Publications by authors named "Shin-Tson Wu"

179 Publications

Mini-LED, Micro-LED and OLED displays: present status and future perspectives.

Light Sci Appl 2020 Jun 18;9(1):105. Epub 2020 Jun 18.

College of Optics and Photonics, University of Central Florida, Orlando, FL, 32816, USA.

Presently, liquid crystal displays (LCDs) and organic light-emitting diode (OLED) displays are two dominant flat panel display technologies. Recently, inorganic mini-LEDs (mLEDs) and micro-LEDs (μLEDs) have emerged by significantly enhancing the dynamic range of LCDs or as sunlight readable emissive displays. "mLED, OLED, or μLED: who wins?" is a heated debatable question. In this review, we conduct a comprehensive analysis on the material properties, device structures, and performance of mLED/μLED/OLED emissive displays and mLED backlit LCDs. We evaluate the power consumption and ambient contrast ratio of each display in depth and systematically compare the motion picture response time, dynamic range, and adaptability to flexible/transparent displays. The pros and cons of mLED, OLED, and μLED displays are analysed, and their future perspectives are discussed.
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http://dx.doi.org/10.1038/s41377-020-0341-9DOI Listing
June 2020

Doubling the FOV of AR displays with a liquid crystal polarization-dependent combiner.

Opt Express 2021 Apr;29(8):11512-11519

We propose a glasses-like augmented reality (AR) display with an extended field-of-view (FOV) using a liquid crystal polarization-dependent combiner (PDC). Such a PDC consists of two polarization volume lenses (PVLs) that are based on patterned liquid crystals to selectively control the beam path according to the right-handed or left-handed circularly polarized light. By encoding the left and right half of the FOV into two orthogonal polarization states, the overall horizontal FOV can be doubled while maintaining an ultrathin and flat form factor. Based on this multiplexing concept, the FOV can be further extended by integrating more PVLs with different diffraction angles. The proposed configuration with polarization-time multiplexing provides a promising solution for overcoming the limited FOV issue in AR displays.
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http://dx.doi.org/10.1364/OE.422639DOI Listing
April 2021

Aberration-free pupil steerable Maxwellian display for augmented reality with cholesteric liquid crystal holographic lenses.

Opt Lett 2021 Apr;46(7):1760-1763

Maxwellian displays offer unique features like always-in-focus quality, high efficiency, and large field-of-view, but its small eyebox remains a major challenge for augmented reality. To enlarge the eyebox, pupil steering is a promising approach. However, previous pupil steering methods generally rely on changing the incident light angle on the lens coupler, which results in serious aberrations. In this Letter, we demonstrate a pupil steerable see-through Maxwellian display incorporating novel cholesteric liquid crystal (CLC) holographic lenses. By actively modulating the polarization state of the incident light, we can schematically choose which holographic lens to function, which fundamentally eliminates the aberrations.
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http://dx.doi.org/10.1364/OL.422559DOI Listing
April 2021

Peculiar polarization response in chiral liquid crystal stacks for multispectral camouflage.

Opt Express 2021 Jan;29(2):2931-2939

Chiral liquid crystals are self-organized Bragg reflectors which respond to circularly polarized light. Manipulation of the chiral structure has aroused great research interest. The x-y plane two-dimensional patterning of chiral liquid crystals leads to reflective planar optics, and the z-axis modulation results in a variety of photonic bandgap controls. Here, the optical properties of even-number left- and right-handed chiral liquid crystal stacks are investigated, with emphasis on the linear polarization response. Under certain conditions, a linearly polarized incidence can result in a linearly polarized reflected light. More intriguingly, the linear polarization has different forms of response to thick and thin chiral liquid crystal sublayers and responds to the rotation of liquid crystal alignment. Based on the peculiar polarization response, a new type of wavelength-response camouflage and anti-counterfeiting is conceptually proposed, which can hide two different images simultaneously within a small spectral range. Our work paves the way for three-dimensional manipulation of chiral liquid crystals and enlightens novel applications.
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http://dx.doi.org/10.1364/OE.417521DOI Listing
January 2021

Broadband cholesteric liquid crystal lens for chromatic aberration correction in catadioptric virtual reality optics.

Opt Express 2021 Feb;29(4):6011-6020

A planar and broadband cholesteric liquid crystal (CLC) lens is designed, fabricated, and hybridized with a refractive lens to form a catadioptric pancake lens for virtual reality (VR) displays. Due to their opposite optical dispersion behaviors, the chromatic aberration of the assembled pancake lens is dramatically suppressed, as verified by both ray-tracing analysis and experimental results. The demonstrated catadioptric pancake lens has great potential for next-generation VR displays.
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http://dx.doi.org/10.1364/OE.419595DOI Listing
February 2021

Large-angle two-dimensional grating with hybrid mechanisms.

