Miniaturized pumping optical module based on VCSEL laser

Abstract

The invention discloses a miniaturized pumping optical module based on a VCSEL (Vertical Cavity Surface Emitting Laser), which can realize miniaturization of the optical module through optical element layout and low-stress and less-stray-light installation, thereby being beneficial to meeting the requirements of performance test and pursuing of ultrahigh sensitivity by a large scientific device, and is characterized in that the miniaturized pumping optical module comprises a shell, the shell is formed by overlapping a photosensitive resin lower-layer structure shell, a photosensitive resin middle-layer structure shell and a photosensitive resin upper-layer structure shell layer by layer, a large gear and a small gear are arranged on the top face of the upper-layer structure shell, and a cylindrical groove where a quarter-wave plate is embedded is formed in the inner wall face of a center hole of the large gear. A VCSEL laser and a photoelectric detector which are parallel are arranged on the top face of the lower-layer structure shell, a polarization splitting prism is arranged in the upper-layer structure shell, a collimating lens set formed by overlapping a concave lens and a convex lens is arranged in a light source channel in the middle-layer structure shell, the transmission side of the polarization splitting prism is aligned with the quarter-wave plate, and the transmission side of the collimating lens set is aligned with the quarter-wave plate. The reflection side of the polarization splitting prism is connected with a photoelectric detector.

Description

Technical Field

[0001] This invention belongs to the field of pump optical path technology, and in particular, a miniaturized pump optical module based on a VCSEL laser. Through the layout of optical elements and the installation of low-stress and low-stray-light, the optical module can be miniaturized, which is beneficial to meeting the requirements of performance testing and the pursuit of ultra-high sensitivity in large scientific facilities. Background Technology

[0002] Navigation systems play a vital role in people's daily travel. my country's independently developed and manufactured BeiDou Navigation Satellite System (BDS) is one such system and is gradually becoming one of the world's leading navigation systems. However, in some special environments (such as the deep sea and caves), its navigation capabilities can be severely reduced. In these situations, inertial navigation systems can still provide accurate navigation even when BDS is inaccurate. In terms of precise positioning, inertial navigation systems are autonomous navigation systems that do not rely on external information or radiate energy. They involve a comprehensive technology encompassing physics, mathematics, mechanics, optics, materials science, precision mechanics, microelectronics, computers, control, testing, and advanced manufacturing processes, and are one of the important indicators of a country's advanced technological level. Compared with other navigation systems, inertial navigation systems possess important characteristics such as comprehensive information, complete autonomy, high degree of concealment, real-time and continuous information, and are not limited by time, location, or human interference. They can be applied in various scenarios, including land, sea, and air. With the continuous advancement of the information age and the development of fields such as intelligent robots, autonomous driving, virtual reality, and smart homes, the requirements for high precision, low cost, and miniaturization of inertial navigation systems are becoming increasingly stringent.

[0003] Inertial navigation technology is the core and a hallmark of inertial technology. The core components of an inertial navigation system (INS) are gyroscopes and accelerometers. Currently, research on accelerometers is relatively mature, and various technical solutions for miniature accelerometers have been developed and applied. The key to further breakthroughs in inertial navigation systems lies in gyroscopes. Gyroscopes can be divided into three categories. The first category is electromechanical gyroscopes that apply Newtonian mechanics, including high-precision gyroscopes. This type of gyroscope has been developing since the 1950s. Today, high-precision triple-buoyancy and electrostatic gyroscopes can be used in strategic-level inertial navigation, but they are generally large and expensive, failing to meet the demands for miniaturization and low cost. The second category is microelectromechanical systems (MEMS) that apply Newtonian mechanics. System (MEMS) gyroscopes can meet the requirements of miniaturization and low cost, but their accuracy is relatively poor. Due to the scale effect, their accuracy cannot be improved theoretically, and they cannot meet the requirements of high precision. The second type of gyroscope is the optical gyroscope, which utilizes the Sagnac effect (Sagnac, the inventor of the rotating ring interferometer). However, its accuracy is proportional to its size, and it is also difficult to meet the miniaturization and high precision requirements of the inertial navigation development trend. The third type of gyroscope is the atomic gyroscope. This type of gyroscope uses lasers to manipulate the macroscopic angular momentum of individual atoms. Since the friction at the atomic level is zero, it can theoretically achieve strategic or tactical level precision. Moreover, because it is manipulated at the atomic scale, it is easy to miniaturize and has broad development prospects.

