A multi-spectrum laser chip TO package structure and a packaging method thereof

Abstract

This invention discloses a TO packaging structure and method for a multispectral laser chip, including a socket, a cap, and pins. A heat sink, shaped like a frustum or prism, is located in the upper center of the socket. A spectral detector is mounted on the upper surface of the heat sink. At least two sides of the heat sink are equipped with independently controllable thermoelectric coolers. A substrate is mounted on the side of each thermoelectric cooler furthest from the heat sink. Each substrate contains an independently controllable laser chip and a thermistor for temperature detection. The upper window of the cap has an optical window, and the socket has lead posts. The optical window is a metalens. This invention achieves integrated and miniaturized open multi-wavelength emission and multi-wavelength detection by packaging the spectral detector and multiple laser chips of different wavelengths onto the same socket. Each laser chip has individual temperature control, resulting in more precise output wavelength. A single metalens simultaneously shapes and converges the emitted beam and the reflected beam.

Description

Technical Field

[0001] This invention relates to the field of semiconductor chip packaging technology, and in particular to a TO packaging structure for a multispectral laser chip and its packaging method. Background Technology

[0002] In the field of gas detection, tunable semiconductor laser absorption spectroscopy (TDLAS) technology has become an important technique for trace gas detection due to its advantages such as high sensitivity, high resolution, and fast response. This technology utilizes the narrow linewidth and tunable wavelength of semiconductor lasers to accurately scan the characteristic absorption lines of the gas to be measured. Traditional TDLAS systems typically consist of discrete light source modules (laser and driver), optical path modules (lenses, optical fibers, gas cells), and detection modules (photodetectors). This discrete structure system is bulky, with complex optical path adjustments, making it unsuitable for portable field applications; furthermore, the coupling efficiency between discrete components is easily affected by environmental factors such as vibration and temperature changes, resulting in poor stability.

[0003] Existing technologies utilize the selective absorption characteristics of gas molecules for specific wavelengths of infrared light. A broadband light source illuminates a gas chamber, and a narrow-band filter designed for the characteristic absorption peaks of the target gas filters the wavelengths. Finally, the light intensity attenuation is converted into gas concentration according to the Lambert-Beer law. However, this technology suffers from energy dispersion in the broadband light source. If the filter bandwidth is not narrow enough or the out-of-band cutoff depth is insufficient, the purity of the monochromatic light will be poor, deviating from the Lambert-Beer law and leading to large errors in the calculation results.

[0004] To address the aforementioned issues, in recent years, multiple chips (such as laser chips of different wavelengths, detector chips, or detector arrays with integrated filters) have been packaged in a single TO-type housing to achieve integrated detection of multiple gases. This approach offers significant advantages in reducing system size, but it also introduces challenges in thermal management and optical shaping.

[0005] Multi-chip TO packages mostly employ a unified temperature control scheme, making it impossible to achieve independent temperature control for individual chips. Different wavelengths and models of laser chips have different rated operating temperatures, and unified temperature control can easily lead to abnormal operating temperatures of some chips, thereby affecting the stability of the emitted wavelength and making it difficult to guarantee detection accuracy.

[0006] In terms of optical shaping, traditional TO package optical windows mostly use ordinary lenses, which usually have only one optical axis. Chips at the edge of the field of view will produce coma and astigmatism, resulting in distortion of the emitted light pattern. Moreover, it is impossible to shape the emitted and reflected light simultaneously, making it difficult to cooperate with the detector to achieve efficient optical signal reception, resulting in poor overall performance.

[0007] In summary, existing multispectral laser TO packaging structures suffer from numerous drawbacks, including large size, inaccurate temperature control, poor optical shaping, and low integration, which hinder the performance improvement and application expansion of multispectral laser devices. Therefore, developing a multispectral laser chip TO packaging structure with high integration, small size, independent temperature control, and precise optical shaping has become a pressing technical problem for those skilled in the art. Summary of the Invention

[0008] The purpose of this invention is to provide a TO packaging structure and packaging method for a multispectral laser chip, so as to solve the problems mentioned in the background art.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a multispectral laser chip TO packaging structure, including a socket, a cap disposed above the socket, and several pins vertically passing through the socket. A heat sink is disposed in the middle upper part of the socket. The heat sink is a frustum or prism structure. A spectral detector is disposed on the upper surface of the heat sink. At least two sides of the heat sink are provided with independently controllable thermoelectric coolers. A substrate is mounted on the side of each thermoelectric cooler away from the heat sink. Each substrate is provided with an independently controllable laser chip and a thermistor for temperature detection of the laser chip. The heat sink, substrate, laser chip, thermistor, thermoelectric cooler, and spectral detector are all disposed inside the cap. The upper window of the cap is provided with an optical window. Several lead posts are disposed on the socket. The optical window is a metalens.

