Achieving high transmission of light through a highly conductive structure implemented on a semic... more Achieving high transmission of light through a highly conductive structure implemented on a semiconductor remains a challenge in optoelectronics as the transmission is inevitably deteriorated by absorption and Fresnel reflection. There have been numerous efforts to design structures with near-unity transmission, yet they are typically constrained by a trade-off between conductivity and optical transmission. To address this problem, we propose and demonstrate a transmission mechanism enabled by a monolithic GaSb subwavelength grating integrated with Au stripes (metalMHCG). Near-unity transmission of polarized light is achieved by inducing low-quality factor resonance in the air gaps between the semiconductor grating stripes, which eliminates light absorption and reflection by the metal. Our numerical simulation shows 97% transmission of transverse magnetic polarized light and sheet resistance of 2.2 ΩSq−1. The metalMHCG structure was realized via multiple nanopatterning and dry etchi...
We demonstrate a high resolution electrochemical deposition technique to realize dimers with high... more We demonstrate a high resolution electrochemical deposition technique to realize dimers with high aspect ratio nanometric gaps suitable for sensing.
Dual-band photodetection in mid- and near-wave infrared spectral bands is of scientific interest ... more Dual-band photodetection in mid- and near-wave infrared spectral bands is of scientific interest and technological importance. Most of the state-of-the-art mid-infrared photodetectors normally operate at low temperature and/or suffer from toxicity and high cost due to limitations of material properties and device structures. The capability of surface plasmons in confining electromagnetic waves into extremely small volume provides an opportunity for improving the performance for room temperature operation. Here, we report an n-InAsSb/n-GaSb heterostructure photodiode integrated with plasmonic two-dimensional subwavelength hole array (2DSHA) for room temperature two band photodetection. We demonstrate that with a properly designed 2DSHA, room temperature detectivities of the heterostructure device can be enhanced to ~1.4 × 109 Jones and ~1.5 × 1011 Jones for the two bands peaked at 3.4 μm and 1.7 μm, respectively. In addition, we study the photocurrent enhancement in both photoconduct...
Optics-based sensing platform working under unpolarized light illumination is of practical import... more Optics-based sensing platform working under unpolarized light illumination is of practical importance in the sensing applications. For this reason, sensing platforms based on localized surface plasmons are preferred to their integrated optics counterparts for their simple mode excitation and inexpensive implementation. However, their optical response under unpolarized light excitation is typically weak due to their strong polarization dependence. Herein, the role of rotational symmetry for realizing robust sensing platform exhibiting strong optical contrast and high sensitivity is explored. Specifically, gammadion and star-shaped gold nanostructures with different internal and external rotational symmetries are fabricated and studied in detail, from which their mode characteristics are demonstrated as superposition of their constituent longitudinal plasmons that are in conductive coupling with each other. We demonstrate that introducing and increasing internal rotational symmetry wo...
ABSTRACT We present a systematic study of different sonicated cold development scenarios for the ... more ABSTRACT We present a systematic study of different sonicated cold development scenarios for the purpose of achieving high density optical metamaterial. High aspect ratio sub-15-nm dots at pitch as small as 40 nm are successfully demonstrated for 110-nm thick resist at low exposure dose. Some of the key results include sub-15-nm gold nanodots at 40-nm pitch and high density optical metamaterial (with only ∼30nm separation between two adjacent resonators).
Ultrahigh density nanostructure arrays with controlled size and position have promised a variety ... more Ultrahigh density nanostructure arrays with controlled size and position have promised a variety of potential applications. However, their practical realization is often hindered by the amount of resources required for large-scale fabrication. Using an ultrahigh contrast electron beam lithography process, we show ultrahigh resolution and high aspect ratio patterning capability which can be done at an exposure dose lower than 100 μC cm(-2). In particular, the high aspect ratio of dot arrays on 110 nm thick resist is confirmed by a standard lift-off process of 20 nm thick gold nanodots at sub-15 nm feature size and 40 nm pitch. The smallest gold nanodot size from our experiment is 11 nm.
