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We propose a field of view (FOV) enlargement method using the line symmetric image input in the single layer volumetric holographic waveguide. We build a mathematical model and analyze the virtual image to be seen by the observer considering the interaction volume of the signal light ray within the volumetric hologram waveguide. It is found that the diffracted light intensity is varied with each ray angle due to the variation of the interaction volume, which results in a critical issue of poor uniformity of luminance on the virtual image in the volumetric hologram waveguide. Our proposed method compensates for the variation in the interaction volume by another ray coming from the line symmetric point within the input image. The proposed method achieves a 490-times improvement in uniformity of luminance over the FOV 60 (H) × 60 (V) degrees, which is twice the FOV compared with conventional waveguide.

In mode-division multiplexing systems, the transmission quality is restricted by the differential mode delay (DMD). We previously proposed a spatial mode exchange technique using volume holograms (VHET) to reduce the DMD. VHET can be used for the exchange of multiple spatial modes with different transmission speeds using a single device. However, in VHET, incidents of cross-talk (XT) caused by non-target holograms severely degrade the exchange performance. To address this issue, we propose a spatial mode exchange technique that uses volume holograms in combination with a random optical diffuser. By scattering the intensity distribution of the signal beam uniformly using a random optical diffuser, high exchange performance can be attained due to the reduction in the influence of non-targeted holograms. We confirmed the basic operation of the proposed scheme by considering the crosstalk component coupled to the few-mode fiber in a mode-division multiplexing system. The simulation results show that the maximum XTs are significantly suppressed to − 15.8 dB.

In this study, we reveal a novel aerial display system, to the best of our knowledge, that combines volume hologram mirrors with a dihedral corner reflector array (DCRA). The suggested aerial display has a see-through capability, which allows for a new design of aerial displays by combining with other types of displays. Furthermore, the virtual image, which frequently disrupts the observation of aerial images, can be suppressed by the Bragg condition of the volume hologram. The color dispersion in the holograms is efficiently compensated by employing features of the DCRA. The findings of preliminary experiments are demonstrated using a DCRA device and full-color hologram mirrors.

We propose a volume holographic optical element (VHOE) used as an objective turret in a lensless digital holographic microscope. It also served as a reference wave guide to reduce the volume of the system. For further optimization of resolution performance, it used a spherical wave in the object light of the VHOE, which served as the reference light of the microscope. Another sheared spherical wave was used to illuminate the sample. The optimized VHOE increased the spatial resolution of the record signal effectively. Furthermore, the change of spherical wave distance leads to the change of imaging magnification.

Advancements in 3D printing, specifically by 2-photon polymerization, enabled the fabrication of high resolution novel optical elements for various applications by engineering the topography of the structures. Recently, the ability to obtain a varying refractive index distribution by 2-photon polymerization also started to gain momentum to design and produce gradient-index (GRIN) micro-optics. Here, we demonstrate micro-scale volume holograms by 2-photon polymerization by tuning the exposure point by point in the 3D volume to obtain the necessary refractive index distribution. 3D printed micro-scale GRIN volume holograms lay an opportunity to open a complimentary dimension in various systems thanks to in-situ fabrication advantage, which can provide complex interconnections and beam shaping in micro-scale.

A new implementation of the weight vector in a classifier based on an optical system using a volume holographic filter with a vector decomposition algorithm is proposed for high-speed data classification. Using a volume holographic filter, the correlation between the input and the decomposed weight vector is calculated for the classification score, which is the output from the decision function in the optical classifier. The authors experimentally demonstrate the core concept and confirm the effectiveness of the proposed method by executing a two-class classification problem using a volume hologram medium.

The planar diffractive waveguide is widely adopted in optical see-through head-mounted displays in the field of augmented reality due to its distinguished trade-off among the form factor, optical character, and mass production process. The diffractive waveguides can be divided into surface relief grating waveguides and volume hologram grating waveguides. In this review, the state of the art of planar diffractive waveguides is described, including the physical principle, optical configuration, performance parameters, and manufacturing process. Typical commercial augmented reality head-mounted displays are also presented with a discussion on the advantages as well as disadvantages of surface relief grating and volume hologram grating waveguides. Finally, the bottleneck of planar diffractive waveguides and the future development trends are discussed.

