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

Abstract

The invention discloses an output wavelength closed-loop adjustment method and system based on a negative feedback adjustment device, and relates to the field of external cavity quantum cascade lasers. According to the output wavelength closed-loop adjusting method, during the working period of the external cavity wide-spectrum tuning laser, the real-time light spot position is calculated through a negative feedback adjusting device, the real-time light spot position is matched with the light spot position in a calibration data table to obtain the corresponding laser wavelength, and the output wavelength is adjusted by comparing the laser wavelength with the target laser wavelength. Determining a voltage adjustment value, controlling the current working voltage of the galvanometer driver to be increased or decreased according to the voltage adjustment value, and circulating the process until the laser wavelength output by the resonant cavity is stabilized in the target laser wavelength or an allowable error range thereof; accurate control over the rotating angle of the galvanometer is achieved, and repeatability and accuracy of the output wavelength are improved.

Description

Technical Field

[0001] The invention relates to the field of external cavity wide spectrum tunable lasers, and in particular to an output wavelength closed-loop regulation method and system based on a negative feedback regulation device. Background Art

[0002] The external cavity wide spectrum tunable laser works based on the external cavity principle. Its characteristic is that the laser gain device is placed in an angle-tunable external cavity, and the output wavelength is precisely tuned by adjusting the rotation angle of the galvanometer in the external cavity. However, in practical applications, since the rotation angle of the galvanometer is usually controlled by the voltage output by the driver, and the accuracy of the output voltage and the existence of factors such as mechanical friction and aging make it difficult to achieve precise control of the rotation angle of the galvanometer, which in turn affects the repeatability and accuracy of the output wavelength of the external cavity laser. Among them, repeatability refers to the consistency of multiple measurement results under the same conditions. Summary of the invention

[0003] In order to accurately control the rotation angle of the galvanometer and improve the repeatability and accuracy of the output wavelength of the external cavity laser, the present invention proposes an output wavelength closed-loop adjustment method based on a negative feedback adjustment device, which is applied to the external cavity wide spectrum tunable laser;

[0004] The external cavity wide spectrum tunable laser comprises: a galvanometer, a galvanometer driver for controlling the angle of the galvanometer, and a resonant cavity; the laser wavelength output by the resonant cavity changes based on the change of the galvanometer angle;

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

[0006] By adjusting the working voltage of the galvanometer driver, the galvanometer angle is changed, thereby changing the position of the light spot formed by the laser beam emitted by the visible light laser after reflection, so that the light spot passes through a plurality of preset position points on the photosensitive area of ​​the one-dimensional position detector in sequence; when the light spot passes through each preset position point, the position of the position point is recorded as the light spot position, the corresponding galvanometer driver working voltage and the laser wavelength output by the resonant cavity at this time, so as to form the calibration data corresponding to the position point, and establish a calibration data table;

[0007] Set the target laser wavelength to be output by the resonant cavity, and search for the matching laser wavelength in the calibration data table, and obtain the corresponding galvanometer driver operating voltage by matching the obtained laser wavelength;

[0008] The external cavity wide spectrum tunable laser is started, and the galvanometer driver is started with the matched galvanometer driver working voltage to rotate the galvanometer, and at the same time, the negative feedback regulating device is controlled to enter the working state;

[0009] During the operation of the external cavity wide spectrum tunable laser, the real-time spot position is calculated by a negative feedback adjustment device, and the real-time spot position is matched with the spot position in the calibration data table to obtain the corresponding laser wavelength. 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, and after reaching the target laser wavelength, continuous adjustment is performed to keep the wavelength stable within the target laser wavelength or its allowable error range.

[0010] Furthermore, the negative feedback regulation device further comprises: a controller;

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

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

[0013] Furthermore, the external cavity wide spectrum tunable laser also includes:

[0014] Blazed gratings, used for wavelength selection, reflect light of a specific wavelength back into the resonant cavity by diffraction;

[0015] The resonant cavity is composed of a first collimating lens, a laser gain chip and a second collimating lens; the photons emitted by the laser gain chip pass through the first collimating lens; the photons passing through the first collimating lens are reflected by the galvanometer to the blazed grating; the blazed grating diffracts according to the wavelength of the incident light; the diffracted photons are reflected by the galvanometer and reflected back into the laser gain chip through the first collimating lens; after the wavelength is selected by the blazed grating, the light of a specific wavelength is gain-amplified in the resonant cavity, and when its intensity exceeds the lasing threshold of the 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 light path emitted by the visible light laser and the laser light path emitted by the laser gain chip do not interfere with each other, so as to ensure that the light beam of one will not be blocked by the optical element of the other.

