Output wavelength closed-loop adjusting method and system based on negative feedback adjusting device

Abstract

The application discloses an output wavelength closed-loop adjusting method and system based on a negative feedback adjusting device, and relates to the field of external cavity quantum cascade lasers; wherein, during the operation of the external cavity broadband tunable laser, the output wavelength closed-loop adjusting method calculates a real-time light spot position through the negative feedback adjusting device, matches the real-time light spot position with the light spot position in a calibration data table, obtains a corresponding laser wavelength, compares the laser wavelength with a target laser wavelength, determines a voltage adjustment value, controls the working voltage of the current galvanometer driver to increase or decrease according to the voltage adjustment value, and repeats the process until the laser wavelength output by the resonant cavity is stabilized at the target laser wavelength or within an allowable error range thereof; the galvanometer rotation angle is accurately controlled, and the repeatability and accuracy of the output wavelength are improved.

Description

Technical Field

[0001] This invention relates to the field of external cavity broadband tuned lasers, and more particularly to a method and system for closed-loop adjustment of output wavelength based on a negative feedback adjustment device. Background Technology

[0002] External cavity broadband tunable lasers operate on the external cavity principle, characterized by placing the laser gain device within an angle-tunable external cavity. Precise tuning of the output wavelength is achieved by adjusting the rotation angle of a galvanometer within the cavity. However, in practical applications, the galvanometer rotation angle is typically controlled by the voltage output from the driver. The accuracy of the output voltage, along with factors such as mechanical friction and aging, makes precise control of the galvanometer rotation angle difficult. This, in turn, affects the repeatability and accuracy of the external cavity laser's output wavelength. Repeatability refers to the consistency of measurement results under identical conditions. Summary of the Invention

[0003] In order to precisely control the rotation angle of the galvanometer and improve the repeatability and accuracy of the output wavelength of the external cavity laser, this invention proposes a closed-loop adjustment method for the output wavelength based on a negative feedback adjustment device, which is applied to an external cavity broadband tuned laser.

[0004] The external cavity broadband tunable laser includes: a galvanometer, a galvanometer driver for controlling the angle of the galvanometer, and a resonant cavity; the laser wavelength output by the resonant cavity varies based on the change in the angle of the galvanometer.

[0005] The negative feedback adjustment device includes: a visible light laser and a one-dimensional position detector; the visible light laser is used to emit a laser beam, which is reflected to the one-dimensional position detector through a galvanometer in an external cavity broadband tuned laser; the output wavelength closed-loop adjustment method includes:

[0006] By adjusting the operating voltage of the galvanometer driver, the angle of the galvanometer is changed, thereby altering the position of the laser spot formed after reflection by the laser beam emitted by the visible light laser. This causes the laser spot to sequentially pass through multiple preset position points on the photosensitive area of ​​the one-dimensional position detector. When the laser spot passes through each preset position point, the position of that point, the corresponding operating voltage of the galvanometer driver, and the laser wavelength output by the resonant cavity at that time are recorded to form the calibration data corresponding to that position point, and a calibration data table is established.

[0007] Set the target laser wavelength to be output from the resonant cavity, find the matching laser wavelength in the calibration data table, and obtain the corresponding galvanometer driver operating voltage through the matched laser wavelength;

[0008] Start the external cavity broadband tuned laser and start the galvanometer driver with the matched galvanometer driver working voltage to make the galvanometer rotate, while controlling the negative feedback adjustment device to enter the working state.

[0009] During the operation of the external cavity broadband tuned laser, the real-time spot position is calculated by the negative feedback adjustment device, and the corresponding laser wavelength is obtained by matching the spot position in the calibration data table with the real-time spot position. By comparing the laser wavelength with the target laser wavelength, the voltage adjustment value is determined, and the voltage adjustment value is used to control the current galvanometer driver operating voltage to increase or decrease. This process is repeated to make the laser wavelength output by the resonant cavity reach the target laser wavelength. After reaching the target laser wavelength, the adjustment is continuously made to keep the wavelength stable within the target laser wavelength or its allowable error range.

[0010] Furthermore, the negative feedback adjustment device also includes: a controller;

[0011] The one-dimensional position detector is used to generate a photocurrent at the spot illumination point when the laser spot hits its photosensitive area, and the current signal is collected by the electrodes at both ends of the one-dimensional position detector.

[0012] The controller calculates the position of the light spot based on the collected current signal; the position of the light spot is the vertical distance between the light spot and the center line of the photosensitive area.

[0013] Furthermore, the external cavity broadband tuned laser also includes:

[0014] A blazed grating is used for wavelength selection, reflecting light of a specific wavelength back to the resonant cavity through diffraction.

[0015] The resonant cavity is composed of a first collimating lens, a laser gain chip, and a second collimating lens. Photons emitted by the laser gain chip pass through the first collimating lens. The photons passing through the first collimating lens are reflected by a galvanometer to a blazed grating. The blazed grating diffracts according to the wavelength of the incident light. The diffracted photons are reflected by the galvanometer and then reflected back into the laser gain chip by the first collimating lens. When the wavelength is selected by the blazed grating, the light of a specific wavelength is amplified in the resonant cavity. When its intensity exceeds the lasing threshold of that wavelength, the laser of the specific wavelength selected by the galvanometer and the blazed grating is output through the second collimating lens.

[0016] Furthermore, the laser beam path emitted by the visible light laser does not interfere with the laser beam path emitted by the laser gain chip, so as to ensure that the beam of one is not blocked by the optical element of the other.

