Laser power stabilization system and laser device

Abstract

The application relates to a laser power stabilizing system and a laser device, which comprises a light splitting input end, a light splitting input light path used for connecting one output end of a light splitter arranged on an output light path of a laser; a photodiode, a light sensing part of the photodiode being connected to the light splitting input end so as to adjust a current passing through the photodiode according to light entering the light splitting input end; a temperature control device, the photodiode being arranged in the temperature control device; and an operational amplifier circuit, the operational amplifier circuit being connected to the photodiode so as to collect the current passing through the photodiode and convert the current into a voltage signal; and an output end of the operational amplifier circuit being used for connecting a controller so as to feed back the voltage signal to the controller, so that the controller controls the laser according to the voltage signal. The temperature control device controls the temperature around the photodiode, so as to reduce the influence of the surrounding environment, especially the temperature, on the photodiode, improve the accuracy of the output voltage signal, and further improve the power stability of the laser.

Description

Technical Field

[0001] This application relates to the field of laser technology, and in particular to a laser power stabilization system and laser equipment. Background Technology

[0002] In recent years, with the development of fiber optic devices, the optical performance of lasers has been continuously improved, and their integration level has become increasingly higher, making them irreplaceable in fields such as fiber optic communication, precision measurement, and lidar. Periodically polarized lithium niobate (PPLN) waveguides are nonlinear optical crystals. They can generate sum-frequency and difference-frequency effects using nonlinear second harmonics. With innovations and breakthroughs in lithium niobate thin-film ridge waveguide technology, the conversion efficiency of sum-frequency and difference-frequency has been significantly improved. Therefore, PPLN ridge waveguides are widely used in single-frequency lasers, expanding the operating wavelength range of lasers, such as special wavelengths like 532nm and 780nm, making them very important for applications in atomic and molecular science research, biomedicine, and quantum detection.

[0003] Since the stability of laser power affects the signal-to-noise ratio of the probe signal, the stability of laser power has become a major concern. Generally, feedback is obtained by probing the optical signal and the laser is controlled by a PID algorithm to achieve power stability. However, in practical engineering applications, the probe optical signal is affected by the environment and will generate some noise, which will affect the accuracy of laser stability control.

[0004] Therefore, how to provide an improved system for stabilizing optical signals to reduce optical signal detection noise and improve laser power stability has become an urgent problem to be solved. Utility Model Content

[0005] In view of this, embodiments of this application provide a laser power stabilization system and a laser device to solve the problem of how to provide an improved stabilization system for detecting optical signals, so as to reduce optical signal detection noise and improve laser power stability.

[0006] In a first aspect, this application provides a laser power stabilization system, including a beam splitting input terminal, wherein the beam splitting input optical path is used to connect to an output terminal of a beam splitter disposed on the output optical path of the laser;

[0007] A photodiode, wherein the photosensitive portion of the photodiode is connected to the beam splitting input terminal, so as to adjust the current passing through the photodiode according to the light entering the beam splitting input terminal;

[0008] Temperature control device, wherein the photodiode is disposed in the temperature control device; and

[0009] An operational amplifier circuit is provided, wherein the operational amplifier circuit is connected to the photodiode for sampling, so as to collect the current passing through the photodiode and convert the current into a voltage signal;

[0010] The output of the operational amplifier circuit is used to connect to the controller to feed back the voltage signal to the controller, so that the controller controls the laser according to the voltage signal.

[0011] In one embodiment, the temperature control device includes a temperature sensor and a temperature control equipment. The temperature control equipment is equipped with the photodiode to control the ambient temperature of the photodiode. The temperature sensor is located around the photodiode to collect the ambient temperature of the photodiode.

[0012] In one embodiment, the temperature control device includes at least two copper plates, one of which is provided with a first semiconductor cooling chip, and the photodiode is disposed on the copper plate provided with the first semiconductor cooling chip, and the photodiode is covered by another copper plate.