[0017] Furthermore, the matching laser wavelength is searched in the calibration data table, and the corresponding galvanometer driver operating voltage is obtained by matching the obtained 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 galvanometer driver operating voltage; 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 this 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 this 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 from the closest calibration data; the calculation formula includes:

[0023]

[0024] In the formula, V1 and V2 represent the galvanometer driver operating voltages in the closest calibration data; λ1 and λ2 represent the laser wavelengths corresponding to V1 and V2 respectively in the closest calibration data; x1 and x2 represent the spot positions corresponding to V1 and V2 respectively in the closest calibration data; λ represents the target laser wavelength; where: V1 < V < V2; V and x represent the galvanometer driver operating voltage and 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 L - I R ; Σ = I L + I R ;

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

[0029] I L and I RThey respectively represent the photocurrents received by the first end electrode and the second end electrode of the one-dimensional position detector; L represents the length of the photosensitive area of ​​the one-dimensional position detector; and x represents the calculated spot position.

[0030] The embodiment of 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 wide spectrum tunable laser;

[0031] The external cavity wide spectrum tunable laser comprises: a galvanometer, a galvanometer driver for controlling the angle of the galvanometer, and a resonant cavity; the laser wavelength output by the resonant cavity changes based on the change of the galvanometer angle;

[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, and is reflected to the one-dimensional position detector through a galvanometer in an external cavity wide spectrum tunable laser; the output wavelength closed-loop adjustment system includes:

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

[0034] A matching module is used to set the target laser wavelength to be output by the resonant cavity, and to search for a matching laser wavelength in a calibration data table, and to obtain a corresponding galvanometer driver operating voltage by matching the obtained laser wavelength;

[0035] A starting module is used to start the external cavity wide spectrum tunable laser, and start the galvanometer driver with the matched galvanometer driver working voltage to rotate the galvanometer, and control the negative feedback regulating device to enter the working state;

[0036] The closed-loop regulation module is used to calculate the real-time spot position through a negative feedback regulation device during the operation of the external cavity wide spectrum tunable laser, and to match the spot position in the calibration data table through the real-time spot position to obtain the corresponding laser wavelength, and to determine the voltage adjustment value by comparing the laser wavelength with the target laser wavelength, and to control the current galvanometer driver working voltage to increase or decrease with the voltage adjustment value, and to repeat this process so that the laser wavelength output by the resonant cavity reaches the target laser wavelength, and after reaching the target laser wavelength, to continuously adjust to keep the wavelength stable within the target laser wavelength or its allowable error range.

[0037] Furthermore, the negative feedback regulation device further comprises: a controller;

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

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

[0040] Furthermore, the external cavity wide spectrum tunable laser also includes:

[0041] Blazed gratings, used for wavelength selection, reflect light of a specific wavelength back into the resonant cavity by diffraction;

[0042] The resonant cavity is composed of a first collimating lens, a laser gain chip and a second collimating lens; the photons emitted by the laser gain chip pass through the first collimating lens; the photons passing through the first collimating lens are reflected by the galvanometer to the blazed grating; the blazed grating diffracts according to the wavelength of the incident light; the diffracted photons are reflected by the galvanometer and reflected back into the laser gain chip through the first collimating lens; after the wavelength is selected by the blazed grating, the light of a specific wavelength is gain-amplified in the resonant cavity, and when its intensity exceeds the lasing threshold of the 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) The present invention adjusts the working voltage of the galvanometer driver so that the light spot formed by the laser beam emitted by the visible light laser passes through a plurality of preset position points on the photosensitive area of ​​the one-dimensional position detector in sequence; when the light spot passes through each preset position point, the position of the position point is recorded as the light spot position, the corresponding galvanometer driver working voltage and the laser wavelength output by the resonant cavity at this time, so as to form calibration data corresponding to the position point, and establish a calibration data table; during the operation of the external cavity wide spectrum tunable laser, the real-time light spot position is calculated by a negative feedback adjustment device, and the real-time light spot position is matched with the light spot position in the calibration data table to obtain the corresponding laser wavelength, and the voltage adjustment value is determined by comparing the laser wavelength with the target laser wavelength, and the current galvanometer driver working voltage is controlled to increase or decrease by the voltage adjustment value, and this process is repeated until the laser wavelength output by the resonant cavity is stabilized within the target laser wavelength or within its allowable error range; thus, precise control of the galvanometer rotation angle is achieved, and the repeatability and accuracy of the output wavelength are improved;