[0017] Furthermore, the matching laser wavelength is found in the calibration data table, and the corresponding galvanometer driver operating voltage is obtained using the matched laser wavelength. Specifically:

[0018] Search for the matching laser wavelength in the calibration data table; if there is a matching laser wavelength, obtain the corresponding working voltage of the galvanometer driver; if there is no matching laser wavelength, interpolate the calibration data table by the interpolation method to obtain the calibration data matching the target laser wavelength;

[0019] Match the real-time spot position with the spot positions in the calibration data table to obtain the corresponding laser wavelength, specifically: match the real-time spot position with the spot positions in the calibration data table. If there is a matching spot position, obtain the laser wavelength corresponding to the spot position. If there is no matching spot position, interpolate the calibration data table by the interpolation method to obtain the calibration data matching the real-time spot position, and obtain the laser wavelength in the calibration data.

[0020] Further, the interpolation of the calibration data table by the interpolation method to obtain the calibration data matching the target laser wavelength is specifically:

[0021] Search for the two laser wavelengths closest to the target laser wavelength and their corresponding calibration data in the calibration data table;

[0022] Calculate the calibration data matching the target laser wavelength through the closest calibration data; the calculation formula includes:

[0023]

[0024] In the formula, V1 and V2 represent the working voltages of the galvanometer drivers in the closest calibration data; λ1 and λ2 represent the laser wavelengths corresponding to V1 and V2 in the closest calibration data; x1 and x2 represent the spot positions corresponding to V1 and V2 in the closest calibration data; λ represents the target laser wavelength; where: V1 < V < V2; V and x represent the working voltage of the galvanometer driver and the spot position matching the target laser wavelength respectively.

[0025] Further, the controller calculates the spot position according to the collected current signal, and the calculation formula is:

[0026]

[0027] where, Δ = I ,

[0029] -I R ; Σ = I L +I R ;

[0028] In the formula, I0 is the magnitude of the photo-generated current generated at the spot illumination when the laser spot hits its photosensitive area;

[0029] I L and I Rrepresents the photocurrent received by the first and second electrodes of the one-dimensional position detector, respectively; L represents the length of the photosensitive area of ​​the one-dimensional position detector; x represents the calculated position of the light spot.

[0030] This invention also proposes an output wavelength closed-loop adjustment system based on a negative feedback adjustment device, which is applied to an external cavity broadband tuned laser.

[0031] The external cavity broadband tunable laser includes: a galvanometer, a galvanometer driver for controlling the angle of the galvanometer, and a resonant cavity; the laser wavelength output by the resonant cavity varies based on the change in the angle of the galvanometer.

[0032] The negative feedback adjustment device includes: a visible light laser and a one-dimensional position detector; the visible light laser is used to emit a laser beam, which is reflected to the one-dimensional position detector by a galvanometer in an external cavity broadband tuned laser; the output wavelength closed-loop adjustment system includes:

[0033] The calibration module is used to change the galvanometer angle by adjusting the operating voltage of the galvanometer driver, thereby changing the position of the laser spot formed after reflection of the laser beam emitted by the visible light laser. The laser spot passes through multiple preset position points on the photosensitive area of ​​the one-dimensional position detector in sequence. When the laser spot passes through each preset position point, the position of the position point, the corresponding operating voltage of the galvanometer driver, and the laser wavelength output by the resonant cavity at this time are recorded to form the calibration data corresponding to the position point and establish a calibration data table.

[0034] The matching module is used to set the target laser wavelength to be output by the resonant cavity, find the matching laser wavelength in the calibration data table, and obtain the corresponding galvanometer driver operating voltage through the matched laser wavelength.

[0035] The startup module is used to start the external cavity broadband tuned laser and start the galvanometer driver with the matched galvanometer driver working voltage to make the galvanometer rotate, while controlling the negative feedback adjustment device to enter the working state.

[0036] The closed-loop adjustment module is used to calculate the real-time spot position through a negative feedback adjustment device during the operation of the external cavity broadband tuned laser. By matching the spot position in the calibration data table with the real-time spot position, the corresponding laser wavelength is obtained. By comparing the laser wavelength with the target laser wavelength, the voltage adjustment value is determined, and the voltage adjustment value is used to control the current galvanometer driver operating voltage to increase or decrease. This process is repeated to make the laser wavelength output by the resonant cavity reach the target laser wavelength. After reaching the target laser wavelength, the module is continuously adjusted to keep the wavelength stable within the target laser wavelength or its allowable error range.

[0037] Furthermore, the negative feedback adjustment device also includes: a controller;

[0038] The one-dimensional position detector is used to generate a photocurrent at the spot illumination point when the laser spot hits its photosensitive area, and the current signal is collected by the electrodes at both ends of the one-dimensional position detector.

[0039] The controller calculates the position of the light spot based on the collected current signal; the position of the light spot is the vertical distance between the light spot and the center line of the photosensitive area.

[0040] Furthermore, the external cavity broadband tuned laser also includes:

[0041] A blazed grating is used for wavelength selection, reflecting light of a specific wavelength back to the resonant cavity through diffraction.

