A method and system for generating a pulse laser with stable repetition rate environment

Abstract

The application discloses a kind of pulse laser generation method and system of heavy frequency environment stability, it is related to laser technical field.The pulse laser generation system of heavy frequency environment stability proposed in the application includes pump light source and optical resonator, optical resonator includes pump light coupling device, gain device, mode-locking device, coupling output device, optical path compensation module, wherein optical path compensation module utilizes the same material with the sign of temperature coefficient of other parts of optical resonator, under the change of ambient temperature, introduce the sign opposite optical path variation of the optical path variation amount of other parts in optical resonator.The pulse laser generation method of heavy frequency environment stability proposed in the application is used, cavity length compensation module is built and is added to optical resonator, can compensate the pulse laser repetition frequency variation caused by other devices in optical resonator when the change of ambient temperature, with lower cost, simple structure makes the repetition frequency of pulse laser have environmental stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser, in particular to a pulse laser generation method and system with stable repetition frequency in environment. BACKGROUND

[0002] Pulse laser generation is usually achieved by using a pulse laser, and in many application fields of pulse laser, such as microwave frequency measurement and high-frequency microwave signal generation, the stability of the repetition frequency is an important factor affecting the accuracy of frequency measurement and the quality of generated signals.

[0003] The pulse laser is composed of a pump light source and an optical resonator, and the repetition frequency of the pulse laser is mainly affected by the optical path in the optical resonator. For a ring cavity, the repetition frequency is generally the speed of light divided by the optical path in the optical resonator. Since each material constituting the optical resonator has thermal expansion effect and thermo-optic effect, when the ambient temperature changes, the optical path in the optical resonator will change accordingly, resulting in a change in the repetition frequency of the pulse laser.

[0004] The common method for stabilizing the repetition frequency at present is to add a piezoelectric ceramic (PZT) in the optical resonator, and by changing the driving voltage of the PZT to control its stretching length, the length of the optical resonator is affected, so as to control the repetition frequency. However, this method for stabilizing the repetition frequency needs to design a complex feedback control circuit, and needs a driving voltage of more than one hundred volts, which has certain safety hazards.

[0005] The present application can use the proposed pulse laser generation method and system to maintain the optical path in the optical resonator stable when the ambient temperature changes, so as to significantly reduce the influence of the ambient temperature change on the repetition frequency of the pulse laser. SUMMARY

[0006] The present application provides a pulse laser generation method and system with stable repetition frequency in environment.

[0007] The present application provides a pulse laser generation method with stable repetition frequency in environment, comprising the following steps:

[0008] Step 1, building a pulse laser, the pulse laser comprising a pump light source and an optical resonator without optical path compensation module, the optical resonator without optical path compensation module comprising a pump light coupling device, a gain device, a mode locking device and a coupling output device, measuring the positive and negative temperature coefficients of the optical resonator without optical path compensation module;

[0009] Step 2, select a material with a thermal expansion coefficient same in sign as the temperature coefficient of the optical resonant cavity without the optical path compensation module as the driving material, fix one end of the spatial optical path part in the optical path compensation module at fixed point 1, connect the other end to one end of the driving material in the optical path compensation module, fix the other end of the driving material at fixed point 2, keep the distance between fixed point 1 and fixed point 2 unchanged, the driving material has the same sign of temperature coefficient as other parts of the optical resonant cavity, when the temperature changes, the change in the length of the driving material causes the optical path in the spatial optical path in the compensation module to change in the opposite direction, compensating for the change in the optical path of other parts of the optical resonant cavity;

[0010] Step 3, connect the optical path compensation module to the optical resonant cavity, when the ambient temperature changes, the pulse laser output by the pulse laser with the optical path compensation module added has improved pulse laser repetition frequency stability.

[0011] In one example, in step 1, the temperature coefficient of the optical resonant cavity without the optical path compensation module is the total optical path change when the ambient temperature changes by one unit.

[0012] In one example, in step 2, the optical path compensation module is divided into a transmission type compensation module and a reflection type compensation module. The transmission type compensation module is as shown in Figure 2 , where 1 is fixed point 1, 2 is fixed point 2, 3 is the driving material, 4 is the fiber collimator 1, 5 is the fiber collimator 2, the fiber collimator 1 and the fiber collimator 2 form a spatial optical path, the fiber collimator 2 is fixed at fixed point 1, the fiber collimator 1 is connected to one end of the driving material, and the other end of the driving material is fixed at fixed point 2; the reflection type compensation module is as shown in Figure 3 , where 1 is fixed point 1, 2 is fixed point 2, 3 is the driving material, 4 is the fiber collimator 3, 5 is the mirror, the fiber collimator 3 and the mirror form a spatial optical path, the mirror is fixed at fixed point 1, the fiber collimator 3 is connected to one end of the driving material, and the other end of the driving material is fixed at fixed point 2.

