JPH04130686A - Laser light wavelength converter - Google Patents

Abstract

PURPOSE:To improve a wavelength conversion efficiency by aligning condensing angles to a predetermined angle capable of accurately satisfying phase aligning condition of all lights to be converted in a laser luminous flux. CONSTITUTION:A parallel laser luminous flux 21 is applied to a convex conical lens 40 to convert it to a conical luminous flux 22 to be incident to a nonlinear optical crystal 50. In this case, a conical axis FL is brought into coincidence with the direction of a crystal optical axis (z), the light 20 to be converted is condensed in the vicinity of a focal line FL to be enhanced to form a high intensity region of a polarized wave. The vertex angle of the lens 40 is so set that the vertex of the flux 21 becomes an angle for satisfying phase aligning conditions. A second harmonic wave conversion light 30 generated by wavelength conversion in the nonlinear optical crystal 40 is converted to a parallel output luminous flux 31 by a conical lens 60 to be externally output. Thus, it is condensed to the condensing angle coincident with the phase aligning angle to satisfy the phase aligning condition and to improve its wavelength conversion efficiency.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a laser that projects a laser beam onto a nonlinear optical crystal such as β-barium borate (BBO) or lithium niobate and converts it into light of a different wavelength. The present invention relates to an optical wavelength conversion device.

[Conventional technology]

As is well known, lasers generate coherent light that is powerful and has sharp directivity, so their applications are not limited to the fields of material processing and measurement, but recently in medicine.

Although they are becoming widespread in the chemical industry, they only oscillate at specific wavelengths, with some exceptions, and this is one of the biggest obstacles to their application.

Laser light wavelength conversion technology using nonlinear optical crystals, which is the subject of the present invention, is attracting attention as a promising means of solving this problem.The principle and main conventional techniques will be briefly explained below. .

Generally, when two laser beams with different frequencies enter a nonlinear optical crystal, a polarized wave with an intensity proportional to the optical electric field of each laser beam and a polarized wave with an intensity proportional to the product of both electric fields is generated inside the crystal. . The latter has a frequency that is the sum of the frequencies of the re-entering laser light, and from this, light with a frequency or wavelength different from that of the original laser light is obtained. This is the principle of wavelength conversion called sum frequency generation, but what is practically important is when two incident laser beams have the same frequency, that is, converting a single laser beam into light with twice the frequency or half the wavelength. In this case, the second high wave generation or 5HG (Second H
It is called "Armonic Generatlon".

On the other hand, it is also possible to do the opposite wavelength conversion, that is, apply a laser beam of a certain frequency to a nonlinear optical crystal and convert it into two beams whose sum of frequencies is equal to the frequency of the original laser beam.

In this case, a nonlinear optical crystal is usually incorporated into the resonator and resonance conditions are adjusted so that both or only one of the two converted lights can be oscillated and extracted. This is optical parametric oscillation or OPO (Optica
l Parasétric 0scillation)
It is called.

By the way, in both the SHG and OPO systems, in order to increase the wavelength conversion efficiency, it is necessary to advance the laser light, which is the light to be converted, and the converted light in a nonlinear optical crystal with the same phase, and this is called phase matching. Calling 0 e.g. SHG
Then, the fundamental wave, which is the light to be converted, and the second harmonic, which is the converted light, are made to travel in the same direction under phase matching conditions. For this purpose,
The velocity of both waves, that is, the refractive index of the nonlinear optical crystal for both waves, must be the same, but since the higher the frequency of light, the higher the refractive index, this phase matching condition is generally not satisfied. The optical anisotropy of is often used for phase matching.

Hereinafter, the essential cost of phase matching in the case of using a uniaxial negative crystal will be explained.

Light incident on this type of crystal travels as ordinary light and extraordinary light, and the refractive index for the former is constant regardless of the direction of incidence, but the refractive index for the latter changes depending on the direction.

