Highly sensitive strength investigation method based on self-interference type micro-resonant cavity photo-sensorTechnical field
The present invention relates to optical sensing field, especially a kind of Gao Ling based on self-interference type micro-resonant cavity photo-sensorSensitivity strength investigation method.
Background technique
In recent years, low cost, the demand of highly sensitive miniature transducer constantly increase, especially in biochemical preparation andThe substances context of detection such as toxic gas.It addresses that need, industry and academia have proposed and made many typesSensor, wherein optical sensor is concerned in numerous type sensors with its minimum size and high sensitivity.Many optical phenomenas such as, absorption, fluorescence, radiation and refraction etc. and many optical medium structures, such as optical fiber, photonic crystal, micro-Annular resonant cavity, surface plasma and grating etc. are all used to open up novel sensor mechanism to obtain preferable sensing effect.Optical sensor based on micro-ring resonant cavity has size small, high sensitivity and it is compatible with CMOS technology be easily integrated etc. it is excellentPoint is widely used in optical sensing field, when optical waveguide effective refractive index changes with target substance, micro-resonant cavityResonance wavelength is drifted about, thus by test this wave length shift can measure target substance concentration variation (document 1,Mario,La.Notte,Benedetto Troia,Tommaso Muciaccia,Calo Edoardo Campanella,Francesco De Leonardis and Vittoro M.N.Passaro,“Recent advances in gas andchemical detection by vernier effect-based photonic sensors”,Sensors,V.14(3),4831-4855 (2014), i.e. Mario, La.Notte, Benedetto Troia, Tommaso Muciaccia, CaloEdoardo Campanella, Francesco De Leonardis and Vittoro M.N.Passaro " is imitated based on vernierProgress of the optical sensor answered in gas and chemical probing ", sensor, V.14 (3), 4831-4855 (2014)).SoAnd the optical sensor based on micro-ring resonant cavity remains some the shortcomings that limiting its further development and application.For baseIn the optical sensor of micro-ring resonant cavity, high sensitivity needs a sharp resonance spectrum, and detection limit depends on micro-loopThe Q factor of resonant cavity.This requires the transmission loss of device is low, to improve the requirement to device making technics.Subsequent sectionThe personnel of grinding propose the optical sensor based on cursor effect, to obtain high sensitivity and low detection limit.In fact,Raising based on cursor effect sensitivity is derived solely from the reading method of vernier graduation, and physics intrinsic sensitivity does not obtainA bit raising.Dai etc. proposes a kind of micro-ring resonant cavity that coupling is related to based on Mach-increasing Deccan, by measuring resonant wavelengthMovement, about 10 can be detected with higher sensitivity-6~10-5Effective refractive index variation.But in measurement variations in refractive indexValue is 10-6When, wavelength amount of movement is only 0.35pm, needs detection system of a high price (patent 1, ZL200810060460.8).In patent (patent 1, ZL 200810060460.8), it was also proposed that measured in a certain fixed wave lengthThe method of transimission power measures the variation of refractive index, but the frequency spectrum actually generated due to method promise (Fano) effect is wide,There are problems in practice, for example its measurement range is limited, the measurement linearity is very poor.Therefore, high detection accuracy is being keptUnder the premise of, it is necessary to new sensor mechanism is explored so that the detection cost of system is effectively reduced, such as is replaced originally with strength investigationWavelength measurement.
Summary of the invention
It is required when holding high sensitivity in order to overcome existing self-interference type micro-resonant cavity photo-sensor detection method very highThe frequency positioning of precision, the higher deficiency of cost of testing system, the present invention provide one kind under the premise of keeping high sensitivityThe height based on self-interference type micro-resonant cavity photo-sensor for avoiding requiring very high-precision frequency positioning, reducing cost of testing systemSensitivity strength investigation method.