[0013] In one embodiment, each thermoelectric cooler is connected to the controller to control the temperature of the temperature control device according to the control instructions of the controller, and the temperature sensor is connected to the controller to send the collected temperature to the controller.

[0014] In one embodiment, the temperature sensor is a thermistor temperature sensor.

[0015] In one embodiment, a sampling circuit is further included, the sampling circuit employing a shielded twisted-pair cable, and the operational amplifier circuit is connected to the photodiode through the sampling circuit.

[0016] In one embodiment, the operational amplifier circuit is an operational amplifier zero-bias circuit or an operational amplifier plus-bias circuit.

[0017] In a second aspect, this application provides a laser device, the laser device including a laser, a beam splitter, a controller connected to the laser, and a laser power stabilization system as described in the first aspect and its improvements, the laser power stabilization system being connected to the laser, the beam splitter, and the controller.

[0018] In one embodiment, the system further includes a seed source and a waveguide, wherein the seed source, the laser, the waveguide, and the beam splitter are connected sequentially in the direction of light propagation.

[0019] In one embodiment, the controller includes an ADC circuit, an FPGA circuit, and a DAC circuit. One end of the ADC circuit is connected to one end of the FPGA circuit, and the other end of the ADC circuit is connected to the output terminal of the operational amplifier circuit. The other end of the FPGA circuit is connected to one end of the DAC circuit, and the other end of the DAC circuit is connected to the laser and the temperature control device.

[0020] The advantages of this application compared to the prior art are as follows: The system of this application includes a beam splitting input terminal, the beam splitting input optical path being used to connect to an output terminal of a beam splitter disposed on the output optical path of a laser; a photodiode, the photosensitive portion of which is connected to the beam splitting input terminal to adjust the current passing through the photodiode according to the light entering through the beam splitting input terminal; a temperature control device, the photodiode being disposed in the temperature control device; and an operational amplifier circuit, the operational amplifier circuit being connected to the photodiode to collect the current passing through the photodiode and convert the current into a voltage signal; the output terminal of the operational amplifier circuit is used to connect to a controller to feed the voltage signal back to the controller, so that the controller controls the laser according to the voltage signal. By controlling the temperature around the photodiode through the temperature control device, the influence of the surrounding environment, especially temperature, on the photodiode is reduced, the accuracy of the output voltage signal is improved, and thus the power stability of the laser is improved. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the structure of a laser device provided in one embodiment of this application;

[0023] Figure 2 This is a schematic diagram of the structure of an operational amplifier zero-bias circuit provided in an embodiment of this application. Detailed Implementation

[0024] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0025] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0026] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0027] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if detected [the described condition or event]" may be interpreted, depending on the context, as meaning "once determined," "in response to determination," "once detected [the described condition or event]," or "in response to detection [the described condition or event]."

[0028] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0029] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0030] To illustrate the technical solution of this application, specific embodiments are described below.

[0031] This application provides a laser device, which includes a laser, a beam splitter, a controller connected to the laser, and a laser power stabilization system, wherein the laser power stabilization system is connected to the laser, the beam splitter, and the controller.

[0032] The laser power stabilization system includes a beam splitter input terminal, a photodiode, a temperature control device, and an operational amplifier circuit. The beam splitter input optical path is used to connect to one output terminal of the beam splitter located on the output optical path of the laser. The photosensitive part of the photodiode is connected to the beam splitter input terminal to adjust the current passing through the photodiode according to the light entering the beam splitter input terminal. The photodiode is located in the temperature control device. The operational amplifier circuit is connected to the photodiode to collect the current passing through the photodiode and convert the current into a voltage signal. The output terminal of the operational amplifier circuit is used to connect to the controller to feed the voltage signal back to the controller, so that the controller controls the laser according to the voltage signal.

[0033] By controlling the temperature around the photodiode using a temperature control device, the influence of the surrounding environment, especially temperature, on the photodiode can be reduced, thereby improving the accuracy of the output voltage signal and ultimately enhancing the power stability of the laser.