A negative crystal is one in which the refractive index of extraordinary light is lower than the refractive index of ordinary light, and an example of its optical anisotropy is shown in Figure 9. In this figure, the refractive index is drawn from the origin to the line segment of each curve. The optical axis of the crystal is the direction in which the refractive index of ordinary light and extraordinary light are equal, expressed by the length of
For ordinary light, the refractive index nle of the fundamental wave and the refractive index nto of the second harmonic wave are constant in all directions, but for extraordinary light, the refractive index l1ls of the fundamental wave and the refractive index ntm of the second harmonic wave are on the optical axis 2. It changes into an elliptical shape depending on the angle θ from

Now, as shown in the figure, the refractive index of the fundamental wave of ordinary light is n.

Since and the refractive index nfs of the second harmonic of the extraordinary light are equal in the direction of angle θ1 from optical axis 2, the converted light is used as a fundamental wave and propagates inside this optical crystal in the direction of this angle θ□. If the beam is incident in such a way, phase matching will be satisfied.

In this way, phase matching in which the fundamental wave is the ordinary light and the second harmonic is the extraordinary light is called Type I.

In addition, it is also possible to perform wavelength conversion in which the fundamental wave is ordinary light and extraordinary light and the second harmonic is extraordinary light. In this case, the phase matching condition is n tm = (n 1 ° + n l @ ) / ”
This is satisfied in the direction of the angle θ1 in the figure. This is called a type n phase matching condition.

Both types I and ■ above are called angular phase matching methods because they achieve phase matching by adjusting the incident angle of the converted light with respect to the optical axis of the nonlinear optical crystal.This method is popular because the adjustment is easy in principle. Laser light wavelength conversion devices have been widely used.

However, even when such a phase matching method is used, it is necessary to increase the incident intensity of the light to be converted in order to increase the wavelength conversion efficiency to a level that can be used in practice. However, it has been customary to enter the nonlinear optical crystal from an angular direction that satisfies the phase matching condition, and to form a high-intensity region of the resulting polarized wave within as narrow a range as possible near the focal point of the lens inside the crystal.

[Problem to be solved by the invention] In principle, high wavelength conversion efficiency should be obtained if a high-intensity region of polarized waves by the converted light is formed in a nonlinear optical crystal while satisfying the phase matching condition as described above. However, in reality, things often do not always go as planned.

One of the reasons for this is that when the converted light is focused near the focal point of the lens to form a high-intensity region of polarized waves, the angular phase matching condition is no longer accurately satisfied. In other words, since the light flux of the converted light converges at a focal point, that is, one point, the light flux contains various angular components of the converted light, and even if the phase matching condition is satisfied for a specific angular component among them, This is because it does not hold true for other angle components. For example, the angle θ5 in FIG. , the refractive index n1° and nte become even greater, but even a slight deviation in the angle will cause a large change in both, so the phase matching condition no longer holds true, and the allowable angle for this deviation is usually very small, about 15 rad. It is nearly impossible to focus the converted light at a narrow angle.

Another cause is so-called walk-off, where the converted light and the converted light separate. In a uniaxial optical crystal, the propagation directions of ordinary and extraordinary light are different except for the optical axis and the direction perpendicular to it, so a walk-off always occurs between the converted light and the converted light, and the polarization waves of both interact. The range in which the wavelength conversion can be performed is restricted, and the wavelength conversion efficiency tends to decrease.Of course, the more strongly the light to be converted is focused by a lens or the like, the more this adverse effect increases.

An object of the present invention is to overcome these contradictions and difficulties and provide a laser light wavelength conversion device with high conversion efficiency.

[l[Means for solving the problem]

According to the first invention of the present case, this purpose is to convert a laser beam of light to be converted into a conical beam by an optical means and converge it inside a uniaxial nonlinear optical crystal; by aligning the direction of the light beam with the optical axis direction of the nonlinear optical crystal, and setting the apex angle of the conical light beam condensed within the nonlinear optical crystal so as to satisfy the phase matching condition between the converted light and the converted light. achieved.

Note that it is advantageous for the optical means in the above structure to consist of a convex conical lens or a part thereof; if the angle of incidence that satisfies the phase matching condition of the converted light with respect to the nonlinear optical crystal is relatively large, it is preferable to use a concave conical lens. Advantageously, it consists of a conical mirror section. This can also be a concave cylindrical mirror section.

