Semiconductor laser chip for gas sensor

Abstract

The invention relates to a semiconductor laser chip (101) comprising: * A substrate (105) comprising: - two side faces (107), - a lower face (109), and - an upper face (108); * at least two semiconductor lasers (102), these two lasers (102) being distributed between the two side faces (102) with a spacing (E) between two adjacent lasers (102), the substrate (101) having a width (l), this width being the distance between the two side faces (107) of the substrate (105), and a thickness (e), this thickness (e) being the distance measured between the lower face (109) and the upper face (108) of the substrate (105) perpendicular to the width (l), the width (l) being less than or equal to 4 times the thickness (e).

Description

Description Title: Semiconductor laser chip for gas sensor Technical field

[0001] The present invention relates to the field of semiconductor lasers, and more particularly to semiconductor laser chips, in particular for gas sensors.

[0002] Generally, semiconductor laser chips are obtained by a complex series of steps of depositing layers on a monocrystalline substrate (also called substrate in the present description) forming a wafer (generally called wafer in English) and by cutting this wafer to obtain laser chips. This deposition of layers is carried out either by liquid or gas phase epitaxy, or by molecular beam on the substrate. The substrate consists of a pure crystal (generally InP or InAs or GaAs or other semiconductor material). A laser unit is generally a parallelepiped portion of the wafer, and is obtained by a series of steps of chemical or physicochemical etching and deposition of materials which may be non-crystalline or crystalline intended to constitute the laser cavity as well as the diffraction grating and structure the laser unit.

[0003] There are different types of semiconductor laser chips, including quantum cascade laser chips, or QCL chips for Quantum Laser Cascade. A quantum cascade laser chip comprises two electrodes for applying an electric field between the two electrodes, a waveguide arranged between the electrodes and a laser unit which corresponds to a structure comprising a gain region formed of several layers which comprise for example an alternation of strata of a first type each defining a quantum barrier and strata of a second type each defining a quantum well, these strata being made up of first and second semiconductor materials, respectively constituting the barriers and the wells. The quantum cascade laser unit further comprises two optical confinement layers arranged on either side of the gain region.The laser unit forms a rod that extends at least partially along the length of the semiconductor laser chip.

[0004] Once the laser chip is manufactured, it is generally cleaved parallel to the bar formed by the laser units on the substrate. This allows the width of the laser chip to be fixed. It is then cleaved perpendicular to the bar to allow the facets that act as a mirror to be made. These cleavages consist of breaking the crystal of the substrate on which the laser units have been deposited along a crystalline axis, that is to say an axis extending over the thickness of the substrate, to obtain a quasi-perfect mirror surface. This breaking is generally carried out by scratching the surface of the substrate containing the laser units and then applying pressure on either side of the scratch so as to break the crystal along this crystalline axis.

[0005] The overall production cost of a semiconductor laser chip is defined in particular by the following equation: Surface area of ​​material used to manufacture a laser chip / Production yield of the semiconductor laser chip x Manufacturing cost of the cleaved laser chip.

[0006] It is understood that: • The surface area of ​​material used is defined by the surface area of ​​material (substrate and deposited layers) used to manufacture the laser chip, • The production yield of the semiconductor laser chip is defined by the ratio of the number of functional laser units to the maximum number of laser units that can be produced on the laser chip, • The manufacturing cost of the cleaved laser chip corresponds to the cost of implementing the process used for the manufacturing of said laser chip.

[0007] Thus, the larger the surface area of ​​material used, and / or the lower the production yield of the semiconductor laser chip, and / or the higher the manufacturing cost of the laser chip.

[0008] In the prior art, laser chips comprising a single laser unit exist. Such semiconductor laser chips have a non-optimized production yield. Indeed, there is only one functional laser unit and the surface area of ​​the semiconductor laser chip is not used to the maximum. In other words, part of the surface area of ​​the laser chip is wasted.

[0009] There are also in the prior art semiconductor laser chips comprising several laser units which are configured for example to each emit a wavelength of their own. For example, document US7826509 describes a laser chip comprising several laser units whose width is typically 2 mm. This geometry is proposed in portable broadband sensors in order to simultaneously detect a large number of chemical compounds. The use of such a material surface is particularly expensive.

[0010] The present invention aims to reduce the overall production cost of a semiconductor laser chip by maximizing the number of laser units on the smallest laser chip obtained by cleaving. Summary

[0011] In this description, the terms chip, laser chip and semiconductor laser chip are used interchangeably, the terms assembly and chip-base assembly are used interchangeably and the terms laser unit and semiconductor laser unit are used interchangeably.

[0012] In this description, certain elements or parameters may be indexed, such as first unit or second unit, as well as first parameter and second parameter, or first criterion and second criterion, etc. In this case, it is a simple indexing to differentiate and name elements or parameters or criteria that are close but not identical. This indexing does not imply a priority of one element, parameter or criterion over another and such names can easily be interchanged without departing from the scope of this description. This indexing does not imply an order in time, for example, to assess this or that criterion.

[0013] The present invention relates to a semiconductor laser chip comprising: • A substrate, in particular cleaved, comprising: o two lateral faces, o a lower face, o an upper face, • at least two semiconductor laser units, these two laser units being distributed between said two lateral faces with a spacing between two neighboring laser units, said substrate having a width, this width being the distance between said two lateral faces of said substrate, and a thickness, this thickness being the distance between the lower face and the upper face of said substrate perpendicular to the width of the substrate, said width being less than or equal to 4 times the thickness of said substrate.

[0014] In one aspect according to the invention, the laser chip is in particular obtained by cleaving the substrate.

[0015] In one aspect according to the invention, the two lateral faces of the substrate are in particular obtained by cleaving said substrate, said substrate being in particular cleaved.

[0016] In one aspect of the invention, the lower face and the upper face are two opposite faces of the substrate. The terms lower and upper are conventions for distinguishing these two faces.

[0017] In one aspect according to the invention, the two side faces are two opposite faces of the substrate.

[0018] By width is meant here the distance between the two lateral faces of the substrate between which the semiconductor laser units are distributed with a spacing between two neighboring laser units, in other words the laser units are arranged in different locations spaced apart by a spacing between two neighboring laser units in the dimension of the width of the substrate.

[0019] By thickness is meant here the distance between the lower face and the upper face of the substrate, said lower face being configured to be placed on a base and the upper face being opposite said lower face.

[0020] By length is meant here the distance between two other faces of the substrate which are each in junction with one of the two lateral faces, the lower face and the upper face of the substrate, and on which the laser units extend at least partially.

[0021] The presence of at least two laser units in the said laser chip makes it possible to exploit almost the entire surface of the laser chip. In other words, very little surface area of ​​the substrate, and therefore of the laser chip, is lost. In fact, the laser units are distributed over the substrate width, a single chip thus comprises several laser units. The production yield of said laser chip is therefore optimized.

