JPH1123371A - Wavefront measurement method for coherent light source - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To provide a wavefront measuring method for a coherent light source which does not require a complicated optical system and can directly evaluate the wavefront of a beam emitted from a measured coherent light source without passing through an optical system having an aberration. That is the task. SOLUTION: A multimode optical fiber 14 and a single mode optical fiber 14 are each used as a probe on a reference surface 13 at least tens of μm away from the measured coherent light source 1 to sweep the intensity distribution of the measured coherent light source 1. Measuring, based on the intensity distribution measured using the multi-mode optical fiber 14 as a probe and the intensity distribution measured using the single-mode optical fiber 14 as a probe, the inclination angle distribution of the wavefront of the coherent light source 1 to be measured by arithmetic processing And a step of calculating the wavefront of the coherent light source 1 to be measured from the inclination angle distribution of the wavefront by arithmetic processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a simple wavefront measuring method for a coherent light source such as a semiconductor laser, a solid-state laser, and a gas laser.

[0002]

2. Description of the Related Art First, a conventional wavefront measuring method for a coherent light source will be described. Fig. 8 shows Matsubo Technical Re
port (1986.No.6, P14-P17) `` SELF-REFERENCING WAVEF
FIG. 11 is a basic configuration diagram illustrating a configuration of a self-referencing interferometry, which is a conventional coherent light source wavefront measurement method described in “RONT INTERFEROMETER FOR LASER SOURCES”. 8, reference numeral 1 denotes a coherent light source to be measured such as a semiconductor laser, 2 denotes an output beam from the coherent light source 1 to be measured, and 3 denotes an output beam for converting the output beam 2 from the coherent light source 1 to parallel light. The measuring beam collimating lens 4 is a parallel beam converted by the measured beam collimating lens 3, 5 is a beam splitter for separating the parallel beam 4 into two optical paths A and B, and 6 a is a beam splitter 5.
The beams A and 6b transmitted through the optical path A are reflected by the beam splitter 5, and the beams B and 7a guided by the optical path B are mirrors that reflect the beam A6a, and 8a and 8b are the beams A6a and B6b, respectively. A condensing lens 9 for condensing the light is provided with a pinhole 10 having a sufficiently smaller hole diameter than the converging beam provided at the condensing position of the beam 6a.
a and 10b are focused beams A6a and B6b
Collimator lens for converting light into parallel light again, 7b
Are mirrors that reflect the collimated beam B6b,
1 is a beam combiner for combining the collimated beam A6a and the beam B6b, and 12 is a combined beam A
6 is a detector array for detecting the intensity pattern of the beam 6a and the beam B6b.

Next, the operation of the wavefront measuring method using the self-reference interferometry in the above-mentioned conventional example will be described with reference to FIG. As shown in FIG. 8, this measurement system is basically a two-beam interferometer that separates and combines a beam into two light beams, and the type of the interferometer is a Mach-Zehnder interferometer. An output beam 2 emitted from a measured coherent light source 1 is converted into a parallel beam 4 by a measured beam collimating lens 3 and distributed to two optical paths of an interferometer. The beam A6a incident on one optical path A is condensed by the condensing lens 8a and is incident on the pinhole 9. Here this pinhole 9
By setting the diameter of the hole to be sufficiently smaller than the diameter of the Airy disk of the focused beam, the beam emitted from the pinhole 9 becomes an ideal spherical wave. On the other hand, the beam B6b incident on the other optical path B is once condensed by the condenser lens 8b, but becomes a divergent beam as it is. Therefore, the beam B6b maintains the wavefront information of the measured coherent light source 1 as it is. Next, the beam A6a that has become an ideal spherical wave is converted again into a parallel beam by the collimating lens 10a. The beam B6b that maintains the wavefront information of the measured coherent light source 1 as it is is converted again into a parallel beam by the collimating lens 10b. The beam A6a and the beam B6b converted into the parallel beams again are combined by the beam combiner 11 and enter the detector array 12. Therefore, in the detector array 12, interference fringes using the beam A6a as reference light are observed, and the wavefront of the coherent light source 1 to be measured can be obtained from the pattern of the interference fringes. The details are described in "Optical Measurement Handbook" Asakura Shoten and the like.

