CN109100310B - Ultra-spectrum detection micro-system - Google Patents
Ultra-spectrum detection micro-system Download PDFInfo
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- CN109100310B CN109100310B CN201810745280.7A CN201810745280A CN109100310B CN 109100310 B CN109100310 B CN 109100310B CN 201810745280 A CN201810745280 A CN 201810745280A CN 109100310 B CN109100310 B CN 109100310B
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Abstract
A hyperspectral detection microsystem comprising: the device comprises a light collection coupling module, a waveguide light splitting chip and a spectrum data processing module, wherein the waveguide light splitting chip comprises a cascade MZI waveguide filter, a waveguide optical switch array, a thermo-optic phase modulation MZI array and an on-chip integrated linear array detector. The invention integrates the integrated silicon-based cascade MZI array waveguide technology, the thermo-optic phase modulation technology, the silicon-based spectrum light splitting technology, the on-chip detector integration technology, the signal processing and spectrum recovery algorithm, the Si-CMOS process and the high-density integration manufacturing process of the microsystem, and has the advantages of wide spectrum detection range, high spectrum detection precision, ultra-small volume, weight and power consumption, ultra-low cost, quick maneuvering and the like.
Description
Technical Field
The invention relates to the field of miniature spectral analysis instruments, in particular to a chip-level hyperspectral detection micro-system based on a silicon-based cascaded MZI array waveguide technology.
Background
As an important optical detection sensing means, the super-resolution spectral analysis technology can be widely applied to the fields of food safety detection, gas monitoring, trademark anti-counterfeiting and the like. Food is often required to be subjected to additive detection, corruption degree detection, pesticide residue detection, chemical residue detection and other work in laboratories related to food hygiene, and a sample tissue is required to be extracted to perform chemical reaction detection with a specific type of reagent in the traditional method, so that the detection time is short, the process is complex, and the cost of the consumed detection reagent is high. The detection mode utilizing the spectral analysis technology has the advantages of simple operation, quick detection time, no consumption of a detection reagent, non-contact and no damage. Meanwhile, the target detection accuracy can be effectively improved by improving the spectral resolution and expanding the spectral range in a targeted manner. In addition, in the field of gas monitoring, the detection means of the spectral analysis technology can avoid the replacement of detection reagents and prolong the service life of products.
The micro spectrometer with mature technology at present can be mainly divided into a dispersion type spectrometer and an interference type spectrometer according to the light splitting principle. Dispersive micro-spectrometers are generally based on the principle of optical splitting of grating dispersion, and are combined with classical optical structures such as Ebert-fast structure, Czerny-Turner structure, Littrow structure, etc. to realize fine measurement of spectra. The grating structure can adopt two structures of a plane grating and a concave grating, wherein the optical structure based on the plane grating is adopted to facilitate the modularization of system elements. Compared with a plane grating system, the concave grating omits a collimating lens and an imaging lens element, the same focal depth can have smaller system volume, and meanwhile, the concave grating can correct most of aberration of the system through holographic optimization design.
However, the dispersive micro spectrometer is mainly based on the miniaturization of the optical machine structure and the system elements, the integration degree is not high, and the stability of the system is poor. In addition, the micro spectrometer based on dispersion light splitting has small luminous flux, low energy utilization rate and higher requirement on detection light intensity, and limits the action distance and the application range of the micro spectrometer.
The interference type micro spectrometer obtains a spectrum signal by carrying out Fourier change on a signal obtained by detection based on an interference principle. The research institute of the microtechnology of Neuchatel university of Switzerland developed a sheet grating integrated Fourier transform spectrometer, which was built with an electrostatic comb drive fabricated on an SOI chip by a deep reactive etching method to control the movement of a mirror. The height of the reflector is 75 μm, the grating period number is 32mm-1, the grating period length is 100 μm, the total size of the device is 7mm × 4mm, and the working range of the spectrometer is 380 nm-1700 nm. A NeoSpectra type spectrometer of Egypt Si-Ware company adopts MEMS technology to realize a Michelson interferometer on a silicon substrate, realizes spectrum adjustment through an MEMS actuator, and utilizes an InGaAs detector to detect signals and perform Fourier transformation on the signals to obtain spectrum information.
