Waveguide Holograms Research Articles

Distortions of the virtual image in augmented reality displays based on waveguide holograms: the arising of tangential distortion and magnification chromatism

Distortions of the virtual image in augmented reality displays based on waveguide holograms: the arising of tangential distortion and magnification chromatism

Method for measuring periods of waveguide diffractive optical elements

An original method of the periods of waveguide diffractive optical elements (DOEs) measuring is proposed. In contrast to standard techniques, the proposed method provides measurements of waveguide gratings periods while the diffracted light is propagating in the substrate material. The method is simple and has a small error Keywords: waveguide holograms, diffractive optical elements.

Design of a waveguide eye-tracking system operating in near-infrared with holographic optical elements

Recent research in augmented reality (AR) eyewear has prompted interest in using volume holographic optical elements for this application. However, many sensing operations in AR systems require the use of wavelengths in the near-infrared (NIR) (750 to 900 nm). These wavelengths typically exceed the sensitivity range of available commercial holographic recording materials (450 to 650 nm), which complicates the design of optical elements with power since significant aberrations result when the reconstruction wavelength differs from the construction wavelength. Several methodologies for designing a waveguide hologram imaging system in NIR are reviewed and evaluated. The design approach presented in our work integrates the most effective practices such as fabrication point source location optimization and aberration analysis to realize effective holographic waveguide couplers formed with visible wavelength light and reconstructed in the NIR. The technique is demonstrated by designing and fabricating an input waveguide hologram in conjunction with a multiplexed output coupling hologram. The resulting input/output waveguide holograms can achieve an image resolution of (∼3 lp / mm) with a 0.6-mm-thick glass substrate that has a refractive index of 1.8.

Holographic Waveguide Periscopes in Augmented Reality Displays

Main properties of holographic waveguide periscopic multiplexors of the exit pupil of optical systems of augmented reality displays are considered. Limitations in the operation of waveguide holograms, compensation of chromatic aberrations in periscopic schemes, and influence of waveguide defects on the operation of augmented reality displays constructed based on waveguide holograms are analyzed.

Polarization-selective waveguide holography in the visible spectrum.

We propose and experimentally demonstrate a polarization-selective waveguide hologram at optical wavelengths, based on an all-dielectric metamaterial multilayer system. We show that two spatially separated or overlapped holographic images can be produced with two orthogonally polarized beams, incorporated into a binary computer generated hologram (CGH). These two images can be combined into a single 3D stereoscopic image observable using linearly or circularly polarized glasses. The two polarized beams can also be utilized to construct radially and azimuthally polarized "vortex" beams. The fundamental and first higher-order TM and TE modes of an optical waveguide are used to guide the two polarization states with distinct propagation constants. The two guided waves act as spatially distinct reference waves such that the integrated, on-chip hologram can distinguish the two and provide two independent images corresponding to the two polarizations. Polarization selective waveguide holograms can be used in a diverse set of applications, from chip-scale displays and augmented reality (AR) to optical trapping.

All-optical tunable power splitter based on a surface plasmonic two-mode interference waveguide.

In this paper, we have introduced a surface plasmonic two-mode interference (SPTMI) coupler having a silicon core, GaAsInP side cladding, and silver top and bottom cladding as an optical power splitter. A wide range of tunability from the 50∶50 splitting ratio to 1∶99 is achieved by refractive index modulation of the GaAsInP cladding with application of varying optical pulse power. The coupling length of the SPTMI-based splitter is ∼11.5 times less than that of a previously reported optical power splitter based on multimode waveguide holograms. The proposed optical power splitter has potential in development of large-scale integrated circuits due to its compactness and high fabrication tolerance.

Experimental method for testing diffraction properties of reflection waveguide holograms.

Waveguide holograms' diffraction properties include peak wavelength and diffraction efficiency, which play an important role in determining their display performance. Based on the record and reconstruction theory of reflection waveguide holograms, a novel experimental method for testing diffraction properties is introduced and analyzed in this paper, which uses a plano-convex lens optically contacted to the surface of the substrate plate of the waveguide hologram, so that the diffracted light beam can be easily detected. Then an experiment is implemented. The designed reconstruction wavelength of the test sample is 530nm, and its diffraction efficiency is 100%. The experimental results are a peak wavelength of 527.7nm and a diffraction efficiency of 94.1%. It is shown that the tested value corresponds well with the designed value.