We present a new type of filter that improves the SNR of systems where polychromatic signal and noise are located at different distances within the same line of sight. The filter is based on holographic technology that allows for the discrimination of wavefronts by range. In using a combination of two holographic elements, a pre-disperser and a thick volume hologram, we were able to significantly increase the spectral bandwidth of the filter, from 9nm without the pre-disperser to 70nm with both holographic elements. Laboratory proof of concept demonstrated that such a filter is capable of an SNR improvement of 15 dB for a monochromatic source, and up to 7.6 dB for a polychromatic source. This filter can find applications in astronomic observation, satellite or space debris tracking, and free-space optical communication.

The resolution of images is increasing year by year. High-definition images have a large amount of data so that high calculation cost is required for image processing. For example, when original data is restored from non-clear high-definition two dimensional coded images, it is necessary to improve the image quality. A volume holographic optical element works as a multiple lens for each pixel in an image so that spreading pixel patterns can be individually focused. Then, each pixel becomes clear and original data can be easily restored. However, it is difficult to analytically express the function of volume holographic optical elements. In our previous study, reconstructed images from a volume hologram, in which some data pages were recorded in multiple, were expressed by analytic function. The analytic function was called pixel amplitude function. In this study, the pixel amplitude function is used for an input image to a volume holographic optical element. Then, output image is analytically expressed.

In this study, we prepared a cylindrical wave diffractive optical element that diffracts color images using volume hologram technology to improve the performance and cost of HMDs.

A wavelength multiplexing procedure for color transmission volume holograms of diffusing objects recorded in Bayfol® HX200 photopolymer is proposed. For the recording, three lasers of 442 nm, 532 nm and 633 nm, and a Spectralon® diffusing object were used for monochromatic and polychromatic calibration. Monochromatic calibration shows that the maximum index modulation obtained for each wavelength was not enough to give 100% efficiency, although the efficiency values achieved in the case of monochromatic recordings with diffusing objects were high, at around 90% for 633 nm and 532 nm recordings, and 60% for 442 nm. The efficiency values obtained for multiplexed holograms were 19.1% for the 442 nm hologram, 25.9% for the 532 nm hologram and 15.2% for the 633 nm. This research was funded by the “Diputación General de Aragón-Fondo Social Europeo” (TOL research group, E44_17R), the “Generalitat de Catalunya” (2017FI_B2_00127 and 2017 SGR 1276) and the “Ministerio de Ciencia e Innovación” (PID2019-108598GB-I00, PID2019-111536RB-I00 and PID2021-114311RA-I00)

An optimized wavelength multiplexing procedure for color reflection holograms of diffusing objects recorded in Bayfol® HX photopolymer is proposed. It is based on simultaneous initial illumination of all the wavelengths and sequential shuttering down of the laser beams involved. Three lasers of 442 nm, 532 nm and 633 nm were selected, as a tradeoff solution between setup complexity and color reproduction accuracy. The obtained results prove that the presented method improves the simultaneous and sequential exposure methods by increasing the mean efficiency and reducing the standard deviation (increasing uniformity) of the involved wavelengths. For a Spectralon® diffusing object, the assessed method reports a mean efficiency of 25.0% with a standard deviation of 2.9%, while simultaneous and sequential iterative exposures result in mean efficiencies of 12.1% and 20.6% with standard deviations of 3.4% and 5.4%, respectively. The authors would like to thank Covestro Deutschland AG for supplying the recording photopolymer material. This research has been supported by the “Diputación General de Aragón-Fondo Social Europeo” (TOL research group, E44_17R), the “Generalitat de Catalunya” (2017FI_B2_00127 and 2017 SGR 1276) and the "Ministerio de Ciencia e Innovación" (PID2019-108598GB-I00). Daniel Chemisana thanks ICREA for the ICREA Academia award.

Radial polarization converters can convert an incident light into a radially polarized light, which is beneficial in a variety of applications. In this paper, a new design of holographic radial polarization converter is proposed which consists of eight space-variant polarization-selective volume hologram gratings. According to the coupled wave theory, a feasible design of the polarization-selective volume hologram gratings was described. The prism-hologram-prism sandwiched recording method was adopted for the recording. The s- and p-polarization diffraction efficiencies of the fabricated polarization-selective volume hologram gratings at 443.29 nm are 90.83% and 22.09%, respectively. The operation bandwidth is about 4.42 nm. A prototype of holographic radial polarization converter was successfully assembled and tested. Due to the introduction of volume hologram gratings, this design should have the advantages of high diffraction efficiency, narrow band, compactness, and planar configuration, meaning it is especially suitable for low-cost mass production and has high application potential in related fields.