[0042] The resonant cavity is composed of a first collimating lens, a laser gain chip, and a second collimating lens. Photons emitted by the laser gain chip pass through the first collimating lens. The photons passing through the first collimating lens are reflected by a galvanometer to a blazed grating. The blazed grating diffracts according to the wavelength of the incident light. The diffracted photons are reflected by the galvanometer and then reflected back into the laser gain chip by the first collimating lens. When the wavelength is selected by the blazed grating, the light of a specific wavelength is amplified in the resonant cavity. When its intensity exceeds the lasing threshold of that wavelength, the laser of the specific wavelength selected by the galvanometer and the blazed grating is output through the second collimating lens.

[0043] Compared with the prior art, the present invention has at least the following beneficial effects:

[0044] (1) This invention adjusts the operating voltage of the galvanometer driver so that the laser beam emitted by the visible light laser passes sequentially through multiple preset position points on the photosensitive area of ​​the one-dimensional position detector. When the laser beam passes through each preset position point, the position of the position point, the corresponding operating voltage of the galvanometer driver, and the laser wavelength output by the resonant cavity at this time are recorded to form calibration data corresponding to the position point and establish a calibration data table. During the operation of the external cavity broadband tuned laser, the real-time position of the laser beam is calculated by the negative feedback adjustment device, and the laser wavelength is obtained by matching the real-time position of the laser beam with the position of the laser beam in the calibration data table. By comparing the laser wavelength with the target laser wavelength, the voltage adjustment value is determined, and the voltage adjustment value is used to control the current galvanometer driver operating voltage to increase or decrease. This process is repeated until the laser wavelength output by the resonant cavity is stable within the target laser wavelength or its allowable error range. This achieves precise control of the galvanometer rotation angle and improves the repeatability and accuracy of the output wavelength.

[0045] (2) By using a negative feedback adjustment device, the present invention can monitor and adjust the laser wavelength in real time, which significantly improves the accuracy of wavelength adjustment; the calibration data table ensures the correspondence between the working voltage of the galvanometer driver and the actual laser wavelength, thereby realizing precise control of the output wavelength.

[0046] (3) Through the closed-loop adjustment mechanism, the present invention can continuously monitor the real-time spot position and dynamically adjust the working voltage of the galvanometer driver according to the actual measurement results, so as to ensure that the output wavelength is always stable near the target laser wavelength and improve the overall stability of the system.

[0047] (4) The present invention simplifies the operation process through an automated adjustment mechanism, reduces the need for manual intervention, and lowers the difficulty of operation and error rate. Users only need to set the target laser wavelength, and the system can automatically complete the adjustment process.

[0048] (5) The present invention can detect and correct wavelength deviation in a timely manner through the closed-loop adjustment module, which improves the reliability and robustness of the system. Even in the presence of factors such as the accuracy of the output voltage of the galvanometer driver and mechanical friction, the accuracy of the output wavelength can be maintained. Attached Figure Description

[0049] Figure 1 This is a structural diagram of an external cavity broadband tuned laser and a negative feedback adjustment device.

[0050] Figure 2 This is a structural diagram of an output wavelength closed-loop adjustment system based on a negative feedback adjustment device;

[0051] Figure 3 This is a schematic diagram of the principle structure of a one-dimensional position detector;

[0052] Figure 4 This is a schematic diagram showing the relationship between the rotation angle of the galvanometer and the position of the laser spot.

[0053] In the picture:

[0054] 1. Blazed grating; 2. Galvanometer; 3. Galvanometer driver; 4. First collimating lens; 5. Infrared laser chip; 6. Second collimating lens; 7. Visible laser; 8. One-dimensional position detector; 9. Controller. Detailed Implementation

[0055] 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.

[0056] Example 1

[0057] The output wavelength of an external cavity laser is positively correlated with the rotation angle of the galvanometer. This rotation angle is controlled by a galvanometer driver; applying different voltages changes the rotation angle. However, due to factors such as the accuracy of the galvanometer driver voltage, the rotation angle is often not consistent at the same voltage point. This deficiency results in an output wavelength error of ±3 nm, which is unacceptable in some high-precision spectrometers. To address the problem of low repeatability of the galvanometer rotation angle, this invention proposes a closed-loop output wavelength adjustment method based on a negative feedback adjustment device, applied to external cavity broadband tunable lasers.

[0058] like Figure 1 As shown, the external cavity broadband tuned laser includes: a galvanometer 2, a galvanometer driver 3 for controlling the angle of the galvanometer, and a resonant cavity; the laser wavelength output by the resonant cavity varies based on the change of the galvanometer angle (rotation angle);

[0059] The external cavity broadband tuned laser also includes:

[0060] Blazed grating 1 is used for wavelength selection, reflecting light of a specific wavelength back to the resonant cavity through diffraction;

[0061] The resonant cavity is composed of a first collimating lens 4, a laser gain chip 5, and a second collimating lens 6. Photons emitted from the laser gain chip 5 pass through the first collimating lens 4. The photons passing through the first collimating lens 4 are reflected by the galvanometer 2 to the blazed grating 1. The blazed grating 1 diffracts according to the wavelength of the incident light. The diffracted photons are reflected by the galvanometer 2 and then reflected back into the laser gain chip 5 through the first collimating lens 4. After wavelength selection by the blazed grating 1, light of a specific wavelength is amplified in the resonant cavity. When its intensity exceeds the lasing threshold of that wavelength, the laser of the specific wavelength selected by the galvanometer 2 and the blazed grating 1 is output through the second collimating lens 6. The second collimating lens 6, in addition to reflecting part of the light back into the resonant cavity, also serves as the emitting end of the entire external cavity broadband tuned laser, emitting laser light with power exceeding the lasing threshold.