[0010] Further optimization involves ensuring that at least two of the laser chips on the heat sink have different emission wavelengths.

[0011] Further optimization involves the laser chip being a single-mode laser chip, where the wavelength and power of each laser chip can be independently tuned by temperature and / or current.

[0012] Further optimization allows the laser chip's wavelength to cover near-infrared to far-infrared light.

[0013] Further optimizations include the ability of the spectral detector to operate at room temperature or under active temperature control via a thermoelectric cooler; the spectral detector is a broadband detector with wavelengths covering near-infrared to far-infrared light.

[0014] Further optimization involves the arrangement of a microstructure column array in the functional area of ​​the metalens, and the metalens is fabricated using a double-sided metalens process.

[0015] Further optimization involves the heat sink having a cross-section that is any one of a regular polygon, a rectangle, or a trapezoid.

[0016] This application also discloses a packaging method for a multispectral laser chip TO package structure, based on the aforementioned multispectral laser chip TO package structure, comprising the following steps:

[0017] Step 1: Mounting thermistors. A pick-and-place machine is used to mount multiple thermistors onto corresponding mounting areas on multiple substrates, wherein one thermistor is mounted on one substrate.

[0018] Step 2: Mount the laser chip. Mount one laser chip on each substrate with a thermistor and use a eutectic bonding machine to eutectic bond the laser chip and the substrate.

[0019] Step 3: Wire bonding of the laser chip to the substrate. The electrodes of the laser chip are wire bonded to the corresponding welding areas on the substrate using a wire bonding machine, so that the laser chip and the substrate form an electrical interconnection.

[0020] Step 4: Mount the thermoelectric cooler. Mount each substrate with a thermistor and laser chip onto the upper surface of each thermoelectric cooler.

[0021] Step 5: The thermoelectric cooler is mounted on the side of the heat sink. The lower surface of the thermoelectric cooler is mounted on the side of the heat sink using a pick-and-place machine. Then, according to the emission wavelength of the laser chip mounted on each thermoelectric cooler, the thermoelectric cooler is sequentially attached to each side of the heat sink.

[0022] Step 6: Mount the detector. Use a pick-and-place machine to mount the spectral detector onto the upper surface of the heat sink.

[0023] Step 7: The components inside the tube cap are bonded to the lead posts. All the lead ends of the thermistors, substrates, thermoelectric coolers, and spectral detectors are bonded to the corresponding lead posts on the tube base using conductive wires on a wire bonding machine to form electrical interconnections.

[0024] Step 8, sealing: In a vacuum environment or inert gas environment, the tube cap and tube seat are hermetically sealed in a sealing machine to complete the sealing process.

[0025] Beneficial effects: The multispectral laser chip TO packaging structure of the present invention has a truncated pyramidal heat sink, and a laser chip can be installed on each side. By packaging multiple laser chips in the same packaging structure, multiple laser chips can emit lasers simultaneously or in sequence, which can greatly reduce the packaging process, reduce the packaging volume, realize multispectral TO packaging, and meet the needs of simultaneous detection of multiple gases by using multiple laser chips with different wavelengths.

[0026] By packaging the spectral detector and multi-wavelength laser chip on the same socket, the light emitted by the laser chip is directly projected into the external free space, and the reflected light after absorption by the gas to be measured is also received by the detector in free space. This eliminates the need for optical fibers or gas chambers, achieving integrated and miniaturized open-loop multi-wavelength emission and detection. Each laser chip is equipped with an independently controlled thermoelectric cooler, enabling independent temperature control of the laser chip and thus achieving wavelength tunability for each laser chip. This solves the technical challenge of not being able to individually control the temperature of each chip when multiple chips are packaged on the same socket. Compared to traditional filter solutions, this method offers more precise wavelength control, higher packaging efficiency, and a smaller size.

