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

Abstract

The invention relates to the measurement technology of beam quality of a supercontinuum source, and provides a device and a method for measuring the beam quality of the supercontinuum source. The measuring device comprises a spectrometer, a reflecting mirror, a broadband polarizing beam splitter, a near-field area array CCD (Charge Coupled Device), a far-field area array CCD and a computer for processing measurement information. The measuring method comprises the following steps of using the spectrometer to measure the spectrum of a supercontinuum source, and obtaining the center of gravity of the spectrum according to the measurement results; using the area array CCDs to measure the light field distribution of a near field and a far field, and obtaining a near-field spot radius and a far-field divergence angle; and constructing an ideal Gaussian fundamental mode beam, calculating an SC-M<2> (supercontinuum) factor, and using the SC-M<2> factor to evaluate the beam quality of the supercontinuum source. According to the device and the method provided by the invention, the beam quality of the supercontinuum source can be generally evaluated, not just the beam quality of certain spectral components in the light source is evaluated and measured.

Description

Be used for measuring measurement mechanism and the method for super continuum source beam quality

Technical field

The present invention relates to the measuring technique of super continuum source beam quality, especially a kind of method of using the spectrum center of gravity that the super continuum source beam quality is measured.

Background technology

Beam quality is parameter very important in laser application technique, and it is to estimate the performance index of laser characteristics from the aspect of matter, and design, manufacturing, detection and the application etc. of laser instrument are all had very important directive significance.

At present there has been a lot of methods that the beam quality of laser is estimated, as M ²The factor, Power in the bucket, Si Telieer such as compare at [Feng Guoying, Zhou Shouhuan, " discussion of laser beam quality comprehensive evaluation, " Chinese laser, 2009,36,1643-1653], the wherein M ²The factor is defined as the spot radius and the product of its far-field divergence angle and the ratio of the corresponding product of desirable Gauss's basic mode light beam of actual light beam, Power in the bucket be in the plane, far field actual light beam a certain radii fixus the bucket in power and the ratio of this light source general power, Si Telieer is than the ratio that is defined as actual light beam peak power and ideal beam peak power.Also there is corresponding beam quality measurement mechanism to measure (as described in the patent of patent No. ZL 200620039036.1 and 200510030096.7) to it for these methods.But these methods and measurement mechanism are only applicable to traditional accurate monochromatic narrow-band spectrum LASER Light Source.

Super continuum source is a kind of novel wide spectrum light source, has that the conventional laser coherence is good, the advantages such as brightness is high, good directionality, also has very wide spectrum (usually greater than 1 THz) simultaneously.Due to the wide spectral characteristics of super continuum source, evaluation method and the measurement mechanism of the conventional laser beam quality of introducing previously also is not suitable for the beam quality of super continuum source is estimated and measured.at present the super continuum source beam quality being estimated the main method of taking is to use the method (as narrow band filter slice) of filtering that the spectral component in super continuum source is leached, use the conventional beam apparatus for measuring quality to measure [X.Chenan to the narrow band light that leaches, X.Zhao, M.N.Islam, F.L.Terry, M.J.Freeman, A.Zakel, and J.Mauricio, " 10.5W Time-Averaged Power Mid-IR Supercontinuum Generation Extending Beyond 4 μ m With Direct Pulse Pattern Modulation, " IEEE Journal of Selected Topics in Quantum Electronics, 2009, 15, 422-434], the entire light quality of super continuum source is not measured, so just can not reflect the characteristic of whole light source, lose its integral body as the value of novel broad spectrum light source.In addition, the researchist also is studied the beam quality of the important nonlinear medium photonic crystal fiber that produces super continuum source, but this method is equally also carried out for single wavelength, entire light quality [the Y.Vidne and M.Rosenbluh that can not reflect the super continuum source that produces by photonic crystal fiber, " Spatial modes in a PCF fiber generated continuum, " Opt.Express, 2005,13,9721-9728].

Summary of the invention

The technical problem to be solved in the present invention is: a kind of measurement mechanism and method for measuring the super continuum source beam quality is provided, adopt this device and method super continuum source can be done as a whole its beam quality is estimated and measured, rather than its beam quality is divided the measurement of wavelength.

Principle of the present invention is: at first use spectrometer that the spectrum of super continuum source is measured, the first moment of trying to achieve spectral distribution according to measurement result is the spectrum center of gravity.Use area array CCD that near field of light field distribution and the far field distribution of super continuous spectrums light beam are measured, use second moment method to try to achieve near field spot radius and far-field divergence angle by measurement result.With desirable Gauss's basic mode light beam at spectrum center of gravity place as the reference light beam, the super continuous spectrums light beam parameters that calculating records amasss (beam parameter product, be denoted as BPP, be the product of its near field spot radius and far-field divergence angle) ratio long-pending with the light beam parameters of reference beam, defining this ratio is SC-M ²The factor (SC:supercontinuum, super continuous spectrums) uses this value that the super continuum source beam quality is estimated.

