Papers by Keyword: Optical Sensor

Abstract: Development of optical chemical sensors for the detection of specific toxic chemicals at ultratrace levels and analysis of complex mixtures is crucial for new green and safe technologies [1, 2]. Metallic structures confined at the nanoscale acquire interesting properties such as strongly localizing E fields on their surfaces through Plasmonic Resonance under stimuli of light at certain wavelengths. This nanostructures are called plasmonic structures [3–5]. This effect is exploited to amplify the optical signal obtained by the molecules of interest, located near plasmonic structures [3, 6]. Purpose of the work is the development of innovative, easy to manufacture and cheap optical active layer consisting of Plasmonic Ag Nanoparticles on a Wide Band Gap semiconductor material such as Silicon Carbide to be used as substrate for Surface Enhanced Raman Scattering or for the fabrication of integrated optical sensor for remote chemical and biological applications. In this contest, the phenomenon of Ag thin film thermal dewetting on SiC substrate was implemented to develop a simple nanoparticles synthetic approach. Scanning Electron Microscopy confirmed the formation of Ag nanoparticles by thermal annealing of thin silver film. 4-MBA was used as probe molecule for SERS phenomenon investigation. The formation of a covalent bond between the silver nanostructures, acting as plasmonic "hot spots", and the species of interest enable its detection at very low concentrations, in the range of 10^-5 M or less, in both Raman and UV-Vis configurations.

Abstract: Two types of fiber optics, namely macro etched silica single mode fiber (SMF) and Fiber Bragg Grating (FBG) (Bragg wavelength of 1550 nm and 1554 nm) had been used to detect various types of honey samples, such as Apis Dorsata Honey, Trigona Honey and Capilano Australian Honey. To study the effect of exposure period in open environment at room temperature, all honey samples were exposed in open environment at room temperature from 2 to 10 days. In comparison with macro etched SMF and FBG (λ_B=1554 nm), the FBG (λ_B=1550 nm) portrays an excellent sensing properties with sensitivity and selectivity of 33.56 dB/RIU and 24.07 dB/RIU respectively. The output of this work concludes that the quality of honey based on optical output power reduces up to 0.35% as period of exposure to the open environment increased.

Abstract: A simple aqueous based synthesis technique at room temperature was performed for preparation manganese-doped zinc sulfide quantum dots. Under 4 eV excitation quantum dots show photoluminescence bands at 2.11 and 3.1 eV corresponded to Mn²⁺ and intrinsic ZnS emission respectively. ZnS quantum dots were used as the luminescent sensing element for methane detection in aqueous media. The luminescent sensor response occurs due to photoinduced electron transfer from QDs to methane molecule resulting in QD luminescence quenching.

Abstract: This paper presents the preparation of intensity-based plastic optical fiber (POF) sensor and its characteristics in the detection of ethanol concentration in water. Response of the sensor probes were analyzed for 0.02 to 1.00% v/v ethanol concentrations. The POF sensors have high sensitivity of detecting very low concentration of ethanol with 0.02% v/v ethanol in water. The reponsitivity of the polished U-shape sensor was 285 per percent of ethanol concentration. There are three distinct shapes of POF sensor probes that were developed: tapered U-shape; polished U-shape; and polished coil-shape. The POF were shaped into sensor probes by indirectly heating the POF at 80°C for several minutes and rapidly cooled in retaining the shapes. Tapering of POF was done using tensile tester with thermostatic chamber and other sensor probes were polished using fine abrasive for enhancing their sensitivities. The performance of the sensors was tested using He-Ne laser as the light source and the output spectra were analyzed using Ocean Optics spectrometer. The light intensity from the three sensors showed nonlinear response to ethanol concentrations from 0.02% - 1.00%. The POF sensor is more sensitive to 0.02%-0.10% ethanol concentration compared to 0.20% to 1.00%. At lower concentration, water tends to gradually absorb into POF polymer network and causes the fiber to swell more due to volume expansion. Higher ethanol concentration causes the swelling of the fiber to be eventually reduced and reached its detection limit.

Abstract: In order to safeguard China’s increasingly important sovereignty as well as our maritime rights and interests, monitoring of waters has been given more and more important importance. On such an occasion, electronic sensor and optical sensor appear as two applicable and useful means among all those space borne sensors which are widely used by many countries and regions thanks to their distinctive edges. In this paper, the key technology of target association and its pragmatic application prospect are further studied on the basis of the existing knowledge of electronic sensor and optical sensor.

Abstract: This paper presented a kind of design principle and method of the adaptive solar power supply system, and draw out the lighting system, hardware circuit and software flow charts of the system. Using MCU control solar lighting system to track the sun direction, the system collects the sun angle information through optical sensor in order to use solar energy in high efficiency. The device not only can provide reliable electric energy for the highway cameras, visibility detectors and other dispersion equipment, but has the advantages of low carbon, environmental protection, intelligence, etc.

Abstract: We investigate three conditions of optical fiber ring resonator. The tunable central light intensity of ring resonator can be realized through adjusting the dynamic variation of splitting ratio on the conditions of over-coupling, under-coupling and active-coupling. Especially in active-coupling case, we can get the large intensity at the resonant frequency with increase in splitting ratio in smaller range. This property can be used for sensing application and other fields.

Abstract: Welding defects result infailure of the machinery and other negative consequences. Therefore, they need to be detected as they appear to ensure efficient and high-quality production. There is a raising interest in the implementation of sensors to provide highly accurate and robust real-time welding process monitoring. This work describes the four most widely used techniques of welding process monitoring. These monitoring techniques are arc sensors, optical sensors, infrared sensors, and ultrasonic sensors. This work explains their principles of operation: discuss their advantages and limitations and give typical areas of application. Arc sensors, optical sensors, infrared sensors, and ultrasonic sensors are described in detail with the necessary figures and schemes in the first part of the present study. The physical background, the strengths and weaknesses, and real life examples of the sensing techniques are given in this part. The results of the research show that each sensing method has its specific features thatcan play an important role in certain welding applications. Arc sensors do not requireadditional equipment in the welding zone. Thisis why they can be used where operational space is limited. Optical sensors allow the observation of the weld pool behavior. Infrared sensors can create the temperature profile of the weld. Ultrasonic sensors usually have good resolution and can provide accurate data. This paper will help welding engineers to choose the optimal sensing equipment for aspecific industrial application.

Abstract: A high-performance microcavity sensor with a port connected with a waveguide directly is investigated numerically. With input light and output light transmitting in the same waveguide, we propose a robust coupling mechanism. For a circular microcavity with a diameter of 20μm and a refractive index of 1.45, our numerical results show that the coupled modes are excited and more than 5×10⁴ Q-factor is calculated from the transmission spectrum. Dramatically, the spectrum shows a fano-shape resonance at specific wavelength which is useful for high-precision optical sensing on the order of 10^-5.

Abstract: Localized surface plasmon resonance (LSPR) peak wavelength of nanostructures metallic materials, such as gold and silver, is very sensitive to the dielectric environment of the materials; hence widely used as sensors to detect various types of chemicals. In this study, high - yield gold nanoplates ca. 63% have been grown on the quartz substrate using the seed - mediated growth method. The grown gold nanoplates exhibit variety of shapes such as triangular, hexagonal, truncated hexagonal and flat rod. The LSPR spectrum of Au nanoplates sample has two absorption bands; centring at 543 nm and 710 nm, which are associated with transverse SPR (t-SPR) and longitudinal SPR (l-SPR) respectively. The intensities and peaks position of these two bands were found to linearly change with the concentration of boric acid solutions.