[0027] The meta-lens enables precise shaping of laser beams on each side, transforming elliptical beams from oblique or perpendicular incident light from each laser chip into parallel beams. Simultaneously, it converges the reflected light after absorption by the gas under test onto the detector. This allows a single meta-lens to shape both the emitted light and the incident light after absorption by the gas under test, solving the technical challenge of traditional optical window lenses in accurately shaping various types of beams. Attached Figure Description

[0028] Figure 1 This is a three-dimensional structural diagram of the TO package structure of the multispectral laser chip disclosed in this invention without a tube cap.

[0029] Figure 2 This is a three-dimensional structural diagram of the TO package structure of the multispectral laser chip disclosed in this invention;

[0030] Figure 3 This is a schematic diagram of the internal structure of the TO package structure of the multispectral laser chip disclosed in this invention.

[0031] Figure 4 This is a schematic diagram of the meta-lens beam shaping disclosed in this invention;

[0032] Figure 5 This is a schematic diagram of laser emission from the TO package structure of the multispectral laser chip disclosed in this invention.

[0033] Figure 6 This is a schematic diagram of laser emission in the TO package structure of the multispectral laser chip disclosed in this invention when there is no optical window;

[0034] Figure 7 This is a schematic diagram of the working state of the TO package structure of the multispectral laser chip disclosed in this invention.

[0035] Figure 8 This is a schematic diagram of the spectral absorption of four gases disclosed in this invention;

[0036] Figure 9This is a schematic diagram of the packaging process for the TO package structure of the multispectral laser chip disclosed in this invention.

[0037] Reference numerals: 1-Socket, 2-Pin, 3-Heat sink, 4-Substrate, 5-Laser chip, 6-Thermistor, 7-Thermoelectric cooler, 8-Lead post, 9-Cap, 10-Optical window, 11-Spectrometer detector. Detailed Implementation

[0038] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0039] like Figure 1-8 As shown, this application discloses a multispectral laser chip TO packaging structure, including a tube socket 1, a tube cap 9 disposed above the tube socket 1, and several pins 2 vertically passing through the tube socket 1. A heat sink 3 is disposed in the middle upper part of the tube socket 1. The heat sink 3 is a frustum or prism structure. A spectral detector 11 is disposed on the upper surface of the heat sink 3. At least two sides of the heat sink 3 are provided with independently controllable thermoelectric coolers 7. A substrate 4 is mounted on the side of each thermoelectric cooler 7 away from the heat sink. Each substrate 4 is provided with an independently controllable laser chip 5 and a thermistor 6 for temperature detection of the laser chip 5. The heat sink 3, substrate 4, laser chip 5, thermistor 6, thermoelectric cooler 7 and spectral detector 11 are all disposed inside the tube cap 9. A light window 10 is provided at the upper end of the tube cap 9. Several lead posts 8 are provided on the tube socket 1. The light window 10 is a metalens.

[0040] In this application, the multispectral laser chip TO package structure is applied in the laser field. It features a robust structure, excellent heat dissipation, and low cost, representing a miniaturized and highly reliable semiconductor device package structure. This multispectral laser chip TO package structure includes a socket 1, pins 2, a heat sink 3, a substrate 4, a laser chip 5, a thermistor 6, a thermoelectric cooler 7, lead posts 8, a cap 9, an optical window 10, and a spectral detector 11. The socket 1 serves as the basic support structure for the package, supporting the heat sink 3 and the substrate 4, laser chip 5, thermistor 6, thermoelectric cooler 7, and lead posts 8 mounted on it. It also houses the pins 2 and serves as a heat conductor and dissipator. The pins 2 are used for electrical connections between components within the enclosed cavity and external circuitry. These connections are achieved through the lead posts 8 located above the socket 1, enabling the transmission of the laser chip 5's drive current, the thermoelectric cooler 7's control signals, and the thermistor 6's temperature feedback signals. The heat sink 3, as a highly efficient heat-conducting medium, rapidly dissipates the heat generated by the laser chip 5 to the external environment, increasing the heat dissipation area. The substrate 4 is used for mounting the laser chip 5 and the thermistor 6, as well as providing electrical interconnection, mechanical support, and heat conduction. The laser chip 5 is a narrow-linewidth semiconductor laser, serving as the light-emitting element to output laser light of a specific wavelength. The thermistor 6 is used to sense the temperature of the laser chip 5's housing in real time and accurately, converting temperature changes into electrical signals to form a temperature monitoring and closed-loop control circuit, ensuring stable operation of the laser chip 5. Thermoelectric cooler 7 is used to control cooling or heating, precisely regulating the temperature of the laser chip 5. Lead posts 8 are used to connect to the substrate 4, the thermistor 6, and the thermoelectric cooler 7. A cap 9 connects to the base 1 to form a closed cavity, which is a vacuum or inert gas environment, isolating external moisture and oxygen and reducing particulate matter contamination. A light window 10 is used for the transmission of the laser light emitted by the laser chip 5, achieving efficient laser transmission and shaping, and optimizing laser output characteristics. A spectrometer 11 is used to receive the reflected light, and by detecting changes in the intensity of the received reflected light, the concentration of the corresponding gas is determined. By encapsulating the spectral detector 11 and multiple laser chips in the same package, the integration and miniaturization of open multi-wavelength emission and multi-wavelength detection are achieved.