Furthermore, in order to further improve the wavelength conversion efficiency, a resonant mirror with high reflectivity for the converted light is provided on the opposite side of the optical means of the nonlinear optical crystal, and this is used as one of the resonant mirror pairs to create a laser for the converted light. It is advantageous to insert optical means and a nonlinear optical crystal into the resonant system of the oscillator.

Further, according to the second invention of the present case, for a uniaxial nonlinear optical crystal having a conical surface having an apex angle of 90 degrees and whose central axis is flush with the optical axis of the crystal, the converted light parallel to the optical axis of the crystal is The laser beam is incident on the inner surface of the conical surface of the nonlinear optical crystal so as to be totally reflected and focused on the central axis of the conical surface, and the converted light is converted into converted light under the condition of 90 degree phase matching between the two lights. The above objectives are achieved by wavelength conversion.

In this second invention, in order to further improve the wavelength conversion efficiency, it is particularly advantageous to insert the nonlinear optical crystal with its conical surface as one of a pair of resonant mirrors into a laser resonant system for oscillating the light to be converted.

Further, in terms of implementation, it is convenient to use a wavelength selective mirror to separate the converted light from the converted light and to take it out in a different direction.

Note that both the first and second inventions are suitable for converting the wavelength of SHG, that is, the light to be converted, into converted light of the second harmonic of the fundamental wave. Further, the first invention performs wavelength conversion by type I
It is suitable for both of the phase matching conditions (1) and (2).

[Function] In the present invention as well, the laser beam of the converted light is condensed into a nonlinear optical crystal in order to increase the wavelength conversion efficiency, as in the conventional case. By aligning all of the converted lights to a certain angle that can accurately satisfy the phase matching condition, the wavelength conversion efficiency is improved and the desired problem is solved.

That is, in the first invention, the light beam to be converted is converted into a conical light beam by an optical means, and in the second invention, a conical surface having a central axis in the optical axis direction and having an apex angle of 90 degrees is provided in the nonlinear optical crystal. In either case, the converted light is focused on the central axis of the cone by making the beam of the converted light parallel to the optical axis of the crystal incident so as to be totally reflected on the inner surface of the conical surface. In other words, whereas in the past, the converted light was focused near the focal point of a lens, etc., in the present invention, the converted light is focused near the focal line on the cone axis. The condensing angles of all the converted lights can be made constant and the phase matching condition can be accurately satisfied.

Also, regarding walk-off, even after the converted light generated in a certain part of the focal line leaves the converted light, it interacts with the converted light that is being focused in another part of the focal line. Therefore, in the present invention, the range in which the polarized waves of the converted light and the converted light can interact with each other is much wider than before, and the adverse effects of walk-off can be reduced more than before, and the wavelength conversion efficiency can be further improved. can.

〔Example〕

An embodiment of the laser light wavelength conversion device of the present invention will be described with reference to the drawings. In the following embodiments, wavelength conversion is performed using SHG for convenience of explanation, but the present invention can of course also be applied to OPO.

FIG. 1 shows a first embodiment of the first invention. In this example, the converted light 20 with a wavelength of 1.06p generated by a YAG laser (not shown) is applied to a uniaxial nonlinear optical crystal 50 such as BBO, and SHG using this as the fundamental wave
31! It is assumed that a second harmonic with a wavelength of m is generated and extracted as converted light 30.

In the first embodiment, a convex conical lens 40 is used as the optical means,
As shown in the figure, a desirably parallel laser beam 21 of the converted light 20 is applied to this, and the conical beam 22 is converted into a conical beam 22, which is then input into the nonlinear optical crystal 50. In addition, at this time, by aligning the conical axis PL of the conical light beam 22 with the direction of the crystal optical axis 2 of the uniaxial nonlinear optical crystal 50, the converted light 20
is focused in the vicinity of the focal line PL that coincides with the two directions of the optical axis to form a high-intensity region of the polarized wave, which is about 103 times higher than the original intensity.

