CN117629933A - Photon integrated on-chip methane sensor - Google Patents
Photon integrated on-chip methane sensor Download PDFInfo
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 118
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Abstract
The invention discloses a photonic integrated on-chip methane sensor, which comprises a wafer, wherein the wafer comprises a substrate layer, and an active region, a grating layer, an InGaAs layer and a waveguide layer which sequentially extend outwards along a first direction of the substrate layer, wherein the first direction is perpendicular to a light path propagation direction; the wafer is provided with a high reflection film on the initial end face along the light path propagation direction and an antireflection film on the final end face; the electric isolation layer and the gas detection groove extend outwards along the first direction of the grating layer, the waveguide layer and the InGaAs layer are not arranged in the electric isolation layer and the gas detection groove, and the electric isolation layer is close to the end face position of the antireflection film; the end face position of the gas detection groove, which is close to the high-reflection film; neither the gas detection groove nor the electrical isolation layer covers the edge areas of the InGaAs layer and the waveguide layer; the surface of the wafer is provided with an electrode layer; the high-reflection film to electric isolation layer region forms DFB laser, and the electric isolation layer to antireflection film region forms photodetector. The invention realizes the maximum integration and miniaturization, has higher detection precision, and has simpler preparation process and lower cost than the traditional method.
Description
Technical Field
The invention relates to the technical field of infrared sensors, in particular to a photon integrated on-chip methane sensor.
Background
Methane sensors can be classified into electrochemical sensors, thermocatalytic sensors, and infrared sensors according to their principles. Electrochemical methane sensors measure gas concentrations based on chemical reactions between a gas-sensitive electrode and methane. But it is extremely susceptible to interference by other gases causing large measurement errors and, because it is the principle of electrochemical reaction, causes problems of poor long-term stability and short service life of the sensor. The thermocatalytic methane sensor is used for measuring the concentration by heat change generated after methane combustion. Because of the combustion phenomenon, the method has great potential safety hazard, and therefore, the method is difficult to be widely applied. While infrared methane sensors, which have non-contact measurement, high sensitivity, high accuracy and excellent long-term stability, have been greatly developed, measure the absorption of laser light of a specific wavelength by methane molecules.
The infrared methane sensor is developed at a high speed in the field of methane concentration detection, and high-sensitivity, high-precision and non-contact measurement of methane gas is realized. For the traditional infrared methane sensor, in order to realize high-precision concentration measurement, the infrared methane sensor is often matched with a gas chamber to be used simultaneously, so that a higher laser propagation path is realized to reach more obvious signal characteristics. The traditional methane sensor based on infrared absorption spectrum technology generally comprises a laser light source, a photoelectric detector, an air chamber, a signal processing system and the like. However, due to the existence of the air chamber, the overall size of the sensor is greatly increased, although the size of the air chamber can be reduced and the optical path is higher by putting the reflecting mirror in the air chamber, the methane sensor which is more integrated still cannot be realized, and the defects of large volume, complex air chamber structure, difficulty in integration and the like are overcome, so that the methane sensor has a wider application prospect. Thus, on-chip waveguide methane sensors utilizing optical waveguide structures instead of conventional plenums are also emerging.
An on-chip waveguide methane sensor. The sensor mainly comprises an on-chip waveguide, an infrared laser, a photoelectric detector and other components. The working principle is based on the fact that the absorption peak of methane molecules is located in an infrared region, and the transmission and detection of infrared laser on a chip are realized by utilizing a waveguide structure, so that the measurement of methane gas is realized. Compared with the traditional infrared absorption methane sensor, the on-chip waveguide methane sensor has the advantages of small volume and high response speed, and can be integrated on an integrated circuit chip, and has the advantages of low cost and the like, so that the sensor has wide application prospect in the fields of aviation, aerospace, petroleum and natural gas detection, environmental monitoring and the like. However, due to the existence of the waveguide, the loss of the laser light intensity is greatly improved, so that the signal-to-noise ratio of the signal is greatly reduced, the detection sensitivity is greatly reduced, and accurate modulation and detection technology are required. In addition, the detection result is affected by environmental conditions such as temperature and humidity, and calibration and use condition control are required.
Therefore, how to provide a photonic integrated on-chip methane sensor with high integration level and high precision is a technical problem to be solved by those skilled in the art.