[0004] Atomic gyroscopes are divided into atomic spin gyroscopes and atomic interferometric gyroscopes. Atomic spin gyroscopes mainly include spin exchange relaxation-free gyroscopes (SERFG) and nuclear magnetic resonance gyroscopes (NMRG). NMR gyroscopes hold promise for chip-based fabrication using mature micromachining technology and possess strategic-level theoretical precision at the mechanistic level, meeting the high precision, low cost, and miniaturization requirements of inertial navigation technology. They are currently a research hotspot in the field of gyroscopes.

[0005] The principle of a nuclear magnetic resonance gyroscope is to detect the angular velocity of a carrier by utilizing the interaction between a laser and alkali metal atoms and inert gas atoms in the gyroscope's gas chamber. The laser, as the core signal source of the NMR gyroscope, directly affects its performance. Due to the influence of factors such as ambient temperature, vibration, and electromagnetic interference, the laser frequency drifts significantly in the open-loop state. On the one hand, laser frequency fluctuations directly cause fluctuations in the system's calibration coefficients, leading to gyroscope drift. On the other hand, if the laser frequency parameters cannot be stabilized at the optimal level, it will amplify optical rotation noise, ultimately amplifying the gyroscope's output noise. To improve the performance of the NMR gyroscope, laser power detection and monitoring are also necessary.

[0006] In terms of light source module design, there is a significant demand for VCSEL optical path designs that meet pumping requirements. Miniaturized modules designed by combining miniaturized optical paths with frequency stabilization systems can be applied to laboratory nuclear magnetic resonance gyroscopes, thus fulfilling and achieving miniaturization requirements.

[0007] Therefore, conducting research on miniaturized VCSEL laser pump optical systems suitable for nuclear magnetic resonance gyroscopes and combining them with small modules, and completing the corresponding optical pump module, optical path, circuit and program design, is of great significance for the experimental project group to realize the chip-based device and promote the miniaturization and integration of nuclear magnetic resonance gyroscopes. Summary of the Invention

[0008] This invention addresses the deficiencies or shortcomings of existing technologies by providing a miniaturized pump optical module based on a VCSEL laser. Through the layout of optical components and the installation of low-stress, low-stray-light components, the miniaturization of the optical module can be achieved, thereby helping to meet the requirements of performance testing and the pursuit of ultra-high sensitivity in large scientific facilities.

[0009] The technical solution of the present invention is as follows:

[0010] A miniaturized pump optical module based on a VCSEL laser is characterized by comprising a housing, which is formed by stacking a lower photosensitive resin structure, a middle photosensitive resin structure, and an upper photosensitive resin structure layer by layer. The top surface of the upper photosensitive resin structure has a meshing large gear and a small gear. A cylindrical groove with a quarter-wave plate embedded in the inner wall of the central hole of the large gear is provided. The large gear is driven by the small gear to adjust the circularly polarized light emitted from the quarter-wave plate. The top surface of the lower photosensitive resin structure has a VCSEL laser and a photodetector arranged side-by-side. A polarizing beam splitter is disposed within the upper photosensitive resin structure. A collimating lens group composed of a concave lens and a convex lens is disposed within the light source channel of the middle photosensitive resin structure. The input side of the polarizing beam splitter is directly above the convex lens. The transmission side of the polarizing beam splitter is aligned with the quarter-wave plate. The reflection side of the polarizing beam splitter is connected to the photodetector through a photodetector channel.

[0011] The large gear is positioned on the top surface of the photosensitive resin upper structure shell by a large gear fixing structure.

[0012] The reflecting side of the polarizing beam splitter is attached to the right-angle side of the right-angle reflecting prism, and the emitting side of the right-angle reflecting prism is aligned with the photodetector.

[0013] Both the VCSEL laser and the photodetector are mounted on the PCB.

[0014] The lower and middle layers of the photosensitive resin structure are joined and fixed using mortise and tenon joints.

[0015] The dimensions of the lower layer of the photosensitive resin shell are 15.5mm × 9mm × 2mm; the dimensions of the middle layer of the photosensitive resin shell are 15.5mm × 12mm × 9mm; and the dimensions of the upper layer of the photosensitive resin shell are 15.5mm × 9mm × 6.4mm.

