JPH10325970A - Broad-band high-speed wavelength conversion method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the alignment to a phase matching angle with respect to a laser beam and to enable high-speed higher modulation conversion without rotating a nonlinear optical crystal by controlling the incident angle of the laser beam made incident on the nonlinear optical crystal according to the dispersion characteristics of a dispersion element and the condensing characteristics of a condenser element. SOLUTION: The exciting laser beam is refracted in the optical path according to the wavelength by a first prism 12 which is the dispersion element, by which the optical path of the beam is divided by each wavelength of the exciting laser beam. The incident angle on the nonlinear optical crystal 10 is adjusted so as to be optimized at respective wavelengths by a first cylindrical concave surface mirror 14 which is the condenser element. On the other hand, the converted laser beam emitted from the nonlinear optical crystal 10 is adjusted in the optical path and is made incident on a second prism 18 by a second cylindrical concave surface mirror 16 which is the condenser element. The laser beam is refracted and is emitted through a prescribed optical path. The alignment of the nonlinear optical crystal 10 to the phase matching angle with respect to the incident laser beam is made possible without rotating the nonlinear optical crystal according to this wavelength conversion method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for broadband high-speed wavelength conversion, and more particularly to a method and an apparatus for broadband high-speed wavelength conversion of laser light using a nonlinear optical crystal. Efficiently performs harmonic conversion that satisfies the phase matching condition in the nonlinear optical crystal, regardless of the wavelength of the excitation laser light, corresponding to the wavelength change of the laser (excitation laser light) incident on The present invention relates to a broadband high-speed wavelength conversion method and apparatus capable of performing the method.

[0002]

2. Description of the Related Art As a conventional wavelength conversion technique for laser light, for example, a harmonic conversion method in which an excitation laser light is made to enter a nonlinear optical crystal and a harmonic of the excitation laser light is emitted from the nonlinear optical crystal as converted laser light. By
A nonlinear wavelength conversion method for performing wavelength conversion of pump laser light is known, and in such a nonlinear wavelength conversion method, it is necessary to satisfy a phase matching condition between the pump laser light and the nonlinear optical crystal.

As a method for satisfying the phase matching condition, the nonlinear optical crystal is rotated manually or by a motor so that the nonlinear optical crystal is positioned at a phase matching angle satisfying the phase matching condition with respect to the excitation laser beam. There is a method of adjusting the incident angle of the excitation laser beam to the nonlinear optical crystal (see FIG. 1).

The above-mentioned phase matching condition is determined by the required wavelength of the converted laser light emitted from the nonlinear optical crystal and the excitation laser light incident on the nonlinear optical crystal required for the required wavelength of the converted laser light. Given a wavelength, it is uniquely determined. Therefore, when trying to change the wavelength of the converted laser light emitted from the nonlinear optical crystal, it is necessary to change the wavelength of the excitation laser light incident on the nonlinear optical crystal every time the wavelength of the converted laser light is changed. In addition, the nonlinear optical crystal has to be positioned at a phase matching angle with respect to the excitation laser light by rotating the nonlinear optical crystal manually or by a motor.

However, in the method of rotating the nonlinear optical crystal manually or with a motor, it takes time to position the nonlinear optical crystal at the phase matching angle with respect to the excitation laser beam, and high-speed harmonic conversion cannot be performed. There was a problem.

Further, when the nonlinear optical crystal is rotated to be positioned at the phase matching angle, the beam of the excitation laser beam shifts. For this reason, there is a problem that a correction device for correcting such a deviation of the beam of the excitation laser light is required separately.

Further, when the nonlinear optical crystal is rotated to be positioned at the phase matching angle, when a beam having a wide spectrum width is used as the excitation laser light, a wavelength component deviating from the phase matching condition occurs. There is a problem that high conversion efficiency cannot be obtained.

In the method of rotating the nonlinear optical crystal so as to be positioned at the phase matching angle, a beam including a plurality of wavelengths as excitation laser light cannot be simultaneously incident on the nonlinear optical crystal, and the wavelength can be simultaneously converted. There was a problem that the wavelength was limited to only one wavelength.

It is possible to adjust the incident angle of the excitation laser beam on the nonlinear optical crystal without rotating the nonlinear optical crystal manually or with a motor, thereby solving the above-mentioned conventional problems. As an apparatus, for example, an apparatus as shown in FIG. 2 has been conventionally proposed.

In the apparatus shown in FIG. 2, the excitation laser light is made incident on the nonlinear optical crystal via two prisms (first prism and second prism) as dispersion elements and one lens. Things.

That is, in the apparatus shown in FIG. 2, the optical path is separated for each wavelength of the excitation laser light by two prisms (first prism and second prism), and the light is separated by the dispersion characteristics of the prism and the light-collecting characteristics of the lens. The angle of incidence on the nonlinear optical crystal is determined.

Here, the wavelength of the pump laser light is λ (λ
Can take any value such as λ ₁ , λ _center , λ _{2 ,.} ), The incident angle θ ′ (λ) of the excitation laser light to the nonlinear optical crystal (when λ = λ ₁ , θ ′ (λ) is θ ′ (λ ₁ ), and when λ = λ _center θ ′ (λ) is θ ′ (λ _center ), and when λ = λ ₂ , θ ′ (λ) is θ ′ (λ ₂ ). The angle, that is, the phase adjustment angle suitable for the phase matching condition is θ (λ) (when λ = λ ₁ , θ (λ) is θ (λ ₁ ), and when λ = λ _center , θ
(Λ) is θ (λ _center ), and when λ = λ ₂ , θ
(Λ) is θ (λ ₂ ). (1) Incident angle β to the first prism (2) Apex angle A of the first and second prisms (3) Materials (dispersion characteristics) of the first and second prisms
n (λ) (4) Adjustment of five parameters of the distance d between the first prism and the second prism (5) the focal length f of the lens.

That is, in the apparatus shown in FIG. 2, it is necessary to adjust θ ′ (λ) to θ (λ) by using only five parameters. There was a problem that θ ′ (λ) could not be adjusted to θ (λ) with accuracy.

In the apparatus shown in FIG. 2, when a parallel beam is used as the excitation laser light, the excitation laser light is condensed on the nonlinear optical crystal (see FIG. 3). Although it is possible to use a parallel beam having a low power as a laser beam, there is a problem that a nonlinear optical crystal may be damaged if a parallel beam having a high power is used as an excitation laser beam.

Further, in the conventional technique, there is a problem that the converted laser lights of different wavelengths emitted from the nonlinear optical crystal cannot be coaxially overlapped.

[0016]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned various problems of the prior art, and has as its object to rotate a nonlinear optical crystal without rotating it. It is an object of the present invention to provide a wide-band high-speed wavelength conversion method and a device capable of performing high-speed harmonic conversion by enabling alignment with a phase matching angle with respect to incident laser light.

Further, according to the present invention, since the nonlinear optical crystal is not rotated to be positioned at the phase matching angle, even when a beam having a wide spectral width is used as laser light incident on the nonlinear optical crystal, It is an object of the present invention to provide a broadband high-speed wavelength conversion method and a device therefor that can obtain high conversion efficiency without generating a wavelength component deviating from a phase matching condition.

Further, the present invention enables a beam including a plurality of wavelengths to be simultaneously incident on a nonlinear optical crystal as a laser beam to be incident on the nonlinear optical crystal, and at the same time, a broadband high-speed wavelength conversion capable of wavelength conversion of multiple wavelengths. It is intended to provide a method and an apparatus thereof.

