Joel K.W. Yang

Joel K.W. Yang
Singapore University of Technology and Design · Division of Engineering Product Development

PhD

About

230
Publications
58,922
Reads
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12,208
Citations
Introduction
Joel K.W. Yang currently works at the Division of Engineering Product Development, Singapore University of Technology and Design. Joel does research in Optics, Materials Science and Experimental Physics. His research interest is in Nano-Optics and Nanofabrication where one observes and engineers the unique properties of light as it interacts with nanoscopic objects. This knowledge enables the creation of color prints with unprecedented detail (viewable under a microscope), holographic color prints, antennas for directing quantum emitters, and more.
Additional affiliations
September 2013 - present
Singapore University of Technology and Design
Position
  • Professor (Assistant)
August 2009 - present
Agency for Science, Technology and Research (A*STAR)
Position
  • Researcher
February 2009 - August 2009
Massachusetts Institute of Technology
Position
  • PostDoc Position
Education
January 2004 - February 2009
Massachusetts Institute of Technology
Field of study
  • Electrical Engineering

Publications

Publications (230)
Article
Full-text available
Bound-states-in-the-continuum (BIC) is an emerging concept in nanophotonics with potential impact in applications, such as hyperspectral imaging, mirror-less lasing, and nonlinear harmonic generation. As true BIC modes are non-radiative, they cannot be excited by using propagating light to investigate their optical characteristics. In this paper, f...
Article
Full-text available
Exciton is a bosonic quasiparticle consisting of a pair of electron and hole, with promising potentials for optoelectronic device applications, such as exciton transistors, photodetectors and light emitting devices. However, the charge-neutral nature of excitons renders them challenging to manipulate using electronics. Here we present the generatio...
Article
Full-text available
Laser probing remains invaluable to the semiconductor industry for isolating and diagnosing defects in silicon transistors in integrated circuits during electrical stress tests. However, continuous device miniaturization below the 20 nm technology node has crammed multiple transistors within the focal spot of the laser beam, resulting in signal cro...
Article
Additive manufacturing produces 3D geometries by depositing material in a layer-by-layer fashion. Commonly, the resolution of additive manufacturing is in the millimeter and micrometer scales, due to limitations in mechanical precision and material properties. In the past two decades, nanoscale additive manufacturing has been achieved using femtose...
Article
Phase transitions can occur in certain materials such as transition metal oxides (TMOs) and chalcogenides when there is a change in external conditions such as temperature and pressure. Along with phase transitions in these phase change materials (PCMs) come dramatic contrasts in various physical properties, which can be engineered to manipulate el...
Preprint
The orbital angular momentum (OAM) of light holds great promise for applications in optical communication, super-resolution imaging, and high-dimensional quantum computing. However, the spatio-temporal coherence of the light source has been essential for generating OAM beams, as incoherent ambient light would result in polychromatic and obscured OA...
Preprint
Full-text available
In this paper we propose and demonstrate single subwavelength hybrid dielectric-plasmonic optical nanoantennas coupled to localised quantum dot emitters that constitute efficient and bright unidirectional photon sources under optical pumping. To achieve this, we devised a silicon nanoring sitting on a metallic (gold) mirror with a $10\,$nm gap in b...
Preprint
Full-text available
In optical anti-counterfeiting, several distinct optically variable devices (OVDs) are often concurrently employed to compensate for the insufficient security level of constituent OVDs. Alternatively, metasurfaces that exhibit multiple optical responses effectively combine multiple OVDs into one, thus significantly enhancing their security and hind...
Preprint
Digital camera sensors utilize color filters on photodiodes to achieve color selectivity. As color filters and photosensitive silicon layers are separate elements, these sensors suffer from optical cross-talk, which sets limits to the minimum pixel size. In this paper, we report hybrid silicon-aluminum nanostructures in the extreme limit of zero di...
Article
Design flexibility, ease of use, and reduced wastage have made additive manufacturing well suited for producing functional prints in many fields including optics. As surface quality is compromised in many cases, postprocessing or better fabrication techniques are required. Advanced fabrication techniques such as two-photon polymerization lithograph...
