A laser for gas or smoke detection and a method of manufacturing and use thereof

Abstract

The application relates to the fields of semiconductor optoelectronic technology and micro-electro-mechanical system technology, and particularly relates to a laser for gas or smoke detection and a preparation method and application thereof. The laser comprises a light source part; and a hollow sacrifice layer, an upper layer DBR and a control electrode which are sequentially formed on the light source part, wherein the hollow sacrifice layer and the upper layer DBR define a gas microcavity for collecting a to-be-detected gas or smoke, a central region thickness of the gas microcavity changes based on a voltage applied by the control electrode, and wherein the laser outputs a wavelength corresponding to a concentration of the to-be-detected gas or smoke in response to a change of an average refractive index of the gas microcavity caused by the to-be-detected gas or smoke collected by the gas microcavity. The laser for gas or smoke detection has at least the advantages of high sensitivity, long service life, fast response, miniaturization, strong universality and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the fields of semiconductor optoelectronics and micro-electro-mechanical systems, and in particular to a laser for gas or smoke detection and a preparation method and application thereof. BACKGROUND

[0002] In industrial production and daily life, it is particularly important to detect and warn some gases and smokes, especially toxic, flammable and explosive gases and smokes. Early and accurate warning can minimize accidents and protect people's lives and property safety in production and life. Currently, the market's smoke and gas detectors mainly include infrared absorption type, semiconductor adsorption type, catalytic combustion type and radioactive ion type detectors. These detectors mainly use gas-sensitive materials to absorb, chemically react with specific gases and block radioactive particles, or have poor stability and are greatly affected by the environment; or have low precision and are difficult to detect low-concentration gases and smokes; or can only detect specific gases, which limits their application; or have radioactivity, which is generally safe.

[0003] Therefore, the detection of a wide range of and highly sensitive small-concentration gases or smokes with strong universality has become a focus. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a laser for gas or smoke detection and a preparation method and application thereof. Through the technical solution of the present application, a wide-range and non-selective gas or smoke concentration detection can be achieved, effectively solving the problem of high-sensitivity and wide-range integrated chip detection, and solving the problems of poor stability, low precision, only detecting specific gases and having radioactivity of existing gas or smoke detectors. Compared with traditional optical gas detectors such as fiber gas detectors, the laser does not need external light source input, can generate laser with wavelength changing with gas concentration by itself, and is conducive to the simplification and miniaturization of the overall structure.

[0005] Specifically, according to a first aspect of the present application, a laser for gas or smoke detection is provided, which comprises: a light source part; and a hollow sacrificial layer, an upper layer DBR and a control electrode formed in sequence on the light source part, wherein the hollow sacrificial layer and the upper layer DBR define a gas microcavity for collecting a to-be-detected gas or smoke, a central region thickness of the gas microcavity changes based on a voltage applied by the control electrode, and wherein the laser outputs a wavelength corresponding to a concentration of the to-be-detected gas or smoke in response to a change in average refractive index of the gas microcavity caused by the to-be-detected gas or smoke collected by the gas microcavity.

[0006] In the embodiment of the present application, the optical cavity length of the laser is changed based on the change of the average refractive index of the gas microcavity to output a wavelength corresponding to the concentration of the gas or smoke to be detected; the thickness of the central region of the gas microcavity is inversely proportional to the detection concentration of the gas or smoke to be detected.

[0007] In the embodiment of the present application, the hollow sacrificial layer is formed by spin coating photoresist on the light source portion and being partially etched; the initial thickness of the gas microcavity depends on the thickness of the photoresist, and the thickness of the photoresist is changed based on the dilution ratio of the photoresist.

[0008] In the embodiment of the present application, the light source portion includes a lower DBR, an active region, an oxidation confinement layer, an intermediate DBR, and a passivation layer grown in sequence on a GaAs substrate; a first electrode sputtered on the back surface of the GaAs substrate and a second electrode sputtered on the passivation layer, the photoresist is spin coated on the second electrode, and the second electrode is used for current injection of the laser.

[0009] In the embodiment of the present application, the passivation layer, the second electrode, and the control electrode each include a light-emitting hole, wherein the diameter of the light-emitting hole of the passivation layer is smaller than the diameter of the mesa of the light source portion, and the diameter of the light-emitting hole of the second electrode is smaller than the diameter of the light-emitting hole of the passivation layer.

