Two-dimensional (2-D) metal nanodot arrays (NDAs) have been attracting significant attention for use in biological and chemical sensing applications. The unique optical properties of the metal NDAs originate from their localized surface plasmon resonance (LSPR). Nanofabrication methods that use nanoporous alumina masks (NAMs) have been widely used to produce metal NDAs. We report a fabrication technique for a 2-D Ag NDA and its utilization as a platform for LSPR-based sensing applications. A well-ordered Ag NDA of ∼70-nm diameter, arranged in a periodic pattern of 105 nm, was fabricated on an indium tin oxide (ITO) glass substrate using an NAM as an evaporation mask. The LSPR of the Ag NDA on the ITO glass was investigated using ultraviolet–visible spectroscopy. The LSPR wavelength shifts caused by the variations in the quantity of methylene blue adsorbed on the Ag NDA were examined. The results of this study suggest that the Ag NDA prepared using NAM can be used as a chemical sensor platform.
A surface plasmon resonance (SPR) sensor hybridized with self-assembled metallic nanoparticles is proposed and experimentally demonstrated. The measured sensitivity of the proposed SPR sensor is 110.77 deg/RIU, while that of a conventional SPR sensor is 84.75 deg/RIU. The enhanced sensitivity is attributed to the strong localized surface plasmons and the increased surface interaction area by the nanoparticles. Angle variation measurement, which is an easy detection method using bulk optics, is possible with this structure because a supplementary metallic thin film layer on the nanoparticles leads to utilization of the sensitive variation of the strong localized field by the change of the refractive index. Furthermore, the proposed structure can be fabricated with a very simple three-step nonlithographic process.
In this paper, we propose a bio-sensing method using optical heterodyne detection for ultra-high Q micro-disk laser (MDL) sensor platform. MDL structure with ultra-high Q-factor (> 108) has advantage in detecting a small variation of the lasing wavelength. For example, when a single molecule is attached to sidewall of MDL, the lasing wavelength is changed by sub-pm. Optical spectrum analyzer (OSA) has limits to detect sub-pm variation in the resonant wavelength because of the spectral resolution. In order to overcome this limitation, we used a heterodyne detection method which needs two MDLs with the same characteristics.
The noble metal nanostructure has attracted significant attention because of their potential applications as sensitive sensor platform blocks for biological and chemical sensing. The unique optical property of the metal nanostructure is originated from localized surface plasmon resonance (LSPR). The fabrication of metal nanostructure is a key issue for sensor applications of LSPR. In this paper, fabrication technique of two-dimensional Ag nanodot array on an indium tin oxide (ITO) glass substrate via the nanoporous alumina mask and the utilization as a platform for LSPR chemical sensor was studied. Well-ordered Ag nanodot array with approximately 65 nm diameter in periodic pattern of 105 nm was fabricated using the nanoporous alumina with through-holes as an evaporation mask. The LSPR of Ag nanodot array on ITO glass substrate was investigated by UV-vis spectroscopy. The LSPR wavelength-shifts owing to the concentration variances of Methylene Blue (MB) adsorbed on Ag nanodot arrays were examined for application of chemical sensor.
In this paper, an effective quality-factor is analyzed for asymmetric Mach-Zehnder interferometer (AMZI) with ring resonator sensor. The device is designed with AMZI to interference with the optical input of the ring resonator based on silica semiconductor process. The design of device satisfy a critical resonance at out of phase condition through asymmetric power split ratio. According to operation principle of Mach-Zehnder interferometer, the critical resonance occurs when the power passing through asymmetric arm is in a range of ring resonator power variation. Our simulation shows that the Q-factor of the device is enhanced from 1161.9 to 5342.5 if a RR is coupled to an arm of AMZI.
In this paper, surface plasmon resonance triangular ring resonator (SPR-TRR) Vernier structure based on InP is simulated for index variation from 1.33 to 1.35. Sensing area of SPR-TRR is achieved to make an ultra-compact SPR mirror by deposition of Au film layer which is designed to deposit on vertex of TRR. The possibility of mass production is shown by a deposition of SPR mirror on the triangular ring resonator (TRR). Also, the sensitivity enhancement of an envelope signal for Vernier effect is confirmed by FDTD simulation compared to SPR-TRR. As simulation results, the sensitivity is enhanced 20 nm / RIU to 480 nm / RIU. Thus, SPR-TRR Vernier structure is used for a biosensor to enhance the sensitivity of biosensor.
In this paper, we have theoretically analyzed using a finite-difference time domain (FDTD) methods and realized a
high sensitive triangular ring resonator sensor based on the total internal reflection (TIR) mirror with a thin metal film
for surface plasmon resonance (SPR) phenomenon. One of advantages is a high sensitivity with large phase variation at
TIR mirror facet with SPR. Previously, the sensing region of the general ring resonator sensor is located on the cladding
region or upper core region. However, the triangular ring resonator has a very high sensitivity using the sensing region of
the TIR mirror facet, because the length of the evanescent field at TIR mirror is longer than the evanescent field length at
the cladding region. Another is a high Q-factor by the round-trip loss compensation through an active medium in the
waveguide. Proposed sensor also has an integrated light source using an InP-based semiconductor optical amplifier. The
sensitivity of triangular ring resonator with SPR is extremely enhanced by large phase shift at TIR mirror facet on SPR.
Optimized metal thickness is a 33.4 nm at the SPR angle of 22.92 degree. The simulation result of the sensitivity for the
triangular ring resonator sensor with SPR is 4.2×104 nm/RIU using by FDTD method. To measure the biosensor, we used
an antigen/antibody reaction.
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