[0041] In this application, the heat sink 3 is a frustum or prism structure with multiple sides, each side having a substrate 4, and each substrate 4 corresponding to a laser chip 5. The laser emitted by the laser chip 5 mounted on the substrate 4 on each side of the heat sink 3 can be focused onto the upper optical window 10 and transmitted out. Therefore, encapsulating multiple laser chips 5 in the same packaging structure can greatly reduce the packaging process and shrink the packaging structure. By encapsulating multiple laser chips 5 in the same packaging structure, a multi-in-one laser TO package is achieved. At the same time, it is not necessary to encapsulate multiple individual chips independently, arrange multiple independent packaging structures simultaneously in a cavity, and set up a beam combiner, which would result in a particularly large final package volume.

[0042] In this application, the heat sink 3 and the tube base 1 are integrally formed, resulting in high structural strength, eliminating contact thermal resistance, and improving thermal coupling efficiency. The heat sink 3 has a frustum-shaped structure, which allows multiple laser chips 5 mounted on the side of the heat sink 3 to form a uniform circular array. Light emitted from each side of the heat sink 3 converges to the optical window 10 to form coaxial light, effectively avoiding phase difference and optical path difference when beams overlap.

[0043] In this application, each laser chip 5 is independently controlled. The heat sink 3, with its prism structure and multiple sides, allows for the mounting of multiple laser chips 5. Independent control of each laser chip 5 enables a single TO tube to emit multiple wavelengths of laser light. Compared to traditional filter solutions, this results in more precise wavelengths, higher packaging efficiency, and a smaller size. Multiple laser chips 5 can emit lasers simultaneously or sequentially. Simultaneous emission results in higher optical power; sequential emission avoids power degradation caused by prolonged operation of a single chip, delaying laser attenuation and improving the reliability of the laser TO packaging structure. Furthermore, multiple laser chips 5 can be configured to activate only some chips based on the required optical power, adapting to different operating scenarios and offering high applicability. Each thermoelectric cooler 7 is independently controllable, solving the technical challenge of individually controlling the temperature of each laser chip 5 when packaging multiple laser chips 5 within the same socket 1.

[0044] In this application, the optical window 10 is a metalens, which is typically made of a high-refractive-index dielectric material, and a "meta-surface" composed of countless subwavelength nanostructure arrays is fabricated on its surface. This metalens can shape the tilted elliptical light emitted from the laser chip 5 into parallel light, greatly improving performance and integration. The optical window 10 is a metalens, and its material is titanium dioxide, gallium nitride, silicon, etc., and its diameter matches the opening size on the cap 9.

[0045] In one embodiment of this application, at least two of the laser chips 5 on the heat sink 3 have different emission wavelengths. Laser chips 5 with the same emission wavelength can meet the application requirements of wavelength combining and wavelength locking, achieving high beam combining efficiency. Simultaneously, the same wavelength beams can achieve collinearity and polarization maintenance. Depending on the number of activated chips, flexible switching between low-power, high-precision and high-power, high-energy applications is possible. Laser chips 5 with different emission wavelengths can be used in multi-wavelength application scenarios without changing the laser TO package structure, significantly improving the versatility and applicability of the equipment. They can also meet the needs of multi-wavelength applications, such as in the detection of various gases, where multi-wavelength combinations can improve detection coverage and accuracy.