An approach for recording complex holograms using two beam interference setup incorporating a light modulating device in one of the arms of the holographic setup is proposed. This allows the intensity profile of the beam reflected by the DMD to be adjusted to a pre-determined profile. Using an UV laser, the created interference pattern is recorded into PTR glass plate. The variable light amplitude exposure of the glass is converted to a refractive index change after thermal treatment step. The DMD device makes possible the incorporation of zones in the hologram where there is no interference pattern and therefore there is no hologram. Such custom designed holograms can find applications in laser resonators or as spatially sensitive wavelength filters. In addition, the holograms recorded in the volume of the PTR glass are practically insusceptible to surface damage, changes in the environment and other factors from which holograms recorded in polymers suffer.

A see-through light-field 3D display that works in head-up configuration is being presented. The display system consists of only a commercial projector and a holographic screen and works on the principle of Integral Imaging. The holographic screen is a volume hologram that is digitally fabricated, which functions as a micro concave- mirror array. The screen also has other optical functions embedded that helps to eliminate the bulk of optical components needed otherwise. This significantly simplifies the system, there by taking it closer to the consumer market. A color 3D scene of size 20cm x 10cm x 5cm (depth) has been successfully reproduced and can be seen through naked eye for a viewing angle of 10-degrees.

In this research, we propose a mode selective switch (MSS) using volume holograms. MSS is a device that distributes the mode-division multiplexed (MDM) signal to different output ports for each spatial mode component contained in the signal. Using MSS, the function of reconfigurable optical add / drop multiplexer (ROADM) can be implemented, which can manipulate arbitrary spatial mode signal at any position in the next generation MDM network. In our proposed MSS, the incident signal is separated into spatial mode components by the volume hologram on the input side. The signal destination will be selected for each mode by diffracting independently. The spatial mode components are separated in direction of the plurality of volume holograms on the output side using a spatial light modulator (SLM). In the volume hologram on the output side, the multiple spatial mode components are recombined and emitted once again as an MDM signal. This method has the advantageous that one volume hologram can multiplex or de-multiplex multiple modes, allowing it to cope easily with the increase in the number of modes and ports to be multiplexed. In the experiment, the optical signal lights of three-mode are separated for each spatial mode by the volume hologram on the input side, and the switching to either of the two ports on the output side is successfully performed for each mode using the SLM.

In mode-division multiplexing (MDM) systems, transmission quality is restricted by differential mode delay (DMD). We have proposed and developed a spatial-mode exchange technique using volume holograms (VHET) as a leading technology to reduce DMD. VHET can equilibrate the transmission time of each spatial mode which has different transmission speeds in a few mode fiber using a volume hologram. This technology enables low signal distortion and high spectral efficiency, which are indispensable to the long-haul transmission for the MDM system. However, in this technology, modal cross-talks (MXTs), which are caused by inter-page cross-talks in the volume hologram, seriously degrade the performance of VHET. In this study, we proposed a method of combining a volume hologram and a random optical diffuser to reduce the MXTs. In our method, the intensity distribution of the input spatial mode is diffused uniformly by a random optical diffuser. The high exchange performance will be attained because the non-targeted holograms included in the multiplexed holograms do not affect most of the spatial mode. Moreover, our method can be applied to the communication wavelength bands using the dual wavelength method. We confirmed the basic operation of the proposed scheme using a linearly polarized mode group comprising LP0,1, LP1,1, and LP2,1. Compared with the conventional VHET, the simulation results show that the maximum MXTs are significantly suppressed from 0.4 to -15.8 dB.

Efficiency of optical frequency conversion in quadratic media critically depends on spatial modulation of the nonlinear optical response of the materials. This modulation ensures, via the quasi phase matching (QPM), an efficient energy exchange between optical waves at different frequencies. The QPM structures, also known as the nonlinear photonic crystals, offer a variety of novel properties and functionalities that cannot be obtained in uniform nonlinear crystals. In particular the 3-dimensional modulation of nonlinearity allows one to realize the so-called nonlinear volume holograms which extends the concept of volume holography to nonlinear optics. Nonlinear volume hologram represents the 3- dimensional distribution of the nonlinear polarization which arises from interaction between input fundamental beam and generated wave with complex wave front, in medium exhibiting quadratic nonlinearity (χ(2)). When illuminated by fundamental beam, the nonlinear hologram gives rise to a wave at different frequency (e.g. second harmonic of fundamental wave) having complex intensity distribution following the transverse structure of the hologram itself. In this way one can combine generation of waves at new frequencies with simultaneous shaping of their transverse and longitudinal intensity profiles. In this work we present formation of various types of nonlinear volume holograms in ferroelectric crystals by using unique all-optical domain inversion technique and demonstrate their application in optical wave-shaping.