As described above, the coherent light source 1 to be measured in the detector array 12 in the configuration of FIG.
Is observed, but in reality, aberrations of the measured beam collimating lens 3, the condenser lenses 8a and 8b, and the collimating lenses 10a and 10b are superimposed on this interference fringe pattern. Have been. Therefore, in actual measurement, a correction operation for removing these aberration components in advance is required.

[0005]

As described above, in the conventional method of measuring the wavefront of a coherent light source, the configuration of the measurement system is complicated, and the alignment of the two optical paths constituting the interferometer is required. The light to be measured has passed through many optical components with aberrations before reaching the surface, and it is necessary to correct these.The amount of light must be reduced by passing through a pinhole to generate reference light. There were problems such as a decrease in the contrast of interference fringes.

The present invention has been made to solve such a problem, and does not require a complicated optical system. The wavefront of the beam emitted from the measured coherent light source does not pass through an optical system having an aberration. It is an object of the present invention to obtain a wavefront measurement method of a coherent light source that can be directly evaluated.

[0007]

According to a first aspect of the present invention, there is provided a method for measuring a wavefront of a coherent light source, comprising the steps of: Measuring the intensity distribution of the coherent light source by sweeping the single-mode optical fiber as a probe, the intensity distribution measured using the multi-mode optical fiber as a probe, and the intensity measured using the single-mode optical fiber as a probe A step of calculating the inclination angle distribution of the wavefront of the coherent light source based on the distribution, and a step of calculating the wavefront of the coherent light source by operation processing from the inclination angle distribution of the wavefront.

According to a second aspect of the present invention, there is provided a method of measuring a wavefront of a coherent light source, wherein the multimode optical fiber and the single mode optical fiber are arranged adjacent to each other and their end faces are aligned, and the intensity distribution of the coherent light source is measured. .

According to a third aspect of the present invention, in the wavefront measuring method for a coherent light source, a one-dimensional or two-dimensional multimode optical fiber array is used as the multimode optical fiber, and a one-dimensional or two-dimensional single-mode optical fiber is used as the single-mode optical fiber. The intensity distribution of the coherent light source is measured using an array.

According to a fourth aspect of the present invention, in the method for measuring a wavefront of a coherent light source, the two-dimensional multi-mode optical fiber array and the two-dimensional single-mode optical fiber array are installed adjacent to each other and the end faces thereof are aligned. The intensity distribution of the coherent light source is measured by switching between the array and the two-dimensional single mode optical fiber array.

According to a fifth aspect of the present invention, a method of measuring a wavefront of a coherent light source uses a photodiode as the multimode optical fiber and measures the intensity distribution of the coherent light source.

According to a sixth aspect of the present invention, there is provided a method for measuring a wavefront of a coherent light source, wherein a two-dimensional multi-mode single-mode optical fiber hybrid array in which the multi-mode optical fibers and the single-mode optical fibers are alternately arranged is used as a probe. It measures the intensity distribution of a coherent light source.

According to a seventh aspect of the present invention, in the wavefront measuring method for a coherent light source, a reflectometer for measuring a position of a reflection point is connected behind the single mode optical fiber, and a distance between the end face of the single mode optical fiber and the coherent light source is measured. Is monitored.

According to a wavefront measuring method for a coherent light source according to claim 8, a single mode core is provided at the center of a cross section of an output beam from the coherent light source in a region at least tens of μm away from the coherent light source. Measuring the intensity distribution of the coherent light source by sweeping as a probe a double-core optical fiber having a multi-mode core formed coaxially with the single-mode core around the mode core; and Distribution, based on the intensity distribution measured by the single mode core,
The method includes a step of calculating the inclination angle distribution of the wavefront of the coherent light source by arithmetic processing, and a step of calculating the wavefront of the coherent light source by arithmetic processing from the inclination angle distribution of the wavefront.

