Laser parameter measuring method for optical frequency comb system

Abstract

The invention provides a laser parameter measurement method for an optical frequency comb system, which can be used for measuring parameters such as output frequency of a laser in the optical frequency comb system. According to the invention, the problems that the optical frequency comb system uses the same output end to realize output of spatial light and optical fiber coupling light and performs laser frequency measurement by using an optical fiber coupling output mode are solved, the invalid power loss of the optical frequency comb system is reduced, the application prospect of the optical frequency comb is improved, and the method can be used for measuring the laser output frequency parameter of the optical frequency comb.

Description

Technical Field

[0001] The present invention relates to the technical field of optical metrology, and in particular to a laser parameter measurement method for an optical frequency comb system. Background Art

[0002] Femtosecond optical frequency combs are ultrashort pulses generated by mode-locked lasers. They are characterized by a series of frequency components that are evenly spaced and have a coherent and stable phase relationship in the spectrum. They are a major breakthrough in the field of laser technology after the advent of ultrashort pulse lasers. As a precision measuring instrument, optical frequency combs have excellent frequency stability, time resolution, frequency transfer and conversion characteristics, and integrate ultrafast spectroscopy and ultrastable frequency. They have important application prospects in precision measurement fields such as precision spectroscopy, laser physics, space applications, and metrology frontiers.

[0003] The optical frequency comb is like a "ruler", which enables humans to achieve ultra-precise measurements of optical frequencies. For example, the optical frequency comb can be used to measure the output frequency of a frequency-stabilized laser, and further obtain the wavelength value through the relationship between frequency and wavelength. The traditional optical comb system is mainly composed of a pump source, an oscillator, a feedback adjustment circuit and a signal source. In order to achieve the frequency measurement of the laser, a measurement optical path module needs to be added to the optical comb system; at the same time, traditional optical frequency combs mostly use the mode of optical fiber output and spatial light output separately. In the face of the high power requirements of the high repetition rate optical frequency comb, such a design will bring great power waste, so the output port of the optical frequency comb needs to be adjusted. Summary of the invention

[0004] In view of this, the present invention proposes a laser parameter measurement method for an optical frequency comb system, which can measure parameters such as the laser output frequency in the optical frequency comb system.

[0005] To achieve the above object, the technical solution of the present invention is:

[0006] A laser parameter measurement method for an optical frequency comb system comprises the following steps: firstly, adjusting the output mode of a conventional optical frequency comb system; then constructing a measurement optical path, wherein the measurement optical path comprises a beam combiner and an avalanche photodetector; wherein the output of the optical frequency comb system is returned to the optical system through a polarization-maintaining optical fiber jumper, and the output laser of a laser to be measured also enters the optical system through an optical fiber, and the two lasers are combined by the beam combiner, and the combined laser enters a photodetector to generate an analog electrical signal, which can be processed by a host computer after analog-to-digital conversion to obtain parameter information of the laser to be measured.

[0007] The specific steps include:

[0008] Adjust the output mode of the optical frequency comb system and use a dedicated adapter at the output port of the optical frequency comb to connect with an aspheric lens or a polarization-maintaining fiber patch cord;

[0009] Building a measuring optical path, wherein the measuring optical path includes a beam combiner and an avalanche photodetector;

[0010] When the optical frequency comb output is not needed, a protective cover is installed at the output port; when spatial light output is needed, an aspheric lens is installed at the output port of the optical frequency comb; when the frequency of the laser to be tested needs to be measured, the output port of the optical frequency comb is connected to the flange port of the optical system Fb1 through a polarization-maintaining fiber jumper, and the output port of the laser to be tested is connected to the flange port of the optical system Fb2;

[0011] Start the optical frequency comb and the laser to be tested, so that the output laser of the optical frequency comb and the output laser of the laser to be tested are irradiated onto the avalanche photodetector after the beam combiner;

[0012] The analog electrical signal is collected through a frequency meter and transmitted to the host computer;

[0013] Adjust the position of the comb teeth of the optical frequency comb to determine the position of the laser to be measured;

[0014] Lock the repetition frequency and offset frequency of the optical frequency comb and measure the frequency of the laser to be tested;

[0015] On the host computer, the output wavelength value of the laser to be tested is calculated based on the relationship between frequency and wavelength.

[0016] The dedicated adapter realizes the switching between the optical frequency comb output and the aspheric lens or the polarization-maintaining optical fiber jumper.

[0017] The beam combiner combines the output laser of the optical frequency comb with the output laser of the laser to be measured; and the avalanche photodetector converts the combined laser into an analog electrical signal.

[0018] The host computer processes the analog electrical signal to obtain the laser frequency of the laser to be tested; and calculates the output frequency stability of the laser to be tested by using the Allen variance formula.

[0019] Beneficial effects:

[0020] 1. The present invention solves the problem that an optical frequency comb system uses the same output end to realize spatial light and fiber-coupled light output and uses the fiber-coupled output method to measure laser frequency, reduces the ineffective power loss of the optical frequency comb system, improves the application prospect of the optical frequency comb, and can be used for measuring the output frequency parameters of the laser of the optical frequency comb.

[0021] 2. The present invention adopts a special adapter at the optical frequency comb output port to realize the connection between the optical frequency comb output and the aspheric lens. Through the aspheric lens, the optical frequency comb system can realize focused spatial light output, avoiding the divergent output of the optical fiber port, and can be used for ranging or spectral analysis.