[0062] The negative feedback adjustment device includes: a visible light laser 7 and a one-dimensional position detector 8; the visible light laser 7 is used to emit a laser beam, which is reflected to the one-dimensional position detector 8 through the galvanometer 2 in the external cavity broadband tuned laser; the negative feedback adjustment device also includes: a controller 9.

[0063] In this embodiment, the one-dimensional position detector 8 is a one-dimensional linear PSD with a photosensitive surface size of 1mm*12mm and a position resolution of 0.3um.

[0064] The one-dimensional position detector 8 is used to generate a photocurrent at the spot illumination point when the laser spot hits its photosensitive area, and the current signal is collected by the electrodes at both ends of the one-dimensional position detector 8.

[0065] The controller 9 calculates the position of the light spot based on the collected current signal; the position of the light spot is the vertical distance between the center point of the light spot and the center line of the photosensitive area.

[0066] It should be noted that a one-dimensional position detector (PSD) is a type of photoelectric detector widely used to measure parameters such as displacement, angular changes, and vibration of objects. In laser reflection-based measurement systems, a PSD can provide a precise position signal by receiving changes in the position of a laser spot. In this invention, a PSD is used to detect the displacement of a laser spot in a single direction. The surface of a PSD is typically made of a uniformly distributed resistive material. When a laser spot illuminates its surface, a photocurrent is generated at the point of illumination, and the signal is collected by two electrodes. Depending on the position of the laser spot on the resistive surface, the current is distributed to the two electrodes in different proportions. The position of the spot can be determined by measuring the current difference between the two electrodes.

[0067] like Figure 3 As shown, the center of the photosensitive area is set as the origin of the coordinate system, and the position of the laser spot on the photosensitive area, i.e., the spot position, is x. Then, the formula for the controller 9 to calculate the spot position based on the acquired current signal is:

[0068]

[0069] Where Δ=I L -I R ;Σ=I L +I R ;

[0070] In the formula, I0 is the magnitude of the photocurrent generated at the spot when the laser spot hits its photosensitive area;

[0071] I L and I R denoted by L and x, respectively, represent the photocurrents received by the first and second electrodes of the one-dimensional position detector 8; L represents the length of the photosensitive area of ​​the one-dimensional position detector 8; and x represents the calculated position of the light spot.

[0072] It should be noted that the photocurrent output from the electrodes at both ends of the one-dimensional position detector is also converted into a voltage signal by a resistor. When the galvanometer driver changes the rotation angle of the galvanometer (the galvanometer angle is based on the rotation angle of the galvanometer relative to the initial or reference position), the position of the visible light laser spot on the photosensitive area will shift, thereby changing the voltage signal output from both ends of the one-dimensional position detector. After passing through the data processing circuit board, these two signals are converted into voltage values ​​that characterize the actual position of the laser spot on the photosensitive area (with the center of the photosensitive area as the origin). In this invention, every 0.5V output voltage corresponds to a 1mm laser spot displacement, and positive and negative values ​​represent the direction of the laser spot.

[0073] The laser beam path emitted by the visible light laser 7 and the laser beam path emitted by the infrared laser chip 5 do not interfere with each other, so as to ensure that the beam of one is not blocked by the optical element of the other.

[0074] The output wavelength closed-loop adjustment method includes:

[0075] By adjusting the operating voltage of the galvanometer driver, the angle of the galvanometer is changed, thereby changing the position of the laser spot formed after reflection of the laser beam emitted by the visible light laser 7. The laser spot passes through multiple preset position points on the photosensitive area of ​​the one-dimensional position detector 8 in sequence. When the laser spot passes through each preset position point, the position of the position point, the corresponding operating voltage of the galvanometer driver, and the laser wavelength output by the resonant cavity at this time are recorded to form the calibration data corresponding to the position point and establish a calibration data table.

[0076] Set the target laser wavelength to be output from the resonant cavity, find the matching laser wavelength in the calibration data table, and obtain the corresponding galvanometer driver operating voltage through the matched laser wavelength;

[0077] Find the matching laser wavelength in the calibration data table, and obtain the corresponding galvanometer driver operating voltage using the matched laser wavelength. Specifically:

[0078] The calibration data table is searched for a matching laser wavelength. If a matching laser wavelength is found, the corresponding galvanometer driver operating voltage is obtained. If no matching laser wavelength is found, the calibration data table is interpolated using the interpolation method to obtain calibration data that matches the target laser wavelength.

[0079] The process of interpolating the calibration data table using an interpolation method to obtain calibration data that matches the target laser wavelength is as follows:

[0080] Find the two laser wavelengths that are closest to the target laser wavelength in the calibration data table and their corresponding calibration data;

[0081] Calculate the calibration data matching the target laser wavelength through the closest calibration data; the calculation formula includes:

[0082]

[0083] In the formula, V1 and V2 represent the operating voltages of the galvanometer driver in the closest calibration data; λ1 and λ2 represent the laser wavelengths corresponding to V1 and V2 in the closest calibration data respectively; x1 and x2 represent the spot positions corresponding to V1 and V2 in the closest calibration data respectively; λ represents the target laser wavelength; where: V1 < V < V2; V and x represent the operating voltage of the galvanometer driver and the spot position matching the target laser wavelength respectively.