[0022] In one aspect of the invention, the width of the laser chip is the same as the width of the substrate.

[0023] In one aspect according to the invention, the substrate has a width less than or equal to 3.5 times the thickness of said substrate, preferably less than or equal to 3 times the thickness of said substrate, preferably less than or equal to 2.5 times the thickness of said substrate, preferably less than or equal to 2 times the thickness of said substrate, preferably less than or equal to 1.5 times the thickness.

[0024] In this way, the material surface used for the production of the laser chip is reduced, which leads to a reduction in the production cost of the laser chip, and the width of the substrate of the semiconductor laser chip is large enough to prevent said laser chip from being damaged during the cleaving step, which can cause the chip to break. This width / thickness ratio of the substrate therefore gives said laser chip sufficient mechanical strength to avoid breakage during the cleaving step. The smallest cleavable laser chip is thus obtained.

[0025] In one aspect according to the invention, the width of the substrate is between 150 pm and 1 mm, preferably between 150 pm and 750 pm, preferably between 150 pm and 500 pm, preferably between 150 pm and 400 pm, preferably between 150 pm and 350 pm, preferably between 150 pm and 300 pm, preferably between 150 pm and 250 pm, preferably between 200 pm and 250 pm, preferably equal to 250 pm.

[0026] In one aspect according to the invention, the thickness of the substrate is between 50 pm and 350 pm, preferably between 75 pm and 300 pm, preferably between 100 pm and 200 pm, preferably between 100 pm and 150 pm, preferably between 120 pm and 150 pm.

[0027] In one aspect according to the invention, the length of the substrate is between 0.5 mm and 5 mm, preferably between 1 mm and 3.5 mm, preferably between 2 mm and 3 mm.

[0028] In one aspect of the invention, the laser chip comprises at least three laser units, these three laser units being distributed between the two lateral faces of the substrate with a spacing between two neighboring laser units. In other words, the at least three laser units are distributed across the width of the substrate. In other words, the at least three laser units are distributed across the width of the laser chip.

[0029] In one aspect of the invention, the laser units are arranged on one of the faces of the substrate.

[0030] In one aspect of the invention, the laser units are arranged on the underside of the substrate. In another aspect of the invention, the laser units are arranged on the upper side of the substrate.

[0031] In another aspect of the invention, the laser units are buried in the substrate. In this aspect of the invention, the laser chip comprises at least one layer of electrically insulating material on either side of the laser units. For example, the insulating material is semi-insulating InP (indium phosphide). The semi-insulating InP is, for example, a so-called doped InP, to which impurities such as iron are added. In this way, the laser units are electrically isolated from each other.

[0032] In one aspect of the invention, the laser units are closer to the upper face of the substrate than to the lower face of the substrate. It is understood here either that the laser units are buried in the substrate closer to the upper face than to the lower face of said substrate, or that the laser units are arranged on the upper face of said substrate of the laser chip.

[0033] In one aspect of the invention, the laser units are closer to the underside of the substrate than to the upper side of said substrate. It is understood here either that the laser units are buried in the substrate closer to the underside than to the upper side of said substrate, or that the laser units are arranged on the underside of the substrate.

[0034] In one aspect of the invention, the laser chip comprises at least two electrodes of different polarity configured to allow the passage of an electric current in at least one laser unit of the laser chip. Said at least two electrodes are configured to be in electrical contact with said at least one laser unit.

[0035] In one aspect according to the invention, the laser chip comprises at least one electrode of positive polarity and at least one electrode of negative polarity, said electrodes being configured to be in electrical contact with at least one laser unit so as to allow the passage of an electric current in said at least one laser unit.

[0036] In one aspect of the invention, at least one electrode of a given polarity is disposed on at least one laser unit.

[0037] In one aspect of the invention, the laser chip comprises as many positive polarity electrodes as it comprises laser units. In other words, each positive electrode is in electrical contact with a separate laser unit. For example, the laser chip comprises one laser unit and one positive polarity electrode, or the chip comprises two laser units and two positive polarity electrodes, or the chip comprises three laser units and three positive polarity electrodes, or the chip comprises N laser units and N positive polarity electrodes.

[0038] In one aspect of the invention, the laser chip comprises as many negative polarity electrodes as it comprises laser units. In other words, each negative electrode is in electrical contact with a separate laser unit. For example, the laser chip comprises one laser unit and one negative polarity electrode, or the chip comprises two laser units and two negative polarity electrodes, or the chip comprises three laser units and three negative polarity electrodes, or the chip comprises N laser units and N negative polarity electrodes.

[0039] In one aspect of the invention, the laser chip includes a positive polarity electrode configured to be in electrical contact with all of the laser units at once.

[0040] In one aspect of the invention, the laser chip includes a negative polarity electrode configured to be in electrical contact with all of the laser units at once.

[0041] In one aspect of the invention, at least one electrode is disposed on the underside of the substrate.

[0042] In one aspect of the invention, all the electrodes of the same polarity are arranged on the same face of the substrate.

[0043] In one aspect according to the invention, the electrodes are configured to be electrically connected with a base, in particular with electrical tracks of a base.

[0044] In one aspect according to the invention, the spacing between two neighboring laser units distributed between the two lateral faces of the substrate is between 10 pm and 150 pm, preferably between 20 pm and 150 pm, preferably between 30 pm and 150 pm, preferably between 30 pm and 150 pm, preferably between 40 pm and 150 pm, preferably between 50 pm and 150 pm, preferably between 75 pm and 125 pm, preferably equal to 100 pm. In other words, in the width of the chip, the spacing between two neighboring laser units is between 75 and 150 pm, preferably between 75 pm and 125 pm, preferably equal to 100 pm. In this way, the spacing between two neighboring laser units is configured so that the electrodes of the same face are not electrically connected to each other.

[0045] In one aspect according to the invention, the spacing between two neighboring laser units distributed between the two lateral faces of the substrate is constant. In other words, when the laser chip comprises N laser units, N being greater than or equal to two, the spacing between a first laser unit and a second laser unit in the width of the substrate is the same as the spacing between said second laser unit and a third laser unit which is the same as the spacing between the N-1th laser unit and the Nth laser unit.

[0046] In one aspect of the invention, the spacing between at least two neighboring laser units distributed between the two lateral faces of the substrate varies. In other words, the spacing between a first laser unit and a second laser unit across the width of the substrate is different from the spacing between said second laser unit and a third laser unit.

[0047] In one aspect of the invention, the electrodes are formed by depositing electrically conductive material on the substrate, in particular a metallic material, configured to be in electrical contact with at least one laser unit. For example, said electrically conductive metallic material is chosen from gold, copper, silver or aluminum.

[0048] In one aspect according to the invention, the substrate comprises at least one semiconductor material of the InP (indium phosphide) or GaAs (gallium arsenide) or GaSb (gallium antimonide) or InAs (indium arsenide) or Silicon type.