Opt Lett 2021 Feb;46(4):920-923

We demonstrate a large-diffraction-angle two-dimensional (2D) grating based on cholesteric liquid crystal (CLC). One dimension is a polarization volume grating (PVG) working in the Bragg regime, which is produced by a patterned photoalignment layer. The other dimension is a CLC grating working in the Raman-Nath regime, which is introduced by CLC self-assembly under a weak anchoring energy condition. The condition for the coexistence of the CLC Raman-Nath grating (RNG) and PVG is analyzed, and the efficiency and grating period of the CLC RNG are also characterized. Potential application of this 2D grating for enlarging the eyebox of augmented reality displays is discussed.
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http://dx.doi.org/10.1364/OL.417468DOI Listing
February 2021

Halo effect in high-dynamic-range mini-LED backlit LCDs.

Opt Express 2020 Nov;28(24):36822-36837

We develop an optical model including the glare effect in the human vision system to analyze the halo effect of high-dynamic-range (HDR) mini-LED backlit liquid crystal displays (LCDs). In our model, an objective function is first introduced to evaluate the severity of the halo effect with different image contents. This function is further combined with PSNR to establish a new evaluation metric to analyze the image quality affected by the halo effect. A subjective visual experiment is also conducted to verify the above-mentioned evaluation metrics. In addition, we analyze the influence of ambient environment (viewing angle and ambient light illuminance) on the halo effect. After considering the requirements on local dimming zones, dynamic contrast ratio, gamma shift, and color shift for practical applications, we find that fringe-field-switching mode is a strong contender for the mini-LED backlit LCD system.
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http://dx.doi.org/10.1364/OE.413133DOI Listing
November 2020

Rigorous coupled-wave analysis of liquid crystal polarization gratings.

Opt Express 2020 Nov;28(24):35960-35971

Several types of liquid crystal polarization gratings (LCPGs) can be achieved depending on their molecular configurations and diffraction properties. We perform detailed numerical studies of these LCPGs based on the rigorous coupled-wave analysis (RCWA) approach. The unique properties of Raman-Nath and Bragg gratings are investigated, and how the transition between them influences the diffraction behaviors is explained. Two types of LCPGs, corresponding to the planar and the slanted director configurations, are compared in detail. The influence of gradient-pitch on the performance of reflection grating is also explored. Potential applications of these LCPGs for near-eye displays are emphasized.
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http://dx.doi.org/10.1364/OE.410271DOI Listing
November 2020

Maxwellian near-eye display with an expanded eyebox.

Opt Express 2020 Dec;28(26):38616-38625

Maxwellian view systems can be employed to circumvent the vergence-accommodation conflict in near-eye displays (NEDs), which directly project images onto the retina regardless of the human eye's depth of focus. However, Maxwellian view optics typically have a limited eyebox, which prevents broader applications of this architecture in NEDs. Here, we demonstrate a thin-film two-dimensional beam deflector composed of multi-twist broad-band Pancharatnam-Berry deflectors to mitigate this limitation via eyebox replication. Based on experimental validation, our proposed design can display always-focused full-color images within a 9 mm × 9 mm eyebox and thus mitigate the limitation of conventional Maxwellian displays while adding negligible weight and volume.
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http://dx.doi.org/10.1364/OE.413471DOI Listing
December 2020

Patterning Liquid-Crystal Alignment for Ultrathin Flat Optics.

ACS Omega 2020 Dec 3;5(49):31485-31489. Epub 2020 Dec 3.

College of Optics and Photonics University of Central Florida, Orlando, Florida 32816, United States.

Liquid-crystal (LC)-based ultrathin flat optical elements (FOEs) exhibit several attractive properties, such as a high degree of optical tunability, strong polarization selectivity, nearly 100% diffraction efficiency, and a simple fabrication process. Investigating the alignment patterning of LC-FOEs to diversify their performance has attracted broad interest in the optics field. In this mini-review, we start from the photoalignment (PA) process and then dive into device structures and performances. By generating and recording the desired polarization fields on the PA layer, the LC molecules will follow the recorded patterns and establish the phase profiles for different functionalities, such as gratings and lenses. Because of the polarization dependency, LC-FOEs have found useful applications in near-eye displays. Understanding the interactions between the PA mechanism and LC molecules helps to optimize the device performance for novel optical systems.
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http://dx.doi.org/10.1021/acsomega.0c05087DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7745223PMC
December 2020

Enhancing the Efficiency of Color Conversion Micro-LED Display with a Patterned Cholesteric Liquid Crystal Polymer Film.