A material that has both negative permittivity and permeability is termed as left-handed material... more A material that has both negative permittivity and permeability is termed as left-handed material. The properties of Left Handed Material (LHM), such as negative refraction, have been simulated numerically by beam propagation method. The results are consistent with other works reported in the literature. It is shown that the Poynting vector and the phase velocity of the electromagnetic wave are indeed anti-parallel, confirming that the left-handed material does not violate the causality condition. It is conventional to simulate the phase restoring mechanism in a left-handed medium by showing (negative) refraction at an interface between an LHM and a conventional material. In this paper, we show for the first time, a simulation using BPM for the case of multiple-slit interference using Gaussian beam. The interference for two to three sources with different separations is used to show that the LHM can restore the phase and reverse the diffraction and interference effects.
Page 1. Experimental Verification of Finesse enhancement scheme in two-ring resonator system Land... more Page 1. Experimental Verification of Finesse enhancement scheme in two-ring resonator system Landobasa YM Tobinga, Desmond CS Lima, Pieter Dumonb, Roel Baetsb, and Mee-Koy Chin*a aNanyang Technological University ...
ABSTRACT The authors demonstrate a robust, low dose, high contrast, and ultrahigh resolution patt... more ABSTRACT The authors demonstrate a robust, low dose, high contrast, and ultrahigh resolution patterning process based on sonication assisted development of ZEP520A positive tone resist in both room and cold temperature. The contrast as high as γ ∼ 25 and γ ∼ 9.14 can readily be achieved in 6 °C and room temperature development, respectively, in diluted n-amyl acetate solution. The high contrast is demonstrated on 90 nm thick ZEP resist at 20 kV acceleration voltage, from which 20 nm thick titanium lift-off of 60 nm pitch lines and 50 nm pitch dots can be successfully achieved.
Light confining microresonators based on evanescent wave propagation and whispering gallery (WG) ... more Light confining microresonators based on evanescent wave propagation and whispering gallery (WG) modes have received much attention in the past decades, due to their conceptual similarity with their standing wave counterparts, improvements in fabrication technology, and their versatility in realizing various functions in telecommunications, sensing, measurement, and instrumentation. In this chapter the general concepts, design principles, and practical realizations of
Achieving high transmission of light through a highly conductive structure implemented on a semic... more Achieving high transmission of light through a highly conductive structure implemented on a semiconductor remains a challenge in optoelectronics as the transmission is inevitably deteriorated by absorption and Fresnel reflection. There have been numerous efforts to design structures with near-unity transmission, yet they are typically constrained by a trade-off between conductivity and optical transmission. To address this problem, we propose and demonstrate a transmission mechanism enabled by a monolithic GaSb subwavelength grating integrated with Au stripes (metalMHCG). Near-unity transmission of polarized light is achieved by inducing low-quality factor resonance in the air gaps between the semiconductor grating stripes, which eliminates light absorption and reflection by the metal. Our numerical simulation shows 97% transmission of transverse magnetic polarized light and sheet resistance of 2.2 ΩSq−1. The metalMHCG structure was realized via multiple nanopatterning and dry etchi...
We demonstrate a high resolution electrochemical deposition technique to realize dimers with high... more We demonstrate a high resolution electrochemical deposition technique to realize dimers with high aspect ratio nanometric gaps suitable for sensing.
Dual-band photodetection in mid- and near-wave infrared spectral bands is of scientific interest ... more Dual-band photodetection in mid- and near-wave infrared spectral bands is of scientific interest and technological importance. Most of the state-of-the-art mid-infrared photodetectors normally operate at low temperature and/or suffer from toxicity and high cost due to limitations of material properties and device structures. The capability of surface plasmons in confining electromagnetic waves into extremely small volume provides an opportunity for improving the performance for room temperature operation. Here, we report an n-InAsSb/n-GaSb heterostructure photodiode integrated with plasmonic two-dimensional subwavelength hole array (2DSHA) for room temperature two band photodetection. We demonstrate that with a properly designed 2DSHA, room temperature detectivities of the heterostructure device can be enhanced to ~1.4 × 109 Jones and ~1.5 × 1011 Jones for the two bands peaked at 3.4 μm and 1.7 μm, respectively. In addition, we study the photocurrent enhancement in both photoconduct...