[0084] Start the external cavity wide-spectrum tunable laser, and start the galvanometer driver with the operating voltage of the galvanometer driver obtained by matching, so that the galvanometer 2 rotates, and at the same time control the negative feedback adjustment device to enter the working state;

[0085] During the operation of the external cavity wide-spectrum tunable laser, calculate the real-time spot position through the negative feedback adjustment device, and match the spot position in the calibration data table through the real-time spot position to obtain the corresponding laser wavelength. By comparing the size of this laser wavelength with the target laser wavelength, determine the voltage adjustment value, and control the current operating voltage of the galvanometer driver to increase or decrease with the voltage adjustment value. Cycle this process to make the laser wavelength output by the resonant cavity reach the target laser wavelength, and after reaching the target laser wavelength, continuously adjust to keep the wavelength stable within the target laser wavelength or its allowable error range.

[0086] In addition, it should be noted that in this embodiment:

[0087] The change in the operating voltage of the galvanometer driver will cause the rotation direction of the galvanometer to change. Specifically:

[0088] When the operating voltage of the galvanometer driver increases: the galvanometer rotates in one direction.

[0089] When the operating voltage of the galvanometer driver decreases: the galvanometer rotates in the opposite direction.

[0090] This relationship is based on the basic principle of the galvanometer driver controlling the galvanometer. The increase or decrease of the operating voltage of the galvanometer driver will change the electromagnetic torque applied to the galvanometer, resulting in the galvanometer rotating in a specific direction.

[0091] In this embodiment, a minimum voltage change value, i.e., a voltage adjustment value, is set. When the laser wavelength is longer than the target laser wavelength, the voltage adjustment value is set to a negative value, and this negative voltage adjustment value is used to control the current galvanometer driver operating voltage to decrease, thereby causing the galvanometer 2 to rotate in the opposite direction; when the laser wavelength is shorter than the target laser wavelength, the voltage adjustment value is set to a positive value, and this positive voltage adjustment value is used to control the current galvanometer driver operating voltage to increase, thereby causing the galvanometer 2 to rotate in the other direction.

[0092] The corresponding laser wavelength is obtained by matching the real-time spot position with the spot position in the calibration data table. Specifically, if a matching spot position exists, the laser wavelength corresponding to that spot position is obtained. If no matching spot position exists, the calibration data table is interpolated using an interpolation method to obtain calibration data that matches the real-time spot position, and the laser wavelength in that calibration data is then obtained.

[0093] In this embodiment, the calibration data table is interpolated using an interpolation method to obtain calibration data that matches the real-time spot position. This interpolation method is the same as the above-mentioned method: interpolating the calibration data table using an interpolation method to obtain calibration data that matches the target laser wavelength. The only difference is that here, the corresponding laser wavelength and the working voltage of the galvanometer driver are calculated.

[0094] like Figure 4 As shown, since there is a certain mathematical relationship between the rotation angle of the galvanometer and the position of the laser spot, and the laser wavelength output by the resonant cavity changes based on the change of the galvanometer angle, this invention, in the structure of the external cavity broadband tuned laser, combines a negative feedback adjustment device, and by sharing the galvanometer in the external cavity broadband tuned laser, the position of the laser spot changes on the photosensitive area of ​​the one-dimensional position detector due to the rotation of the galvanometer angle, thereby achieving closed-loop precise control of the laser wavelength output by the resonant cavity.

[0095] Two aspects need to be explained in detail here:

[0096] 1. The rotation angle of the galvanometer and the position of the laser spot satisfy a certain mathematical relationship:

[0097] like Figure 4 As shown: When measuring the rotation angle of galvanometer 2 using a one-dimensional position detector 8, the beam emitted by the visible light laser 7 is obliquely incident on galvanometer 2, and the reflected beam generated by galvanometer 2 is incident on the photosensitive area of ​​the one-dimensional position detector 8. When galvanometer 2 rotates, the position of the reflected beam spot on the photosensitive area will shift accordingly. Let the incident angle of the beam emitted by the visible light laser 7 be θ0, and the rotation angle of galvanometer 2 be θ. The displacement Δx of the laser spot on the photosensitive area and the rotation angle θ of galvanometer 2 satisfy the following mathematical relationship:

[0098] Δx = d*tan(2θ);

[0099] Where d is the vertical distance between the laser incident point on galvanometer 2 and the PSD. When galvanometer 2 rotates at a small angle, tan(2θ) is approximately equal to 2θ, therefore the displacement of the laser spot is approximately linearly related to the rotation angle of galvanometer 2. By measuring the position change of the laser spot on the PSD and combining it with the known optical path distance d, the rotation angle of galvanometer 2 can be accurately calculated.

[0100] 2. The laser wavelength output by the resonant cavity varies based on the rotation angle of the galvanometer 2:

[0101] An external cavity broadband tunable laser places the laser gain device in a tunable external cavity, and achieves precise tuning of the output wavelength by adjusting the optical elements (such as gratings or mirrors) within the external cavity. In this embodiment, the laser output wavelength is changed by rotating the mirror 2 in the external cavity. The blazed grating 1 reflects light of different wavelengths back into the resonant cavity at different angles.

