Shin-Tson Wu

University of Central Florida | UCF · College of Optics & Photonics

Following the recent experimental discovery of a new polarization conversion phenomenon in polarization volume gratings (PVGs), in this paper, we investigate its underlying physical mechanisms in cholesteric liquid crystal (CLC) reflectors and PVGs. We examine the transition of eigenstates from circular to linear polarization as the incident angle...

Metal halide perovskites (MHPs) have emerged as a promising class of materials for radiation detection due to their high atomic numbers and thus high radiation absorption, tunable and efficient luminescent...

A versatile and tunable vectorial holography is demonstrated based on single-layer single-material liquid crystal superstructures. This novel approach advances the process from scalar to vectorial holography, opening new opportunities for advanced cryptography, super‑resolution imaging, and many other tunable photonic applications.

Augmented reality (AR) displays, heralded as the next-generation platform for spatial computing, metaverse, and digital twins, empower users to perceive digital images overlaid with real-world environment, fostering a deeper level of human-digital interactions. With the rapid evolution of couplers, waveguide-based AR displays have streamlined the e...

We propose a theoretically lossless pancake optics solution that incorporates a nonreciprocal polarization rotator sandwiched between two reflective polarizers. A proof‐of‐concept experiment using a commercially available Faraday rotator (FR) is implemented. The theoretically predicted 100% efficiency can indeed be achieved approximately by using t...

Pancharatnam‐Berry (PB) phase liquid crystal (LC) lenses show attractive benefits in optical systems because of their high efficiency, compact size and polarization‐dependent behavior. However, as a kind of diffraction‐based devices, PB LC lenses suffer from chromatic dispersion, which limits their applications in multi‐wavelength imaging systems....

Blue InGaN/GaN CPC microLED with metallic sidewall can achieve a higher efficiency based on the dipole cloud model in FDTD and electrical model in TCAD. By merely optimizing the p‐GaN contact size, the EQE is improved by 8.7%. Such method helps to achieve high brightness with a lower power consumption.

To achieve wide‐gamut and high‐efficiency tandem white OLED (WOLED) microdisplays, we propose a new structure leveraging from the high‐order antinodes and patterned microcavities. The color gamut coverages of 95% Rec. 2020 and 92% Rec. 2020 can be achieved in B/G/R WOLED with a moderate microcavity and B/YG WOLED with a strong microcavity, respecti...

Tone mapping and mini‐LED backlight algorithms are applied to enhance the sunlight readability of LCDs by fitting the human eye's functionality and increasing image uniformity. Both experimental and simulation results indicate that high luminance displays with an optimized gamma value help to distinguish low grayscale contents under bright ambient...

We analyze the field‐of‐view (FoV) limitations in a single‐layer, full‐color waveguide‐based augmented reality display, revealing key influences from the waveguide's refractive index, exit pupil expansion (EPE) scheme, and combiner's angular response. Based on these analyses, we propose an optimized butterfly EPE scheme with gradient‐pitch polariza...

Liquid‐crystal optics is a promising optical element for near‐eye display as it provides an ultrathin formfactor and lightweight. However, its severe chromatic aberrations impose a big challenge for full‐color display applications. In this study, we demonstrate an achromatic diffractive liquid‐crystal device to overcome this longstanding chromatic...

Compact and high efficiency microdisplays are essential for lightweight augmented reality (AR) glasses to ensure longtime wearing comfort. Liquid-crystal-on-silicon (LCoS) is a promising candidate because of its high-resolution density, high brightness, and low cost. However, its bulky illumination system with a polarizing beam splitter (PBS) cube...

Liquid crystal polarization holograms (LCPHs) based on photo‐alignment and self‐assembled liquid crystal are attractive for the attributes like micrometer ultra‐thinness, high efficiency and dynamic tunability. Previous fabrication methods are limited in the degree‐of‐freedom (DoF) in both photoalignment process and liquid crystal deposition. This...

The sunlight readability of display devices, such as notebook computers, transparent displays, vehicle displays, and augmented reality, is a significant technical challenge due to degraded image quality. To mitigate this problem, by fitting the human eye function, we propose a tone mapping method on a mobile phone display panel to enhance low grays...