Disclosure of Invention
The invention provides a photon integrated on-chip methane sensor aiming at the current research situation and the existing problems.
The invention provides a photon integrated on-chip methane sensor, which comprises a wafer, wherein the wafer comprises a basal layer, an active region, a grating layer, an InGaAs layer, a waveguide layer, an electric isolation layer and a gas detection groove; the active region, the grating layer, the InGaAs layer and the waveguide layer extend outwards in sequence along a first direction of the substrate layer, wherein the first direction is perpendicular to the light path propagation direction; the wafer is provided with a high-reflection film on the initial end face along the light path propagation direction and an antireflection film on the final end face;
the electric isolation layer extends outwards along the first direction of the grating layer, the waveguide layer and the InGaAs layer are not arranged in the electric isolation layer, and the electric isolation layer is close to the end face position of the antireflection film along the light path propagation direction;
the gas detection groove extends outwards along the first direction of the grating layer, the waveguide layer and the InGaAs layer are not arranged in the gas detection groove, and the gas detection groove is close to the end face position of the high-reflection film along the light path propagation direction; the gas detection groove and the electric isolation layer do not cover the edge areas of the InGaAs layer and the waveguide layer;
the surface of the wafer is provided with an electrode layer;
the high-reflection film to the electric isolation layer region form a DFB laser, and the electric isolation layer to the antireflection film region form a photoelectric detector.
Preferably, the InGaAs layer is disposed along the optical path propagation direction and penetrates through the top of the grating layer, the width of the InGaAs layer perpendicular to the optical path propagation direction is smaller than the width of the grating layer, and the InGaAs layer is located at the middle position of the top of the grating layer, and the waveguide layer is formed on the InGaAs layer.
Preferably, the electrode layer covers the surface of the waveguide layer and covers the surface of the grating layer except for the regions of the grating layer on the surface of the electrically isolating layer and the gas detection groove.
Preferably, the active region uses III-V quaternary compound semiconductor material, and comprises a buffer layer, a lower limiting layer, a multiple quantum well and an upper limiting layer from bottom to top; the quantum well exists in the region, and the upper and lower energy level particle number inversions are formed in the active region.
Preferably, the grating layer is formed by adopting secondary epitaxy, and the method comprises the following steps:
after an active region is formed by one-time epitaxy, holographic exposure is carried out on the surface of the active region, and a zero-order grating is prepared;
and carrying out secondary epitaxy by using photoetching, wherein the whole zero-order grating layer integrates a first-order grating, comprising an internal grating region of the DFB laser, and the difference between the Bragg wavelength and the lasing wavelength of the DFB laser is smaller than a given threshold value.
Preferably, the InGaAs layer and the waveguide layer region which are not etched by the electric isolation layer form an electric conductivity region I, the electric isolation layer forms an electric conductivity region II, the electric conductivity of the electric conductivity region I is higher than that of the electric conductivity region II, and the electric conductivity region I is located at two sides of the electric conductivity region II along the propagation direction of the optical path to form a series-parallel circuit.
Preferably, the electrical isolation layer has a resistance of 3KΩ -5KΩ.
Preferably, the waveguide layer adopts a ridge waveguide.
Preferably, the electrode layer is made of Au material.
Preferably, the substrate is a III-V compound semiconductor material.
Compared with the prior art, the invention has the following beneficial effects:
1. compact and integrated: compared with the traditional methane sensor, the methane sensor has the advantages that the optical air chamber is omitted, and the overall size is greatly reduced. Compared with the on-chip waveguide methane sensor, the optical waveguide is removed, the DFB laser and the photoelectric detector are designed on the same carrier substrate, and compared with the waveguide methane sensor, the optical waveguide structure is removed, so that the optical structure part of the sensor is integrated and miniaturized to the greatest extent.
2. High detection precision: thanks to the design of windowing the gas detection groove of the DFB laser chip, the methane gas is innovatively diffused into the DFB laser chip, so that the laser can interact with methane molecules in a resonance stage, the laser is continuously reflected at two end faces of the chip in a light intensity lasing stage, the physical reaction of the gas and the laser is greatly improved, the photoelectric detector and the DFB laser are simultaneously designed on the same wafer carrier, the light intensity of the laser can be transmitted through the waveguide in the chip, the propagation distance of the light is greatly reduced, and the light intensity attenuation is smaller compared with that of the waveguide structure, so that the detection precision of the methane concentration is greatly improved.
