Pancharatnam-Berry Optical Elements Research Articles

Correcting the wavelength-induced phase deviation of Pancharatnam-Berry lenses.

Liquid-crystal-based Pancharatnam-Berry optical elements are widely used in virtual reality and augmented reality. However, the mismatch between exposure wavelength and operating wavelength leads to an undesirable phase deviation to the lenses, which in turn causes severe aberration especially when the f-number is small. To overcome the mismatched wavelength problem and to obtain a nearly ideal lens phase profile, a new exposure method using two template lenses with different focal lengths is proposed and experimentally validated. Our results indicate that such a lens indeed exhibits a better imaging performance than that fabricated by traditional interference method.

Planar Alvarez tunable lens based on polymetric liquid crystal Pancharatnam-Berry optical elements.

Virtual reality (VR) and augmented reality (AR) have widespread applications. The vergence-accommodation conflict (VAC), which causes 3D visual fatigue, has become an urgent challenge for VR and AR displays. Alvarez lenses, with precise and continuously tunable focal length based on the lateral shift of its two sub-elements, are a promising candidate as the key electro-optical component in vari-focal AR display systems to solve the VAC problem. In this paper, we propose and fabricate a compact Alvarez lens based on planar polymetric liquid crystal Pancharatnam-Berry optical elements. It can provide continuous diopter change from -1.4 D to 1.4 D at the wavelength of 532 nm with the lateral shift ranging from -5 mm to 5 mm. We also demonstrate an AR display system using this proposed Alvarez lens, where virtual images are augmented on the real world at different depths.

Emerging Near-eye Displays with Pancharatnam-Berry Optical Elements

Emerging Near-eye Displays with Pancharatnam-Berry Optical Elements

Emerging Near-eye Displays with Pancharatnam-Berry Optical Elements

Emerging Near-eye Displays with Pancharatnam-Berry Optical Elements

Generalization of Pancharatnam-Berry phase interference theory for fabricating phase-integrated liquid crystal optical elements

ABSTRACTIn this paper, we extended the methods for fabricating phase-integrated liquid crystal optical elements by interfering of orthogonal circularly polarised beams with different PB phase and generalised those methods as Pancharatnam-Berry (PB) phase interference theory. The generalised theory exhibits two kinds of interference ways. The first way takes place when various PB optical elements (PBOEs) are sequentially illuminated by a linearly polarised light in half-wave condition. The second way happens when the first PBOE is illuminated by a circularly polarised light in quarter-wave condition while the following PBOEs are in half-wave condition. The fabrication of fork polarisation gratings based on this generalised theory is used to confirm the two different interference ways. The generalised theory can better describe the interference of orthogonal circularly polarised beams with different PB phase and can be widely used for fabricating phase-integrated liquid crystal optical elements using existing PB phase device, which may promote the development and extensive applications of the PBOEs.

Holographic Silicon Metasurfaces for Total Angular Momentum Demultiplexing Applications in Telecom

The simultaneous processing of orbital angular momentum (OAM) and polarization has recently acquired particular importance and interest in a wide range of fields ranging from telecommunications to high-dimensional quantum cryptography. Due to their inherently polarization-sensitive optical behavior, Pancharatnam–Berry optical elements (PBOEs), acting on the geometric phase, have proven to be useful for the manipulation of complex light beams with orthogonal polarization states using a single optical element. In this work, different PBOEs have been computed, realized, and optically analyzed for the sorting of beams with orthogonal OAM and polarization states at the telecom wavelength of 1310 nm. The geometric-phase control is obtained by inducing a spatially-dependent form birefringence on a silicon substrate, patterned with properly-oriented subwavelength gratings. The digital grating structure is generated with high-resolution electron beam lithography on a resist mask and transferred to the silicon substrate using inductively coupled plasma-reactive ion etching. The optical characterization of the fabricated samples confirms the expected capability to detect circularly-polarized optical vortices with different handedness and orbital angular momentum.

High‐efficiency switchable optical elements for advanced head‐up displays

AbstractThe Pancharatnam‐Berry optical elements (PBOEs) are utilized to enhance the performance of head‐up displays (HUDs). The Pancharatnam‐Berry lenses (PBLs) provide varifocal functionality and compensate chromatic aberrations, while the Pancharatnam‐Berry deflectors (PBDs) can function as optical combiners and waveguide couplers. Moreover, the Rigorous coupled wave analysis (RCWA) based on the scattering matrix is developed and applied in the structure optimization of PBOEs for HUD applications.

Pancharatnam–Berry optical elements for head-up and near-eye displays [Invited

Liquid-crystal-based Pancharatnam–Berry phase optical elements (PBOEs), also known as diffractive wave plates (DWPs), geometric phase optics (GPO), or geometric phase holograms (GPHs), are functional planar structures with patterned orientation of anisotropy axis. Several scientifically interesting yet practically useful electro-optical effects, such as focusing, beam splitting, waveguide coupling, and wavelength filtering, have been realized with PBOEs. Because of the high degree of optical tunability, polarization selectivity, nearly 100% diffraction efficiency, and simple fabrication process, PBOEs have found widespread applications in emerging display systems, particularly virtual/augmented/mixed reality displays and head-up displays. In this review, we will describe the basic operation principles, present device fabrication procedures, discuss numerical modeling methods, and address applications of PBOEs in emerging display systems.

Nano-fabrication and characterization of silicon meta-surfaces provided with Pancharatnam-Berry effect

In this paper, the implementation of optical elements in the form of Pancharatnam-Berry optics is considered. With respect to 3D bulk and diffractive optics, acting on the dynamic phase of light, Pancharatnam-Berry optical elements transfer a phase that is geometric in nature by locally manipulating the polarization state of the incident beam. They can be realized as space-variant sub-wavelengths gratings that behave like inhomogeneous form-birefringent materials. We present a comprehensive work of simulation, realization, and optical characterization at the telecom wavelength of 1310 nm of the constitutive linear grating cell, whose fabrication has been finely tuned to get a π-phase delay and obtain a maximum in the diffraction efficiency. The optical design in the infrared region allows the use of silicon as candidate material due to its transparency. In order to demonstrate the possibility of assembling the single grating cells for generating more complex phase patterns, the implementation of two Pancharatnam-Berry optical elements is considered: a blazed grating and an optical vortices demultiplexer.

Experimental realization to efficiently sort vector beams by polarization topological charge via Pancharatnam–Berry phase modulation

This paper reports the experimental realization of efficiently sorting vector beams by polarization topological charge (PTC). The PTC of a vector beam can be defined as the repetition number of polarization state change along the azimuthal axis, while its sign stands for the rotating direction of the polarization. Here, a couple of liquid crystal Pancharatnam–Berry optical elements (PBOEs) have been used to introduce conjugated spatial phase modulations for two orthogonal circular polarization states. Applying these PBOEs in a 4-f optical system, our experiments show the setup can work for PTC sorting with a separation efficiency of more than 58%. This work provides an effective way to decode information from different PTCs, which may be interesting in many fields, especially in optical communication.