Semiconductor laser chip for gas sensor

Abstract

A semiconductor laser chip (101) comprising: a substrate (105) comprising: o two side surfaces (107), o a lower surface (109), o an upper surface (108), at least two semiconductor lasers (102) distributed between the two side surfaces (102), with a spacing (E) between two adjacent lasers (102), the substrate (101) having a width (l) and a thickness (e), the width (l) is the distance between the two sides (107) of the substrate (105) and the thickness (e) is the distance measured between the lower surface (109) and the upper surface (108) of the substrate (105) perpendicular to the width (l), the width (l) being less than or equal to four times the thickness (e).

Description

Technical Field

[0001] The present invention relates to the field of semiconductor lasers, and more specifically to a semiconductor laser chip, in particular to a semiconductor laser chip for a gas sensor. Background Art

[0002] In general, semiconductor laser chips are obtained by a complex series of steps involving the deposition of layers on a single crystal substrate (also referred to in this specification as a substrate) forming a wafer, and cutting this wafer to obtain the laser chip. The layer deposition is carried out by liquid or gas phase epitaxy or by molecular jetting onto the substrate. The substrate is a pure crystal (usually InP or InAs or GaAs or other semiconductor materials). The laser unit is usually a parallelepiped part of the wafer and is obtained by a series of chemical or physicochemical etching and deposition steps of the material, which can be amorphous or crystalline, designed to form the laser cavity and the diffraction grating and construct the laser unit.

[0003] There are many different types of semiconductor laser chips, including quantum laser cascade (QCL) chips. 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 cell corresponding to a structure comprising a gain region formed by several layers, the several layers comprising, for example, alternating layers of a first type each defining a quantum barrier and layers of a second type each defining a quantum well, the layers being made of first and second semiconductor materials constituting the barriers and the wells, respectively. The quantum cascade laser cell also comprises two optical confinement layers arranged on either side of the gain region. The laser cell forms a rod extending at least partially along the length of the semiconductor laser chip.

[0004] Once the laser chip is manufactured, it is usually cleaved parallel to the strip formed by the laser units on the substrate. Thereby, the width of the laser chip is fixed. It is then cleaved perpendicular to the strip to produce facets that act as mirrors. These cleavages involve breaking the substrate crystal on which the laser units have been deposited along a crystal axis (i.e., an axis extending through the thickness of the substrate) to obtain a nearly perfect mirror surface. This breaking is usually achieved by scratching the surface of the substrate containing the laser units and then applying pressure on either side of the scratch to break the crystal along this crystal axis.

[0005] The total production cost of the semiconductor laser chips is defined in particular by the following equation: surface area of ​​the material used to manufacture the laser chips / production yield of the semiconductor laser chips×cost of manufacturing the cleaved laser chips.

[0006] It should be understood that:

[0007] The surface area of ​​the material used is limited by the surface area of ​​the material used to make the laser chip (substrate and deposited layers),

[0008] The production efficiency of a semiconductor laser chip is defined by the ratio of the number of laser units that function to the maximum number of laser units that can be fabricated on a laser chip,

[0009] The costs of manufacturing the cleaved laser chip correspond to the costs of implementing the process for manufacturing said laser chip.

[0010] Therefore, the larger the surface area of ​​the material used, and / or the lower the production yield of the semiconductor laser chip, and / or the higher the cost of manufacturing the laser chip.

[0011] In the prior art, there are laser chips that include a single laser unit. Such semiconductor laser chips have a non-optimized production yield. This is because there is only one functional laser unit and the surface area of ​​the semiconductor laser chip is not fully utilized. In other words, part of the laser chip surface is lost.

[0012] The prior art also includes semiconductor laser chips that include multiple laser units, each configured to emit its own specific wavelength. For example, US7826509 describes a laser chip that includes several laser units that are typically 2 mm wide. This geometry is used in portable broadband sensors to detect a large number of chemical compounds simultaneously. Using such a large area of ​​material is particularly expensive.

[0013] The present invention aims to reduce the overall production cost of semiconductor laser chips by maximizing the number of laser units on the smallest laser chip obtained by cleaving. Summary of the invention

[0014] In this specification, the terms chip, laser chip, and semiconductor laser chip are used interchangeably, the terms assembly and chip substrate assembly are used interchangeably, and the terms laser unit and semiconductor laser unit are used interchangeably.

[0015] In this specification, certain elements or parameters may be indexed, such as first unit or second unit, and first parameter and second parameter, or first standard and second standard, etc. In this case, it is a matter of simple indexing to distinguish and name elements or parameters or standards that are close but not identical. The index does not imply the priority of one element, parameter or standard relative to another, and the names can be easily interchanged without departing from the scope of this specification. The index also does not imply, for example, the chronological order in which the standard or the standard is evaluated.

[0016] The present invention relates to a semiconductor laser chip, comprising:

[0017] A substrate, in particular a cleaved substrate, comprising:

[0018] o Two sides,

[0019] o Lower surface,

[0020] o Upper surface,

[0021] at least two semiconductor laser units, the two laser units being distributed between the two side surfaces with a spacing between two adjacent laser units,

[0022] The substrate has a width and a thickness, wherein the width is the distance between the two side surfaces of the substrate, and the thickness is the distance between the lower surface and the upper surface of the substrate perpendicular to the width of the substrate, and the width is less than or equal to 4 times the thickness of the substrate.

[0023] In one aspect of the invention, the laser chip is obtained by cleaving a substrate.

[0024] In one aspect of the invention, the two sides of the substrate are obtained by cleaving the substrate, the substrate is in particular cleaved.

[0025] In one aspect of the invention, the lower surface and the upper surface are two opposite sides of the substrate. The qualifiers "lower" and "upper" are conventional methods used to distinguish between the two sides.

[0026] In one aspect of the invention, the two side surfaces are two opposite sides of the substrate.

[0027] The width refers to the distance between two side surfaces of the substrate, between which the semiconductor laser units are distributed with intervals between two adjacent laser units, that is, the laser units are arranged at different positions separated by the intervals between two adjacent laser units on the width dimension of the substrate.

[0028] Thickness herein refers to the distance between a lower surface and an upper surface of a substrate, wherein the lower surface is configured to rest on a baseplate and the upper surface is opposite to the lower surface.

[0029] By length we mean the distance between two other substrate faces, each of which is bonded to one of the two side faces, the lower surface and the upper surface of the substrate, and over which the laser unit extends at least partially.

[0030] In particular, the presence of at least two laser units in the laser chip means that practically the entire surface area of ​​the laser chip can be utilized. In other words, very little surface area of ​​the substrate and, therefore, of the laser chip is wasted. The laser units are distributed across the width of the substrate so that a single chip comprises several laser units. This optimizes the production efficiency of the laser chip.