[0034] like Figure 1 The diagram shown is a structural schematic of a laser device provided in this application. The laser device also includes a seed source and a waveguide. The seed source, laser, waveguide, and beam splitter are connected in sequence in the direction of light propagation. The controller includes an ADC circuit, an FPGA circuit, and a DAC circuit. One end of the ADC circuit is connected to one end of the FPGA circuit, and the other end of the ADC circuit is connected to the output of the operational amplifier circuit. The other end of the FPGA circuit is connected to one end of the DAC circuit, and the other end of the DAC circuit is connected to the laser and the temperature control device.

[0035] The optical path begins with the seed source, and its output optical signal is amplified by the laser and then connected to the waveguide. The waveguide output is divided into two parts: the main optical path serves as the output, and the other small part serves as feedback to the photodiode, which is placed on a temperature control device.

[0036] In one embodiment, the temperature control device includes a temperature sensor and a temperature control unit. A photodiode is disposed on the temperature control unit to control the ambient temperature of the photodiode. The temperature sensor is disposed around the photodiode to collect the ambient temperature. By detecting the ambient temperature using the temperature sensor, the temperature control unit can be accurately controlled based on the ambient temperature, for example, maintaining the ambient temperature at approximately 25°C.

[0037] In one embodiment, the temperature sensor is a thermistor temperature coefficient (NTC) sensor, which can reduce the overall size of the device and accurately collect temperature information.

[0038] In one embodiment, the temperature control device includes at least two copper plates. A thermoelectric cooler (TEC) is disposed on one of the copper plates, and a photodiode is disposed on the copper plate with the first TEC. The photodiode is covered by another copper plate. By placing the photodiode on one copper plate and covering its upper part with a copper plate, heat conduction is achieved, ensuring temperature uniformity across the entire photodiode. Finally, the TEC controls the temperature of this copper plate, ensuring a consistent temperature within the operating temperature range. For example, the TEC maintains a constant temperature of 25°C within the operating temperature range, thus ensuring that the photodiode's responsivity does not change with ambient temperature variations.

[0039] In one embodiment, each thermoelectric cooler is connected to a controller to control the temperature of the temperature control device according to the controller's control commands. A temperature sensor is connected to the controller to send the collected temperature data to the controller. The controller that controls the laser can be connected to the temperature control device for temperature control; alternatively, the temperature control device can be controlled by an independent controller.

[0040] In one embodiment, a sampling circuit is also included. The sampling circuit uses shielded twisted-pair cable, and the operational amplifier circuit is connected to the photodiode through the sampling circuit. Since the current generated by the photodiode is a small signal, even slight external interference can cause a significant change in the output optical power. Therefore, using shielded twisted-pair cable can minimize EMC interference.

[0041] In one embodiment, the operational amplifier circuit is either a zero-bias operational amplifier circuit or an over-bias operational amplifier circuit. Figure 2 shows a schematic diagram of the zero-bias operational amplifier circuit provided in this embodiment, which is an operational amplifier chip and its components used for converting the current of a photodiode to voltage and amplifying the voltage. The photodiode is a current-type device, requiring the conversion of the current signal into a detectable voltage signal, and amplification of the small signal. The operational amplifier chip itself has a certain amount of noise; therefore, a low-noise chip model is selected here. A low-noise operational amplifier chip refers to an amplifier with extremely low internal noise levels, typically a few nV / Hz. Its purpose is to minimize the additional noise introduced by itself when amplifying weak current or voltage signals.

[0042] Figure 2 illustrates a complete signal transmission path: the photodiode current signal flows through a feedback resistor, is converted into a voltage by a low-noise operational amplifier (LNP), amplified, and then converted into a digital signal by an ADC and output to a digital processor. The LNP and precision resistors ensure the accuracy of signal conversion and amplification, while the ADC performs a high-fidelity conversion from analog to digital.