According to a ninth aspect of the present invention, a method of measuring a wavefront of a coherent light source uses a one-dimensional or two-dimensional double-core optical fiber array as the double-core optical fiber, and measures the intensity distribution of the coherent light source.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing a measurement system of the wavefront measurement method of the coherent light source according to the first embodiment. FIG.
1, reference numeral 1 denotes a coherent light source to be measured such as a semiconductor laser, a solid-state laser, and a gas laser; 2, a beam emitted from the coherent light source 1 to be measured; Surfaces 14 and 14 are a multi-mode optical fiber (hereinafter referred to as MMF) and a single-mode optical fiber (hereinafter referred to as SMF) having an incident end face on the reference surface 13.

Next, the operation will be described. First, the position of the reference plane 13 is set in the Fraunhofer area. The Fraunhofer region is a region where the light emitted from the measured coherent light source 1 is not subjected to the diffraction effect due to the aperture of the light emitting point and the wavefront shape is in a steady state, and is represented by a distance Z0 satisfying the following equation.

[0018]

(Equation 1)

Here, ωL is the coherent light source 1 to be measured.
Spot size when the mode shape of Gaussian distribution,
λ is the wavelength. Assuming that the measured coherent light source 1 is a semiconductor laser, ωL is about 1 μm. If the wavelength is about 1 to 2 μm, the Fraunhofer region becomes several tens μm or more according to the equation (1).

In FIG. 1, a coherent light source 1 to be measured
Is the actual intensity distribution on the X axis on the reference plane 13 of P
_L (x), MMF and measurement at the time of sweeping the X-axis using the SMF14 results each P _M (x), a relationship of the following equation by placing the P _S (x).

[0021]

(Equation 2)

Here, ηM is the coupling efficiency to the MMF 14,
ηS is the coupling efficiency to SMF14.

First, let us look at ηM. The condition for coupling light to the MMF 14 is that light enters the core, which is an effective aperture, within the maximum incident angle. Therefore, in FIG. 1, the angle ＭＭ at which the MMF 14 looks at the measured coherent light source 1 ψ
Is within the maximum incident angle of the fiber, ηM takes a constant value regardless of x. Therefore, in this case, MMF14
Is a distribution that reflects the actual intensity distribution on the reference surface 13 of the measured coherent light source 1.

Next, let us look at ηS. FIG. 2 shows a combined model of the output beam 2 from the measured coherent light source 1 and the SMF 14 at the position x on the reference plane 13. Here, the electric field distribution in the reference surface 13 E ₁₀ is to be measured coherent light source 1, E ₂₀ is an electric field distribution in the reference surface 13 of the SMF 14, .phi.1 phase distribution in the reference surface 13 to be measured coherent light source 1, .phi.2 Is the phase distribution on the reference surface 13 of the SMF 14, and F _Z is the wavefront distribution of the coherent light source 1 to be measured. At this time, the coupling efficiency ηS of light to SM14F is expressed by the following equation.

[0025]

(Equation 3)

Here, it is assumed that the wavefront of the coherent light source 1 to be measured changes gradually with respect to the change in the waveguide mode of the SMF 14. In other words, it is assumed that the wavefront of the coherent light source 1 to be measured is flat in the local region where the waveguide mode of the SMF 14 exists. Under this assumption, the coupling between the outgoing beam 2 from the coherent light source 1 to be measured and the SMF 14 is expressed as a combination of plane waves having two intersection angles θ in a portion where the guided mode of the SMF 14 exists.

Next, since the electric field distribution of the guided mode of the SMF 14 is well approximated by a Gaussian distribution, it is assumed to be a Gaussian distribution. On the other hand, it is assumed that the electric field distribution of the measured coherent light source 1 on the reference surface 13 is an arbitrary distribution. However, it is assumed that the change in the electric field distribution of the measured coherent light source 1 on the X axis is sufficiently smaller than the change in the electric field distribution of the SMF 14. Further, it is assumed that the electric field distribution of the measured coherent light source 1 is constant in a region where the guided mode of the SMF 14 exists. By introducing the above assumption, the coupling efficiency ηS is expressed by the following equation.