[0013] In one example, in step 2, the optical path compensation module uses a spatial optical path to change the spatial position of the fiber collimator through the thermal expansion effect of the driving material when the ambient temperature changes, thereby affecting the distance between the fiber collimators 1 and 2 in the transmission type compensation module or the distance between the fiber collimator 3 and the mirror in the reflection type compensation module, using a driving material with a thermal expansion coefficient same in sign as the temperature coefficient of the optical resonant cavity without the optical path compensation module, when the ambient temperature changes, introducing an optical path change opposite to the optical path change of the optical resonant cavity without the optical path compensation module.

[0014] The present application provides a pulse laser generation system with stable repetition frequency in an environment, comprising:

[0015] The pump light source and the optical resonant cavity, the optical resonant cavity includes a pump light coupling device, a gain device, a mode locking device, a coupling output device, an optical path compensation module; the optical signal in the optical resonant cavity passes through the spatial light path part in the optical path compensation module, one end of the spatial light path part is fixed at fixed point 1, the other end is connected with one end of the driving material in the optical path compensation module, the other end of the driving material is fixed at fixed point 2, the distance between fixed point 1 and fixed point 2 remains unchanged, the driving material has the same temperature coefficient sign as other parts of the optical resonant cavity, when the temperature changes, the change of the length of the driving material causes the optical path of the spatial light path in the compensation module to change reversely, and the optical path changes of other parts of the optical resonant cavity are compensated.

[0016] In one example, the pump light source shown is a semiconductor light source, a dye light source, a solid light source, a gas light source.

[0017] In one example, the pump light coupling device shown is a dichroic mirror, a thin film with the characteristics of a dichroic mirror, an optical wavelength division multiplexing device.

[0018] In one example, the optical resonant cavity shown is a fiber cavity composed of optical fibers and optical fiber devices or a spatial cavity composed of spatial light paths and spatial light devices such as mirrors, and the cavity type structure is a ring cavity, a linear cavity, an "8" cavity, and a "9" cavity.

[0019] In one example, the mode locking device shown is a material or structure with a saturable absorption effect, including carbon nanotubes, black phosphorus, graphene, two-dimensional materials, semiconductor saturable absorption mirrors, photonic crystal devices, and nonlinear fiber ring mirrors.

[0020] In one example, the optical path compensation module shown does not require the repetition frequency of the pulsed laser as a control signal, nor does it require a complex feedback control system, but directly uses its own thermal expansion effect and thermo-optic effect to compensate for the optical path in the optical resonant cavity.

[0021] In one example, the coupling output device shown has one input end and two output ends, divides the input light into two paths, and is a beam splitter, an optical coupler, an optical wavelength division multiplexing device, an optical polarization beam splitter, and an optical polarization beam splitting prism.

[0022] The present application proposes a pulse laser generation method and system with stable repetition frequency in the environment. The system and the implementation method have the following practical application significance:

[0023] 1. The present application solves the problem of pulse laser repetition frequency fluctuation when the environmental temperature changes. When the environmental temperature changes, due to the thermal expansion effect and thermo-optic effect of each device in the optical resonant cavity, the optical path in the optical resonant cavity will change, resulting in a change in the repetition frequency of the pulsed laser, which will have a negative impact on the quality of the microwave signal generation and the frequency measurement accuracy of the microwave signal.

[0024] 2. The pulse laser generation method with stable repetition frequency in the environment has the characteristics of simple structure and easy implementation, does not need a complex feedback control system, and does not need to dynamically adjust parameters, and has low implementation difficulty.

[0025] 3. The pulse laser generation system with stable repetition frequency in the environment does not contain a high-voltage driving circuit, has the characteristics of low power consumption and high safety, and has the advantages of a large working temperature range and low cost compared with the method of adjusting the cavity length by using a PZT. BRIEF DESCRIPTION OF DRAWINGS

[0026] The application will be further described in detail below in combination with the drawings, in which:

[0027] Figure 1 is a system schematic diagram of the pulse laser generation method with stable repetition frequency in the environment. Wherein 1 is a pump light source, 2 is a pump light coupling device, 3 is a gain device, 4 is a mode-locked device, 5 is a coupling output device, and 6 is an optical path compensation module.