[0010] In the embodiment of the present application, the first electrode and the second electrode each include a Ti / Au material system, and the second electrode includes a metal with hard texture and stable chemical properties; the upper DBR serves as a cantilever beam of the gas microcavity and includes a multilayer dielectric material including a low-stress, high-refractive-index-contrast material system; the passivation layer includes a SiO2 passivation layer.

[0011] In the embodiment of the present application, the photoresist includes polyimide, and the dilution ratio of the photoresist is adjusted by a photoresist diluent, and the photoresist diluent includes an organic solvent.

[0012] According to a second aspect of the present application, a preparation method of a laser for gas or smoke detection is provided, comprising the following steps: step S1: sequentially epitaxially growing a lower DBR, an active region, an oxidation confinement layer and an intermediate DBR on a GaAs substrate by metal organic chemical vapor deposition or molecular beam epitaxy to obtain an epitaxial wafer; step S2: photoetching and etching a mesa, and performing lateral wet nitrogen oxidation around the mesa to form an oxidation confinement hole for confining light field and current; step S3: growing a passivation layer, photoetching and etching a light-emitting hole of the passivation layer, sputtering a second electrode and photoetching and etching a light-emitting hole of the second electrode, and making the light-emitting hole of the passivation layer smaller than the diameter of the mesa and the light-emitting hole of the second electrode smaller than the light-emitting hole of the passivation layer to form a nested structure, thereby completing the preparation of a light source part, and finally sputtering a first electrode on the back of the GaAs substrate; step S4: using a spin coater to spin coat photoresist on the second electrode as a sacrificial layer; step S5: growing a plurality of pairs of upper DBRs on the sacrificial layer, the upper DBRs serving as cantilever beams of a gas microcavity at the same time; step S6: photoetching and sputtering Ni on the upper DBRs to form a control electrode, stripping a microcavity shape of the gas microcavity, and using the microcavity shape as an etching mask to perform RIE patterned etching on the upper DBRs to form the gas microcavity; step S7: photoetching and etching a light-emitting hole of the control electrode; and step S8: removing the photoresist of the gas microcavity by using oxygen plasma etching, thereby completing the preparation of the laser for gas or smoke detection.

[0013] In the embodiments of the present application, in step S1, the etching solution of the epitaxial wafer is CH3OH:H3PO4:H2O2:H2O=1.5~3:0.5~1.5:0.5~1.5:4.5~5.5; in step S3, the passivation layer etching solution is HF:NH4F:H2O=2~4ml:5~7mg:9~11ml; and in step S6, the etching gas of the upper DBRs is CHF3:Ar=80~120sccm:8~12sccm, and the Ni etching solution is HNO3:H2O=0.5~1.5:0.5~1.5.

[0014] According to a third aspect of the present application, the laser for gas or smoke detection is applied in the field of gas or smoke detection, comprising:

[0015] obtaining a first wavelength change of the laser for gas or smoke detection for a plurality of known concentrations of a to-be-detected gas or smoke;

[0016] obtaining a linear relationship between the wavelength change and the concentration of the to-be-detected gas or smoke based on the first wavelength change and the known concentrations; and

[0017] The laser used for gas or smoke detection obtains a second wavelength change for a test gas or smoke of unknown concentration, and the concentration of the test gas or smoke of unknown concentration is determined based on the second wavelength change and the linear relationship.

[0018] This invention proposes a laser for gas or smoke detection, its fabrication method, and its application. The laser for gas or smoke detection utilizes the cavity length and refractive index sensitivity of an FP cavity to achieve high sensitivity, long lifetime, fast response, miniaturization, and non-selective gas and smoke detection, offering at least the following advantages:

[0019] 1. Non-selective gas and smoke concentration detection, high sensitivity, long lifespan, fast response, and small size;

[0020] 2. It can generate laser light with wavelength that varies with gas concentration without the need for external light source input, which is beneficial for the simplification and miniaturization of the overall structure;

[0021] 3. By using a polyimide sacrificial layer, the initial thickness of the gas microcavity can be adjusted by different dilution ratios. Furthermore, the thickness of the central region of the gas microcavity can be controlled by control electrodes, thereby dynamically regulating the laser's responsivity and detection range.