Another object of the present invention is to provide a broadband high-speed wavelength conversion method and an apparatus therefor, which can set the incident angle of laser light incident on the nonlinear optical crystal with high precision to a phase matching angle. Things.

Another object of the present invention is to provide a wide-band high-speed wavelength conversion method and apparatus capable of using a high-power parallel beam as laser light incident on a nonlinear optical crystal.

It is another object of the present invention to provide a broadband high-speed wavelength conversion method and apparatus capable of coaxially superposing converted laser lights of different wavelengths emitted from a nonlinear optical crystal.

[0022]

According to a first aspect of the present invention, there is provided a broadband high-speed wavelength conversion method according to the present invention. In the broadband high-speed wavelength conversion method of performing wavelength conversion of light, laser light is incident on the dispersion element, the laser light is emitted from the dispersion element by separating the optical path corresponding to the wavelength change of the laser light, The laser light emitted from the dispersive element is incident on the condensing element, reflected and emitted according to the condensing characteristics of the condensing element, and the laser light emitted from the condensing element is incident on the nonlinear optical crystal. The incident angle of the laser beam incident on the nonlinear optical crystal is controlled according to the dispersion characteristics of the dispersive element and the condensing characteristics of the condensing element.

Therefore, according to the broadband high-speed wavelength conversion method according to the first aspect of the present invention, the nonlinear optical crystal can be positioned at the phase matching angle with respect to the incident laser light without rotating. Thus, the above-mentioned problems can be completely solved. Here, the laser light incident on the dispersion element may include a plurality of different wavelength components as in the broadband high-speed wavelength conversion method according to the second aspect of the present invention.

According to a third aspect of the present invention, there is provided a wide-band high-speed wavelength conversion method in which a laser beam is incident on a nonlinear optical crystal and the wavelength of the laser beam is converted by harmonic conversion. The wavelength-converted laser light emitted from the nonlinear optical crystal is incident on the light-collecting element, and is emitted according to the light-collecting characteristics of the light-collecting element.
The laser light emitted from the light-collecting element is incident on the dispersion element, emitted according to the dispersion characteristics of the dispersion element, and collected according to the light-collection properties of the light-collection element and the dispersion characteristics of the dispersion element. The laser light emitted from the dispersion element is coaxially overlapped.

Therefore, according to the broadband high-speed wavelength conversion method according to the third aspect of the present invention, laser beams of different wavelengths emitted from the nonlinear optical crystal can be coaxially superposed.

Here, the dispersive element can be a prism as in the broadband high-speed wavelength conversion method according to the present invention.

The dispersive element can be a diffraction grating as in the broadband high-speed wavelength conversion method according to the present invention.

Further, the light-collecting element may be a concave mirror as in the broadband high-speed wavelength conversion method according to claim 6 of the present invention. When the light-collecting element is a concave mirror, the curvature of the concave mirror becomes the light-collecting characteristic of the light-collecting element.

Further, the light-collecting element can be a lens as in the broadband high-speed wavelength conversion method according to the present invention.

The broadband high-speed wavelength converter according to claim 8 of the present invention is directed to a broadband high-speed wavelength converter for performing laser light incident on a nonlinear optical crystal and performing wavelength conversion of the laser light by harmonic conversion. A dispersive element that injects laser light, separates the optical path of the laser light according to the wavelength change of the laser light, and emits the laser light. And a laser beam emitted from the light-collecting element is incident at an incident angle controlled according to the dispersion characteristics of the light-dispersing element and the light-collecting characteristics of the light-collecting element. And an optical crystal.

Therefore, according to the broadband high-speed wavelength converter according to the eighth aspect of the present invention, the nonlinear optical crystal can be positioned at a phase matching angle with respect to the incident laser light without rotating. Thus, the above-mentioned problems can be completely solved. Here, the laser beam incident on the dispersion element may include a plurality of different wavelength components as in the broadband high-speed wavelength converter according to the ninth aspect of the present invention.

A broadband high-speed wavelength converter according to a tenth aspect of the present invention is a broadband high-speed wavelength converter for injecting laser light into a nonlinear optical crystal and performing wavelength conversion of the laser light by harmonic conversion. A light-condensing element that emits wavelength-converted laser light emitted from the nonlinear optical crystal and emits light according to light-collecting characteristics, and a laser light emitted from the light-collecting element enters light according to dispersion characteristics. And a dispersion element that emits light. The laser light emitted from the dispersion element is coaxially overlapped according to the light collection characteristics of the light collection element and the dispersion characteristics of the dispersion element.

Therefore, according to the broadband high-speed wavelength converter according to the tenth aspect of the present invention, laser beams of different wavelengths emitted from the nonlinear optical crystal can be coaxially superposed.

Here, the dispersive element can be a prism as in the broadband high-speed wavelength converter according to claim 11 of the present invention.

Further, the dispersive element can be a diffraction grating as in the broadband high-speed wavelength converter according to the twelfth aspect of the present invention.

Further, the light-collecting element may be a concave mirror, as in a broadband high-speed wavelength converter according to the present invention. When the light-collecting element is a concave mirror, the curvature of the concave mirror becomes the light-collecting characteristic of the light-collecting element.

Further, the light-collecting element may be a lens as in the broadband high-speed wavelength converter according to the present invention.

According to a fifteenth aspect of the present invention, there is provided a broadband high-speed wavelength conversion method in which a laser beam is incident on a nonlinear optical crystal and the wavelength of the incident laser beam is converted by harmonic conversion. In the method, a laser beam is incident on a first dispersion element, and the incident laser beam is separated by refracting an optical path in accordance with a wavelength change, and is separated from the first dispersion element, and is emitted from the first dispersion element. The laser light emitted from the dispersive element is incident on the second dispersive element, and the incident laser light is emitted from the second dispersive element as a parallel beam by refracting the optical path corresponding to the wavelength change. The parallel beam laser light emitted from the second dispersion element is incident on a parabolic mirror, and the incident parallel beam laser light is focused on the same point by the parabolic mirror. And the laser light condensed and reflected from the parabolic mirror at the same point is incident on the nonlinear optical crystal, and the dispersion characteristics of the first dispersion element and the second dispersion element and the parabola The incident angle of the laser beam incident on the nonlinear optical crystal is controlled in accordance with the light condensing characteristics of the plane mirror.

Therefore, according to the broadband high-speed wavelength conversion method according to the fifteenth aspect of the present invention, the nonlinear optical crystal can be positioned at the phase matching angle with respect to the incident laser light without rotating. Thus, the above-mentioned problems can be completely solved.

Here, the laser beam incident on the first dispersion element may include a plurality of different wavelength components.

According to a sixteenth aspect of the present invention, there is provided a broadband high speed wavelength conversion method in which a laser beam is incident on a nonlinear optical crystal and the wavelength of the incident laser beam is converted by harmonic conversion. In the method, the wavelength-converted laser light emitted from the nonlinear optical crystal is incident on a parabolic mirror, reflected as a parallel beam by the parabolic mirror, and reflected as a parallel beam from the parabolic mirror. The laser light is incident on the first dispersion element, the laser light incident as a parallel beam is refracted in the optical path corresponding to the wavelength change and emitted, and the laser light emitted from the first dispersion element is emitted to the first dispersion element. 2, the incident laser light is refracted in the optical path corresponding to the wavelength change and emitted, and the light-collecting characteristics of the parabolic mirror and the first dispersion element and the second dispersion element Minute Depending on the dispersion characteristics of the element is obtained by so as to overlap the laser beam emitted from the second dispersion element coaxially.