[0102] When the length of the external cavity is adjusted by rotating or translating galvanometer 2, galvanometer 2 changes the path of light, thereby altering the effective length of the optical cavity. Assuming the rotation angle of galvanometer 2 is θ, and the optical path distance from galvanometer 2 to blazed grating 1 is D, at small angles, the change in optical path ΔF is approximately:

[0103] ΔF=F2-F1≈2D·sin(θ);

[0104] In the formula, F1 represents the optical path distance from the incident point of the galvanometer to the first collimating lens 4, and F2 represents the length of the resonant cavity;

[0105] The mode wavelength κ of the optical cavity (i.e., the external cavity) is related to the cavity length F, and is generally expressed as:

[0106] Where m is the order of the mode (a positive integer), and the optical cavity length F = D + F1 + F2;

[0107] It needs to be explained that the mode wavelength of an optical cavity refers to a specific wavelength that is allowed to exist within the resonant cavity. Through a preset gain curve, several specific wavelengths are selected, and then they are allowed to continue to compete. Finally, the wavelength with the strongest light intensity is emitted as the output wavelength.

[0108] When galvanometer 2 rotates, the incident angle θ0 changes, according to the above formula. The output laser wavelength λ will also change accordingly, and the amount of wavelength change is:

[0109]

[0110] In the formula, λ′ represents the laser wavelength output by the resonant cavity after the rotation angle of the galvanometer 2 changes; λ represents the laser wavelength output by the resonant cavity before the rotation angle changes.

[0111] Therefore, for small angle changes, the output laser wavelength λ and the rotation angle θ of galvanometer 2 have an approximately linear relationship. By controlling the rotation angle of galvanometer 2, continuous tuning of the laser output wavelength can be achieved, thereby covering a relatively wide wavelength range.

[0112] As can be seen from the detailed explanation of the above two aspects: by sharing the galvanometer in the external cavity broadband tuned laser, the position of the laser spot on the photosensitive area of ​​the one-dimensional position detector is changed due to the rotation of the galvanometer angle, and closed-loop precise control of the output laser wavelength of the resonant cavity can be achieved.

[0113] This invention adjusts the operating voltage of the galvanometer driver to cause the laser beam emitted by a visible light laser to sequentially pass through multiple preset position points on the photosensitive area of ​​a one-dimensional position detector. At each preset position point, the position, corresponding galvanometer driver operating voltage, and laser wavelength output from the resonant cavity are recorded, forming calibration data for that position point, and a calibration data table is established. During the operation of the external cavity broadband tuned laser, the real-time spot position is calculated using a negative feedback adjustment device, and the corresponding laser wavelength is obtained by matching the real-time spot position with the spot position in the calibration data table. By comparing this laser wavelength with the target laser wavelength, a voltage adjustment value is determined, and the voltage adjustment value is used to control the current galvanometer driver operating voltage to increase or decrease. This process is repeated until the laser wavelength output from the resonant cavity stabilizes within the target laser wavelength or its allowable error range. This achieves precise control of the galvanometer rotation angle, improving the repeatability and accuracy of the output wavelength.

[0114] Example 2

[0115] like Figure 2 As shown, the present invention also proposes an output wavelength closed-loop adjustment system based on a negative feedback adjustment device, which is applied to an external cavity broadband tuned laser.

[0116] The external cavity broadband tunable laser includes: a galvanometer, a galvanometer driver for controlling the angle of the galvanometer, and a resonant cavity; the laser wavelength output by the resonant cavity varies based on the change in the angle of the galvanometer.

[0117] The external cavity broadband tuned laser also includes:

[0118] A blazed grating is used for wavelength selection, reflecting light of a specific wavelength back to the resonant cavity through diffraction.

[0119] The resonant cavity is composed of a first collimating lens, a laser gain chip, and a second collimating lens. Photons emitted by the laser gain chip pass through the first collimating lens. The photons passing through the first collimating lens are reflected by a galvanometer to a blazed grating. The blazed grating diffracts according to the wavelength of the incident light. The diffracted photons are reflected by the galvanometer and then reflected back into the laser gain chip by the first collimating lens. When the wavelength is selected by the blazed grating, the light of a specific wavelength is amplified in the resonant cavity. When its intensity exceeds the lasing threshold of that wavelength, the laser of the specific wavelength selected by the galvanometer and the blazed grating is output through the second collimating lens.

[0120] The negative feedback adjustment device includes: a visible light laser and a one-dimensional position detector; the visible light laser is used to emit a laser beam, which is reflected to the one-dimensional position detector through a galvanometer in an external cavity broadband tuned laser; the negative feedback adjustment device also includes: a controller;

[0121] The one-dimensional position detector is used to generate a photocurrent at the spot illumination point when the laser spot hits its photosensitive area, and the current signal is collected by the electrodes at both ends of the one-dimensional position detector.

[0122] The controller calculates the position of the light spot based on the collected current signal; the position of the light spot is the vertical distance between the light spot and the center line of the photosensitive area.

[0123] The output wavelength closed-loop adjustment system includes:

[0124] The calibration module is used to change the galvanometer angle by adjusting the operating voltage of the galvanometer driver, thereby changing the position of the laser spot formed after reflection of the laser beam emitted by the visible light laser. The laser spot passes through multiple preset position points on the photosensitive area of ​​the one-dimensional position detector in sequence. When the laser spot passes through each preset position point, the position of the position point, the corresponding operating voltage of the galvanometer driver, and the laser wavelength output by the resonant cavity at this time are recorded to form the calibration data corresponding to the position point and establish a calibration data table.

[0125] The matching module is used to set the target laser wavelength to be output by the resonant cavity, find the matching laser wavelength in the calibration data table, and obtain the corresponding galvanometer driver operating voltage through the matched laser wavelength.

[0126] The startup module is used to start the external cavity broadband tuned laser and start the galvanometer driver with the matched galvanometer driver working voltage to make the galvanometer rotate, while controlling the negative feedback adjustment device to enter the working state.