For the spectrograph based on the Michelson interferometer and the spectrograph based on the adjustable F-P cavity, the MEMS electrostatic adjusting technology is relied on, and the requirements on the adjusting precision and the stability of the MEMS device are high. In addition, the interference type micro spectrometer has a complex structure, high requirements on MEMS processing technology and high cost, and limits the application range of the interference type micro spectrometer.
Therefore, how to improve the integration degree of the system, reduce the complexity of the structure, and expand the spectrum detection range becomes a technical problem that needs to be solved urgently in the prior art.
Disclosure of Invention
The invention aims to provide a hyperspectral detection micro-system which can reduce the volume, reduce the system number, improve the resolution ratio and expand the spectrum detection range.
In order to achieve the purpose, the invention adopts the following technical scheme:
a hyperspectral detection microsystem comprising:
the light collection coupling module is used for collecting the radiation light information of the target and coupling the radiation light information to the waveguide light splitting chip;
the waveguide light splitting chip is used for filtering the collected radiation light, performing spectral light splitting by using the MZI array, and outputting an electric signal after photoelectric conversion;
and the spectral data processing module is used for restoring the output electric signal into the spectral information of the target.
Optionally, the light collection coupling module specifically includes:
the optical lens group is plated with an anti-reflection and anti-filtering film layer and is used for receiving the radiation light of a target spectrum section and obtaining the radiation light with input spectrum bandwidth;
a transmission optical fiber for improving the optical coupling efficiency of the radiation light into the optical waveguide as an intermediate stage;
and the lateral taper type mode matcher is used for coupling the radiation light from the transmission optical fiber into the waveguide light-splitting chip.
Optionally, in the light collection and coupling module, the coupling efficiency of the radiated light and the transmission fiber in the space is expressed as:
wherein a is the ratio of the diameter of the optical lens group to the diameter of the field before the fiber mode field propagates back to the optical lens;
AR、ACthe area of a coupling mirror and the area of speckles of the optical lens group are respectively;
x1、x2the sizes of light spots of the light field incident on the optical lens are respectively the size of the light spot of the main shaft and the size of the light spot in the vertical direction.
Optionally, the waveguide optical splitting chip specifically includes:
the device comprises a cascaded MZI waveguide filter, a waveguide optical switch array, a thermo-optic phase modulation MZI array and an on-chip integrated linear array detector.
The cascaded MZI waveguide filter is used for dividing the input spectral bandwidth into n optical channels, and each optical channel has a certain optical channel bandwidth;
the waveguide optical switch array is used for carrying out n multiplied by 1 gating on n optical channels;
the thermo-optic phase modulation MZI array is used for performing spatial Fourier light splitting on the gated optical channel and realizing spectral fine tuning through thermo-optic phase modulation;
and the on-chip integrated linear array detector is used for performing photoelectric conversion on the optical signal output by the thermo-optic phase modulation MZI array waveguide to output an electric signal.
Optionally, the cascaded MZI waveguide filter divides an input spectral bandwidth of 500nm into 4 optical channels with a bandwidth of 125 nm.
Optionally, the waveguide optical switch array is based on a silicon photonic integrated technology, and carrier injection mmi (multimode interference) is adopted, so that the absorption coefficient of the material is changed by changing the concentration of injected carriers, thereby sequentially realizing switching of a plurality of spectral bands with different central wavelengths.
Optionally, the spectrum detection resolution expression of the thermo-optic phase modulation MZI array is as follows:
the spectrum detection spectrum is wide:
wherein is introduced into0Is the central wavelength of the distinguishable spectral range; n iseffIs the waveguide effective refractive index; n is MZI array number; Δ LminThe minimum length difference between the two arms of the MZI.
Optionally, the minimum optical path difference before the thermo-optic phase modulation MZI array introduces the thermo-optic phase modulation is Δ LminOutput power of each output port is Pout(Ii) The minimum optical path difference between the introduced thermally tuned MZI interferometers is changed to Δ Lmin+ΔL0Output power after thermal regulation is Pout(Ii+iΔL0) Thereby changing the wave number σ0And further to change the central wavelength lambda of the distinguishable spectral range0And more precise spectrum detection is realized.