[0022] 4. The upper DBR serves not only as a reflector but also as a cantilever beam, avoiding the cumbersome process of fabricating a cantilever beam separately in traditional structures, while simplifying the manufacturing process.

[0023] 5. The laser is fabricated using a single-wafer deposition-etching process, which has the advantages of simple fabrication process and flexible customization of parameters compared to double-wafer bonding and traditional single-wafer epitaxial structures and processes. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0025] Figure 1 A three-dimensional schematic diagram of a laser for gas or smoke detection provided in an embodiment of the present invention;

[0026] Figure 2 for Figure 1 An exploded view of a laser used for gas or smoke detection is shown.

[0027] Figures 3-8 For preparation Figures 1-2Cross-sectional schematic diagrams of various stages of the laser for gas or smoke detection are shown, wherein:

[0028] Figure 3 A cross-sectional schematic diagram of the light source portion is shown, wherein the etching of the mesa, oxidation, growth of the passivation layer and etching of the light hole, sputtering of the Ti / Au second electrode and peeling of the light hole, and sputtering of the backside first electrode have been completed;

[0029] Figure 4 The light source portion and the sacrificial layer are shown;

[0030] Figure 5 The light source portion, the sacrificial layer and the upper DBR are shown;

[0031] Figure 6 The light source portion, the sacrificial layer, the upper DBR and the control electrode are shown;

[0032] Figure 7 The light source portion, the sacrificial layer, the upper DBR, the control electrode and the light hole formed on the control electrode are shown;

[0033] Figure 8 The laser for gas or smoke detection prepared is shown;

[0034] Figure 9 A flow chart of the method for preparing the laser for gas or smoke detection provided by the embodiments of the present application is shown;

[0035] Figure 10 The laser for gas or smoke detection provided by the embodiments of the present application tests the response of water mist particles;

[0036] Figure 11 The laser for gas or smoke detection provided by the embodiments of the present application tests the response of ethanol gas, which is almost linear with the gas concentration;

[0037] Figure 12 The laser for gas or smoke detection provided by the embodiments of the present application tests the response of carbon tetrachloride gas, which is almost linear with the gas concentration;

[0038] Figure 13 The laser for gas or smoke detection provided by the embodiments of the present application tests the response of acetone gas, which is almost linear with the gas concentration;

[0039] Figure 14 A graph showing the relationship between different microcavity thicknesses and responsivity when the laser for gas or smoke detection tests ethanol gas. DETAILED DESCRIPTION

[0040] In order to make the objects, technical solutions and advantages of the present application clearer, the following further describes the embodiments of the present application in detail with reference to the accompanying drawings and in conjunction with specific embodiments.

[0041] It should be noted that all the expressions of "first" and "second" in the embodiments of the present application are used to distinguish two same-named different entities or different parameters. It can be seen that "first" and "second" are only for the convenience of description and should not be understood as a limitation on the embodiments of the present application. The subsequent embodiments will not be described one by one.

[0042] As described above, for gas or smoke detection, the existing detector has the problems of poor universality and poor stability. Based on this, the present application provides a laser for gas or smoke detection and a preparation method and application thereof. The laser comprises, from bottom to top, a laser light source, a gas microcavity, an upper DBR and a control electrode. The gas microcavity is used to collect gas or smoke, the resonance phase of the gas microcavity is changed, and then the output wavelength of the laser is controlled. Compared with the traditional gas or smoke detector, the laser of the present application has the characteristics of high sensitivity, high response speed, high linearity, non-selective detection of gas or smoke, and the response and detection range can be changed by an external control voltage. The preparation method of the laser uses a single deposition-etching method, is compatible with semiconductor process, and has high integration and small volume.

[0043] Specifically, according to the first aspect of the present application, a laser 100 for gas or smoke detection is provided. As shown in Figure 1 、 Figure 2 and Figure 8 The laser 100 for gas or smoke detection comprises: a light source part 120; and a hollow sacrificial layer 130, an upper DBR 11 and a control electrode 12 formed in sequence on the light source part 120, wherein the hollow sacrificial layer 130 and the upper DBR 11 define a gas microcavity 8 for collecting the to-be-detected gas or smoke, the center region thickness of the gas microcavity 8 is changed based on the voltage applied by the control electrode 12, and wherein the laser 100 outputs a wavelength corresponding to the concentration of the to-be-detected gas or smoke in response to the change of the average refractive index of the gas microcavity 8 caused by the to-be-detected gas or smoke collected by the gas microcavity 8.