In addition, since this converted light 20 is condensed by the conical lens 40 in the form of a conical light beam 21 whose traveling directions are aligned,
The light is always incident on all points on the focal line FL at a constant condensing angle. Furthermore, in this embodiment, the apex angle in the nonlinear optical crystal 40 of the conical light beam 21 that determines the condensing angle is, for example, the angle θ in FIG.
The apex angle of the conical lens 40 is set so that it becomes □. Note that the condensing angle θ1 that satisfies this phase matching condition is 22.8” when the nonlinear optical crystal 40 is BBO.

The converted light 30, which is the second harmonic generated by the wavelength conversion within the nonlinear optical crystal 40, is emitted in the form of a conical light beam having the same divergence angle as the condensing angle θ, 1 above. A conical lens 60, which is the same as the conical lens 40, is used in the opposite direction to form a parallel output beam 31, which is then taken out to the outside. Note that, in addition to the converted light 30, this output light beam 31 includes the converted light 20 that did not contribute to wavelength conversion, but if necessary, this can be removed from the output light beam 31 by means such as a wavelength selective mirror. can.

In the second embodiment shown in FIG. 2, the wavelength conversion device shown in FIG. 1 is incorporated into a resonant system of a laser device for oscillating light 20 to be converted. The laser device 10 generates converted light 20 using a laser medium 11 such as YAG, which is energized by a light source 10a. A wavelength conversion device comprising the above-mentioned conical lens 40 and nonlinear optical crystal 50 and including a conical lens 70 is inserted.

On the left side of the wavelength selective mirror 13 in the drawing, there is a coating 13a on the right side that is highly reflective for wavelengths of 1.06- but non-reflective for wavelengths of 0.53-. Each is provided with a coating 13b that is non-reflective for blue wavelengths.

In this second embodiment, since the high-intensity converted light 20 in the laser resonant system passes through the wavelength conversion device, the intensity of the converted light 20 received by the nonlinear optical crystal 50 is at least 1 This is an order of magnitude higher, making it possible to further improve wavelength conversion efficiency. This second embodiment is particularly useful for improving wavelength conversion efficiency when the output level of laser device 10 is relatively low.

3rd U2! In the third embodiment of J, a conical lens portion 41 is used as the optical means. This conical lens 41 includes, for example, a first
Although the diameter is larger than that of the conical lens 40 shown in the figure, a sector-shaped portion having a diameter of about half or one third is used.

The principle of wavelength conversion in this third embodiment is the same as that in the first embodiment, and in order to convert the converted light 30 into a parallel output beam 31, a conical lens 61, which is the same as the conical lens 41, is arranged in the opposite direction on the output side. However, even if the nonlinear optical crystal 50 is separated from the conical lenses 41 and 61 as shown in the figure, the advantage is that the focal line PL that condenses the converted light 20 can be formed within the nonlinear optical crystal 50. have. This is because if the linear optical medium 50 has deliquescent properties, it needs to be housed in a cell or the like, which requires some space around it.

In the fourth embodiment of FIG. 4, for example, the second harmonic of the wavelength of 0,534 obtained in the first embodiment is assumed to be the converted light of 2°,
A converted light 3o of the fourth harmonic having a wavelength of 0.26- is generated. However, in this case, for example, the angle θ1 at which the Type I phase matching condition is applied is 47.5° when BBO is used for the nonlinear optical crystal.

Since the phase matching angle θ□ is thus large, a concave conical mirror portion 42 is used as the optical means in this fourth embodiment. Figure (a) shows the same front view as before, Figure (b)
The side views are shown respectively. In this embodiment, as shown in the figure, the nonlinear optical crystal 5o is formed into a cylindrical shape, and the conical light beam 22 of the light 2o to be converted by the conical mirror portion 42 is incident from the circumferential surface of the nonlinear optical crystal 5o in the same direction as the optical axis 2. The light is focused on the fish & 1lpt. As before, converting the converted light 30 into a parallel output light beam 31 using the conical mirror portion 62 having the same shape as that for condensing light.

This fourth embodiment is suitable not only when the phase matching angle θ1 of type I is large as shown above, but also when the phase matching angle θ1 of type II is large as shown in FIG. is larger than that of type (2), so it is also suitable for phase matching of type (2).

