Optical frequency doubling device applied to laser internal engraving

Abstract

The invention relates to the technical field of laser processing, and discloses an optical frequency doubling device applied to laser internal engraving, which comprises a shell used for separating the internal temperature from the external temperature and reducing the influence of the outside on the inside; the clamps are mounted in the shell, are symmetrically distributed up and down, wrap the crystals, and are used for fixing the positions between the crystals and conducting heat; the crystal is arranged between the clamps and is used for converting the fundamental frequency laser into multiplied frequency laser; and the temperature control mechanism is mounted on one side, far away from the crystal, of the clamp, has heating and cooling functions and is used for increasing or reducing the temperature of the crystal. A plurality of nonlinear crystals with different geometric cutting angles are placed in the same clamp, and the temperature control module controls the overall temperature of the clamp to be the midpoint of the phase matching temperature of each crystal. When the temperature drifts, decline of frequency doubling efficiency of part of the crystals can be compensated by efficiency rise of other crystals, so that stability of output power of frequency doubling light is effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of laser processing, in particular to an optical frequency doubling device used for laser inner engraving. Background Art

[0002] Laser engraving technology is a high-precision processing method widely used in industrial manufacturing and artistic creation. This technology uses a laser beam to engrave inside the material to achieve delicate patterns and complex structures. Due to the high energy density and good focusing characteristics of lasers, laser engraving can be efficiently and accurately processed on a variety of materials (such as glass, wood, metal, etc.). However, in order to achieve higher processing quality and efficiency, it is usually necessary to adjust the wavelength of the laser to a range that is more suitable for absorption by specific materials. The main function of the optical frequency doubling device is to convert the wavelength of the base frequency laser into a shorter frequency doubling laser wavelength. Taking the 1064nm base frequency laser as an example, the optical frequency doubling device can effectively generate 532nm lasers. This wavelength of laser is more easily absorbed by many materials, thereby achieving higher processing efficiency and more delicate engraving effects. In addition, the application of frequency doubling lasers in the visible light range also facilitates operators to align and adjust.

[0003] However, existing frequency doubling devices usually use a single nonlinear crystal for frequency conversion, which has key problems such as insufficient temperature control accuracy, phase matching problems, output power fluctuations, high structural complexity, and insufficient flexibility. Specifically, temperature fluctuations will cause the performance of the crystal to decline, thereby affecting the frequency doubling efficiency; the geometric cutting angles of different crystals will lead to different phase matching temperatures, making it difficult to meet the matching requirements of multiple crystals at the same time; the efficiency decline of a single crystal will directly cause fluctuations in the overall laser output power, affecting the processing quality. In addition, existing devices are often complex in design and need to rely on high-precision monitoring and control systems, which increases the overall cost and difficulty of maintenance. At the same time, they lack adaptability to different laser wavelengths or materials, limiting their use in a variety of applications. Therefore, there is an urgent need for a new type of frequency doubling device to solve the above problems and improve the performance and stability of laser engraving. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides an optical frequency doubling device applied to laser inner engraving, which solves the problem of unstable frequency doubling efficiency caused by temperature fluctuation in laser inner engraving.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: an optical frequency doubling device applied to laser engraving, comprising:

[0006] The outer shell is used to separate the internal temperature from the external temperature and reduce the influence of the external environment on the internal part;

[0007] A clamp is installed inside the housing and is symmetrically distributed up and down and wraps around the crystals, and is used to fix the positions between the crystals and conduct heat;

[0008] A crystal, which is disposed between the fixtures and is used to convert fundamental frequency laser light into frequency-doubled laser light;

[0009] The temperature control mechanism is installed on the side of the fixture away from the crystal and has both heating and cooling functions, which is used to increase or decrease the temperature of the crystal;

[0010] The temperature control module is arranged outside the shell and is electrically connected to the temperature control mechanism to control the operating state of the temperature control mechanism.

[0011] Preferably, the crystal includes but is not limited to a fixed pitch arrangement and bonded contact connections.

[0012] Preferably, the crystals are distributed at a fixed interval in a range of 0.5 mm to 1 mm.

[0013] Preferably, when the crystals are arranged at a fixed interval, both light-transmitting surfaces thereof are polished and coated to provide irradiation channels for fundamental frequency laser and frequency-doubled laser.

[0014] Preferably, when the crystals are connected by bonding, the incident surface of the first crystal and the exit surface of the last crystal are polished and coated to provide fundamental frequency laser and frequency-doubled laser irradiation channels.

