CN103148941A - Device and method for measuring beam quality of supercontinuum source - Google Patents

Abstract

The invention relates to a measurement technology for the beam quality of a supercontinuum light source, and provides a measuring device and method for measuring the beam quality of a supercontinuum light source. The measuring device includes a spectrometer, a mirror, a wide-band beam splitting prism, a near-field array CCD, a far-field array CCD and a computer for processing measurement information. The measurement method includes: use a spectrometer to measure the spectrum of the supercontinuum light source, and obtain the spectral center of gravity according to the measurement results; use an area array CCD to measure the near-field light field distribution and the far-field light field distribution, and obtain the near-field spot radius and Far-field divergence angle; construct an ideal Gaussian mode beam, calculate the SC-M ² factor, and use the SC-M ² factor to evaluate the beam quality of the supercontinuum light source. The invention can evaluate the overall beam quality of the wide-spectrum supercontinuum light source instead of just evaluating and measuring the beam quality of certain spectral components in the light source.

Description

Measuring device and method for measuring beam quality of supercontinuum light source

technical field

The invention relates to a technique for measuring the beam quality of a supercontinuum light source, in particular to a method for measuring the beam quality of a supercontinuum light source by using the spectral center of gravity.

Background technique

Beam quality is an extremely important parameter in laser application technology. It is a performance index for evaluating laser characteristics in terms of quality. It has very important guiding significance for the design, manufacture, detection and application of lasers.

At present, there are many methods to evaluate the laser beam quality, such as ^M2 factor, power in the barrel, Strehl ratio, etc. , 1643-1653], where the ^M2 factor is defined as the ratio of the product of the spot radius of the actual beam and its far-field divergence angle to the corresponding product of the ideal Gaussian mode beam, and the power in the bucket is the actual beam in the far-field plane at a fixed The ratio of the power in the bucket of the radius to the total power of the light source, Strehl ratio is defined as the ratio of the actual beam peak power to the ideal beam peak power. For these methods, there are also corresponding beam quality measuring devices to measure them (as described in patent Nos. ZL 200620039036.1 and 200510030096.7). However, these methods and measuring devices are only applicable to traditional quasi-monochromatic narrow-band spectral laser light sources.

The supercontinuum light source is a new type of wide-spectrum light source, which has the advantages of good coherence, high brightness, and good directionality of traditional lasers, and also has a wide spectrum (usually greater than 1 THz). Due to the wide-spectrum characteristics of the supercontinuum light source, the traditional laser beam quality evaluation methods and measurement devices introduced above are not suitable for evaluating and measuring the beam quality of the supercontinuum light source. At present, the main method used to evaluate the beam quality of supercontinuum light sources is to use filtering methods (such as narrow-band filters) to filter out the spectral components in supercontinuum light sources, and use traditional beam quality measurement devices for the filtered narrowband light Making measurements [X.Chenan, X.Zhao, M.N.Islam, F.L.Terry, M.J.Freeman, A.Zakel, and J.Mauricio, "10.5W Time-Averaged Power Mid-IR SupercontinuumGeneration Extending Beyond 4μm With Direct Pulse Pattern Modulation, "IEEE Journal of Selected Topics in Quantum Electronics, 2009, 15, 422-434], did not measure the overall beam quality of the supercontinuum light source, so it cannot reflect the characteristics of the entire light source, and loses its overall value as a new wide-spectrum light source. In addition, researchers have also studied the beam quality of photonic crystal fibers, an important nonlinear medium for supercontinuum light sources, but this method is also carried out for a single wavelength and cannot reflect the beam quality generated by photonic crystal fibers. Overall beam quality of supercontinuum sources [Y.Vidne and M.Rosenbluh, "Spatialmodes in a PCF fiber generated continuum," Opt. Express, 2005, 13, 9721-9728].

Contents of the invention

The technical problem to be solved by the present invention is to provide a measuring device and method for measuring the beam quality of a supercontinuum light source, which can evaluate and measure the beam quality of the supercontinuum light source as a whole, Instead of measuring its beam quality by wavelength.

The principle of the present invention is as follows: firstly, a spectrometer is used to measure the spectrum of a supercontinuum light source, and the first-order moment of the spectral distribution, that is, the spectral center of gravity, is obtained according to the measurement result. The near-field light field distribution and the far-field light field distribution of the supercontinuum beam are measured by an area array CCD, and the near-field spot radius and the far-field divergence angle are obtained by using the second-order moment method from the measurement results. Taking the ideal Gaussian mode beam at the center of gravity of the spectrum as the reference beam, calculate the measured supercontinuum beam parameter product (beam parameter product, denoted as BPP, that is, the product of the near-field spot radius and the far-field divergence angle) and the reference beam The ratio of the beam parameter product is defined as the SC-M ² factor (SC: supercontinuum, supercontinuum), and this value is used to evaluate the beam quality of the supercontinuum light source.