[0028]

(Equation 4)

Here, κ is the wave number, ωF is the spot size of the SMF 14, and C is a constant and is expressed by the following equation.

[0030]

(Equation 5)

Here, Δx is a region where the waveguide mode of the SMF 14 exists, and is an integration region in the equation (4). As described above, the following expression is obtained from Expressions (2), (3) and (7).

[0032]

(Equation 6)

Here, the position on the X-axis where θ = 0 is X0
Assuming that

[0034]

(Equation 7)

Can be expressed as follows. Therefore, equations (9) and (10)
The following relationship is obtained from:

[0036]

(Equation 8)

Here, P _M (x) 'is a normalized intensity distribution measured by the MMF 14, and P _S (x)' is a normalized intensity distribution measured by the SMF 14.

From Expression (11), the local inclination of the wavefront θ on the reference surface 13 of the coherent light source 1 to be measured is expressed by a very simple relational expression such as the following expression.

[0039]

(Equation 9)

[0040] Here, because the wavefront inclination θ of is given by the derivative of the wavefront distribution F _Z, the wavefront distribution F _Z is obtained from the following equation.

[0041]

(Equation 10)

FIG. 3 shows the coordinates of the wavefront distribution. The wavefront distribution is defined by a displacement from the reference plane 13. In addition, the above equation (13)
Is calculated by simple numerical calculation from the distribution data of the local wavefront inclination θ obtained by the equation (12).

On the other hand, the wavefront distribution of an ideal spherical wave is expressed by the following equation.

[0044]

[Equation 11]

Since the displacement of the actual wavefront from the ideal spherical surface (reference spherical surface) is the wavefront aberration, the expression (13) -the expression (14) is obtained.
Thus, the wavefront aberration distribution of the measured coherent light source 1 can be obtained. Note that the wavefront aberration measurement resolution of the above-described measurement method is substantially determined by the mode field diameter of the SMF 14 to be used. For example, since the mode field diameter of a normal SMF in the 1.3 μm band is about 10 μm, a small value of about 10 μm is obtained as the resolution of wavefront aberration measurement by this measurement method.

As described above, according to this embodiment,
The measured value using a multimode optical fiber as a probe, which is the result of reflecting the actual intensity distribution on the measurement surface (reference surface) of the coherent light source, and the result, reflecting both the actual intensity distribution and the inclination of the local wavefront The intensity distribution can be removed by a simple calculation from the ratio of the measured values using a certain single-mode optical fiber as a probe, and the inclination distribution of the wavefront can be obtained.

Embodiment 2 FIG. 4 is a configuration diagram showing a measurement system of the wavefront measurement method of the coherent light source according to the second embodiment. In FIG. 4, 15 is the MMF and 16 is this MMF.
15 and the incident end face were aligned and fixed adjacent to each other.
F, 1, 2, and 13 are the same as those in FIG.

As described in the first embodiment, in the wavefront measuring method of the coherent light source according to the present invention, the wavefront aberration at the position is obtained from the ratio of the measured value in the MMF to the measured value in the SMF. Therefore, it is necessary to match the coordinates of the measurement value in the MMF and the measurement value in the SMF. FIG.
By fixing the MMF 15 and the SMF 16 adjacent to each other as shown in (1), the relative positional relationship between them can be kept constant. Therefore, MMF15 and SMF16
If the positional relationship is obtained in advance, the coordinates of the measured values can be easily matched with high accuracy.

It should be noted that the relative positions of the MMF and the SMF can be easily set with high accuracy by using the high accuracy of the outer diameter of the cladding portion and the high coaxial accuracy of the core portion relative to the outer periphery of the cladding portion. I can do it. Further, the relative position can be easily set with high accuracy by using two V grooves provided in parallel.

Embodiment 3 FIG. 5 is a configuration diagram showing a measurement system of the wavefront measurement method of the coherent light source according to the third embodiment. In FIG. 5, 17 is a one-dimensional or two-dimensional array of MMF or SMF, and 1, 2, and 13 are the same as those in FIG.
In this manner, by arraying the MMF and the SMF, the amount of sweep of the optical fiber can be reduced. In particular, in the case of a two-dimensional array, respective intensity distribution data on the reference plane can be obtained instantaneously without sweeping.