We report on the null reconstruction effect (NRE) of an elliptical polarization volume hologram with orthogonal elliptically, circularly, and linearly polarized waves, respectively. The NRE is a special phenomenon in polarization holography, which means the diffraction efficiency declines to zero when the hologram is reconstructed by an orthogonally polarized reading wave. In our previous work [Opt. Express24, 1641 (2016)OPEXFF1094-408710.1364/OE.24.001641; Opt. Lett.42, 1377 (2017)OPLEDP0146-959210.1364/OL.42.001377; Opt. Express23, 8880 (2015)OPEXFF1094-408710.1364/OE.23.008880], the NRE of polarization holography recorded by linear and circular polarization waves has been investigated. Compared with linear and circular polarization holography, elliptical polarization holography represents a more general and unified recording hologram. However, no work on the NRE of elliptical polarization holography, as far as we know, has been reported until now. In this paper, the NRE of elliptical polarization holography is investigated and demonstrated theoretically and experimentally. First, the conditions of achieving NRE in elliptical polarization holography are studied based on vector holography theory. The results indicate that the NRE is a common phenomenon in polarization holography written by linear, circular, and elliptical polarization waves. Then, a series of experiments of NRE in a polarization hologram written by orthogonal elliptically, circularly, and linearly polarized waves is carried out. The NRE of elliptical polarization holography is experimentally observed, and the results are in nice agreement with the theoretical analysis. The NRE of elliptical polarization holography is expected to be applied in high-density optical data storage and polarization-controlled holographic elements.

In this paper, a comprehensive ray-tracing model for simulating volume holographic gratings is programmed and demonstrated in OpticStudio. The model integrates physical properties of the hologram, such as diffraction direction and efficiency based on incident rays’ direction and polarization state, into the standard ray-tracing model. The model also accounts for hologram emulsion shrinkage and refractive index shift. With integration of these physical effects, advanced modeling tools like image simulation and optimization become available and are demonstrated with a case study of a seethrough head-mounted display.

The values of the amplitudes of the refractive index and absorption coefficient modulations in volume hologram gratings, which were recorded in a polymer material with phenanthrenequinone (PQ), have been determined by the results of the approximation of the angular selectivity contours, which were measured at wavelengths of 450, 473, 532, and 633 nm before and after the development of holograms, resulting from the diffusion of PQ molecules in a glassy polymer. Immediately after recording, before the diffusion development, the holograms are mixed amplitude-phase in the PQ absorption spectral region and phase for the red light, which is not absorbed by it (633 nm), and become purely phase during the development regardless of the wavelength. The shape of the selectivity contour of the undeveloped hologram indicates the counterphase between the modulations of the absorption coefficient and refractive index, illustrating the concept of complementary gratings, on which the principle of hologram formation in the material under consideration is based.

A method for development of gratings for effective excitation of surface plasmonic waves using holography principles has been proposed and theoretically analyzed. For the case of a plasmonic wave in a dielectric layer on metal, the proposed volume hologram is 1.7 times more effective than the simple grating of slits in the dielectric layer with the optimized period and slits’ width. The advantage of the hologram over the optimized grating is in the refractive index distribution that accounts phase relationships between an exciting and an excited waves more correctly. The proposed holographic method is universal. As expected, this can be extended for effective excitation of different types of optical surface waves and modes of optical waveguides.