In the fifth embodiment shown in FIG. 5, a concave cylindrical mirror portion 43 is used as the optical means, and its axis is arranged parallel to the optical axis 2 of the nonlinear optical crystal 5°. is incident from an oblique direction as shown in the figure, and the conical light beam 22 is transformed into a focal line PL.
The light is focused on.

Further, as before, the converted light 30 is made into a parallel output light beam 31 by the same cylindrical mirror portion 63. This fifth fruit”
The male side has the advantage that the cylindrical mirror parts 43 and 63 can be manufactured most easily, but the converted light 2 reflected on the cylindrical mirror surface
Since optical aberrations are likely to occur in the convergence of the zero conical light beam 22, it is preferable not to make the curvature of the mirror too large.

Although the first invention described above uses angular phase matching,
A special case is the phase matching angle θ.

Alternatively, it is possible to set θ1 to 90 degrees;
This is called degree phase matching.

The refractive index characteristics of a uniaxial nonlinear optical crystal that can satisfy the 90 degree phase matching condition shown in FIG. 8 is shown for the case of type I. As mentioned above, the curves of the refractive index n+e and nte for the fundamental wave and the second harmonic extraordinary light are ellipsoids, so under this Type 1 90 degree phase matching condition, the refractive index for the fundamental wave ordinary light is as shown in the figure. n1° curve and the refractive index n8 for the second harmonic extraordinary light. The curve is θ□−90”
They will touch each other in the direction of .

Therefore, in the vicinity of this phase matching angle θ1=90°, even if the angle is slightly shifted, the refractive index of both layers is n. And n! Therefore, the 90-degree phase matching shown in Figure 8 has a wider tolerance for the incident angle of the converted light to the nonlinear optical crystal than the normal angle phase matching shown in Figure 9, on the order of < lOmrad. Can tolerate deviations. Also, at the 90 degree phase matching point, n.

and n8. Since the intersection angle of the refractive index curves becomes 0, no walk-off occurs.

Because of these advantages, 90 degree phase matching is advantageous in improving wavelength conversion efficiency. Lithium niobate (LiNb) doped with magnesium oxide is a suitable nonlinear optical crystal for this purpose.
Os), which satisfies the refractive index condition shown in FIG. 8 at a temperature around 100°C.

To perform wavelength conversion under this 90 degree phase matching condition, for example, the apex angle of the conical surface 42a of the conical mirror portion 42 in FIG. 4(a) is set to 90 degrees, and the conical light beam 22 may be applied from a direction perpendicular to the optical axis 2, but in the second invention, the nonlinear optical crystal itself has the function of satisfying this 90 degree phase matching condition.

FIG. 6 shows a first embodiment of the second invention. For the nonlinear optical crystal 51, for example, lithium niobate is used as a uniaxial optical crystal suitable for 90-degree phase matching, and by optically polishing one end surface, the central axis PL is aligned in the direction of the crystal optical axis 2 as shown in the figure. A conical surface 52 having a matching 90 degree apex angle is formed. Next, this nonlinear optical crystal 51 is housed in a container 80 provided with a suitable window 81, and maintained at a temperature near the aforementioned 100° C. by means such as a temperature controller 90.

A light beam 21 of the converted light 20 with a wavelength of 1,061 m generated by a YAG laser, for example, is incident on this nonlinear optical crystal 51 from a direction parallel to the optical axis Z, and the conical surface 52 is By completely reflecting the light twice on the inner surface, the light is focused on the wireless FL and then emitted in the opposite direction to the direction of incidence. Therefore, the converted light 20 is the focal line FL within the nonlinear optical crystal 51.
High intensity light is always focused in the vicinity from a direction perpendicular to the S
Converted light 30 with a wavelength of 0.53 μ is generated by the HG with high wavelength conversion efficiency without walk-off, and is emitted from the nonlinear optical crystal 51 after being totally reflected by the conical surface 51 .

In the second invention, the paths of the converted light 20 that enters the nonlinear optical crystal 51 and the converted light 30 that is reversely emitted are the same as the converted light 20 that does not contribute to wavelength conversion.
The wavelength-selective mirror 70 shown preferably separates the converted light 20 and the converted light 30, the wavelength-selective mirror 70 being placed at 45 degrees to the light beam 21 and having one surface on one of its surfaces.
A coating 71 that is highly reflective at a wavelength of 0.06* and non-reflective for a wavelength t of 0.53 μm is provided, and a coating 72 that is non-reflective for both wavelengths is provided on the opposite side.