[0031] In one aspect of the invention, the width of the laser chip is the same as the width of the substrate.

[0032] In one aspect of the present invention, the width of the substrate is less than or equal to 3.5 times the thickness of the substrate, preferably less than or equal to 3 times the thickness of the substrate, preferably less than or equal to 2.5 times the thickness of the substrate, preferably less than or equal to 2 times the thickness of the substrate, preferably less than or equal to 1.5 times the thickness of the substrate.

[0033] In this way, the surface area of ​​the material used to produce the laser chip is reduced, resulting in a reduction in the production cost of the laser chip, and the width of the substrate of the semiconductor laser chip is high enough to prevent the laser chip from being damaged during the cleaving step, which could cause the chip to break. Therefore, this substrate width / thickness ratio gives the laser chip enough mechanical strength to avoid breaking during the cleaving step. This results in the smallest cleavable laser chip.

[0034] In one aspect of the present invention, the substrate width is between 150 μm and 1 mm, preferably between 150 μm and 750 μm, more preferably between 150 μm and 500 μm, more preferably between 150 μm and 400 μm, more preferably between 150 μm and 350 μm, more preferably between 150 μm and 300 μm, more preferably between 150 μm and 250 μm, more preferably between 200 μm and 250 μm, more preferably equal to 250 μm.

[0035] In one aspect according to the present invention, the substrate thickness is between 50 μm and 350 μm, preferably between 75 μm and 300 μm, more preferably between 100 μm and 200 μm, more preferably between 100 μm and 150 μm, more preferably between 120 μm and 150 μm.

[0036] In one aspect of the invention, the substrate length is between 0.5 mm and 5 mm, preferably between 1 mm and 3.5 mm, more preferably between 2 mm and 3 mm.

[0037] In one aspect of the present invention, the laser chip includes at least three laser units, which are distributed between two sides of the substrate, with a spacing between two adjacent 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.

[0038] In one aspect of the invention, the laser unit is arranged on one side of the substrate.

[0039] In one aspect of the invention, the laser unit is arranged on the lower surface of the substrate. In another aspect, the laser unit is arranged on the upper side of the substrate.

[0040] In another aspect of the invention, the laser units are embedded 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). Semi-insulating InP is for example so-called doped InP, to which impurities such as iron are added. In this way, the laser units are electrically isolated from each other.

[0041] In one aspect of the invention, the laser unit is closer to the upper surface of the substrate than to the lower surface of the substrate. This means that the laser unit is embedded in the substrate closer to the upper surface than to the lower surface of the substrate, or the laser unit is positioned on the upper surface of the laser chip substrate.

[0042] In one aspect of the invention, the laser unit is closer to the lower surface of the substrate than to the upper surface of the substrate. This means that the laser unit is embedded in the substrate closer to the lower surface of the substrate than to the upper surface, or the laser unit is positioned on the lower surface of the substrate.

[0043] In one aspect of the present invention, a laser chip comprises at least two electrodes having different polarities, the at least two electrodes being configured to allow current to flow through at least one laser unit of the laser chip. The at least two electrodes are configured to be in electrical contact with the at least one laser unit.

[0044] In one aspect of the invention, the laser chip comprises at least one electrode of positive polarity and at least one electrode of negative polarity, the electrodes being configured to be in electrical contact with at least one laser unit so as to allow current to flow through the at least one laser unit.

[0045] In one aspect of the invention, at least one electrode of a given polarity is arranged on at least one laser unit.

[0046] In one aspect of the present invention, the laser chip includes as many positive polarity electrodes as there are laser units. In other words, each positive electrode is in electrical contact with a separate laser unit. For example, the laser chip includes one laser unit and one positive polarity electrode, or the chip includes two laser units and two positive polarity electrodes, or the chip includes three laser units and three positive polarity electrodes, or the chip includes N laser units and N positive polarity electrodes.

[0047] In one aspect of the present invention, the laser chip includes as many negative polarity electrodes as the laser units it has. In other words, each negative electrode is in electrical contact with a separate laser unit. For example, the laser chip includes one laser unit and one negative polarity electrode, or the chip includes two laser units and two negative polarity electrodes, or the chip includes three laser units and three negative polarity electrodes, or the chip includes N laser units and N negative polarity electrodes.

[0048] In one aspect of the present invention, the laser chip includes a positive polarity electrode configured to be in electrical contact with all of the laser units simultaneously.

[0049] In one aspect of the present invention, the laser chip includes a negative polarity electrode configured to be in electrical contact with all of the laser units simultaneously.

[0050] In one aspect of the invention, at least one electrode is arranged on the lower surface of the substrate.

[0051] In one aspect of the invention, all electrodes of the same polarity are arranged on the same side of the substrate.

[0052] In one aspect of the invention, the electrode is configured to be electrically connected to the substrate, in particular to an electrical trace of the substrate.

[0053] In one aspect of the present invention, the spacing between two adjacent laser units distributed between the two sides of the substrate is between 10 μm and 150 μm, preferably between 20 μm and 150 μm, more preferably between 30 μm and 150 μm, more preferably between 40 μm and 150 μm, more preferably between 50 μm and 150 μm, more preferably between 75 μm and 125 μm, more preferably equal to 100 μm. In other words, over the width of the chip, the spacing between two adjacent laser units is between 75 and 150 μm, preferably between 75 μm and 125 μm, more preferably equal to 100 μm. In this way, the spacing between two adjacent laser units is configured so that the electrodes on the same side are not electrically connected to each other.

[0054] In one aspect of the present invention, the spacing between two adjacent laser units distributed between two sides of the substrate is constant. In other words, when the laser chip includes N laser units, N is greater than or equal to 2, the spacing between the first laser unit and the second laser unit on the width of the substrate is the same as the spacing between the second laser unit and the third laser unit, and the spacing between the second laser unit and the third laser unit is the same as the spacing between the n-1th laser unit and the Nth laser unit.

[0055] In one aspect of the present invention, the spacing between at least two adjacent laser units distributed between two sides of the substrate is varied. In other words, the spacing across the width of the substrate between the first laser unit and the second laser unit is different from the spacing between the second laser unit and the third laser unit.

[0056] In one aspect of the invention, the electrode is formed by depositing a conductive material on the substrate, in particular a metal material, which is configured to be in electrical contact with at least one laser unit. For example, the conductive metal material is selected from gold, copper, silver or aluminum.

[0057] In one aspect of the present invention, the substrate comprises at least one semiconductor material of InP (Indium Phosphide) or GaAs (Gallium Arsenide) or GaSb (Gallium Antimonide) or InAs (Indium Arsenide) or a silicon type material.