Optionally, the on-chip integrated linear array detector realizes on-chip integration by adopting a heterogeneous or heterogeneous integration method.
Optionally, the spectral data processing module specifically includes:
the noise removal module is used for filtering a background noise signal in the spectrum detection micro-system;
the flat field correction module is used for calibrating the optical detector to obtain response coefficients of different pixels of the optical detector and compensating signal errors caused by the nonuniformity of the optical detector;
the ADC apodization module is used for carrying out apodization operation to recover a real spectrum signal and improve the signal-to-noise ratio;
and the spectrum data inversion module is used for performing spectrum data inversion to obtain preliminary spectrum information.
And the spectral radiometric calibration module is used for radiometric calibration of the spectrum, correcting the spectral information obtained by inversion and outputting the spectral information.
The invention has the following advantages
(1) The invention provides a chip-level super-resolution spectrum detection micro-system architecture based on a silicon optical integration technology, wherein a waveguide cascade broadband spectrum filter, a planar waveguide MZI array light splitting module and a detector are integrated on the same substrate, compared with the traditional super-spectrum detection system, the size, the weight and the power consumption are greatly reduced, a scanning module is not needed, the stability of the system can be improved, and the chip-level super-spectrum detection is realized.
(2) The invention adopts a cascade system framework of broadband spectrum pre-dispersion and waveguide MZI array spectrum fine dispersion, can realize spectrum detection with large spectrum detection range and higher spectrum resolution, and has better spectrum section expansibility.
(3) On the basis of MZI spectral splitting of the waveguide array, the invention provides that a thermo-optic phase modulation technology is used for adjusting each MZI optical path difference, so that ultrahigh spectral resolution detection in a target spectral range is realized, and output optical power under different optical path differences can be obtained on the premise of not increasing the number of MZI arrays.
Drawings
FIG. 1 is a block diagram of a hyperspectral detection microsystem according to an embodiment of the invention;
FIG. 2 is a block diagram of a hyperspectral detection microsystem according to an embodiment of the invention;
FIG. 3 is a schematic structural diagram of a light collection and coupling module according to an embodiment of the present invention;
FIG. 4 is an effect diagram of an ideal broad spectrum pre-splitter module;
FIG. 5 is a diagram of the effect of a 1200nm-1325nm optical switch module according to an embodiment of the present invention;
FIG. 6 is an enlarged frame diagram of a silicon-based thermo-optic phase modulation array waveguide unit according to an embodiment of the present invention;
FIG. 7 is a block diagram of a spectral data processing module according to an embodiment of the present invention.
The reference numerals in the drawings respectively refer to the technical features:
1. a light collection coupling module; 2; a waveguide spectroscopic chip 3; a spectral data processing module; 11. an optical lens group; 12. a transmission optical fiber; 15. a lateral taper pattern matcher; 21. cascading MZI waveguide filters; 22. a waveguide optical switch array; 23. thermo-optic phase modulation MzI array waveguide; 24. integrating a linear array detector on a chip; 31. a noise removal module; 32. a flat field correction module; 33. an ADC apodization module; 34. a spectral data inversion module; 35. spectral radiance calibration module.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
The invention integrates a silicon-based cascade MZI array waveguide technology, a silicon-based spectrum splitting technology, a spectrum differential analysis technology based on thermo-optic phase modulation, an on-chip detector integration technology, a signal processing and spectrum restoration algorithm, and designs a waveguide splitting chip by utilizing the technologies to construct a chip-level hyper-spectrum detection micro-system architecture.