[0049] In one aspect of the invention, the laser chip comprises at least one electrically insulating layer, said electrically insulating layer being configured to electrically insulate the laser units arranged on the same face of the substrate from each other. In this way, the laser units are each crossed by an electric current which is specific to them.

[0050] In one aspect according to the invention, the electrically insulating layer is obtained by depositing an electrically insulating material on the substrate. For example, the electrically insulating material is chosen from silicone or rubber.

[0051] In one aspect according to the invention, the electrically insulating layer is arranged between the upper face of the substrate and at least one electrode arranged on said upper face.

[0052] In one aspect according to the invention, the laser chip comprises at least one wall between two electrodes, said wall being covered by said electrically insulating layer. The wall makes it possible to flatten the surface of the laser chip, in particular when the laser units are on the upper or lower face of the substrate.

[0053] In one aspect of the invention, the laser chip is a quantum cascade laser chip. In other words, the at least two laser units are quantum cascade laser units.

[0054] In one aspect of the invention, the laser units are configured to emit light radiation in pulsed mode. This makes it possible in particular to reduce the energy consumption for powering said laser units compared to a continuous mode. The efficiency of the laser units (optical energy / electrical energy required) is therefore improved.

[0055] In one aspect according to the invention, at least one laser unit is configured to emit light radiation at a wavelength in the infrared, preferably in the mid-infrared.

[0056] In one aspect according to the invention, at least one laser unit is configured to emit light radiation in a wavelength range between 3 and 15 microns, preferably between 4 and 10 microns.

[0057] In one aspect of the invention, all of the laser units of the laser chip are configured to emit light radiation at a same wavelength.

[0058] In one aspect of the invention, at least two laser units of the laser chip are configured to emit light radiation at different wavelengths.

[0059] In one aspect according to the invention, the laser chip comprises N laser units, N being greater than or equal to two, at least one of said laser units being configured to be crossed by an electric current sufficiently weak to allow heat to be generated without emitting light radiation, and at least one other laser unit being configured to be crossed by an electric current sufficiently strong to generate light radiation.

[0060] In one aspect of the invention, the laser chip comprises at least N laser units, N being greater than or equal to two, at least two laser units being configured to emit a light radiation at a given wavelength under different atmospheric conditions, especially at different temperatures.

[0061] In one aspect according to the invention, the laser chip is configured to operate only the laser unit(s) emitting light radiation at the wavelength given to the atmospheric conditions surrounding it, in particular to the temperature surrounding it.

[0062] The invention also relates to a chip-base assembly comprising: • At least one semiconductor laser chip as described above, • A base on which the said laser chip is mounted.

[0063] In other words, the chip-base assembly comprises a laser chip as described above, said chip being arranged on the base. In other words, the laser chip and the base are superimposed.

[0064] In one aspect of the invention, the lower face of the substrate of the laser chip faces the base. In other words, the lower face of the substrate of the laser chip is arranged on the base and the upper face of the substrate is opposite the base.

[0065] In one aspect according to the invention, the electrode disposed on the lower face of the substrate is disposed on the base.

[0066] In one aspect of the invention, the laser chip is fixed to the base, for example by welding or gluing.

[0067] In one aspect according to the invention, the base comprises at least one base comprising a material having heat dissipation properties chosen from copper, AIN.

[0068] In one aspect according to the invention, the base comprises a thermal management element, in particular a Pelletier element.

[0069] The base plate's function is, in particular, the thermal management of the laser chip. It allows for good heat dissipation.

[0070] In one aspect according to the invention, the base of the base is parallelepiped in shape.

[0071] In one aspect of the invention, the base of the base comprises an upper face, a lower face, and two side faces, the upper face being opposite the lower face. The terms lower and upper are conventions for distinguishing these two faces.

[0072] In one aspect of the invention, the laser units of the laser chip are closer to the underside of the laser chip substrate, and therefore closer to the base than to the upper side of the laser chip substrate.

[0073] In one aspect of the invention, the laser units of the laser chip are closer to the upper face of the laser chip substrate than to the lower face of the laser chip substrate, and therefore to the base.

[0074] In one aspect according to the invention, the base comprises at least two electrical tracks of different polarity, each of the electrical tracks being configured to be in electrical contact with at least one electrode of the same polarity of the laser chip.

[0075] In one aspect of the invention, the electrical tracks are configured to be in electrical contact with at least one laser unit.

[0076] In one aspect according to the invention, said at least one laser unit is configured to be in electrical contact with at least two electrodes of the laser chip, said electrodes being electrically connected to the electrical tracks. In this way, the laser units are configured to be in electrical contact with the base, more particularly with said electrical tracks of the base.

[0077] In one aspect of the invention, the base comprises as many electrical tracks of a given polarity as the laser chip comprises electrodes of the same polarity. In other words, the base comprises as many electrical tracks of positive polarity as the laser chip comprises electrodes of positive polarity, and the base comprises as many electrical tracks of negative polarity as the chip comprises electrodes of negative polarity.

[0078] In one aspect of the invention, the base includes a positive polarity electrical track configured to be in electrical contact with all positive polarity electrodes of the laser chip.

[0079] In one aspect of the invention, the base includes a negative polarity electrical track configured to be in electrical contact with all negative polarity electrodes of the laser chip.

[0080] In one aspect of the invention, each of the electrical tracks is arranged on the base of the base.

[0081] In one aspect according to the invention, each of the electrical tracks is arranged on the same face of the base of the base, in particular on the upper face of said base.

[0082] In one aspect of the invention, the electrical tracks are formed by depositing an electrically conductive material, in particular a metal deposit on the base.

[0083] In one aspect of the invention, the chip-base assembly comprises at least one electrical connector configured to electrically connect an electrical track of the base to at least one electrode of the chip. Said electrical connector is for example a wire or a plate comprising an electrically conductive material, in particular gold, copper, aluminum or silver.

[0084] In one aspect according to the invention, the electrical connector is connected on the one hand to at least one electrode of a given polarity of the laser chip via an electrical contact zone, in particular a weld or a bond, on the other hand to at least one electrical track of the base of the same polarity as said electrode. The electrical contact zone comprises by example an electrically conductive material such as gold, copper, aluminum, silver.

[0085] In one aspect of the invention, the electrical contact area at least partially covers the electrode of the laser chip.

[0086] In one aspect according to the invention, the electrical contact zone has a diameter less than or equal to 100 pm, preferably less than or equal to 90 pm, preferably less than or equal to 80 pm, preferably less than or equal to 70 pm, preferably less than or equal to 60 pm, preferably less than or equal to 60 pm, preferably less than or equal to 50 pm, preferably less than or equal to 25 pm, preferably less than or equal to 10 pm.

