A kind of particle size detecting sensor based on optical resonator
Technical field
The present invention relates to a kind of for detecting the concentration of particulate and the sensor of size in gas or liquid, to can be applicable in air haze and detecting and environmental protection and the biochemical analysis field such as microorganism detection in water.
Background technology
Micro-nano particle quality testing is surveyed has important application in the field such as environmental protection and biochemical analysis, such as: haze pollutes and caused by the micro-nano particle suspended in air exactly; The phytoplankton of micro/nano-scale can affect the water quality (Biogeosciences, 7,3239-3257,2010) of seawater.At present, the main method detecting in gas or liquid the micro-nano particle that suspends has: sedimentation, laser method, sieve method, image method and electric-resistivity method etc.Wherein laser detection has feature quickly and easily, its test philosophy is: after laser is irradiated to suspended particle, because the particle of different-grain diameter is to the scattering angle difference (as Fig. 1) of light, therefore carry out analyzing size-grade distribution (the C.F. Bohren and D.R.Huffman just can knowing particle to the intensity distributions of scattered light, " Absorption and scattering of light by small particles ", John Wiley & Sons, New York, 1983).
In order to improve laser detection precision, needing the interaction strengthening light and particle, thus strengthening scattering effect.For optical resonator, because the resonance effect in chamber makes light intensity be largely increased, the scattering effect of chamber endoparticle to light can be enhanced.But problems faced is: how scattered light, to light Constrained effect, derives from intra resonant cavity by resonator cavity?
In sum, how to design the particle detection sensor based on optical resonator, make to improve light scattering effect, effectively derive scattered light again? that wound of the present invention grinds motivation.
Summary of the invention
The present invention is for solving the problem, and propose " a kind of particle size detecting sensor based on optical resonator ", wherein optical resonator adopts the Fabry-P é rot chamber be made up of deielectric-coating Bragg mirror (DBR); Because the reflectivity of DBR is to angular-sensitive, when incident angle exceedes specific threshold, the reflectivity of DBR sharply reduces, and the scattered light that therefore scattering angle exceedes specific threshold can effectively be derived and be detected in resonator cavity.Sensor of the present invention has the highly sensitive and simple feature of structure.
The characteristic of inventor to optical resonator and DBR has deep research (Applied Optics, vol.45, pp.8448-8453,2006), thus has inspired generation of the present invention.As shown in Figure 2 or Figure 3, sensor is made up of Fabry-P é rot chamber, lens and photodetecting part sensor construction of the present invention.
Described micro-nano particle detecting sensor, its testing process can realize (Fig. 2 or Fig. 3) according to the following steps: 1. laser incides on Fabry-P é rot chamber, and enters acquisition resonance enhancing in chamber; 2. liquid or gaseous sample enter Fabry-P é rot chamber; 3. the particle in sample carries out scattering to the laser in chamber; 4., when the scattering angle of scattered light exceedes specific threshold, scattered light is derived in chamber; 5. scattered light is by photodetection.
Described Fabry-P é rot chamber, can be integrated in (Appl.Phys.Lett., vol.102, pp.163701,2013) on micro-fluidic chip, thus reduces volume.
Described Fabry-P é rot chamber, is made up of (Fig. 4) two Bragg mirrors arranged in parallel, and Bragg mirror wherein forms by the film of different refractivity is alternately stacking.
The specific threshold of described incident angle, has following feature: when incident angle is less than specific threshold, Bragg mirror energy usable reflection light wave; When incident angle is greater than specific threshold, the reflectivity of Bragg mirror to light wave sharply declines, and loses mirror function (Fig. 5).
Described Bragg mirror, can select different membraneous material combinations, thus regulate the refractive index difference between different membraneous material, realize the adjustment to specific threshold.
Described Bragg mirror, can be formed at deposited on substrates film by sputtering, evaporation or the method grown, membraneous material wherein preferentially adopts Si/SiO
2, TiO
2/ SiO
2and GaAs/AlGaAs.
Described light scattering effect, has forward scattering and back scattering two kinds of forms, and corresponding lens and photodetector need rear end (Fig. 2) or front end (Fig. 3) of being placed on Fabry-P é rot chamber.
Described photodetection, can adopt and realize in two ways: 1. adopt charge coupled cell (CCD) array, can to the strong distribution direct imaging of scattered light; 2. adopt photodetector, need the position of rotation or mobile detector, thus obtain the spatial light intensity distribution of scattered light.
Accompanying drawing explanation
Accompanying drawing, it is incorporated into and becomes the part of this instructions, demonstrates embodiments of the invention, and explains principle of the present invention with aforesaid summary together with detailed description below.
Fig. 1 is the scattering schematic diagram of particle to light.
Fig. 2 is the sensor construction of detection forward scattering.
Fig. 3 is the backward scattered sensor construction of detection.
Fig. 4 is the structural representation in Fabry-P é rot chamber.
Fig. 5 be deielectric-coating Bragg mirror reflectivity and the graph of a relation of incident angle.
Embodiment
For making content of the present invention more clear, describe the specific embodiment of the present invention in detail below in conjunction with technical scheme and accompanying drawing.
Example 1
First, Si/SiO is plated on a glass substrate
2film to form Bragg mirror, then by two substrate surface arranged on opposite sides to form Fabry-P é rot chamber (as Fig. 4).
Secondly, passed into by the gas containing suspended particle in Fabry-P é rot chamber, particle carries out forward scattering to the laser of incidence; When the scattering angle of scattered light exceedes specific threshold, scattered light, through Bragg mirror, is derived and is detected by ccd array in Fabry-P é rot chamber; Finally, according to the intensity distributions of the scattered light that CCD detection arrives, analyze the size-grade distribution (Fig. 2) learning particle.
Example 2
First, Si/SiO is plated on a silicon substrate
2film to form Bragg mirror, then by two substrate surface arranged on opposite sides to form Fabry-P é rot chamber (as Fig. 4).
Secondly, passed into by the liquid containing suspended particle in Fabry-P é rot chamber, particle carries out back scattering to the laser of incidence; When the scattering angle of scattered light exceedes specific threshold, scattered light, through Bragg mirror, is derived and is detected (Fig. 3) by photodetector in Fabry-P é rot chamber.
Finally, pointwise moving photoconductor detector, to obtain the space distribution of scattered light intensity.
Example 3
First, plate GaAs/AlGaAs film on gaas substrates to form Bragg mirror, then by two substrate surface arranged on opposite sides to form Fabry-P é rot chamber (as Fig. 4).
Secondly, passed into by the gas containing suspended particle in Fabry-P é rot chamber, particle carries out back scattering to the laser of incidence; When the scattering angle of scattered light exceedes specific threshold, scattered light, through Bragg mirror, is derived and is detected (Fig. 3) by ccd array in Fabry-P é rot chamber.
In sum, the particle size detecting sensor based on optical resonator provided by the invention, can utilize resonance enhancement effect to improve the scattering of particle to light, and the reflectivity impact of incident angle on Bragg mirror can be utilized again to derive scattered light.The sensor of invention has the simple and highly sensitive feature of structure.
The above is the know-why applied of the present invention and instantiation, the equivalent transformation done according to conception of the present invention, if its scheme used do not exceed that instructions and accompanying drawing contain yet spiritual time, all should within the scope of the invention, hereby illustrate.