[0028] Figure 2 is a structure schematic diagram of a transmission type compensation module, wherein 1 is a fixed point 1, 2 is a fixed point 2, 3 is a driving material, 4 is a fiber collimator 1, and 5 is a fiber collimator 2.

[0029] Figure 3 is a structure schematic diagram of a reflection type compensation module, wherein 1 is a fixed point 1, 2 is a fixed point 2, 3 is a driving material, 4 is a fiber collimator 3, and 5 is a mirror.

[0030] Figure 4 is a system structure diagram of the pulse laser generation system with stable repetition frequency in the environment in Example 1. Wherein 1 is a semiconductor laser as a pump light source, 2 is a wavelength division multiplexer and optical isolator two-in-one device as a pump light coupling device, 3 is an erbium-doped fiber as a gain device, 4 is a carbon nanotube as a mode-locked device, 5 is an optical coupler as a coupling output device, and 6 is an optical path compensation module.

[0031] Figure 5 is a structure design of a transmission type compensation module, wherein 1 is a driving material, 2 is a fiber collimating lens 1, and 3 is a fiber collimating lens 2.

[0032] Figure 6 is a repetition frequency of pulse laser before and after installation of the optical path compensation module in Example 1 changes with the environment temperature.

[0033] Figure 7is the system structure diagram of the pulse laser generation system with stable repetition frequency in the environment of example two. Wherein 1 is a semiconductor saturable absorber mirror as a mode locker, 2 is a semiconductor laser as a pump light source, 3 is an optical wavelength division multiplexer as a pump light coupling device, 4 is an erbium-doped fiber as a gain device, 5 is an optical coupler as a coupling output device, and 6 is an optical path compensation module.

[0034] Figure 8 is the structure design of the reflective compensation module, wherein 1 is a driving material, 2 is a fiber collimating lens 3, and 3 is a mirror.

[0035] Figure 9 is the repetition frequency of the pulse laser before and after the installation of the optical path compensation module in example two changes with the ambient temperature. DETAILED DESCRIPTION

[0036] Example 1

[0037] The system structure diagram of the embodiment is shown in Figure 4

[0038] The pump light source in the embodiment is a semiconductor laser.

[0039] The optical resonant cavity type in the embodiment is a ring cavity.

[0040] The pump light coupling device in the embodiment is an optical wavelength division multiplexer and optical isolator two-in-one device.

[0041] The gain device in the embodiment is an erbium-doped fiber.

[0042] The mode locker in the embodiment is a carbon nanotube.

[0043] The coupling output device in the embodiment is an optical coupler.

[0044] The optical path compensation module in the embodiment is shown in Figure 5 , wherein 1 is a driving material, 2 is a fiber collimating lens 1, and 3 is a fiber collimating lens 2. The spatial light path composed of the fiber collimating lenses 1 and 2 and the air therebetween is located in the optical resonant cavity. The fiber collimating lens 2 is fixed at a fixed point 1, the fiber collimating lens 1 is connected with one end of the driving material, and the other end of the driving material is fixed at a fixed point 2. The distance between the fixed point 1 and the fixed point 2 remains unchanged. Through the thermal expansion effect of the driving material, the spatial position of the fiber collimating lens is changed when the ambient temperature changes, thereby affecting the distance between the fiber collimating lenses 1 and 2 in the transmission compensation module.

[0045] In the embodiment, the optical resonant cavity without the optical path compensation module is composed of optical fibers and optical fiber devices. The thermal expansion coefficient and the thermal light coefficient of the optical fibers are both greater than zero, and the temperature coefficient of the optical resonant cavity without the optical path compensation module is positive. ​

[0046] In this embodiment, the organic glass with the same positive thermal expansion coefficient is selected as the driving material, the length of the driving material is 0.12m, and the transmission compensation module is built as the optical path compensation module according to the structure shown in Figure 5

[0047] The built optical path compensation module is connected to the optical resonant cavity. The pulse laser repetition frequency changes with temperature before and after the installation of the optical path compensation module as shown in Figure 6 Compared with the system without using this technology, the stability of the pulse laser repetition frequency can be significantly improved.

[0048] Example 2

[0049] The system structure diagram of this embodiment is shown in Figure 7

[0050] The pump light source in this embodiment is a semiconductor laser.