[0015] A control method for an optical frequency doubling device applied to laser engraving comprises the following steps:

[0016] S1. Configure the crystal array: Use multiple nonlinear crystals, set the total number of crystals N, and cut the crystals according to the geometric cutting angle (θ i ,φ i ) to optimize cutting;

[0017] S2. Set the ideal phase matching temperature: Calculate the ideal phase matching temperature T for each crystal i,opt ;

[0018] S3. Setting the target temperature of the entire fixture through the temperature control module: Calculate and set the target temperature of the entire fixture as a weighted average of the ideal phase matching temperatures of all crystals.

[0019] Preferably, in the step S2, the definition formula of the crystal position and the phase matching temperature is:

[0020] When N is an odd number:

[0021]

[0022] When N is an even number:

[0023]

[0024] Among them, T i,opt is the ideal phase matching temperature, N is the total number of crystals, and i is the crystal serial number.

[0025] Preferably, in step S3, the target temperature calculation formula of the temperature control module is:

[0026]

[0027] Among them, T control is the target temperature of the temperature control module, T i,opt is the ideal phase matching temperature, N is the total number of crystals, and i is the crystal serial number.

[0028] Working principle: Before the device is put into operation, it is necessary to calculate the average temperature between the crystals. After the calculation, the temperature in the fixture is adjusted to the average value through the temperature control module. After the adjustment is completed, the corresponding base frequency laser begins to transmit from the first crystal, and finally transmits from the last crystal. When the base frequency laser is transmitted, if the corresponding temperature shifts, some performance changes, resulting in an increase and decrease reaction, thereby offsetting the deviation that should be caused by the temperature drift.

[0029] The present invention provides an optical frequency doubling device for laser engraving, which has the following beneficial effects:

[0030] 1. The present invention forms a frequency doubling device by placing multiple nonlinear crystals in the same fixture. Different crystals have different geometric cutting angles and correspond to different phase matching temperatures. The overall temperature control temperature of the temperature control module is the midpoint of the phase matching temperature of each crystal. When the crystal temperature drifts, some crystals deviate from the phase matching temperature, resulting in a decrease in the frequency doubling efficiency. However, there are always some crystals close to the phase matching temperature, resulting in an increase in the frequency doubling efficiency, so that the decrease is compensated. Therefore, the stability of the frequency doubling light output power can be effectively improved as a whole. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a cross-sectional view of the present invention;

[0032] Figure 2 It is a flow chart of the steps of the present invention.

[0033] Among them, 1. shell; 2. fixture; 3. crystal; 4. temperature control mechanism; 5. temperature control module. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Embodiment 1:

[0036] Please see attached Figure 1 The embodiment of the present invention provides an optical frequency doubling device for laser engraving, comprising:

[0037] The housing 1 is used to separate the internal temperature from the external temperature and reduce the influence of the external environment on the internal temperature;

[0038] The fixture 2 is installed inside the housing 1 and is symmetrically distributed up and down and wraps around the crystal 3, and is used to fix the position between the crystals 3 and conduct heat;

[0039] A crystal 3, which is arranged between the clamps 2 and is used to convert the fundamental frequency laser into a frequency-doubled laser;

[0040] A temperature control mechanism 4 is installed on the side of the fixture 2 away from the crystal 3 and has both heating and cooling functions, and is used to increase or decrease the temperature of the crystal 3;

[0041] A temperature control module 5, which is arranged outside the housing 1 and is electrically connected to the temperature control mechanism 4, and is used to control the operating state of the temperature control mechanism 4;

[0042] Crystal 3 includes but is not limited to fixed pitch arrangement and bonded contact connection;

[0043] The crystals 3 are distributed at fixed intervals in the range of 0.5 mm to 1 mm;

[0044] When the crystals 3 are arranged at a fixed interval, their two light-transmitting surfaces are polished and coated to provide irradiation channels for the fundamental frequency laser and the frequency-doubled laser;

[0045] When the crystals 3 are connected by bonding, the incident surface of the first crystal 3 and the exit surface of the last crystal 3 are polished and coated to provide irradiation channels for the fundamental frequency laser and the frequency-doubled laser.