The technical scheme that the present invention specifically adopts is:

A measuring device for measuring the beam quality of a supercontinuum light source, comprising a spectrometer, a reflector, a broadband beam splitter, a near-field array CCD, a far-field array CCD and a computer for processing measurement information; the spectrometer is used for measuring The spectrum of the supercontinuum light source; the supercontinuum light beam output by the supercontinuum light source is collimated and expanded by a reflector, and then split through a wide-band beamsplitter prism to obtain a reflected beam and a transmitted beam, and the reflected beam is obtained by The near-field surface array CCD measures the near-field light field distribution, and the transmitted light beam is measured by the far-field surface array CCD to measure the far-field light field distribution. The distance; the computer calculates and obtains the measurement result according to the spectrum of the supercontinuum light source, the near-field light field distribution and the far-field light field distribution.

Preferably, the distance between the far-field CCD and the reflector is 10 times the Rayleigh distance of the supercontinuum light source beam.

Preferably, the spectral measurement range of the spectrometer includes the entire spectral range of the supercontinuum light source.

Preferably, the reflector is a gold-coated off-axis parabolic reflector.

The present invention also provides a method for measuring the beam quality of a supercontinuum light source, comprising the following steps:

S1. Use a spectrometer to measure the spectrum of the supercontinuum light source, and then calculate the first-order moment of the spectral distribution according to the measurement results to obtain the spectral center of gravity;

S2. Use the area array CCD to measure the near-field light field distribution and far-field light field distribution of the supercontinuum beam respectively, and use the second-order moment method to calculate the near-field spot radius and far-field divergence angle for the measurement results, and then calculate The beam parameter product of the supercontinuum beam;

S3. take the center of gravity of the spectrum obtained in step S1 as the wavelength to construct an ideal Gaussian mode beam, and calculate the beam parameter product of the ideal Gaussian mode beam;

S4. the result of dividing the beam parameter product of the supercontinuum beam obtained by step S2 by the beam parameter product of the ideal Gaussian mode beam obtained by step S3 is used as an evaluation factor for evaluating the beam quality of the supercontinuum light source, Evaluate the beam quality of the supercontinuum light source.

Preferably, the step of evaluating the beam quality of the supercontinuum light source in the step S4 includes: comparing the evaluation factor with 1, and the beam with the evaluation factor close to 1 is a beam of good quality.

Preferably, the step of measuring the near-field light field distribution and the far-field light field distribution of the supercontinuum light beam using an area array CCD respectively in the step S2 includes:

S21. Collimating and expanding the supercontinuum beam output by the supercontinuum light source through a reflector;

S22. Splitting light through a broadband beam splitting prism to obtain reflected light beams and transmitted light beams;

S23. The reflected light beam obtained in step S22 adopts a near-field surface array CCD to measure the near-field light field distribution, and adopts a far-field surface array CCD to measure the far-field light field distribution for the transmitted light beam, and the far-field surface array CCD is at a distance from the reflector The distance is greater than the Rayleigh distance of the supercontinuum light source beam.

Preferably, in the step S23, the distance between the CCD of the far-field surface array and the mirror is 10 times the Rayleigh distance of the supercontinuum light beam.

Preferably, the spectral measurement range of the spectrometer in the step S1 includes the entire spectral range of the supercontinuum light source.

Preferably, the reflector in the step S2 is a gold-coated off-axis parabolic reflector.

The present invention can achieve the following technical effects: measure and calculate the spectral center of gravity of the supercontinuum light source spectrum, construct a Gaussian mode beam as a reference beam with the spectral center of gravity as the center wavelength, and measure the near-field beam width and far-field divergence of the supercontinuum light source The measurement of the angle can evaluate the beam quality of the wide-spectrum supercontinuum light source as a whole, instead of just evaluating and measuring the beam quality of certain spectral components in the light source.

Description of drawings

Fig. 1 is a schematic diagram of supercontinuum light source spectrum measurement;

Fig. 2 is the structural representation of measuring device embodiment of the present invention;

Fig. 3 is the flowchart of measuring method of the present invention;

Fig. 4 is a flow chart of measuring near-field light field distribution and far-field light field distribution in an embodiment of the measurement method of the present invention.

