Yati Tobing - Academia.edu (original) (raw)

Papers by Yati Tobing

International Journal of Science and Research (IJSR), Jul 5, 2017

This research aims to examine in depth of treatment pregnancy and childbirth-tribes Walsa Keerom ... more This research aims to examine in depth of treatment pregnancy and childbirth-tribes Walsa Keerom Regency waris District in the province of Papua. This study uses qualitative methods with an ethnographic approach. Informants in this study is pregnant and the mother of childbirth (mother descended from Walsa), families of pregnant women and mothers parturition (husband or parents of pregnant women and mothers parturition), midwives, herbalists and other indigenous tribes of Walsa. Data collection is done through the methods of the Focus Group Discussion, in-depth interviews, observation and documentation and passive participation. The results showed that the implementation of the care of expectant mothers tribe Walsa done by maintaining physical health, family support was given from the beginning of pregnancy of the mother, intertwined relationship between pregnant women with families, relatives and neighbors. Types of pregnancy examination is done traditionally by utilizing the services of a shaman at age 2-9 months of pregnancy. The women of the tribe Walsa also utilizes the services of midwives to checked her pregnancy gestational age when stepping on the moon. Diet pregnant women the same as his family's diet with main menu papeda (original food of Papuanes) and vegetable consumed in limited. There are culture specific food abstinence during pregnancy. Help and handling labor performed by the mother alone or shaman and assisted by relatives or neighbors. Place of delivery is done in the kitchen, the back room or hut specially made the husband behind the House. While Labor's husband is not allowed to accompany his wife to 3-4 weeks after the baby is born. The position used when maternity was the position of the squat. The cutting of the umbilical cord after the placenta (her brother) was born using a razor blade and placenta treatment done by burying it in the ground and adjusted the position of the House in the country

Nanophotonics

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...

Advanced Optical Materials

Strong interactions between surface plasmons in ultra-compact nanocavities and excitons in two di... more Strong interactions between surface plasmons in ultra-compact nanocavities and excitons in two dimensional materials have attracted wide interests for its prospective realization of polariton devices at room temperature. Here, a continuous transition from weak coupling to strong coupling between excitons in MoS2 monolayer and highly localized plasmons in ultracompact nanoantenna is proposed. The nanoantenna is assembled by a silver nanocube positioned over a gold film and separated by a dielectric spacer layer. A 1570-fold enhancement in the photoluminescence is observed at weak coupling regime in hybrid nanocavities with thick spacer layers. The interaction between excitons and plasmons is then directly prompted to strong coupling regime by shrinking down the thickness of spacer layer. Room temperature formation of polaritons with Rabi splitting up to 190 meV is observed with a fair polariton loss around 165 meV. Numerical calculations quantify the relation between coupling strength, local density of states and spacer thickness, and reveal the transition between weak coupling and strong coupling in nanocavities. The findings in this work offer a guideline for feasible designs of plasmon-exciton interaction systems with gap plasmonic cavities.

Nanoscale

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.

Scientific reports, Jan 24, 2018

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...

ACS Photonics

Since optical gain was observed from colloidal quantum dots (CQDs), research on CQD lasing has be... more Since optical gain was observed from colloidal quantum dots (CQDs), research on CQD lasing has been focused on the CQDs themselves as gain materials and their coupling with optical resonators. Combining the advantages of a CQD gain medium and optical microcavity in a laser device is desirable. Here, we show concentric circular Bragg gratings intimately incorporating CdSe/CdZnS/ZnS gradient shell CQDs. Because of the strong circularly symmetric optical confinement in two dimensions, the output beam CQD-based circular grating distributed feedback laser is found to be highly spatially coherent and azimuthally polarized with a donut-like cross section. We also observe the strong modification of the photoluminescence spectrum by the grating structures, which is associated with modification of optical density of states. This effect confirmed the high quality of the resonator that we fabricated and the spectral overlap between the optical transitions of the emitter and resonance of the cavity. Single mode lasing has been achieved under a quasi-continuous pumping regime, while the position of the lasing mode can be conveniently tuned via adjusting the thickness of the CQD layer. Moreover, a unidirectional output beam can be observed as a bright circular spot on a screen without any collimation optics, presenting a direct proof of its high spatial coherence.