[0044] In the embodiments of the present application, the laser 100 can be a VCSEL, the optical cavity length of which is changed based on the change of the average refractive index of the gas microcavity 8 to output a wavelength corresponding to the concentration of the to-be-detected gas or smoke. In addition, the center region thickness of the gas microcavity 8 is inversely proportional to the detection concentration of the to-be-detected gas or smoke.

[0045] Specifically, the laser 100 has the gas microcavity 8 for collecting ambient gas or smoke. The refractive index difference of different gas or smoke causes the average refractive index of the gas microcavity 8 to change, and in turn changes the equivalent optical cavity length of the F-P cavity of the laser 100, so as to realize the change of the wavelength, and the laser 100 can detect multiple gas or smoke without gas selectivity. The minimum concentration and the maximum concentration of the detection can also be dynamically adjusted by designing the thickness of the gas microcavity 8, which solves the problem that the detection range of the conventional gas or smoke detector is relatively fixed. Since no chemical reaction and physical adsorption are involved, the response time is fast, the service life is long, the volume is small, the power consumption and heat generation are small, and the overall power consumption is about 50 mW.

[0046] Since the lasing wavelength of the F-P cavity is extremely sensitive to the cavity length and the average refractive index in the cavity, a change of tens of nanometers in the cavity length can cause a change of nanometers in the wavelength. The laser 100 for gas or smoke detection can achieve extremely high sensitivity in application. Since the two-dimensional area of the gas microcavity 8 is very small, about hundreds of microns, the response speed of the laser 100 is improved and the device is miniaturized. Therefore, the laser 100 can realize faster response to the concentration of gas or smoke, avoiding the low response speed caused by the large gas microcavity and slow gas diffusion speed. At the same time, by controlling the voltage applied by the electrode 12 to adjust the thickness of the gas microcavity 8, the sensitivity and detection range of the laser 100 can be flexibly adjusted, making it more widely applicable. For example, adjusting to a thicker gas microcavity 8 to accumulate a larger phase difference to detect smaller concentrations of gas or smoke; and adjusting to a thinner gas microcavity 8 to detect a larger range of concentrations.

[0047] The hollow sacrificial layer 130 is formed after the photoresist is spin-coated on the light source portion 120 to form the sacrificial layer 9, and the sacrificial layer 9 is partially etched. The initial thickness of the gas microcavity 8 depends on the thickness of the photoresist, and the thickness of the photoresist changes based on the dilution ratio of the photoresist. In one embodiment, the photoresist can include but is not limited to a photoresist of model 5214. In another embodiment, the photoresist can include but is not limited to a polyimide, such as but not limited to a polyimide of model JSR-5100. The initial thickness of the gas microcavity 8 can be changed by adjusting the concentration of the photoresist by adding different proportions of diluent, thereby changing the free spectral range (FSR) of the gas microcavity 8. Based on this, lasers for different gas or smoke can be prepared to improve versatility. The dilution ratio of the photoresist can be adjusted by a photoresist diluent. The photoresist diluent includes an organic solvent. In one embodiment, the photoresist diluent includes at least one of chlorobenzene, toluene, carbon tetrachloride. In addition, the two-dimensional size of the gas microcavity 8 is hundreds of microns, which greatly reduces the volume of the laser 100.

[0048] In general, in the preparation stage of the laser 100, the gas microcavity 8 of a predetermined initial thickness can be manufactured by adjusting the dilution ratio of the photoresist, so as to obtain a predetermined free spectral range of the gas microcavity 8. After the laser 100 is prepared, the thickness of the central region of the gas microcavity 8 can be adjusted by applying an external voltage through the control electrode 12. For example, the upper DBR 11 acting as a cantilever beam can be deformed under the external voltage (e.g. a depression is generated in the center of the cantilever beam), so as to change the thickness of the central region of the gas microcavity 8 under the condition of a certain glue thickness, thereby adjusting the minimum concentration and the maximum concentration of the detection.