[0127] The closed-loop adjustment module is used to calculate the real-time spot position through a negative feedback adjustment device during the operation of the external cavity broadband tuned laser. By matching the spot position in the calibration data table with the real-time spot position, the corresponding laser wavelength is obtained. By comparing the laser wavelength with the target laser wavelength, the voltage adjustment value is determined, and the voltage adjustment value is used to control the current galvanometer driver operating voltage to increase or decrease. This process is repeated to make the laser wavelength output by the resonant cavity reach the target laser wavelength. After reaching the target laser wavelength, the module is continuously adjusted to keep the wavelength stable within the target laser wavelength or its allowable error range.

[0128] This invention, by using a negative feedback adjustment device, can monitor and adjust the laser wavelength in real time, significantly improving the accuracy of wavelength adjustment; the calibration data sheet ensures the correspondence between the working voltage of the galvanometer driver and the actual laser wavelength, thereby achieving precise control of the output wavelength.

[0129] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0130] Furthermore, in this invention, descriptions involving terms such as "first," "second," and "a" are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0131] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0132] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

Claims

1. A closed-loop adjustment method for output wavelength based on a negative feedback adjustment device, characterized in that, Applications in external cavity broadband tuned lasers; The external cavity broadband tunable laser includes: a galvanometer, a galvanometer driver for controlling the angle of the galvanometer, and a resonant cavity; the laser wavelength output by the resonant cavity varies based on the change in the angle of the galvanometer. The negative feedback adjustment device includes: a visible light laser and a one-dimensional position detector; the visible light laser is used to emit a laser beam, which is reflected to the one-dimensional position detector through a galvanometer in an external cavity broadband tuned laser; the output wavelength closed-loop adjustment method includes: By adjusting the operating voltage of the galvanometer driver, the angle of the galvanometer is changed, thereby altering the position of the laser spot formed after reflection by the laser beam emitted by the visible light laser. This causes the laser spot to sequentially pass through multiple preset position points on the photosensitive area of ​​the one-dimensional position detector. When the laser spot passes through each preset position point, the position of that point, the corresponding operating voltage of the galvanometer driver, and the laser wavelength output by the resonant cavity at that time are recorded to form the calibration data corresponding to that position point, and a calibration data table is established. Set the target laser wavelength to be output from the resonant cavity, find the matching laser wavelength in the calibration data table, and obtain the corresponding galvanometer driver operating voltage through the matched laser wavelength; Start the external cavity broadband tuned laser and start the galvanometer driver with the matched galvanometer driver working voltage to make the galvanometer rotate, while controlling the negative feedback adjustment device to enter the working state. During the operation of the external cavity broadband tuned laser, the real-time spot position is calculated by the negative feedback adjustment device, and the corresponding laser wavelength is obtained by matching the spot position in the calibration data table with the real-time spot position. By comparing the laser wavelength with the target laser wavelength, the voltage adjustment value is determined, and the voltage adjustment value is used to control the current galvanometer driver operating voltage to increase or decrease. This process is repeated to make the laser wavelength output by the resonant cavity reach the target laser wavelength. After reaching the target laser wavelength, the adjustment is continuously made to keep the wavelength stable within the target laser wavelength or its allowable error range.

2. The closed-loop adjustment method for output wavelength based on a negative feedback adjustment device according to claim 1, characterized in that, The negative feedback adjustment device further includes: a controller; The one-dimensional position detector is used to generate a photocurrent at the spot illumination point when the laser spot hits its photosensitive area, and the current signal is collected by the electrodes at both ends of the one-dimensional position detector. The controller calculates the position of the light spot based on the collected current signal; the position of the light spot is the vertical distance between the light spot and the center line of the photosensitive area.

3. The output wavelength closed-loop adjustment method based on a negative feedback adjustment device according to claim 2, characterized in that, The external cavity broadband tuned laser also includes: A blazed grating is used for wavelength selection, reflecting light of a specific wavelength back to the resonant cavity through diffraction. The resonant cavity is composed of a first collimating lens, a laser gain chip, and a second collimating lens. Photons emitted by the laser gain chip pass through the first collimating lens. The photons passing through the first collimating lens are reflected by a galvanometer to a blazed grating. The blazed grating diffracts according to the wavelength of the incident light. The diffracted photons are reflected by the galvanometer and then reflected back into the laser gain chip by the first collimating lens. When the wavelength is selected by the blazed grating, the light of a specific wavelength is amplified in the resonant cavity. When its intensity exceeds the lasing threshold of that wavelength, the laser of the specific wavelength selected by the galvanometer and the blazed grating is output through the second collimating lens.

4. The output wavelength closed-loop adjustment method based on a negative feedback adjustment device according to claim 3, characterized in that, The laser optical path emitted by the visible light laser does not interfere with the laser optical path emitted by the laser gain chip, so as to ensure that the beam of one party will not be blocked by the optical elements of the other party.

5. The output wavelength closed-loop adjustment method based on a negative feedback adjustment device according to claim 4, characterized in that, Search for the matching laser wavelength in the calibration data table, and obtain the corresponding working voltage of the galvanometer driver through the obtained laser wavelength. Specifically: Search for the matching laser wavelength in the calibration data table; if there is a matching laser wavelength, obtain the corresponding working voltage of the galvanometer driver. If there is no matching laser wavelength, interpolate the calibration data table by the interpolation method to obtain the calibration data matching the target laser wavelength; Match the real-time spot position with the spot position in the calibration data table to obtain the corresponding laser wavelength. Specifically: Match the real-time spot position with the spot position in the calibration data table. If there is a matching spot position, obtain the laser wavelength corresponding to the spot position. If there is no matching spot position, interpolate the calibration data table by the interpolation method to obtain the calibration data matching the real-time spot position, and obtain the laser wavelength in the calibration data.

