General analytic solution for far-field phase and amplitude control, with a phase-only spatial light modulator

Absolutely interferometric calibration of phase liquid crystal spatial light modulators using honeycomb gratings composited with Billet-split Fresnel zone plates

The traditional interferometric calibration of phase spatial light modulators (SLM) based on interference fringes shift is easily disturbed due to environmental vibration. Here a kind of absolutely interferometric calibration of phase SLM is investigated to eliminate the disturbance using dual honeycomb gratings composited with Billet-split Fresnel zone plates (BsFZP), in which honeycomb gratings split an incident beam into three beams and the first two beams are interfered by BsFZP while the last beam is chosen as the absolute reference point. The experiments on both 532 and 632.8 nm incident wavelengths were separately carried out, and the measuring accuracy was proved by a SID4 wavefront sensor. The proposed high-accuracy calibration provided the basis for SLM application scenarios with high precision.

Automotive Holographic Head-Up Displays

Driver's access to information about navigation and vehicle data through in-car displays and personal devices distract the driver from safe vehicle management. The discrepancy between road safety and infotainment must be addressed to develop safely operated modern vehicles. Head-up displays (HUDs) aim to introduce a seamless uptake of visual information for the driver while securely operating a vehicle. HUDs projected on the windshield provide the driver with visual navigation and vehicle data within the comfort of the driver's personal eye box through a customizable extended display space. Windshield HUDs do not require the driver to shift the gaze away from the road to attain road information. This article presents a review of technological advances and future perspectives in holographic HUDs by analyzing the optoelectronics devices and the user experience of the driver. The review elucidates holographic displays and full augmented reality in 3D with depth perception when projecting the visual information on the road within the driver's gaze. Design factors, functionality, and the integration of personalized machine learning technologies into holographic HUDs are discussed. Application examples of the display technologies regarding road safety and security are presented. An outlook is provided to reflect on display trends and autonomous driving.

Simultaneous shaping of amplitude and phase of light in the entire output plane with a phase-only hologram

An iterative beam shaping algorithm is proposed to simultaneously shape the amplitude and phase of an optical beam. The proposed algorithm consists of one input plane and two completely overlapped output planes which refer to the output plane in real space. The two output planes are imposed with both amplitude and phase constraints, and the constrained areas in the two output planes are complementary. As a result, both the amplitude and phase in the entire output plane are controllable and arbitrary target complex amplitudes can be achieved with the proposed algorithm. The computing result of the proposed algorithm is a phase-only distribution which can be conveniently realized with a spatial light modulator or a fabricated diffractive optical element. Both simulations and experiments have verified the high performance of the proposed algorithm.

Complete shaping of optical vector beams

We propose and experimentally demonstrate the complete and simultaneous modulation of the amplitude, phase and arbitrary state of polarization of optical beams. Based on a 4-f system including a spatial light modulator (SLM), two orthogonally polarized beams serving as the base vector components are produced by a computer generated hologram. The complex amplitude of orthogonal components is realized by a macro-pixel encoding technique purposely designed for phase-only SLMs. Vector beams can be created from the coaxial superposition of the two base beams. This enables us to design optical fields with arbitrarily structured amplitude, phase and polarization by using only one SLM, and thus provides an easy-to-implement route for exploring the novel effects and expanding the functionality of vector beams with space-variant parameters.

Beam shaping of complex amplitude with separate constraints on the output beam

We present a beam shaping technique in controlling the complex amplitude of an optical beam. The constraint on the amplitude of the output beam in the Gerchberg-Saxton algorithm is replaced with constraints both on the amplitude and phase of the output beam in the proposed method. The total areas of the constrained regions and free regions on the complex amplitude of the output beam in the proposed method are maintained. An output beam with arbitrary complex amplitude can be realized with the proposed method. The computing result from the proposed method is a phase-only distribution, which can be fabricated as diffractive optical element for higher diffraction efficiency. Both simulations and experiments are present and the effectiveness of the proposed method is verified.

Dynamic placement of plasmonic hotspots for super-resolution surface-enhanced Raman scattering

In this paper, we demonstrate dynamic placement of locally enhanced plasmonic fields using holographic laser illumination of a silver nanohole array. To visualize these focused "hotspots", the silver surface was coated with various biological samples for surface-enhanced Raman spectroscopy (SERS) imaging. Due to the large field enhancements, blinking behavior of the SERS hotspots was observed and processed using a stochastic optical reconstruction microscopy algorithm enabling super-resolution localization of the hotspots to within 10 nm. These hotspots were then shifted across the surface in subwavelength (<100 nm for a wavelength of 660 nm) steps using holographic illumination from a spatial light modulator. This created a dynamic imaging and sensing surface, whereas static illumination would only have produced stationary hotspots. Using this technique, we also show that such subwavelength shifting and localization of plasmonic hotspots has potential for imaging applications. Interestingly, illuminating the surface with randomly shifting SERS hotspots was sufficient to completely fill in a wide field of view for super-resolution chemical imaging.