[0049] Further referring to Figure 8 , the light source part 120 can include, sequentially grown on a GaAs substrate, the lower DBR 2, the active region 3, the oxidation confinement layer 6, the intermediate DBR 7, the passivation layer 4; the first electrode 1 sputtered on the back of the GaAs substrate and the second electrode 5 sputtered on the passivation layer 4, and the photoresist is spin-coated on the second electrode 5, and the second electrode 5 is used for current injection of the laser 100. The passivation layer 4, the second electrode 5 and the control electrode 12 each include a light emitting hole, wherein the diameter of the light emitting hole 4a of the passivation layer 4 is smaller than the diameter of the mesa F (shown in Figure 3 ) of the light source part 120, and the diameter of the light emitting hole 5a of the second electrode 5 is smaller than the diameter of the light emitting hole 4a of the passivation layer 4, so as to form a nested structure, through which the passivation layer 4 can form the effect of side insulation, and at the same time the metal can realize current injection on the top of the mesa F. In addition, in the present application, the gas microcavity 8 generally surrounds the area where the mesa F is located, that is, surrounds the light emitting hole 4a and the light emitting hole 5a.

[0050] The laser 100 can be used for a laser light source of a GaAs material system, and the wavelength includes but is not limited to 1060 nm. The first electrode 1 and the second electrode 5 can each include a Ti / Au material system. The second electrode 5 can also act as a mask during the manufacturing process, so the second electrode 5 can use a metal with a relatively hard texture and stable chemical properties, including but not limited to nickel (Ni), chromium (Cr), etc. The control electrode 12 can also be referred to as a third electrode, which is used to apply a voltage to adjust the microcavity thickness, determine its static operating point, dynamically change the responsivity and detection range of the detector. The upper DBR 11 forms optical feedback as the upper DBR of the laser 100, which not only acts as a mirror but also acts as a cantilever beam, constituting a structural unit of the gas microcavity 8. The upper DBR 11 includes a plurality of dielectric materials, which include a low-stress, high-refractive-index contrast material system, such as SiO2 / TiO2, SiO2 / Ta2O5. In one embodiment, TiO2 and SiO2 are alternately distributed to realize reflection (i.e. distributed Bragg reflector), and generally TiO2 is used as the first layer and the last layer. The passivation layer 4 includes a SiO2 passivation layer.

[0051] In summary, the laser 100 according to the present application can be simply divided into two parts, i.e. a light source part 120 and a gas microcavity 8. The light source part 120 is prepared by sequentially depositing a sacrificial layer 9, an upper DBR 11 and a control electrode 12, and then patterning and etching the sacrificial layer 9 to form a hollow sacrificial layer 130.

[0052] According to a second aspect of the present application, there is provided a method for preparing a laser for gas or smoke detection. Referring to Figures 3-9 , a method 300 for preparing the laser 100 for gas or smoke detection according to the present application will be described in detail below. The laser 100 is prepared by using a monolithic deposition-etching process.

[0053] As Figure 9 described, the method 300 comprises the following steps:

[0054] Step S1: a lower DBR 2, an active region 3, an oxidation confinement layer 6 and an intermediate DBR 7 are sequentially grown on a GaAs substrate by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE) to obtain an epitaxial wafer, as shown in Figure 3 ;

[0055] Step S2: a mesa F (shown in Figure 3 ) is etched by lithography and etching, and a lateral wet nitrogen oxidation is performed around the mesa F to form an oxidation confinement hole for confining the light field and the current;

[0056] Step S3: a passivation layer 4 is grown, and a light-emitting hole 4a of the passivation layer 4 is etched by lithography and etching, then a second electrode 5 is sputtered, and a light-emitting hole 5a of the second electrode 5 is etched by lithography and etching. The light-emitting hole 4a of the passivation layer 4 is smaller than the diameter of the mesa F’, and the light-emitting hole 5a of the second electrode 5 is smaller than the light-emitting hole 4a of the passivation layer 4, so as to form a nested structure. The preparation of the light source part 120 is completed, and finally a first electrode 1 is sputtered on the back of the GaAs substrate;