Specifically, the method comprises the steps of firstly collecting target radiation light information, coupling the target radiation light information to a waveguide light splitting chip, carrying out spectrum broadband pre-splitting on input light in the waveguide light splitting chip through a cascade broadband filter, roughly splitting the input light into a plurality of broadband spectral bands, and then carrying out super-resolution spectrum splitting in each spectral band through a planar waveguide MZI array; the thermo-optic phase modulation unit is introduced into the planar waveguide array unit, so that spectral information under different optical path differences can be obtained, and further more fine spectral information can be obtained through spectral differential analysis; in order to improve the integration level of the system, a waveguide optical switch array is introduced between a broadband filter and a thermo-optic phase modulation MZI array to switch among various spectral bands, so that the time-sharing multiplexing of the planar waveguide super-resolution light splitting module is realized; output light of the planar waveguide array is coupled to a corresponding on-chip integrated detector in an aligning manner, and after the output light of the detector is read by a reading circuit, spectral information of a target is obtained through spectral signal restoration processing, so that chip-level, ultra-spectral resolution and wide spectral range spectral detection is realized.
Referring to FIG. 1, a block diagram of a hyperspectral detection microsystem according to an embodiment of the invention is shown, and FIG. 2 is a block diagram of a hyperspectral detection microsystem according to an embodiment of the invention.
The hyperspectral detection microsystem comprises: the device comprises a light collection coupling module 1, a waveguide light splitting chip 2 and a spectrum data processing module 3;
the light collection coupling module 1 is used for collecting the radiation light information of the target, and coupling the radiation light information to the waveguide optical splitting chip 2, wherein the radiation light information comprises light emitted and reflected by the target;
the waveguide light splitting chip 2 is used for filtering the collected radiation light, performing spectral light splitting by using the MZI array, and outputting an electric signal after photoelectric conversion;
and the spectral data processing module 3 is used for restoring the output electric signal into the target spectral information.
For the light collection coupling module 1, since the technical scheme of directly coupling the space light into the optical waveguide by using the waveguide grating is very sensitive to the wavelength of the incident light, the invention adopts a cascading processing scheme of coupling the optical lens group with the optical fiber and then coupling the optical fiber with the waveguide light splitting chip. And coupling and packaging the lens group and one end of the broadband transmission optical fiber, and coupling the other end of the lens group and the input waveguide of the on-chip integrated module of the waveguide light splitting chip to realize front-end input of a detection optical signal. When the optical fiber is coupled with the waveguide, the influence of the optical field mode transmission characteristic under a certain spectral bandwidth (for example, 500nm) on the coupling efficiency needs to be considered, so that the mode matcher scheme is adopted for optical coupling, specifically, the lateral tapered mode matcher is adopted for optical coupling. The method has simple process, easy realization and simple and complete theory, and can realize higher coupling efficiency by designing and adjusting parameters such as the length, the width, the tapered region length, the lateral tapered function and the like of the output waveguide.
In particular, with reference to fig. 3, a specific form of the light collection coupling module 1 is shown, comprising:
the optical lens group 11 is plated with an anti-reflection and anti-filtering film layer and is used for receiving the radiation light of a target spectrum section and obtaining the radiation light with an input spectrum bandwidth; optionally, the input spectral bandwidth is 500nm, so that light with wavelength of 1200nm to 1700nm is transmitted, and light with other spectral bands is cut off.
A transmission optical fiber 12 for improving the optical coupling efficiency of the radiation light into the optical waveguide as an intermediate stage;
and a lateral taper mode matcher 13 for coupling the radiation light from the transmission fiber into the waveguide optical splitter chip.
The lateral tapered mode matcher 13 can improve the optical coupling efficiency of the radiation light as the signal light entering the waveguide light splitting chip from the transmission fiber, and avoid the loss of the incident light signal when the incident light is in a wide spectral range due to the optical frequency selectivity of the waveguide grating;
the coupling efficiency of the radiated light and the transmission fiber in the space can be expressed as follows:
wherein a is the ratio of the diameter of the optical lens group to the diameter of the field before the fiber mode field propagates back to the optical lens;
AR、ACthe area of a coupling mirror and the area of speckles of the optical lens group are respectively;
x1、x2the sizes of light spots of the light field incident on the optical lens are respectively the size of the light spot of the main shaft and the size of the light spot in the vertical direction.
According to the simplified waveguide transmission theory, single-mode transmission needs to satisfy the following conditions:
wherein under the symmetrical light guide, the light guide,
n1n2respectively waveguide core and substrate/cladding refractive indices. I.e. waveguide core thickness
Under the same waveguide structure parameters, if the short wavelength meets the single mode condition, the long wavelength also meets the single mode condition. The waveguide parameters in the subsequent modules are designed and adjusted according to different parts and functions.