We propose a projection-type see-through near-to-eye display by combining two holographic optical elements (HOEs), a holographic lens with the on-axis projection configuration and a holographic diffuser. The proposed method provides an enlarged eye-box by virtue of diffusing properties of an HOE diffuser (HOED) without any temporal multiplexing methods. In this paper, a thorough analysis on imaging characteristics of an HOE lens (HOEL) according to the projection configuration is provided, so that we optimize the recording geometry of the HOEL with the passively enlarged eye-box. The theoretical analysis is validated by simulation results using a volume hologram model in OpticStudio. As experimental verifications, we realize a prototype of the proposed method using the photopolymer-based HOEs in a single color. The fabricated HOEL and HOED show high transmittance of 84.9% and 62.2%, respectively. By using the fabricated HOED with a diffusing angle over 20 ° and an angular selectivity of 8.7 °, the prototype successfully provides see-through images with the eye-box larger than 5 mm in width.

To optimize the performance of visible light communication (VLC) systems it is important that a VLC receiver has both a carefully designed field of view (FOV) which excludes light from unwanted directions and optical filtering to block unwanted wavelengths. The new dual-aperture hologram receiver consists of two parallel opaque layers each with a transparent aperture and a volume hologram placed below the second aperture. The dual apertures ensure that only light from specific directions reaches the hologram. The hologram provides wavelength selectivity and additional directivity. Analytical and simulation results show how the FOV of the new dual aperture hologram receiver depends on the dimensions of the aperture structure, and the position and size of the receiver photodiode, and how the optical bandwidth depends on the design of the hologram. Proof of concept experiments confirm the performance of the receiver. Major advantages of the new receiver are its compact structure suitable for incorporation in smartphones and its ease of manufacture.

Protective elements formed in a 3D hologram recorded in a polymer nanocomposite, such as a lens hologram, a cryptographic information lens hologram, a hologram with a hidden cryptographic image invisible to the naked eye, and a transmissive element based on the volume hologram of the flat body, are studied. Holograms are recorded on a nanocomposite material that is a photopolymerization monomer composite containing various photosensitizers and nanoparticles.

Beating of a broad laser reference beam with a quite general focused object beam inside a plasma volume generates a dynamic plasma hologram. Both beams may be of moderate intensity. The volume hologram can be read out by an ultraintense main beam (of similar structure as the reference beam) producing an object beam replica. For the latter, intensity in the focus may become extremely large. As an application, the possibility of a read-out focused Gaussian laser pulse with intensity of several 10^{19}W/cm^{2} in focus is shown by three-dimensional numerical simulations. Besides the focusing possibility, the hologram may also act as a mode converter for high-intensity laser pulses. Generating a plasma hologram with a focused Laguerre-Gaussian object beam results in a staggered plasma density grating, allowing the production of high-intensity vortex beam replica.

The article describes the features of the security elements used in color three-dimensional security holograms. Unlike classical security holograms - "rainbow" relief - phase holograms, color three-dimensional security holograms have spectral and angular selectivity. This feature allows them to create new security elements or use the properties of already known elements as a new. The article describes the schemes and devices for creating such security elements, as well as devices for their visualization and control. Examples of typical security elements used in color three-dimensional security holograms are presented. This work was supported by the Russian Science Foundation (Project No. 18-79-00304).

The manipulation of a laser’s transverse profile is of great interest for many applications. The most common and simple approach to beam shaping is by the use of optical phase masks. Conventional phase masks fabricated by surface profiling using spatially selective etching or deposition are easily damaged and limit high energy applications. We have shown in past work, that it is possible to create different phase profiles in the volume of photo-thermorefractive (PTR) glass, which unlike conventional phase mask materials has a high damage threshold that can withstand high peak and average powers. Here we present an approach for mode conversion of a high power fiber laser system using two different types of phase masks fabricated by encoding phase profiles into volume Bragg gratings. These holographic phase masks (HPMs) can successfully introduce wavefront change and achieve high diffraction efficiency (based on wavelength and the grating strength) for a broad range of wavelengths by tuning the element to the gratings Bragg condition. The first element had a grayscale vortex phase profile for HG1 conversion. The second had a binary four-sector phase profile, and was capable to perform fundamental mode conversion to a TEM01, TEM10, or TEM11. Mode conversion efficiency and thermal stress on each type of phase element were investigated using a 150 W of continuous wave power with a TEM00 profile Yb:fiber laser.