Optics-based sensing platform working under unpolarized light illumination is of practical import... more Optics-based sensing platform working under unpolarized light illumination is of practical importance in the sensing applications. For this reason, sensing platforms based on localized surface plasmons are preferred to their integrated optics counterparts for their simple mode excitation and inexpensive implementation. However, their optical response under unpolarized light excitation is typically weak due to their strong polarization dependence. Herein, the role of rotational symmetry for realizing robust sensing platform exhibiting strong optical contrast and high sensitivity is explored. Specifically, gammadion and star-shaped gold nanostructures with different internal and external rotational symmetries are fabricated and studied in detail, from which their mode characteristics are demonstrated as superposition of their constituent longitudinal plasmons that are in conductive coupling with each other. We demonstrate that introducing and increasing internal rotational symmetry wo...
ABSTRACT We present a systematic study of different sonicated cold development scenarios for the ... more ABSTRACT We present a systematic study of different sonicated cold development scenarios for the purpose of achieving high density optical metamaterial. High aspect ratio sub-15-nm dots at pitch as small as 40 nm are successfully demonstrated for 110-nm thick resist at low exposure dose. Some of the key results include sub-15-nm gold nanodots at 40-nm pitch and high density optical metamaterial (with only ∼30nm separation between two adjacent resonators).
Ultrahigh density nanostructure arrays with controlled size and position have promised a variety ... more Ultrahigh density nanostructure arrays with controlled size and position have promised a variety of potential applications. However, their practical realization is often hindered by the amount of resources required for large-scale fabrication. Using an ultrahigh contrast electron beam lithography process, we show ultrahigh resolution and high aspect ratio patterning capability which can be done at an exposure dose lower than 100 μC cm(-2). In particular, the high aspect ratio of dot arrays on 110 nm thick resist is confirmed by a standard lift-off process of 20 nm thick gold nanodots at sub-15 nm feature size and 40 nm pitch. The smallest gold nanodot size from our experiment is 11 nm.
A material that has both negative permittivity and permeability is termed as left-handed material... more A material that has both negative permittivity and permeability is termed as left-handed material. The properties of Left Handed Material (LHM), such as negative refraction, have been simulated numerically by beam propagation method. The results are consistent with other works reported in the literature. It is shown that the Poynting vector and the phase velocity of the electromagnetic wave are indeed anti-parallel, confirming that the left-handed material does not violate the causality condition. It is conventional to simulate the phase restoring mechanism in a left-handed medium by showing (negative) refraction at an interface between an LHM and a conventional material. In this paper, we show for the first time, a simulation using BPM for the case of multiple-slit interference using Gaussian beam. The interference for two to three sources with different separations is used to show that the LHM can restore the phase and reverse the diffraction and interference effects.
Page 1. Experimental Verification of Finesse enhancement scheme in two-ring resonator system Land... more Page 1. Experimental Verification of Finesse enhancement scheme in two-ring resonator system Landobasa YM Tobinga, Desmond CS Lima, Pieter Dumonb, Roel Baetsb, and Mee-Koy Chin*a aNanyang Technological University ...
ABSTRACT The authors demonstrate a robust, low dose, high contrast, and ultrahigh resolution patt... more ABSTRACT The authors demonstrate a robust, low dose, high contrast, and ultrahigh resolution patterning process based on sonication assisted development of ZEP520A positive tone resist in both room and cold temperature. The contrast as high as γ ∼ 25 and γ ∼ 9.14 can readily be achieved in 6 °C and room temperature development, respectively, in diluted n-amyl acetate solution. The high contrast is demonstrated on 90 nm thick ZEP resist at 20 kV acceleration voltage, from which 20 nm thick titanium lift-off of 60 nm pitch lines and 50 nm pitch dots can be successfully achieved.
Light confining microresonators based on evanescent wave propagation and whispering gallery (WG) ... more Light confining microresonators based on evanescent wave propagation and whispering gallery (WG) modes have received much attention in the past decades, due to their conceptual similarity with their standing wave counterparts, improvements in fabrication technology, and their versatility in realizing various functions in telecommunications, sensing, measurement, and instrumentation. In this chapter the general concepts, design principles, and practical realizations of
Uploads
Papers by Yati Tobing