[0046] In another embodiment of this application, the laser chip is a single-mode laser chip, and the wavelength and power of each laser chip can be independently tuned by temperature and / or current.

[0047] Among them, the single-mode laser chip possesses excellent single-longitudinal-mode and single-transverse-mode output characteristics, with high output beam quality and good coherence, effectively avoiding the technical defects of multi-mode laser output such as beam divergence, spectral disorder, and poor output stability. The wavelength and power of each laser chip 5 can be independently tuned, achieving precise tuning through the adjustment of a single or dual variable in the chip's operating temperature and driving current. Specifically, fine tuning is achieved by changing the injection current, with a tuning coefficient of 0.02 nm / mA, and the chip temperature is controlled by the thermoelectric cooler 7, with a tuning coefficient of 0.10 nm / °C. By controlling the current and temperature, the laser chip 5 outputs the characteristic absorption wavelength of the target gas. The tuning channels of each laser chip 5 are independent of each other; the wavelength and power tuning process of a single laser chip 5 will not cause crosstalk or interference to the operating status and output parameters of other chips, realizing independent configuration, precise calibration, and dynamic control of multi-channel laser output parameters.

[0048] In another embodiment of this application, the wavelength of the laser chip 5 covers the range from near-infrared to far-infrared light. The wavelength that matches the absorption peak of the gas to be measured is selected according to the type of target gas, and the overall wavelength coverage range is 700nm-14μm.

[0049] In another embodiment of this application, the spectral detector 11 is a broadband detector with wavelengths covering near-infrared to far-infrared light, and an overall detection band of 700nm-14μm. It can accurately sense, convert photoelectric signals and acquire signals of different wavelengths within this band. It has wide-band blind-zone detection, high spectral responsivity and signal acquisition stability. It can be adapted to the near-infrared to far-infrared broadband laser output of the laser chip 5 to achieve synchronous detection of the reflected light signal after laser emission. There is no need to configure additional multi-band dedicated detection components, which effectively simplifies the overall structure of the detection system, while ensuring the consistency and accuracy of the detection of light signals across the entire band.

[0050] In this embodiment, the spectrometer 11 can operate at room temperature or under active temperature control by the thermoelectric cooler 7. That is, it can operate normally at room temperature (20-25°C) without further cooling, which can reduce power consumption; or it can operate under active temperature control by the thermoelectric cooler 7, which can accurately control the temperature and ensure the stable temperature of the working environment of the spectrometer 11.

[0051] In this embodiment, a wavelength suitable for the absorption peak of the gas to be measured is selected according to the type of the target gas, with an overall wavelength coverage range of 700nm-14μm. The laser chip 5 and the spectral detector 11 can be selected according to the characteristic absorption wavelength of the gas to be measured, specifically:

[0052] When the wavelength of the absorption peak of the gas to be measured is in the near-infrared range of 700nm-2.5μm, the laser chip 5 is selected as a gallium arsenide (GaAs) based or indium phosphide (InP) based distributed feedback (DFB) semiconductor laser chip; the corresponding spectral detector 11 is preferably a silicon or indium gallium arsenide (InGaAs) detector.

[0053] When the wavelength of the absorption peak of the gas to be measured is in the 2.0μm-14μm band, the laser chip 5 is an antimony single-mode DFB semiconductor laser chip, preferably an interband cascade laser (ICL) chip with DFB structure, which has the advantages of low threshold current, low power consumption and easy integration; the corresponding spectral detector 11 is an antimony infrared detector, preferably a high operating temperature (HOT) antimony infrared detector or a mercury cadmium telluride (HgCdTe) infrared detector.

[0054] In another embodiment of this application, the functional area of ​​the metalens is provided with an array of microstructure pillars. The feature size and period of this array of microstructure pillars are smaller than the working wavelength, and the aspect ratio (height / feature size) of the pillars is typically controlled within 10:1. This microstructure pillar can optically control incident / emitted light signals in the near-infrared to far-infrared bands, effectively reducing light reflection loss on the optical window surface, improving the light transmission efficiency, and suppressing stray light interference. It also reduces dispersion and distortion problems during light signal transmission, ensuring the integrity and accuracy of broadband light signals transmitted through the optical window 10.