Recently, technology for high resolution device has improved. Accordingly, it is predicted that the demand is increasing. The device such as high-resolution display with amount of data requires large capacity data storage to store the data. Therefore, we considered that holographic data storage that is expected as large capacity can be used as storage device of UHD. However, many errors generate by noises in high density holographic data storage. It is supposed errors can be corrected by clarifying the cause of noises. In order to analyze the noises and correct the errors, light propagation analysis is required. Although several light propagation analysis methods are established, these are not suitable for analyzing holographic data storage. One of the reasons why not suitable is that heavy computation loads can be time-consuming in conventional methods because the thickness of volume holograms are much thicker than the wavelength of propagating light. In this study, we propose light propagation analysis method based on analytic function. In addition, we investigate method that can calculate light propagation in holographic data storage using the method. In holographic data storage, the information is recorded as electric susceptibility distribution of recording medium. This study introduces a parameter related light intensity and sensitive of medium and the Maxwell’s wave equation is expanded by Born-expansion using the parameter. Then, solutions of the wave equation can be solved analytically. Therefore, behavior of light wave in volume hologram can be expressed. We analyze the noises and investigate methods correcting errors by using this method.

Different partially overlapped holograms are reconstructed with digital spatial filter. Compare with the non-overlapped holograms, the overlapped ones show weaker gaps and black lines. The result contributes to improve image quality.

An implementation of full-parallax holographic stereogram printer is presented. The sequence of the two-dimensional perspectives of the three-dimensional object is formed hogel images and produced the entire stereogram. Numerical simulation and optical reconstructions are implemented.

Two different types of holographic printers have been developed that can output holograms on photosensitive materials from digital data calculated as computer-generated holograms to display three-dimensional (3-D) images. The first one is the holographic fringe printer that can write a thin transmission hologram. The other one is the volume hologram printer to write a thick reflection hologram. These printers can output holograms that can provide all physiological depth cues the same as real objects. Therefore, reconstructed images are very natural and do not provide the accommodation-convergence conflict like other 3-D display systems, such as stereoscopic displays. This paper introduces basics of printers, improvements, and reconstructed images.

This paper presents design and implementation of a color wavefront holographic printer. The printer output is a white light viewable volume hologram composed as a two-dimensional (2-D) array of elemental holograms. The three-dimensional (3-D) input data for the printer are encoded as computer generated holograms (CGHs) displayed in succession on an amplitude type spatial light modulator. The printer optical head extracts and demagnifies the beam with the 3-D object information from the beam diffracted by the modulator to produce a small size elemental hologram. This allows for mosaic delivery of exposures at primary colors with each elemental hologram acting as a single color channel. Computer generation of digital contents is accelerated by design of a phase-added stereogram approach based on partitioning of each CGH. Bright 3-D reconstruction with a motion parallax at saturated colors from holograms of test objects is presented. The holograms are printed on a silver-halide emulsion. The achieved high quality proves feasibility of recording analog color volume holograms from digital contents by mosaic delivery of the primary colors. Two quality enhancement approaches are proposed and tested.

In this paper, a new approach is proposed to realize a lens-less and 90° light-bending by a volume-holographic element, consisting of 3D sub-wavelength index-gratings throughout the sample. In this approach, a top incident plane-wave is diffracted by 90° and guided into a planar volume hologram. Conversely, a side-incident light may be guided and diffracted out of the top sample surface. The diffraction-efficiency η of light was studied in real-time during light-exposure and also in the dark after exposure to observe “dark-enhancement”. It is shown that 90° light-bending at normal incidence can be achieved with a high efficiency, η ~70%, and a small angular-tolerance, Δ θ =0.02°. It is further shown, as a proof-of-concept, that a 5° cylindrical-wave top-incident beam may be used to improve angular tolerance to Δ θ =5°, but with a reduced efficiency of η ~0.80%.

We propose a pre-compensated recording process of holographic optical element (HOE) lenses, where both of reference and signal waves have spherical wavefronts, for solving a wavelength mismatch problem between the recording and displaying process. Based on a localized approximation for aperiodic volume gratings, the wavelength mismatch and shrinkage effects are pre-compensated by optimizing the recording setup of HOE lenses, so that the Bragg condition of each local grating is satisfied. In order to realize the practical implementations of recording setup, complicated wavefronts to be required for the wavelength and shrinkage compensation are approximated into spherical waves. The simulation results using the volume hologram models of OpticStudio verify that the undesirable focal shift and color breakup problems in the HOE lens due to the wavelength mismatch are compensated. Displaying experiments using a full-color HOE lens with the field of view of 30° are presented, where the maximum wavelength mismatch between the recording and displaying process is 17 nm.