Nanomaterials (Basel) 2020 Dec 5;10(12). Epub 2020 Dec 5.

College of Optics and Photonics, University of Central Florida, Orlando, FL 32816, USA.

Color-converted micro-light-emitting diode (micro-LED) displays with wide color gamut, high ambient contrast ratio, and fast response time are emerging as a potentially disruptive technology. However, due to limited optical density and thickness of the color-conversion film, the blue light leakage and low color-conversion efficiency still hinder their widespread applications. In this paper, we demonstrate a patterned cholesteric liquid crystal (CLC) polymer film with two special optical functionalities. On the green and red sub-pixels, the corresponding planar CLC texture acts as a distributed Bragg reflector for the blue light, which in turn improves the color conversion efficiency and expands the color gamut. On the blue sub-pixels, the corresponding focal-conic CLC texture acts as light scattering medium, which helps to reduce the angular color shift. Further analysis reveals that the patterned CLC film can alleviate the crosstalk between green and blue color filters. Therefore, compared to the display system without such a CLC film, our proposed device structure increases the color conversion efficiency by 143% (at ~90% Rec. 2020) and reduces average angular color shift Δu'v' from 0.03 to 0.018 at the viewing angle with the most severe color shift. Such a patterned CLC film is applicable to all kinds of color-conversion display systems, including organic and inorganic phosphors.
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http://dx.doi.org/10.3390/nano10122430DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7762002PMC
December 2020

Submillisecond-Response Polymer Network Liquid Crystal Phase Modulators.

Polymers (Basel) 2020 Nov 30;12(12). Epub 2020 Nov 30.

College of Optics and Photonics, University of Central Florida, Orlando, FL 32816, USA.

A submillisecond-response and light scattering-free polymer-network liquid crystal (PNLC) for infrared spatial light modulators is demonstrated. Our new liquid crystal host exhibits a higher birefringence, comparable dielectric anisotropy, and slightly lower visco-elastic constant than a commonly employed commercial material, HTG-135200. Moreover, the electro-optical performance of our PNLCs with different monomer concentrations, cell gaps, and liquid crystal (LC) hosts is compared and discussed from four aspects: operating voltage, hysteresis, relaxation time, and light scattering loss. The temperature effect on hysteresis is also analyzed. Potential applications of PNLCs for laser beam steering and spatial light modulators especially in the infrared region are foreseeable.
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http://dx.doi.org/10.3390/polym12122862DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7760688PMC
November 2020

Augmented Reality and Virtual Reality Displays: Perspectives and Challenges.

iScience 2020 Aug 22;23(8):101397. Epub 2020 Jul 22.

College of Optics and Photonics, University of Central Florida, Orlando, FL 32816, USA. Electronic address:

As one of the most promising candidates for next-generation mobile platform, augmented reality (AR) and virtual reality (VR) have potential to revolutionize the ways we perceive and interact with various digital information. In the meantime, recent advances in display and optical technologies, together with the rapidly developing digital processers, offer new development directions to advancing the near-eye display systems further. In this perspective paper, we start by analyzing the optical requirements in near-eye displays poised by the human visual system and then compare it against the specifications of state-of-the-art devices, which reasonably shows the main challenges in near-eye displays at the present stage. Afterward, potential solutions to address these challenges in both AR and VR displays are presented case by case, including the most recent optical research and development, which are already or have the potential to be industrialized for extended reality displays.
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http://dx.doi.org/10.1016/j.isci.2020.101397DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7404571PMC
August 2020

Standing wave polarization holography for realizing liquid crystal Pancharatnum-Berry phase lenses.

Opt Express 2020 Jul;28(15):21729-21736

A standing wave polarization holography setup is proposed to generate the desired polarization field for fabricating both on-axis and off-axis liquid crystal Pancharatnum-Berry phase lenses. Compared to other interference exposure setups, standing wave interferometry can double the polarization field amplitude because it does not require a beam splitter. Moreover, the optical axis angle of the lenses can be easily adjusted without realigning the optical setup. Based on the design, we first theoretically derive the polarization field distribution. In the experiment, we build the recording optical system and fabricate a series of on-axis and off-axis lenses. Further optical characterization proves the high diffraction efficiency of the fabricated lenses.
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http://dx.doi.org/10.1364/OE.399036DOI Listing
July 2020

High dynamic range head-up displays.