[0055] Furthermore, the metalens is fabricated using a double-sided metalens process, which can shape the vertically or obliquely incident elliptical light emitted from the laser chip into circular parallel light for emission. Simultaneously, it can shape and converge the reflected light emitted from the laser chip 5 onto the surface of the spectral detector, achieving simultaneous shaping of both emitted and reflected light. Based on the wavelength of the emitted light from the laser chip 5 and its position, a suitable micro-pillar array structure is designed, allowing the vertically or obliquely incident elliptical light emitted from each side of the heat sink 3 to be individually shaped into parallel light after passing through the metalens. Simultaneously, these emitted lights of different wavelengths are absorbed by the gas to be measured and reflected back to the metalens. After being shaped by the metalens, they converge onto the spectral detector 11 on the upper surface of the tube base 1. The edge area of ​​the metalens is used for bonding or laser welding with the tube cap 9, forming a sealed integrated structure to ensure airtightness.

[0056] In another embodiment of this application, after the cap 9 is sealed, its cavity is a vacuum or inert gas environment. The cap 9 is welded to the base 1, and after welding, the cavity of the cap 9 is a sealed cavity, effectively preventing external media from entering the sealed cavity and avoiding leakage of the filling medium inside the cavity. By creating a vacuum or inert gas environment inside the cavity, the inert gas environment provides a high-purity, high-stability, and low-risk working environment for the thermoelectric cooler 7, the laser chip 5, and the thermistor 6. This environment can isolate oxidation and corrosion, extend the service life of each component, suppress thermal disturbances, improve temperature control accuracy, and provide insulation and arc prevention, ensuring the reliability of the internal chips and circuits. It can also reduce scattering and contamination, maintaining laser transmission efficiency. The vacuum environment can create an extreme environment free from gas interference, isolating oxidation, corrosion, and contamination, extending the service life of each component, eliminating gas convection and heat conduction, improving temperature control accuracy, and possessing ultra-high insulation strength, preventing arcing and discharge. This ensures that no gas molecules scatter the laser within the sealed cavity, nor adsorb the laser, thus maximizing laser transmission efficiency.

[0057] In another embodiment of this application, the cross-section of the heat sink 3 is any one of a regular polygon, rectangle, or trapezoid. The heat sink 3 adopts a regular three-dimensional structure of frustum or prism, which can effectively increase the heat dissipation surface area. The cross-section of the heat sink 3 can be selected from three regular shapes: regular polygon, rectangle, or trapezoid. These three shapes can be flexibly selected according to actual packaging requirements, chip quantity, and heat dissipation requirements, and all can form a good fit with the overall structure of the TO package.

[0058] In this application, the tube base 1 is made of Kovar alloy with a diameter of 8-12 mm. The heat sink 3 on the upper surface of the tube base 1 is a regular square truncated pyramid with a square cross-section. The upper surface of the square truncated pyramid has a side length of 5 mm, the lower surface has a side length of 6 mm, and the height is 5 mm. A single-stage thermoelectric cooler 7 with a power of 1.2 watts is mounted on each of its four sides. The thermoelectric cooler 7 has a side length of 5 mm × 5 mm and a thickness of 1 mm. A substrate 4, which is an aluminum nitride ceramic substrate, is mounted on the upper surface of the thermoelectric cooler 7. Each aluminum nitride ceramic substrate has a laser chip 5 mounted on it, and the four laser chips 5 have different wavelengths. Depending on the type of gas to be measured, a laser chip 5 covering the absorption peak of the gas to be measured is selected, and a spectrometer 11 covering the aforementioned wavelengths is used, enabling the detection of four different gases. Specifically, the wavelengths of the four laser chips 5 are 1653nm, 1572nm, 1511nm and 1310nm, respectively, which correspond to the absorption peaks of methane, carbon dioxide, ammonia and hydrogen fluoride gases, and can detect the above four gases.