Detailed ways

Figure 1 is a schematic diagram of the spectrum measurement of a supercontinuum light source, in which the supercontinuum output from the supercontinuum output port 1 is received by a spectrometer 2 and its spectrum is measured. During the measurement process, the resolution is selected according to the performance of the spectrometer 2, and its spectral measurement range should cover the entire spectral range of the supercontinuum light source, generally from the wavelength corresponding to the maximum value of the measured spectrum to the wavelength corresponding to the value less than 60dB of the maximum value range between.

Fig. 2 shows an embodiment of the light beam quality measuring device of the supercontinuum light source of the present invention. It includes a gold-plated off-axis parabolic reflector 3, a dichroic prism 4, a near-field array CCD 5 and a far-field array CCD6, and a computer 7 for processing measurement information. A solid line with an arrow in the figure indicates a light beam.

The supercontinuum beam output from the supercontinuum output terminal 1 is collimated and expanded by the reflector 3, and then split by the wide-band beam splitter prism 4. The reflected beam is measured by the near-field array CCD 5. The near-field light field distribution is used for the measurement results. The second-order moment method can calculate the near-field spot size w of the light field. When the transmitted beam is transmitted ten times the Rayleigh distance of the supercontinuum beam, that is, z=10L shown in the figure (L is the Rayleigh distance of the supercontinuum beam), the light field distribution is the far field distribution of the supercontinuum beam, which is given by Far-field surface array CCD6 measurement, the second-order moment method can be used to calculate the light field near-field spot size, and divide it by the transmission distance to obtain the beam far-field divergence angle θ. At the same time, the center of gravity of the spectrum is calculated according to the spectral distribution of the supercontinuum light source, and then the overall beam quality of the supercontinuum light source is calculated.

Fig. 3 and Fig. 4 show the flowchart of the measuring method of the present invention. The concrete technical scheme of measuring method of the present invention can be further described as follows:

First, use a spectrometer to measure the spectrum of the supercontinuum light source. During the measurement process, select the resolution according to the performance of the spectrometer, and the spectral measurement range should cover the entire spectral range of the supercontinuum light source, generally from the wavelength corresponding to the maximum value of the measured spectrum The range between wavelengths corresponding to values 60 dB less than the maximum value. Find the first-order moment of the measured spectrum, as follows

$\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; =</span>\frac{{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; \&infin;</span>}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&lambda;d\&lambda;</span>}}{{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; \&infin;</span>}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d\&lambda;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

为光谱重心。由于光谱仪测得的数据为分立的数据点，并不是连续值，因此在计算中使用求和来代替积分，如下式Where P _λ (λ) is the spectral distribution, λ is the wavelength,

is the center of gravity of the spectrum. Since the data measured by the spectrometer are discrete data points and not continuous values, the summation is used instead of the integral in the calculation, as shown in the following formula

$\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&lambda;\&Delta;\&lambda;</span>}}{\underset{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&Delta;\&lambda;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

where Δλ is the resolution of the spectrometer.

Secondly, use a gold-coated off-axis parabolic mirror to collimate the output supercontinuum beam, and then use an area array CCD that responds to the entire spectral range to measure the near-field distribution of the supercontinuum beam near the output of the mirror , using the second-order moment method to obtain the beam width of the beam. The specific method is to first use the first-order moment to obtain the center of gravity of the beam, as follows

$\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span>\frac{{<span\; class="notranslate">\; \&Integral;</span><span\; class="notranslate">\; \&Integral;</span>}_{<span\; class="notranslate">\; -</span><span\; class="notranslate">\; \&infin;</span>}^{<span\; class="notranslate">\; \&infin;</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; wxya</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; dxdy</span>}}{{<span\; class="notranslate">\; \&Integral;</span><span\; class="notranslate">\; \&Integral;</span>}_{<span\; class="notranslate">\; -</span><span\; class="notranslate">\; \&infin;</span>}^{<span\; class="notranslate">\; \&infin;</span>}\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; dxdy</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

$\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; =</span>\frac{{<span\; class="notranslate">\; \&Integral;</span><span\; class="notranslate">\; \&Integral;</span>}_{<span\; class="notranslate">\; -</span><span\; class="notranslate">\; \&infin;</span>}^{<span\; class="notranslate">\; \&infin;</span>}\mathrm{<span\; class="notranslate">\; yP</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; dxdy</span>}}{{<span\; class="notranslate">\; \&Integral;</span><span\; class="notranslate">\; \&Integral;</span>}_{<span\; class="notranslate">\; -</span><span\; class="notranslate">\; \&infin;</span>}^{<span\; class="notranslate">\; \&infin;</span>}\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; dxdy</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

