With the development of holography technique and nano-superfinishing technique, holography grating has being used into the spectrometer. To overcome some drawbacks of optical system for traditional plane and concave grating typed spectrometer, a splitting-light optical system for spectrometer based on volume phase holographic transmission (VPHT) grating is designed and developed in this paper. Meanwhile, the principle of VPHT grating is introduced by using the coupled-wave theory, and the relationship between the diffraction efficiency of the VPHT and the grating depth and the irradiation wavelength are simulated by means of MATLAB numerical computing method. In order to validate this splitting-light optical system, the experiment of measuring spectral resolution is performed and the spectral resolution reached 2nm, a calibration equation between the diffraction wavelengths and the shift of the corresponding wavelengths is obtained by using polynomial fitting algorithm. The experimental results demonstrate that the design of the splitting-light optical system for spectrometer based on VPHT grating is feasible.
Photoacoustic spectroscopy (PAS) is a hybrid, well-established and promising detection technique that has widely applied into a lot of fields such as bio-medical, material and environment monitoring etc. PAS has high contrast and resolution because of combining the advantages of the pure-optical and the pure-acoustic. In this paper, a photoacoustic experiment of glucose solution induced by 532nm pumped Nd:YAG tunable pulsed laser with repetition rate of 20Hz and pulse width of 10ns is performed. The time-resolved photoacoustic signals of glucose solution induced by pulsed laser in the average time of 512 are obtained. And the photoacoustic experiments of different concentrations of glucose solutions and different wavelengths of pulsed laser are carried out in this paper. Experimental results demonstrate that the bipolar sine-wave profiles for the time-resolved photoacoustic signal of glucose solution are in good agreement with the past reported literatures. And the different absorbing coefficients of glucose solution can be gotten according to the slope of the first part of the time-resolved photoacoustic signals. In addition, the different acoustic velocities of glucose solution can also be gotten according to the shift change of the time-resolved photoacoustic peak values. Research results illustrate that the characteristic wavelengths, different optical and acoustic properties of glucose solution can be interpreted by the time-resolved and peak-to-peak photoacoustic signals induced by the pulsed laser.
Since the water resource is being seriously polluted with the development of the human society, the monitoring of the
available water resource is an impending task. The concentration of the dissolved organic matter, oxygen and inorganic
salt in water can be checked by means of some methods, e.g. electrolysis, electrochemical method, colorimetry. But
because some drawbacks are existed in these methods, the laser-induced fluorescence (LIF) spectrophotometry method is
adopted into this paper. And a novel LIF spectrophotometer for water quality monitor (WQM) is designed. In this WQM,
the 3rd harmonic of the Q switched Nd:YAG laser is used as the induced fluorescence light-source. And for the
splitting-light system of the spectrophotometer for WQM, in order to improve the resolution and light-passing efficiency,
a novel volume holography transmissive(VHT) grating is used as the diffraction grating instead of the plane or
holography grating. Meanwhile, the linear CCD with combined data acquisition (DAQ) card is used as the fluorescence
spectral detection system and virtual instrument (VI) technology based on LabVIEW is used to control the spectral
acquisition and analysis. Experimental results show that the spatial resolution of the novel spectrophotometer for WQM
is improved, its resolution can reach 2nm. And the checking accuracy of this WQM is higher than others. Therefore, the
novel LIF spectrophotometer for WQM has the potential value in the water quality monitoring and biochemical
application.
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