The concrete technical scheme that adopts of the present invention is:

A kind of measurement mechanism for measuring the super continuum source beam quality comprises spectrometer, catoptron, broadband Amici prism, near field area array CCD, far field area array CCD and for the treatment of the computing machine of metrical information; Described spectrometer is used for measuring the spectrum of described super continuum source; The super continuous spectrums light beam of described super continuum source output collimates through catoptron and expands, carry out light splitting through the broadband Amici prism again and obtain folded light beam and transmitted light beam, described folded light beam is measured the near field of light field distribution by the near field area array CCD, described transmitted light beam is measured far field by the far field area array CCD and is distributed, and the distance of the described catoptron of described far field area array CCD distance is greater than the Rayleigh distance of described super continuum source light beam; Described computing machine distributes according to the spectrum of described super continuum source, described near field of light field distribution and described far field and calculates measurement result.

Preferably, the distance of the described catoptron of described far field area array CCD distance is 10 times of Rayleigh distance of described super continuum source light beam.

Preferably, the spectral measurement ranges of described spectrometer comprises the spectral range of whole described super continuum source.

Preferably, described catoptron is the off-axis parabolic mirror of gold-plated film.

The present invention also provides a kind of measuring method for measuring the super continuum source beam quality, comprises the following steps:

S1. use spectrometer that the spectrum of described super continuum source is measured, then calculate the first moment of spectral distribution according to measurement result, obtain the spectrum center of gravity;

S2. use respectively area array CCD that near field of light field distribution and the far field distribution of super continuous spectrums light beam are measured, adopt respectively second moment method to calculate near field spot radius and far-field divergence angle to measurement result, the light beam parameters that then calculates described super continuous spectrums light beam is long-pending;

S3. the spectrum center of gravity that obtains take step S1 is constructed desirable Gauss's basic mode light beam as wavelength, and the light beam parameters that calculates described desirable Gauss's basic mode light beam is long-pending;

S4. the super continuous spectrums light beam that step S2 is obtained the long-pending result of the light beam parameters of the long-pending desirable Gauss's basic mode light beam that obtains divided by step S3 of light beam parameters as the evaluation factor for the beam quality of estimating described super continuum source, the beam quality of described super continuum source is estimated.

Preferably, the step of in described step S4, the beam quality of described super continuum source being estimated comprises: compare according to the described evaluation factor and 1, the evaluation factor is the measured light beam of matter near 1 light beam.

Preferably, the step of using respectively area array CCD that near field of light field distribution and the far field distribution of super continuous spectrums light beam are measured in described step S2 comprises:

S21. the super continuous spectrums light beam of super continuum source being exported collimates through catoptron and expands;

S22. carry out light splitting by the broadband Amici prism again and obtain folded light beam and transmitted light beam;

S23. the folded light beam that step S22 is obtained adopts the near field area array CCD to measure the near field of light field distribution, and adopt the far field area array CCD to measure far field to described transmitted light beam and distribute, the distance of the described catoptron of described far field area array CCD distance is greater than the Rayleigh distance of described super continuum source light beam.

Preferably, in described step S23, the distance of the described catoptron of far field area array CCD distance is 10 times of Rayleigh distance of described super continuous spectrums light beam.

Preferably, in described step S1, the spectral measurement ranges of spectrometer comprises the spectral range of whole described super continuum source.

Preferably, the catoptron in described step S2 is the off-axis parabolic mirror of gold-plated film.

The present invention can reach following technique effect: its spectrum center of gravity is calculated in the measurement of super continuum source spectrum, wavelength builds Gauss's basic mode light beam as the reference light beam centered by the spectrum center of gravity, by the measurement to super continuum source near field beamwidth and far-field divergence angle, can carry out the overall evaluation to the beam quality of wide spectrum super continuum source, rather than only the beam quality of some spectral component in light source be estimated and measured.

Description of drawings

Fig. 1 is super continuum source spectral measurement schematic diagram;

Fig. 2 is the structural representation of measurement mechanism embodiment of the present invention;

Fig. 3 is the process flow diagram of measuring method of the present invention;

Fig. 4 is the process flow diagram of measuring near field of light field distribution and far field distribution in measuring method embodiment of the present invention.