Article
It remains a challenge to directly print arbitrary three-dimensional shapes that exhibit structural colors at the micrometer scale. Woodpile photonic crystals (WPCs) fabricated via two-photon lithography (TPL) are elementary building blocks to produce 3D geometries that generate structural colors due to their ability to exhibit either omnidirection...
Article
We demonstrate a passive all-chalcogenide all-optical perceptron scheme. The network’s nonlinear activation function (NLAF) relies on the nonlinear response of Ge2Sb2Te5 to femtosecond laser pulses. We measured the sub-picosecond time-resolved optical constants of Ge2Sb2Te5 at a wavelength of 1500 nm and used them to design a high-speed Ge2Sb2Te5-t...
Preprint
Full-text available
When gratings are illuminated by white light, they produce an angular distribution of wavelengths dependent on the diffraction order and grating periodicity. Previous studies of gratings mostly focused on highly ordered structures with at least one geometric parameter (height, periodicity, orientation, angle of incidence) kept constant. However, th...
Article
Full-text available
While structural colors are ubiquitous in nature, saturated reds are mysteriously absent. This long-standing problem of achieving Schrödinger's red demands sharp transitions from "stopband" to a high-reflectance "passband" with total suppression of higher-order resonances at blue/green wavelengths. Current approaches based on nanoantennas are insuf...
Article
The objective of this Opinion is to stimulate new research into materials that can meet the needs of tomorrow’s programmable photonics components. Herein, we argue that the inherent property portfolios of the common telluride phase change materials, which have been successfully applied in data storage technologies, are unsuitable for most emerging...
Preprint
Reconfigurable metamaterials require constituent nanostructures to demonstrate switching of shapes with external stimuli. For generality, such nanostructures would touch and stick to other surfaces in one of its configurations. Yet, a longstanding challenge is in overcoming this stiction caused by Van der Waals forces, which impedes shape recovery....
Article
Full-text available
Color changes can be achieved by straining photonic crystals or gratings embedded in stretchable materials. However, the multiple repeat units and the need for a volumetric assembly of nanostructures limit the density of information content. Inspired by surface reliefs on oracle bones and music records as means of information archival, here we endo...
Article
Full-text available
Color tuning is a fascinating and indispensable property in various applications. Thus far, a variety of reconfigurable approaches have been implemented to achieve color change. However, it is still a challenge to enable continuous color tuning over the entire hue range in a simple, stable, and rapid manner without changes in configuration and mate...
Preprint
It remains a challenge to directly print three-dimensional arbitrary shapes that exhibit structural colors at the micrometer scale. Woodpile photonic crystals (WPCs) fabricated via two-photon lithography (TPL) are promising as building blocks to produce 3D geometries that generate structural colors due to their ability to exhibit either omnidirecti...
Preprint
Colour changes can be achieved by straining photonic crystals or gratings embedded in stretchable materials. However, the multiple repeat units and the need for a volumetric assembly of nanostructures limit the density of information content. Inspired by surface reliefs on oracle bones and music records as means of information archival, here we end...
Preprint
Color tuning is a fascinating and indispensable property in applications such as advanced display, active camouflaging and information encryption. Thus far, a variety of reconfigurable approaches have been implemented to achieve color change. However, it is still a challenge to enable a continuous color tuning over the entire hue range in a simple,...
Preprint
Dielectric optical nanoantennas play an important role in color displays, metasurface holograms, and wavefront shaping applications. They usually exploit Mie resonances as supported on nanostructures with high refractive index, such as Si and TiO2. However, these resonances normally cannot be tuned. Although phase change materials, such as the germ...
Preprint
While structural colors are ubiquitous in nature, saturated reds are mysteriously absent. Hence, a longstanding problem is in fabricating nanostructured surfaces that exhibit reflectance approaching the theoretical limit. This limit is termed the Schrodinger red and demands sharp spectral transitions from "stopband" to a high reflectance "passband"...
