A saturable absorber testing system and testing method

Abstract

This invention relates to the field of laser optical device technology, and more particularly to a saturable absorber testing system and method, comprising: a laser for emitting pulsed light signals of a specific wavelength; an optical amplifier for receiving and amplifying the pulsed light signals emitted by the laser; an adjustable attenuator including a half-glass plate and a polarization beam splitter; wherein the half-glass plate is used to change the polarization direction of the incident linearly polarized light, so that the amplified light signal input to the adjustable attenuator undergoes a specific degree of adjustable attenuation when passing through the polarization beam splitter; a sample placement device for placing the saturable absorber sample to be tested; an optical power meter for measuring the optical power intensity of the light signal before and after passing through the sample; and a signal processing unit for data processing to obtain the nonlinear transmission curve of the saturable absorber sample. This invention optimizes the optical path structure of traditional testing systems and effectively reduces the influence of dispersion in the test optical path on the measurement results.

Description

Technical Field

[0001] This invention relates to the field of laser optical device technology, and in particular to a saturable absorber testing system and testing method. Background Technology

[0002] A saturable absorber is an optical material with nonlinear absorption characteristics, where its absorption intensity varies with light intensity. Specifically, it exhibits high absorption capacity at lower light intensities, while its absorption capacity decreases or even approaches saturation at higher light intensities. This nonlinear absorption characteristic makes saturable absorbers widely applicable in fields such as laser technology, optical communication, and ultrafast optics.

[0003] Saturable absorbers are the most commonly used passive mode-locking elements in lasers. During normal laser operation, they help achieve longitudinal mode phase synchronization within the laser cavity through nonlinear absorption, generating ultrashort pulse lasers. This nonlinear absorption characteristic directly determines the output pulse characteristics of the mode-locked laser. Therefore, selecting a saturable absorber material with suitable performance parameters is extremely important for achieving stable mode-locking of the laser.

[0004] Currently, the most commonly used method for measuring the nonlinear transmission curves of saturable absorbers is the dual-channel balancing method, also known as the dual-channel intensity scanning method. This widely adopted method requires splitting the light signal emitted by the laser source into two paths via a coupling device, one through the saturable absorber sample and the other through a reference blank control group (e.g., CN109861062A). However, the power of the signal light emitted by the laser cannot be fully utilized to excite the nonlinear characteristics of the sample under test, thus failing to accurately characterize the key parameters of the saturable absorber. Furthermore, in the traditional dual-channel balancing method, the total fiber length is relatively large, and the coupling ratio of the coupled optical path fluctuates with changes in incident light power during continuous attenuation adjustment, ultimately affecting the accuracy of the measurement results. Summary of the Invention

[0005] The purpose of this invention is to provide a reliable saturable absorber testing system and method, which improves the problems of poor measurement accuracy caused by the long total length of optical fiber and the complex optical path structure in the existing technology.

[0006] To achieve the above objectives, the present invention provides a saturable absorber testing system, comprising:

[0007] A laser is used to emit pulsed light signals of a specific wavelength.

[0008] An optical amplifier is used to receive and amplify the pulsed optical signal emitted by a laser, so that the optical power of the amplified optical signal output by the optical amplifier meets the preset power standard.

[0009] An adjustable attenuator includes a half-wave plate and a polarizing beam splitter. The half-wave plate is used to change the polarization direction of the incident ray polarized light, so that the amplified light signal input to the adjustable attenuator undergoes a specific degree of adjustable attenuation when it passes through the polarizing beam splitter. The polarizing beam splitter is used to split the incident laser into a probe beam and a reference beam, and the splitting ratio is dynamically adjusted by rotating the half-wave plate.

[0010] A sample placement device for placing a saturable absorber sample to be tested;

[0011] An optical power meter is used to measure the optical power intensity of a light signal before and after it passes through the sample under test in a path.

[0012] The signal processing unit is used to process the two sets of optical power values ​​measured by the optical power meter to obtain the power intensity of the probe light and its transmittance through the saturable absorber sample, and to plot the nonlinear transmission curve of the saturable absorber sample accordingly.

[0013] In some embodiments of this application, the laser is a femtosecond laser source, wherein the wavelength of the femtosecond laser source is one of 1550nm, 1300nm, and 1060nm;

[0014] The laser is a polarization-maintaining output, and the output beam is a highly linearly polarized laser.