The technical solution adopted by the present invention to solve the technical problems is:
A kind of highly sensitive strength investigation method based on self-interference type micro-resonant cavity photo-sensor, realizes the micro- of the detectionResonant cavity photo-sensor includes an input waveguide, a micro-ring resonant cavity, an output waveguide and an optical detection arm waveguide,Input waveguide and output waveguide are coupled with micro-ring resonant cavity respectively, are placed in the two sides of micro-ring resonant cavity, and one end of input waveguide isThe light source incoming end of entire optical sensor；The other end of input waveguide and light are visited at the coupling of input waveguide and micro-ring resonant cavityThe input terminal of test arm waveguide is connected；The output end of optical detection arm waveguide and output at the coupling of output waveguide and micro-ring resonant cavityOne end of waveguide is connected, and the other end of output waveguide is transducing signal exit end；Out radio-frequency spectrum possess led with unicast be coupled to it is micro-The similar frequency spectrum of annular resonant cavity, the transmission spectrum are the frequency spectrums for transmitting valley and having periodic distribution；
Detection method are as follows: measured matter is covered on to the upper surface of optical detection arm waveguide, light enters from one end of input waveguideIt penetrates, is coupled with micro-ring resonant cavity, then a part is coupled into micro-ring resonant cavity；The other end of the another part from input waveguideIt is emitted and passes through optical detection arm and enter output waveguide, a part of light is due to the coupling between output waveguide and micro-resonant cavity in this partCooperation is used, and is again coupled into micro-resonant cavity, and a part of light being coupled out in a part of light and micro-ring resonant cavity in this partIt is emitted after interference from the output waveguide other end；High sensitivity can be realized in variation by testing resonance wave strong point intensity transmissionSensing.
Further, when measured matter refractive index changes, the optical path length of optical detection arm waveguide changes, not onlyResonance wavelength at transmission valley is drifted about, and the intensity for transmitting valley changes.
Technical concept of the invention are as follows: when optical detection arm waveguide length meets 0.75 times equal to micro-ring resonator lengthWhen, the radio-frequency spectrum that goes out of the self-interference type micro-ring resonant cavity possesses to lead with unicast and is coupled to the similar frequency spectrum of micro-ring resonant cavity, the biographyDefeated spectrum is the frequency spectrum for transmitting valley and having periodic distribution.In the corresponding resonance wavelength of transmission valley, not only with the micro-ring resonantThe physical length of chamber is related, and long with the physics of the coefficient of coup and optical detection arm of input and output waveguide and micro-ring resonant cavityIt spends related.Equally, the size also coefficient of coup and optical detection with input and output waveguide and micro-ring resonant cavity of valley is transmittedThe physical length of arm is related.Therefore, when measured matter refractive index changes, the optical path length of optical detection arm waveguide becomesChange, not only transmits the resonance wavelength at valley and drift about, but also the intensity for transmitting valley changes.By testing resonance waveHighly sensitive sensing can be realized in the variation of strong point intensity transmission.
Beneficial effects of the present invention are mainly manifested in: so that the sensor is under the premise of keeping high detectivity,It is only necessary to one high-precision ionization meter can be realized with the laser of frequency sweep, avoid sensors with auxiliary electrode in measurement frequencyVery high-precision frequency positioning is needed when rate is mobile, greatly reduces the cost of test macro.
Detailed description of the invention
Fig. 1 is self-interference type micro-ring resonant cavity optical sensor structural schematic diagram.
Fig. 2 is the radio-frequency spectrum out of self-interference type micro-ring resonant cavity.
Transmission paddy of the Fig. 3 at wavelength X=1552nm is with input and output waveguide and micro-ring resonant cavity coefficient of coup sizeVariation.
Transmission paddy of the Fig. 4 at wavelength X=1552nm with optical detection arm waveguide optical path length minor change when and generateVariation.
The normalization intensity transmission value that Fig. 5 transmits paddy at wavelength X=1552nm is micro- with optical detection arm waveguide optical path lengthThe curve of small variation.
Specific embodiment
The invention will be further described below in conjunction with the accompanying drawings.