Embodiment 4 FIG. FIG. 6 is a configuration diagram showing a measurement system of the wavefront measurement method of the coherent light source according to the fourth embodiment. In FIG. 6, reference numeral 18 denotes a one-dimensional or two-dimensional array of MMF, and 19 denotes a one-dimensional or two-dimensional array of SMF which is arranged adjacent to the one-dimensional or two-dimensional array 18 of MMF and is installed adjacent thereto. Is the same as FIG. Thus, a one-dimensional or two-dimensional array 18 of MMFs
By making the one-dimensional or two-dimensional array 19 of SMF and SMF adjacent and fixed, the relative positional relationship between them can be kept constant. Therefore, if these positional relationships are obtained in advance, the coordinates of the measured values obtained by the two can be corrected with high precision and easily matched. In addition, by measuring the one-dimensional or two-dimensional array 18 of the MMF and the one-dimensional or two-dimensional array 19 of the SMF in advance and switching them, an efficient measurement without extra positioning work can be realized.

Embodiment 5 FIG. 1 and 4,
In the embodiment of the invention shown in FIGS. 5 and 6, a photodiode may be used instead of the MMF. The maximum incident angle of the MMF is usually about 30 degrees. On the other hand, the maximum incident angle of the photodiode is usually 45 degrees or more. First, in the description of the first embodiment, if the angle ψ at which the MMF looks at the measured coherent light source 1 in FIG. It has been described that the distribution directly reflects the intensity distribution on the surface. Therefore, since the maximum incident angle of the photodiode is larger than that of the MMF, a measurement value that directly reflects the intensity distribution up to a position further away from the optical axis can be obtained. Further, the wavefront of a coherent light source having a larger emission angle can be measured.

Embodiment 6 FIG. FIG. 7 is a sectional view of a probe used for measuring the wavefront of the coherent light source according to the sixth embodiment. In FIG. 7, 15 is MMF, 16 is MMF1
5 and SMF alternately arranged, 20 are MMF15 and SMF
Reference numeral 16 denotes an MMF / SMF hybrid array alternately arranged in two dimensions. By setting the end face of such an MMF / SMF hybrid array 20 to the reference plane 13 shown in FIG.
Intensity distribution measurement data in the MF are collected two-dimensionally at every other measurement point. Therefore, wavefront measurement data can be obtained by interpolating these data with each other and performing the calculation shown in equation (11). As a result, the measurement can be instantly terminated without sweeping the probe and without switching.

Embodiment 7 FIG. In the first embodiment of the present invention shown in FIG. 1, a double-core optical fiber having a single-mode waveguide core at the center and a multi-mode waveguide core around the core is used as a measurement probe. If the single mode guided light and the multimode guided light are extracted separately, the intensity distribution measurement data in MMF and SMF
The coordinates of the intensity distribution measurement data can always be automatically matched.

Embodiment 8 FIG. In the first embodiment of the present invention shown in FIG. 1, a double-core optical fiber having a single-mode waveguide core at the center and a multi-mode waveguide core around the core is used as a measurement probe. By using a two-dimensional or two-dimensional array, the amount of sweep of the optical fiber can be reduced. In particular, by using a two-dimensional array of double-core optical fibers, the data in which the coordinates of the intensity distribution measurement data in the MMF and the intensity distribution measurement data in the SMF completely match can be instantaneously obtained without sweeping the measurement probe at all. Can be obtained.

Embodiment 9 FIG. 1 and 4,
In the embodiments of the invention shown in 5, 6, and 7, the distance Z0 between the coherent light source 1 to be measured and the reference plane 13 can be easily obtained by connecting a reflectometer for measuring the position of the reflection point behind at least one SMF. Can be measured, whereby the radius of curvature Z0 of the reference spherical surface can be obtained. A commercially available reflectometer can be used (for example, HP 8504B).