The volume hologram printer is useful for 3D display, because it is selective to the wavelength and be able to reconstruct with the natural illumination. There are many studies of a volume hologram printer been studied to output a volume hologram from a computer-generated hologram. The final volume hologram consists of tiled small holograms and the tiling manner often causes spilt lines which will have impact on image quality. With an intent to get rid of the split lines and improve the quality, fully overlapping printing was proposed recently. Each elemental hologram is overlapped both in vertical and horizontal directions by 50%. Then, the hologram is printed four times in each area and it makes the printing speed four times slower. For this case, partially overlapping printing is proposed in this paper to improve image quality with small effect in printing speed. For partial overlapping, a digital spatial filter is projected and added to every elemental hologram. Using the digital spatial filter, different partially overlapped holograms are calculated and reconstructed to compare to the non-overlapped ones. The simulation result shows that the overlapped one (10% in both vertical and horizontal) has much weaker gaps and black lines.

A system for replicating high-efficiency volume hologram arrays, which has potential for high-volume manufacturing, is proposed. The system can meet the fabrication requirements of spectrum-splitting photovoltaic systems that are based on transmission volume holographic lens arrays. While previous hologram replication systems are mostly based on variations of the contact-copy method, the new technique is based on diffraction of reference and object beams from a master hologram through a prism and does not require contact with the copy hologram. The replication system has a number of identified advantages over contact-copy systems. An experimental volume holographic lens arrays fabricated using the proposed system had high median diffraction efficiency and low variability (95.3%+/-0.9%).

A replication system and method for fabricating volume hologram arrays is reviewed in this paper. The replication system can be used to fabricate high-efficiency transmission volume holographic lens arrays that are well-suited for spectrum-splitting photovoltaic applications. As in the well-known contact-copy replication technique, the new technique uses a master hologram to generate the desired holographic exposure, however no contact is required with the copy hologram. The object and reference beams for the holographic exposure are generated by discrete “coupling elements” on the master hologram and coupled through a prism to form an interference pattern on the copy hologram. The system can be implemented using relatively inexpensive lab equipment, but also has potential for large-scale production of holographic elements. A prototype system was developed and used to fabricate an experimental holographic lens array with a large aperture (9.6cm X 6cm) and high median diffraction efficiency (95.6%).

We demonstrate the technique of fast, electro-optical control of the transfer function of reflective Bragg grating. The grating is recorded as a volume hologram in LiNbO 3 crystal. We demonstrated a set of different transfer functions with controllable parameters.

We investigate the spatial frequency response of a volume grating recorded in a ZrO2 nanoparticle-dispersed nanocomposite. We experimentally find that there exists the optimum recording intensity to maximize the saturated refractive index modulation amplitude of a nanocomposite grating recorded at short and long grating spacing. A strong parametric relationship between grating spacing and recording intensity is seen and an increase in the saturated refractive index modulation amplitude at shorter grating spacing (< 0.5 μm)can be obtained by using higher recording intensities than those at longer grating spacing. Such a trend can be qualitatively explained by a phenomenological model used for holographic polymer-dispersed liquid crystal gratings. We also describe another method for the improvement of the high spatial frequency response by co-doping of thiol monomer that acts as a chain-transfer agent.

Studies to integrate increased sensory capacities of the wearer on head mounted displays are growing fast for applications in augmented, virtual and mixed reality. This paper focuses on the characterisation of the combiner of the UNO augmented reality glasses by GlassUp: a volume holographic optical element, recorded at 532 nm on Bayfol® HX, providing high diffraction efficiency over a narrow bandwidth at the desired angles. Furthermore, there is a negligible impact on the head mounted display frontal lens’s width and on the view of the real world. Studying the volume hologram, we developed a characterisation tool that gave us insight into the patterns inside the polymer and served as quality check for UNO. In particular, we designed a setup that provides Total Angular Characterisation through Optical Spectroscopy (TACOS), acquiring the visible spectral response of VHOEs as transmittance, reflectance or dispersion maps at arbitrary angles. Furthermore, it analyses the patterns through a custom fit based on the Kogelnik model. The early stages volumetric holograms presented undesirable secondary efficiency peaks causing ghosts, impairing both the vision of the real world and the image projected by the optical module. TACOS’ custom fit allowed us to conduct a quantitative analysis on the ghosts. In this work, we present an equilibrium study on all these parameters to find the better condition of projection. Moreover, we studied the impact of the recording parameters on the appearance of ghosts, e.g. tuning exposure, power ratios.