3. Low cost: because the DFB laser and the photoelectric detector are integrated on the same wafer, the epitaxial materials of the DFB laser and the photoelectric detector are basically consistent with the subsequent process, the cost can be effectively saved, and the process time can be shortened.
4. High stability: the on-chip integrated sensor is composed of precise microelectronic elements, providing highly reliable measurement results. By utilizing an integrated calibration and correction algorithm, excellent accuracy and stability can be provided, drift and errors of the sensor are reduced, and accuracy and long-term reliability are ensured.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is apparent that the drawings in the following description are only embodiments of the present invention, and that other drawings may be obtained from the provided drawings without inventive labor for those skilled in the art.
FIG. 1 is a top view of a photonic integrated on-chip methane sensor structure provided by an embodiment of the present invention;
FIG. 2 is a side view of a photonic integrated on-chip methane sensor structure provided in an embodiment of the present invention;
fig. 3 is a left side view of a photonic integrated on-chip methane sensor structure provided in accordance with a third embodiment of the present invention.
In the figure:
1 is a DFB laser, 2 is a photoelectric detector, 3 is a substrate layer, 4 is an active region, 5 is a grating layer, 6 is an electrode layer, 7 is a waveguide layer, 8 is an electrode layer, 9 is a coating film, 10 is a gas detection groove, and 11 is an InGaAs layer.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention is different from the on-chip waveguide methane sensor, the DFB laser and the photoelectric detector are designed on the same wafer substrate in the chip design stage, the waveguide structure for transmitting laser is removed, so that the smaller optical structure size is realized, and the transmission of the laser to the photoelectric detector is realized through the waveguide in the chip, so that the transmission distance is greatly shortened, the light intensity is not greatly attenuated, and the better signal-to-noise ratio is ensured. In addition, in order to improve interaction between methane gas and laser, unlike a conventional structure, a DFB laser chip is designed to diffuse methane gas into the laser chip through a gas detection groove near an HR end face, and when laser resonates in the chip, the laser acts with the gas, so that higher precision of the methane sensor is realized. The high integration of the same chip of the DFB laser and the photodetector is beneficial, and the two are basically consistent in the growth of epitaxial materials and the subsequent process, so that the processing cost can be greatly saved.
The principle of application of the invention is described in detail below with reference to the accompanying drawings.
As shown in fig. 1-3, the DFB laser 1 and the photodetector 2 are integrated on the same substrate layer to form a wafer, specifically:
the photonic integrated on-chip methane sensor comprises a wafer, wherein the wafer comprises a substrate layer 3, an active region 4, a grating layer 5, an InGaAs layer 11, a waveguide layer 7, an electric isolation layer 6 and a gas detection groove 10; the active region 4, the grating layer 5, the InGaAs layer 11 and the waveguide layer 7 sequentially extend outwards along a first direction of the substrate layer 3, wherein the first direction is perpendicular to the light path propagation direction; the wafer has a high reflection film on the initial end face along the light path propagation direction and an antireflection film on the final end face.
In specific execution, the active region 4, the grating layer 5, the InGaAs layer 11 and the waveguide layer 7 are epitaxially grown on the substrate layer 3 in sequence; and plating a high-reflection film on the light path transmission initial end face of the wafer, and plating an antireflection film on the light path transmission terminal end face of the wafer.
The electric isolation layer 6 extends outwards along the first direction of the grating layer 5, the electric isolation layer 6 is not provided with the waveguide layer 7 and the InGaAs layer 11, the electric isolation layer 6 is close to the end face position of the antireflection film along the light path propagation direction, and the electric isolation layer 6 does not cover the edge areas of the InGaAs layer 11 and the waveguide layer 7.
In a specific implementation, the waveguide layer 7 and the InGaAs layer 11 are etched to form an electrical isolation layer 6, the electrical isolation layer 6 being formed on top of the grating layer 5.
The gas detection groove 10 extends outwards along the first direction of the grating layer 5, the waveguide layer 7 and the InGaAs layer 11 are not arranged in the gas detection groove 10, and the gas detection groove 10 is close to the end face position of the high-reflection film along the light path propagation direction; the gas detection groove 10 does not cover the edge regions of the InGaAs layer 11 and the waveguide layer 7.