Opt Express 2020 Aug;28(16):24298-24307

We demonstrate a full-color high dynamic range head-up display (HUD) based on a polarization selective optical combiner, which is a three-layer cholesteric liquid crystal (CLC) film. Such a CLC film has three reflection bands corresponding to the three primary colors. A key component in our HUD system is a polarization modulation layer (PML) consisting of a twisted-nematic LC polarization rotator sandwiched by two quarter-wave plates. This spatially switchable PML generates opposite polarization states for the displayed image and its background area. Thus, this optical combiner reflects the displayed image to the observer and transmits the background noise, making the black state darker. Furthermore, by matching the reflection spectra of the optical combiner with the colors of the display panel, the bright state gets brighter. Therefore, both bright state and dark state are improved simultaneously. Our experimental results show that the dark state of the new HUD is lowered by 3x and bright state is boosted by 2.5x. By applying antireflection coating to the optical components and optimizing the degree of polarization, our simulation results indicate that the dynamic range can be improved by ∼50x (17 dB). Potential applications of the proposed HUDs for improving the driver's safety are foreseeable.
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http://dx.doi.org/10.1364/OE.400154DOI Listing
August 2020

Foveated display system based on a doublet geometric phase lens.

Opt Express 2020 Aug;28(16):23690-23702

We propose a new concept of a foveated display with a single display module. A multi-resolution and wide field of view (FOV) can be simultaneously achieved using only a single display, based on temporal polarization-multiplexing. The polarization-dependent lens set functions as an optical window or beam expander system depending on the polarization state, which can provide two operating modes: fovea mode for a high-resolution and peripheral mode for a wide viewing angle. By superimposing two-mode images, the proposed system supports a foveated and wide FOV image without an ultra-high-resolution display. We demonstrate the feasibility of the proposed configuration through the proof-of-concept system.
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http://dx.doi.org/10.1364/OE.399808DOI Listing
August 2020

Mini-LED, Micro-LED and OLED displays: present status and future perspectives.

Light Sci Appl 2020 18;9:105. Epub 2020 Jun 18.

College of Optics and Photonics, University of Central Florida, Orlando, FL 32816 USA.

Presently, liquid crystal displays (LCDs) and organic light-emitting diode (OLED) displays are two dominant flat panel display technologies. Recently, inorganic mini-LEDs (mLEDs) and micro-LEDs (μLEDs) have emerged by significantly enhancing the dynamic range of LCDs or as sunlight readable emissive displays. "mLED, OLED, or μLED: who wins?" is a heated debatable question. In this review, we conduct a comprehensive analysis on the material properties, device structures, and performance of mLED/μLED/OLED emissive displays and mLED backlit LCDs. We evaluate the power consumption and ambient contrast ratio of each display in depth and systematically compare the motion picture response time, dynamic range, and adaptability to flexible/transparent displays. The pros and cons of mLED, OLED, and μLED displays are analysed, and their future perspectives are discussed.
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http://dx.doi.org/10.1038/s41377-020-0341-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7303200PMC
June 2020

Self-assembled plasmonics for angle-independent structural color displays with actively addressed black states.

Proc Natl Acad Sci U S A 2020 Jun 3;117(24):13350-13358. Epub 2020 Jun 3.

Department of Physics, University of Central Florida, Orlando, FL 32816;

Nanostructured plasmonic materials can lead to the extremely compact pixels and color filters needed for next-generation displays by interacting with light at fundamentally small length scales. However, previous demonstrations suffer from severe angle sensitivity, lack of saturated color, and absence of black/gray states and/or are impractical to integrate with actively addressed electronics. Here, we report a vivid self-assembled nanostructured system which overcomes these challenges via the multidimensional hybridization of plasmonic resonances. By exploiting the thin-film growth mechanisms of aluminum during ultrahigh vacuum physical vapor deposition, dense arrays of particles are created in near-field proximity to a mirror. The sub-10-nm gaps between adjacent particles and mirror lead to strong multidimensional coupling of localized plasmonic modes, resulting in a singular resonance with negligible angular dispersion and ∼98% absorption of incident light at a desired wavelength. The process is compatible with arbitrarily structured substrates and can produce wafer-scale, diffusive, angle-independent, and flexible plasmonic materials. We then demonstrate the unique capabilities of the strongly coupled plasmonic system via integration with an actively addressed reflective liquid crystal display with control over black states. The hybrid display is readily programmed to display images and video.
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http://dx.doi.org/10.1073/pnas.2001435117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7306820PMC
June 2020

Absorption-based polarization gratings.