In the formula, P(x, y) is the light field intensity distribution measured by the area array CCD, and x and y are the two vertical coordinate axes of the area array CCD, respectively. Then use the second moment to calculate the beam width as follows

${\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2</span>}\sqrt{\frac{{<span\; class="notranslate">\; \&Integral;</span><span\; class="notranslate">\; \&Integral;</span>}_{<span\; class="notranslate">\; -</span><span\; class="notranslate">\; \&infin;</span>}^{<span\; class="notranslate">\; \&infin;</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; -</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; dxdy</span>}}{{<span\; class="notranslate">\; \&Integral;</span><span\; class="notranslate">\; \&Integral;</span>}_{<span\; class="notranslate">\; -</span><span\; class="notranslate">\; \&infin;</span>}^{<span\; class="notranslate">\; \&infin;</span>}\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; dxdy</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2</span>}\sqrt{\frac{{<span\; class="notranslate">\; \&Integral;</span><span\; class="notranslate">\; \&Integral;</span>}_{<span\; class="notranslate">\; -</span><span\; class="notranslate">\; \&infin;</span>}^{<span\; class="notranslate">\; \&infin;</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; -</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; dxdy</span>}}{{<span\; class="notranslate">\; \&Integral;</span><span\; class="notranslate">\; \&Integral;</span>}_{<span\; class="notranslate">\; -</span><span\; class="notranslate">\; \&infin;</span>}^{<span\; class="notranslate">\; \&infin;</span>}\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; dxdy</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

Where w _x , w _y are beam radii respectively. Since the measurement results of the area array CCD are discrete data, the integrals in the above formula should be replaced by summation, as shown in the following formula

$\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\underset{\mathrm{<span\; class="notranslate">\; the\; y</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\mathrm{<span\; class="notranslate">\; wxya</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&Delta;x\&Delta;y</span>}}{\underset{\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\underset{\mathrm{<span\; class="notranslate">\; the\; y</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\mathrm{<span\; class="notranslate">\; \&Sigma;P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&Delta;x\&Delta;y</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

$\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\underset{\mathrm{<span\; class="notranslate">\; the\; y</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\mathrm{<span\; class="notranslate">\; yP</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&Delta;x\&Delta;y</span>}}{\underset{\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\underset{\mathrm{<span\; class="notranslate">\; the\; y</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;P</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&Delta;x\&Delta;y</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2</span>}\sqrt{\frac{\underset{\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\underset{\mathrm{<span\; class="notranslate">\; the\; y</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; -</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&Delta;x\&Delta;y</span>}}{\underset{\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\underset{\mathrm{<span\; class="notranslate">\; the\; y</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&Delta;x\&Delta;y</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2</span>}\sqrt{\frac{\underset{\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\underset{\mathrm{<span\; class="notranslate">\; the\; y</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; -</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&Delta;x\&Delta;y</span>}}{\underset{\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\underset{\mathrm{<span\; class="notranslate">\; the\; y</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&Delta;x\&Delta;y</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

Where Δx and Δy are the resolution of the area array CCD, respectively.

定义超连续谱光束的瑞利距离From the measured near-field beam width w _x and w _y and the spectral center of gravity

Defining the Rayleigh distance of a supercontinuum beam

$\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; :</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&pi;</span>}{<span\; class="notranslate">\; (</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; /</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; .</span>$

According to the theory of Gaussian mode beams, the beam can be considered collimated within the Rayleigh distance at both ends of the beam waist position, and the light field distribution far greater than the Rayleigh distance can be considered as the far field distribution of the beam. Therefore, the light field distribution of the supercontinuum beam is measured respectively at a distance of ten times the Rayleigh distance from the off-axis parabolic mirror by using an area array CCD. The beam width is obtained similarly by using the second-order moment method, and the far-field divergence angles θ _x and θ _y of the supercontinuum beam are obtained by dividing the beam width by the transmission distance.

由测量得到的超连续谱光源光束束宽与远场发散角可以计算得到评价超连续谱光源整体光束质量的评价因子（记为SC-M²）如下式：The ideal Gaussian mode beam is constructed with the spectral center of gravity as the wavelength, and it is used as a reference beam for evaluating the beam quality of the supercontinuum light source. The beam parameter product of the beam is

The evaluation factor (denoted as SC-M ² ) for evaluating the overall beam quality of supercontinuum light sources can be calculated from the measured beam width and far-field divergence angle of supercontinuum light sources as follows:

$\mathrm{<span\; class="notranslate">\; SC</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}}{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 11</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{<span\; class="notranslate">\; SC</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}}{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 12</span>}<span\; class="notranslate">\; )</span>$

Use this factor to evaluate the beam quality of the supercontinuum light source, the closer the value is to 1, the better the beam quality.