[0016] The technical effects of this invention are as follows: This invention provides a miniaturized pump optical module based on a VCSEL laser, used for optical pumping of an alkali metal gas cell for atomic inertial measurement, meeting sensitivity and performance testing requirements, and achieving miniaturization of the pump module. This has implications for the future integration of nuclear magnetic resonance gyroscopes. The structure, circuit, optical path, and software design of the miniaturized pump optical module system based on the VCSEL laser are achieved through optical simulation analysis, designing the layout of optical components and low-stress, low-stray-light installation. The VCSEL laser light source forms the pumped beam through a collimating lens, PBS, and a quarter-wave plate. Through structural and circuit design and software design, the optical module is miniaturized, and real-time power monitoring is achieved, with visualization on a host computer. This meets sensitivity and performance testing requirements and is particularly suitable for large scientific devices that require ultra-high sensitivity.

[0017] This invention has the following features: 1) It proposes a design scheme for a small pump light source module for atomic inertial measurement devices. 2) Compared with other schemes, the integrated design eliminates some optical components and further simplifies the circuitry, resulting in a small system structure that meets experimental requirements, providing a miniaturized pump light source module for nuclear magnetic resonance gyroscopes. 3) The module structure uses photosensitive resin material, which has high dimensional stability, is suitable for precision machining of miniaturized structures, has a temperature resistance far exceeding the temperature required for laser operation, is not easily deformed in the prototype working environment, thus not affecting the accuracy of the optical path, and has good toughness, making it less prone to breakage. In the optical path direction, a collimating lens is connected after the light source, and stable circularly polarized light is formed after passing through PBS and a waveplate, thereby forming stable circularly polarized light that is introduced into the alkali metal gas cell of the nuclear magnetic resonance gyroscope for optical pumping. 4) In real-time power detection, the control signal directly acts on the analog control interface of the laser to adjust the current and thus control the optical power, based on the responsivity R(λ) and dark current I. DARK Junction capacitance C j Based on parameters such as these, the S13956-1 photodetector was ultimately selected for implementation. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the optical path structure of a miniaturized pump optical module based on a VCSEL laser, which implements the present invention.

[0019] Figure 2 This is a schematic diagram of the assembly structure of a miniaturized pump optical module based on a VCSEL laser, which implements the present invention.

[0020] Figure 3 yes Figure 2 A three-dimensional structural diagram of its appearance.

[0021] The reference numerals in the attached figures are explained as follows: 1-VCSEL laser (VCSEL, Vertical-Cavity Surface-Emitting Laser); 2-VCSEL laser; 3-collimating lens group; 4-polarizing beam splitter (PBS); 5-photodetector (PD); 6-large gear fixing structure; 7-large gear; 8-small gear; 9-upper layer of photosensitive resin structure shell; 10-middle layer of photosensitive resin structure shell; 11-lower layer of photosensitive resin structure shell; 12-quarter-wave plate; 13-alkali metal gas cell; xyz-cartesian coordinate axes (i.e., x-axis, y-axis, and z-axis). The pump light travels along the x-axis in the coordinate system. Detailed Implementation

[0022] The following is in conjunction with the attached diagram ( Figures 1-3 The invention will be described in the following sections and examples.

[0023] Figure 1 This is a schematic diagram of the optical path structure of a miniaturized pump optical module based on a VCSEL laser, which implements the present invention. Figure 2 This is a schematic diagram of the assembly structure of a miniaturized pump optical module based on a VCSEL laser, which implements the present invention. Figure 3 yes Figure 2 A three-dimensional structural diagram of the exterior. (Reference) Figures 1 to 3 As shown, a miniaturized pump optical module based on a VCSEL laser includes a housing. The housing is composed of a lower photosensitive resin structure housing 11, a middle photosensitive resin structure housing 10, and an upper photosensitive resin structure housing 9, which are stacked layer by layer. The top surface of the upper photosensitive resin structure housing 9 is provided with a meshing large gear 7 and a small gear 8. The inner wall of the central hole of the large gear 7 is provided with a cylindrical groove into which a quarter-wave plate 12 is embedded. The large gear 7 is driven by the small gear 8 to adjust the circularly polarized light emitted from the quarter-wave plate 12. The top surface of the photosensitive resin lower structure shell 11 is provided with a VCSEL laser 1 and a photodetector 5 arranged side by side. The photosensitive resin upper structure shell 9 is provided with a polarizing beam splitter 4. The light source channel in the photosensitive resin middle structure shell 10 is provided with a collimating lens group 3 composed of concave and convex lenses. The input side of the polarizing beam splitter 4 is directly above the convex lens. The transmission side of the polarizing beam splitter 4 is aligned with the quarter-wave plate 12. The reflection side of the polarizing beam splitter 4 is connected to the photodetector 5 through a photodetector channel.