[0087] In one aspect of the invention, an electrical track is configured to be in electrical contact with at least one electrode by a junction zone. By junction zone, here is meant a junction zone in which the contact between the electrical track and the electrode is physical. In other words, the electrode and the electrical track are superimposed on each other. In this case, it is not necessary to use an electrical connector for the at least one electrode and the electrical track to be in electrical contact.

[0088] In one aspect according to the invention, the laser chip comprises N laser units, N being greater than or equal to two, at most N-1 of said laser units being electrically connected with the electrical tracks of the base. In other words, at least one laser unit is not electrically connected to the electrical tracks of the base. Thus, only the most efficient laser units are in electrical contact with the base.

[0089] In one aspect according to the invention, the laser chip comprises N laser units, N being greater than or equal to two, at least one laser unit among said N laser units being configured to be crossed by an electric current sufficiently weak to allow heat to be generated without emitting light radiation, and at least one other laser unit being configured to be crossed by an electric current sufficiently strong to generate light radiation.

[0090] In one aspect according to the invention, the chip comprises N laser units, N being greater than or equal to two, at least one of said laser units being configured to emit light radiation at a wavelength different from the other laser units.

[0091] In one aspect of the invention, the chip-socket assembly comprises at least two chips as described above.

[0092] In one aspect according to the invention, the chip-base assembly comprises at least one laser chip comprising N laser units, N being greater than or equal to two, at least one of said laser units being configured to be crossed by an electric current sufficiently weak to allow heat to be generated without emitting light radiation, and at least one other laser unit being configured to be crossed by an electric current sufficiently strong to generate light radiation.

[0093] In one aspect according to the invention, the chip-base assembly comprises at least one laser chip comprising at least N laser units, N being greater than or equal to two, at least two laser units being configured to emit light radiation at a given wavelength under different atmospheric conditions, in particular at different temperatures.

[0094] In one aspect of the invention, the chip-base assembly is configured to operate only the laser unit(s) emitting light radiation at the wavelength given to the atmospheric conditions surrounding it, in particular to the temperature surrounding it. In this way, the chip-base assembly operates the laser unit most suited to the atmospheric conditions, for example to the temperature.

[0095] The present invention also relates to a gas sensor comprising: • A cell forming a resonator, comprising a gas inlet duct, a gas outlet duct and at least one opening called a laser inlet, • At least one chip-base assembly as described above comprising at least two laser units, at least one of said two laser units being configured to emit, into the cell, light radiation having a wavelength whose value is specifically adapted to the excitation of a gas to be detected, such that an interaction between the light radiation and the gas to be detected contained in the cell induces the generation of a signal characteristic of the presence of said gas at a resonance frequency of the cell, and • A signal detection device.

[0096] In one aspect of the invention, the gas sensor comprises: • A cell forming an optical resonator, comprising a gas inlet duct, a gas outlet duct and at least one opening called a laser inlet, • At least one chip-base assembly as described above comprising at least two laser units, at least one of said two laser units being configured to emit, into the cell, light radiation having a wavelength whose value is specifically adapted to the excitation of a gas to be detected, such that an interaction between the light radiation and the gas to be detected contained in the cell induces the generation of an optical signal characteristic of the presence of said gas at a resonance frequency of the cell, and • A signal detection device.

[0097] In one aspect of the invention, the gas sensor comprises a focusing or collimating device, in particular a lens configured to collimate or focus the light radiation coming from said at least one laser unit.

[0098] In another embodiment according to the invention, the gas sensor according to the invention is a photoacoustic gas sensor which comprises the characteristics described in document FR3084745.

[0099] In this embodiment, the gas sensor comprises: • A cell forming an acoustic resonator, comprising a gas inlet duct, a gas outlet duct and at least one opening called a laser inlet; • At least one chip-base assembly as described above comprising at least two laser units, at least one of said two laser units being configured to emit, into the cell, light radiation having a wavelength whose value is specifically adapted to the excitation of a gas to be detected, such that an interaction between the light radiation and the gas to be detected contained in the cell induces the generation of acoustic waves at a resonance frequency of the cell; and • At least one detection microphone arranged in a chimney opening into the cell.

[0100] In another aspect according to the invention, the chip-base assembly is placed directly in front of the laser input of the cell, without interposition of optical focusing or collimation elements.

[0101] In one aspect of the invention, the chip-base assembly is disposed inside the sensor cell.

[0102] In another aspect according to the invention, the photoacoustic gas sensor comprises a focusing or collimating device, in particular a lens configured to collimate or focus the light radiation coming from said at least one laser unit.

[0103] In one aspect of the invention, the sensor comprises a power supply circuit configured to operate the laser source in pulsed mode. This makes it possible in particular to reduce the energy consumption of said sensor for operation compared to operation in continuous mode. The efficiency of the laser corresponding to the optical energy / electrical energy ratio is thus improved.

[0104] In one aspect of the invention, the gas sensor has a total length of less than 5 cm and a total width of less than 4 cm.

[0105] In one aspect according to the invention, the cell is of the dual Helmholtz resonator type comprising two first cavities connected to the detection microphone and each comprising a laser input and two other cavities, connected to the first, comprising the gas inlet duct and the gas outlet duct.

[0106] In one aspect of the invention, the cylindrical cavities of the cell have a diameter of less than 2 mm.

[0107] In one aspect according to the invention, the walls of the cell have an optical reflection factor greater than 50%, preferably 75%.

[0108] In one aspect of the invention, the gas sensor comprises a chip-base assembly comprising at least N laser units, N being greater than or equal to two, at least two laser units being configured to emit light radiation at a given wavelength under different atmospheric conditions, in particular at different temperatures.

[0109] In one aspect of the invention, the sensor is configured to operate only the laser unit(s) emitting light radiation at the wavelength given to the atmospheric conditions surrounding it, in particular to the temperature surrounding it. In this way, the sensor operates the laser unit most suited to the atmospheric conditions, for example to the temperature.

[0110] In one aspect according to the invention, the sensor comprises a chip-base assembly comprising at least N laser units, N being greater than or equal to two, at least two laser units being configured to emit light radiation at different wavelengths corresponding to different excitation wavelengths of the same gas or of the same molecule of said gas, said sensor being configured to operate the at least two laser units simultaneously so as to characterize said gas studied.

[0111] In one aspect of the invention, the chip-base assembly of the gas sensor comprises at least N laser units, N being greater than or equal to two, among which at least one laser unit is configured to be traversed by an electric current sufficiently weak to generate heat without emitting light radiation, and at least one other laser unit is configured to be traversed by an electric current sufficiently strong to generate light radiation. In this way, the thermal management of the gas sensor is optimized.

[0112] The invention also relates to a method of producing a chip-base assembly comprising the following steps: • Formation of a laser chip by: o Deposition of layers of material to form at least two laser units on a substrate, said laser units being spaced apart by a spacing in the dimension of the width of the substrate, said substrate having a thickness corresponding to the distance between an upper face and a lower face of said substrate, o Cleaving the substrate so as to form two lateral faces of said substrate, the width of the substrate obtained corresponding to the distance between the two lateral faces obtained, said width being less than or equal to 4 times the thickness of said substrate, Fixing the resulting chip on a base.