Micro-LEDs have found widespread applications in modular large-screen TVs, automotive displays, and high-resolution-density augmented reality glasses. However, these micron-sized LEDs experience a significant efficiency reduction due to the defects originating from the dry etching process. By controlling the current distribution via engineering the...

Pancake lens has been widely used in virtual reality (VR) and mixed reality (MR) due to its compact form factor. However, using a half mirror (HM) to fold the optical path results in a tremendous optical loss. To enhance the optical efficiency while keeping a compact form factor, we present a new folded optical system incorporating a nonreciprocal...

In the quest for more compact and efficient augmented reality (AR) displays, the standard approach often necessitates the use of multiple layers to facilitate a large full‐color field of view (FoV). Here, we delve into the constraints of FoV in single‐layer, full‐color waveguide‐based AR displays, uncovering the critical roles played by the wavegui...

Pancake optics (also known as polarization-based catadioptric system) has been widely used as the imaging lens for virtual reality (VR) and mixed reality (MR) headsets because of its compact formfactor and excellent image quality. However, such a folded pancake optics not only dramatically lowers the optical efficiency to 25% because of the utiliza...

To achieve wide-gamut and high-efficiency tandem white OLED (WOLED) microdisplays, we propose a new structure leveraging high-order antinodes and patterned microcavities. The color gamut coverages of 95% Rec. 2020 and 92% Rec. 2020 can be achieved in B/G/R tandem WOLED with a moderate microcavity and B/YG tandem WOLED with a strong microcavity, res...

Virtual reality/augmented reality (VR/AR/MR) devices provide a platform of basic infrastructure for the next-generation human-computer interfaces. Integrated Optoelectronics for VR/AR/MR technologies plays an essential role in improving the performance and reducing the size/volume/ weight/power consumption for VR/AR/MR systems, and it has become a...

This paper introduces an innovative approach to integral volumetric imaging employing time and polarization multiplexing techniques to present volumetric three-dimensional images. Traditional integral volumetric imaging systems with a coarse lens array often face moiré pattern issues stemming from layered panel structures. In response, our proposed...

Augmented reality (AR) displays, as the next generation platform for spatial computing and digital twins, enable users to view digital images superimposed on real-world environment, fostering a deeper level of human-digital interactions. However, as a critical element in an AR system, optical combiners face unprecedented challenges to match the exc...

Micro LED can play an important role in the future generation of smart displays. They are found very attractive in many applications, such as maskless lithography, biosensor, AR/MR etc., at the same time. A monitor that can fulfill saturated color rendering, high display resolution, and fast response time is highly desirable, and the micro LED-base...

Since the invention of holography by Dennis Gabor, the fabrication of holograms has mainly relied on direct recording of wavefront by engraving the intensity fringes of interfering electric fields into the holographic material. The degree-of-freedom (DoF) is often limited, especially for its usage as a holographic optical element in imaging or disp...

Vehicle displays are becoming more integrated into our daily lives. Achieving a premium driving experience demands the display panel to have high-resolution density and sufficient brightness, particularly when exposed to intense ambient light, as direct sunlight can obscure the displayed images. Combining Barten’s model and diffraction theory, the...

Diffractive liquid-crystal optics is a promising optical element for virtual reality (VR) and mixed reality as it provides an ultrathin formfactor and lightweight for human factors and ergonomics. However, its severe chromatic aberrations impose a big challenge for full-color display applications. In this study, we demonstrate an achromatic diffrac...

A new electrically driven polymer stabilized polarization volume grating (PVG) is developed. Such a switchable PVG exhibits submillisecond response time, large range of diffraction efficiency modulation, and high see‐through quality. Its potential applications, including significantly suppressed rainbow effect and enhanced light efficiency for a wa...

We demonstrate an ultracompact virtual reality (VR) system with thickness of about 1‐cm. In this system, the imaging optics consists of a lenslet array, a deflector array, and a Pancharatnam‐Berry deflector (PBD). We have experimentally demonstrated a polarization interpolation configuration to reduce the system thickness by nearly 50%.

Optimized nanowire LEDs exhibiting a narrower radiation pattern and weaker angular color shift are obtained via 3D dipole cloud model. These RGB nanowires are more efficient than their counterpart micro‐LEDs with chip sizes below 20μm, 80μm, and 10μm, respectively. Promising applications such as high‐brightness directional light engines for AR/VR d...