[0058] In one aspect of the invention, the laser chip comprises at least one electrically insulating layer configured to electrically isolate laser units arranged on the same side of the substrate from each other. In this way, the laser units each have their own current flowing through them.

[0059] In one aspect of the invention, the electrically insulating layer is obtained by depositing an electrically insulating material on a substrate. For example, the electrically insulating material is selected from silicone or rubber.

[0060] In one aspect of the invention, an electrically insulating layer is arranged between a top surface of the substrate and at least one electrode arranged on said top surface.

[0061] In one aspect of the invention, the laser chip comprises at least one wall between two electrodes, said wall being covered by said electrically insulating layer.The wall helps to flatten the surface of the laser chip, in particular when the laser unit is located on the upper or lower surface of the substrate.

[0062] In one aspect of the invention, the laser chip is a quantum cascade laser chip. In other words, at least two laser units are quantum cascade laser units.

[0063] In one aspect of the invention, the laser unit is configured to emit optical radiation in a pulsed mode. In particular, this reduces the energy required to power the laser unit compared to continuous operation. The efficiency of the laser unit (optical energy required / electrical energy) is thus improved.

[0064] In one aspect of the invention, the at least one laser unit is configured to emit optical radiation of a wavelength in the infrared, preferably in the mid-infrared.

[0065] In one aspect of the invention, the at least one laser unit is configured to emit optical radiation in a wavelength range between 3 micrometers and 15 micrometers, preferably between 4 micrometers and 10 micrometers.

[0066] In one aspect of the invention, all laser units on a laser chip are configured to emit optical radiation of the same wavelength.

[0067] In one aspect of the invention, at least two laser units of the laser chip are configured to emit optical radiation of different wavelengths.

[0068] In one aspect of the invention, a laser chip comprises N laser units, N being greater than or equal to 2, at least one of the laser units being configured to have a sufficiently low current flowing therethrough to enable heat to be generated without emitting optical radiation, and at least one other laser unit being configured to have a sufficiently high current flowing therethrough to generate optical radiation.

[0069] In one aspect of the present invention, the laser chip comprises at least N laser units, N being greater than or equal to 2, and at least two laser units are configured to emit optical radiation of a given wavelength under different atmospheric conditions, in particular at different temperatures.

[0070] In one aspect of the invention, the laser chip is configured to operate only laser units that emit optical radiation of a given wavelength under ambient atmospheric conditions, in particular ambient temperature.

[0071] The present invention also relates to a chip substrate assembly, comprising:

[0072] at least one semiconductor laser chip as described above,

[0073] A substrate on which the laser chip is mounted.

[0074] In other words, the chip / substrate assembly comprises a laser chip as described above, which is arranged on a substrate. In other words, the laser chip and the substrate are stacked.

[0075] In one aspect of the present invention, the lower surface of the laser chip substrate faces the base plate. In other words, the lower surface of the laser chip substrate is arranged on the base plate, and the upper surface of the substrate is opposite to the base plate.

[0076] In one aspect of the present invention, the electrode arranged on the lower surface of the substrate is arranged on the base plate.

[0077] In one aspect of the invention, the laser chip is fixed to the substrate, for example by soldering or bonding.

[0078] In one aspect of the present invention, the substrate comprises at least one base portion comprising a material having heat dissipation properties, the material being selected from the group consisting of copper and AlN.

[0079] In one aspect of the invention, the substrate comprises a thermal management element, in particular a Pelletier element.

[0080] The substrate has, among other things, a thermal management function for the laser chip. It does allow for good heat dissipation.

[0081] In one aspect of the invention, the base of the substrate is a parallelepiped.

[0082] In one aspect of the present invention, the base of the substrate includes an upper surface, a lower surface and two side surfaces, the upper surface being opposite to the lower surface. The qualifiers "lower" and "upper" are conventional usages for distinguishing the two surfaces.

[0083] In one aspect of the invention, the laser units of the laser chip are closer to the lower surface of the laser chip substrate and thus closer to the base plate than to the upper side of the laser chip substrate.

[0084] In one aspect of the invention, the laser units of the laser chip are closer to the upper side of the laser chip substrate than to the lower side of the laser chip substrate, and thus closer to the base plate.

[0085] In one aspect of the invention, the substrate comprises at least two electrical traces of different polarity, each of the electrical traces being configured to make electrical contact with at least one electrode of the same polarity on the laser chip.

[0086] In one aspect of the invention, the electrical trace is configured to make electrical contact with at least one laser unit.

[0087] In one aspect of the invention, the at least one laser unit is configured to be in electrical contact with at least two electrodes of the laser chip, the electrodes being electrically connected to electrical traces. In this way, the laser unit is configured to be in electrical contact with the substrate, more specifically, with the electrical traces of the substrate.

[0088] In one aspect of the invention, the substrate includes as many electrical traces of a given polarity as the laser chip includes electrodes of the same polarity. In other words, the substrate includes as many electrical traces of positive polarity as the laser chip includes electrodes of positive polarity, and the substrate includes as many electrical traces of negative polarity as the chip includes electrodes of negative polarity.

[0089] In one aspect of the invention, the substrate includes a positive polarity electrical trace configured to make electrical contact with all positive polarity electrodes on the laser chip.

[0090] In one aspect of the invention, the substrate includes a negative polarity electrical trace configured to make electrical contact with all negative polarity electrodes on the laser chip.

[0091] In one aspect of the invention, each of the electrical traces is disposed on a base of the substrate.

[0092] In one aspect of the invention, each of the electrical tracks is arranged on a same face of a base of the substrate, in particular on an upper face of said base.

[0093] In one aspect of the invention, the electrical traces are formed by depositing a conductive material, in particular a metal deposit, on a substrate.

[0094] In one aspect of the invention, the chip-substrate assembly comprises at least one electrical connector configured to electrically connect an electrical lead of the substrate to at least one electrode of the chip. The electrical connector is, for example, a wire or a plate comprising a conductive material, in particular gold, copper, aluminum or silver.

[0095] In one aspect of the invention, the electrical connector is connected on the one hand to at least one electrode of a given polarity on the laser chip by means of an electrical contact area (in particular by soldering or bonding) and on the other hand to at least one electrical track on the substrate having the same polarity as said electrode. The electrical contact area comprises, for example, an electrically conductive material such as gold, copper, aluminum or silver.

[0096] In one aspect of the invention, the electrical contact region at least partially covers the laser chip electrode.