[0015] In some embodiments of this application, the laser is connected to the sample placement device via an optical amplifier and an adjustable attenuator.

[0016] In some embodiments of this application, the half-wave plate is an achromatic glass plate and is mounted in a high-precision rotary mounting base using a threaded adapter;

[0017] The polarization beam splitter uses a Glan laser polarizer with an antireflection coating and is mounted in a high-precision rotary mount.

[0018] In some embodiments of this application, the optical power meter includes: a first optical power meter and a second optical power meter; wherein, the first optical power meter is used to measure the optical power of the laser reflected from the side window of the polarization beam splitter, and the second optical power meter is used to measure the optical power of the laser after the probe light passes through the saturable absorber.

[0019] In some embodiments of this application, a saturable absorber testing method for a saturable absorber testing system is also disclosed, comprising:

[0020] Step 1: Rotate the half-wave plate to change its optical axis direction, so that the incident laser signal undergoes adjustable attenuation to different degrees when it passes through the polarization beam splitter. The polarization beam splitter is used to split the incident laser into two parts: reflected light and transmitted light.

[0021] Step 2: The transmitted light is used as the probe light for subsequent tests, and the reflected light is used as the reference light for subsequent tests, completing a full performance evaluation of the saturable absorber. The specific process is as follows: During the attenuation change of the adjustable attenuator from high to low, the laser power reflected by the polarization beam splitter is recorded in real time using a first optical power meter to obtain a set of reference optical power data. At the same time, a second optical power meter is used to synchronously measure the optical power of the probe light after passing through the saturable absorber sample under test, forming a set of probe-received optical power data. Based on the linear change relationship between the power intensity of the reflected light and the probe light, the probe input optical power value under the corresponding attenuation condition can be calculated based on the reference optical power data. At the same time, the ratio of the calculated probe input optical power value to the probe-received optical power is defined as the transmittance of the saturable absorber sample under the same attenuation level. Based on different attenuation conditions, the corresponding probe-received optical power and its corresponding sample transmittance are calculated one by one, and finally, the nonlinear transmission curve of the sample under test is plotted.

[0022] The advantages and beneficial effects of this invention are:

[0023] 1. The optical signal emitted by the laser used in this invention is no longer split into two paths by a coupler. Instead, a more precise and concise control method is employed: a combined optical system of a half-wave plate and a polarizing beam splitter is integrated into the adjustable attenuator section. This invention combines the "splitting" process with the adjustable attenuator, which not only optimizes the overall structure of the optical path but also solves the problem in traditional testing methods where the coupling ratio of the coupling device fluctuates with the increase of incident light intensity, ultimately affecting the test results.

[0024] 2. The adjustable attenuator section adopts a spatial optical path structure, which greatly shortens the total length of the optical fiber in the saturable absorber test system and effectively reduces the influence of the dispersion effect of the optical fiber medium on the measurement results of the saturable absorption characteristics.

[0025] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0026] Figure 1 This is a structural block diagram of a saturable absorber testing system according to an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the device connection of a saturable absorber testing system according to an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram illustrating the working principle of an adjustable attenuator composed of a half-wave plate and a Glan polarizer in an embodiment of the present invention. Detailed Implementation

[0029] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. These terms are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0030] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0031] like Figure 1 As shown, the present invention provides a saturable absorber testing system, comprising:

[0032] A laser is used to emit pulsed light signals of a specific wavelength.

[0033] An optical amplifier is used to receive and amplify the pulsed optical signal emitted by a laser, so that the optical power of the amplified optical signal output by the optical amplifier meets the preset power standard.

[0034] An adjustable attenuator includes a half-wave plate and a polarizing beam splitter. The half-wave plate is used to change the polarization direction of the incident ray polarized light, so that the amplified light signal input to the adjustable attenuator undergoes a specific degree of adjustable attenuation when it passes through the polarizing beam splitter. The polarizing beam splitter is used to split the incident laser into a probe beam and a reference beam, and the splitting ratio is dynamically adjusted by rotating the half-wave plate.

[0035] A sample placement device for placing a saturable absorber sample to be tested;

[0036] An optical power meter is used to measure the optical power intensity of a light signal before and after it passes through the sample under test in a path.