[0046] Specifically, before the device is put into operation, it is necessary to first calculate the average value of the adaptation temperature between the crystals 3. The setting of this temperature is the key to ensure the efficient operation of the entire optical frequency doubling device. Through the temperature control module 5, the temperature control mechanism 4 can be accurately controlled to adjust the temperature in the fixture 2 to the preset adaptation value. The goal of this process is to achieve temperature balance between the crystals 3 and provide an ideal working environment for the subsequent laser frequency doubling process;

[0047] After the adjustment is completed, the fundamental frequency laser will be transmitted from the first crystal 3, and after conversion of each crystal, it will finally be emitted from the last crystal 3. At this time, the wavelength of the laser will be effectively converted from 1064nm to 532nm. It is worth noting that during the fundamental frequency laser transmission process, if the temperature shifts, the performance of some crystals 3 may change. This change is manifested as the efficiency of some crystals increasing, while the efficiency of other crystals decreasing, that is, the impact of the decrease in the frequency doubling efficiency of some crystals will be compensated by the increase in the frequency doubling efficiency of some crystals;

[0048] This design has an important effect, that is, it effectively reduces the power fluctuation as a whole, thereby improving the stability of the doubled frequency optical power. This not only improves the accuracy of laser processing, but also enhances the system's adaptability in changing environments. Ultimately, this method will significantly improve the overall processing quality of laser engraving and ensure the consistency and reliability of the product.

[0049] Embodiment 2:

[0050] Please see attached Figure 2 , a control method for an optical frequency doubling device applied to laser engraving, comprising the following steps:

[0051] S1. Configure a crystal array: Use multiple nonlinear crystals 3, set the total number of crystals 3 N, and cut the crystals 3 according to the geometric cutting angle (θ i ,φ i ) to optimize cutting;

[0052] S2. Set the ideal phase matching temperature: Calculate the ideal phase matching temperature T for each crystal 3 i,opt ;

[0053] S3, setting the target temperature of the entire fixture through the temperature control module: calculating and setting the target temperature of the entire fixture 2 as the weighted average of the ideal phase matching temperatures of all crystals 3;

[0054] In step S2, the definition formula of the crystal 3 position and phase matching temperature is:

[0055] When N is an odd number:

[0056]

[0057] When N is an even number:

[0058]

[0059] Among them, T i,opt is the ideal phase matching temperature, N is the total number of crystals 3, and i is the serial number of crystal 3;

[0060] In step S3, the target temperature calculation formula of the temperature control module 5 is:

[0061]

[0062] Among them, T control is the target temperature of the temperature control module 5, T i,opt is the ideal phase matching temperature, N is the total number of crystals 3, and i is the serial number of crystal 3.

[0063] Specifically, step S1 constructs an optical frequency doubling device by using multiple nonlinear crystals 3; optimizes the cutting according to the geometric cutting angle of each crystal to ensure that it can achieve the best phase matching; the optimization of the geometric cutting angle is based on the laser wavelength and the optical properties of the material to ensure the maximum conversion efficiency in practical applications; this reasonable crystal configuration not only helps to improve the laser output power, but also improves the processing accuracy;

[0064] In step S2, the ideal phase matching temperature is calculated for each crystal 3. The setting of this temperature is based on the theory of nonlinear optics and is achieved by considering the geometric cutting angle of the crystal and its corresponding wavelength. The ideal phase matching temperature ensures that the light wave maintains the same phase velocity in the crystal at this temperature, thereby maximizing the conversion efficiency. By accurately setting the phase matching temperature of each crystal, the conversion efficiency and overall output quality of the laser can be significantly improved.

[0065] S3, setting the target temperature of the temperature control module: This step calculates and sets the target temperature of the temperature control module 5, which is the weighted average of the ideal phase matching temperatures of all crystals 3; through this weighted average method, the temperature requirements of each crystal can be effectively integrated, thereby reducing the impact of temperature fluctuations on the overall system; precise control of the temperature control module helps to maintain overall output stability under dynamic operating conditions and ensure quality consistency during laser processing;

[0066] In this way, a high-efficiency and stable laser frequency doubling system is formed by using a reasonable crystal 3 configuration, precise phase matching temperature setting and an effective temperature control mechanism through a control method; through the implementation of the above steps, the output power of the frequency doubling laser can be effectively improved, and the power drift caused by temperature changes can be reduced, thereby improving the processing quality of laser inner engraving; this method not only reduces the dependence on high-precision temperature control modules, making the device design simpler and more compact, but also makes it more flexible and economical in practical applications.

[0067] Embodiment three:

[0068] The frequency doubling device of the present invention uses LBO crystal to convert the fundamental frequency 1064nm laser into the frequency doubling 532nm laser. The device uses 5 LBO crystals, and the specific parameters are as follows:

[0069] Crystal configuration:

[0070] The size of each crystal is 3×3×5 mm, of which 5 mm is the length in the light transmission direction.

[0071] The light-transmitting end faces of the crystal are polished and coated, and the coating layer is suitable for 1064nm and 532nm anti-reflection coatings.