Utilizing three unique defining properties of volume holograms, namely, wavelength degeneracy, angular selectivity, and multiplexing capability, here we show the recording and simultaneous reconstruction of the Airy and Dual Airy beam from multiplexed volume holographic gratings (MVHGs). Each grating acts independently and creates its own diffraction pattern corresponding to the shape of the grating. Multicolor reconstruction of MVHGs are shown. Experimental results demonstrate that volume holograms are capable of reproducing optical wavefront with high precision without affecting the structural properties of beams at any optical wavelengths. These MGHGs acts as wavelength-independent mode shaper and can be used to make compact optical systems. The volume hologram based beam shaping technique is simple and cost-effective and has potential for the mass production.

Ultrafast femtosecond laser systems have enabled many breakthroughs in the fields of science and technology. However due to the large spectral bandwidth necessary for creating short pulses, it is quite difficult to manipulate their transverse mode structure. Here we present successful femtosecond transverse mode conversion from the fundamental mode TEM00 to modes TEM01, TEM10, and TEM11 with the use of an achromatic phase mask based on diffractive optics. The femtosecond source had ~12.8 nm of bandwidth and pulse duration of

The structurization of holographic planes in holograms recorded in CaF 2 crystal with color centers was found. It is apparent in the formation of spiral bundles, which pierce the holographic planes. It testifies to the self-organization process of color centers in these planes. This process is supposed to be linked with colloidal centers, 2D metal islets in the crystal lattice, whose formation and decay on hologram recording at temperatures of 150–190 °C may be considered as a dynamic phase transition that facilitates the generation of stable spatially inhomogeneous (dissipative) structures in the form of bundles. They arise on hologram recording and are frozen on cooling of the crystal after the recording process is finished.

High-luminance (~1000cd/m2) and high-uniformity see-through eyewear display has been developed by using two in-coupling and one out-coupling reflection volume holograms on optical waveguide glass. This novel volume hologram design achieves an ideal eyewear display for augmented reality with high transparency, high luminance and low power in various environments.

Photothermal effects in a holographic medium of calcium fluoride crystals with color centers $$(\hbox {CaF}_{2})$$ are discussed. It is shown that photochromism of this crystal makes it possible to record volume holograms within its volume and to change their physical properties by photothermal treatments. The diffusion–drift mechanism of a hologram recording in $$\hbox {CaF}_{2}$$ includes the conversion of centers and their redistribution over the crystal bulk. Depending on the readout wavelength, it is possible to read out amplitude, amplitude phase, or phase holograms. The opportunity to record thick holograms in $$\hbox {CaF}_{2}$$ and their high resistance with respect to non-coherent illumination at an elevated temperature allows forming narrow-band angular and spectral holographic filters in $$\hbox {CaF}_{2}$$ .

The wavefront printer records a volume-reflection hologram as a two-dimensional array of elemental holograms from computer-generated holograms (CGHs) displayed on a spatial light modulator (SLM). The wavefront coming from the object is extracted by filtering in the spatial-frequency domain. This paper presents a method to improve color reproduction in a wavefront printer with spatial division of exposures at primary colors, by adaptive partitioning of the SLM in accordance with the color content encoded in the input CGHs, and by the controllable change of exposure times for the recording of primary colors. The method is verified with a color wavefront printer with demagnification of the object beam. The quality of reconstruction achieved by the proposed method proves its efficiency in eliminating the stripe artifacts that are superimposed on reconstructed images in conventional mosaic recording.

A holographic method for measuring linear displacements based on the use of a highly stable volume scale hologram recorded in an additively colored calcium fluoride crystal with photochromic color centers is proposed and experimentally approved. The essence of this method lies in measuring and analyzing harmonic signals formed during linear displacement of crystal with a volume hologram in an external interference field. A physical model of the formation of harmonic signals in photodetectors when measuring displacements is considered, and a mathematical method for calculating linear displacements by plotting a Lissajous figure is substantiated. A laboratory breadboard of a device for measuring linear displacements in a range of 10 mm, limited by the aperture of crystal with a recorded 8.7-mm-thick hologram, is designed. When using a scale hologram with a period of 2.18 μm and a 632.8-nm He-Ne laser for reading this hologram, the error in measuring displacements by this method is 9 nm at a resolution of 3 nm.