Embodiment

Figure 1 shows that super continuum source spectral measurement schematic diagram, in figure, the super continuous spectrums of super continuous spectrums output terminal 1 output is received and its spectrum is measured by spectrometer 2.Performance according to spectrometer 2 in measuring process is selected resolution, and its spectral measurement ranges should cover the spectral range of whole super continuum source, be generally from wavelength corresponding to institute photometry spectrum maximal value with less than the scope between wavelength corresponding to the value of this maximal value 60dB.

Figure 2 shows that an embodiment of super continuum source beam quality measurement mechanism of the present invention.The off-axis parabolic mirror 3, Amici prism 4, near field area array CCD 5 and the far field area array CCD 6 that comprise gold-plated film, and for the treatment of the computing machine 7 of metrical information.The solid line that adds arrow in figure represents light beam.

By the super continuous spectrums light beam of super continuous spectrums output terminal 1 output through catoptron 3 collimator and extenders, afterwards through 4 light splitting of broadband Amici prism, folded light beam is measured the near field of light field distribution by near field area array CCD 5, uses second moment method can calculate light field near field spot size w to measurement result.Transmitted light beam through transmit ten times super continuous spectrums light beam Rayleigh distance namely the z=10L(L shown in figure be super continuous spectrums light beam Rayleigh distance) time, optical field distribution is the far-field distribution of super continuous spectrums light beam, measured by far field area array CCD 6, use second moment method can calculate light field near field spot size to result, it can be obtained far field beam angle of divergence θ divided by transmission range.Then while calculates the entire light quality of super continuum source according to the spectrum center of gravity that the super continuum source spectral distribution calculates.

Fig. 3 and the process flow diagram that Figure 4 shows that measuring method of the present invention.The concrete technical scheme of measuring method of the present invention can further illustrate as follows:

At first use spectrometer that the spectrum of super continuum source is measured, performance according to spectrometer in measuring process is selected resolution, and spectral measurement ranges should cover the spectral range of whole super continuum source, be generally from wavelength corresponding to institute photometry spectrum maximal value with less than the scope between wavelength corresponding to the value of this maximal value 60dB.The spectrum that records is asked first moment, as shown in the formula

$\stackrel{\&OverBar;}{\mathrm{\&lambda;}}=\frac{{\&Integral;}_0^{\&infin;}{P}_{\mathrm{\&lambda;}}\left(\mathrm{\&lambda;}\right)\mathrm{\&lambda;d\&lambda;}}{{\&Integral;}_0^{\&infin;}{P}_{\mathrm{\&lambda;}}\left(\mathrm{\&lambda;}\right)\mathrm{d\&lambda;}}---\left(1\right)$

P in formula _λ(λ) be spectral distribution, λ is wavelength,

Be the spectrum center of gravity.The data that record due to spectrometer are discrete data point, are not successive value, therefore replace integration with summation in calculating, as shown in the formula

$\stackrel{\&OverBar;}{\mathrm{\&lambda;}}=\frac{\underset{\mathrm{\&lambda;}}{\mathrm{\&Sigma;}}{P}_{\mathrm{\&lambda;}}\left(\mathrm{\&lambda;}\right)\mathrm{\&lambda;\&Delta;\&lambda;}}{\underset{\mathrm{\&lambda;}}{\mathrm{\&Sigma;}}{P}_{\mathrm{\&lambda;}}\left(\mathrm{\&lambda;}\right)\mathrm{\&Delta;\&lambda;}}---\left(2\right)$

In formula, Δ λ is the resolution of spectrometer.

Next uses the off-axis parabolic mirror of gold-plated film that the super continuous spectrums light beam of exporting is collimated, then use the area array CCD that whole spectral range is responded near catoptron output, the light field near field distribution of super continuous spectrums light beam being measured, use second moment method to try to achieve the beamwidth of light beam to measurement result.At first concrete grammar for to use first moment to try to achieve the center of gravity of light beam, as shown in the formula

$\stackrel{\&OverBar;}{x}=\frac{{\&Integral;\&Integral;}_{-\&infin;}^{\&infin;}-\mathrm{xP}(x,y)\mathrm{dxdy}}{{\&Integral;\&Integral;}_{-\&infin;}^{\&infin;}P(x,y)\mathrm{dxdy}}---\left(3\right)$

$\stackrel{\&OverBar;}{y}=\frac{{\&Integral;\&Integral;}_{-\&infin;}^{\&infin;}\mathrm{yP}(x,y)\mathrm{dxdy}}{{\&Integral;\&Integral;}_{-\&infin;}^{\&infin;}P(x,y)\mathrm{dxdy}}---\left(4\right)$

