The temperature characteristics of near infrared surface plasmon resonance （SPR） sensors with Kretschmann configuration are studied theoretically and experimentally. The experimental results match with the numerical simulations in the temperature range from 10 ℃ to 40.℃. With the increase of temperature, the resonance angle for gas increases slightly, but that for aqueous solution decreases obviously. No matter the dielectric layer is gas or aqueous solution, the resonance peaks are both broadened.
This work demonstrated quantitatively that DSA （dansylamide） and apo CA （dezincified carbon anhydrase） interacted with each other in the presence of Zn2＋ （zinc ion）. The fluorescence emission of DSA in the presence of Zn2＋ and the intensity of fluorescence, which was proportional to the concentration of Zn2＋, could be used in the measurement of Zn2＋ concentration. Considering that Zn2＋ was the active center of enzymes like CA （carbon anhydrase）, two dezincification reagents were compared to ensure the validity of our method. A certain range concentration of Zn2＋ could be measured by the reaction product of apo CA, DSA and Zn2＋, where the measurement limitation was about 60 nmol/L. Interaction of CA with DSA was also studied with infrared spectrometry.
The mode theory is the main way to study the propagation characteristics of light in fiber so far,but it is not suitable for analysis of light in duct.By using ray-tracing method,the rotary propagation characteristics of light in multimode-single mode-multimode(MSM) fiber structures are analyzed in this paper.Firstly,the light ray in fiber can propagate around an inscribed circle,and the central axis of this fiber is the propagation axis.Secondly,the radius of the inscribed circle is decided by both incident angle and incident position,and its variation is between 0 and RM,where RM is the radius of the multimode fiber.Lastly,the bigger the ratio of core and cladding diameter is,the higher the propagation efficiency is.
The equivalent four-pole network model is used to simulate one-dimension longitudinal acoustic resonator with different buffer diameters and lengths, aiming to reach a theoretic model which is able to estimate the optimal buffer geometry. In experiments, the buffer volumes are decreased gradually by filling a set of aluminum rings with different inner diameters and lengths into the buffers to get the desired dimensions. The experimental results show that the average deviation of 1.1% is obtained between the experimental results and the theoretical simulation at the buffer length of 30 mm. Experiments show that the minimum background signal occurs when the buffer length is equal to a quarter of the acoustic wavelength (λ/4). The amplitude of the photoacoustic signal is barely influenced when dbuf>3dres. Considering that oversize of photoacoustic cell needs more measuring gas and more material, the buffer diameter can be deduced to dbuf≈3dres. Therefore, smaller photoacoustic cell is desirable.
A high-efficiency capillary-fiber optic probe is developed for measuring the concentration of trace elements. The optimal probe consists of an excitation fiber (incident fiber) and a ring of collection fibers which is made up of 6 fibers. Both simulation and experiment results show that the structure gives the higher coupling efficiency with a reasonable capillary diameter. The coupling efficiency of the probe is determined by the number and arrangement of the fibers, internal diameter and length of the fiber optic sensing probe, and the end reflectivity of the capillary. The concentra-tion of the carbonic anhydrase solution and dezincification reagents also affect the efficiency. A fluorescence efficiency of 2.4% is obtained in zinc detection experiment.