[0045] (2) The present invention can monitor and adjust the laser wavelength in real time by using a negative feedback adjustment device, thereby significantly improving the accuracy of wavelength adjustment; the calibration data table ensures the corresponding relationship between the operating voltage of the galvanometer driver and the actual laser wavelength, thereby achieving accurate control of the output wavelength;

[0046] (3) The present invention can continuously monitor the real-time spot position through a closed-loop adjustment mechanism, and dynamically adjust the operating voltage of the galvanometer driver according to the actual measurement results, ensuring that the output wavelength is always stable near the target laser wavelength, thereby improving 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 reduces the difficulty and error rate of operation. The user only needs to set the target laser wavelength, and the system can automatically complete the adjustment process;

[0048] (5) The present invention can timely detect and correct wavelength deviation through a closed-loop adjustment module, thereby improving the reliability and robustness of the system and maintaining the accuracy of the output wavelength even in the presence of factors such as the accuracy of the output voltage of the galvanometer driver and mechanical friction. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is the overall structure diagram of the external cavity wide spectrum tunable laser and the negative feedback regulating device;

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

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

[0052] Figure 4 Schematic diagram of the relationship between the galvanometer rotation angle and the laser spot position.

[0053] In the figure:

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

[0055] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0056] Embodiment 1

[0057] There is a positive correlation between the output wavelength of the external cavity laser and the rotation angle of the galvanometer. The rotation angle of the galvanometer is controlled by the galvanometer driver. When voltages of different magnitudes are applied, the rotation angle of the galvanometer will change. However, due to the accuracy of the galvanometer driver voltage and other reasons, the galvanometer rotation angles are often different at the same voltage point. This deficiency causes the output wavelength error to reach ±3nm, which is unacceptable in some high-precision spectrometers. In order to solve the problem of low repeatability of the galvanometer rotation angle, the present invention proposes an output wavelength closed-loop adjustment method based on a negative feedback adjustment device, which is applied to an external cavity wide-spectrum tunable laser;

[0058] like Figure 1 As shown, the external cavity wide spectrum tunable laser comprises: a galvanometer 2, a galvanometer driver 3 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 (rotation angle);

[0059] The external cavity wide spectrum tunable laser also includes:

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

[0061] The resonant cavity is composed of a first collimating lens 4, a laser gain chip 5 and a second collimating lens 6; the photons emitted by 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 reflected back into the laser gain chip 5 through the first collimating lens 4; after the wavelength selection of the blazed grating 1, the light of a specific wavelength is gain-amplified in the resonant cavity, and when its intensity exceeds the lasing threshold of the 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. Among them, in addition to reflecting part of the light back into the resonant cavity, the second collimating lens 6 also serves as the transmitting end of the entire external cavity wide-spectrum tunable laser, and emits the laser whose power exceeds the lasing threshold.

[0062] The negative feedback regulating device comprises: a visible light laser 7 and a one-dimensional position detector 8; the visible light laser 7 is used to emit a laser beam, and is reflected to the one-dimensional position detector 8 through the galvanometer 2 in the external cavity wide spectrum tunable laser; the negative feedback regulating device also comprises: a controller 9;

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

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

[0065] The controller 9 calculates the light spot position according to the collected current signal; the light spot position 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 the one-dimensional position detector (PSD) is a photoelectric detector, which is widely used to measure parameters such as displacement, angle change and vibration of an object. In a measurement system based on laser reflection, the PSD can provide an accurate position signal by receiving the position change of the laser spot. In the present invention, the PSD is used to detect the displacement of the laser spot in a single direction. The surface of the PSD is usually made of a uniformly distributed resistor material. When the laser spot is irradiated onto its surface, a photocurrent is generated at the irradiation point of the spot, and the signal is collected by two electrodes. According to the position of the laser spot on the resistor surface, the current will be distributed to the two electrodes in different proportions, and the position of the spot can be obtained by measuring the current difference at both ends.