For the waveguide spectroscopic chip 2, referring to fig. 1 and 2, a plurality of components are integrated in an on-chip integration manner, including: the device comprises a cascaded MZI waveguide filter 21, a waveguide optical switch array 22, a thermo-optic phase modulation MZI array 23 and an on-chip integrated line array detector 24.
The cascaded MZI waveguide filter 21 is configured to divide the input spectral bandwidth into n optical channels, where each optical channel has a certain optical channel bandwidth, and a product of the optical channel bandwidth and the number of optical channels is equal to the output and input spectral bandwidth. In a specific embodiment, MZI waveguide filters 21 are cascaded to split the 500nm input spectral bandwidth into 4 optical channels of 125nm bandwidth.
And a waveguide optical switch array 22 for n × 1 gating of the n optical channels. In one specific embodiment, 4 125nm bandwidth optical channels are 4 x 1 gated;
a thermo-optic phase modulation MZI array 23, which is used for performing spatial Fourier light splitting on the gated optical channel and realizing spectral fine tuning through thermo-optic phase modulation;
and the on-chip integrated linear array detector 24 is used for performing photoelectric conversion on the optical signal output by the thermo-optic phase modulation MZI array waveguide to output an electric signal.
Taking the spectrum detection range of 1200nm-1700nm as an example, the detection range is divided into a plurality of spectrum bands by a broadband spectrum pre-splitting technology, and the spectrum of a large range is cut to form 4 approximate rectangular window band-pass filters with the spectrum width of 125 nm. The broadband spectrum filter adopts a cascading MZI scheme, namely, filtering is carried out by utilizing a cascading MZI waveguide, and spectrum pre-splitting with large bandwidth and high isolation is realized by the design of an MZI structure and the selection of parameters.
The cascaded MZI waveguide can select a silicon nitride material to design and verify a filter, the refractive index of the silicon nitride is about 2, the waveguide transmission loss is very low in the range of 450nm to 2000nm, the cascaded MZI waveguide is widely used in a CMOS process, and the processing cost is low. By adjusting the etching process parameters and changing the sectional shape of the waveguide, effective dispersion management can be realized, the filter device with low loss and high isolation can be conveniently designed and manufactured,
furthermore, in order to reduce the complexity of subsequent signal processing, in the process of designing the filter device, the power jitter in the spectral band is reduced as much as possible, and a dispersion management scheme based on the cascaded MZI may be matched to implement flat-band filtering. Referring to fig. 4, an idealized broad spectrum pre-splitter effect diagram is shown.
After the broadband spectrum is pre-dispersed, in order to realize ultrahigh resolution subdivision of the spectrum in each spectral band, an ultrahigh resolution spectral subdivision module needs to be additionally connected to each spectral band, but the whole on-chip filtering high resolution light-splitting system occupies a larger chip area. Meanwhile, the ultrahigh-resolution spectral splitting module connected behind each spectral band can adopt the same structural design under the condition of meeting the target resolution. Therefore, in order to further increase the integration level, the invention adopts the waveguide optical switch array to switch among various spectral bands after cascading the MZI waveguide, removes redundant modules, and realizes the gating of spectral passband and the time division multiplexing of the ultra-high resolution spectral module.
Specifically, the waveguide optical switch array 22 is based on a silicon photonic integration technology, and adopts a carrier injection mmi (multimode interference). The absorption coefficient of the material is changed by changing the concentration of injected carriers, so that the switching of a plurality of spectral bands with different central wavelengths is realized in sequence. The waveguide optical switch should improve the response speed of the optical switch as much as possible, reduce the loss and crosstalk of the optical switch, improve the extinction ratio and realize polarization insensitivity. The bandwidth of each optical switch is consistent with the optical channel bandwidth. Referring to fig. 5, a graph illustrating the effect of a 1200nm-1325nm optical switch module according to an embodiment of the present invention is shown.