Opt Express 2020 Apr;28(9):13907-13912

We demonstrate an absorption-based polarization grating made of dichroic dye-doped polymerizable liquid crystal. These gratings manifest a polarization-sensitive diffraction efficiency over the absorption band of the employed dye material, based on our theoretical analysis and experimental evidence. The spectral range can be easily tailored by varying the dye material. Since these gratings generate first-order diffracted beams with orthogonal circular polarizations, they can be utilized as key components in polarimetry systems. Meanwhile, due to their absorptive nature, these polarization gratings can function as LED-compatible polarization masks for photopatterning while fabricating various liquid crystal devices.
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http://dx.doi.org/10.1364/OE.392550DOI Listing
April 2020

Passive polymer-dispersed liquid crystal enabled multi-focal plane displays.

Opt Express 2020 May;28(10):15294-15299

A multi-focal plane see-through near-eye display using a transparent projection display is demonstrated. The key component of the transparent projection display is a passive polymer-dispersed liquid crystal (PDLC), which is highly transparent for a large range of incident angles in air but strongly scattering at large oblique angles in high refractive index medium (e.g. glass). The use of a passive device can avoid temporal multiplexing. Such a display is highly transparent in air and can easily deliver full-color images. The proposed method is an important step toward transparent display-enabled multi-focal plane displays.
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http://dx.doi.org/10.1364/OE.392489DOI Listing
May 2020

Flat cholesteric liquid crystal polymeric lens with low f-number.

Opt Express 2020 Feb;28(4):5875-5882

We use a simple photoalignment method to fabricate four reflective cholesteric liquid crystal (CLC) polymeric lenses with diameter D=2.45 cm and low f-numbers (f/2, f/0.9, f/0.45, f/0.33) at 550 nm. Such a flat CLC lens can be converging or diverging, depending on the handedness and direction of the incident light. Our CLC lenses can achieve ∼85% diffraction efficiency for a designated polarization state and manifest decent imaging ability.
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http://dx.doi.org/10.1364/OE.387942DOI Listing
February 2020

Broadband wide-view Pancharatnam-Berry phase deflector.

Opt Express 2020 Feb;28(4):4921-4927

We demonstrate a high-efficiency achromatic, wide-view Pancharatnam-Berry phase deflector (PBD) based on a three-layer multi-twist structure. A practical method to measure the thickness and twist angle of liquid crystal (LC) polymer films is developed based on Jones matrix of twist-nematic liquid crystals. With the help of this new measurement method, we fabricated a three-layer multi-twist PBD. The imaging performance and the angular response of the achromatic wide-view PBD are also characterized. Potential application of PBD for near-eye displays is foreseeable.
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http://dx.doi.org/10.1364/OE.385540DOI Listing
February 2020

Chirped polarization volume grating with ultra-wide angular bandwidth and high efficiency for see-through near-eye displays.

Opt Express 2019 Nov;27(24):35895-35902

We report a reflective chirped polarization volume grating (CPVG) with a dramatically wider angular bandwidth and significantly higher first-order diffraction efficiency than the holographic volume grating and surface relief grating for large field-of-view (FOV) augmented reality (AR) displays. By introducing gradient pitch structure along the beam propagation direction, the angular bandwidth is extended from 18° to 54° while keeping over 80% diffraction efficiency. We also prepare a two-layer reflective PVG and compare its performance with the chirped structure. Based on the simulation and experimental results, CPVG is a strong contender for large FOV AR displays.
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http://dx.doi.org/10.1364/OE.27.035895DOI Listing
November 2019

Swelling-Deswelling Microencapsulation-Enabled Ultrastable Perovskite-Polymer Composites for Photonic Applications.

Chem Rec 2020 Jul 13;20(7):672-681. Epub 2019 Dec 13.

College of Optics and Photonics, University of Central Florida, Orlando, Florida, 32816, USA.