Therefore, according to the broadband high-speed wavelength conversion method of the present invention, laser beams of different wavelengths emitted from the nonlinear optical crystal can be coaxially superposed.

Here, the first dispersion element and the second dispersion element can be prisms.

Further, the first dispersion element and the second dispersion element can be diffraction gratings.

A broadband high-speed wavelength converter according to a seventeenth aspect of the present invention is a broadband high-speed wavelength converter that performs laser light incident on a nonlinear optical crystal and performs wavelength conversion of the incident laser light by harmonic conversion. In the apparatus, the laser beam is incident, the incident laser beam is separated and emitted by refracting an optical path corresponding to a wavelength change, and the laser beam is emitted from the first dispersion element. A second dispersive element that emits a laser beam incident thereon, refracts the incident laser beam in accordance with a wavelength change, and emits the beam as a parallel beam, and a parallel beam emitted from the second dispersive element. A parabolic mirror that reflects the laser beam of the incident parallel beam at the same point and reflects it, and is focused and reflected from the parabolic mirror at the same point A non-linear optical crystal for entering a laser beam at an incident angle controlled according to the dispersion characteristics of the first dispersion element and the second dispersion element and the condensing characteristic of the parabolic mirror; It was done.

Therefore, according to the broadband high-speed wavelength converter according to claim 17 of the present invention, it is possible to align the nonlinear optical crystal with the incident laser light at a phase matching angle without rotating the crystal. Thus, the above-mentioned problems can be completely solved.

Here, the laser beam incident on the first dispersion element may include a plurality of different wavelength components.

A broadband high-speed wavelength converter according to claim 18 of the present invention performs a wide-band high-speed wavelength conversion in which a laser beam is incident on a nonlinear optical crystal and the wavelength of the incident laser beam is converted by harmonic conversion. In the device, the wavelength-converted laser light emitted from the nonlinear optical crystal is incident, a parabolic mirror that reflects as a parallel beam, and the laser light that is reflected as a parallel beam from the parabolic mirror is incident. A first dispersion element that refracts an optical path of a laser beam incident as a parallel beam in accordance with a wavelength change and emits the laser light; and a laser beam emitted from the first dispersion element is incident and incident. A second dispersion element that refracts an optical path in response to a wavelength change and emits the laser light,
Laser light emitted from the second dispersion element is coaxially overlapped according to the light-collecting characteristics of the parabolic mirror and the dispersion characteristics of the first dispersion element and the second dispersion element. It is.

Therefore, according to the broadband high-speed wavelength converter according to the eighteenth aspect of the present invention, laser beams of different wavelengths emitted from the nonlinear optical crystal can be coaxially overlapped.

Here, the first dispersion element and the second dispersion element can be prisms.

Further, the first dispersion element and the second dispersion element can be diffraction gratings.

[0052]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a wide-band high-speed wavelength conversion method and apparatus according to the present invention;

FIG. 4 shows a conceptual configuration diagram of an example of an embodiment of a broadband high-speed wavelength converter according to the present invention. This broadband high-speed wavelength converter includes a titanium sapphire laser (wavelength tunable laser). Ti: sapph
ir laser) to the nonlinear optical crystal 1
0 as the excitation laser beam to the nonlinear optical crystal 10
Is a broadband high-speed wavelength converter that performs harmonic conversion of the excitation laser light by emitting the second harmonic of the excitation laser light as converted laser light.

That is, the broadband high-speed wavelength converter shown in FIG. 4 comprises a nonlinear optical crystal 10, a first prism 12 as a dispersive element, and a first cylindrical concave mirror 14 as a condensing element.
And a second cylindrical concave mirror 16 as a light condensing element and a second prism 18 as a dispersing element.

The first prism 12 and the second prism 1
8 has the same configuration, and the first cylindrical concave mirror 14 and the second cylindrical concave mirror 16 have the same configuration.

In the broadband high-speed wavelength converter shown in FIG. 4, the optical path of the excitation laser light is refracted by the first prism 12 according to the wavelength, and the optical path of the beam is divided for each wavelength of the excitation laser light. Cylindrical concave mirror 14
Is adjusted so as to optimize the angle of incidence on the nonlinear optical crystal 10 at each wavelength, and the light is incident on the nonlinear optical crystal 10.

Note that the first cylindrical concave mirror 14 is
It also focuses the excitation laser beam.

The excitation laser beam incident on the nonlinear optical crystal 10 is wavelength-converted by the nonlinear optical crystal 10,
From the nonlinear optical crystal 10, the second harmonic of the excitation laser light is emitted as converted laser light.

The converted laser light emitted from the nonlinear optical crystal 10 has its optical path adjusted by the second cylindrical concave mirror 16 according to a principle reverse to the principle of the operation of the first prism 12 and the first cylindrical concave mirror 14, and The light enters the second prism 18, is refracted by the second prism 18, and is emitted through a predetermined optical path. That is, the light is collimated by the second cylindrical concave mirror 16 and the second prism 18, is superposed coaxially, and is emitted from the second prism 18.

Here, in the broadband high-speed wavelength converter shown in FIG. 4, the wavelength of the pump laser light is λ (where λ is λ ₁ ,
Any value such as λ _center , λ ₂ , ... can be taken. ), The incident angle θ ′ (λ) of the excitation laser light to the nonlinear optical crystal (θ ′ when λ = λ ₁ )
(Λ) is θ ′ (λ ₁ ), and θ ′ when λ = λ _center
(Λ) is θ ′ (λ _center ), and θ ′ when λ = λ ₂
(Λ) is θ ′ (λ ₂ ). ) Optimal incident angle to the nonlinear optical crystal 10 of the excitation laser light, i.e., the phase adjustment angle adapted to the phase matching condition θ (λ) (λ = λ 1 when theta
(Λ) is θ (λ ₁ ), and when λ = λ _center , θ
(Λ) is θ (λ _center ), and when λ = λ ₂ , θ
(Λ) is θ (λ ₂ ). (1) Incident angle β to first prism 12 (2) Apex angle A of first prism 12 (3) Material (dispersion characteristic) n (λ) of first prism 12 (4) 1 prism 12 and first cylindrical concave mirror 1
(5) Curvature R of the first cylindrical concave mirror 14 (6) Adjustment of six parameters of the angle of incidence α _center on the first cylindrical concave mirror 14 when the wavelength of the excitation laser beam is λ _center Will be done.

As described above, FIG.
Compared with the apparatus shown in FIG. 4, the broadband high-speed wavelength converter shown in FIG.

That is, the characteristics of the parameters (1) to (5) in the broadband high-speed wavelength converter shown in FIG. 4 substantially coincide with the characteristics of the parameters (1) to (5) in the device shown in FIG. cage, in a wideband high-speed wavelength converter shown in FIG. 4, as compared to the apparatus shown in FIG. 2, "(6) the angle of incidence alpha _center of the first cylindrical concave mirror 14 at a wavelength lambda _center of the excitation laser light" Has been added as a new parameter.