[0024] The large gear 7 is positioned on the top surface of the upper photosensitive resin shell 9 via the large gear fixing structure 6. The reflecting side of the polarizing beam splitter 4 is attached to the right-angle side of the right-angle reflecting prism, and the emitting side of the right-angle reflecting prism is aligned with the photodetector 5. Both the VCSEL laser 1 and the photodetector 5 are mounted on the PCB. The lower photosensitive resin shell 11 and the middle photosensitive resin shell 10, as well as the middle photosensitive resin shell 10 and the upper photosensitive resin shell 9, are all joined and fixed using mortise and tenon joints.

[0025] The dimensions of the lower photosensitive resin shell 11 are 15.5mm × 9mm × 2mm; the dimensions of the middle photosensitive resin shell 10 are 15.5mm × 12mm × 9mm; and the dimensions of the upper photosensitive resin shell 9 are 15.5mm × 9mm × 6.4mm.

[0026] This invention addresses a gap in existing technologies by designing a miniaturized pump optical module system based on a VCSEL laser for optical pumping of an alkali metal gas cell used in atomic inertial measurement. This system satisfies sensitivity and performance testing requirements and achieves miniaturization of the pump module, contributing to the future integration of nuclear magnetic resonance gyroscopes. The invention details the structure, circuitry, optical path, and software design of the miniaturized VCSEL pump optical module system. Through optical simulation analysis, the layout of optical components and low-stress, stray light-reducing installation are designed. The VCSEL laser source forms the pumped beam through a collimating lens, a PBS (Polymer Surface Photon), and a quarter-wave plate. The miniaturization of the optical module, real-time power monitoring, and visualization on a host computer are achieved through structural, circuit, and software design. This system satisfies sensitivity and performance testing requirements and is particularly suitable for large scientific facilities seeking ultra-high sensitivity.

[0027] like Figure 1 As shown, the optical path system in this embodiment mainly includes a laser source (i.e., VCSEL laser 1), a VCSEL laser 2, a collimating lens group 3, a polarizing beam splitter 4 (PBS), and a photodetector 5 (PD). In this embodiment, a VCSEL laser with a center wavelength of 980nm is selected. The collimating lens group 3 includes a lens and a convex lens to collimate the laser.

[0028] like Figure 1 , Figure 2 and Figure 3 As shown, an experimental design and study of a miniaturized pump optical module system based on a VCSEL laser is presented, including the following steps:

[0029] Step 1: Design the collimation system and optical path system from the VCSEL laser source 1. Simulate by adjusting the optical components to debug the pump light that meets the requirements. Then test the pump light in the prototype to solve the optical path performance, optical component layout and low stress to reduce stray light installation.

[0030] Step 2: The beam split by the PBS polarizing beam splitter 4 passes through the photodetector 5 to monitor the power of the light source in real time, and a circuit board PCB is designed for the implementation of the circuit part, connecting the module electrical signals to the outside for integration;

[0031] Step 3: Perform mechanical structure design and analysis on the miniaturized light source module, and design and process the miniaturized three-dimensional structure layout.

[0032] Step 4: Perform functional tests on the integrated light source module, and conduct sensitivity and performance tests on the nuclear magnetic resonance gyroscope prototype.

[0033] Using photosensitive resin to 3D print the mechanical structure results in high dimensional stability, making it suitable for precision machining of miniaturized structures. Its temperature resistance is far higher than the temperature required for laser operation, and it is not easily deformed in the prototype working environment, which would affect the accuracy of the optical path. It also has good toughness and is not easily broken.

[0034] The polarization control section mainly includes a polarizer and a waveplate. The polarizer is usually a PBS to obtain a high extinction ratio, and the reflected light is used for light intensity monitoring and control.

[0035] A collimating lens is connected to the light source, and after passing through a PBS and a waveplate, stable circularly polarized light is formed. This stable circularly polarized light is then fed into the alkali metal gas cell of the nuclear magnetic resonance gyroscope for optical pumping.

[0036] The resistance temperature detector (RTD) is a platinum resistance thermometer made of non-magnetic material.

[0037] A collimating lens group 3 is provided between the laser and the PBS. The collimating lens group 3 consists of a lens and a convex lens to collimate the pump laser.

