In this paper, we propose temperature sensing method by using optical beating. When temperature changes, a peak wavelength of the sensing laser varies slightly. However, with limitation of the optical spectrum analyzer’s (OSA) spectral resolution (sub-nm), it is hard to measure the exact quantity of the wavelength variation. Therefore, we used electrical spectrum analyzer (ESA) and two lasers to obtain the wavelength shift. We used DFB-LD (distributed feedback laser diode) and TLS (tunable laser source) to get beating signal. Each of laser has 1550 nm of wavelength, -20 dBm of intensity and 108 of Q factor. We varied temperature by 0.1 °C from 17.4 °C to 18.4 °C using TEC (temperature controller). We observed 0.01 nm/°C of wavelength change through OSA and 9.5 GHz/°C of beating frequency change through ESA. With this result, we verified that we can measure relative temperature change with having ultra-fine resolution of 9.5×10-7 °C theoretically for the ESA resolution bandwidth of 1 kHz. This detecting ability can be applied to highly sensitive temperature sensor.
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.
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.
Position-sensitive photomultiplier tubes (PSPMTs) in array are used as gamma ray position detector. Each PMT converts the light of wide spectrum range (100 nm ~ 2500 nm) to electrical signal with amplification. Because detection system size is determined by the number of output channels in the PSPMTs, resistive network has been used for reducing the number of output channels. The photo-generated current is distributed to the four output current pulses according to a ratio by resistance values of resistive network. The detected positions are estimated by the peak value of the distributed current pulses. However, due to parasitic capacitance of PSPMTs in parallel with resistor in the resistive network, the time constants should be considered. When the duration of current pulse is not long enough, peak value of distributed pulses is reduced and detected position error is increased. In this paper, we analyzed the detected position error in the resistive network and variation of time constant according to the input position of the PSPMTs.
Surface-enhanced Raman scattering (SERS) has attracted considerable attention for chemical and biological agent detection through
the amplification of electromagnetic fields from localized surface plasmon resonance on a metal nanostructure. The fabrication of
metal nanostructure is the key issue for applications of SERS substrate. Particularly, well-ordered noble metal nanodot array can be
reproducibly fabricated using anodic aluminum oxide layer with uniform channels of nanometer dimensions. In this study, we report
the fabrication of Ag nanodot array on indium-tin-oxide (ITO) glass via the nanoporous alumina mask with through-holes and the
utilizing the array as a substrate for SERS application. Ag nanodot array with 55 nm diameter was fabricated in periodic pattern with
separation distance of 105 nm as a replica of the alumina mask. Optical property of Methylene Blue adsorption on Ag nanodot array
was examined by Raman spectroscopy. These results suggest that Ag nanodot array might be useful as a SERS platform for the future
application in sensitive detection of chemical materials.
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