[0097] In one aspect of the present invention, the diameter of the electrical contact area is less than or equal to 100 μm, preferably less than or equal to 90 μm, preferably less than or equal to 80 μm, preferably less than or equal to 70 μm, preferably less than or equal to 60 μm, preferably less than or equal to 60 μm, preferably less than or equal to 50 μm, preferably less than or equal to 25 μm, preferably less than or equal to 10 μm.

[0098] In one aspect of the invention, the electrical trace is configured to be in electrical contact with at least one electrode via a land. A land is a land where the contact between the electrical trace and the electrode is physical. In other words, the electrode and the electrical trace are superimposed on each other. In this case, an electrical connector is not required to electrically contact at least one electrode and the electrical trace.

[0099] In one aspect of the invention, the laser chip comprises N laser units, N being greater than or equal to 2, and at most N-1 of the laser units being electrically connected to the electrical traces of the substrate. In other words, at least one laser unit is not electrically connected to the electrical traces of the substrate. In this way, only the most effective laser units are in electrical contact with the substrate.

[0100] In one aspect of the present invention, a laser chip includes N laser units, N being greater than or equal to 2, at least one of the N laser units being configured to have a sufficiently low current flowing therethrough to enable heat to be generated without emitting optical radiation, and at least one other laser unit being configured to have a sufficiently high current flowing therethrough to generate optical radiation.

[0101] In one aspect of the invention, a chip comprises N laser units, N being greater than or equal to 2, at least one of the laser units being configured to emit optical radiation of a different wavelength than the other laser units.

[0102] In one aspect of the present invention, a chip-substrate assembly comprises at least two chips as described above.

[0103] In one aspect of the present invention, a chip-substrate assembly includes at least one laser chip, the laser chip including N laser units, N being greater than or equal to 2, at least one of the laser units being configured to have a sufficiently low current flowing through it to enable heat to be generated without emitting optical radiation, and at least one other laser unit being configured to have a sufficiently high current flowing through it to generate optical radiation.

[0104] In one aspect of the present invention, the chip-substrate assembly includes at least one laser chip, which includes at least N laser units, N is greater than or equal to 2, and at least two laser units are configured to emit optical radiation of a given wavelength under different atmospheric conditions, in particular at different temperatures.

[0105] In one aspect of the invention, the chip-substrate assembly is configured to operate the laser unit only to emit optical radiation at a wavelength given the ambient atmospheric conditions (particularly the ambient temperature). In this way, the chip-substrate assembly operates the laser unit best suited to the atmospheric conditions (e.g., temperature).

[0106] The present invention also relates to a gas sensor, comprising:

[0107] a cell forming a resonator, comprising a gas inlet duct, a gas outlet duct and at least one laser inlet opening,

[0108] at least one chip-substrate assembly as described above, comprising at least two laser units, at least one of said two laser units being configured to emit optical radiation into said cell, said optical radiation having a wavelength whose value is particularly suitable for the excitation of the gas to be detected, such that the interaction between said optical radiation and the gas to be detected contained in said cell induces a signal characteristic of the presence of said gas at a resonant frequency of said cell, and

[0109] Signal detection device.

[0110] According to one aspect of the present invention, a gas sensor comprises:

[0111] a cell forming an optical resonator, comprising a gas inlet duct, a gas outlet duct and at least one aperture, referred to as a laser inlet,

[0112] at least one chip-substrate assembly as described above, comprising at least two laser units, at least one of said two laser units being configured to emit optical radiation into said cell, said optical radiation having a wavelength whose value is particularly suitable for the excitation of the gas to be detected, so that the interaction between said optical radiation and the gas to be detected contained in said cell induces an optical signal characteristic of the presence of said gas at the resonance frequency of said cell, and

[0113] Signal detection device.

[0114] In one aspect of the invention, the gas sensor comprises focusing or collimating means, in particular a lens configured to collimate or focus the optical radiation from the at least one laser unit.

[0115] In another embodiment according to the invention, the gas sensor according to the invention is a photoacoustic gas sensor comprising the features described in FR3084745.

[0116] In this embodiment, the gas sensor comprises:

[0117] a cell forming an acoustic resonator, comprising a gas inlet duct, a gas outlet duct and at least one opening referred to as a laser inlet;

[0118] at least one chip-substrate 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 optical radiation having a wavelength whose value is particularly suitable for the excitation of the gas to be detected, so that the interaction between the optical radiation and the gas to be detected contained in the cell induces the generation of acoustic waves at the resonance frequency of the cell; and

[0119] • At least one detection microphone, arranged in the chimney opening to the cell.

[0120] In another aspect of the invention, the chip-substrate assembly is placed directly in front of the laser input of the cell without the intervening focusing or collimating optics.

[0121] In one aspect of the invention, the chip-substrate assembly is disposed inside the sensor cell.

[0122] In another aspect of the invention, the photoacoustic gas sensor comprises focusing or collimating means, in particular a lens configured to collimate or focus the optical radiation from the at least one laser unit.

[0123] In one aspect of the invention, the sensor comprises a power supply circuit configured to operate the laser source in pulsed mode. In particular, this makes it possible to reduce the power consumption of the sensor for operation compared to operation in continuous mode. The laser efficiency corresponding to the light energy / electrical energy ratio is thus improved.

[0124] In one aspect of the invention, the gas sensor has an overall length of less than 5 cm and an overall width of less than 4 cm.

[0125] In one aspect of the invention, the cell is of the double Helmholtz resonator type, comprising two first cavities connected to detection microphones and each having a laser input, and two further cavities connected to the first cavities, comprising a gas inlet duct and a gas outlet duct.

[0126] In one aspect of the invention, the cylindrical cavity of the cell has a diameter of less than 2 mm.

[0127] In one aspect of the invention, the cell walls have an optical reflectivity greater than 50%, preferably 75%.

[0128] In one aspect of the present invention, a gas sensor comprises a chip-substrate assembly comprising at least N laser units, N being greater than or equal to 2, and at least two laser units being configured to emit optical radiation of a given wavelength under different atmospheric conditions, in particular at different temperatures.

[0129] In one aspect of the invention, the sensor is configured to operate the laser unit(s) only to emit optical radiation at a wavelength given the ambient atmospheric conditions, in particular the ambient temperature. In this way, the sensor operates the laser unit(s) best suited to the atmospheric conditions, such as temperature.

[0130] In one aspect of the invention, a sensor comprises a chip substrate assembly comprising at least N laser units, N being greater than or equal to 2, at least two laser units being configured to emit light radiation of different wavelengths corresponding to different excitation wavelengths of the same gas or the same molecules of the gas, and the sensor being configured to operate at least two laser units simultaneously so as to characterize the gas under study.