When the beam of the excitation laser beam separated by the first prism 12 is obliquely incident on the first cylindrical concave mirror 14, the first cylindrical concave mirror 14 functions as a kind of dispersion element. The dispersion characteristic of the first cylindrical concave mirror 14 can be continuously changed by changing the angle of incidence α _center on the cylindrical concave mirror 14.

For this reason, according to the broadband high-speed wavelength converter shown in FIG. 4, it is possible to adjust θ ′ (λ) to θ (λ) with higher accuracy than the device shown in FIG. Can be.

Now, the principle of the broadband high-speed wavelength converter shown in FIG. 4 will be described. The solid line θ (λ) in the graph shown in FIG. 5 indicates that the nonlinear optical crystal is obtained when the center wavelength of the pump laser light is 800 nm. 10 shows an optimum incident angle of the excitation laser light to the nonlinear optical crystal 10 calculated from the ten phase matching conditions.

At each wavelength λ of the incident laser light, if the excitation laser light can be incident on the nonlinear optical crystal 10 at an incident angle θ (λ), the second harmonic of the excitation laser light can be generated with high efficiency.

In the broadband high-speed wavelength converter shown in FIG. 4, the first prism 12 and the first cylindrical concave mirror 14 are used so that the wavelength of the excitation laser light can be adjusted without rotating the nonlinear optical crystal 10 manually or by a motor. , The incident angle of the excitation laser beam to the nonlinear optical crystal 10 can be automatically set to θ (λ). Actually, the above-mentioned six parameters are selected so that the incident angle θ ′ (λ) determined by the above-mentioned six parameters becomes the optimum incident angle θ (λ).

Here, regarding the effect of the first prism 12, when the beam of the excitation laser beam enters the first prism 12, the direction of the beam changes for each wavelength due to the dispersion effect of the first prism 12. The wavelength dependence is a curve as indicated by the broken line in the graph shown in FIG. It can be seen that the shape of this curve is similar to θ (λ), but its slope is smaller than θ (λ).

Therefore, when the first cylindrical concave mirror 14 is used, the inclination of the above-described curve can be increased, and the spread of the beam can be suppressed. To be precise, the inclination of the above-mentioned curve is determined by the distance d between the first prism 12 and the first cylindrical concave mirror 14 and the curvature R of the first cylindrical concave mirror 14. However, the slope of the curve is different from the slope of θ (λ) (see FIG. 6).

Next, the shape of the curve having an inclination different from the inclination of θ (λ) is adjusted by the incident angle α _center on the first cylindrical concave mirror 14 and the incident angle β on the first prism 12. At this time, if the angle of incidence α _center on the first cylindrical concave mirror 14 and the angle of incidence β on the first prism 12 are changed, the slope of the curve changes at the same time (see FIG. 7).
The vertex angle A of the first prism 12, the material (dispersion characteristic) n (λ) of the first prism 12, the distance d between the first prism 12 and the first cylindrical concave mirror 14, and the curvature R of the first cylindrical concave mirror 14 are shown below. Change and make repeated adjustments.

Further, the broadband high-speed wavelength converter shown in FIG. 4 can use not only a low-power parallel beam but also a high-power parallel beam as the excitation laser light.

That is, when a parallel beam having a low power is used as the excitation laser beam, the focal point may be located in the nonlinear optical crystal 10 as shown in FIG. In this way, the cross-sectional area of the beam in the nonlinear optical crystal 10 is reduced, the intensity of the excitation laser light in the nonlinear optical crystal 10 can be increased, and efficient wavelength conversion can be performed.

On the other hand, when a high-power parallel beam is used as the excitation laser beam, as shown in FIG. 9, a convex lens 20 having an appropriate focal length is provided in front of the first prism 12.
Is arranged so that the focal point is located between the first prism 12 and the first cylindrical concave mirror 14, so that the beam of the excitation laser light is parallel on the nonlinear optical crystal 10. By doing so, the cross-sectional area of the beam in the nonlinear optical crystal 10 increases, and the intensity of the excitation laser light can be reduced.
Damage to the nonlinear optical crystal 10 can be prevented.

By adjusting the focal length of the convex lens 20 and the focal position generated between the first prism 12 and the first cylindrical concave mirror 14, the beam diameter of the excitation laser beam and the beam in the nonlinear optical crystal 10 are adjusted. The ratio with the diameter can be adjusted. Note that in FIG.
Reference numeral 2 denotes a convex lens, which acts so as to convert the laser light emitted from the second prism 18 into a parallel beam.

FIG. 10 is an explanatory view of a conceptual configuration of a main part in the case where an ordinary non-cylindrical spherical concave mirror 24 is used instead of the first cylindrical concave mirror 14 in the broadband high-speed wavelength converter shown in FIG. In this case, it is preferable to dispose a cylindrical lens 26 between the first prism 12 and the concave mirror 24.

Here, the concave mirror 24 has different focal points in the vertical and horizontal directions when the excitation laser beam is obliquely incident (see FIG. 11). Then, the cylindrical lens 26 acts to adjust only the focal point in the vertical direction (see FIG. 12).

FIG. 13 is a conceptual block diagram of another embodiment of the broadband high-speed wavelength converter according to the present invention. 4 are denoted by the same reference numerals as those used in FIG. 4, and detailed description of the configuration and operation will be omitted.

The broadband high-speed wavelength converter shown in FIG. 13 comprises a second cylindrical concave mirror 16 and a second prism 18.
Only the point that a nonlinear optical crystal 28 and a third cylindrical concave mirror 30 are disposed between them is different from the broadband high-speed wavelength converter shown in FIG.

Here, the nonlinear optical crystal 28 has the same configuration as the nonlinear optical crystal 10, and the third cylindrical concave mirror 30 has the same configuration as the first cylindrical concave mirror 14 and the second cylindrical concave mirror 16.

Therefore, according to the broadband high-speed wavelength converter shown in FIG. 13, the second harmonic of the converted laser light emitted from the nonlinear optical crystal 10 is wavelength-converted to the third harmonic by the nonlinear optical crystal 28. The third harmonic of the converted laser light is emitted from the second prism 18 as converted laser light.

Next, FIG. 4 performed by the present applicant.
Experimental results using the broadband high-speed wavelength converter shown in FIG.

In this experiment, the nonlinear optical crystal 10
Is a BBO crystal, and the nonlinear optical crystal 10
The BBO crystal has a crystal angle of 2 with respect to the excitation laser beam.
It is cut to be 9.2 degrees.

The excitation laser beam has a wavelength of 7
Pulses whose wavelength can be selected in the range of 06 nm to 948 nm
The laser uses a titanium sapphire laser, and its maximum energy is 4 mJ / pulse.
The pulse width is 20 ns to 40 ns.

Further, the above six parameters are as follows: (1) the incident angle β to the first prism 12: 70 degrees; (2) the apex angle A of the first prism 12: 67 degrees; and (3) the first prism 12 Material (dispersion characteristics) n (λ):
S F57 (4) First prism 12 and first cylindrical concave mirror 1
(4) Curvature R of the first cylindrical concave mirror 14: 106.1 mm
6.5 mm (6) The incident angle α _center on the first cylindrical concave mirror 14 when the wavelength of the excitation laser beam is λ _center is set to 60 degrees.

The graphs shown in FIGS. 14 to 16 are graphs showing the results of experiments under the above-described experimental conditions.
The solid line θ (λ) in FIG. 14 indicates the optimum incident angle of the pump laser light to the nonlinear optical crystal 10 calculated from the phase matching condition of the nonlinear optical crystal 10.