In formula, P (x, y) distributes for the distribution of light intensity that is recorded by area array CCD, and x, y are respectively the vertical coordinate axis of area array CCD two.Then use second moment calculate beam radius as shown in the formula

$w_x=2\sqrt{\frac{{\&Integral;\&Integral;}_{-\&infin;}^{\&infin;}{(x-\stackrel{\&OverBar;}{x})}^{2}P(x,y)\mathrm{dxdy}}{{\&Integral;\&Integral;}_{-\&infin;}^{\&infin;}P(x,y)\mathrm{dxdy}}}---\left(5\right)$

$w_y=2\sqrt{\frac{{\&Integral;\&Integral;}_{-\&infin;}^{\&infin;}{(y-\stackrel{\&OverBar;}{y})}^{2}P(x,y)\mathrm{dxdy}}{{\&Integral;\&Integral;}_{-\&infin;}^{\&infin;}P(x,y)\mathrm{dxdy}}}---\left(6\right)$

W in formula _x, w _yBe respectively beam radius.Because the area array CCD measurement result is discrete data, so the integration in following formula all should use summation to replace, as shown in the formula

$\stackrel{\&OverBar;}{x}=\frac{\underset{x}{\mathrm{\&Sigma;}}\underset{y}{\mathrm{\&Sigma;}}\mathrm{xP}(x,y)\mathrm{\&Delta;x\&Delta;y}}{\underset{x}{\mathrm{\&Sigma;}}\underset{y}{\mathrm{\&Sigma;}}\mathrm{\&Sigma;P}(x,y)\mathrm{\&Delta;x\&Delta;y}}---\left(7\right)$

$\stackrel{\&OverBar;}{y}=\frac{\underset{x}{\mathrm{\&Sigma;}}\underset{y}{\mathrm{\&Sigma;}}\mathrm{yP}(x,y)\mathrm{\&Delta;x\&Delta;y}}{\underset{x}{\mathrm{\&Sigma;}}\underset{y}{\mathrm{\&Sigma;P}}(x,y)\mathrm{\&Delta;x\&Delta;y}}---\left(8\right)$

$w_x=2\sqrt{\frac{\underset{x}{\mathrm{\&Sigma;}}\underset{y}{\mathrm{\&Sigma;}}{(x-\stackrel{\&OverBar;}{x})}^{2}P(x,y)\mathrm{\&Delta;x\&Delta;y}}{\underset{x}{\mathrm{\&Sigma;}}\underset{y}{\mathrm{\&Sigma;}}P(x,y)\mathrm{\&Delta;x\&Delta;y}}}---\left(9\right)$

$w_y=2\sqrt{\frac{\underset{x}{\mathrm{\&Sigma;}}\underset{y}{\mathrm{\&Sigma;}}{(y-\stackrel{\&OverBar;}{y})}^{2}P(x,y)\mathrm{\&Delta;x\&Delta;y}}{\underset{x}{\mathrm{\&Sigma;}}\underset{y}{\mathrm{\&Sigma;}}P(x,y)\mathrm{\&Delta;x\&Delta;y}}}---\left(10\right)$

In formula, Δ x, Δ y are respectively the resolution of area array CCD.

By the near field beam radius w that records _xAnd w _yWith the spectrum center of gravity

The Rayleigh distance of definition super continuous spectrums light beam

$L:L=\mathrm{\&pi;}{((w_x+w_y)/2)}^2/\stackrel{\&OverBar;}{\mathrm{\&lambda;}}.$

By the theory of Gauss's basic mode light beam as can be known, can think that with interior light beam collimates in two ends, beam waist position Rayleigh distance, can think the far-field distribution of light beam much larger than the optical field distribution of Rayleigh distance.Therefore use area array CCD in ten times of Rayleigh distances of distance off-axis parabolic mirror, the optical field distribution of super continuous spectrums light beam to be measured respectively.Use second moment method in like manner to try to achieve beam radius, obtain super continuous spectrums far field beam angle of divergence θ by this beamwidth divided by transmission range _xAnd θ _y

The desirable Gauss's basic mode light beam of structure take the spectrum center of gravity as wavelength, as the reference beam of estimating the super continuum source beam quality, the light beam parameters of this light beam is long-pending is

Can calculate by the super continuum source beam radius that measures and far-field divergence angle the evaluation factor of estimating super continuum source entire light quality and (be designated as SC-M ²) as shown in the formula:

$\mathrm{SC}-M_x^2=\frac{\mathrm{\&pi;}}{\stackrel{\&OverBar;}{\mathrm{\&lambda;}}}{w}_x{\mathrm{\&theta;}}_x---\left(11\right)$

$\mathrm{SC}-M_y^2=\frac{\mathrm{\&pi;}}{\stackrel{\&OverBar;}{\mathrm{\&lambda;}}}{w}_y{\mathrm{\&theta;}}_y---\left(12\right)$

Use the beam quality of this factor pair super continuum source to estimate, this value illustrates that more near 1 beam quality is better.