[0057] Step S4: a photoresist is spin-coated on the second electrode 5 by using a spin coater and is cured as a sacrificial layer 9, as shown in Figure 4 ;

[0058] Step S5: a plurality of pairs (e.g. 10 pairs or so) of upper DBRs 11 are grown on the sacrificial layer 9, as shown in Figure 5 . The upper DBRs 11 simultaneously serve as cantilever beams of a gas microcavity 8 (shown in Figure 8 );

[0059] Step S6: a control electrode 12 is formed on the upper DBRs 11 by lithography and sputtering of Ni, as shown in Figure 6The microcavity shape of the gas microcavity 8 is formed by stripping, and the upper DBR 11 is subjected to RIE patterned etching by using the control electrode 12 as an etching mask to form the gas microcavity 8;

[0060] Step S7: photoetching and etching the light-emitting hole 12a of the control electrode 12, as shown in FIG. 7B. Figure 7

[0061] Step S8: removing the photoresist of the gas microcavity 8 by using oxygen plasma etching, completing the fabrication of the laser, and obtaining the laser 100 for gas or smoke detection, as shown in FIG. 8. Figure 8

[0062] In step S1, the epitaxial wafer etching solution is CH3OH:H3PO4:H2O2:H2O = 1.5-3:0.5-1.5:0.5-1.5:4.5-5.5; in an embodiment, the epitaxial wafer etching solution is CH3OH:H3PO4:H2O2:H2O = 2:1:1:5.

[0063] In step S3, the passivation layer etching solution is HF:NH4F:H2O = 2-4ml:5-7mg:9-11ml; in an embodiment, the SiO2 etching solution is HF:NH4F:H2O = 3ml:6mg:10ml.

[0064] In step S6, the etching gas of the upper DBR is CHF3:Ar = 80-120sccm:8-12sccm, and the Ni etching solution is HNO3:H2O = 0.5-1.5:0.5-1.5; in an embodiment, the etching gas of the upper DBR is CHF3:Ar = 100sccm:10sccm, and the Ni etching solution is HNO3:H2O = 1:1.

[0065] The preparation method 300 of the laser for gas or smoke detection can realize the preparation of the laser for a wide range of non-selective gas or smoke concentration detection, and the polyimide sacrificial layer, the upper DBR, and the control electrode are sequentially deposited on the light source part of the laser, and then the sacrificial layer is patterned and etched, and the whole is completed by using a single deposition-etching process, and meanwhile, the upper DBR not only serves as a mirror but also as a cantilever beam, avoiding the complicated process of separately fabricating the cantilever beam in the traditional structure. Compared with the double wafer bonding and the traditional single epitaxial structure and process, the preparation process is simple, and the parameters of each part can be flexibly customized.

[0066] According to a third aspect of the present application, the laser for gas or smoke detection is applied in the field of gas or smoke detection. The laser 100 mentioned in the embodiments of the present application can be applied in the field of gas or smoke detection to solve the problems in the prior art. ​​

[0067] In the application of the laser for gas or smoke detection, when the gas or smoke enters the gas microcavity, the optical cavity length (i.e. the physical thickness multiplied by the refractive index) of the laser changes, and then the output wavelength changes. Since one output wavelength change corresponds to one gas or smoke concentration, the output wavelength can be used to detect the concentration of the gas or smoke.

[0068] In the embodiments of the application, the application comprises:

[0069] Obtaining a first wavelength change of the laser for gas or smoke detection for a plurality of known concentrations of the gas or smoke to be measured;

[0070] Obtaining a linear relationship between the wavelength change and the concentration of the gas or smoke to be measured based on the first wavelength change and the known concentrations; and

[0071] Obtaining a second wavelength change of the laser for gas or smoke detection for an unknown concentration of the gas or smoke to be measured, and determining the concentration of the unknown concentration of the gas or smoke to be measured based on the second wavelength change and the linear relationship.

[0072] The application will be further illustrated by the following embodiments:

[0073] When the gas microcavity of the laser for gas or smoke detection of the application collects smoke or water mist, the smoke or water mist changes the average refractive index of the gas microcavity, and the laser outputs different wavelengths. In this way, it can be detected whether the smoke or water mist exists and its concentration. Figure 10 For the laser for gas or smoke detection with a center wavelength of 1060 nm (for example, the laser 100 of the application), the wavelength change is 2 nm in different environments by using deionized water mist instead of smoke particles. Therefore, the laser of the application can be used to detect water mist or smoke, and realize the detection of water mist or smoke, etc. The application of the laser of the application in gas detection will be further explained below.