Paper No P4: The Development of the Integrated Holographic Recording Head for Synthesized 3D Hologram Recording

AbstractAn integration of several total internal reflection (TIR) holographic optical elements (HOEs) for the design of compact holographic recording system is discussed. Methods of waveguide holography (WGH) permits to realize the concept of pure HOE recording setup for synthesizing three‐dimensional (3D) holograms. So the idea of homogeneous technology for “HOLOGRAMS BREEDING” was approved. The several schemes for light guiding HOE recording was proposed to obtain integrated TIR illumination and reference beam forming units. In this paper, it is shown that the specific light transformation waveguide holograms permit to construct efficient recording setup for 3D synthesized micro‐hogel recording. It is also shown several experimental schemes of reflection/transmition variants of 3D synthesized hologram recording. The schemes of HOE operation improvement are discussed and some experimental results are shown.

Mobile glasses-free 3D using compact waveguide hologram

The exploding mobile communication devices make 3D data available anywhere anytime. However, to record and reconstruct 3D, the huge number of optical components is often required, which makes overall device size bulky and image quality degraded due to the error-prone tuning. In addition, if additional glass is required, then user experience of 3D is exhausting and unpleasant. Holography is the ultimate 3D that users experience natural 3D in every direction. For mobile glasses-free 3D experience, it is critical to make holography device that can be as compact and integrated as possible. For reliable and economical mass production, integrated optics is needed as integrated circuits in semiconductor industry. Thus, we propose mobile glasses-free 3D using compact waveguide hologram in terms of overall device sizes, quantity of elements and combined functionality of each element. The main advantages of proposed solution are as follows: First, this solution utilizes various integral optical elements, where each of them is a united not adjustable optical element, replacing separate and adjustable optical elements with various forms and configurations. Second, geometrical form of integral elements provides small sizes of whole device. Third, geometrical form of integral elements allows creating flat device. And finally, absence of adjustable elements provide rigidly of whole device. The usage of integrated optical means based on waveguide holographic elements allows creating a new type of compact and high functional devices for mobile glasses-free 3D applications such as mobile medical 3D data visualization.

Achromatic reconstruction of femtosecond holograms in the planar optical waveguide

Holograms were recorded by 30 fs laser pulses in 20 microm film of dichromated gelatin on the polished quartz substrate and reconstructed in the waveguide mode. The geometric-optical regime of waveguide hologram reconstruction was obtained: the direction of the reconstructed beam was observed to be independent on the reconstructing wavelength within the hologram spectral selectivity band. We discuss the possibility of producing achromatic waveguide optical elements containing only a few periods.

Variable splitting ratio 2 × 2 MMI couplers using multimode waveguide holograms

Variable power splitting ratio 2x2 MMI couplers using multimode waveguide holograms are analyzed. Theoretical analysis shows that variable splitting ratios can be obtained with surface relief holograms on MMI couplers with fixed dimensions. Devices with paired-imaging lengths are designed on a silicon-on-insulator (SOI) platform. Beam propagation simulations are used to verify a matrix theory analysis and to investigate proposed device performance. Fabrication tolerance of the proposed device is also analyzed.

Implementation of discrete unitary transformations by multimode waveguide holograms

Integration of holograms into multimode waveguides allows the implementation of arbitrary unitary mode transformations and unitary matrix-vector multiplication. Theoretical analysis is used to justify a design approach to implement specific functions in these devices. Based on this approach, a compact mode-order converter, a Hadamard transformer, and a spatial pattern generator-correlator are proposed and analyzed. Beam propagation simulations are used to verify the theoretical calculations and to address bandwidth, scalability, and fabrication criteria. Optical pattern generators were successfully fabricated using standard photolithographic techniques to demonstrate the feasibility of the devices.

True-time-delay modules based on a single tunable laser in conjunction with a waveguide hologram for phased array antenna application

A wavelength-controlled continuous beam-steering four-element X-band (8- to 12-GHz) phased array antenna system is presented. The system is based on the continuously tunable optical true-time-delay technique. Dispersion-enhanced waveguide holograms were proposed and used to fabricate the optical true-time-delay devices. The devices are characterized both theoretically and experimentally. The wavelength of a laser was tuned within the system to get continuously tunable true time delay. The time delay was measured for a wavelength tuning range from 1537 to 1547 nm in 10-nm steps. The far-field radiation patterns of the antenna system were measured at 9 and 10.3 GHz, and they showed no beam squint. The true-time-delay formation idea presented here is suitable for not only X-band, but also for higher microwave frequencies, such as K-band.