Claims (10)

1. A measuring device for measuring the beam quality of a supercontinuum light source, characterized in that it includes a spectrometer (2), a reflector (3), a broadband beam splitter (4), a near field array CCD (5), a far A field array CCD (6) and a computer (7) for processing measurement information; the spectrometer (2) is used for measuring the spectrum of the supercontinuum light source; the supercontinuum beam output by the supercontinuum light source is reflected The mirror (3) collimates and expands the beam, and then splits the beam through the broadband beam splitter (4) to obtain the reflected beam and the transmitted beam. The near-field light field distribution of the reflected beam is measured by the near-field array CCD (5), and the transmitted beam The beam is measured by the far-field surface array CCD (6) to measure the far-field light field distribution; the distance between the far-field surface array CCD (6) and the mirror (3) is greater than the Rayleigh distance of the supercontinuum light source beam; the The computer (7) calculates and obtains measurement results according to the spectrum of the supercontinuum light source, the near-field light field distribution and the far-field light field distribution. 2. The measuring device for measuring the beam quality of a supercontinuum light source according to claim 1, characterized in that the distance between the far-field array CCD (6) and the mirror (3) is the supercontinuum 10 times the Rayleigh distance of the spectral source beam. 3. The measuring device for measuring the beam quality of a supercontinuum light source according to claim 1 or 2, characterized in that: the spectral measurement range of the spectrometer (2) includes the entire spectral range of the supercontinuum light source. 4. The measuring device for measuring the beam quality of a supercontinuum light source according to claim 1 or 2, characterized in that: the reflector (3) is a gold-coated off-axis parabolic reflector. 5. A method for measuring the beam quality of a supercontinuum light source, characterized in that it may further comprise the steps: S1. Use a spectrometer to measure the spectrum of the supercontinuum light source, and then calculate the first-order moment of the spectral distribution according to the measurement results to obtain the spectral center of gravity; S2. Use the area array CCD to measure the near-field light field distribution and far-field light field distribution of the supercontinuum beam respectively, and use the second-order moment method to calculate the near-field spot radius and far-field divergence angle for the measurement results, and then calculate The beam parameter product of the supercontinuum beam; S3. take the center of gravity of the spectrum obtained in step S1 as the wavelength to construct an ideal Gaussian mode beam, and calculate the beam parameter product of the ideal Gaussian mode beam; S4. the result of dividing the beam parameter product of the supercontinuum beam obtained by step S2 by the beam parameter product of the ideal Gaussian mode beam obtained by step S3 is used as an evaluation factor for evaluating the beam quality of the supercontinuum light source, Evaluate the beam quality of the supercontinuum light source. 6. the method for measuring the beam quality of a supercontinuum light source according to claim 5, characterized in that: the step of evaluating the beam quality of the supercontinuum light source in the step S4 comprises: according to the The evaluation factor is compared with 1, and the beam with the evaluation factor close to 1 is a beam with good quality. 7. according to claim 5 or 6 described for measuring the measuring method of supercontinuum light source beam quality, it is characterized in that: use area array CCD respectively in the described step S2 to the near-field light field distribution of supercontinuum light beam and The steps for measuring the far-field optical field distribution include: S21. Collimating and expanding the supercontinuum beam output by the supercontinuum light source through a reflector; S22. Splitting light through a broadband beam splitting prism to obtain reflected light beams and transmitted light beams; S23. The reflected light beam obtained in step S22 adopts a near-field surface array CCD to measure the near-field light field distribution, and adopts a far-field surface array CCD to measure the far-field light field distribution for the transmitted light beam, and the far-field surface array CCD is at a distance from the reflector The distance is greater than the Rayleigh distance of the supercontinuum light source beam. 8. The measuring method for measuring the beam quality of a supercontinuum light source according to claim 7, characterized in that: in the step S23, the distance between the far-field surface array CCD and the reflector is the ray of the supercontinuum beam. 10 times the benefit distance. 9. The measurement method for measuring the beam quality of a supercontinuum light source according to claim 8, characterized in that: the spectral measurement range of the spectrometer in the step S1 includes the entire spectral range of the supercontinuum light source. 10. The measurement method for measuring the beam quality of a supercontinuum light source according to claim 8, characterized in that: the reflector in the step S2 is a gold-coated off-axis parabolic reflector.

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