[0074] Figures 11-13 Examples of the specific application of the laser for gas or smoke detection of the application in gas detection.

[0075] For example, when the gas microcavity collects ethanol gas, the average refractive index in the gas microcavity changes (the higher the concentration of ethanol, the greater the refractive index), thereby increasing the optical cavity length (physical thickness multiplied by refractive index) and causing red shift of the wavelength. Based on this, the gas microcavity of the laser for gas or smoke detection can collect ethanol gas of multiple known concentrations respectively, and for each known concentration, the wavelength is measured by the spectrometer, thereby obtaining the first wavelength change for the ethanol gas of the known concentration. Then, based on the first wavelength change and the known concentration, the linear relationship between the wavelength change and the concentration of the ethanol gas is obtained, for example, the four wavelength change vs. concentration values are output Figure 11 as shown in the curve diagram. Figure 11 In this way, the responsivity, i.e., the slope of the output curve, is the amount of wavelength change divided by the amount of concentration change. Based on this, in actual application, the gas concentration corresponding to any wavelength can be obtained according to the curve Figure 11 , thereby realizing concentration detection of ethanol gas of unknown concentration. That is, in actual application, the laser for gas or smoke detection can collect ethanol gas of unknown concentration, and the wavelength is measured by the spectrometer to obtain the wavelength change, and then the relationship between the wavelength change and the concentration of the ethanol gas is found out, thereby obtaining the concentration of the ethanol gas at this time. Figure 11

[0076] In a similar way, the concentrations of carbon tetrachloride and acetone gas can be obtained, as shown in Figures 12-13 .

[0077] Taking ethanol, carbon tetrachloride and acetone gas as examples, the amount of wavelength change of the laser of the present application is proportional to the concentration of the gas, has good linearity, and has no gas selectivity. The responsivity of ethanol, carbon tetrachloride and acetone is 0.044 nm / percentage, 0.0085 nm / percentage and 0.056 nm / percentage respectively, and has different microcavity thicknesses under different control voltages, i.e., has different responsivities for the same kind of gas.

[0078] As shown in Figure 14 , different gas microcavity thicknesses result in different slopes, i.e., detection responsivity, i.e., different gas concentration changes corresponding to unit wavelength change. As described above, by applying voltage to the control electrode, the gas microcavity thickness can be changed (due to electrostatic attraction), thereby adjusting the responsivity and the detection range to adapt to different environments. The detection range and the responsivity of the laser of the present application are mutually restricted, i.e., large range corresponds to weak responsivity, and strong responsivity corresponds to small range. The thicker the gas microcavity, the smaller the detection range, but the higher the responsivity.

[0079] ​In summary, the application provides a laser for gas or smoke detection and a preparation method and application thereof.

[0080] The technical features of the above embodiments can be combined in any manner, and for the sake of brevity, not all possible combinations of the technical features in the above embodiments are described, however, as long as the combinations of the technical features do not contradict each other, they should be considered within the scope of the present disclosure.

[0081] The above embodiments only express several implementation manners of the application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the application, and these are within the protection scope of the application. Therefore, the protection scope of the patent of the application should be subject to the appended claims.

Claims

1. A laser for gas or smoke detection, characterized in that Comprise: a light source part comprising a lower DBR, an active region, an oxidation confinement layer, an intermediate DBR and a passivation layer grown in sequence on a GaAs substrate; a first electrode sputtered on the back of the GaAs substrate and a second electrode sputtered on the passivation layer, a photoresist spin-coated on the second electrode, the second electrode being used for current injection of the laser; and a hollow sacrificial layer, an upper DBR and a control electrode formed in sequence on the light source part, wherein the hollow sacrificial layer and the upper DBR define a gas microcavity for collecting a gas or smoke to be measured, a central region thickness of the gas microcavity changes based on a voltage applied by the control electrode, and wherein the laser outputs a wavelength corresponding to a concentration of the gas or smoke to be measured in response to a change in average refractive index of the gas microcavity caused by the gas or smoke to be measured collected by the gas microcavity, the hollow sacrificial layer is formed by spin-coating the photoresist on the light source part and being partially etched, an initial thickness of the gas microcavity depends on a thickness of the photoresist, and the thickness of the photoresist changes based on a dilution ratio of the photoresist.