As a result, the light beam 21 of the converted light 20 is reflected by the wavelength-selective mirror 70 while passing into and out of the nonlinear optical crystal 5, and the output light beam 32 of the converted light 30 is reflected by the wavelength-selective mirror 70.
It can be separated and taken out from this through 0. Note that the conical surface 52 of the nonlinear optical crystal 5] functions as a total reflection mirror for the light beam 21, so if it is necessary to prevent the converted light 20 from returning to the YAG laser device, it is necessary to Appropriate measures such as inserting an isolator in the direction portion can be taken.

In the second practical example of the second invention shown in FIG. 7, the first embodiment is incorporated into the resonant system of the laser device lIO for oscillating the converted light 20. This laser device 10 uses a light source 10a to generate YAG
The laser medium 11 is optically excited to generate converted light 20 having a wavelength of 1.06-. A full oscillation mirror 12 is normally used as one of the pair of resonant mirrors in the laser resonant system.
By utilizing the fully oscillating conical surface 52 of the nonlinear optical crystal 51 as described above for the other resonant mirror, the nonlinear optical crystal 51 is tied into the laser resonant system.

The aforementioned wave N ashes mirror 7o is disposed between the laser medium 11 and the nonlinear optical crystal 51, and one surface 71 of the wave N ashes mirror 7o
1 and causes the converted light 2o to reciprocate within the laser resonant system. Converted light 30 with a wavelength of 0.53ts is generated by sHG from the converted light 2o focused near the focal line PL in the nonlinear optical crystal 51, and after being totally reflected by the conical surface 52, the wavelength selective mirror 7o It is extracted to the outside as a parallel output light beam 32 through the light beam. As in the case of FIG. 2, the nonlinear optical crystal 51 is housed in a container 8o and placed at a constant temperature using a temperature side illumination device 90.

In the second embodiment with the above configuration, the nonlinear optical crystal 51 receives the converted light 20 in the laser resonant system, which has an intensity that is more than one order of magnitude higher than that in the first embodiment, and in addition, in the SHG, the converted light 30 is the second harmonic. is generated with an intensity proportional to the square of the converted light 20, which is the fundamental wave, so high wavelength conversion efficiency can be achieved.

〔Effect of the invention〕

As described above, in the first invention, the light to be converted is made into a conical light beam by an optical means and is focused on the focal line in the l-axis nonlinear optical crystal, and at this time, the direction of the cone axis of the conical light beam is By matching the direction of the optical axis and setting the apex angle within the nonlinear optical crystal to satisfy the phase matching condition,
Further, in the second invention, a uniaxial nonlinear optical crystal is provided with a conical surface having an apex angle of 90 degrees whose central axis coincides with the optical axis direction of the crystal, and the beam of the light to be converted parallel to the optical axis of the crystal is directed to the conical surface. The light is incident on the inner surface of the cone so as to be totally reflected, is focused on a focal line on the central axis of the conical surface, and is subjected to wavelength conversion under 90 degree phase matching conditions, thereby achieving the effects described below. can.

(a) Since the light to be converted is condensed in the form of a conical light beam along the focal line in the nonlinear optical crystal at a condensing angle that matches the phase matching angle, all the targets to be wavelength converted are The phase matching condition is now accurately satisfied for the converted light, and the wavelength conversion efficiency is significantly improved compared to the conventional method.

(b) Even after the converted light generated near the focal line separates from the converted light due to walk-off, it interacts with the converted light that is being focused toward the focal line, resulting in polarization of the converted light and converted light. The interaction range between waves is much wider than before, reducing the adverse effects of walk-off and further improving wavelength conversion efficiency.

(C) In the second invention, with a simple configuration in which a conical surface is provided in the nonlinear optical crystal, the 90 degree phase matching condition is accurately satisfied for all the converted light and there is no walk-off, so the wavelength conversion efficiency is significantly improved. .