[0057]

As described above, according to the first aspect of the present invention,
Since only the multi-mode optical fiber and the single-mode optical fiber need to be used as the optical components, a complicated optical system is unnecessary, and since no interferometer is used, complicated and precise optical path axis alignment is unnecessary. Wavefront measurement system can be easily set. In addition, it can be set compactly without taking up space.

According to the second aspect of the present invention, since the multi-mode optical fiber and the single-mode optical fiber are disposed adjacent to each other and aligned with the end faces, the coordinates of the measured values can be easily corrected and matched. As a result, a more accurate wavefront aberration measurement result can be obtained.

According to the third aspect of the present invention, a one-dimensional or two-dimensional multi-mode optical fiber array is used instead of the multi-mode optical fiber, and a one-dimensional or two-dimensional single mode is used instead of the single-mode optical fiber. Since the optical fiber array is used, the amount of sweep of the optical fiber can be reduced, or the intensity distribution data on the reference surface can be obtained instantaneously without sweeping, and the wavefront aberration can be measured more quickly.

According to the fourth aspect of the present invention, the two-dimensional multi-mode optical fiber array and the two-dimensional single-mode optical fiber array are installed adjacent to each other and aligned with the end faces. 2 above
Since the intensity distribution of the coherent light source is measured by switching the dimensional single mode optical fiber array, the coordinates of the measured values can be corrected and matched with high accuracy, and a more accurate wavefront aberration measurement result can be obtained, The intensity distribution data on the reference surface can be obtained instantaneously without sweeping the optical fiber, and the wavefront aberration can be measured more quickly.

According to the fifth aspect of the present invention, since the photodiode is used instead of the multimode optical fiber, a measured value reflecting the intensity distribution as it is can be obtained up to a position further away from the optical axis, and the light emission can be further improved. The wavefront aberration of a coherent light source with a large angle can be measured.

According to the invention of claim 6, since the calculation is performed by interpolating the intensity distribution measurement data in the multi-mode optical fiber and the intensity distribution measurement data in the single-mode optical fiber, the probe can be used. The measurement can be instantaneously terminated without any sweeping or switching.

According to the seventh aspect of the present invention, a reflectometer for measuring the position of a reflection point is connected to the rear of the single mode optical fiber, and the distance between the end face of the single mode optical fiber and the coherent light source is monitored. So that the radius of curvature of the reference spherical surface can be easily obtained,
A more accurate measurement result of the wavefront aberration is obtained.

According to the invention of claim 8, a double core optical fiber having a single mode core at the center and a multimode core formed coaxially with the single mode core around the single mode core is used as a probe. Since it is used, the coordinates of the intensity distribution measurement data of the multimode core and the coordinates of the intensity distribution measurement data of the single mode core can always be automatically matched, and no coordinate correction is required.

According to the ninth aspect of the present invention, since a one-dimensional or two-dimensional double-core optical fiber array is used instead of the double-core optical fiber, the intensity distribution measurement data in the multi-mode core and the intensity in the single-mode core are used. The coordinates of the distribution measurement data can always be automatically matched, and no coordinate correction is required, and the amount of optical fiber sweep can be reduced. In particular, by using a two-dimensional double-core optical fiber array, the measurement can be completed instantaneously without sweeping the probe and without switching.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a measurement system of a wavefront measurement method of a coherent light source according to a first embodiment of the present invention.

FIG. 2 shows a coherent light source 1 at a position x on a reference plane.
FIG. 6 is a combined model diagram of an outgoing beam 2 from the SMF and SMF.

FIG. 3 is a diagram showing coordinates of a wavefront distribution.

FIG. 4 is a configuration diagram illustrating a measurement system of a wavefront measurement method of a coherent light source according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram showing a measurement system of a wavefront measurement method of a coherent light source according to a third embodiment of the present invention.

FIG. 6 is a configuration diagram illustrating a measurement system of a wavefront measurement method of a coherent light source according to a fourth embodiment of the present invention.

FIG. 7 is a configuration diagram illustrating a measurement system of a wavefront measurement method of a coherent light source according to a sixth embodiment of the present invention.

FIG. 8 is a basic configuration diagram showing a configuration of a self-referencing interferometry, which is a conventional coherent light source wavefront measuring method.