And the ultrahigh resolution spectrum subdivision module behind the optical switch adopts a silicon-based ultrahigh resolution spectrum division module. The silicon-based ultrahigh-resolution light splitting module is based on a planar waveguide array, a thermo-optic phase modulation technology is introduced on the basis, and the super-resolution light splitting performance of the module is further improved by detecting and analyzing a spectral differential signal.
Specifically, the invention adopts a thermo-optic phase modulation MZI array 23, introduces the MZI structure into an array waveguide, and utilizes the spatial heterodyne technology to improve the spectral resolution of the system. A thermo-optic phase modulation MZI array belongs to a planar waveguide MZI array, and is based on the design idea of an Array Waveguide Grating (AWG), and a waveguide MZI structure is used for replacing a waveguide phase delay line and a star coupler in the AWG. MZIs in each channel have fixed length difference, and coherent light splitting of light with different wavelengths is achieved. The light splitting structure of the structure belongs to a static Fourier spectrum light splitting structure, and the maximum length difference of an array MZI structure is determined according to the spectral resolution in the design; determining the step amount of phase delay according to the detection spectrum range; and determining the number of channels of the array waveguide by combining the spectrum detection range and the resolution. Wherein the spectral detection resolution expression is as follows:
the spectrum detection spectrum is wide:
wherein is introduced into0Is the central wavelength of the distinguishable spectral range; n iseffIs the waveguide effective refractive index; n is MZI array number; Δ LminThe minimum length difference between the two arms of the MZI.
In order to realize the design of large spectral range and high spectral resolution, the number of MZI arrays must be increased, thereby increasing the process difficulty. In order to reduce the processing difficulty, the invention adopts a thermo-optic phase modulation technology, a thermo-optic adjustable unit is introduced into one arm of each MZI in the array, and the optical path difference of two arms in the MZI structure of each array unit is changed, so that the difference is not obtainedThe output optical power under the same optical path difference is shown in an enlarged frame diagram of the silicon-based thermo-optic phase modulation array waveguide unit, referring to fig. 6. The minimum optical path difference before introducing thermo-optic phase modulation is Delta LminOutput power of each output port is Pout(Ii) The minimum optical path difference between the introduced thermally tuned MZI interferometers is changed to Δ Lmin+ΔL0Output power after thermal regulation is Pout(Ii+iΔL0). At this time, the wave number σ will be changed0And further to change the central wavelength lambda of the distinguishable spectral range0Therefore, more precise spectrum detection is realized, and more precise spectrum detection can be carried out on the gravity spectrum area. And carrying out Fourier change on data acquired by the detector linear array, and carrying out inversion to obtain signal spectrum information.
And the on-chip integrated linear array detector 24 is used for performing photoelectric conversion on the optical signal output by the thermo-optic phase modulation MZI array waveguide to output an electric signal.
For the on-chip integration of the linear array detector 24, a heterogeneous or heterogeneous integration method is adopted to realize the on-chip integration of the optical detector and the light splitting module. The heterogeneous method comprises the steps of coupling III-V group materials meeting detection requirements with a light splitting device through bonding, and then performing a device process, or directly bonding a prepared detector chip with the light splitting device; heterogeneous methods typically involve epitaxially growing a layer of Ge material or III-V material directly on selected regions of the device surface, followed by device processing.
For heterogeneous or heterogeneous integration, when the detector is coupled with the waveguide, end-face coupling or evanescent wave coupling is mainly adopted, and the coupling efficiency, the process alignment difficulty, the influence on dark current and the like of two coupling modes are fully considered.
And the spectral data processing module 3 is used for restoring the output electric signal into the target spectral information. Referring to FIG. 7, a diagram of a spectral data processing module according to a specific embodiment of the present invention is shown. The spectrum data processing module is matched with the thermo-optic phase modulation MZI array waveguide, and is used for processing signal spectrum information in real time according to the change of the thermo-optic phase modulation. The method comprises the following steps:
the noise removing module 31 is configured to filter a background noise signal in the spectrum detection micro-system, and mainly includes a dark current output when the detector is not illuminated, and noise caused by background light, and the noise mainly represents fluctuation in a restored spectrum caused by a burr generated on an interference signal; non-linearity in the magnitude of the recovered spectrum due to the non-linear response of the detector, etc. Some of the errors are inherent in the instrument, slowly change along with time, and can be corrected to a certain extent by utilizing instrument modeling and analysis of instrument functions, such as nonlinearity of a detector, instrument linear functions and the like, and other errors occur randomly, but can be detected and corrected through real-time interferogram signals obtained by the instrument according to the characteristics of the errors, such as correction of burrs and phase errors.