[0067] like Figure 3 As shown, the center of the photosensitive area is set as the coordinate origin, and the position of the laser spot on the photosensitive area, that is, the spot position, is x. Then the controller 9 calculates the spot position according to the collected current signal using the following calculation formula:

[0068]

[0069] Where Δ=I L -I R ;Σ=I L +I R ;

[0070] Where, I0 is the photocurrent generated at the spot when the laser spot hits its photosensitive area;

[0071] I L and I R They respectively represent the photocurrents received by the first end electrode and the second end electrode 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 light spot position.

[0072] It should be noted that the photocurrent output by the electrodes at both ends of the one-dimensional position detector will also be converted into a voltage signal through 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 position or reference position), the spot position of the visible light laser on the photosensitive area will be displaced, and thus the voltage signals output at both ends of the one-dimensional position detector will also change. After passing through the data processing circuit board, these two signals will be converted into voltage values ​​used to characterize the true position of the spot on the photosensitive area (with the center of the photosensitive area as the origin). In the present invention, every 0.5V output voltage corresponds to a 1mm laser spot displacement, and the positive and negative represent the direction of the spot.

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

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

[0075] By adjusting the working voltage of the galvanometer driver, the galvanometer angle is changed, thereby changing the position of the light spot formed by the laser beam emitted by the visible light laser 7 after reflection, so that the light spot passes through a plurality of preset position points on the photosensitive area of ​​the one-dimensional position detector 8 in sequence; when the light spot passes through each preset position point, the position of the position point is recorded as the light spot position, the corresponding galvanometer driver working voltage and the laser wavelength output by the resonant cavity at this time, so as 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 by the resonant cavity, and search for the matching laser wavelength in the calibration data table, and obtain the corresponding galvanometer driver operating voltage by matching the obtained laser wavelength;

[0077] Find the matching laser wavelength in the calibration data table, and obtain the corresponding galvanometer driver operating voltage by matching the obtained laser wavelength, specifically:

[0078] Search the calibration data table for a matching laser wavelength; if there is a matching laser wavelength, obtain the corresponding galvanometer driver operating voltage; if there is no matching laser wavelength, interpolate the calibration data table through the interpolation method to obtain calibration data matching the target laser wavelength;

[0079] The calibration data table is interpolated by the interpolation method to obtain calibration data matching the target laser wavelength, specifically:

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

[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 working voltages of the galvanometer driver in the closest calibration data; λ1 and λ2 represent the laser wavelengths corresponding to V1 and V2 respectively in the closest calibration data; x1 and x2 represent the spot positions corresponding to V1 and V2 respectively 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.

[0084] Start the external cavity wide-spectrum tunable laser, and start the galvanometer driver with the working 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 working 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 working voltage of the galvanometer driver will cause the rotation direction of the galvanometer to change. Specifically:

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

[0089] When the working 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 working voltage of the galvanometer driver will change the electromagnetic torque applied to the galvanometer, thereby causing the galvanometer to rotate in a specific direction.

[0091] In this embodiment, a minimum value of voltage change, namely, 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 the current galvanometer driver working voltage is controlled to decrease by the negative voltage adjustment value, so that the galvanometer 2 rotates 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 the current galvanometer driver working voltage is controlled to increase by the positive voltage adjustment value, so that the galvanometer 2 rotates 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, the real-time spot position is matched with the spot position in the calibration data table. If there is a matching spot position, the laser wavelength corresponding to the spot position is obtained. If there is no matching spot position, the calibration data table is interpolated by the interpolation method to obtain calibration data matching the real-time spot position, and the laser wavelength in the calibration data is obtained.