Claims (10)

1. measurement mechanism of be used for measuring the super continuum source beam quality is characterized in that: comprise spectrometer (2), catoptron (3), broadband Amici prism (4), near field area array CCD (5), far field area array CCD (6) and for the treatment of the computing machine (7) of metrical information; Described spectrometer (2) is used for measuring the spectrum of described super continuum source; The super continuous spectrums light beam of described super continuum source output collimates through catoptron (3) and expands, passing through broadband Amici prism (4) carries out light splitting and obtains folded light beam and transmitted light beam again, described folded light beam is measured the near field of light field distribution by near field area array CCD (5), and described transmitted light beam is measured far field by far field area array CCD (6) and distributed; The distance of described far field area array CCD (6) the described catoptron of distance (3) is greater than the Rayleigh distance of described super continuum source light beam; Described computing machine (7) distributes according to the spectrum of described super continuum source, described near field of light field distribution and described far field and calculates measurement result.

2. the measurement mechanism for measuring the super continuum source beam quality according to claim 1 is characterized in that: the distance of described far field area array CCD (6) the described catoptron of distance (3) is 10 times of Rayleigh distance of described super continuum source light beam.

3. the measurement mechanism for measuring the super continuum source beam quality according to claim 1 and 2, it is characterized in that: the spectral measurement ranges of described spectrometer (2) comprises the spectral range of whole described super continuum source.

4. the measurement mechanism for measuring the super continuum source beam quality according to claim 1 and 2, it is characterized in that: described catoptron (3) is the off-axis parabolic mirror of gold-plated film.

5. measuring method of be used for measuring the super continuum source beam quality is characterized in that comprising the following steps:

S1. use spectrometer that the spectrum of described super continuum source is measured, then calculate the first moment of spectral distribution according to measurement result, obtain the spectrum center of gravity;

S2. use respectively area array CCD that near field of light field distribution and the far field distribution of super continuous spectrums light beam are measured, adopt respectively second moment method to calculate near field spot radius and far-field divergence angle to measurement result, the light beam parameters that then calculates described super continuous spectrums light beam is long-pending;

S3. the spectrum center of gravity that obtains take step S1 is constructed desirable Gauss's basic mode light beam as wavelength, and the light beam parameters that calculates described desirable Gauss's basic mode light beam is long-pending;

S4. the super continuous spectrums light beam that step S2 is obtained the long-pending result of the light beam parameters of the long-pending desirable Gauss's basic mode light beam that obtains divided by step S3 of light beam parameters as the evaluation factor for the beam quality of estimating described super continuum source, the beam quality of described super continuum source is estimated.

6. the measuring method for measuring the super continuum source beam quality according to claim 5, it is characterized in that: the step of in described step S4, the beam quality of described super continuum source being estimated comprises: compare according to the described evaluation factor and 1, the evaluation factor is the measured light beam of matter near 1 light beam.

7. according to claim 5 or 6 described measuring methods for measuring the super continuum source beam quality is characterized in that: use respectively area array CCD that the near field of light field distribution of super continuous spectrums light beam and the far field step of measuring that distributes is comprised in described step S2:

S21. the super continuous spectrums light beam of super continuum source being exported collimates through catoptron and expands;

S22. carry out light splitting by the broadband Amici prism again and obtain folded light beam and transmitted light beam;

S23. the folded light beam that step S22 is obtained adopts the near field area array CCD to measure the near field of light field distribution, and adopt the far field area array CCD to measure far field to described transmitted light beam and distribute, the distance of the described catoptron of described far field area array CCD distance is greater than the Rayleigh distance of described super continuum source light beam.

8. the measuring method for measuring the super continuum source beam quality according to claim 7 is characterized in that: in described step S23, the distance of the described catoptron of far field area array CCD distance is 10 times of Rayleigh distance of described super continuous spectrums light beam.

9. the measuring method for measuring the super continuum source beam quality according to claim 8, it is characterized in that: in described step S1, the spectral measurement ranges of spectrometer comprises the spectral range of whole described super continuum source.

10. the measuring method for measuring the super continuum source beam quality according to claim 8, it is characterized in that: the catoptron in described step S2 is the off-axis parabolic mirror of gold-plated film.

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