AIP Advances

We report detailed investigation of n-GaSb/n-InAsSb heterostructure photodetectors for infrared p... more We report detailed investigation of n-GaSb/n-InAsSb heterostructure photodetectors for infrared photodetection at different temperatures and biases. Our results show that the heterostructure photodetectors are capable of dual color photodetections at a fixed forward bias with its highest responsivity occurred at room temperature; With the decrease of the forward bias, a turning point, at which the photocurrent changes its direction, exist and the corresponding voltage values increases with the decrease of temperature; At all reverse biases, the photocurrents flow in the same direction but the maximum current occurs at about 205 K. A new model is proposed, which can well explain all the observations.

Scientific reports, Jan 8, 2017

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...

Scientific Reports, 2013

Metamaterials provide a good platform for biochemical sensing due to its strong field localizatio... more Metamaterials provide a good platform for biochemical sensing due to its strong field localization at nanoscale. In this work, we show that electric and magnetic resonant modes in split-ring-resonator (SRR) can be efficiently excited under unpolarized light illumination when the SRRs are arranged in fourfold rotationally symmetric lattice configuration. The fabrication and characterization of deep subwavelength (,l/15) gold-based SRR structures with resonator size as small as , 60 nm are reported with magnetic resonances in Vis-NIR spectrum range. The feasibility for sensing is demonstrated with refractive index sensitivity as high as , 636 nm/RIU.

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 ...

Coupling induced effects are higher order effects inherent in waveguide evanescent coupling that ... more Coupling induced effects are higher order effects inherent in waveguide evanescent coupling that are known to spectrally distort optical performances of integrated optics devices formed by coupled resonators. We present both numerical and experimental studies of coupling-induced phase shift in various basic integrated optics devices. Rigorous finite difference time domain simulations and systematic experimental characterizations of different basic structures were conducted for more accurate parameter extraction, where it can be observed that coupling induced wave vector may change sign at the increasing gap separation. The devices characterized in this work were fabricated by CMOS-process 193nm Deep UV (DUV) lithography in silicon-on-insulator (SOI) technology.

We show theoretically and demonstrate experimentally that box-like response can be obtained using... more We show theoretically and demonstrate experimentally that box-like response can be obtained using 2D arrays of microring resonator. The box-like response is manifested from the complementary photonic bandgap properties of the column and row configurations. The observed sidelobe suppression is ~10dB, while the usable bandwidth can be as high as 500 to 750 GHz.

We experimentally demonstrate coupled-resonator-inducedtransparency (CRIT) phenomenon in ring-bus... more We experimentally demonstrate coupled-resonator-inducedtransparency (CRIT) phenomenon in ring-bus-ring (RBR) geometry synergistically integrated with Mach-Zehnder interferometer (MZI). The RBR consists of two detuned resonators indirectly coupled through a center bus waveguide. The transparency is obtained by increasing the light intercavity interaction through tailoring the RBR phase response while ensuring balanced MZI operation. In this work, a CRIT resonance with a quality factor of ~18,000 is demonstrated with cavity size detuning of ~0.035% and power coupling of ~60%, which are in good agreement with the theory.

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.

We show experimentally the existence of defect modes in mutually coupled microring resonator arra... more We show experimentally the existence of defect modes in mutually coupled microring resonator arrays fabricated in silicon-on-insulator technology. The movements of donor-like and acceptor-like modes are demonstrated for various defect lengths, in good agreement with earlier theoretical prediction.

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

We experimentally study the effects of the coupling-induced phase shift (CIPS) in silicon-on-insu... more We experimentally study the effects of the coupling-induced phase shift (CIPS) in silicon-on-insulator microring-coupled Mach-Zehnder interferometer (MZI) devices for the flat-top filter application. Excellent agreement is obtained between the theoretical modeling and the experiment. It is demonstrated that width offset of the uncoupled MZI arm can compensate the CIPS and approximate a box-like filter with only 0.02% deviation from its ideal requirement.