In a specific implementation, the waveguide layer 7 and the InGaAs layer 11 are etched to form a gas detection trench 10, and the gas detection trench 10 is formed on top of the grating layer 5.
An electrode layer 8 is formed on the surface of the wafer;
the regions from the high reflection film to the electric isolation layer 6 form the DFB laser 1, and the regions from the electric isolation layer 6 to the antireflection film form the photodetector 2.
The photon integrated on-chip methane sensor provided by the embodiment of the invention consists of an optical structure and a signal processing system. In the optical structure part, the chip of the DFB laser 1 and the photoelectric detector 2 are designed on the same wafer carrier, unlike the traditional separated light source and detector, so that the high integration and miniaturization of the laser light source and the photoelectric detector 2 are realized. During gas concentration measurement, the amplitude of the light intensity signal of the photodetector 2 can seriously affect the final measurement error, so that compared with a waveguide sensing structure, the transmission of the light source is in the same waveguide, and the loss of laser in the propagation process is reduced. Therefore, the optimal design enables the emergent light of the DFB laser 1 to be directly received by the detector, so that the signal-to-noise ratio is greatly improved.
At present, the principle of application of the infrared methane sensor is a spectrum absorption method, and the principle is that when laser light with a specific wavelength passes through a gas molecule to be detected, a light intensity absorption phenomenon is generated, and the phenomenon is detected by the photoelectric detector 2, so that the gas concentration is detected. In this process, the length of the optical path length, which is the length of the interaction between the laser and the gas, has the greatest influence on the signal. On photonic chips with integrated properties, therefore, in order to achieve a higher signal-to-noise ratio, the structure differs from the conventional DFB laser 1 structure at the chip design stage. A gas detection trench 10 is etched into the ridge waveguide of the DFB laser 1 down to the grating layer 5 and no electrode layer 8 is plated on it, so that the gas interacts with the laser here. Because of the enhanced resonance brought by the laser grating layer 5, the interaction between the laser and the gas molecules is enhanced, and the absorption optical path of the gas molecules is improved, thereby improving the detection precision of the concentration of methane molecules.
As shown in fig. 1, the infrared methane sensor is in a strip shape along the propagation direction of the optical path, and as shown in fig. 3, the InGaAs layer 11 and the waveguide layer 7 are only arranged in the middle area, i.e. the width is smaller than the widths of the substrate layer 3, the active region 4 and the grating layer 5, and extend through the whole optical path.
In one embodiment, DFB laser 1 is used to generate a laser that detects the wavelength of a particular gas, and when an applied current is injected into the active region, it will cause the quantum well region to accumulate a large number of electrons, the population of the upper and lower energy levels of this region are reversed, stimulated radiation occurs, light amplification occurs, and the amplified light is reflected back and forth between the two end faces, resonates continuously, and generates laser light. And the specific wavelength output is selected through the periodic feedback of the grating.
The photodetector 2 (PD) converts an electrical signal into an optical signal, when light is incident on the PD, atoms in the semiconductor PN junction are excited by absorbing photons, and generate unbalanced carriers of electron-hole pairs, holes move to the P region under the action of an internal electric field, electrons move to the N region, a reverse photocurrent is generated, and a voltage signal is formed under the action of an external amplifying circuit and detected by the external circuit. The optical power intensity can be obtained by detecting the optical current. The absorption peak of the gas can influence the power of the light wave with specific wavelength, and the change of the power influences the concentration of the photo-generated carriers in the PD region, so that the current generated in the region is influenced, and the gas concentration can be detected by representing the current.
The distributed feedback semiconductor laser and the photoelectric detector 2 are integrated on the same wafer, and each layer of material is subjected to vapor phase epitaxial growth by a Metal organic chemical vapor deposition device (Metal-organic Chemical Vapor Deposition, MOCVD).
In one embodiment, the substrate layer 3 is made of a III-V compound semiconductor material, and the forbidden band width of the III-V compound semiconductor material can meet the requirement of near infrared gas detection.
In one embodiment, active region 4 is formed using a III-V family quaternary compound semiconductor material, such as InGaAsP/AlGaAsP, and the like, and structurally includes a buffer layer, a lower confinement layer, a multiple quantum well (including a well and a barrier), and an upper confinement layer. The region has quantum wells where a large number of electrons transition from the top of the valence band to the bottom of the conduction band, creating an inversion of the upper and lower energy level population.