[0113] In one aspect according to the invention, the fixing step is carried out either by welding or by gluing.

[0114] In one aspect according to the invention, the method comprises a step of cutting a wafer, said wafer comprising the substrate and several laser units, so as to obtain the desired number of laser chips. Brief description of the drawings

[0115] Other characteristics, details and advantages of the invention will emerge from reading the description given below for information purposes in relation to drawings in which:

[0116] Figure 1 [Fig. 1] is a schematic representation of a photoacoustic gas sensor according to the invention,

[0117] Figure 2 [Fig. 2] is a schematic representation of a first example of embodiment of a chip-base assembly according to the invention,

[0118] Figure 3 [Fig. 3] is a schematic representation of a second exemplary embodiment of a chip-base assembly according to the invention,

[0119] Figure 4 [Fig. 4] is a schematic representation of a third example of embodiment of a chip-base assembly according to the invention,

[0120] Figure 5 [Fig. 5] is a schematic representation of a fourth example of embodiment of a chip-base assembly according to the invention,

[0121] Figure 6 [Fig. 6] is a schematic representation of a fifth example of embodiment of a chip-base assembly according to the invention,

[0122] Figure 7 [Fig. 7] is a schematic representation of a sixth example embodiment of a chip-base assembly according to the invention,

[0123] Figure 8 [Fig. 8] is a schematic representation of a seventh example embodiment of a chip-base assembly according to the invention.

[0124] Figure 1 illustrates a photoacoustic gas sensor 1 according to the invention. The photoacoustic sensor 1 according to the invention may comprise the characteristics of the photoacoustic sensor described in document FR3084745.

[0125] The photoacoustic gas sensor 1 according to the invention comprises a cell 20 comprising a gas inlet duct 60 and a gas outlet duct 70, a chip-base assembly 100 comprising a laser chip arranged on a base, said laser chip comprising at least two laser units, at least one of which is configured to emit light radiation at a wavelength in the mid-infrared, a chimney 30 opening into the cell comprising a detection microphone 50 and an opening called laser inlet 40.

[0126] In the embodiment of Figure 1, the chip-base assembly 10 is attached to the laser input 40, so that the laser radiation emitted by the at least one laser unit of the chip-base assembly 100 is directly emitted into the cell 20 without the interposition of optical focusing elements. In the embodiment of Figure 1, the laser radiation is produced by at least one quantum cascade laser (QCL) unit included in the chip-base assembly 10, said laser unit emitting in pulsed mode at 4 to 10 microns. The QCL laser unit is in the form of a bar whose typical dimensions are 3mmxl 0pmx20 pm. The divergence of the laser beam at the output of the laser bar is typically 60°. The chip-base assembly 10 can, for example, operate in pulse mode at a frequency much higher than the resonant frequency of the cell in order to avoid possible interference.

[0127] The photoacoustic sensor 1 further comprises an electronic detection circuit 80 connected to the detection microphone 50. In the embodiment of FIG. 1, the gas is introduced through an inlet conduit 60 and evacuated through an outlet conduit 70. The two conduits are directly connected to the cell 20. During the interaction between the laser emitted by the at least one laser unit of the chip-base assembly 10 and the gas, within the cell 20, the gas is excited. The excited vibrational levels will de-excite by non-radiative transitions leading to molecular collisions and heating of the gas. Thus, acoustic and thermal waves are generated and the acoustic waves will be detected by the detection microphone 50 placed in the chimney 30 connecting the microphone 50 to the cell 20.The microphone 50 is connected to a detection circuit 80 which makes it possible to determine the amplitude of the acoustic waves and thus to trace the concentration of the gaseous species studied. The chip-base assembly 10 being placed directly in front of the input face, this embodiment requires only basic alignment. In addition, not using an optical focusing element in the sensor architecture makes it much more resistant to shocks and / or vibrations, less sensitive to misalignment and less expensive. This architecture therefore increases its operating life and its range of applications.

[0128] The chip-base assembly 10 makes it possible to emit, in the cell 20, light radiation at a wavelength specifically adapted to the generation of the photoacoustic effect in the gas to be studied.

[0129] The internal walls of the gas cell 20 have an infrared reflective optical treatment in order to maximize the laser flux which interacts with the gas atoms or molecules to be studied. The cell has, for example, an optical reflection factor greater than 50% and preferably greater than 75%.

[0130] The chip-base assembly of the photoacoustic sensor 1 according to the invention can be chosen from the chip-base assemblies described in Figures 2 to 8 of the present description. The characteristics of these chip-base assemblies are described in more detail in Figures 2 to 8.

[0131] Figure 2 represents a chip-base assembly 100 according to a first embodiment.

[0132] In this embodiment, the chip-base assembly 100 comprises a laser chip 101 and a base 111 on which the laser chip 101 is placed.

[0133] The 101 laser chip includes: • A substrate, in particular cleaved, 105 comprising: o two lateral faces 107, o a lower face 109, o an upper face 108, • Three semiconductor laser units 102 arranged on the upper face 108 of the substrate 105, said three laser units 102 being distributed between said two lateral faces 107 of the substrate 105 with a spacing E between two neighboring laser units 102.

[0134] In this example, the width I of the substrate 105 is equal to the width of the laser chip.

[0135] In other words, the three laser units 2 are distributed over the width I of the substrate 105. In this way, the entire width I of the substrate, and therefore of the laser chip, is used. This makes it possible to improve the production efficiency of the laser chip 101.

[0136] The substrate 105 of the laser chip 101 here comprises a width I less than 4 times the thickness e of said substrate. In this example, the width I of the substrate is 1.5 to 3 times greater than the thickness e, preferably 2.5 times greater than the thickness e of said substrate 105.

[0137] In this way, the material surface area used for the production of the laser chip 101 is reduced, the production cost of the laser chip 101 is therefore reduced. In addition, the width l / thickness e ratio of the substrate 105 of the laser chip 101 gives it the necessary strength to avoid breakage during the cleavage step. The width I of the substrate 105 is for example between 250 pm and 300 pm, and the thickness e of the laser chip 101 is for example between 120 pm and 150 pm.

[0138] In this embodiment, the laser chip 101 is in a so-called “up” configuration, that is to say that the laser units 102 are closer to the upper face 108 of the substrate 105 than to the lower face 109 of the substrate 105. More precisely, the laser units 102 are here arranged on the upper face 108 of the substrate 105 of the laser chip 101.