Article
Full-text available
A light field print (LFP) displays three-dimensional (3D) information to the naked-eye observer under ambient white light illumination. Changing perspectives of a 3D image are seen by the observer from varying angles. However, LFPs appear pixelated due to limited resolution and misalignment between their lenses and colour pixels. A promising soluti...
Preprint
Bound-states-in-the-continuum (BIC)is a wave-mechanical concept that generates resonances with vanishing spectral linewidths. It has many practical applications in Optics, such as narrow-band filters, mirror-less lasing, and nonlinear harmonic generation. As true BIC optical modes non-radiative and confined to the near field of nanostructures, they...
Article
Efficient generation of anti-Stokes emission within nanometric volumes enables the design of ultracompact, miniaturized photonic devices for a host of applications. Many subwavelength crystals, such as metal nanoparticles and two-dimensional layered semiconductors, have been coupled with plasmonic nanostructures for augmented anti-Stokes luminescen...
Article
Full-text available
Four-dimensional (4D) printing of shape memory polymer (SMP) imparts time responsive properties to 3D structures. Here, we explore 4D printing of a SMP in the submicron length scale, extending its applications to nanophononics. We report a new SMP photoresist based on Vero Clear achieving print features at a resolution of ~300 nm half pitch using t...
Article
Three-dimensional (3D), ordered nanoporous Cu2O and Cu inverse opal structures are attractive for various applications in photonics and catalysis. Here, we demonstrate an approach to fabricate 3D nanoporous inverse opals by electroplating through a uniform polystyrene (PS) opal template. The material composition of the inverse opals can be controll...
Preprint
A light field print (LFP) displays three-dimensional (3D) information to the naked-eye observer under white light illumination. Changing perspectives of a 3D image are seen by the observer from varying angles. However, LFPs appear pixelated due to limited resolution and misalignment between lenses and colour pixels. With advanced nanofabrication te...
Article
Full-text available
Materials that exhibit large and rapid switching of their optical properties in the visible spectrum hold the key to color-changing devices. Antimony trisulfide (Sb 2 S 3 ) is a chalcogenide material that exhibits large refractive index changes of ~1 between crystalline and amorphous states. However, little is known about its ability to endure mult...
Conference Paper
Short wavelength probing (SWP) uses wavelengths of light shorter than 1100 nm or energies higher than silicon bandgap for laser probing applications. While SWP allows a significant improvement to spatial resolution, there are aberrations to the collected laser probing waveforms which result in difficulties in signal interpretations. In this work, w...
Article
Full-text available
Integrating micro-optical components at the end facet of an optical fiber enables compact optics to shape the output beam (e.g. collimating, focusing, and coupling to free space elements or photonic integrated circuits). However, the scalability of this approach is a longstanding challenge as these components must be aligned onto individual fiber f...
Preprint
Varying only the in-plane or out-of-plane dimensions of nanostructures produces a wide range of colourful elements in metasurfaces and thin films. However, achieving shades of grey and control of colour saturation remains challenging. Here, we introduce a hybrid approach to colour generation based on the tuning of nanostructure geometry in all thre...
Article
Full-text available
Dielectric nanostructures are the basic building blocks for photonic metasurfaces exhibiting designer optical responses. As their optical responses are non-intuitive, design procedures often consider only primitive geometries such as circles, ellipses, and rectangles. Despite these simplified geometries, achieving a target response still requires t...
Preprint
Full-text available
We develop a single-layer waveguide surface grating structure to vertically couple near infrared (NIR) light at ~1.55 um wavelength from a large area (~100 um length scale) Si waveguide on a Silicon-On-Insulator (SOI) substrates to free-space for high-power laser applications. Our design approach is based on the optimization of local emission angle...
Preprint
Full-text available
Four-dimensional (4D) printing of shape memory polymer (SMP) imparts time responsive properties to 3D structures. Here, we explore 4D printing of a SMP in the submicron length scale, extending its applications to nanophononics. We report a new SMP photoresist based on Vero Clear achieving print features at a resolution of ~300 nm half pitch using t...