In one embodiment, in order to realize stable single-mode lasing of the laser, and the lasing wavelength is consistent with the absorption peak of the gas to be detected, the period of the grating needs to be designed, and secondary epitaxial fabrication is performed on the process. Firstly, after the active region 4 is manufactured from bottom to top by the once-epitaxial material, holographic exposure is performed on the surface of the active region to prepare the zero-order grating. And then carrying out secondary epitaxy on the whole zero-order grating layer by using a photoetching technology, and finally integrating a first-order grating inside the laser, wherein the Bragg wavelength of the first-order grating is approximately equal to the lasing wavelength of the laser.
In one embodiment, the InGaAs layer 11 is disposed along the optical path propagation direction through the top of the grating layer 5, the width of the InGaAs layer 11 perpendicular to the optical path propagation direction is smaller than the width of the grating layer 5, and the waveguide layer 7 is formed on the InGaAs layer 11 at the middle of the top of the grating layer 5.
In the present embodiment, the InGaAs layer 11 is a highly doped InGaAs layer 11, and the doping concentration is>10 16 cm -3 。
In one embodiment, in order to make the DFB laser 1 and the PD operate normally, the photodetector 2 is not affected by the current applied to the DFB laser 1, so that the two areas grown in the same epitaxy do not cross each other, and the DFB laser 1 and the PD need to be isolated. The ridge waveguide is etched by photolithographic techniques to under the highly doped InGaAs layer 11.
The areas of the InGaAs layer 11 and the waveguide layer 7 not etched by the electrical isolation layer 6 form a conductivity area I, the electrical isolation layer 6 forms a conductivity area II, the conductivity of the conductivity area I is higher than that of the conductivity area II, and the conductivity area I is located at two sides of the conductivity area II along the propagation direction of the optical path. The high doped InGaAs layer 11 has a high conductivity due to the presence of a large amount of ions, so that the high conductivity regions on both sides and the low conductivity region etched in the middle form a series-parallel circuit.
In this embodiment, the electrical isolation layer 6 has a resistance of 3KΩ -5KΩ.
In one embodiment, the waveguide layer 7 is formed by etching a ridge waveguide structure for transmitting light waves on the wafer. The laser mode field is confined within the waveguide by a refractive index difference with the air on both sides.
In one embodiment, the electrode layer 8 is made of Au material. In the process, gold (Au) is plated on the upper and lower surfaces of the whole wafer to supply an operating current to the DFB laser 1.
In this embodiment, in one embodiment, the electrode layer 8 covers the surface of the waveguide layer 7, and covers the surface of the grating layer 5 except for the regions of the grating layer 5 on the surfaces of the electrically insulating layer 6 and the gas detection grooves 10. The bottom of the basal layer is also plated with an electrode layer.
In one embodiment, the two end faces of the DFB laser 1 are both provided with a coating film 9, and the two end faces refer to the end faces of the light path from which the light is emitted and incident, wherein the left end face is coated with a high reflection coating (HRcoating), typically more than 95%, and the right side of the PD is coated with an anti-reflection coating (arccoating), i.e., an anti-reflection coating, typically 0.1%. The HR coating can increase the optical feedback of the DFB laser 1, and the AR coating can emit light which enters the PD from the waveguide and is converted into an electric signal as much as possible, so that the light reflected back to the PD is prevented from influencing the absorbed optical power.
In one embodiment, at the end of the waveguide near the HR coating, during fabrication, the waveguide is etched by etching to form a gas detection trench 10 to a depth above the grating layer 5 without gold plating. Under the condition that the light-emitting power and the lasing wavelength of the laser are not affected, the gas to be detected can interact with the light waves in the waveguide, and the light reflected by the HR end is absorbed by the gas in the ridge waveguide and finally transmitted into the PD by the waveguide. Different optical powers are formed at different gas concentrations and are converted into different optical signals by the photodetector 2.
In one embodiment, the etching of the gas detection trenches 10 is performed on a conventional laser chip using focused ion beam exposure techniques. In particular, the gas groove is etched on one side of the high-reflection coating of the conventional laser.