The flat field correction module 32 is used for calibrating the optical detector to obtain response coefficients of different pixels of the optical detector and compensating signal errors caused by the nonuniformity of the optical detector;
and the ADC apodization module 33 is configured to perform apodization operation to recover the true spectral signal and improve the signal-to-noise ratio. Apodization is mainly aimed at that all interference signals cannot be obtained due to the limitation of the bandwidth of a detector, spectral data obtained by integral inversion of the interference signals collected by the detector in a limited bandwidth is convolution of real spectral information and a response function of the detector, generally expressed as a rectangular window function, and the real spectral signals can be recovered by utilizing apodization, so that the signal-to-noise ratio is improved.
And the spectrum data inversion module 34 is used for performing spectrum data inversion to obtain preliminary spectrum information.
And the spectral radiometric calibration module 35 is configured to perform radiometric calibration on the spectrum, correct the spectral information obtained through the inversion, and output the spectral information.
Inversion and scaling are mainly aimed at the non-constant response of optical systems, waveguides, detectors, etc. to different wavelengths.
Alternative alternatives of the invention:
in the present invention, an optical lens group is preferably used in light collection, but a conventional lens may be used, which is advantageous in that the technology is mature, but disadvantageous in that it is bulky and heavy.
The carrier switch is preferably used in the waveguide optical switch array 22, but a thermo-optical switch may be used, which has the advantages of mature technology and low switching speed; or an electric absorption light switch is adopted, the advantages are that the extinction ratio is large, and the defects are that the wavelength and polarization dependence is strong.
The thermal optical phase modulation MZI array is preferably adopted in the ultrahigh resolution spectral subdivision module, but carrier dispersion effect phase modulation can also be adopted, the advantages are that the modulation speed is high, the polarization is irrelevant, and the defect is that the loss is large.
In the broad spectrum pre-spectral light-splitting module based on the cascade MZI filter, the waveguide is preferably silicon nitride material, but polymer material, III-V material and the like can be selected, and a plurality of materials are doped to realize the low-loss transmission and the filtering effect of a specific spectral band of the waveguide.
Therefore, the present invention has the following advantages
(1) The invention provides a chip-level super-resolution spectrum detection micro-system architecture based on a silicon optical integration technology, wherein a waveguide cascade broadband spectrum filter, a planar waveguide MZI array light splitting module and a detector are integrated on the same substrate, compared with the traditional super-spectrum detection system, the size, the weight and the power consumption are greatly reduced, a scanning module is not needed, the stability of the system can be improved, and the chip-level super-spectrum detection is realized.
(2) The invention adopts a cascade system framework of broadband spectrum pre-dispersion and waveguide MZI array spectrum fine dispersion, can realize spectrum detection with large spectrum detection range and higher spectrum resolution, and has better spectrum section expansibility.
(3) On the basis of MZI spectral splitting of the waveguide array, the invention provides that a thermo-optic phase modulation technology is used for adjusting each MZI optical path difference, so that ultrahigh spectral resolution detection in a target spectral range is realized, and output optical power under different optical path differences can be obtained on the premise of not increasing the number of MZI arrays.