[0051] The optical resonant cavity type in this embodiment is a linear cavity.

[0052] The pump light coupling device in this embodiment is an optical wavelength division multiplexer.

[0053] The gain device in this embodiment is an erbium-doped optical fiber.

[0054] The mode-locked device in this embodiment is a semiconductor saturable absorber mirror.

[0055] The coupling output device in this embodiment is an optical coupler.

[0056] The optical path compensation module in this embodiment is shown in Figure 8 , wherein 1 is the driving material, 2 is the optical fiber collimating lens 3, and 3 is the mirror. The spatial light path composed of the optical fiber collimating lens 3, the mirror and the air in between is located in the optical resonant cavity, the mirror is fixed at the fixed point 1, the optical fiber collimating lens 3 is connected to one end of the driving material, the other end of the driving material is fixed at the fixed point 2, and the distance between the fixed point 1 and the fixed point 2 remains unchanged.

[0057] In this embodiment, the optical resonant cavity without the optical path compensation module is composed of optical fibers and optical fiber devices, the thermal expansion coefficient and the thermal light coefficient of the optical fibers are both greater than zero, and the temperature coefficient of the optical resonant cavity without the optical path compensation module is positive.

[0058] In this embodiment, the nylon with the same positive thermal expansion coefficient is selected as the driving material, the length of the driving material is 0.1m, and the reflection compensation module is built as the optical path compensation module according to the structure shown in Figure 8

[0059] ​​​The built optical path compensation module is connected to the optical resonant cavity. The repetition frequency of the pulse laser before and after the installation of the optical path compensation module changes with temperature as shown in Figure 9 Compared with the system without using this technology, the stability of the repetition frequency of the pulse laser can be significantly improved.

[0060] The above only describes the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can make appropriate changes or variations within the technical scope disclosed by the present application, and such changes or variations shall be covered within the protection scope of the present application.

Claims

1. A method for generating a pulse laser with a stable repetition rate, the method comprising: generating a pulse laser with a repetition rate; and adjusting the repetition rate of the pulse laser to a target repetition rate. The specific steps are as follows: Step 1, build a pulse laser, the pulse laser includes a pump light source and an optical resonant cavity without an optical path compensation module, the optical resonant cavity without the optical path compensation module includes a pump light coupling device, a gain device, a mode locking device and a coupling output device, and the positive and negative temperature coefficients of the optical resonant cavity without the optical path compensation module are measured; Step 2, the optical path compensation module is divided into a transmission type compensation module and a reflection type compensation module; the transmission type compensation module includes a driving material, a first optical fiber collimator and a second optical fiber collimator, wherein the first optical fiber collimator and the second optical fiber collimator constitute a spatial light path, the second optical fiber collimator is fixed at a first fixed point, one end of the first optical fiber collimator is connected with the driving material, and the other end of the driving material is fixed at a second fixed point; the reflection type compensation module includes a driving material, a third optical fiber collimator and a mirror, wherein the third optical fiber collimator and the mirror constitute a spatial light path, the mirror is fixed at the first fixed point, one end of the third optical fiber collimator is connected with the driving material, and the other end of the driving material is fixed at the second fixed point, and the distance between the first fixed point and the second fixed point remains unchanged; The optical path compensation module uses a spatial light path, changes the spatial position of the optical fiber collimator through the thermal expansion effect of the driving material when the ambient temperature changes, and then affects the distance between the first optical fiber collimator and the second optical fiber collimator in the transmission type compensation module or the distance between the third optical fiber collimator and the mirror in the reflection type compensation module; the driving material with the same sign of the thermal expansion coefficient as the temperature coefficient of the optical resonant cavity without the optical path compensation module is used, and when the ambient temperature changes, an optical path change opposite to the optical path change of the optical resonant cavity without the optical path compensation module is introduced; Step 3, connect the optical path compensation module to the optical resonant cavity, and when the ambient temperature changes, the pulse laser output by the pulse laser with the optical path compensation module added has improved pulse laser repetition frequency stability.

2. The method of claim 1, wherein the repetition rate environment stabilized pulsed laser generation method is characterized by, The temperature coefficient of the optical resonant cavity without the optical path compensation module is the total optical path change in the optical resonant cavity without the optical path compensation module when the ambient temperature changes by one unit.

3. The method of claim 1, wherein the repetition rate environment stabilized pulsed laser generation method is characterized by, The optical resonant cavity is a ring cavity, a linear cavity, an "8" cavity or a "9" cavity.

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