[0022] 3. The present invention adopts a special adapter at the optical frequency comb output port to realize the connection between the optical frequency comb output and the polarization-maintaining fiber jumper. Through the polarization-maintaining fiber jumper, the output of the optical frequency comb system can be maintained in the optical fiber, which is convenient for using instruments such as spectrometers and power meters to measure the output parameters of the optical frequency comb system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the measuring optical path involved in the method of the present invention. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0025] The present invention provides a laser parameter measurement method for an optical frequency comb system, which is as follows:

[0026] First, the output mode of the traditional optical frequency comb system is adjusted. A dedicated adapter is used at the output port of the optical frequency comb to connect the optical frequency comb output to an aspheric lens or a polarization-maintaining fiber jumper. Through an aspheric lens, the optical frequency comb system can achieve focused spatial light output, avoiding divergent output from the fiber port, which can be used for ranging or spectral analysis; through a polarization-maintaining fiber jumper, the output of the optical frequency comb system can be maintained within the optical fiber, making it easier to use instruments such as spectrometers and power meters to measure the output parameters of the optical frequency comb system.

[0027] Then build a measuring optical path. The measuring optical path of the present invention is as follows: Figure 1 As shown. The measurement optical path is mainly composed of a beam combiner and an avalanche photodetector. The output of the optical frequency comb system is returned to the optical system through a polarization-maintaining fiber jumper. The output laser of the laser to be measured also enters the optical system through the optical fiber. The two lasers are combined through the beam combiner. The combined laser enters the photodetector to generate an analog electrical signal. After analog-to-digital conversion, the electrical signal can be processed by the host computer to obtain parameter information such as the laser frequency of the laser to be measured.

[0028] When the optical frequency comb is not needed for output, a protective cover is installed at the output port.

[0029] When spatial light output time is required, an aspheric lens is installed at the output port of the optical frequency comb.

[0030] When it is necessary to measure the frequency of the laser to be tested, the output port of the optical frequency comb is connected to the flange port of the optical system Fb1 through a polarization-maintaining fiber jumper. Similarly, the output port of the laser to be tested is connected to the flange port of the optical system Fb2. Then, the optical frequency comb and the laser to be tested are started. The output laser of the optical frequency comb and the output laser of the laser to be tested are irradiated onto the avalanche photodetector after passing through the beam combiner. The analog electrical signal can be collected by a frequency meter and then transmitted to the host computer.

[0031] After the optical frequency comb and the laser to be measured are stabilized, the optical frequency comb is in the preparation for measurement. At this time, it is necessary to first determine the accurate position of the laser to be measured by adjusting the comb teeth position of the optical frequency comb. After the judgment is completed, the repetition frequency and offset frequency of the optical frequency comb can be locked, and the frequency of the laser to be measured is measured. The value collected by the frequency meter will be fed back to the host computer.

[0032] On the host computer, the output wavelength value of the laser to be tested can be calculated through the relationship between frequency and wavelength, and the output frequency stability of the laser to be tested can also be calculated through the Allan variance formula.

[0033] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A laser parameter measurement method for an optical frequency comb system, characterized in that: First, the output mode of the traditional optical frequency comb system is adjusted; then a measurement optical path is built, which includes a beam combiner and an avalanche photodetector; the output of the optical frequency comb system is returned to the optical system through a polarization-maintaining fiber jumper, and the output laser of the laser to be measured also enters the optical system through the optical fiber, and the two lasers are combined by a beam combiner. The combined laser enters the photodetector to generate an analog electrical signal, which can be processed by a host computer after analog-to-digital conversion to obtain parameter information of the laser to be measured.

2. The laser parameter measurement method according to claim 1, characterized in that: The specific steps include: Adjust the output mode of the optical frequency comb system and use a dedicated adapter at the output port of the optical frequency comb to connect with an aspheric lens or a polarization-maintaining fiber patch cord; Building a measuring optical path, wherein the measuring optical path includes a beam combiner and an avalanche photodetector; When the optical frequency comb output is not needed, a protective cover is installed at the output port; when spatial light output is needed, an aspheric lens is installed at the output port of the optical frequency comb; when the frequency of the laser to be tested needs to be measured, the output port of the optical frequency comb is connected to the flange port of the optical system Fb1 through a polarization-maintaining fiber jumper, and the output port of the laser to be tested is connected to the flange port of the optical system Fb2; Start the optical frequency comb and the laser to be tested, so that the output laser of the optical frequency comb and the output laser of the laser to be tested are irradiated onto the avalanche photodetector after the beam combiner; The analog electrical signal is collected through a frequency meter and transmitted to the host computer; Adjust the position of the comb teeth of the optical frequency comb to determine the position of the laser to be measured; Lock the repetition frequency and offset frequency of the optical frequency comb and measure the frequency of the laser to be tested; On the host computer, the output wavelength value of the laser to be tested is calculated based on the relationship between frequency and wavelength.

3. The laser parameter measurement method according to claim 1 or 2, characterized in that: The dedicated adapter realizes the switching between the optical frequency comb output and the aspheric lens or the polarization-maintaining optical fiber jumper.

4. The laser parameter measurement method according to claim 1 or 2, characterized in that: The beam combiner combines the output laser of the optical frequency comb with the output laser of the laser to be measured; and the avalanche photodetector converts the combined laser into an analog electrical signal.

5. The laser parameter measurement method according to claim 3, characterized in that: The host computer processes the analog electrical signal to obtain the laser frequency of the laser to be tested; and calculates the output frequency stability of the laser to be tested by using the Allen variance formula.

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