Orthogonal aperture multiplexing for multilayered waveguide holographic read-only memories.

A multilayered waveguide holographic read-only memory is a promising candidate for the next generation of optical data storage systems. We improved the data density of the memory by using a multiplexing method with a set of orthogonal optical masks. We multiplexed as many as nine images into one waveguide hologram, and all the observed images had negligible cross talk. This made it possible to achieve a ninefold increase in data density. We provide experimental results for both metallic and liquid-crystal masks.

Continuously delay-time tunable-waveguide hologram module for X-band phased-array antenna

Tunable optical true time-delay modules based on a dispersive waveguide hologram are presented to provide continuous radio-frequency beam scanning for an X-band (8-12 GHz) phased-array antenna system. The true time-delay modules operating in the 1550-nm region were fabricated with continuously tunable time delays from 5 to 64 ps. The far-field radiation patterns were measured with different delay combinations and the continuity of the scanning angles from 35/spl deg/ to 55/spl deg/ was experimentally confirmed at X-band frequencies.

Holography with surface-plasmon-coupled waveguide modes

We report on an attempt to use the enhancement effect of surface-plasmon resonance to improve the image quality of a waveguide hologram. With a structure consisting of a waveguide medium sandwiched between a metal film and a hologram, we obtained holographic images reconstructed by surface-plasmon-coupled waveguide modes. Comparison of the holographic images reconstructed by TM and TE modes indicates that the surface-plasmon effect is responsible for better image quality in diffraction efficiency and image contrast.

Incoupling waveguide holograms for simultaneous focusing into multiple arbitrary positions

A design method is presented that enables the realization of a novel type of incoupling waveguide hologram (IWGH) that simultaneously focuses the incoupled light to any desired positions in the waveguide. IWGH's, or grating couplers, are gratinglike structures etched into the waveguide surface. They couple the light incident from free space into the waveguide. The grating lines can be dislocated with respect to each other to provide phase modulation of the incoupled light. By use of this phase modulation, novel beam splitting and focusing functions can be built into the IWGH's. The new design algorithm is based on a model that assumes a simple relation between the incident light wave and the locally excited guided wave. This model is used to obtain an efficient formulation of the optimization problem. Four different IWGH's were designed and fabricated in InP for light at 1550-nm wavelength. Experiments confirm that these IWGH's are capable of incoupling the incident wave and simultaneously splitting and focusing the guided wave into multiple positions in the waveguide at different distances from the IWGH.

Waveguide grating coupler with a tailored spectral response based on a computer-generated waveguide hologram

We propose a novel method that, for the first time to our knowledge, makes it possible to tailor the spectral response of an input grating coupler. This method is based on the idea of computer-generated waveguide holography. Grating couplers with different spectral responses have been designed and fabricated, and experimental results are presented that demonstrate the effectiveness of the proposed method.

Path-reversed substrate- guided-wave optical interconnects for wavelength-division demultiplexing

A path-reversed substrate-guided-wave holographic interconnection scheme is investigated for a wavelength-division demultiplexing application. Using a beveled edge of a waveguiding plate allows optical signals to be coupled into the waveguiding plate and then to be coupled out of the plate by a waveguide hologram. Theoretical analyses are given for dispersion, bandwidth, and recording parameters of various guided-wave holographic gratings. A device is fabricated with a 45 degrees incident angle and a 45 degrees diffraction angle by use of a 20-microm photopolymer film. The 3-dB bandwidth of the device is measured to be 20 nm. Four-channel wavelength demultiplexing is demonstrated at 796, 798, 800, and 802 nm with no cross talk observed. A one-to-five cascaded four-channel wavelength-division demultiplexer with +/-5% energy uniformity under s polarization is also demonstrated to increase the user-sharing capacity. Twenty fan-out channels (5 x 4) are achieved experimentally.

Waveguide-hologram-based wavelength-multiplexed pseudoanalog true-time-delay module for wideband phased-array antennas

A pseudoanalog true-time-delay (TTD) module based on substrate-guided waves and wavelength-division multiplexing is presented. A 1-to-32 (5-bit) even fan-out is demonstrated by use of a two-dimensional waveguide hologram array. This module has a packing density of 2.5 lines/cm(2) and very compact packaging (8 cm x 4 cm x 8 mm). It also reduces TTD system complexity by providing continuously tuned delay signals to parallel-control the whole phased-array antenna system. The device has a measured bandwidth of as high as 2.4 THz. The delay signal can range from tens of picoseconds to several nanoseconds.