[0139] The laser chip 101 here comprises three electrodes 103 of positive polarity, each of these three electrodes 103 is configured to be in electrical contact with a laser unit 102. The three electrodes 103 of positive polarity are each superimposed on a laser unit 102 and are arranged on the upper face 108 of the substrate 105 of the laser chip 101. The laser chip 101 here comprises an electrode 103 of negative polarity configured to be in electrical contact with the three laser units 102 at the same time. The electrode 103 of negative polarity is here arranged on the lower face 109 of the substrate 105 of the laser chip 101. The electrodes 103 are here formed by deposition of an electrically conductive material, in particular a metallic material, such as gold.

[0140] The laser chip 101 comprises an electrically insulating layer 104 configured to electrically insulate the laser units 102 arranged on the same face of the substrate 105 from each other, here the laser units 102 arranged on the upper face 108 of the substrate 105. The electrically insulating layer 104 is formed by deposition of an electrically insulating material, chosen from silicone or rubber, on the upper face 108 of the substrate 105. The electrically insulating layer 104 is arranged between the upper face 108 of the substrate 105 and the electrodes 103 arranged on the upper face 108 of the substrate.

[0141] The laser chip 101 comprises walls 106, said walls 106 are covered with said electrically insulating layer 104. These walls 106 are arranged between two neighboring laser units 102 so as to flatten the upper surface of the laser chip.

[0142] The spacing E between two neighboring laser units 102 is large enough so that the electrodes 103 of the same face do not come into electrical contact with each other. The spacing E between two neighboring laser units 102 is constant, in other words the spacing E between a first and a second laser unit 102 is the same as the spacing E between the second and a third laser unit 102. This spacing E is for example 100 pm. In an exemplary embodiment not shown here, the spacing E varies between two neighboring electrodes 103.

[0143] To make handling easier, the laser chip 101 is fixed on the base 111. The base 111 is parallelepipedal and has dimensions of 5mmx6mmxl, 2mm. The base 111 comprises a thermal management element, in particular a Pelletier element. The base 111 comprises a base 115 comprising a material having heat dissipation properties, in particular AIN. Thus, the base 111 also has the function of ensuring good thermal management of the laser chip 101.

[0144] The base 111 here comprises two electrical tracks 112 of different polarity, the two electrical tracks being arranged on an upper face 117 of the base 115. One of the electrical tracks 112 is of negative polarity, and the other electrical track 112 is of positive polarity. The electrical track 112 of positive polarity is here in electrical contact with one of the electrodes 103 of positive polarity of the laser chip 101, and the electrical track 112 of negative polarity is in electrical contact with the electrode 103 of negative polarity of the laser chip 101. An electric field is thus created between the two electrodes 103 and an electric current flows in the laser unit 102.The electrical track 112 of positive polarity is here in electrical contact with the electrode 103 of positive polarity via an electrical connector 113 which may be a gold wire which connects said electrical track 112 and said electrode 103, said electrical connector 113 is connected with said electrode via an electrical contact zone 114, here a gold-based solder. The electrical track 112 of negative polarity is in electrical contact with the electrode 103 of negative polarity of the laser chip 101 via a junction zone 116 between said electrical track 112 and said electrode 103.

[0145] The advantage of such an embodiment is that only the most efficient laser unit 102 is in electrical contact with the base 111, i.e. the one with better efficiency.

[0146] Figure 3 shows a second exemplary embodiment of a chip-base assembly 200 according to the invention. In this exemplary embodiment, the laser chip 201 includes the same characteristics as in the embodiment of Figure 2 except that two laser units 202 are each in electrical contact with a different positive polarity electrode 203 and with a common negative polarity electrode 203.

[0147] The substrate 205 of the laser chip 201 therefore comprises a width I less than 4 times the thickness of said substrate. In this example, the width I of the substrate is 1.5 to 3 times greater than the thickness e, preferably 2.5 times greater than the thickness e of said substrate 205.

[0148] The laser chip here comprises three 202 laser units.

[0149] The base 211 here comprises three electrical tracks 212 of different polarity, the three electrical tracks being arranged on the upper face 217 of the base 215 of the base 211. One of the electrical tracks 212 is of negative polarity, and the other two electrical tracks 212 are of positive polarity. The two electrical tracks 212 of positive polarity are in electrical contact with separate electrodes 203 of positive polarity of the laser chip 201, each of the electrodes 203 being connected to a laser unit 202. The electrical track 212 of negative polarity is in electrical contact with the electrode 203 of negative polarity of the laser chip 201. Each laser unit 202 in contact with a positive electrode 203 and a negative electrode 203 are thus traversed by an electric current.

[0150] The electrical tracks 212 of positive polarity are here in electrical contact with the electrodes 203 of positive polarity via electrical connectors 213 which may be gold wires which connect said electrical tracks 212 to said electrodes 203. Said electrical connectors 213 are connected to electrodes 203 via a gold-based solder 214. The electrical track 212 of negative polarity is in electrical contact with the electrode 203 of negative polarity via a junction zone 216 between said electrical track 212 and said electrode 203.

[0151] The advantage of such an embodiment is that only the two most efficient laser units 202 are in electrical contact with the base 211 and therefore carried a current. In other words, the laser units 202 with better optical efficiency are chosen.

[0152] In this example, the two laser units 202 in electrical contact with the base 211 can be configured to emit light radiation at the same wavelength or light radiation at different wavelengths.

[0153] Another advantage of this embodiment is that one of the laser units 202 in electrical contact with the base 211 can be configured to receive an electric current sufficiently weak not to emit light radiation and sufficiently strong to emit heat, the other laser unit 202 in electrical contact with the base 211 is configured to receive an electric current sufficiently strong to emit light radiation. In this way, the heat-emitting laser unit intervenes in the management thermal management of the chip-base assembly 200 which makes it possible to reduce the costs associated with the thermal management of such an assembly without causing light interference.

[0154] Advantageously, it is possible for the laser units 202 to be configured to emit light radiation at a given wavelength under different atmospheric conditions, in particular at different temperatures. Thus, only the laser unit 202 emitting the desired wavelength under the surrounding conditions can be put into operation so as not to supply the second laser unit 202 with energy unnecessarily.

[0155] Figure 4 shows a third exemplary embodiment of a chip-base assembly 300 according to the invention. In this exemplary embodiment, the laser chip 301 includes the same characteristics as in the embodiment of Figure 2 except that all the laser units 302 are in electrical contact with a different positive polarity electrode 303 and with a common negative polarity electrode 303.

[0156] The substrate 305 of the laser chip 301 therefore comprises a width I less than 4 times the thickness of said substrate. In this example, the width I of the substrate is 1.5 to 3 times greater than the thickness e, preferably 2.5 times greater than the thickness e of said substrate 305.

[0157] The laser chip here comprises three 302 laser units.