[0037] The signal processing unit is used to process the two sets of optical power values ​​measured by the optical power meter to obtain the power intensity of the probe light and its transmittance through the saturable absorber sample, and to plot the nonlinear transmission curve of the saturable absorber sample accordingly.

[0038] It's important to understand that in the optical transmission path, a coupling device is no longer needed after the adjustable attenuator to split the single optical signal into two. Instead, a half-glass plate and a polarizing beam splitter are used in the adjustable attenuator section to precisely adjust the intensity of the optical signal passing through the sample under test. During the attenuation process of the adjustable attenuator from high to low, a first optical power meter records the laser power reflected by the polarizing beam splitter in real time, obtaining a set of reference optical power data. Simultaneously, a second optical power meter synchronously measures the power of the probe light after passing through the saturable absorber sample under test, forming a set of probe-received optical power data. Based on the linear relationship between the power intensity of the reflected light and the probe light, the probe input optical power value under the corresponding attenuation conditions can be calculated from the reference optical power data.

[0039] The advantages and beneficial effects of this invention are:

[0040] 1. The laser signal emitted in this invention is no longer split into two paths via a coupler. Instead, a more precise and concise control method is employed: a combined optical system integrating a half-wave plate and a polarizing beam splitter is incorporated into the adjustable attenuator section. This single-channel optical path structure integrates the "splitting" process with the adjustable attenuator, not only optimizing the overall structure of the optical path but also solving the problem in traditional testing methods where the coupling ratio of the coupling device fluctuates with increasing incident light intensity, ultimately affecting the test results.

[0041] 2. The adjustable attenuator section adopts a spatial optical path structure, which greatly shortens the total length of the optical fiber in the saturable absorber test system and effectively reduces the influence of the dispersion effect of the optical fiber medium on the measurement results of the saturable absorption characteristics.

[0042] In some embodiments of this application, the laser is a femtosecond laser source, wherein the wavelength of the femtosecond laser source is one of 1550nm, 1300nm, and 1060nm;

[0043] The laser is a polarization-maintaining output, and the output beam is a highly linearly polarized laser.

[0044] In some embodiments of this application, the laser is connected to the sample placement device via an optical amplifier and an adjustable attenuator.

[0045] In some embodiments of this application, the half-wave plate is an achromatic glass plate and is mounted in a high-precision rotary mounting base using a threaded adapter;

[0046] The polarization beam splitter uses a Glan laser polarizer with an antireflection coating and is mounted in a high-precision rotary mount.

[0047] Specifically, by precisely rotating the half-wave plate, the polarization direction of the incident linearly polarized light can be changed, causing the incident beam to be attenuated to different degrees after passing through the Glan polarizer, thus achieving precise adjustment of the subsequent output power.

[0048] like Figure 2 As shown, in some embodiments of this application, the optical power meter includes: a first optical power meter and a second optical power meter; wherein, the first optical power meter is used to measure the optical power of the laser reflected from the side window of the polarization beam splitter, and the second optical power meter is used to measure the optical power of the beam after the probe light passes through the saturable absorber.

[0049] It should be understood that in the embodiments of the present invention, the adjustable attenuator adopts the form of a spatial optical path. Therefore, when connecting with the front and rear devices, if the optical fiber path used by the connected device needs to be aligned with a collimator, it is necessary to ensure that the light energy emitted by the femtosecond laser is received by the two power meters (referring to the first optical power meter and the second optical power meter) as much as possible.

[0050] In some embodiments of this application, a method for testing saturable absorbers is also disclosed, comprising the following steps:

[0051] Step 1: Rotate the half-wave plate to change its optical axis direction, causing the incident laser signal to undergo adjustable attenuation to varying degrees as it passes through the polarization beam splitter. The polarization beam splitter is used to split the incident laser into reflected and transmitted light.

