JPH06350176A - Device for generating laser beam harmonics - Google Patents

Abstract

PURPOSE:To provide a laser beam harmonic generating device which efficiently generates harmonics without permitting beam reflected by a filter to directly enter a non-linear optical element. CONSTITUTION:A flat convex lens 2 and a flat convex lens type filter 4 are provided at a prescribed interval permitting the convex planes to face each other and a non-linear optical element 3 is provided at the focal point S of the flat convex lens 2. The non-linear optical element 3 efficiently converts the fundamental waves alpha of laser beams entered with high energy density into second harmonics beta. The fundamental waves alpha are reflected by the film 4b on the convex plane and are permitted to diverge. The second harmonics betaare permitted to permeate the film 4b to be applied on a flat lens 4a and are collimated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser light harmonic generator, and more particularly to a nonlinear optical element for converting a fundamental wave of laser light into a harmonic, and a fundamental wave of laser light transmitted through the nonlinear optical element. The present invention relates to a harmonic generation device for laser light, which includes a filter that reflects light and transmits harmonics.

[0002]

2. Description of the Related Art Conventionally, a harmonic generator for converting a fundamental wave of laser light into a second harmonic has been used in processing or marking with laser light. This is because a smaller light spot can be obtained and fine processing can be performed by using the second harmonic wave having a shorter wavelength than the fundamental wave.

FIG. 2 is a front view showing the structure of a conventional harmonic generator 31 and its usage. In the harmonic generator 31, the nonlinear optical element 32 for converting the fundamental wave α of the laser light into the second harmonic β with the efficiency E existing in the second harmonic β and the fundamental wave α of the laser light are reflected on the optical axis 31a. , And a filter 33 that transmits the second harmonic β.

However, the optical axis 31 of the harmonic generator 31 is
When the optical axis 34a of the laser light source 34 is aligned with a and the laser light is emitted from the laser light source 34, the fundamental wave α of the laser light
Is converted into a fundamental wave α and a second harmonic wave β by the non-linear optical element 32, and only the second harmonic wave β passes through the filter 33. The second harmonic β is used for processing and marking as described above.

[0005]

However, in such a harmonic generator 31, since the fundamental wave α of the laser light reflected by the filter 33 is incident on the nonlinear optical element 32 again, the laser of the reflected light is generated. There is a problem that the nonlinear optical element 32 is damaged or the output becomes unstable depending on energy.

Further, as shown in FIG. 3, when the energy density P of the laser light is reduced, the conversion efficiency E of the nonlinear optical element 32 decreases, so that the energy of the laser light with a relatively small energy density is used. Usage efficiency was poor.

Therefore, the main object of the present invention is to prevent the reflected light of the filter from directly entering the non-linear optical element, and to efficiently generate harmonics even from laser light having a small energy density. An object of the present invention is to provide a laser light harmonic generation device capable of performing the same.

[0008]

According to the present invention, a nonlinear optical element for converting a fundamental wave of a laser beam emitted from a laser light source into a harmonic wave and a fundamental wave of a laser beam transmitted through the nonlinear optical element are reflected. In a laser light harmonic generation device including a filter that transmits harmonics, the filter is a convex lens that diverges and reflects a fundamental wave and transmits harmonics, and the laser light source and the nonlinear optical A condenser lens is provided between the element and the element to condense the laser beam and make it enter the nonlinear optical element.

[0009]

In the laser light harmonic generating device according to the present invention, since the filter is a convex lens,
The reflected light of the filter becomes divergent light according to the shape of the convex surface.
Therefore, it is possible to prevent the reflected light of the filter from directly entering the nonlinear optical element, and it is possible to prevent the nonlinear optical element from being damaged or the output from becoming unstable due to the reflected light of the filter.

Further, since the condenser lens is provided between the laser light source and the non-linear optical element, the energy density of the laser beam can be increased by the condenser lens to irradiate the non-linear optical element. Therefore, it is possible to efficiently generate harmonics even from laser light having a low energy density.