That is, if the excitation laser beam can be incident on the nonlinear optical crystal 10 at the incident angle θ (λ) at each wavelength λ of the excitation laser beam, the second harmonic of the excitation laser beam can be generated with high efficiency. .

Then, the broken line θ ′ (λ) in FIG.
Shows the measurement results of the incident angle of the excitation laser beam on the nonlinear optical crystal 10 under the above-described experimental conditions.

The solid line in FIG. 15 indicates the difference “θ” between the incident angle θ ′ (λ) of the excitation laser beam to the nonlinear optical crystal 10 measured under the above experimental conditions and the optimum incident angle θ (λ). (Λ) −θ ′ (λ) ”. Although the solid line representing the incident angle θ (λ) and the broken line representing the incident angle θ ′ (λ) in FIG. 14 almost overlap,
When “θ (λ) −θ ′ (λ)” is calculated and enlarged, FIG.
As shown in FIG.

Further, the broken line in FIG. 15 indicates the allowable range of the incident angle of the excitation laser light on the nonlinear optical crystal 10 for efficient wavelength conversion.

Accordingly, the incident angle θ ′ of the excitation laser beam to the nonlinear optical crystal 10 measured under the above-described experimental conditions.
([Lambda]) and the optimal angle of incidence [theta] ([lambda]), "[theta] ([lambda])-
If θ ′ (λ) ”is within the allowable angle described above, the second harmonic can be generated with high efficiency.

FIG. 16A shows the nonlinear optical crystal 1.
FIG. 16 (b) shows the relationship between the wavelength of the excitation laser light incident on the non-linear optical crystal 1 and the output of the excitation laser light.
The relationship between the wavelength of the second harmonic of the converted laser light emitted from 0 and the output of the second harmonic is shown. This FIG.
As shown in FIGS. 4A and 4B, according to the wideband high-speed wavelength converter shown in FIG.
The light in the wavelength range of m can be converted into a converted laser light including a second harmonic having a wavelength of 350 nm to 450 nm.

FIG. 17 shows that the nonlinear optical crystal 10 was changed when only the incident angle α _center to the first cylindrical concave mirror 14 was changed and the other experimental conditions were the same as those shown in FIG. 6 is a graph showing a change in the incident angle θ ′ (λ) of the excitation laser light of FIG. As is apparent from FIG. 17, when the incident angle α _center to the first cylindrical concave mirror 14 is changed, the wavelength dependence of the incident angle θ ′ (λ) of the excitation laser light to the nonlinear optical crystal 10 changes. I understand.

Here, the incident angle θ ′ (λ) of the excitation laser beam to the nonlinear optical crystal 10 and the above-mentioned six parameters (1) the incident angle β to the first prism 12 (2) the first prism 12 (3) Material of first prism 12 (dispersion characteristic) n (λ) (4) First prism 12 and first cylindrical concave mirror 1
(5) The curvature R of the first cylindrical concave mirror 14 (6) The incident angle α _center on the first cylindrical concave mirror 14 when the wavelength of the excitation laser beam is λ _center is defined as described above. (Refer to FIG. 18 which is an enlarged view of a main part of FIG. 4), but have a relationship as shown in a relational expression in FIG.

As is clear from the relational expression in FIG. 19, the incident angle θ ′ (λ) of the excitation laser beam to the nonlinear optical crystal 10 is the above-mentioned six parameters (1) the incident angle to the first prism 12. (2) Apex angle A of first prism 12 (3) Material (dispersion characteristic) n (λ) of first prism 12 (4) First prism 12 and first cylindrical concave mirror 1
(5) the curvature R of the first cylindrical concave mirror 14; (6) a function of the incident angle α _center on the first cylindrical concave mirror 14 when the wavelength of the excitation laser beam is λ _center ; The incident angle θ ′ (λ) of the excitation laser light to the nonlinear optical crystal 10 is determined by these six parameters.

In the relational expression in FIG. 19, b
Is a formula representing the deflection angle of the first prism 12, and is a function of the wavelength λ of the excitation laser light. When the wavelength λ of the excitation laser light changes, b also changes.

Further, x and y represent the positions on the first cylindrical concave mirror 14 where the excitation laser beam hits, and are functions of a, b and c, where a and c are the first cylindrical concave mirrors. It changes depending on the angle of incidence α _center on the concave mirror 14 and finally changes γ (λ).

Here, the prior art shown in FIG. 2 will be described with reference to the configuration diagram of the prior art corresponding to FIG. 2 shown in FIG. 20A and the conceptual diagram of the prior art shown in FIG. In the prior art, two pairs of prisms of the same material and the same apex angle generate a laser beam having a different optical path for each wavelength. The lens determines the angle of incidence on the nonlinear optical crystal by its light-collecting characteristics while maintaining the wavelength dependence created by the two pairs of prisms.

In such prior art, the lens is
As shown in FIG. 21, a simple function θ ′ (λ) symmetric about the center of the lens determined by the distance x ′ = x (λ) −x (λ _center ) from the center of the lens to the incident position of the beam.
= G (x ′ (λ)) [Accurately θ ′ (λ) = tan
⁻¹ (x ′ (λ) / f): f is the focal length of the lens], and thus the dispersion effect that determines the wavelength dependence of the angle of incidence on the nonlinear optical crystal in this prior art is due to the dispersion effect of the prism. Control is possible only by the dispersion characteristics. FIG.
2 (a) shows a main part configuration diagram of the broadband high-speed wavelength converter corresponding to FIG. 4, and FIG. 22 (b) shows a conceptual diagram of the broadband high-speed wavelength converter corresponding to FIG. However, in this broadband high-speed wavelength converter,
The first prism 12 separates the laser light beam for each wavelength and creates a distribution ε (λ) of wavelength components in the ε direction according to the dispersion characteristics of the material. Here, the first cylindrical concave mirror 14 functions as a light-collecting element similarly to the lens in the related art, and gives a function of θ ′ (λ) = h (ε (λ)). Cylindrical concave mirror 14
It can be changed by the inclination of. From this,
It is possible to further change the prism dispersion effect with a concave mirror.

Therefore, in the broadband high-speed wavelength converter according to the present invention, the wavelength dependence of the angle of incidence on the nonlinear optical crystal 10 depends on the dispersion characteristics of the first prism 12 and the dispersion effect of the first cylindrical concave mirror 14. Will be determined by As a result, the angle of incidence can be set with higher accuracy than in the prior art.

The same effect can be obtained by tilting the condenser lens instead of the concave mirror or displacing the center of the lens from the optical axis.

That is, in the conventional device, the lens is arranged so as to be perpendicular to the incident light.
As shown in (b), by disposing a condenser lens at the position of the cylindrical concave mirror of the broadband high-speed wavelength converter and adjusting the angle of the condenser lens, a dispersion effect can be obtained also in the lens.

Accordingly, in a device in which the cylindrical concave mirror of the broadband high-speed wavelength converter is replaced with a lens,
The wavelength dependence of the angle of incidence on the nonlinear optical crystal 10 is determined by two factors: the dispersion characteristics of the first prism 12 and the dispersion effect of the lens. As a result, the angle of incidence can be set with higher accuracy than in the prior art.