[0052] Step 2: Using the transmitted light as the probe light for subsequent tests and the reflected light as the reference light, a complete performance evaluation of the saturable absorber is completed. The specific process is as follows: During the attenuation change of the adjustable attenuator from high to low, the laser power reflected by the polarization beam splitter is recorded in real time using a first optical power meter to obtain a set of reference optical power data. Simultaneously, a second optical power meter is used to synchronously measure the optical power of the probe light after passing through the saturable absorber sample under test, forming a set of probe-received optical power data. Based on the linear change relationship in power intensity between the reflected light and the probe light, the probe input optical power value under the corresponding attenuation condition can be calculated based on the reference optical power data. The ratio of the calculated probe input optical power value to the probe-received optical power is defined as the transmittance of the saturable absorber sample under the same attenuation level. Based on different attenuation conditions, the corresponding probe-received optical power and its corresponding sample transmittance are calculated one by one, and finally, the nonlinear transmission curve of the sample under test is plotted.

[0053] The beneficial effects of this invention are:

[0054] 1. In an embodiment of the present invention, another form of test method and system is provided, wherein the adjustable attenuator adopts a spatial optical path form. This design significantly simplifies the complexity of the optical path structure and effectively shortens the total length of the optical fiber in the saturable absorber test system, thereby reducing the influence of the dispersion effect of the optical fiber medium on the measurement results of the saturable absorption characteristics.

[0055] 2. In this invention, the optical signal emitted by the laser is no longer split into two paths via a coupler. Instead, a more precise and concise control method is employed: a combined optical system of a half-wave plate and a polarizing beam splitter is integrated into the adjustable attenuator section. This design adjusts the polarization state of the incident light by precisely controlling the rotation angle of the half-wave plate, and then uses the polarizing beam splitter to split the incident laser into a probe beam and a reference beam. The splitting ratio is dynamically adjusted by rotating the half-wave plate.

[0056] During the attenuation process of the adjustable attenuator from high to low, the laser power reflected by the polarization beam splitter is recorded in real time using a first optical power meter to obtain a set of reference optical power data. Simultaneously, a second optical power meter is used to synchronously measure the optical power of the probe light after passing through the saturable absorber sample under test, forming a set of probe-received optical power data. Based on the linear relationship between the power intensity of the reflected light and the probe light, the probe input optical power value under the corresponding attenuation condition can be calculated from the reference optical power data. This method focuses on optimizing the optical path structure, integrating the functions of attenuation and beam splitting, shortening the total length of the optical fiber in the saturable absorber testing system, effectively reducing the influence of the dispersion effect of the optical fiber medium on the measurement results of the saturable absorption characteristics, and providing a more reliable data foundation for subsequent measurement of the optical properties of the sample.

[0057] Those skilled in the art should also understand that fiber dispersion has multiple effects on the measurement of nonlinear transmission curves of saturable absorbers, specifically as follows: First, fiber dispersion causes pulse broadening of the incident light, thereby reducing the peak power of the light pulse passing through the saturable absorber. For example, assuming the peak power of the incident light pulse is 1kW, due to the dispersion effect, the actual peak power reaching the saturable absorber may drop to 600W. This power reduction prevents the saturable absorber from reaching complete saturation, adversely affecting the accurate characterization of the nonlinear transmission curve. Second, the pulse broadening caused by fiber dispersion also leads to a deviation between the actual measured value and the expected value of the abscissa of the nonlinear transmission curve (such as the peak power of the incident light), thus causing the measured curve to shift in the abscissa direction. Nonlinear transmission curves typically exhibit the following characteristics: high absorption loss at low incident light intensity; as the incident light intensity increases, the absorption loss gradually decreases, eventually approaching saturation. However, if the saturable absorber fails to fully saturate, the saturated portion of the curve cannot be accurately represented, causing a deviation between the curve shape and the actual situation, thus affecting the accuracy of the measurement results.

[0058] The embodiments of the present invention will be described in detail below with reference to specific examples.

[0059] like Figure 2As shown, in this embodiment, the laser source selected is a Zimao femtosecond laser seed source (ZIMAO, TCR-FS-1560-0.1). The laser's pulse width and repetition frequency are 200 fs and 80 MHz, respectively, and the output beam is linearly polarized light with an average output power of up to 40 mW. This embodiment uses a polarization-dependent attenuation device, which requires the light source used in the test system to be polarization-maintaining. In addition, this test system also has a minimum requirement for the output power of the light source. If the output power of the light source is too low, the saturable absorber material under test may not reach a saturated absorption state, ultimately affecting the measurement results.

