Perforated periodic nanostructures (i.e. nanohole arrays) have become of great alternatives for transmissive structural coloration due to high transmission efficiency and high sensitivity upon incident angles. However, structural colors of conventional periodic nanostructures inevitably exhibit a substantial color-crosstalk due to the multiple resonances. Our previous work (M.-S. Ahn et al., nanoscale) had already reported that the complementary plasmonic structures (CPS) effectively attenuate the high-order resonances, and thus improve color-purity in the range from VIS (red) to NIR.
In this work, we successfully demonstrated transmissive structural coloration with high color-purity in fully visible ranges by using inverted CPS (iCPS) of aluminum (Al) nanoholes and nanodisks. Unlike previous Ag CPS, the Al iCPS features inverted configuration of suspended nanoholes and buried nanodisks by high refractive index (polyurethane acrylate; PUA) substrate, which blue-shifts the resonances of Al nanoholes and redshifts the extinction dip of Al nanodisks. As a result, carefully engineered extinction dip effectively suppresses the first-order resonance of Al nanoholes, and thus iCPS exhibit a pure visible-coloration with a single resonance, depending on the incident angles.
iCPS were nanofabricated by UV nanoimprinting lithography (UV-NIL) and thermal evaporation of aluminum, which enables uniform nanopattering with inch scale. Polyurethane acrylate (PUA) was used for a substrate due to its high refractive index and UV-curable property. After the replication of nanohole patterns into PUA, aluminum was evaporated on PUA nanohole substrate. Then the Al nanoholes are formed on top surface of PUA and Al nanodisks are buried in PUA nanohole. Structural coloration of iCPS provides a new direction for a tunable optical filter that highly requires tunability and selectivity.
Surface plasmon resonance (SPR) has been actively researched for sensor applications. Based on the subwavelength scale enhancement of light field and its sensitivity to refractive index, SPR can be used for surface enhanced Raman spectroscopy and various bio and chemical sensors. This talk will provide comparative overview of the potentials of SPR for optical sensors and its practical limitations in implementation.
In this invited paper, we glance at the history of plasmonic sensors and provide the optimization study of representative
plasmonic sensors such as surface plasmon resonance (SPR) sensors, localized SPR sensors, and fiber grating SPR
sensors. The key variables of specific plasmonic sensors are numerically examined and compared. Furthermore, we
discuss the recent developments and prospect on various plasmonic sensors.
We propose faced folded rods (FFR) as nano-antenna for light emissions. This FFR structure, which is composed of two
folded gold rods, shows two different field enhancement modes depending on the polarization direction of feeding light.
Under the incidence of x-polarized light, double hot spots are observed at gaps due to capacitive coupling between rods.
Meanwhile, when y-polarized light is applied to this geometry, a single hot spot is achieved at the center of the structure
which is due to the superposition of half-wavelength dipole resonance occurring at each folded rod. Strong resonance of
several vertices, which is predicted to be 100 of electric field enhancement factor in FFRs, can be achieved for sensitive
bio-molecular detection. Thus, we can manipulate the number and position of desired hot spots by way of controlling the
polarization state of light. Since we can obtain up to four different hot spot areas in nano-meter scale, multiplexed biosensing
can be possible using FFRs as the nano-antenna. To understand the physical mechanism behind the pair type of
folded rods, a single folded rod is first simulated as a basic elementary structure and compared with the pair structure.
Then, this FFR structure is fabricated with an electron beam evaporator and the focused ion beam lithography. The
scattered light intensity is captured by a CCD camera and compared with the simulation data.
We review recent advances in the plasmonic sensors associated with chemical and biological sensor system and
introduce their structural design method for enhancement of sensing performance such as detection limits, sensitivity,
and dynamic range, relative to the commercial systems. In addition, the effect of structural parameters of surface
plasmon resonance based sensors with transmission or reflection-type configuration is discussed. We also discuss the
optimal condition of the sensors with nano-structures as well as flat metallic layer structures for practical sensing and
provide the methods for improving sensing capability.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.