Liliana Tjahjana

Deep subwavelength fourfold rotationally symmetric split-ring-resonator metamaterials for highly sensitive and robust biosensing platform

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 (~λ/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.

Direct patterning of high density sub-15 nm gold dot arrays using ultrahigh contrast electron beam lithography process on positive tone resist

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.

Large contrast enhancement by sonication assisted cold development process for low dose and ultrahigh resolution patterning on ZEP520A positive tone resist

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.

Demonstration of low-loss on-chip integrated plasmonic waveguide based on simple fabrication steps on silicon-on-insulator platform

We report the experimental realization of a robust silicon-based plasmonic waveguide structure which can theoretically provide sub-wavelength confinement for Ex- and Ey-polarized surface plasmon polariton modes. Our waveguides exhibit propagation loss as low as 0.2 dB/μm with ∼50% coupling efficiency.

Sub-10-nm Size and Sub-40-nm Pitch Metal Dot Patterning for Low-Cost Bit Patterned Media Application

This paper presents the capability of sonicated cold development process for sub-40-nm pitch metal dots patterning with potentially ~100 times shorter writing time, where lift-off pattern transfer of ~10-nm-sized metal dots at pitch as short as ~34 nm from 110-nm-thick positive-tone resist is demonstrated with good repeatability. Strategies to achieve sub-30-nm pitch are also discussed based on overlay nanofabrication approaches, which we believe could pave the way toward cost-effective 1 Tbit/in 2 bit-patterned-media patterning.

Numerical and experimental studies of coupling-induced phase shift in resonator and interferometric integrated optics devices

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 193 nm Deep UV (DUV) lithography in silicon-on-insulator (SOI) technology.

The role of cold sonicated development scenarios for achieving ultradense and high aspect ratio for optical metamaterial applications

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).

Characteristics of defect modes in side-coupled and mutually coupled microresonator arrays

We present both theoretically and experimentally the existence of defect modes in side-coupled and mutually coupled microresonator arrays. The qualitative difference between the two types of defect modes is investigated. The Q factor of both defect modes for varying defect sizes is characterized, and an enhancement of ∼30× relative to individual loaded resonators is demonstrated. The defect modes are then compared with coupled resonator– induced transparency (CRIT), indicating that the defect modes based on side-coupled microresonator arrays are actually the extension of the CRIT resonance in two-resonator structures.

Low voltage sub-30nm dielectric and metal nanopatterning for plasmonic and metamaterial applications

We present a simple approach for sub-30nm dielectric and metal patterning based on low voltage electron beam lithography and standard lift-off process by using 42nm hydrogen silsesquioxane and 200nm ZEP resist.

Realization of coupled-resonator-induced transparency in silicon-on-insulator based ring-bus-ring geometry

We demonstrate coupled-resonator induced transparency by means of synergistic integration between the ring-bus-ring (RBR) configuration and the Mach-Zehnder interferometer (MZI) device, on silicon-on-insulator (SOI) material platform. Good agreement is obtained between experiment and the theory.