[0060] The adjustable attenuator section employs a combination of a half-wave plate and a polarizing beam splitter. The half-wave plate is an achromatic glass plate (Thorlabs, AHWP05M-1600), mounted in a high-precision rotary mount (PRM1 / M) using a threaded adapter (Thorlabs, AD12F). The polarizing beam splitter is a Glan-type laser polarizer with an anti-reflection coating (Thorlabs, GL10-C), also mounted in a high-precision rotary mount (Thorlabs, PRM1GL10 / M). Its working principle is as follows: by precisely rotating the half-wave plate, the polarization direction of the incident beam can be changed, causing the incident beam to undergo varying degrees of attenuation after passing through the Glan polarizer, thus achieving precise adjustment of the subsequent output power. In this embodiment, the attenuator section uses a spatial optical path; the beam reaches the Glan polarizer after passing through the half-wave plate. The working principle of the Glan polarizer is as follows... Figure 3 As shown, light in the incident beam that is aligned with the optical axis of the Glan polarizer is allowed to pass through, while other components are reflected. Thus, as the front half-wave plate is adjusted, the components of the output light and the components of the reflected light will change continuously. In this embodiment, the manual adjustment attenuation range of the attenuator is 3dB-35dB, that is, the insertion loss of the spatial attenuator is 3dB.

[0061] In this embodiment, a thin-film carbon nanotube material is used as the saturable absorber to be tested. During the test, the carbon nanotube film needs to be placed at the end face of the optical fiber to ensure that the light beam undergoes saturation absorption after passing through the carbon nanotube material.

[0062] In this embodiment, two power meters are used to measure the reflected and output light from the Glan polarizer, respectively. The first optical power meter is a handheld digital optical power meter (Thorlabs, PM100D), paired with a standard diode power probe to measure the light power intensity reflected from the Glan polarizer. During the attenuation process of the adjustable attenuator from high to low, the first optical power meter records the laser light power reflected by the polarization beam splitter in real time, obtaining a set of reference optical power data. Simultaneously, the second optical power meter synchronously measures the light power of the probe light after passing through the saturable absorber sample, forming a set of probe-received optical power data. Based on the linear relationship between the power intensity of the reflected and probe light, the probe input optical power value under the corresponding attenuation conditions can be calculated from the reference optical power data. The second optical power meter is a handheld power meter with an optical fiber connector, used to measure the beam intensity of the probe light after passing through the saturable absorber.

[0063] It should be noted that in the embodiments of the present invention, the adjustable attenuator adopts the form of a spatial optical path. Therefore, when connecting with the front and rear devices, if the optical fiber path used by the connected device needs to be aligned with a collimator, it is necessary to ensure that the light energy emitted by the femtosecond laser is received by the two power meters (referring to the first optical power meter and the second optical power meter) as much as possible, that is, to reduce the insertion loss of the attenuator part.

[0064] The specific measurement steps used in this embodiment of the invention are as follows:

[0065] After turning on the laser, adjust the rotation angle of the half-wave plate to ensure the incident beam gradually increases from small to large, keeping the angle of the Glan polarizer constant. Record the optical signal intensity measured by the first and second optical power meters under different half-wave plate angles. Note that the recorded data is more dense under relatively low-power incident light conditions. Based on the linear relationship between the power intensity of the reflected and probed light, the probe input optical power value under the corresponding attenuation condition can be calculated based on the reference optical power data measured by the first optical power meter. Simultaneously, the ratio of the calculated probe input optical power value to the probe received optical power measured by the second optical power meter is defined as the transmittance of the saturable absorber sample under the same attenuation level. Based on different attenuation conditions, calculate the corresponding probe received optical power and its corresponding sample transmittance, and finally plot the nonlinear transmission curve of the sample under test. Fit the curve according to the following formula:

[0066] ;

[0067] in, T I represents the transmittance related to the intensity of the sample under test, and I represents the intensity of the probe light. Modulation depth is a key parameter. The key parameter is saturation intensity. This represents the background loss of light transmission in the sample.