[0093] In this embodiment, the calibration data table is interpolated by the interpolation method to obtain calibration data that matches the real-time spot position. The interpolation method is the same as the above: the calibration data table is interpolated by the interpolation method to obtain calibration data that matches the target laser wavelength, except that the corresponding laser wavelength and the galvanometer driver operating voltage are calculated here.

[0094] like Figure 4 As shown, since the rotation angle of the galvanometer and the position of the laser spot satisfy a certain mathematical relationship, and the laser wavelength output by the resonant cavity changes based on the change of the galvanometer angle, the present invention combines a negative feedback adjustment device with the structure of the external cavity wide spectrum tunable laser. By sharing the galvanometer in the external cavity wide spectrum tunable laser, the rotation of the galvanometer angle causes the position of the laser spot to change on the photosensitive area of ​​the one-dimensional position detector, thereby realizing closed-loop precise control of the laser wavelength output by the resonant cavity.

[0095] There are two aspects that need to be explained in detail here:

[0096] 1. There is a certain mathematical relationship between the galvanometer rotation angle and the laser spot position:

[0097] like Figure 4 As shown: when using the one-dimensional position detector 8 to measure the rotation angle of the galvanometer 2, the light beam emitted by the visible light laser 7 is incident on the galvanometer 2 obliquely, and the reflected light beam generated by the galvanometer 2 is incident on the photosensitive area of ​​the one-dimensional position detector 8. When the galvanometer 2 rotates, the spot position of the reflected light beam on the photosensitive area will be displaced accordingly. Assuming that the incident angle of the light beam emitted by the visible light laser 7 is θ0, and the rotation angle of the galvanometer 2 is θ, the displacement △x of the laser spot on the photosensitive area and the rotation angle θ of the 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 the galvanometer 2 and the PSD. When the galvanometer 2 rotates at a small angle, tan(2θ) is approximately equal to 2θ, so the displacement of the laser spot is approximately linearly related to the rotation angle of the 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 the galvanometer 2 can be accurately calculated.

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

[0101] The external cavity wide spectrum 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 galvanometers) in the external cavity. In this embodiment, the laser output wavelength is changed by rotating the galvanometer 2 in the external cavity. The blazed grating 1 reflects light of different wavelengths back to the resonant cavity at different angles.

[0102] When the length of the external cavity is adjusted by rotating or translating the galvanometer 2, the galvanometer 2 will change the path of the light, thereby changing the effective length of the optical cavity. Assuming that the rotation angle of the galvanometer 2 is θ, the optical path distance of the laser reflected from the galvanometer 2 to the blazed grating 1 is D. At a small angle, the optical path change ΔF is approximately:

[0103] ΔF=F2-F1≈2D·sin(θ);

[0104] Wherein, 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 optical cavity length F, which 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 the optical cavity refers to the specific wavelength allowed to exist in the resonant cavity. Through the preset gain curve, several specific wavelengths are screened out, 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 the galvanometer 2 rotates, the incident angle θ0 changes. According to the above formula, The output laser wavelength λ will also change accordingly, and the change in wavelength is:

[0109]

[0110] Wherein, λ′ represents the laser wavelength output by the resonant cavity after the rotation angle of the galvanometer 2 is changed; λ represents the laser wavelength output by the resonant cavity before the rotation angle is changed;

[0111] It can be seen that for small angle changes, the output laser wavelength λ and the rotation angle θ of the galvanometer 2 are approximately linear. By controlling the rotation angle of the galvanometer 2, the laser output wavelength can be continuously tuned to cover a wider wavelength range.

[0112] Through the detailed explanation of the above two aspects, it can be known that by sharing the galvanometer in the external cavity wide spectrum tunable laser, the rotation of the galvanometer angle causes the laser spot position to change on the photosensitive area of ​​the one-dimensional position detector, thereby realizing closed-loop precise control of the laser wavelength output by the resonant cavity.