Metal halide perovskite nanocrystals are emerging as novel optoelectronic materials. Owing to their excellent optical and electronic properties such as tunable band gap, narrow-band emission and high charge mobility, they are quite promising in various fields including liquid-crystal display backlighting, solid-state lighting and other energy conversion applications. However, the intrinsic low formation energy makes them vulnerable to external stimulus, e. g. water, oxygen, heat, etc. Among many methods, swelling-deswelling microencapsulation emerges as one of the most promising strategies to improve their stability. Herein, recent developments and future research directions in swelling-deswelling microencapsulation-enabled ultrastable perovskite-polymer composites are summarized. We believe this strategy has great potential to deliver successful perovskite-based commercial products for many photonics applications.
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http://dx.doi.org/10.1002/tcr.201900074DOI Listing
July 2020

A versatile method for fabricating Pancharatnam-Berry micro-optical elements.

Opt Express 2019 Sep;27(20):27831-27840

We report a simple method for fabricating Pancharatnam-Berry micro-optical elements based on relayed Mach-Zehnder interferometer. Two major advantages are fast processing speed and good quality phase profile. Both active and passive micro-lens arrays are fabricated and their imaging performances characterized. To demonstrate the versatility of the proposed method, we also fabricated asymmetric, axial-symmetric, and concentric types of micro-lens arrays.
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http://dx.doi.org/10.1364/OE.27.027831DOI Listing
September 2019

Wavelength-multiplexed multi-focal-plane seethrough near-eye displays.

Opt Express 2019 Sep;27(20):27507-27513

We demonstrate a multi-focal-plane see-through near-eye display with effective focus cues enabled by wavelength multiplexing. A spectral notch filter is implemented as the wavelength-sensitive depth separation element. The vergence-accommodation conflict can be mitigated with the proposed design without space- or time-multiplexing. Another design of a dual-focus projection module for the waveguide-type augmented reality devices using wavelength-multiplexing is also presented.
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http://dx.doi.org/10.1364/OE.27.027507DOI Listing
September 2019

Angular color shift of micro-LED displays.

Opt Express 2019 Jun;27(12):A746-A757

Sidewall emission of a micro-scale light emitting diode (micro-LED) improves the light extraction efficiency, but it causes mismatched angular distributions between AlGaInP-based red micro-LED and InGaN-based blue/green counterparts due to material difference. As a result, color shift of RGB micro-LED displays may become visually noticeable. To address this issue, we first analyze the angular distributions of RGB micro-LEDs and obtain good agreement between simulation and experiment. Next, we propose a device structure with top black matrix and taper angle in micro-LEDs, which greatly suppresses the color shift while keeping a reasonably high light extraction efficiency.
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http://dx.doi.org/10.1364/OE.27.00A746DOI Listing
June 2019

Photo- and electrical-responsive liquid crystal smart dimmer for augmented reality displays.

Opt Express 2019 Jun;27(13):18169-18179

A dual-stimuli polarizer-free dye-doped liquid crystal (LC) dimmer is demonstrated. The LC composition consists of photo-stable chiral agent, photosensitive azobenzene, and dichroic dye in a nematic host with positive dielectric anisotropy. Upon UV exposure, the LC directors and dye molecules turn from initially vertical alignment (high transmittance state) to twisted fingerprint structure (low transmittance state). The reversal process is accelerated by combining a longitudinal electric field to unwind the LC directors from twisted fingerprint to homeotropic state, and a red light to transform the cis azobenzene back to trans. This device can be used as a smart dimmer to enhance the ambient contrast ratio for augmented reality displays.
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http://dx.doi.org/10.1364/OE.27.018169DOI Listing
June 2019

Device simulation of liquid crystal polarization gratings.

Opt Express 2019 Jun;27(13):18102-18112

Liquid crystal polarization gratings manifest several unique features, such as high diffraction efficiency, polarization selectivity, and fast switching time. However, few works address the chiral-doped liquid crystal alignment issue in such gratings. Here, we develop an improved relaxation method to analyze the liquid crystal director distribution in chiral-doped polarization gratings. Our simulation result agrees well with experimental data on a polarization volume grating. The criteria for forming planar or slanted polarization grating are discussed.
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http://dx.doi.org/10.1364/OE.27.018102DOI Listing
June 2019

Improving near-eye display resolution by polarization multiplexing.

Opt Express 2019 May;27(11):15327-15334

We present here an optical approach to boost the apparent pixel density by utilizing the superimposition of two shifted-pixel grids generated by a Pancharatnam-Berry deflector (PBD). The content of the two shifted pixel grids are presented to the observer's eye simultaneously using a polarization-multiplexing method. Considering the compact and lightweight nature of PBD, this approach has potential applications in near-eye display systems. Moreover, the same concept can be extended to projection displays with proper modifications.
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http://dx.doi.org/10.1364/OE.27.015327DOI Listing
May 2019