[0068] In this application, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. In case of any inconsistency, the meaning set forth in this specification or derived from the content described herein shall prevail. Furthermore, the terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit the scope of this application.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A saturable absorber test system, comprising: The application relates to a device for measuring nonlinear transmission of a saturable absorber, comprising the following parts: a laser for emitting a pulsed light signal of a specific wavelength; an optical amplifier for receiving and amplifying the pulsed light signal emitted by the laser so that the light power of the amplified light signal output by the optical amplifier meets a preset power standard; an adjustable attenuator comprising a half-wave plate and a polarization beam splitter, wherein the half-wave plate is used for changing the polarization direction of the incident linearly polarized light so that the amplified light signal input into the adjustable attenuator is subjected to adjustable attenuation of a specific degree when passing through the polarization beam splitter, and the polarization beam splitter is used for splitting the incident laser into probe light and reference light, wherein the splitting ratio is dynamically adjusted by rotating the half-wave plate; a sample placement device for placing a saturable absorber sample to be tested; a light power meter for measuring the light power intensity of the light signal before and after passing through the saturable absorber sample in the passage; a signal processing unit for processing the two groups of light power value data measured by the light power meter to obtain the power intensity of the probe light and the transmittance of the probe light through the saturable absorber sample, and drawing a nonlinear transmission curve of the saturable absorber sample according to the transmittance; the half-wave plate is made of an achromatic plate and is installed in a high-precision rotating mounting seat by using a threaded adapter; the polarization beam splitter is made of a Glaan laser polarizer coated with an antireflection film and is installed in a high-precision rotating mounting seat; in the process of changing the attenuation of the adjustable attenuator from high to low, the first light power meter is used for recording the light power of the laser reflected by the polarization beam splitter in real time to obtain a group of reference light power data; meanwhile, the second light power meter is used for synchronously measuring the light power of the probe light after passing through the saturable absorber sample to be tested to form a group of probe received light power data; based on the linear change relationship between the reflected light and the probe light in the power intensity, the probe input light power value under the corresponding attenuation condition can be calculated according to the reference light power data, and the ratio of the calculated probe input light power value to the probe received light power is defined as the transmittance of the saturable absorber sample under the same attenuation degree; based on different attenuation conditions, the corresponding probe received light power and the corresponding sample transmittance are calculated one by one, and finally the nonlinear transmission curve of the sample to be tested is drawn.

2. A saturable absorber test system as claimed in claim 1, wherein, the laser adopts a femtosecond laser source, wherein the wavelength of the femtosecond laser source is one of 1550 nm, 1300 nm and 1060 nm; the laser is a polarization maintaining output, and the output light beam is highly linearly polarized laser.

3. A saturable absorber test system as claimed in claim 2, wherein, the laser is connected with the optical amplifier, the adjustable attenuator and the sample placement device.

4. A saturable absorber test system as claimed in claim 3, wherein, the light power meter comprises a first light power meter and a second light power meter; the first light power meter is used for measuring the light power of the laser reflected by the side window of the polarization beam splitter, and the second light power meter is used for measuring the light power of the laser after the probe light transmits through the saturable absorber.

5. A saturable absorber test method based on the saturable absorber test system according to any one of claims 1 to 4, characterized by, The application relates to a device for measuring nonlinear transmission of a saturable absorber, comprising the following parts: Step one, rotating the half-wave plate to change the optical axis direction so that the incident laser signal is subjected to adjustable attenuation of different degrees when passing through the polarization beam splitter, and the polarization beam splitter is used for splitting the incident laser into reflected light and transmitted light; Step two, the transmitted light as the probe light of the subsequent test, the reflected light as the reference light of the subsequent test, complete a complete saturable absorber performance evaluation, the specific process is: in the process of the adjustable attenuator from high to low attenuation change, using the first optical power meter real-time record the reflected laser light power by the polarization beam splitter, obtain a set of reference light power data; At the same time, using the second optical power meter synchronous measurement probe light through the measured saturable absorber sample after the optical power, form a set of probe received light power data, based on the linear variation relationship between the reflected light and the probe light on the power intensity, can be calculated according to the reference light power data under the corresponding attenuation conditions of probe input light power value, at the same time, the calculated probe input light power value and probe received light power ratio is defined as the same attenuation degree under the saturable absorber sample transmittance, based on different attenuation conditions, calculate the corresponding probe received light power and its corresponding sample transmittance, and finally draw the nonlinear transmission curve of the sample to be tested.

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