We achieved the field of view (FoV) limit in a single full‐color waveguide, enabled by an optimized three‐layer polarization volume grating (PVG) as an in‐coupler. Pairing with a single‐layer PVG with small thickness as an out‐coupler, we realized a relatively uniform exit pupil of 6 mm in horizontal direction.

A new folded optical system with an enhanced efficiency using two polarization‐selective cholesteric liquid crystal reflectors is proposed. In conventional pancake optics, the optical path length is tripled but its efficiency drops to 25%. Our new configuration provides 50% efficiency, while the optical path length is doubled.

We demonstrate a foveated AR display based on a single microdisplay light engine by using a temporal polarization multiplexing method, enabled by two polarization selective flat cholesteric liquid crystal lenses. The angular resolution of the foveal view is enhanced by 3.12x while maintaining a compact formfactor.

By systematically analyzing the image degradation caused by the VR optics and display light engines, the requirements for a microdisplay panel, such as contrast ratio, number of local dimming zones, and resolution density are optimized. These results help prevent overdesign of display light engines, e.g., mini‐LED backlit LCDs, OLEDs, or micro‐LEDs...

LCD and OLED are presently the two dominating microdisplays for VR headsets. How to achieve high resolution density for wide field of view and eliminating the screen‐door effect, while keeping low power consumption remains a major challenge. For ultracompact and lightweight AR displays, micro‐LED, OLED‐on‐silicon, MEMS, laser beam scan, and front‐l...

To achieve 60 PPD and 100° FoV while keeping a reasonably high aperture ratio for AMLCDs, field sequential color (FSC) is a promising approach. We evaluate the physical properties of a high birefringence nematic LC mixture and then use these data in simulation. Results indicate that such a fringe‐field switching LCD exhibits a fast average gray‐to‐...

Through 3D dipole cloud model, RGB (red, green, and blue) nanowire light‐emitting diode (LED) structures are geometrically optimized to exhibit a narrower radiation pattern, weaker angular color shift, and higher optical efficiency. In comparison with micro‐LEDs whose external quantum efficiency is dependent on the mesa size, these RGB nanowire LED...

Pancake lens structure offers a promising solution to compact formfactor for near‐eye displays. However, utilizing a half mirror to triple the optical path length causes a dramatic optical loss. The theoretical maximum optical efficiency is only 25%. To balance the tradeoff between compact formfactor and optical efficiency, here we propose a new fo...

Reflective polarization volume gratings (PVGs) can be used as input and output couplers in a diffractive waveguide‐based augmented reality (AR). To improve the stability and wearing comfort, a thin and lightweight full‐color waveguide display is needed. In this paper, we propose a single full‐color waveguide AR display based on PVGs. By analyzing t...

Virtual reality (VR) devices use imaging optics to magnify the microdisplay images for providing an immersive viewing experience. A microdisplay is preferred to have high‐resolution density and high dynamic range to meet the demanding requirements of human vision system (HVS), for example, visual acuity >60 pixels per degree and grayscale depth >10...

A new electrically driven polymer‐stabilized polarization volume grating (PVG) is developed. The diffraction efficiency can be modulated by a vertical electric field. A small amount of liquid crystal monomer is doped into the host cholesteric liquid crystal to form a stabilized polymer network to make the unwinding process reversible. The fabricate...

Compared to conventional bulky spectropolarimeters, computational spectropolarimeters which reconstruct light-field information such as polarization and spectrum in a compact form factor, are critical equipment enabling new applications. The key component of a computational spectropolarimeter is a tunable light-field modulator, in which liquid crys...

To achieve 60 pixels per degree (PPD) and 100° field of view (FoV) while keeping a reasonably high aperture ratio for active-matrix liquid crystal displays (LCDs), field sequential color (FSC) is a promising approach. We evaluate the physical properties of a high birefringence nematic LC mixture and then use these data to simulate the performance o...

Liquid crystal displays (LCDs) and photonic devices play a pivotal role to augmented reality (AR) and virtual reality (VR). The recently emerging high-dynamic-range (HDR) mini-LED backlit LCDs significantly boost the image quality and brightness and reduce the power consumption for VR displays. Such a light engine is particularly attractive for com...