[0131] In one aspect of the invention, a chip-substrate assembly of a gas sensor includes at least N laser units, where N is greater than or equal to 2, where at least one laser unit is configured to have a sufficiently low current flowing through it to generate heat without emitting optical radiation, and at least one other laser unit is configured to have a sufficiently high current flowing through it to generate optical radiation. In this way, thermal management of the gas sensor is optimized.

[0132] The invention also relates to a process for producing a chip-substrate assembly, comprising the following steps:

[0133] Laser chip formation is performed by:

[0134] o depositing a layer of material to form at least two laser units on a substrate, the laser units being spaced apart by a spacing in a width dimension of the substrate, the substrate having a thickness corresponding to a distance between an upper surface and a lower surface of the substrate,

[0135] o cleaving the substrate to form two side surfaces of the substrate, the width of the substrate obtained corresponds to the distance between the two side surfaces obtained, the width being less than or equal to 4 times the thickness of the substrate,

[0136] • Attach the resulting chip to a substrate.

[0137] In one aspect of the invention, the fixing step is performed by welding or by gluing.

[0138] In one aspect of the invention, the process comprises the step of dicing a wafer comprising a substrate and a plurality of laser units in order to obtain a desired number of laser chips. BRIEF DESCRIPTION OF THE DRAWINGS

[0139] Other features, details and advantages of the invention will become apparent from the following description given in conjunction with the accompanying drawings, in which:

[0140] Figure 1 is a schematic diagram of a photoacoustic gas sensor according to the present invention,

[0141] Figure 2 is a schematic representation of a first example of a chip-substrate assembly according to the present invention,

[0142] Figure 3 is a schematic representation of a second example of a chip-substrate assembly according to the present invention,

[0143] Figure 4 is a schematic representation of a third example of a chip-substrate assembly according to the present invention,

[0144] Figure 5 is a schematic representation of a fourth example of a chip-substrate assembly according to the present invention,

[0145] Figure 6 is a schematic representation of a fifth example of a chip-substrate assembly according to the present invention,

[0146] Figure 7 is a schematic representation of a sixth example of a chip-substrate assembly according to the present invention,

[0147] Figure 8 is a schematic representation of a seventh embodiment of a chip-substrate assembly according to the present invention. DETAILED DESCRIPTION

[0148] Figure 1 A photoacoustic gas sensor 1 according to the invention is shown. The photoacoustic sensor 1 according to the invention may comprise the features of the photoacoustic sensor described in document FR3084745.

[0149] The photoacoustic gas sensor 1 according to the present invention comprises: a cell 20 including a gas inlet duct 60 and a gas outlet duct 70, a chip-substrate assembly 100 including a laser chip arranged on a substrate, a chimney 30 leading to the cell and a hole called a laser inlet 40, wherein the laser chip includes at least two laser units (at least one of which is configured to emit optical radiation with a wavelength in the mid-infrared range), and the chimney 30 includes a detection microphone 50.

[0150] exist Figure 1 In the illustrated embodiment, the chip-substrate assembly 10 is attached to the laser input port 40 so that the laser radiation emitted by at least one laser unit of the chip-substrate assembly 100 is emitted directly into the cell 20 without intervening optical focusing elements. Figure 1 In the embodiment shown, the laser radiation is generated by at least one quantum cascade laser unit (QCL) included in the chip-substrate assembly 10, which emits in a pulsed mode at 4 to 10 microns. The QCL laser unit takes the form of a bar with typical dimensions of 3 mm x 10 μm x 20 μm. The divergence of the laser beam from the laser bar is typically 60°. The chip-substrate assembly 10 can be operated in a pulsed mode, for example, at a frequency much higher than the resonance frequency of the cell, to avoid possible interference.

[0151] The photoacoustic sensor 1 further comprises an electronic detection circuit 80 connected to the detection microphone 50. Figure 1 In the embodiment shown, the gas is introduced via an inlet conduit 60 and is exhausted via an outlet conduit 70. Both conduits are directly connected to the cell 20. During the interaction between the laser light emitted by at least one laser unit of the chip-substrate assembly 10 and the gas within the cell 20, the gas is excited. The excited vibrational energy levels will be de-excited by non-radiative transitions, resulting in molecular collisions and heating of the gas. Acoustic and thermal waves are thus generated, and the acoustic waves are detected by a detection microphone 50 placed in a chimney 30 connecting the microphone 50 to the cell 20. The microphone 50 is connected to a detection circuit 80, which determines the amplitude of the acoustic waves and thus the concentration of the gas species under investigation. Since the chip-substrate assembly 10 is placed directly in front of the input face, the design requires only basic alignment. In addition, the absence of focusing optical elements in the sensor architecture makes it more resistant to shock and / or vibration, less sensitive to misalignment and less costly. This architecture increases the uptime and application range of the sensor.

[0152] The chip-substrate assembly 10 enables optical radiation to be emitted into the cell 20 at a wavelength particularly suitable for producing a photoacoustic effect in the gas to be investigated.

[0153] The inner wall of the gas cell 20 has an infrared reflective optical treatment to maximize the laser flux that interacts with the gaseous atoms or molecules to be studied. For example, the cell has an optical reflectivity of more than 50%, preferably more than 75%.

[0154] The chip-substrate assembly of the photoacoustic sensor 1 according to the present invention can be obtained from Figures 2 to 8 The chip-substrate assembly described in is selected. Figures 2 to 8 Features of these chip-substrate assemblies are described in more detail in .

[0155] Figure 2 A chip-substrate assembly 100 in a first embodiment is shown.

[0156] In this embodiment, the chip-substrate assembly 100 includes a laser chip 101 and a substrate 111 , on which the laser chip 101 is placed.

[0157] The laser chip 101 includes:

[0158] A substrate, in particular a cleaved substrate 105, comprising:

[0159] o Two sides 107,

[0160] o Lower surface 109,

[0161] o upper surface 108,

[0162] Three semiconductor laser units 102 are arranged on the upper surface 108 of the substrate 105 . The three laser units 102 are distributed between the two side surfaces 107 of the substrate 105 , and there is a distance E between two adjacent laser units 102 .

[0163] In this example, the width l of the substrate 105 is equal to the width of the laser chip.

[0164] In other words, three laser units 2 are distributed over the width l of the substrate 105. In this way, the entire width l of the substrate and, therefore, the entire width l of the laser chip is utilized. Thereby, the production efficiency of the laser chip 101 is improved.

[0165] The substrate 105 of the laser chip 101 has a width l which is less than 4 times the thickness e of the substrate. In this example, the width l of the substrate is 1.5 to 3 times greater than the thickness e, preferably 2.5 times greater than the thickness e of the substrate 105 .