[0072] Crystal spacing:

[0073] The spacing between each crystal is set to 0.5 mm to ensure efficient beam transmission.

[0074] Geometric cutting angle and phase matching temperature:

[0075] The first LBO crystal:

[0076] Geometric cutting angle (θ0=90°, φ0=0.8°)

[0077] Phase matching temperature T 1,opt =421.6K

[0078] The second LBO crystal:

[0079] Geometric cutting angle (θ0=90°, φ0=0.7°)

[0080] Phase matching temperature T 2,opt =421.7K

[0081] The third LBO crystal:

[0082] Geometric cutting angle (θ0=90°, φ0=0.6°)

[0083] Phase matching temperature T 3,opt =421.8K

[0084] The fourth LBO crystal:

[0085] Geometric cutting angle (θ0=90°, φ0=0.5°)

[0086] Phase matching temperature T 4,opt =421.9K

[0087] The fifth LBO crystal:

[0088] Geometric cutting angle (θ0=90°, φ0=0.4°)

[0089] Phase matching temperature T 5,opt =422.0K.

[0090] Specifically, this embodiment describes in detail how to use LBO crystals to efficiently achieve frequency multiplication of lasers, focusing on the configuration, spacing, cutting angle and phase matching temperature of the crystals. This design ensures the stability and efficiency of laser output and provides a reliable technical solution for practical applications in the field of laser engraving. Through reasonable crystal layout and temperature control design, the invented frequency multiplication device exhibits good performance and economy in operation, and is suitable for wide application in industry and scientific research.

[0091] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An optical frequency doubling device for laser engraving, characterized in that: include: An outer shell (1) is used to separate the internal temperature from the external temperature and reduce the influence of the external environment on the internal part; A clamp (2) is installed inside the housing (1) and is symmetrically distributed up and down and wraps around the crystal (3), and is used to fix the position between the crystals (3) and conduct heat; A crystal (3) disposed between the fixtures (2) and used for converting fundamental frequency laser light into frequency-doubled laser light; A temperature control mechanism (4), which is installed on a side of the fixture (2) away from the crystal (3) and has both heating and cooling functions, and is used to increase or decrease the temperature of the crystal (3); The temperature control module (5) is arranged outside the housing (1) and is electrically connected to the temperature control mechanism (4) and is used to control the operating state of the temperature control mechanism (4).

2. The optical frequency doubling device for laser engraving according to claim 1, characterized in that: The crystal (3) includes but is not limited to fixed pitch arrangement and bonded contact connection.

3. The optical frequency doubling device for laser engraving according to claim 1, characterized in that: The crystals (3) are distributed at a fixed interval in a range of 0.5 mm to 1 mm.

4. The optical frequency doubling device for laser engraving according to claim 1, characterized in that: When the crystals (3) are arranged at a fixed interval, their two light-transmitting surfaces are polished and coated to provide irradiation channels for fundamental frequency laser and frequency-doubled laser.

5. The optical frequency doubling device for laser engraving according to claim 1, characterized in that: When the crystals (3) are connected by bonding contact, the incident surface of the first crystal (3) and the exit surface of the last crystal (3) are polished and coated to provide fundamental frequency laser and frequency-doubled laser irradiation channels.

6. A control method for an optical frequency doubling device for laser engraving, according to the optical frequency doubling device for laser engraving according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Configuring a crystal array: using a plurality of nonlinear crystals (3), setting the total number N of crystals (3), and determining the geometric cutting angle (θ) of each crystal (3). i ,φ i ) to optimize cutting; S2. Set the ideal phase matching temperature: Calculate the ideal phase matching temperature T for each crystal (3) i,opt ; S3. Setting the target temperature of the entire fixture through the temperature control module: Calculate and set the target temperature of the entire fixture (2) as the weighted average of the ideal phase matching temperatures of all crystals (3).

7. The control method of the optical frequency doubling device for laser engraving according to claim 6, characterized in that: In step S2, the definition formula of the crystal (3) position and the phase matching temperature is: When N is an odd number: When N is an even number: Among them, T i,opt is the ideal phase matching temperature, N is the total number of crystals (3), and i is the serial number of crystal (3).

8. The control method of the optical frequency doubling device for laser engraving according to claim 6, characterized in that: In step S3, the target temperature calculation formula of the temperature control module (5) is: Among them, T control is the target temperature of the temperature control module (5), T i,opt is the ideal phase matching temperature, N is the total number of crystals (3), and i is the serial number of crystal (3).

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