Article
Full-text available
Structural colors traditionally refer to colors arising from the interaction of light with structures with periodicities on the order of the wavelength. Recently, the definition has been broadened to include colors arising from individual resonators that can be subwavelength in dimension, e.g., plasmonic and dielectric nanoantennas. For instance, d...
Article
Diffractive optical elements (DOEs) are widely applied as compact solutions to generate desired optical patterns in the far field by wavefront shaping. They consist of microscopic structures of varying heights to control the phase of either reflected or transmitted light. However, traditional methods to achieve varying thickness of structures for D...
Article
Simultaneous and uniform actuation of multiple microrotors with easy fabrication method has been gathering significant attention in the field of precise microfluidic manipulation. In this work, the use of a piezoelectric vibration stage is presented to achieve the tunable acoustic vibration‐induced actuation of multiple microrotors fabricated by tw...
Article
Camouflage is critical for many living organisms to survive in the natural world and has stimulated the applications, such as optical cloaking and military affairs. However, most applications adopt crypsis-type camouflage that prevents the organisms from being detected by matching the environment, which is challenging to realize large angle-of-view...
Article
Full-text available
The direct patterning of colors using the bombardment of a focused beam of electrons onto a thin-film stack consisting of polymethyl methacrylate (PMMA) coated with a thin nickel film is demonstrated. This direct electron-beam color printing (DECP) approach creates variations in the height of a Fabry-Perot (FP) cavity, resulting directly in a color...
Article
Electron-beam lithography is widely applied in nanofabrication due to its high resolution. However, it suffers from low throughput due to its patterning process. All the pixels within a pattern's boundary are needed to be scanned for patterning, which is inefficient for a large area closed polygon structure. Introducing an additional step to perfor...
Article
Full-text available
Metasurfaces are planarized and miniaturized versions of conventional optical elements. Subwavelength‐thick single‐layer metalenses have diffraction limited resolution for on‐axis imaging but relatively low resolution for off‐axis imaging due to off‐axial aberrations. The aberrations of planar single‐layer metalenses have been corrected by patterni...
Article
Full-text available
We present results on colors of metal disk arrays viewed under a darkfield microscope and show that the darkfield colors can be manipulated independently of the brightfield colors. We investigate the appearance of colors as disks are clustered to form a new array with double the pitch and a basis of four disks. These structures of aluminum disks on...
Article
Full-text available
The generation of anti-Stokes emission through lanthanide-doped upconversion nanoparticles is of great importance for technological applications in energy harvesting, bioimaging and optical cryptography1,2,3. However, the weak absorption and long radiative lifetimes of upconversion nanoparticles may significantly limit their use in imaging and labe...
Article
Full-text available
Materials made by directed self‐assembly of colloids can exhibit a rich spectrum of optical phenomena, including photonic bandgaps, coherent scattering, collective plasmonic resonance, and wave guiding. The assembly of colloidal particles with spatial selectivity is critical for studying these phenomena and for practical device fabrication. While t...
Article
Plasmonic color generation is a promising field of study that have the potential to produce paradigm-shifts in display and printing technologies. To produce vibrant colors, plasmonic surfaces decorated with complex corrugated or protruding structures have been the commonly adopted strategy for saturated structural color generation. However, it is p...
Article
Full-text available
Devices with locally-addressable and dynamically tunable optical properties underpin emerging technologies such as high-resolution reflective displays and dynamic holography. The optical properties of metals such as Y and Mg can be reversibly switched by hydrogen loading, and hydrogen-switched mirrors and plasmonic devices have been realized, but c...
Article
Full-text available
Metasurfaces as artificially nanostructured interfaces hold significant potential for multi-functionality, which may play a pivotal role in the next-generation compact nano-devices. The majority of multi-tasked metasurfaces encode or encrypt multi-information either into the carefully tailored metasurfaces or in pre-set complex incident beam arrays...
Article
Although Si acts as an electrical semiconductor, it has properties of an optical dielectric. Here, we revisit the behavior of Si as a plasmonic metal. This behavior was previously shown to arise from strong interband transitions that lead to negative permittivity of Si across the ultra-violet spectral range. However, so far, few have studied the pl...