[0166] In this way, the surface area of ​​the material used to produce the laser chip 101 is reduced, and the production costs of the laser chip 101 are reduced. In addition, the ratio of width l / thickness e of the substrate of the laser chip 105 gives it the strength required to avoid breakage during the cleavage phase. The width l of the substrate 105 is, for example, between 250 μm and 300 μm, and the thickness e of the laser chip 101 is, for example, between 120 μm and 150 μm.

[0167] In this embodiment, the laser chip 101 is in an "upward" configuration, i.e., the laser unit 102 is closer to the upper surface 108 of the substrate 105 than to the lower surface 109 of the substrate 105. More precisely, the laser unit 102 is arranged on the upper surface 108 of the substrate 105 of the laser chip 101.

[0168] The laser chip 101 includes three electrodes 103 of positive polarity, each of which is configured to be in electrical contact with the laser unit 102. The three electrodes 103 of positive polarity are each superimposed on the laser unit 102 and arranged on the top surface 108 of the substrate 105 of the laser chip 101. The laser chip 101 includes a negative polarity electrode 103, which is configured to be in electrical contact with all three laser units 102 at the same time. Here, the negative polarity electrode 103 is arranged on the lower surface 109 of the substrate 105 of the laser chip 101. Here, the electrode 103 is formed by depositing a conductive material, in particular a metal material, such as gold.

[0169] The laser chip 101 includes an electrical insulation layer 104 configured to electrically isolate laser units 102 arranged on the same face of a substrate 105 from each other, in this case, the laser units 102 are arranged on an upper surface 108 of the substrate 105. The electrical insulation layer 104 is formed by depositing an electrical insulation material selected from silicone or rubber on the upper surface 108 of the substrate 105. The electrical insulation layer 104 is arranged between the upper surface 108 of the substrate 105 and the electrode 103 arranged on the upper surface 108 of the substrate.

[0170] The laser chip 101 comprises walls 106 which are covered by the electrically insulating layer 104 , these walls 106 being arranged between two adjacent laser units 102 in order to flatten the upper surface of the laser chip.

[0171] The spacing E between two adjacent laser units 102 is large enough so that the electrodes 103 on the same side do not electrically contact each other. The spacing E between two adjacent laser units 102 is constant, i.e. the spacing E between the first and second laser units 102 is the same as the spacing E between the second and third laser units 102. The spacing E is, for example, 100 μm. In an embodiment not shown here, the spacing E varies between two adjacent electrodes 103.

[0172] For ease of handling, the laser chip 101 is attached to a substrate 111. The substrate 111 is a parallelepiped and has dimensions of 5 mm×6 mm×1.2 mm. The substrate 111 comprises a thermal management element, in particular a Pelletier element. The substrate 111 comprises a base 115 comprising a material with heat dissipation properties, in particular AlN. Thus, the substrate 111 also has the function of ensuring good thermal management of the laser chip 101.

[0173] The substrate 111 includes two electrical traces 112 of different polarity, which are arranged on the upper surface 117 of the base 115. One of the electrical traces 112 is of negative polarity, and the other electrical trace 112 is of positive polarity. The positive electrode 112 is in electrical contact with one of the positive 103 electrodes of the laser chip 101, and the negative electrode 112 is in electrical contact with the negative 103 electrode of the laser chip 101. Therefore, an electric field is generated between the two electrodes 103, and current flows through the laser unit 102. The electrical trace 112 of positive polarity is in electrical contact with the electrode 103 of positive polarity via an electrical connector 113, which may be a gold wire connecting the electrical trace 112 and the electrode 103, and the electrical connector 113 is connected to the electrode via an electrical contact area 114 (here, gold-based solder). The electrical trace 112 of negative polarity is in electrical contact with the electrode 103 of negative polarity of the laser chip 101 via a bonding area 116 between the electrical trace 112 and the electrode 103 .

[0174] The advantage of this design is that only the most efficient 102 laser units are in electrical contact with the substrate 111, ie the laser units with the highest efficiency.

[0175] Figure 3 A second example of a chip-substrate assembly 200 according to the present invention is shown. In this embodiment, a laser chip 201 includes Figure 2 The same features are shown in the embodiment except that the two laser units 202 are each electrically contacted with an electrode 203 of a different positive polarity and an electrode 203 of a common negative polarity.

[0176] The substrate 205 of the laser chip 201 therefore has a width l which is less than 4 times the thickness of said substrate. In this example, the width l 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 .

[0177] The laser chip here includes three laser units 202 .

[0178] The substrate 211 includes three electrical traces 212 of different polarities, which are arranged on an upper surface 217 of a bottom 215 of the substrate 211. One of the electrical traces 212 is of negative polarity, and the other two electrical traces 212 are of positive polarity. The two electrical traces 212 of positive polarity are in electrical contact with individual electrodes 203 of positive polarity on the laser chip 201, each of which is connected to a laser unit 202. The negative polarity electrical trace 212 is in electrical contact with the negative polarity electrode 203 of the laser chip 201. Therefore, each laser unit 202 in contact with the positive electrode 203 and the negative electrode 203 has current flowing through them.

[0179] The positive polarity electrical trace 212 is here in electrical contact with the positive polarity electrode 203 via an electrical connector 213, which may be a gold wire connecting the electrical trace 212 to the electrode 203. The electrical connector 213 is connected to the electrode 203 via a gold-based solder 214. The negative polarity electrical trace 212 is in electrical contact with the negative polarity electrode 203 via a bonding area 216 between the electrical trace 212 and the electrode 203.

[0180] The advantage of this type of design is that only the two best performing laser units 202 are in electrical contact with the substrate 211 and therefore have current flowing through them. In other words, the laser unit 202 with the best optical performance is selected.

[0181] In this example, the two laser units 202 in electrical contact with the substrate 211 may be configured to emit optical radiation of the same wavelength or optical radiation of different wavelengths.

[0182] Another advantage of this design is that one of the laser units 202 in electrical contact with the substrate 211 can be configured to receive a current that is weak enough not to emit optical radiation and strong enough to emit heat, while the other laser unit 202 in electrical contact with the substrate 211 is configured to receive a current that is strong enough to emit optical radiation. In this way, the thermal emitting laser unit plays a role in the thermal management of the chip-substrate assembly 200, thereby reducing the costs associated with the thermal management of such an assembly without causing light emission interference.

[0183] Advantageously, the laser unit 202 can be configured to emit optical radiation at a given wavelength under different atmospheric conditions, in particular at different temperatures. In this way, only the laser unit 202 emitting the desired wavelength under ambient conditions can be switched on so as not to provide unnecessary energy to the second laser unit 202.