Referring to Fig.1~Fig. 5, a kind of highly sensitive strength investigation method based on self-interference type micro-resonant cavity photo-sensor,The micro-resonant cavity photo-sensor for realizing the detection includes the micro-ring resonant cavity 2, one of input waveguide 1, one 3 and of output waveguideA piece optical detection arm waveguide 4, input waveguide 1 and output waveguide 3 are coupled with micro-ring resonant cavity 2 respectively, are placed in micro-ring resonant cavity 2Two sides, one end of input waveguide 1 is the light source incoming end of entire optical sensor, in the coupling of input waveguide 1 and micro-ring resonant cavity 2Place, the other end of input waveguide 1 is connected with the input terminal of optical detection arm waveguide 4, in the coupling of output waveguide 3 and micro-ring resonant cavity 2At conjunction, one end of output waveguide 3 is connected with the output end of optical detection arm waveguide 4, and the other end of output waveguide 3 goes out for transducing signalIt penetrates end: going out radio-frequency spectrum and possess to lead with unicast to be coupled to the similar frequency spectrum of micro-ring resonant cavity, which is that transmission valley has weekThe frequency spectrum of phase property distribution；
Detection method are as follows: measured matter is covered on to the upper surface of optical detection arm waveguide, light enters from one end of input waveguideIt penetrates, is coupled with micro-ring resonant cavity, then a part is coupled into micro-ring resonant cavity；The other end of the another part from input waveguideIt is emitted and passes through optical detection arm and enter output waveguide, a part of light is due to the coupling between output waveguide and micro-resonant cavity in this partCooperation is used, and is again coupled into micro-resonant cavity, and a part of light being coupled out in a part of light and micro-ring resonant cavity in this partIt is emitted after interference from the output waveguide other end；High sensitivity can be realized in variation by testing resonance wave strong point intensity transmissionSensing.
Further, when measured matter refractive index changes, the optical path length of optical detection arm waveguide changes, not onlyResonance wavelength at transmission valley is drifted about, and the intensity for transmitting valley changes.
Example: self-interference type micro-ring resonant transducer in this example, R=30 μm of micro-loop radius, then the physics of micro-loop circumference is longSpend LR=2 π R, the physical length of optical detection arm waveguide are LW=0.75LR+d.Fig. 2 is the radio frequency out of self-interference type micro-ring resonant cavitySpectrum, d=0.004 μm at this time, effective refractive index neff=2.85, the coupled systemes of input waveguide and output waveguide and micro-ring resonant cavityNumber it is equal, be 0.5, in the sensor in all optical waveguides optical mode unit length loss factor α=0.01dB/cm.From figure 2 it can be seen that the radio-frequency spectrum out of the self-interference type micro-ring resonant cavity, which possesses to lead with unicast, is coupled to micro-ring resonant cavity classAs frequency spectrum, the transmission spectrum be transmit valley have periodic distribution frequency spectrum.Fig. 3 is shown at wavelength X=1552nmPaddy is transmitted with the variation of input and output waveguide and micro-ring resonant cavity coefficient of coup size.Fig. 4 is shown at wavelength X=1552nmTransmission paddy with optical detection arm waveguide optical path length minor change when and the variation that generates.This shows corresponding in transmission valleyResonance wavelength, it is not only related with the physical length of the micro-ring resonant cavity, but also the coupling with input and output waveguide and micro-ring resonant cavityThe physical length of collaboration number and optical detection arm is related.Equally, transmit valley size also with input and output waveguide and micro-loopThe coefficient of coup of resonant cavity and the physical length of optical detection arm are related.Fig. 5 is shown transmits paddy at wavelength X=1552nmIntensity transmission value is normalized with the curve of optical path length minor change d.As can be seen from Figure in k=0.5,1nm < d <The good linearity can be obtained when 2.5nm, measurement accuracy is about 0.1nm at this time, and corresponding variations in refractive index is about 10-6.Work as kWhen=0.15,0.85, corresponding measurement range expands, but measurement accuracy declines.In k=0.9985, measurement range can expandTo 25nm, measurement accuracy falls to 1nm, and corresponding variations in refractive index is about 10-5。
Above-described embodiment is used to illustrate the present invention, rather than limits the invention, in spirit of the invention andIn scope of protection of the claims, to any modifications and changes that the present invention makes, protection scope of the present invention is both fallen within.