[0158] The base 311 here comprises four electrical tracks 312 of different polarity, the four electrical tracks 312 being arranged on the upper face 317 of the base 315 of the base 311. One of the electrical tracks 312 is of negative polarity, and the other three electrical tracks 312 are of positive polarity. The three electrical tracks 312 are in electrical contact with separate electrodes 303 of positive polarity of the laser chip 301, each of the electrodes 303 of positive polarity being connected to a separate laser unit 302. The electrical track 312 of negative polarity is in electrical contact with an electrode 303 of negative polarity of the laser chip 301. The laser units 302 in contact with a positive electrode and a negative electrode 303 are thus traversed by an electric current.

[0159] The electrical tracks 312 of positive polarity are here in electrical contact with the electrodes 303 of positive polarity via electrical connectors 313 which may be gold wires which connect said electrical tracks 312 to said electrodes 303. Said electrical connectors 313 are connected to electrodes 303 via a gold-based solder 314. The electrical track 312 of negative polarity is in electrical contact with the electrode 303 of negative polarity via a junction zone 316 between said electrical track 312 and said electrode 303.

[0160] In this example, the two laser units 302 in electrical contact with the base 311 can be configured to emit light radiation at the same wavelength or light radiation at different wavelengths.

[0161] An advantage of this embodiment is that one of the laser units 302 in electrical contact with the base 311 can be configured to receive an electrical current. weak enough not to emit light radiation and strong enough to emit heat, the other laser unit 302 in electrical contact with the base 311 is configured to receive an electric current strong enough to emit light radiation. In this way, the heat-emitting laser unit 302 intervenes in the thermal management of the chip-base assembly 300, which makes it possible to reduce the costs associated with the thermal management of such an assembly without causing light interference.

[0162] Advantageously, it is possible for the laser units 302 to be configured to emit light radiation at a given wavelength under different atmospheric conditions, in particular at different temperatures. Thus, the laser unit 302 emitting the desired wavelength under the surrounding conditions can be operated only so as not to supply the second laser unit 302 with energy unnecessarily.

[0163] Figure 5 shows a chip-base assembly 400 according to a fourth embodiment.

[0164] In this embodiment, the chip-base assembly 400 includes all of the characteristics of the embodiment of FIG. 2 except that the chip-base assembly is in the “down” position, i.e. the laser units 402 are arranged closer to the lower face 409 than to the upper face 408 of the substrate 405.

[0165] The substrate 405 of the laser chip 401 therefore comprises a width I less than 4 times the thickness of said substrate. In this example, the width I of the substrate is 1.5 to 3 times greater than the thickness e, preferably 2.5 times greater than the thickness e of said substrate 405.

[0166] The laser chip here comprises three 402 laser units.

[0167] In this example, the laser units 402 are arranged on the lower face 409 of the substrate 405.

[0168] In this example, only a positive electrode 403 of the laser chip is electrically connected to a positive electrical track 412 of the base 411. Thus, only the laser unit 402 electrically connected with said positive electrode 403 on the one hand and to a negative electrode 403 on the other hand is crossed by an electric current.

[0169] The electrical track 412 of negative polarity is here in electrical contact with the electrode 403 of negative polarity of the laser chip 401 via an electrical connector 413 which may be a gold wire which connects said electrical track 412 and said electrode 403, said electrical connector 413 is electrically connected with said electrode via a gold-based solder 414. The electrical track 412 of positive polarity is in electrical contact with the electrode of positive polarity via a junction zone 416 between said electrical track 412 and said electrode 403.

[0170] Figure 6 represents a fifth example of the embodiment of a chip-base assembly. 500 according to the invention.

[0171] The substrate 505 of the laser chip 501 therefore comprises a width I less than 4 times the thickness of said substrate. In this example, the width I of the substrate is 1.5 to 3 times greater than the thickness e, preferably 2.5 times greater than the thickness e of said substrate 505.

[0172] The laser chip here comprises three 502 laser units.

[0173] In this embodiment, the chip-base assembly 500 includes all of the characteristics of the embodiment of FIG. 3 except that the chip-base assembly is in the “down” position, i.e. the laser units 502 are arranged closer to the lower face 509 than to the upper face 508 of the substrate 505.

[0174] In this example, the laser units 502 are arranged on the lower face 509 of the substrate 505.

[0175] In this example, two positive polarity electrodes 503 of the laser chip 501 are each electrically connected to a positive electrical track 512 of the base 511. Thus, only the laser units 502 electrically connected to said positive polarity electrodes 503 of the laser chip 501 on the one hand and to a negative electrode 503 of the laser chip 501 on the other hand are crossed by an electric current.

[0176] The electrical track 512 of negative polarity is here in electrical contact with the electrode 503 of negative polarity of the laser chip 501 via an electrical connector 513 which may be a gold wire which connects said electrical track 512 and said electrode 503, said electrical connector 513 is electrically connected with said electrode via a gold-based solder 514. The electrical tracks 512 of positive polarity are in electrical contact with the electrodes of positive polarity via a junction zone 516 between said electrical track 512 and said electrodes 503.

[0177] Figure 7 represents a sixth example of embodiment of a chip-base assembly 600 according to the invention.

[0178] The substrate 605 of the laser chip 601 therefore comprises a width I less than 4 times the thickness of said substrate. In this example, the width I of the substrate is 1.5 to 3 times greater than the thickness e, preferably 2.5 times greater than the thickness e of said substrate 605.

[0179] The laser chip here comprises three 602 laser units.

[0180] In this embodiment, the chip-base assembly 600 includes all of the characteristics of the embodiment of FIG. 4 except that the chip-base assembly is in the “down” position, i.e. the laser units 602 are arranged closer to the lower face 609 than to the upper face 608 of the substrate 605.

[0181] In this example, three positive polarity electrodes 603 are each electrically connected to a positive electrical track 612 of the base 611. Thus, all the laser units 602 electrically connected to said positive polarity electrodes 603 on the one hand and to a negative electrode 603 on the other hand are crossed by an electric current.

[0182] The electrical track 612 of negative polarity is here in electrical contact with the electrode 603 of negative polarity via an electrical connector 613 which may be a gold wire which connects said electrical track 612 and said electrode 603, said electrical connector 613 is electrically connected with said electrode via a gold-based solder 614. The electrical tracks 612 of positive polarity are in electrical contact with the electrodes of positive polarity via a junction zone 616 between said electrical track 612 and said electrodes 603.

[0183] Figure 8 shows a chip-base assembly 700 according to a seventh embodiment.

[0184] In this embodiment, the chip-base assembly 700 includes all of the features of the embodiment of FIG. 2 except that the laser units 702 are buried in the substrate 705 of the chip 701.

[0185] The substrate 705 of the laser chip 701 therefore comprises a width I less than 4 times the thickness of said substrate. In this example, the width I of the substrate is 1.5 to 3 times greater than the thickness e, preferably 2.5 times greater than the thickness e of said substrate 705.

[0186] The laser chip here comprises three 702 laser units.

[0187] In this embodiment, the laser units 702 are here closer to the upper face 708 of the substrate 705 than to the lower face 709 of the substrate 705.

