Fabry-Pérot干涉近红外光谱仪

文章主要从分光原理、加工技术和仪器性能3个方面介绍Axsun公司的Fabry-Pérot干涉近红外光谱仪     

Note: Higher resolution Brillouin spectroscopy by offset stabilization of a tandem Fabry-Pérot interferometer

A simple modification to a Sandercock-type tandem Fabry-Pérot interferometer is demonstrated. By adding an independent reference laser with temperature tunability, narrow Brillouin lines that are tens GHz shifted from the Rayleigh line can be recorded with much higher frequency resolution than in the original system.     

新型法布里-珀罗(Fabry-Pérot)腔传感结构

应用化学腐蚀和熔接技术对光纤端面进行腐蚀与熔接的方法,构建法布里-珀罗(F-P)腔,根据法布里-珀罗腔的干涉原理设计光纤传感结构,并应用紫外交联法在传感头固定化生物物质RNA,通过观测固定化前后端面SEM图像的对比与F-P腔干涉图谱的相位偏移,得出光纤端面RNA的固定化情况.     

Note: Optical fiber milled by focused ion beam and its application for Fabry-Pérot refractive index sensor

We introduce a highly compact fiber-optic Fabry-Pérot refractive index sensor integrated with a fluid channel that is fabricated directly near the tip of a 32 μm in diameter single-mode fiber taper. The focused ion beam technique is used to efficiently mill the microcavity from the fiber side and finely polish the end facets of the cavity with a high spatial resolution. It is found that a fringe visibility of over 15 dB can be achieved and that the sensor has a sensitivity of ~1731 nm/RIU (refractive index units) and a detection limit of ~5.78 × 10(-6) RIU. This miniature integrated all-in-fiber optofludic sensor may find use in minimal-invasive biomedical applications.     

Scanning Fabry-Pérot interferometer with largely tuneable free spectral range for high resolution spectroscopy of single quantum dots

We report on the implementation of a scanning Fabry-Pérot interferometer for photoluminescence spectroscopy investigation. We choose a conveniently small reflectivity of the two planar semitransparent mirrors which, in spite of a moderate cavity finesse, ensures a good mechanical stability over a long time. We also exploit the large tuneability of the cavity length (i.e., of the free spectral range) for changing the spectral resolution over two order of magnitude (from ~300 μeV to ~4 μeV in full width at half maximum). Such a characteristic easily allows to scan both sharp and broad luminescence bands. We test our Fabry-Pérot interferometer on sharp photoluminescence lines resulting from excitonic recombination in self-assembled GaAs quantum dots. We demonstrate the ability of our system to resolve linewidth as small as 4 μeV.     

Fabry-Pérot interferometer utilized for displacement measurement in a large measuring range

The optical configuration of a Fabry-Pe?rot interferometer is uncomplicated. This has already been applied in different measurement systems. For the displacement measurement with the Fabry-Pe?rot interferometer, the result is significantly influenced by the tilt angles of the measurement mirror in the interferometer. Hence, only for the rather small measuring range, the Fabry-Pe?rot interferometer is available. The goal of this investigation is to enhance the measuring range of Fabry-Pe?rot interferometer by compensating the tilt angles. To verify the measuring characteristic of the self-developed Fabry-Pe?rot interferometer, some comparison measurements with a reference standard have been performed. The maximum deviation of comparison experiments is less than 0.3?μm in the traveling range of 30 mm. The experimental results show that the Fabry-Pe?rot interferometer is highly stable, insensitive to environment effects, and can meet the measuring requirement of the submicrometer order.     

Linear stability analysis of Rayleigh-Bénard convection of cold water near its density maximum in a vertically heated annular container

In order to understand the onset of Rayleigh-Bénard convection of cold water near its density maximum in a vertical annular container heated from below and cooled from above, the instability of the static diffusive state was investigated by linear stability analysis. Two kinds of thermal boundary conditions, perfect insulating and conducting sidewalls, were used. The aspect ratio and radius ratio of the annular container varied from 0.5 to 4.5 and 0.1 to 0.8, respectively. Results indicate that the critical Rayleigh number and the critical wave number increase with the increase of density inversion parameter. There are some new flow modes with large azimuthal wave number near the convection onset for cold water with density maximum, which are not observed in Rayleigh-Bénard convection of the Boussinesq fluids. The stratified flow phenomenon in cold water with density maximum is certified. The larger the density inversion parameter is, the more obvious the stratified flow phenomenon becomes. With the increase of the aspect ratio, the critical Rayleigh number decreases, but the critical wave number increases. However, with the increase of the radius ratio, both the critical Rayleigh number and the critical wave number increase continuously. Furthermore, the effect of thermal boundary conditions at the sidewalls on the convection stability is also validated.