[0184] Figure 4 FIG. 3 shows a third example of a chip-substrate assembly 300 according to the present invention. In this embodiment, a laser chip 301 includes Figure 2 The same features are present in the illustrated embodiment, except that all laser units 302 are in electrical contact with different positive polarity electrodes 303 and a common negative polarity electrode 303 .

[0185] The substrate 305 of the laser chip 301 therefore has a width l which is less than 4 times the thickness of said substrate. In this example, the width l 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 .

[0186] The laser chip here includes three laser units 302 .

[0187] The substrate 311 includes four electrical traces 312 of different polarities, which are arranged on the upper surface 317 of the base 315 of the substrate 311. One of the electrical traces 312 has a negative polarity, and the other three electrical traces 312 have a positive polarity. The three electrical traces 312 are in electrical contact with individual positive polarity electrodes 303 on the laser chip 301, each of which is connected to an individual laser unit 302. The negative polarity electrical trace 312 is in electrical contact with the negative polarity electrode 303 on the laser chip 301. The laser unit 302 in contact with the positive electrode 303 and the negative electrode 303 is therefore passed through by current.

[0188] The positive polarity electrical trace 312 is here in electrical contact with the positive polarity electrode 303 via an electrical connector 313, which may be a gold wire connecting the electrical trace 312 to the electrode 303. The electrical connector 313 is connected to the electrode 303 via a gold-based solder 314. The negative polarity electrical trace 312 is in electrical contact with the negative polarity electrode 303 via a bonding area 316 between the electrical trace 312 and the electrode 303.

[0189] In this example, the two laser units 302 in electrical contact with the substrate 311 may be configured to emit optical radiation of the same wavelength or optical radiation of different wavelengths.

[0190] One advantage of this design is that one of the laser units 302 in electrical contact with the substrate 311 can be configured to receive a current that is weak enough not to emit optical radiation and strong enough to emit heat, while the other laser unit 302 in electrical contact with the substrate 311 is configured to receive a current that is strong enough to emit optical radiation. In this way, the heat-generating laser unit 302 intervenes in the thermal management of the chip-substrate assembly 300, thereby reducing the costs associated with the thermal management of such an assembly without causing light emission interference.

[0191] Advantageously, the laser unit 302 can be configured to emit optical radiation of a given wavelength under different atmospheric conditions, in particular at different temperatures. In this way, the laser unit 302 emitting the desired wavelength under ambient conditions can only be switched on so as not to provide unnecessary energy to the second laser unit 302.

[0192] Figure 5 A chip-substrate assembly 400 in a fourth embodiment is shown.

[0193] In this embodiment, the chip-substrate assembly 400 includes Figure 2 All features of the illustrated embodiment are present, except that the chip-substrate assembly is in a “downward” position, ie, the laser unit 402 is positioned closer to the lower surface 409 than to the upper surface 408 of the substrate 405 .

[0194] The substrate 405 of the laser chip 401 therefore has a width l which is less than 4 times the thickness of said substrate. In this example, the width l 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 .

[0195] The laser chip includes three laser units 402 .

[0196] In this example, the laser unit 402 is arranged on a lower surface 409 of a substrate 405 .

[0197] In this example, only the positive electrode 403 of the laser chip is electrically connected to the positive electrical trace 412 of the substrate 411. Therefore, only the laser unit 402 electrically connected to said positive electrode 403 on the one hand and to the negative electrode 403 on the other hand has a current flowing therethrough.

[0198] The negative polarity electric trace 412 is in electrical contact with the negative polarity electrode 403 of the laser chip 401 via an electric connector 413. The electric connector 413 may be a gold wire connecting the electric trace 412 and the electrode 403. The electric connector 413 is electrically connected to the electrode via a gold-based solder 414. The positive polarity electric trace 412 is in electrical contact with the positive polarity electrode via a bonding area 416 between the electric trace 412 and the electrode 403.

[0199] Figure 6 A fifth example of a chip-substrate assembly 500 according to the present invention is shown.

[0200] Therefore, the substrate 505 of the laser chip 501 has a width l which is less than 4 times the thickness of the substrate. In this example, the width l of the substrate is 1.5 to 3 times greater than the thickness e, preferably 2.5 times greater than the thickness e of the substrate 505 .

[0201] The laser chip includes three laser units 502 .

[0202] In this embodiment, the chip-substrate assembly 500 includes Figure 3 All features of the embodiment shown in are retained except that the chip-substrate assembly is in a “downward” position, ie, the laser unit 502 is positioned closer to the lower surface 509 than to the upper surface 508 of the substrate 505 .

[0203] In this example, the laser unit 502 is arranged on a lower surface 509 of a substrate 505 .

[0204] In this example, the two positive polarity electrodes 503 of the laser chip 501 are each electrically connected to a positive electrical trace 512 of the substrate 511. Therefore, only those laser units 502 which are electrically connected to said positive polarity electrode 503 of the laser chip 501 on the one hand and to the negative electrode 503 of the laser chip 501 on the other hand have current flowing through them.

[0205] The negative polarity electric trace 512 is in electrical contact with the negative polarity electrode 503 of the laser chip 501 via an electric connector 513. The electric connector 513 may be a gold wire connecting the electric trace 512 and the electrode 503. The electric connector 513 is electrically connected to the electrode via a gold-based solder 514. The positive polarity electric trace 512 is in electrical contact with the positive polarity electrode via a bonding area 516 between the electric trace 512 and the electrode 503.

[0206] Figure 7 A sixth example of a chip-substrate assembly 600 according to the present invention is shown.

[0207] Therefore, the substrate 605 of the laser chip 601 has a width l which is less than 4 times the thickness of the substrate. In this example, the width l of the substrate is 1.5 to 3 times greater than the thickness e, preferably 2.5 times greater than the thickness e of the substrate 605 .

[0208] The laser chip includes three laser units 602 .

[0209] In this embodiment, the chip-substrate assembly 600 includes Figure 4 All features of the embodiment shown in are included, except that the chip-substrate assembly is in a “downward” position, ie, the laser unit 602 is positioned closer to the lower surface 609 than the upper surface 608 of the substrate 605 .

[0210] In this example, three positive polarity electrodes 603 are each electrically connected to a positive electrical trace 612 on substrate 611. Therefore, all laser units 602 electrically connected to said positive polarity electrodes 603 on the one hand and to negative electrodes 603 on the other hand have a current flowing through them.

[0211] The negative polarity electric trace 612 is in electrical contact with the negative polarity electrode 603 via an electric connector 613, which may be a gold wire connecting the electric trace 612 and the electrode 603, and the electric connector 613 is electrically connected to the electrode via a gold-based solder 614. The positive polarity electric trace 612 is in electrical contact with the positive polarity electrode via a bonding area 616 between the electric trace 612 and the electrode 603.