That is, as the light condensing element, a lens or the like can be used in addition to a cylindrical concave mirror or a normal non-cylindrical spherical concave mirror, and a parabolic mirror may be used.

As the dispersing element, a diffraction grating or the like can be used in addition to the prism.

FIG. 24 is a conceptual diagram showing an example of an embodiment of a broadband high-speed wavelength converter according to the present invention using a parabolic mirror as a light-collecting element. The conversion device is a tunable laser titanium
Sapphire laser (Ti: sapphire la)
Ser) is used as the excitation laser light for the nonlinear optical crystal 200, and the second harmonic of the excitation laser light is emitted from the nonlinear optical crystal 200 as the converted laser light, thereby performing the harmonic conversion of the excitation laser light. It is a broadband high-speed wavelength converter.

That is, in the broadband high-speed wavelength converter shown in FIG. 24, the incident-side first prism 202, which is the first dispersion element, into which the pumping laser beam is incident, and the pumping laser beam emitted from the incident-side first prism 202 An incident-side second prism 204 as a second dispersive element to be incident, a first parabolic mirror 206 as a condensing element for condensing and reflecting the excitation laser light emitted from the incident-side second prism 204, First parabolic mirror 2
And a second condensing element that condenses and reflects the converted laser light emitted from the nonlinear optical crystal 200.
A parabolic mirror 208, an output-side first prism 210 serving as a third dispersion element on which the converted laser light reflected by the second parabolic mirror 208 is incident, and a conversion output from the output-side first prism 210. It has an emission-side second prism 212 as a fourth dispersion element on which the laser light is incident.

The first prism 202 on the incident side and the second prism 204 on the incident side have the same configuration, and the first prism 210 on the exit side and the second prism 212 on the exit side have the same configuration. The first parabolic mirror 206 and the second parabolic mirror 208 have the same configuration.

In the broadband high-speed wavelength converter shown in FIG. 24, the excitation laser light is
The light path is refracted by 2 according to the wavelength, the light path of the beam is divided for each wavelength of the excitation laser light, and the light enters the second prism 204 on the incident side.

In the incident-side second prism 204, the optical path of the incident excitation laser light is refracted according to the wavelength and emitted as a parallel beam to the first parabolic mirror 206. The angle of incidence on the nonlinear optical crystal 200 is adjusted so as to be optimized at each wavelength, and the light is incident on the nonlinear optical crystal 200.

The first parabolic mirror 206 also focuses the excitation laser beam. Nonlinear optical crystal 20
The excitation laser beam incident on the non-linear optical crystal 20
The wavelength is converted by 0, and the second harmonic of the excitation laser light is emitted from the nonlinear optical crystal 200 as converted laser light.

The converted laser light emitted from the nonlinear optical crystal 200 is applied to the second parabolic mirror 206, the second prism 204 on the incident side, and the first prism 202 on the incident side in accordance with the second principle. The converted laser beam whose optical path is adjusted by the parabolic mirror 208 is incident on the first prism 210 on the emission side, is refracted by the first prism 210 on the emission side, is emitted through a predetermined optical path, and is emitted from the first prism 210 on the emission side. The light is further refracted by the emission-side second prism 212 and emitted through a predetermined optical path. That is, the converted laser light emitted from the nonlinear optical crystal 200 is collimated by the second parabolic mirror 208, the emission-side first prism 210, and the emission-side second prism 212, and is superposed coaxially on the emission-side second prism. It is emitted from 212.

Here, for example, in the embodiment shown in FIG. 4, when a spherical concave mirror is used in place of the first cylindrical concave mirror 14, the angle of incidence on the spherical concave mirror changes for each wavelength of the excitation laser light. The position of the focal point slightly changed for each wavelength (see FIG. 25A).
As a result, depending on the wavelength of the excitation laser light, there is a possibility that the excitation laser light cannot always be focused on the optimal position on the nonlinear optical crystal 10, and high wavelength conversion efficiency is obtained at all wavelengths of the excitation laser light. Could not be done.

However, in the embodiment shown in FIG. 24, the first parabolic mirror 206 used as a light-collecting element always collects light at one point when a parallel beam enters (FIG. 25).
(B)). In other words, the excitation laser light whose optical path has been separated by the incident-side first prism 202 and the incident-side second prism 204 in accordance with the wavelength change and which has been converted into a parallel beam,
The first parabolic mirror 206 always collects light at the same point.

Therefore, according to the embodiment shown in FIG. 24, regardless of the wavelength of the excitation laser light, the excitation laser light is always focused on the optimum position on the nonlinear optical crystal 200. Therefore, high wavelength conversion efficiency can be obtained regardless of the wavelength of the excitation laser light.

Also, the excitation laser light is applied to the nonlinear optical crystal 2.
When the light is focused on the same point on
The converted laser light emitted from 00 is also emitted from the same point, and the converted laser light emitted from the nonlinear optical crystal 200 can be always parallelized by the second parabolic mirror 208 regardless of the wavelength. . The parallel beams can be accurately and coaxially superimposed by the first and second exit-side prisms 210 and 212.

FIG. 26 shows the difference between the incident angle θ ′ (λ) of the excitation laser beam and the optimum incident angle θ (λ) under the following experimental conditions according to the embodiment shown in FIG.
A graph showing the relationship between (λ) −θ (λ) ”and the allowable range of the incident angle of the excitation laser light to the nonlinear optical crystal 200 for efficient wavelength conversion is shown.

In the graph shown in FIG. 26, the solid line is “θ ′ (λ) −θ (λ)” (in FIG. 26, “θ _pm ”
−θ _in ”. ), And a range surrounded by a broken line indicates an allowable range (allowable angle). As is clear from the graph shown in FIG.
It can be seen that wavelength conversion can be performed with high efficiency over a wide range of 8 μm.

Note that the above wavelength 0.64 μm to 0.9
The range of 8 μm is wider than the wavelength range shown in FIG.

FIG. 27 is a graph showing the variation in the emission position of the converted laser light finally emitted from the emission-side second prism 212 under the following experimental conditions according to the embodiment shown in FIG. Have been. As is clear from the graph shown in FIG.
5 μm to 0.50 μm (the wavelength of the excitation laser light is 0.7
(μm to 1.0 μm), the variation is as small as “± 0.06 mm”.

Here, the experimental conditions in the graphs shown in FIG. 26 and FIG. 27 are as follows: (1) Incident side first prism 202, incident side second prism 204 made of SF57, apex angle A1 = 60 degrees (2) Incident side first prism Distance between one prism 202 and second prism 204 on the incident side Distance d1 = 193 mm (3) First parabolic mirror 206, second parabolic mirror 208 Focal length at center wavelength = 60 mm Laser at center wavelength Light incident angle = 23 degrees (4) Outgoing side first prism 210, incident side second prism 212 Made of synthetic quartz, apex angle A2 = 74 degrees (5) Outgoing side first prism 210 and incident side second prism 212 Distance d2 = 255.7 mm (6) Nonlinear optical crystal 200 BBO crystal, length = 5 mm.

[0121]

Since the present invention is constructed as described above, it is not necessary to rotate the nonlinear optical crystal in order to position it at the phase matching angle, so that wavelength conversion can be performed at high speed. It has the effect.

Further, according to the present invention, since it is not necessary to rotate the nonlinear optical crystal in order to position the nonlinear optical crystal at the phase matching angle,
Even when a beam having a wide spectrum width is used as the incident laser light, there is no wavelength component deviating from the phase matching condition, and an excellent effect that a high conversion efficiency can be obtained.