2. The laser of claim 1, wherein, An optical cavity length of the laser changes based on the change in average refractive index of the gas microcavity to output the wavelength corresponding to the concentration of the gas or smoke to be measured; the central region thickness of the gas microcavity is inversely proportional to a detection concentration of the gas or smoke to be measured.

3. The laser of claim 1, wherein, The passivation layer, the second electrode and the control electrode each comprise a light-out hole, wherein a diameter of the light-out hole of the passivation layer is smaller than a diameter of a mesa of the light source part, and a diameter of the light-out hole of the second electrode is smaller than a diameter of the light-out hole of the passivation layer.

4. The laser of claim 1, wherein, The first electrode and the second electrode each comprise a Ti / Au material system, and the second electrode comprises a metal with harder texture and more stable chemical properties; the upper DBR serves as a cantilever beam of the gas microcavity and comprises a multi-layer dielectric material comprising a low-stress, high-refractive-index-contrast material system; the passivation layer comprises a SiO2 passivation layer.

5. The laser of claim 1, wherein, The photoresist comprises polyimide, and the photoresist adjusts the dilution ratio by a photoresist diluent, the photoresist diluent comprising an organic solvent.

6. A method of producing a laser for gas or aerosol detection according to any one of claims 1 to 5, characterized in that Comprise the following steps: Step S1: epitaxially growing a lower DBR, an active region, an oxidation confinement layer and an intermediate DBR in sequence on a GaAs substrate by metal organic chemical vapor deposition or molecular beam epitaxy to obtain an epitaxial wafer; Step S2: photoetching and etching a mesa, performing lateral wet nitridation around the mesa to form an oxidation confinement hole for limiting light field and current; Step S3: growing a passivation layer and photoetching and etching a light-out hole of the passivation layer, then sputtering a second electrode and photoetching and etching a light-out hole of the second electrode, and making the light-out hole of the passivation layer smaller than a diameter of the mesa and the light-out hole of the second electrode smaller than the light-out hole of the passivation layer to form a nested structure, completing fabrication of a light source part, and finally sputtering a first electrode on the back of the GaAs substrate; Step S4: spin coating photoresist on the second electrode as a sacrificial layer using a spin coater and curing; Step S5: growing several pairs of upper DBRs on the sacrificial layer, which simultaneously serve as cantilever beams of a gas microcavity; Step S6: photoetching, sputtering Ni on the upper DBRs to form a control electrode, peeling off a microcavity shape forming the gas microcavity, and then using the microcavity shape as an etching mask to perform RIE patterned etching on the upper DBRs to form the gas microcavity; Step S7: photoetching and etching the light-emitting hole of the control electrode; Step S8: removing the photoresist of the gas microcavity using oxygen plasma etching, and completing the fabrication of the laser for gas or smoke detection.

7. The production method according to claim 6, characterized by, In step S1, the epitaxial wafer etching solution is CH3OH:H3PO4:H2O2:H2O=1.5~3:0.5~1.5:0.5~1.5:4.5~5.5; in step S3, the passivation layer etching solution is HF:NH4F:H2O=2~4ml:5~7mg:9~11ml; in step S6, the etching gas of the upper DBRs is CHF3:Ar=80~120sccm:8~12sccm, and the Ni etching solution is HNO3:H2O=0.5~1.5:0.5~1.

5.

8. Use of a laser as claimed in any one of claims 1-5 for gas or smoke detection, characterized in that, comprising: obtaining a first wavelength change for a plurality of known concentrations of a to-be-measured gas or smoke by the laser for gas or smoke detection; obtaining a linear relationship between the wavelength change and the concentration of the to-be-measured gas or smoke based on the first wavelength change and the known concentrations; and obtaining a second wavelength change for an unknown concentration of the to-be-measured gas or smoke by the laser for gas or smoke detection, and determining the concentration of the unknown concentration of the to-be-measured gas or smoke based on the second wavelength change and the linear relationship.

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