The feasibility and reliability of the device are tested, and the comparison and analysis experimental results are as follows:
the monolithically integrated gas detection device provided by the embodiment of the invention is compared with the current detection equipment. The main performance indexes of the two devices, including lasing wavelength, gas detection accuracy and sensitivity, are tested by using a standard test method. Test results show that under the same gas concentration, the monolithic integrated gas sensor provided by the invention has accurate wavelength and sensitive concentration detection, and the preparation process is simpler and lower in cost than the traditional method.
The above description of a photonic integrated on-chip methane sensor provided by the present invention has been provided in detail, and specific examples are applied herein to illustrate the principles and embodiments of the present invention, and the above examples are only for helping to understand the method and core ideas of the present invention; meanwhile, as those skilled in the art will vary in the specific embodiments and application scope according to the idea of the present invention, the present disclosure should not be construed as limiting the present invention in summary.
In this document, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
Claims (10)
1. The photonic integrated on-chip methane sensor is characterized by comprising a wafer, wherein the wafer comprises a substrate layer, an active region, a grating layer, an InGaAs layer, a waveguide layer, an electric isolation layer and a gas detection groove; the active region, the grating layer, the InGaAs layer and the waveguide layer extend outwards in sequence along a first direction of the substrate layer, wherein the first direction is perpendicular to the light path propagation direction; the wafer is provided with a high-reflection film on the initial end face along the light path propagation direction and an antireflection film on the final end face;
the electric isolation layer extends outwards along the first direction of the grating layer, the waveguide layer and the InGaAs layer are not arranged in the electric isolation layer, and the electric isolation layer is close to the end face position of the antireflection film along the light path propagation direction;
the gas detection groove extends outwards along the first direction of the grating layer, the waveguide layer and the InGaAs layer are not arranged in the gas detection groove, and the gas detection groove is close to the end face position of the high-reflection film along the light path propagation direction; the gas detection groove and the electric isolation layer do not cover the edge areas of the InGaAs layer and the waveguide layer;
the surface of the wafer is provided with an electrode layer;
the high-reflection film to the electric isolation layer region form a DFB laser, and the electric isolation layer to the antireflection film region form a photoelectric detector.
2. The photonic integrated on-chip methane sensor of claim 1, wherein the InGaAs layer is disposed through the top of the grating layer along the direction of propagation of the optical path, wherein the width of the InGaAs layer perpendicular to the direction of propagation of the optical path is smaller than the width of the grating layer and is located at a middle position of the top of the grating layer, and wherein the waveguide layer is formed over the InGaAs layer.
3. The photonic integrated on-chip methane sensor of claim 1, wherein the electrode layer covers a surface of the waveguide layer and covers a surface of the grating layer other than the surface grating layer region of the electrically isolated layer and the gas detection cell.
4. The photonic integrated on-chip methane sensor of claim 1, wherein the active region comprises, from bottom to top, a buffer layer, a lower confinement layer, a multiple quantum well, and an upper confinement layer using a iii-v quaternary compound semiconductor material; the quantum well exists in the region, and the upper and lower energy level particle number inversions are formed in the active region.
5. The photonic integrated on-chip methane sensor of claim 1, wherein the grating layer is formed using a secondary epitaxy, comprising the steps of:
after an active region is formed by one-time epitaxy, holographic exposure is carried out on the surface of the active region, and a zero-order grating is prepared;
and carrying out secondary epitaxy by using photoetching, wherein the whole zero-order grating layer integrates a first-order grating, and the difference between the Bragg wavelength and the lasing wavelength of the DFB laser is smaller than a given threshold value.
6. The photonic integrated on-chip methane sensor of claim 1, wherein the InGaAs layer and waveguide layer regions not etched by the electrical isolation layer form a conductivity region I, the electrical isolation layer forms a conductivity region II, the conductivity of the conductivity region I is higher than the conductivity region II, and the conductivity region I is located on both sides of the conductivity region II along the propagation direction of the optical path, forming a series-parallel circuit.
7. The photonic integrated on-chip methane sensor of claim 1, wherein the electrical isolation layer has a resistance of 3kΩ -5kΩ.
8. The photonic integrated on-chip methane sensor of claim 1, wherein the waveguide layer employs a ridge waveguide.
9. The photonic integrated on-chip methane sensor of claim 1, wherein the electrode layer is made of Au material.
10. The photonic integrated on-chip methane sensor of claim 1, wherein the substrate is a iii-v compound semiconductor material.
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