6. The output wavelength closed-loop adjustment method based on a negative feedback adjustment device according to claim 5, characterized in that, The interpolation method is used to interpolate the calibration data table to obtain the calibration data matching the target laser wavelength. Specifically: Search for the two laser wavelengths closest to the target laser wavelength and their corresponding calibration data in the calibration data table; Calculate the calibration data matching the target laser wavelength through the closest calibration data; the calculation formula includes: In the formula, V1 and V2 represent the working voltages of the galvanometer drivers in the closest calibration data; λ1 and λ2 represent the laser wavelengths corresponding to V1 and V2 in the closest calibration data; x1 and x2 represent the spot positions corresponding to V1 and V2 in the closest calibration data; λ represents the target laser wavelength; where: V1 < V < V2; V and x respectively represent the working voltage of the galvanometer driver and the spot position matching the target laser wavelength.

7. The output wavelength closed-loop adjustment method based on a negative feedback adjustment device according to claim 5, characterized in that, The controller calculates the spot position according to the collected current signal. The calculation formula is: Wherein, Δ = I L -I R ;Σ=I L +I R ; In the formula, I0 is the magnitude of the photocurrent generated at the irradiated area when the laser spot strikes its photosensitive region; I L and I R represents the photocurrent received by the first and second electrodes of the one-dimensional position detector, respectively; L represents the length of the photosensitive area of ​​the one-dimensional position detector; x represents the calculated position of the light spot.

8. A closed-loop output wavelength adjustment system based on a negative feedback adjustment device, characterized in that, Applied to an external cavity wide-spectrum tunable laser; The external cavity wide-spectrum tunable laser includes: a galvanometer, a galvanometer driver for controlling the galvanometer angle, and a resonant cavity; the laser wavelength output by the resonant cavity changes based on the change of the galvanometer angle; The negative feedback adjustment device includes: a visible light laser and a one-dimensional position detector; the visible light laser is used to emit a laser beam, which is reflected by the galvanometer in the external cavity wide-spectrum tunable laser to the one-dimensional position detector; the output wavelength closed-loop adjustment system includes: A calibration module, which is used to change the galvanometer angle by adjusting the working voltage of the galvanometer driver, and then change the spot position formed after the reflection of the laser beam emitted by the visible light laser, so that the spot passes through multiple preset position points on the photosensitive area of the one-dimensional position detector in turn; when the spot passes through each preset position point, record the position of the position point as the spot position, the corresponding working voltage of the galvanometer driver, and the laser wavelength output by the resonant cavity at this time, form the calibration data corresponding to the position point, and establish a calibration data table; The matching module is used to set the target laser wavelength to be output by the resonant cavity, find the matching laser wavelength in the calibration data table, and obtain the corresponding galvanometer driver operating voltage through the matched laser wavelength. The startup module is used to start the external cavity broadband tuned laser and start the galvanometer driver with the matched galvanometer driver working voltage to make the galvanometer rotate, while controlling the negative feedback adjustment device to enter the working state. The closed-loop adjustment module is used to calculate the real-time spot position through a negative feedback adjustment device during the operation of the external cavity broadband tuned laser. By matching the spot position in the calibration data table with the real-time spot position, the corresponding laser wavelength is obtained. By comparing the laser wavelength with the target laser wavelength, the voltage adjustment value is determined, and the voltage adjustment value is used to control the current galvanometer driver operating voltage to increase or decrease. This process is repeated to make the laser wavelength output by the resonant cavity reach the target laser wavelength. After reaching the target laser wavelength, the module is continuously adjusted to keep the wavelength stable within the target laser wavelength or its allowable error range.

9. The output wavelength closed-loop adjustment system based on a negative feedback adjustment device according to claim 8, characterized in that, The negative feedback adjustment device further includes: a controller; The one-dimensional position detector is used to generate a photocurrent at the spot illumination point when the laser spot hits its photosensitive area, and the current signal is collected by the electrodes at both ends of the one-dimensional position detector. The controller calculates the position of the light spot based on the collected current signal; the position of the light spot is the vertical distance between the light spot and the center line of the photosensitive area.

10. The output wavelength closed-loop adjustment system based on a negative feedback adjustment device according to claim 9, characterized in that, The external cavity broadband tuned laser also includes: A blazed grating is used for wavelength selection, reflecting light of a specific wavelength back to the resonant cavity through diffraction. The resonant cavity is composed of a first collimating lens, a laser gain chip, and a second collimating lens. Photons emitted by the laser gain chip pass through the first collimating lens. The photons passing through the first collimating lens are reflected by a galvanometer to a blazed grating. The blazed grating diffracts according to the wavelength of the incident light. The diffracted photons are reflected by the galvanometer and then reflected back into the laser gain chip by the first collimating lens. When the wavelength is selected by the blazed grating, the light of a specific wavelength is amplified in the resonant cavity. When its intensity exceeds the lasing threshold of that wavelength, the laser of the specific wavelength selected by the galvanometer and the blazed grating is output through the second collimating lens.

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