[0113] The present invention adjusts the working voltage of a galvanometer driver so that a light spot formed by a laser beam emitted by a visible light laser sequentially passes through a plurality of preset position points on a photosensitive area of ​​a one-dimensional position detector; when the light spot passes through each preset position point, the position of the position point is recorded as the light spot position, the corresponding galvanometer driver working voltage and the laser wavelength output by the resonant cavity at this time, so as to form calibration data corresponding to the position point, and establish a calibration data table; during the operation of the external cavity wide spectrum tunable laser, the real-time light spot position is calculated by a negative feedback regulating device, and the light spot position in the calibration data table is matched by the real-time light spot position to obtain the corresponding laser wavelength, and the voltage adjustment value is determined by comparing the laser wavelength with the target laser wavelength, and the current galvanometer driver working voltage is controlled to increase or decrease by the voltage adjustment value, and this process is repeated until the laser wavelength output by the resonant cavity is stabilized within the target laser wavelength or within an allowable error range thereof; the precise control of the galvanometer rotation angle is achieved, and the repeatability and accuracy of the output wavelength are improved.

[0114] Embodiment 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 wide spectrum tunable laser;

[0116] The external cavity wide spectrum tunable laser comprises: a galvanometer, a galvanometer driver for controlling the angle of the galvanometer, and a resonant cavity; the laser wavelength output by the resonant cavity changes based on the change of the galvanometer angle;

[0117] The external cavity wide spectrum tunable laser also includes:

[0118] Blazed gratings, used for wavelength selection, reflect light of a specific wavelength back into the resonant cavity by diffraction;

[0119] The resonant cavity is composed of a first collimating lens, a laser gain chip and a second collimating lens; the photons emitted by the laser gain chip pass through the first collimating lens; the photons passing through the first collimating lens are reflected by the galvanometer to the blazed grating; the blazed grating diffracts according to the wavelength of the incident light; the diffracted photons are reflected by the galvanometer and reflected back into the laser gain chip through the first collimating lens; after the wavelength is selected by the blazed grating, the light of a specific wavelength is gain-amplified in the resonant cavity, and when its intensity exceeds the lasing threshold of the 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 regulating device comprises: a visible light laser and a one-dimensional position detector; the visible light laser is used to emit a laser beam, and is reflected to the one-dimensional position detector through a galvanometer in an external cavity wide spectrum tunable laser; the negative feedback regulating device also comprises: a controller;

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

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

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

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

[0125] A matching module is used to set the target laser wavelength to be output by the resonant cavity, and to search for a matching laser wavelength in a calibration data table, and to obtain a corresponding galvanometer driver operating voltage by matching the obtained laser wavelength;

[0126] A starting module is used to start the external cavity wide spectrum tunable laser, and start the galvanometer driver with the matched galvanometer driver working voltage to rotate the galvanometer, and control the negative feedback regulating device to enter the working state;

[0127] The closed-loop regulation module is used to calculate the real-time spot position through a negative feedback regulation device during the operation of the external cavity wide spectrum tunable laser, and to match the spot position in the calibration data table through the real-time spot position to obtain the corresponding laser wavelength, and to determine the voltage adjustment value by comparing the laser wavelength with the target laser wavelength, and to control the current galvanometer driver working voltage to increase or decrease with the voltage adjustment value, and to repeat this process so that the laser wavelength output by the resonant cavity reaches the target laser wavelength, and after reaching the target laser wavelength, to continuously adjust to keep the wavelength stable within the target laser wavelength or its allowable error range.

[0128] The present invention can monitor and adjust the laser wavelength in real time by using a negative feedback adjustment device, thereby significantly improving the accuracy of wavelength adjustment; the calibration data table ensures the corresponding relationship between the operating voltage of the galvanometer driver and the actual laser wavelength, thereby achieving accurate control of the output wavelength.

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

[0130] In addition, in the present invention, descriptions such as "first", "second", "one", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0131] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0132] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