[0043] In addition, photodiodes generally have two driving methods: biased and zero biased. When using the biased method, the photodiode has a fast response speed but high noise, while the zero biased method sacrifices the response speed but has low system noise. The zero biased method is the preferred option for frequency conversion lasers with a closed-loop response speed of several hundred Hz.

[0044] The laser mentioned above can be a pump laser, and the waveguide can be a ridge waveguide such as a PPLN.

[0045] The output of the photodiode is amplified by a shielded twisted-pair cable connected to a zero-bias operational amplifier circuit. The signal is then processed by an FPGA. The FPGA runs a PID algorithm to calculate the difference between the signal sampled by the ADC and the actual value that needs to be achieved. Finally, the output optical power is stabilized by controlling the pump laser current through a DAC.

[0046] This application employs precise temperature control of the photodiode to ensure that the output optical power does not change significantly when the ambient temperature changes. Furthermore, it uses shielded twisted-pair cables to minimize external interference, and employs low-noise operational amplifiers and matching zero-bias circuits to minimize the circuit's own noise and improve the stability of the output power.

[0047] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A laser power stabilization system, characterized in that, Includes a beam splitting input terminal, wherein the optical path of the beam splitting input terminal is used to connect to one output terminal of a beam splitter disposed on the output optical path of the laser; A photodiode, wherein the photosensitive portion of the photodiode is connected to the beam splitting input terminal, so as to adjust the current passing through the photodiode according to the light entering the beam splitting input terminal; A temperature control device, wherein the photodiode is disposed in the temperature control device; as well as An operational amplifier circuit is provided, wherein the operational amplifier circuit is connected to the photodiode for sampling, so as to collect the current passing through the photodiode and convert the current into a voltage signal; The output of the operational amplifier circuit is used to connect to the controller to feed back the voltage signal to the controller, so that the controller controls the laser according to the voltage signal.

2. The laser power stabilization system according to claim 1, characterized in that, The temperature control device includes a temperature sensor and a temperature control equipment. The temperature control equipment is equipped with the photodiode to control the ambient temperature of the photodiode. The temperature sensor is located around the photodiode to collect the ambient temperature of the photodiode.

3. The laser power stabilization system according to claim 2, characterized in that, The temperature control device includes at least two copper plates, one of which is provided with a first semiconductor cooling chip, and the photodiode is disposed on the copper plate provided with the first semiconductor cooling chip, and the photodiode is covered by another copper plate.

4. The laser power stabilization system according to claim 3, characterized in that, Each thermoelectric cooler is connected to the controller to control the temperature of the temperature control device according to the controller's control instructions. The temperature sensor is connected to the controller to send the collected temperature to the controller.

5. The laser power stabilization system according to claim 2, characterized in that, The temperature sensor is a thermistor temperature sensor.

6. The laser power stabilization system according to claim 1, characterized in that, It also includes a sampling circuit, which uses a shielded twisted-pair cable, and the operational amplifier circuit is connected to the photodiode through the sampling circuit.

7. The laser power stabilization system according to any one of claims 1 to 6, characterized in that, The operational amplifier circuit is either a zero-bias operational amplifier circuit or an over-bias operational amplifier circuit.

8. A laser device, characterized in that, The laser device includes a laser, a beam splitter, a controller connected to the laser, and a laser power stabilization system as described in any one of claims 1 to 6, wherein the laser power stabilization system is connected to the laser, the beam splitter, and the controller.

9. The laser device according to claim 8, characterized in that, It also includes a seed source and a waveguide, wherein the seed source, the laser, the waveguide and the beam splitter are connected in sequence in the direction of light propagation.

10. The laser device according to claim 8 or 9, characterized in that, The controller includes an ADC circuit, an FPGA circuit, and a DAC circuit. One end of the ADC circuit is connected to one end of the FPGA circuit, and the other end of the ADC circuit is connected to the output terminal of the operational amplifier circuit. The other end of the FPGA circuit is connected to one end of the DAC circuit, and the other end of the DAC circuit is connected to the laser and the temperature control device.

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