While the invention has been described in further detail with reference to specific preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (9)
1. A hyperspectral detection microsystem comprising:
the light collection coupling module is used for collecting the radiation light information of the target and coupling the radiation light information to the waveguide light splitting chip;
the waveguide light splitting chip is used for filtering the collected radiation light, performing spectral light splitting by using the MZI array, and outputting an electric signal after photoelectric conversion; wherein the content of the first and second substances,
the waveguide spectroscopy chip specifically includes:
the MZI waveguide filter, the waveguide optical switch array, the thermo-optic phase modulation MZI array and the on-chip integrated linear array detector are cascaded;
the cascade MZI waveguide filter is used for dividing input spectral bandwidth into n optical channels, and each optical channel has certain optical channel bandwidth;
the waveguide optical switch array is used for carrying out n multiplied by 1 gating on n optical channels;
the thermo-optic phase modulation MZI array is used for performing spatial Fourier light splitting on the gated optical channel and realizing spectral fine tuning through thermo-optic phase modulation;
the on-chip integrated linear array detector is used for performing photoelectric conversion on the optical signal output by the thermo-optic phase modulation MZI array waveguide to output an electric signal;
and the spectral data processing module is used for restoring the output electric signal into the spectral information of the target.
2. The hyperspectral detection microsystem according to claim 1, wherein:
the light collection coupling module specifically comprises:
the optical lens group is plated with an anti-reflection and anti-filtering film layer and is used for receiving the radiation light of a target spectrum section and obtaining the radiation light with input spectrum bandwidth;
a transmission optical fiber for improving the optical coupling efficiency of the radiation light into the optical waveguide as an intermediate stage;
and the lateral taper type mode matcher is used for coupling the radiation light from the transmission optical fiber into the waveguide light-splitting chip.
3. The hyperspectral detection microsystem according to claim 2, wherein:
in the light collection coupling module, the coupling efficiency of the radiated light and the transmission fiber in the space is expressed as:
wherein a is the ratio of the diameter of the optical lens group to the diameter of the field before the fiber mode field propagates back to the optical lens;
AR、ACthe area of a coupling mirror and the area of speckles of the optical lens group are respectively;
x1、x2the sizes of light spots of the light field incident on the optical lens are respectively the size of the light spot of the main shaft and the size of the light spot in the vertical direction.
4. The hyperspectral detection microsystem according to claim 1, wherein:
the cascade MZI waveguide filter divides the input spectral bandwidth of 500nm into 4 optical channels with 125nm bandwidth.
5. The hyperspectral detection microsystem according to claim 1, wherein:
the waveguide optical switch array is based on a silicon photonic integration technology, adopts carrier injection MMI (multimode interference), and changes the absorption coefficient of a material by changing the concentration of injected carriers, thereby sequentially realizing the switching of a plurality of spectral bands with different central wavelengths.
6. The hyperspectral detection microsystem according to claim 1, wherein:
the spectrum detection resolution expression of the thermo-optic phase modulation MZI array is as follows:
the spectrum detection spectrum is wide:
wherein λ0Is the central wavelength of the distinguishable spectral range; n iseffIs the waveguide effective refractive index; n is MZI array number; Δ LminThe minimum length difference between the two arms of the MZI.
7. The hyperspectral detection microsystem according to claim 6, wherein:
the minimum optical path difference before the thermo-optic phase modulation MZI array introduces the thermo-optic phase modulation is Delta LminOutput power of each output port is Pout(Ii) The minimum optical path difference between the introduced thermally tuned MZI interferometers is changed to Δ Lmin+ΔL0Output power after thermal regulation is Pout(Ii+iΔL0) Thereby changing the wave number σ0And further to change the central wavelength lambda of the distinguishable spectral range0And more precise spectrum detection is realized.
8. The hyperspectral detection microsystem according to claim 1, wherein:
the on-chip integrated linear array detector realizes on-chip integration by adopting a heterogeneous or heterogeneous integration method.
9. The hyperspectral detection microsystem according to claim 1, wherein:
the spectral data processing module specifically comprises:
the noise removal module is used for filtering a background noise signal in the spectrum detection micro-system;
the flat field correction module is used for calibrating the optical detector to obtain response coefficients of different pixels of the optical detector and compensating signal errors caused by the nonuniformity of the optical detector;
the ADC apodization module is used for carrying out apodization operation to recover a real spectrum signal and improve the signal-to-noise ratio;
the spectrum data inversion module is used for performing spectrum data inversion to obtain preliminary spectrum information;
and the spectral radiometric calibration module is used for radiometric calibration of the spectrum, correcting the spectral information obtained by inversion and outputting the spectral information.
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