[0059] Gas detection principle: Methane, carbon dioxide, ammonia, and hydrogen fluoride gases each have their own characteristic absorption bands in the infrared band. The absorption of infrared energy through these bands reflects the gas concentration. Spectrometers determine the gas concentration by detecting changes in the intensity of four types of reflected light. The light intensity reaching the detector is inversely proportional to the gas concentration; higher concentrations absorb more infrared light than lower concentrations.

[0060] The selective absorption of infrared radiation by gases follows the Lambert-Beer Law: Where I0 is the infrared radiation intensity before passing through the medium, I is the radiation intensity after absorption by the medium, and C is the concentration of the gas being measured. Gas absorption coefficient, where L is the path length. Let be the optical path coupling efficiency. From the above equation, it can be seen that the intensity of absorbed radiation is a function of gas concentration, path length, and gas absorption coefficient. The higher the gas concentration and the longer the absorption path, the greater the loss of radiation intensity.

[0061] In this application, the laser chip 5 is preferably a single-mode DFB laser chip, employing an InP-based quantum well DFB structure. Each laser chip 5 corresponds to a characteristic absorption wavelength of the gas to be measured, such as methane (1653 nm), carbon dioxide (1572 nm), ammonia (1511 nm), and hydrogen fluoride (1310 nm). The spectrometer 11 is preferably an InGaAs PIN detector with a response range of 0.8 µm-2.0 µm, covering the aforementioned gas absorption wavelengths. By detecting changes in the intensity of the received reflected light, the concentration of the corresponding gas is determined. By encapsulating the spectrometer 11 and multiple laser chips 5 within a single package, integrated and miniaturized open-loop multi-wavelength emission and multi-wavelength detection are achieved.

[0062] like Figure 9 As shown, this invention also discloses a packaging method for a multispectral laser chip TO package structure, based on the multispectral laser chip TO package structure, comprising the following steps:

[0063] Step 1: Mounting thermistors 6. Multiple thermistors 6 are mounted on corresponding mounting areas on multiple substrates 4, with one thermistor 6 mounted on one substrate 4. The thermistors 6 are mounted on the mounting area of ​​the thermistor 6 on the substrate 4 using a pick-and-place machine with solder (solder paste, silver paste, gold-tin alloy, indium, etc.) and close to the light-emitting end of the laser chip 5. After the solder is heated and cured, the thermistor 6 and the substrate 4 are bonded together to form an integral unit. After mounting multiple substrates 4 with thermistors 6, they are cured uniformly. The heating temperature depends on the solder temperature, and the mounting accuracy is controlled within ±7μm.

[0064] Step 2: Mount the laser chip 5. Mount one laser chip 5 on each substrate 4 on which the thermistor 6 is mounted. Use a eutectic bonding machine to bond the laser chip 5 and the eutectic region of the substrate 4 together. Eutectic bonding is performed on the eutectic stage. The heating temperature must be lower than the curing temperature of the thermistor 6. The mounting accuracy is controlled within ±5μm.

[0065] Step 3: Wire bonding of laser chip 5 to substrate 4. The electrodes of laser chip 5 are wire bonded to the corresponding welding areas on substrate 4 using conductive wires on a wire bonding machine, so that laser chip 5 and substrate 4 form an electrical interconnection.

[0066] Step 4: Mount the thermoelectric cooler 7. Mount each substrate 4 with the thermistor 6 and laser chip 5 onto a thermoelectric cooler 7. Use a pick-and-place machine to mount the substrate 4 onto the side of the thermoelectric cooler 7 away from the heat sink using solder (solder paste, silver paste, gold-tin alloy, indium, etc.).

[0067] Step 5: The thermoelectric cooler 7 is attached to the side of the heat sink 3. Using a pick-and-place machine, the side of the thermoelectric cooler 7 closest to the heat sink is attached to the side of the heat sink 3 on the tube seat 1 with solder. Then, according to the emission wavelength of the laser chip 5 attached to each thermoelectric cooler 7, the thermoelectric cooler 7 is attached to each side of the heat sink 3 in sequence. When attaching, the tube seat 1 is placed horizontally in the pick-and-place machine. After each side is attached, it is heated and cured before attaching the other side, until the thermoelectric cooler 7 is attached to all sides of the heat sink 3.