Further, the present invention has an excellent effect that a beam including a plurality of wavelengths can be simultaneously incident on a nonlinear optical crystal as incident laser light, and that multiple wavelengths can be wavelength-converted at the same time. Play.

Further, the present invention has an excellent effect that the incident angle of the incident laser light on the nonlinear optical crystal can be set to the phase adjustment angle with high accuracy.

Further, the present invention has an excellent effect that a parallel beam having a high power can be used as incident laser light.

Further, the present invention has an excellent effect that converted laser beams of different wavelengths emitted from the nonlinear optical crystal can be coaxially overlapped.

[Brief description of the drawings]

FIG. 1 shows a method of satisfying a conventional phase matching condition, in which a nonlinear optical crystal is positioned at a phase matching angle satisfying a phase matching condition with respect to incident laser light by rotating the nonlinear optical crystal manually or by a motor. It is a conceptual structure explanatory view.

FIG. 2 is a conceptual configuration explanatory view showing a conventional apparatus for adjusting an incident angle of incident laser light on a nonlinear optical crystal without rotating the nonlinear optical crystal manually or by a motor.

FIG. 3 is a conceptual configuration diagram showing a state in which, when a parallel beam is used as incident laser light in the apparatus shown in FIG. 2, the incident laser light is condensed on an amorphous optical crystal.

FIG. 4 is a conceptual configuration explanatory diagram of an example of an embodiment of a broadband high-speed wavelength converter according to the present invention.

FIG. 5 is a graph for explaining the effect of the first prism when explaining the principle of the broadband high-speed wavelength converter according to the present invention.

FIG. 6 shows the distance d between the first prism and the first cylindrical concave mirror, the curvature R of the first cylindrical concave mirror, and the curvature R of the second cylindrical concave mirror 16 when explaining the principle of the broadband high-speed wavelength converter according to the present invention. 3 is a graph for explaining the effect of FIG.

FIG. 7 is a graph for explaining the effects of the angle of incidence α on the first cylindrical concave mirror and the angle of incidence β on the first prism when explaining the principle of the broadband high-speed wavelength converter according to the present invention.

FIG. 8 is a conceptual configuration explanatory view showing a case where a parallel beam with low power is used as incident laser light in the broadband high-speed wavelength converter according to the present invention.

FIG. 9 is a conceptual configuration explanatory view showing a case where a high-power parallel beam is used as incident laser light in the broadband high-speed wavelength converter according to the present invention.

FIG. 10 is an explanatory diagram of a conceptual configuration of a main part in a case where a normal non-cylindrical concave mirror is used in place of the first cylindrical concave mirror in the broadband high-speed wavelength converter shown in FIG. 4;

FIG. 11 is a conceptual configuration explanatory view showing a state where focal points are different between a vertical direction and a horizontal direction when an incident laser beam is obliquely incident on a concave mirror.

FIG. 12 is a conceptual configuration explanatory view showing an operation of adjusting a focal point in a vertical direction of a cylindrical lens.

FIG. 13 is a conceptual configuration explanatory view of another embodiment of the broadband high-speed wavelength converter according to the present invention.

FIG. 14 is a graph showing experimental results, in which the optimum incident angle θ (λ) of the excitation laser beam to the nonlinear optical crystal calculated from the phase matching condition of the nonlinear optical crystal and the nonlinear optical crystal measured by the experiment. The relationship with the incident angle θ ′ (λ) of the excitation laser light to the laser beam is shown.

FIG. 15 is a graph showing experimental results, wherein the difference between the incident angle θ ′ (λ) of the excitation laser light to the nonlinear optical crystal measured by the experiment and the optimal incident angle θ (λ) is “θ”.
([Lambda])-[theta] '([lambda]) "and the allowable range of the incident angle of the excitation laser light to the nonlinear optical crystal for efficient wavelength conversion.

FIGS. 16A and 16B are graphs showing experimental results, wherein FIG. 16A shows the relationship between the wavelength of the pump laser light incident on the nonlinear optical crystal and the output of the pump laser light, and FIG. 4 shows the relationship between the wavelength of the second harmonic of the converted laser light and the output of the second harmonic.

FIG. 17 shows the angle of incidence α on the first cylindrical concave mirror.
15 is a graph showing the change in the incident angle θ ′ (λ) of the excitation laser light to the nonlinear optical crystal when the experiment was performed under the same conditions as in the experiment shown in FIG. 14 _except for changing the _center .

FIG. 18 is an enlarged view of a main part of FIG. 4;

FIG. 19 shows an incident angle θ ′ (λ) of the excitation laser beam to the nonlinear optical crystal and six parameters (1) an incident angle β to the first prism 12 (2) a vertex angle A of the first prism 12 (3) Material of first prism 12 (dispersion characteristic) n (λ) (4) First prism 12 and first cylindrical concave mirror 1
(5) The curvature R of the first cylindrical concave mirror 14 (6) The relational expression with the incident angle α _center on the first cylindrical concave mirror 14 when the wavelength of the excitation laser light is λ _center is shown.

20 is an explanatory diagram for explaining the operation of the related art, and FIG. 20A is a configuration diagram of the related art corresponding to FIG.
(B) is a conceptual diagram of the prior art.

FIG. 21 is an explanatory diagram for explaining an operation of a lens in the related art.

22A and 22B are explanatory diagrams for explaining the operation of the present invention. FIG. 22A is a configuration diagram of a main part of a wideband high-speed wavelength converter corresponding to FIG. 4, and FIG. 22B is a broadband corresponding to FIG. It is a conceptual diagram of a high-speed wavelength converter.

FIG. 23 is an explanatory diagram for explaining a dispersion effect;
(A) is an explanatory view showing a dispersion effect by a cylindrical concave mirror, and (b) is an explanatory view showing a dispersion effect by a lens.

FIG. 24 is a conceptual configuration diagram of an example of an embodiment of a broadband high-speed wavelength converter according to the present invention using a parabolic mirror as a light-collecting element.

25A and 25B show focal positions of reflected light by a spherical concave mirror and a parabolic mirror, FIG. 25A shows a case of a spherical concave mirror, and FIG.
Indicates the case of a parabolic mirror.

FIG. 26 is a graph showing experimental results, wherein “θ ′ (λ) −θ (λ)”, which is the difference between the incident angle θ ′ (λ) of the excitation laser beam and the optimal incident angle θ (λ); The relationship with the allowable range of the incident angle of the pump laser light to the nonlinear optical crystal for efficient wavelength conversion is shown.

FIG. 27 is a graph showing experimental results, showing a change in the emission position of converted laser light finally emitted from the emission-side second prism.