(According to the embodiment in which the dll wavelength disguise device is incorporated into the laser resonant system of the laser device for generating the converted light, the intensity of the converted light given to the nonlinear optical crystal can be increased by one order of magnitude or more, and the wavelength conversion efficiency can be significantly improved.

[Brief explanation of the drawing]

All drawings relate to the invention. 1 to 5 relate to a laser beam wavelength conversion device according to the first invention, FIG. 1 is a block diagram of a first embodiment using a conical lens as an optical means, and FIG. 2 is a wavelength conversion device of the first embodiment. Fig. 3 is a block diagram of a third embodiment that uses a conical lens section as an optical means, and Fig. 4 shows a fourth embodiment that uses a conical mirror section as an optical means. This is a configuration diagram of the same figure (a).
is its front view, FIG. 6 and 7 relate to a laser beam wavelength conversion device according to the second invention, and FIG. 6 is a configuration diagram of the first embodiment thereof,
FIG. 7 is a configuration diagram of a second embodiment in which the wavelength conversion device of the first embodiment is incorporated into a laser device. FIG. 8 is an angle versus refractive index characteristic diagram of a nonlinear optical crystal showing a 90 degree phase matching condition in relation to the second invention, and FIG. 9 is a nonlinear optical crystal showing an angular phase matching condition in relation to the first invention. FIG. 2 is an angle vs. refractive index characteristic diagram. In these figures, lO: laser device, 20: converted light, 21: laser beam of converted light, 22: conical beam of converted light, 30: converted light, 40: conical lens as optical means, 41: Conical lens part as optical means, 42: Conical mirror part as optical means, 43: Cylindrical mirror part as optical means,
50: Nonlinear optical crystal of the first invention, 51: Nonlinear optical crystal of the second invention, 52: Conical surface of nonlinear optical crystal, PL:
Focal line on which the light to be converted is focused, θ□: Phase matching angle of type ■, θ1: Phase matching angle of type ■, 2: Crystal optical axis,
It is.゛, 14th figure figure figure figure figure figure figure figure figure figure figure

Claims (1)

[Scope of Claims] 1) Optical means for converting a laser beam of light to be converted into a conical beam and condensing it on a conical axis; and an optical means for receiving and converting the conical beam so that the conical axis coincides with the optical axis of the crystal. Equipped with a uniaxial nonlinear optical crystal that converts light into converted light of different wavelengths, and set so that the apex angle of the conical light beam within the nonlinear optical crystal satisfies the phase matching condition between the converted light and the converted light. A laser light wavelength conversion device characterized by: 2) A laser beam wavelength conversion device according to claim 1, wherein the optical means is a convex conical lens. 3) A laser beam wavelength conversion device according to claim 2, wherein the optical means is a convex conical lens portion. 4) A laser beam wavelength conversion device according to claim 1, wherein the optical means is a concave conical mirror portion. 5) A laser beam wavelength conversion device according to claim 1, wherein the optical means is a concave cylindrical mirror portion. 6) In the device according to claim 1, a resonant mirror having high reflectivity for the converted light is provided on the side opposite to the optical means of the nonlinear optical crystal, and this is used as one of a pair of resonant mirrors for oscillating the converted light. A laser beam wavelength conversion device characterized in that an optical means and a nonlinear optical crystal are inserted into a laser resonant system. 7) A uniaxial nonlinear optical crystal has a conical surface with an apex angle of 90 degrees and whose central axis coincides with the crystal optical axis.The laser beam parallel to the crystal optical axis of the converted light is totally reflected on the inner surface of the conical surface. The wavelength of laser light is such that the light is incident on the central axis of a conical surface, and the light to be converted is converted into converted light of a different wavelength under conditions of 90 degree phase matching between the two lights. conversion device. 8) A laser light wavelength conversion device according to claim 7, wherein a nonlinear optical crystal is inserted into a laser resonant system for oscillating light to be converted, in which a conical surface is one of a pair of resonant mirrors. 9) A laser beam wavelength conversion device according to claim 7, wherein the converted light is separated from the converted light by a wavelength selective mirror and extracted in a different direction. 10) The laser light wavelength conversion device according to claim 1 or 7, wherein the converted light is a second harmonic of the converted light as a fundamental wave.