[0068] Step 6: Mount the detector. Use a pick-and-place machine to mount the spectral detector 11 onto the upper surface of the heat sink 3. The solder used is solder paste, silver paste, gold-tin alloy, indium, etc.

[0069] Step 7: The components inside the tube cap are bonded to the lead posts. All the mounted and cured thermistors 6, substrate 4, thermoelectric cooler 7 and spectral detector 11 are bonded to the corresponding lead posts 8 on the tube base 1 using conductive wires on a wire bonding machine to form electrical interconnections.

[0070] Step 8: Sealing. In a vacuum environment or inert gas environment, the tube cap 9 and the tube seat 1 are hermetically sealed in a sealing machine to complete the sealing process.

[0071] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A multi-spectrum laser chip TO package structure, comprising a tube base, a tube cap arranged above the tube base, and a plurality of pins vertically penetrating through the tube base, and a heat sink arranged above the middle of the tube base, characterized in that, The heat sink has a frustum or prism structure. A spectral detector is provided on the upper surface of the heat sink. At least two sides of the heat sink are provided with independently controllable thermoelectric coolers. A substrate is mounted on the side of each thermoelectric cooler away from the heat sink. Each substrate is provided with an independently controllable laser chip and a thermistor for temperature detection of the laser chip. The heat sink, substrate, laser chip, thermistor, thermoelectric cooler and spectral detector are all disposed inside a tube cap. The upper window of the tube cap is provided with a light window. Several lead posts are provided on the tube base. The light window is a meta-lens.

2. The multispectral laser chip TO packaging structure according to claim 1, characterized in that, At least two of the laser chips on the heat sink have different emission wavelengths.

3. The multispectral laser chip TO packaging structure according to claim 1, characterized in that, The laser chip is a single-mode laser chip, and the wavelength and power of each laser chip can be independently tuned by temperature and / or current.

4. The multispectral laser chip TO packaging structure according to claim 1, characterized in that, The wavelength of the laser chip covers the range from near-infrared to far-infrared light.

5. The multispectral laser chip TO packaging structure according to claim 1, characterized in that, The spectral detector can operate at room temperature or under active temperature control via a thermoelectric cooler; the spectral detector is a broadband detector, with wavelengths covering near-infrared to far-infrared light.

6. The multispectral laser chip TO packaging structure according to claim 1, characterized in that, The functional area of ​​the metalens is provided with an array of microstructured pillars, and the metalens is fabricated using a double-sided metalens process.

7. The multispectral laser chip TO packaging structure according to claim 1, characterized in that, The heat sink has a cross-section that is any one of a regular polygon, a rectangle, or a trapezoid.

8. A packaging method for a multispectral laser chip TO package structure, characterized in that, The multispectral laser chip TO packaging structure according to any one of claims 1-7 includes the following steps: Step 1: Mounting thermistors. A pick-and-place machine is used to mount multiple thermistors onto corresponding mounting areas on multiple substrates, wherein one thermistor is mounted on one substrate. Step 2: Mount the laser chip. Mount one laser chip on each substrate with a thermistor and use a eutectic bonding machine to eutectic bond the laser chip and the substrate. Step 3: Wire bonding of the laser chip to the substrate. The electrodes of the laser chip are wire bonded to the corresponding welding areas on the substrate using a wire bonding machine, so that the laser chip and the substrate form an electrical interconnection. Step 4: Mount the thermoelectric cooler. Mount each substrate with a thermistor and laser chip onto the upper surface of each thermoelectric cooler. Step 5: The thermoelectric cooler is mounted on the side of the heat sink. The lower surface of the thermoelectric cooler is mounted on the side of the heat sink using a pick-and-place machine. Then, according to the emission wavelength of the laser chip mounted on each thermoelectric cooler, the thermoelectric cooler is sequentially attached to each side of the heat sink. Step 6: Mount the detector. Use a pick-and-place machine to mount the spectral detector onto the upper surface of the heat sink. Step 7: The components inside the tube cap are bonded to the lead posts. All the lead ends of the thermistors, substrates, thermoelectric coolers, and spectral detectors are bonded to the corresponding lead posts on the tube base using conductive wires on a wire bonding machine to form electrical interconnections. Step 8, sealing: In a vacuum environment or inert gas environment, the cap and the tube seat are hermetically sealed in a capping machine to complete the capping process.

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