[Explanation of symbols]

 10, 28, 200 Nonlinear optical crystal 12 First prism 14 First cylindrical concave mirror 16 Second cylindrical concave mirror 18 Second prism 20, 22 Convex lens 24 Concave mirror 26 Cylindrical lens 30 Third cylindrical concave mirror 202 Incident first prism 204 2 prism 206 first parabolic mirror 208 second parabolic mirror 210 first prism on output side 212 second prism on output side

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Hideo Tashiro 19-1399, Koshiji, Nagamachi, Aoba-ku, Sendai-shi, Miyagi Prefecture Photodynamics Research Center, RIKEN

Claims (18)

[Claims] In a broadband high-speed wavelength conversion method for performing laser light wavelength conversion by harmonic conversion by injecting laser light into a nonlinear optical crystal, the laser light is incident on a dispersive element, and The optical path is separated according to the wavelength change of the laser light and emitted from the dispersion element, and the laser light emitted from the dispersion element is made incident on the light-collecting element, and according to the light-collecting characteristics of the light-collecting element. The laser light emitted from the condensing element is reflected and emitted, and is incident on the nonlinear optical crystal. The laser light is incident on the nonlinear optical crystal according to the dispersion characteristics of the dispersive element and the condensing properties of the optical condensing element. A broadband high-speed wavelength conversion method comprising controlling an incident angle of a laser beam. 2. The wide-band high-speed wavelength conversion method according to claim 1, wherein the laser beam incident on the dispersion element includes a plurality of different wavelength components. 3. A wide-band high-speed wavelength conversion method for injecting a laser beam into a nonlinear optical crystal and performing wavelength conversion of the laser beam by harmonic conversion, wherein the wavelength-converted laser beam emitted from the nonlinear optical crystal is collected. The light enters the optical element, emits according to the light-collecting characteristics of the light-collecting element. A broadband high-speed wavelength conversion method, wherein laser light emitted from the dispersion element is coaxially overlapped according to the light-collection characteristic of the light-collection element and the dispersion characteristic of the dispersion element. 4. The wide-band high-speed wavelength conversion method according to claim 1, wherein the dispersive element is a prism. 5. The wide-band high-speed wavelength conversion method according to claim 1, wherein the dispersion element is a diffraction grating. 6. The wide-band high-speed wavelength conversion method according to claim 1, wherein the light-collecting element is a concave mirror. 7. The wide-band high-speed wavelength conversion method according to claim 1, wherein the light-collecting element is a lens. 8. A wide-band high-speed wavelength converter for injecting laser light into a nonlinear optical crystal and performing wavelength conversion of the laser light by harmonic conversion, wherein the laser light is incident, and the laser light is converted into a wavelength of the laser light. A dispersion element that separates an optical path in response to the change and emits the light, a laser light emitted from the dispersion element is incident, and a light-collecting element that reflects and emits the laser light according to light-collecting characteristics; A broadband high-speed wavelength conversion device, comprising: a nonlinear optical crystal that emits the emitted laser light at an incident angle controlled according to the dispersion characteristics of the dispersion element and the light-collection characteristics of the light-collection element. 9. The wideband high-speed wavelength converter according to claim 8, wherein the laser beam incident on the dispersion element includes a plurality of different wavelength components. 10. A wide-band high-speed wavelength converter for injecting a laser beam into a nonlinear optical crystal and performing wavelength conversion of the laser beam by harmonic conversion, wherein a wavelength-converted laser beam emitted from the nonlinear optical crystal is incident. A light-collecting element that emits light according to light-collecting characteristics; and a dispersion element that receives laser light emitted from the light-collecting element and emits light according to dispersion characteristics. A wide-band high-speed wavelength converter, wherein laser beams emitted from the dispersive element are coaxially overlapped according to characteristics and dispersion characteristics of the dispersive element. 11. The method according to claim 8, 9 or 10.
The wideband high-speed wavelength conversion device according to claim 1, wherein the dispersion element is a prism. 12. The method according to claim 8, 9 or 10.
The wide-band high-speed wavelength converter according to claim 1, wherein the dispersion element is a diffraction grating. 13. The method according to claim 8, 9 or 10.
The wideband high-speed wavelength converter according to claim 1, wherein the light-collecting element is a concave mirror. 14. The method according to claim 8, 9 or 10.
The wide-band high-speed wavelength conversion device according to claim 1, wherein the light-collecting element is a lens. 15. A broadband high-speed wavelength conversion method for performing wavelength conversion of laser light incident by harmonic conversion by injecting laser light into a nonlinear optical crystal, wherein the laser light is incident on a first dispersion element, The incident laser light is separated by refracting the optical path in accordance with the wavelength change and is emitted from the first dispersion element. The laser light emitted from the first dispersion element is transmitted to the second dispersion element. The incident laser beam is emitted from the second dispersive element as a parallel beam by refracting the incident laser beam in accordance with the wavelength change, and the parallel beam laser beam emitted from the second dispersive element Is incident on the parabolic mirror, and the incident parallel beam laser light is condensed and reflected at the same point by the parabolic mirror, and condensed and reflected at the same point from the parabolic mirror. Talay Laser light incident on the nonlinear optical crystal according to the dispersion characteristics of the first dispersion element and the second dispersion element and the condensing characteristics of the parabolic mirror; A wide-band high-speed wavelength conversion method characterized by controlling an incident angle of light. 16. A wide-band high-speed wavelength conversion method for performing wavelength conversion of a laser beam incident by harmonic conversion by injecting a laser beam into a nonlinear optical crystal, wherein the wavelength-converted laser beam emitted from the nonlinear optical crystal is used. Is incident on a parabolic mirror, is reflected as a parallel beam by the parabolic mirror, and the laser beam reflected as a parallel beam from the parabolic mirror is incident on a first dispersion element and is converted into a parallel beam. The incident laser light is emitted after refracting the optical path corresponding to the wavelength change, and the laser light emitted from the first dispersion element is incident on the second dispersion element, and the incident laser light is converted into a wavelength. The optical path is refracted in response to the change and emitted, and the second dispersion element is formed according to the light-collecting characteristics of the parabolic mirror and the dispersion characteristics of the first dispersion element and the second dispersion element. Exit from Broadband fast wavelength conversion method characterized by superimposing the laser light coaxially. 17. A broadband high-speed wavelength conversion device for performing wavelength conversion of a laser beam incident by harmonic conversion by injecting a laser beam into a nonlinear optical crystal. The first dispersion element that separates and emits the light by refracting the optical path in response to the wavelength change; and the laser light emitted from the first dispersion element is incident, and the incident laser light is changed in wavelength. A second dispersive element that emits a parallel beam by refracting an optical path corresponding to the above, and a parallel beam laser beam emitted from the second dispersive element is incident, and the incident parallel beam laser beam A parabolic mirror that converges and reflects the same point on the same point, and a laser beam condensed and reflected on the same point from the parabolic mirror, the first dispersive element and the second dispersive element Dispersion characteristics and wideband fast wavelength conversion apparatus characterized by having a nonlinear optical crystal which enters the angle of incidence is controlled in accordance with the focusing characteristic of the parabolic mirror. 18. A wide-band high-speed wavelength converter for injecting laser light into a nonlinear optical crystal and performing wavelength conversion of the laser light incident by harmonic conversion, the wavelength-converted laser light emitted from the nonlinear optical crystal. Incident, and a parabolic mirror that reflects as a parallel beam, and the laser light reflected as a parallel beam from the parabolic mirror is incident, and the laser light incident as a parallel beam corresponds to the wavelength change. A first dispersion element that refracts an optical path and emits the laser light; and a laser beam emitted from the first dispersion element enters and emits the incident laser light by refracting the optical path corresponding to a wavelength change. A second dispersive element, and emits light from the second dispersive element according to the light-collecting characteristics of the parabolic mirror and the dispersive characteristics of the first dispersive element and the second dispersive element. laser -A broadband high-speed wavelength converter characterized in that light is coaxially superimposed.