Virtual reality (VR) and augmented reality (AR) have found widespread applications in education, engineering, healthcare, and entertainment. However, these near-eye displays are often bulky and heavy, and thus are not suitable for long-term wearing. Metalenses, with an ultra-thin formfactor, subwavelength modulation scale, and high modulation flexi...

Augmented reality (AR) and virtual reality (VR) have the potential to revolutionize the interface between our physical and digital worlds. Recent advances in digital processing, data transmission, optics, and display technologies offer new opportunities for ubiquitous AR/VR applications. The foundation of this revolution is based on AR/VR display s...

We propose an ultracompact virtual reality (VR) system with three optical components: a lenslet array, a Pancharatnam-Berry phase deflector (PBD), and a deflector array. The lenslet array aims to collect and collimate the input light from the display panel. The PBD steers the deviated beams after the lenslet array toward the optical axis so that th...

Liquid-crystal-based Pancharatnam-Berry optical elements are widely used in virtual reality and augmented reality. However, the mismatch between exposure wavelength and operating wavelength leads to an undesirable phase deviation to the lenses, which in turn causes severe aberration especially when the f-number is small. To overcome the mismatched...

Virtual reality (VR) and augmented reality (AR) have widespread applications. The vergence-accommodation conflict (VAC), which causes 3D visual fatigue, has become an urgent challenge for VR and AR displays. Alvarez lenses, with precise and continuously tunable focal length based on the lateral shift of its two sub-elements, are a promising candida...

The optical phenomena and physicochemical processes triggered by the light-matter interaction enable multiple applications of semiconductor nanomaterials and optoelectronic devices in the photomedicine field. Remarkably, quantum dot (QD) materials are considered highly attractive as individual platforms for multimodal applications, and for the deve...

Virtual reality (VR) and augmented reality (AR) have found widespread applications in education, engineering, healthcare, and entertainment. However, these near-eye displays are often bulky and heavy, and thus are not suitable for long-term wearing. Metalenses, with an ultra-thin formfactor, subwavelength modulation scale, and high modulation flexi...

Alvarez lens, whose focal length can be continuously tuned by changing the relative lateral positions of its sub‐elements, holds promise in realizing vari‐ or multi‐focal augmented reality (AR) displays to eliminate vergence‐accommodation conflict and 3D visual fatigue. In this paper, we propose and realize a compact Alvarez lens based on planar Pa...

We demonstrate a gaze‐matched Maxwellian‐view augmented reality (AR) system with an enlarged eyebox. Such an AR system exhibits several attractive features for practical applications, including aberration‐free, high optical efficiency, highly transparent for ambient light, relatively large field of view, compact size, and lightweight.

A semi‐analytical model is built based on diffraction theory and human angular resolution to quantitatively evaluate the diffraction effect of transparent displays, including micro‐LED and OLED. By optimizing the pixel structures within a 2×2‐pixel size region, the relative diffraction intensity is reduced by 42% at the 50% aperture ratio regardles...

We evaluate and compare the performance of a 15.6‐inch mini‐LED backlit LCD (mLCD) with a commercial OLED panel. Results show that the mLCD exhibits advantages over the OLED panel in peak brightness, gamma curve, color volume, power consumption, and ambient contrast ratio. The LMK imaging photometer with a high‐resolution CMOS sensor is employed to...

By tailoring the radiation pattern through cavity effect, together with a compact compound parabolic concentrator, the light efficiency of μLED is increased by 1.9×. Such a high brightness μLED light engine helps to enhance the ambient contrast ratio for AR displays or to reduce the power consumption for VR headsets.

Present AR and VR displays are facing technical challenges in inadequate angular resolution, limited field‐of‐view, vergence‐accommodation conflict, chromatic aberrations, low optical efficiency, compact size, and lightweight. In this review paper, using novel diffractive liquid crystal devices, including deflectors and lenses, to mitigate these is...

A novel beam steering angle expander is demonstrated by cascading two polymeric liquid crystal polarization lenses with different diopters. The lens module performs as a planar telescope, which is featured as lightweight, low cost, and high precision. The magnifier offers wide‐angle continuous steering when integrated with an active fine‐angle beam...

Transparent displays suffer from background image blur due to light diffraction when passing through periodic pixel structures. A simple, reference‐image free and semi‐analytical model based on diffraction theory and human eye's angular resolution is proposed to quantitatively evaluate the diffraction effect of transparent displays. Several factors...