[0038] In the upper structure, an additional large gear 7 and a meshing small gear 8 are added. Both gears are axially fixed to the module (the large gear is fixed axially with screws, and the small gear is fixed with an additional fixed shaft). The small gear is located on a fixed shaft outside the module for easy manual rotation. The large gear 7 has a hollowed-out center to provide an outlet for the pumping light emission module. Below it is a cylindrical groove 1mm high and 5mm in diameter for a quarter-wave plate to be embedded and fixed to the large gear. Adjusting the wave plate rotates the small gear, which in turn rotates the large gear via a gear transmission structure, causing the quarter-wave plate to rotate and thus producing the desired circularly polarized light. The upper structure dimensions are 15.5mm × 9mm × 6.4mm.

[0039] In the middle layer structure, a side-facing PBS beam splitter is mounted in the center, directly below the quarter-wave plate, and fixed with optical adhesive. This splits the pump light into two beams: one beam is emitted, and the other is reflected and directed to the photodetector on the bottom PCB. The middle layer structure measures 15.5mm × 12mm × 9mm.

[0040] In the lower layer structure, a recessed area at the bottom is used to place the PCB circuit board, which houses the light source and photodetector. Photodiodes are soldered above the circuit board to receive light signals. The final module design comprises three internal component sections and six structural parts, with different colors used to distinguish the internal components. Layers are joined and secured using mortise and tenon joints, allowing for easy horizontal pushing for assembly or disassembly. The lower layer structure measures 15.5mm × 9mm × 2mm.

[0041] The axial extension line of the aperture of the pump beam forms the envelope of the alkali metal gas chamber.

[0042] Let R a R is the radius of the pump beam aperture. b R is the radius of the front opening. c R is the radius of the pump light spot after collimation by the lens group. d The radius of the pump light spot before collimation by the lens group is given by the formula. when And R c ≥R b This allows for thermal equilibrium at both ends; then, according to the formula... The lens group can then be formed by selecting a concave lens with a focal length of f1 and a convex lens with a focal length of f2 based on the ratio. Finally, a host computer system is programmed to perform visual calculations on the optical module.

[0043] Contents not described in detail in this specification are prior art known to those skilled in the art. It is hereby indicated that the above description is intended to help those skilled in the art understand this invention, but does not limit the scope of protection of this invention. Any equivalent substitutions, modifications, improvements, and / or simplifications of the above descriptions that do not depart from the essential content of this invention fall within the scope of protection of this invention.

Claims

1. A miniaturized pump optical module based on a VCSEL laser, characterized in that, The device includes an outer shell, which is composed of a lower photosensitive resin structure, a middle photosensitive resin structure, and an upper photosensitive resin structure, stacked layer by layer. The top surface of the upper photosensitive resin structure has a meshing large gear and a small gear. The inner wall of the central hole of the large gear has a cylindrical groove into which a quarter-wave plate is embedded. The large gear is driven by the small gear to adjust the circularly polarized light emitted from the quarter-wave plate. The top surface of the lower photosensitive resin structure has a VCSEL laser and a photodetector arranged side-by-side. A polarizing beam splitter is disposed within the upper photosensitive resin structure. A collimating lens group, composed of a concave lens and a convex lens, is disposed within the light source channel of the middle photosensitive resin structure. The input side of the polarizing beam splitter is directly above the convex lens. The transmission side of the polarizing beam splitter is aligned with the quarter-wave plate. The reflection side of the polarizing beam splitter is connected to the photodetector through a photodetector channel.

2. The miniaturized pump optical module based on a VCSEL laser according to claim 1, characterized in that, The large gear is positioned on the top surface of the photosensitive resin upper structure shell by a large gear fixing structure.

3. The miniaturized pump optical module based on a VCSEL laser according to claim 1, characterized in that, The reflecting side of the polarizing beam splitter is attached to the right-angle side of the right-angle reflecting prism, and the emitting side of the right-angle reflecting prism is aligned with the photodetector.

4. The miniaturized pump optical module based on a VCSEL laser according to claim 1, characterized in that, Both the VCSEL laser and the photodetector are mounted on the PCB.

5. The miniaturized pump optical module based on a VCSEL laser according to claim 1, characterized in that, The lower and middle layers of the photosensitive resin structure are joined and fixed using mortise and tenon joints.

6. The miniaturized pump optical module based on a VCSEL laser according to claim 1, characterized in that, The dimensions of the lower layer of the photosensitive resin shell are 15.5mm × 9mm × 2mm; the dimensions of the middle layer of the photosensitive resin shell are 15.5mm × 12mm × 9mm; and the dimensions of the upper layer of the photosensitive resin shell are 15.5mm × 9mm × 6.4mm.

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