Claims

1. A closed-loop output wavelength adjustment method based on a negative feedback adjustment device, characterized in that: Applied to external cavity wide spectrum tunable laser; The external cavity wide spectrum tunable laser comprises: a galvanometer, a galvanometer driver for controlling the angle of the galvanometer, 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 comprises: a visible light laser and a one-dimensional position detector; the visible light laser is used to emit a laser beam, and is reflected to the one-dimensional position detector through a galvanometer in an external cavity wide spectrum tunable laser; the output wavelength closed-loop adjustment method comprises: By adjusting the working voltage of the galvanometer driver, the galvanometer angle is changed, thereby changing the position of the light spot formed by the laser beam emitted by the visible light laser after reflection, so that the light spot passes through a plurality of preset position points on the photosensitive area of ​​the one-dimensional position detector in sequence; when the light spot passes through each preset position point, the position of the position point is recorded as the light spot position, the corresponding galvanometer driver working voltage and the laser wavelength output by the resonant cavity at this time, so as to form the calibration data corresponding to the position point, and establish a calibration data table; Set the target laser wavelength to be output by the resonant cavity, and search for the matching laser wavelength in the calibration data table, and obtain the corresponding galvanometer driver operating voltage by matching the obtained laser wavelength; The external cavity wide spectrum tunable laser is started, and the galvanometer driver is started with the matched galvanometer driver working voltage to rotate the galvanometer, and at the same time, the negative feedback regulating device is controlled to enter the working state; During the operation of the external cavity wide spectrum tunable laser, the real-time spot position is calculated by a negative feedback adjustment device, and the real-time spot position is matched with the spot position in the calibration data table to obtain the corresponding laser wavelength. 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, and after reaching the target laser wavelength, continuous adjustment is performed to keep the wavelength stable within the target laser wavelength or its allowable error range.

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

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

4. The closed-loop output wavelength 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 light beam of one party will not be blocked by the optical elements of the other party.

5. The closed-loop output wavelength 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 matched 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 closed-loop output wavelength 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 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 working voltage of the galvanometer driver and the spot position matching the target laser wavelength respectively.

7. The closed-loop output wavelength 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 ; Where I0 is the photocurrent generated at the spot when the laser spot hits the photosensitive area; I L and I R They respectively represent the photocurrents received by the first end electrode and the second end electrode of the one-dimensional position detector; L represents the length of the photosensitive area of ​​the one-dimensional position detector; and x represents the calculated spot position.

8. An output wavelength closed-loop 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 angle of the galvanometer, 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 angle of the galvanometer by adjusting the working voltage of the galvanometer driver, so as to change the spot position formed after the laser beam emitted by the visible light laser is reflected, and make the spot pass 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; A matching module is used to set the target laser wavelength to be output by the resonant cavity, and to search for a matching laser wavelength in a calibration data table, and to obtain a corresponding galvanometer driver operating voltage by matching the obtained laser wavelength; A starting module is used to start the external cavity wide spectrum tunable laser, and start the galvanometer driver with the matched galvanometer driver working voltage to rotate the galvanometer, and control the negative feedback regulating device to enter the working state; The closed-loop regulation module is used to calculate the real-time spot position through a negative feedback regulation device during the operation of the external cavity wide spectrum tunable laser, and to match the spot position in the calibration data table through the real-time spot position to obtain the corresponding laser wavelength, and to determine the voltage adjustment value by comparing the laser wavelength with the target laser wavelength, and to control the current galvanometer driver working voltage to increase or decrease with the voltage adjustment value, and to repeat this process so that the laser wavelength output by the resonant cavity reaches the target laser wavelength, and after reaching the target laser wavelength, to continuously adjust 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 the negative feedback adjustment device according to claim 8, characterized in that: The negative feedback regulating device further comprises: a controller; The one-dimensional position detector is used to generate a photocurrent at the spot when the laser spot hits its photosensitive area, and the electrodes at both ends of the one-dimensional position detector collect the current signal; The controller calculates the light spot position according to the collected current signal; the light spot position 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 the negative feedback adjustment device according to claim 9, characterized in that: The external cavity wide spectrum tunable laser also includes: Blazed gratings, used for wavelength selection, reflect light of a specific wavelength back into the resonant cavity by diffraction; The resonant cavity is composed of a first collimating lens, a laser gain chip and a second collimating lens; the photons emitted by the laser gain chip pass through the first collimating lens; the photons passing through the first collimating lens are reflected by the galvanometer to the blazed grating; the blazed grating diffracts according to the wavelength of the incident light; the diffracted photons are reflected by the galvanometer and reflected back into the laser gain chip through the first collimating lens; after the wavelength is selected by the blazed grating, the light of a specific wavelength is gain-amplified in the resonant cavity, and when its intensity exceeds the lasing threshold of the 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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