[0188] In this embodiment, only a positive electrode 703 is electrically connected to an electrical track 712 of the base. Only one laser unit 702 is therefore crossed by a current.

[0189] In another embodiment, several positive polarity electrodes 703 could be electrically connected to positive polarity electrical traces 712 as is the case in Figures 3 and 4.

[0190] In an embodiment not shown here, the laser units 702 could be buried in the substrate 705 such that they are closer to the bottom face 709 of the substrate 705 than to the top face 708 of the substrate.

[0191] In this embodiment, the substrate comprises a layer of semi-insulating material on either side of the laser units 702, so as to electrically isolate them from each other.

[0192] The other features of the embodiments of Figures 2 to 7 apply here.

Claims

Claims

1. A semiconductor laser chip (101, 201, 301, 401, 501, 601, 701) comprising • A substrate (105, 205, 305, 405, 505, 605, 705) comprising: o two side faces (107, 207, 307, 407, 507, 607, 707), o a lower face (109, 209, 309, 409, 509, 609, 709), o an upper face (108, 208, 308, 408, 508, 608, 708), • at least two semiconductor lasers (202, 302, 402, 502, 602, 702), these two lasers (102, 202, 302, 402, 502, 602, 702) being distributed between said two lateral faces (102, 202, 302, 402, 502, 602, 702) with a spacing (E) between two neighboring lasers (102, 202, 302, 402, 502, 602, 702), said substrate (105, 205, 305, 405, 505, 605, 705) having a width (I), this width being the distance between said two lateral faces (107, 207, 307, 407, 507, 607, 707) of the substrate (105, 205, 305, 405, 505, 605, 705) and a thickness (e), this thickness (e) being the distance measured between the lower face (109, 209, 309, 409, 509, 609, 709) and the upper face (108, 208, 308, 408, 508, 608, 708, 808) of the substrate (105, 205, 305, 405, 505, 605, 705) perpendicular to the width (I), said width (I) being less than or equal to 4 times the thickness (e).

2. Chip according to the preceding claim, characterized in that the substrate (105, 205, 305, 405, 505, 605, 705) has a width (I) 1.5 to 3 times greater than the thickness (e).

3. Chip according to one of the preceding claims, characterized in that it comprises at least three laser units (102, 202, 302, 402, 502, 602, 702), these three laser units (102, 202, 302, 402, 502, 602, 702) being distributed between said two lateral faces (107, 207, 307, 407, 507, 607, 707) of the substrate (105, 205, 305, 405, 505, 605, 705) with a spacing (E) between two neighboring lasers (102, 202, 302, 402, 502, 602, 702).

4. Chip according to one of the preceding claims, characterized in that the laser units (102, 202, 302) are closer to the upper face (108, 208, 308) of the substrate (105, 205, 305) than to the lower face (109, 209, 309) of the substrate (105, 205, 305).

5. Chip according to one of the preceding claims, characterized in that it comprises at least two electrodes (103, 203, 303, 403, 503, 603, 703) of different polarity configured to allow the passage of an electric current in at least one laser unit (102, 202, 302, 402, 502, 602, 702) of the laser chip (101, 201, 301, 401, 501, 601, 701).

6. Chip according to one of the preceding claims, characterized in that it comprises at least one insulating layer (104, 204, 304, 404, 504, 604, 704) configured to electrically isolate the laser units (102, 202, 302, 402, 502, 602, 702) arranged on the same substrate face (105, 205, 305, 405, 505, 605, 705) from each other.

7. Chip according to one of the preceding claims, characterized in that the substrate (105, 205, 305, 405, 505, 605, 705) comprises at least one semiconductor material of the InP or GaAs or GaSb or InAs or Silicon type.

8. Chip according to one of the preceding claims, characterized in that the laser chip (101, 201, 301, 401, 501, 601, 701) is a quantum cascade laser chip comprising quantum cascade laser units (102, 202, 302, 402, 502, 602, 702).

9. Chip according to one of the preceding claims, characterized in that at least one laser unit (102, 202, 302, 402, 502, 602, 702) is a quantum cascade laser unit emitting in pulsed mode at 4 to 10 microns.

10. Set (100, 200, 300, 400, 500, 600, 700) comprising: • At least one laser chip (101, 201, 301, 401, 501, 601, 701) as previously claimed, • A base (111, 211, 311, 411, 511, 611, 711) on which said chip (101, 201, 301, 401, 501, 601, 701) is mounted.

11. Assembly according to the preceding claim, characterized in that the base (111, 211, 311, 411, 511, 611, 711) comprises at least two electrical tracks (112, 212, 312, 412, 512, 612, 712) of different polarity, each of the electrical tracks (112, 212, 312, 412, 512, 612, 712) being configured to be in electrical contact with at least one electrode (103, 203, 303, 403, 503, 603, 703) of the same polarity.

12. Assembly according to one of claims 10 or 11, characterized in that the chip (101, 201, 401, 501, 701) comprises N laser units (102, 202, 402, 502, 702), N being greater than or equal to two, at most N-1 of said laser units (102, 202, 402, 502, 702) being electrically connected with the electrical tracks (112, 212, 412, 512, 712) of the base (111, 211, 411, 511, 711).

13. Assembly according to one of claims 10 to 12, characterized in that the chip-base assembly (100, 200, 300, 400, 500, 600, 700) comprises at least one laser chip (101, 201, 301, 401, 501, 601, 701) comprising at least N laser units (102, 202, 302, 402, 502, 602, 702), N being greater than or equal to two, at least two laser units being configured to emit light radiation at a given wavelength under different atmospheric conditions, in particular at different temperatures.

14. A gas sensor (1) comprising: • A cell (20) forming a resonator, comprising a gas inlet duct (60), a gas outlet duct (70) and at least one opening called a laser inlet (40); • At least one chip-base assembly (100, 200, 300, 400, 500, 600, 700) as claimed in claims 10 to 13, comprising at least two laser units, at least one of said two laser units being configured to emit, in the cell (20), light radiation having a wavelength whose value is specifically adapted to the excitation of a gas to be detected, such that an interaction between the light radiation and the gas to be detected contained in the cell induces the generation of a signal characteristic of the presence of said gas at a resonance frequency of the cell; and • A signal detection device.

15. A method of producing a chip-socket assembly (100, 200, 300, 400, 500, 600, 700) as previously claimed comprising the following steps: • Formation of a laser chip by: o Deposition of layers of material to form at least two laser units on a substrate, said laser units being spaced apart by a spacing in the dimension of the width of the substrate, said substrate having a thickness corresponding to the distance between an upper face and a lower face of said substrate, o Cleaving the substrate so as to form two lateral faces of said substrate, the width of the substrate obtained corresponding to the distance between the two lateral faces obtained, said width being less than or equal to 4 times the thickness of said substrate, Fixing the resulting chip on a base.

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