loss occurs inherently due to high reflection of the transverse electric (TE) component of an electric field. A reflecting metasurface, with a two dimensional elliptic metal cylinder array (EMCA) that functions as a half-wave plate, was integrated at the bottom of a LED such that the back-reflected TE component, that is otherwise lost by a dielectric/metal bi-layered wire grids (DMBiWG) polarizer on the top emitting surface of the LED, can be converted to desired transverse magnetic (TM) polarized emission after reflecting from the metasurface. This significantly enhances the polarized light emission efficiency. Experimental results show that extraction efficiency of the polarized emission can be increased by 40% on average in a wide angle of ±60° compared to that with the naked bottom of sapphire substrate, or 20% compared to reflecting Al film on the bottom of a sapphire substrate. An extinction ratio (ER) of average value 20 dB within an angle of ±60° can be simultaneously obtained directly from an InGaN/GaN LED. Our results show the possibility of simultaneously achieving a high degree of polarization and high polarization extraction efficiency at the integrated device level. This advances the field of GaN LED toward energy efficiency, multi-functional applications in illumination, display, medicine, and light manipulation.
In this study, we propose a method for calculating a large scale high resolution synthetic color rainbow hologram using the frequency domain splicing technique. This method is motivated by the observation that if the plane wave is used as the reference light, the spectra of the three primary colors of the object light in the color rainbow hologram frequency domain are mutually separated frequency bands. According to this principle, the color views of different angles of a colored 3D object are separated and interpolated, and 2D Fourier transform is performed to form an object light spectrum distribution of the color rainbow hologram. Following the operation, efficient one-dimensional Fourier inverse transform in the row and column directions of the frequency is conducted. The proposed method is able to achieve a significant boost in terms of large scale high resolution hologram computational speed. We demonstrate that a synthetic color rainbow hologram with a size of 30 × 30 mm and a resolution of 94 340 × 94 340 is achieved through our holographic printing system with an unprecedented time of only 25 min. The method is also able to achieve a visually appealing computer generated white light color rainbow hologram, thus having great potential to be used for a practical holographic 3D display.
We investigate the ultradeep subwavelength imaging of a superlens with a surface plasmon polariton (SPP) cavity. A silver layer is added in the imaging region of the superlens to form an Ag film lens/photoresist/Ag layer cavity, in which the long-range plasmon mode is drastically suppressed and the field of the imaging is significantly amplified and extended over to the entire imaging region due to the SPP resonance inside the cavity. Results show that much improved quality of image with much suppressed sidelobes and much extended depth of focus can be obtained with the cavity structure when compared with the conventional open structure. This is confirmed by the transfer function of the system, which becomes flatter with the cavity structure. The proposed method provides a novel and practically feasible way to achieve images with both high resolution and large depth of field.
A fast calculation method for a full parallax high-resolution hologram is proposed based on elemental light field image (EI) rendering. A 3D object located near the holographic plane is firstly rendered as multiple EIs with a pinhole array. Each EI is interpolated and multiplied by a divergent sphere wave and interfered with a reference wave to form a hogel. Parallel acceleration is used to calculate the high-resolution hologram because the calculation of each hogel is independent. A high-resolution hologram with the resolution of 200,000 × 200,000 pixels is calculated within only eight minutes. Full parallax high-resolution 3D displays are realized by optical reconstructions.
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