[0011]

1 is a front view showing the structure of a harmonic generator 1 according to an embodiment of the present invention and its usage.
The harmonic generator 1 includes a plano-convex lens 2 for condensing a laser beam and a nonlinear optical element 3 (for example, KT) that converts a fundamental wave α of the laser beam into a second harmonic β with a certain efficiency E.
P; KTiOPO ₄ ) and the plano-convex lens type filter 4. The plano-convex lens type filter 4 is formed by coating the convex surface of the plano-convex lens 4a with a film 4b having an optical property of reflecting the fundamental wave α of the laser light and transmitting the second harmonic β.

Plano-convex lens 2 and plano-convex lens type filter 4
Are both provided with their optical axes aligned with the optical axis 1 of the harmonic generator 1 and at intervals equal to or greater than the focal length of the plano-convex lens 2.
The convex surface of the plano-convex lens 2 and the convex surface of the plano-convex lens type filter 4 face each other. That is, the plano-convex lens 2 and the plano-convex lens type filter 4 constitute a Kepler type beam expander. In addition, the nonlinear optical element 3 is the plano-convex lens 2
The focus S is included.

When the optical axis 1a of the harmonic generator 1 is aligned with the optical axis 5a of the laser light source 5 (for example, continuous wave type YAG laser) and the laser light source 5 emits the laser light, the laser light is flat. It is condensed by the convex lens 2 and is applied to the nonlinear optical element 3 with high energy density. Therefore, the fundamental wave α of the laser light is converted into the second harmonic laser with high efficiency E.

The fundamental wave α and the second harmonic wave β which have passed through the nonlinear optical element 3 are applied to the convex surface of the plano-convex lens type filter 4 while expanding. Of these, the fundamental wave α is reflected by the convex coating 4b and diverges. Therefore, the reflected fundamental wave α hardly enters the nonlinear optical element 3. On the other hand, the second harmonic β passes through the film 4b and enters the plano-convex lens mold 4a, and is collimated by the plano-convex lens 4a. The collimated second harmonic β is provided for processing and marking.

In this embodiment, the present invention is applied to the harmonic generator 1 for generating the second harmonic β, but it can also be applied to the harmonic generator for generating the fourth harmonic. However, in that case, it is necessary to use the non-linear optical element 3 (for example, BBO; β-BaB ₂ O ₄ ) or the film 4b having an optical property corresponding thereto.

[0016]

As described above, according to the present invention, since the filter is a convex lens, the reflected light of the filter is divergent light according to the convex shape. Therefore,
Unlike the conventional case, the reflected light of the filter does not directly enter the nonlinear optical element, and the reflected light of the filter does not damage the nonlinear optical element or make the output unstable.

Further, since the condenser lens is provided between the laser light source and the nonlinear optical element, the energy density of the laser light incident on the nonlinear optical element can be increased. Therefore, it is possible to generate harmonics with high efficiency even from laser light having a low energy density.

[Brief description of drawings]

FIG. 1 is a front view showing a configuration of a harmonic generator according to an embodiment of the present invention and a usage state thereof.

FIG. 2 is a front view showing a configuration of a conventional harmonic generator and a usage state thereof.

FIG. 3 is a diagram showing the dependence of the conversion efficiency E of a nonlinear optical element on the energy density P of laser light.

[Explanation of symbols]

 1 Harmonic Generator 2 Plano-Convex Lens (Condenser Lens) 3 Nonlinear Optical Element 4 Plano-Convex Lens Filter 5 Laser Light Source α Fundamental Wave β Second Harmonic

Claims (1)

[Claims] 1. A non-linear optical element for converting a fundamental wave of laser light emitted from a laser light source into a harmonic wave, and a filter for reflecting the fundamental wave of the laser light transmitted through the non-linear optical element and transmitting the harmonic wave. In the harmonic generating device for laser light provided with, the filter is a lens having a convex surface that divergently reflects the fundamental wave and transmits the harmonic, and is provided between the laser light source and the nonlinear optical element. A harmonic generation device for laser light, comprising: a condenser lens that condenses the laser light and makes it enter the nonlinear optical element.