[Explanation of symbols]

Reference Signs List 1 Coherent light source to be measured, 2 Emitted beam from coherent light source 1 to be measured, 3 Beam collimated lens to be measured, 4 Parallel beam, 5 Beam splitter, 6a
Beam A guided to optical path A, 6b Beam B guided to optical path B, 7a Mirror that reflects beam A 6a, 8a,
8b condenser lens, 9 pinholes, 10a, 10b
Collimating lens, 7b mirror for reflecting beam B6b, 11 beam combiner, 12 detector array, 1
3 reference plane (observation plane), 14 multimode optical fiber and single mode optical fiber, 15 multimode optical fiber, 16 single mode optical fiber, 17 one-dimensional or two-dimensional array of multimode optical fiber or single mode optical fiber, 18 One-dimensional or two-dimensional array of multi-mode optical fiber, 19 One-dimensional or two-dimensional array of single-mode optical fiber, 20 MMF / SMF
Hybrid array.

Claims (9)

[Claims] At least several tens of μm from a coherent light source.
measuring the intensity distribution of the coherent light source by sweeping a multi-mode optical fiber and a single-mode optical fiber respectively as probes in a section of the output beam from the coherent light source at a distance of m A step of calculating an inclination angle distribution of the wavefront of the coherent light source by an arithmetic processing based on the intensity distribution measured using the optical fiber as a probe and the intensity distribution measured using the single-mode optical fiber as a probe; Obtaining the wavefront of the coherent light source from the distribution by arithmetic processing. 2. The wavefront of a coherent light source according to claim 1, wherein said multimode optical fiber and said single mode optical fiber are installed adjacent to each other and their end faces are aligned, and the intensity distribution of said coherent light source is measured. Measurement method. 3. A one-dimensional or two-dimensional multi-mode optical fiber array is used as the multi-mode optical fiber, a one-dimensional or two-dimensional single-mode optical fiber array is used as the single-mode optical fiber, and the intensity distribution of the coherent light source is determined. 3. The method of measuring a wavefront of a coherent light source according to claim 1, wherein each of the measurements is performed. 4. The two-dimensional multi-mode optical fiber array and the two-dimensional single-mode optical fiber array are arranged adjacent to each other and are aligned, and the two-dimensional multi-mode optical fiber array and the two-dimensional single-mode optical fiber array are arranged. The method of measuring a wavefront of a coherent light source according to claim 3, wherein the intensity distribution of the coherent light source is measured by switching. 5. The method of measuring a wavefront of a coherent light source according to claim 1, wherein a photodiode is used as the multimode optical fiber, and an intensity distribution of the coherent light source is measured. 6. The method according to claim 1, wherein a two-dimensional multi-mode single-mode optical fiber hybrid array in which the multi-mode optical fibers and the single-mode optical fibers are alternately arranged is used as a probe to measure the intensity distribution of the coherent light source. The method for measuring a wavefront of a coherent light source according to claim 1 or 2. 7. A reflection meter for measuring a position of a reflection point is connected to the rear of the single mode optical fiber, and a distance between an end face of the single mode optical fiber and the coherent light source is monitored. Or the wavefront measuring method of the coherent light source according to 2. 8. At least several tens μm from a coherent light source
a single-mode core at the center in the cross section of the output beam from the coherent light source at a distance of m
Measuring the intensity distribution of the coherent light source by sweeping a double-core optical fiber having a multi-mode core formed coaxially with the single-mode core around the single-mode core as a probe; Calculating the inclination angle distribution of the wavefront of the coherent light source by arithmetic processing based on the calculated intensity distribution and the intensity distribution measured by the single-mode core; and calculating the inclination angle distribution of the coherent light source from the inclination angle distribution of the wavefront by arithmetic processing. Obtaining a wavefront. A method for measuring a wavefront of a coherent light source, comprising: 9. The method for measuring a wavefront of a coherent light source according to claim 8, wherein a one-dimensional or two-dimensional double-core optical fiber array is used as the double-core optical fiber, and the intensity distribution of the coherent light source is measured.