[0212] Figure 8 A chip-substrate assembly 700 in a seventh embodiment is shown.

[0213] In this embodiment, the chip-substrate assembly 700 includes Figure 2 All features of the illustrated embodiment, except for the laser unit 702 , are embedded in the substrate 705 of the chip 701 .

[0214] The substrate 705 of the laser chip 701 therefore has a width l which is less than 4 times the thickness of said substrate. In this example, the width l 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 .

[0215] The laser chip includes three 702 laser units.

[0216] In this embodiment, the laser unit 702 is closer to the top surface 708 of the substrate 705 than to the bottom surface 709 of the substrate 705 .

[0217] In this embodiment, only the positive electrode 703 is electrically connected to the electrical trace 712 on the substrate. Therefore, only the laser unit 702 has current flowing through it.

[0218] In another embodiment, several positive polarity electrodes 703 can be electrically connected to positive polarity electrical traces 712, such as Figure 3 and Figure 4 shown.

[0219] In an embodiment not shown here, the laser units 702 may be embedded in the substrate 705 in such a way that they are closer to the lower surface 709 of the substrate 705 than to the upper surface 708 of the substrate.

[0220] In this embodiment, the substrate includes a layer of semi-insulating material on either side of the 702 laser elements in order to electrically isolate them from each other.

[0221] Figures 2 to 7 The other features of the embodiments shown in apply here as well.

Claims

1. A semiconductor laser chip (101, 201, 301, 401, 501, 601, 701), the semiconductor laser chip comprising Substrate (105, 205, 305, 405, 505, 605, 705), including: o Two sides (107, 207, 307, 407, 507, 607, 707), o Lower surface (109, 209, 309, 409, 509, 609, 709), o Upper surface (108, 208, 308, 408, 508, 608, 708), at least two semiconductor lasers (202, 302, 402, 502, 602, 702), the two lasers (102, 202, 302, 402, 502, 602, 702) being distributed between the two side surfaces (102, 202, 302, 402, 502, 602, 702), and a spacing (E) being provided between two adjacent lasers (102, 202, 302, 402, 502, 602, 702), The substrate (105, 205, 305, 405, 505, 605, 705) has a width (l) and a thickness (e), wherein the width is the distance between the two side surfaces (107, 207, 307, 407, 507, 607, 707) of the substrate (105, 205, 305, 405, 505, 605, 705), and the thickness (e) is the distance measured perpendicular to the width (l) between the lower surface (109, 209, 309, 409, 509, 609, 709) and the upper surface (108, 208, 308, 408, 508, 608, 708, 808) of the substrate (105, 205, 305, 405, 505, 605, 705), and the width (l) is less than or equal to 4 times the thickness (e).

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

3. A chip according to any one of the preceding claims, characterized in that The chip comprises at least three laser units (102, 202, 302, 402, 502, 602, 702), wherein the three laser units (102, 202, 302, 402, 502, 602, 702) are distributed between the two side surfaces (107, 207, 307, 407, 507, 607, 707) of the substrate (105, 205, 305, 405, 505, 605, 705), and a spacing (E) is provided between two adjacent lasers (102, 202, 302, 402, 502, 602, 702).

4. A chip according to any one of the preceding claims, characterized in that The laser unit (102, 202, 302) is closer to the upper surface (108, 208, 308) of the substrate (105, 205, 305) than to the lower surface (109, 209, 309) of the substrate (105, 205, 305).

5. A chip according to any one of the preceding claims, characterized in that The chip comprises at least two electrodes (103, 203, 303, 403, 503, 603, 703) of different polarities, wherein the at least two electrodes are configured to allow current to pass through at least one laser unit (102, 202, 302, 402, 502, 602, 702) of the laser chip (101, 201, 301, 401, 501, 601, 701).

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

7. A chip according to any one of the preceding claims, characterized in that The substrate (105, 205, 305, 405, 505, 605, 705) includes at least one semiconductor material of InP, GaAs, GaSb, InAs, or silicon type material.

8. The chip according to claim 1, characterized in that The laser chip (101, 201, 301, 401, 501, 601, 701) is a quantum cascade laser chip comprising a quantum cascade laser unit (102, 202, 302, 402, 502, 602, 702).

9. A chip according to any 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 a pulsed mode at 4 to 10 microns.

10. Components (100, 200, 300, 400, 500, 600, 700), including: at least one laser chip ( 101 , 201 , 301 , 401 , 501 , 601 , 701 ) as claimed in any of the preceding claims, A substrate (111, 211, 311, 411, 511, 611, 711), on which the chip (101, 201, 301, 401, 501, 601, 701) is mounted.

11. Assembly according to the preceding claim, characterized in that The substrate (111, 211, 311, 411, 511, 611, 711) includes at least two electrical traces (112, 212, 312, 412, 512, 612, 712) having different polarities, each of the electrical traces (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) having the same polarity.

12. Assembly according to claim 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 2, and at most N-1 laser units (102, 202, 402, 502, 702) being electrically connected to the electrical traces (112, 212, 412, 512, 712) of the substrate (111, 211, 411, 511, 711).

13. An assembly according to any one of claims 10 to 12, characterized in that The chip-substrate assembly (100, 200, 300, 400, 500, 600, 700) comprises at least one laser chip (101, 201, 301, 401, 501, 601, 701), wherein the at least one laser chip (101, 201, 301, 401, 501, 601, 701) comprises at least N laser units (102, 202, 302, 402, 502, 602, 702), wherein N is greater than or equal to 2, and at least two laser units are configured to emit optical radiation of 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 so-called laser inlet aperture (40); At least one chip-substrate assembly (100, 200, 300, 400, 500, 600, 700) according to claims 10 to 13, comprising at least two laser units, at least one of the two laser units being configured to emit optical radiation into the cell (20), the optical radiation having a wavelength whose value is particularly suitable for the excitation of the gas to be detected, so that the interaction between the optical radiation and the gas to be detected contained in the cell induces a signal characteristic of the presence of the gas at a resonant frequency of the cell; and Signal detection device.

15. A process for producing a chip-substrate assembly (100, 200, 300, 400, 500, 600, 700) as claimed in any one of the preceding claims, comprising the following steps: The laser chip is formed by: o depositing a layer of material to form at least two laser units on a substrate, the laser units being spaced apart by a spacing in a width dimension of the substrate, the substrate having a thickness corresponding to a distance between an upper surface and a lower surface of the substrate, o cleaving the substrate to form two side surfaces of the substrate, the width of the substrate obtained corresponds to the distance between the two side surfaces obtained, the width being less than or equal to 4 times the thickness of the substrate, • Attach the resulting chip to a substrate.

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