JPH04125526A - Higher harmonic generation device - Google Patents

Abstract

PURPOSE:To offer the higher harmonic generation device which can switches a fundamental wave and higher harmonics through easy operation without any deviation in optical axis by obtaining the higher harmonics or fundamental wave selectively by rotating the plane of polarization of the linear polarized fundamental wave. CONSTITUTION:An incidence-side polarization beam splitter 2 and a projection-side polarization beam splitter 3 are arranged on the same optical axis so that the same polarized light component passes through them; and nonlinear crystal 4 which converts the fundamental wave into higher harmonics is arranged between the both and a 1st polarizing optical element 5 which rotates the plane of polarization of the linear polarized fundamental wave is arranged on the incidence surface side of the beam splitter 2. A 2nd polarizing optical element 7 which rotates the plane of polarization of the fundamental wave passed through the beam splitter 2 and a light guide means which guides the fundamental wave reflected by the beam splitter 2 to the same optical axis with the higher harmonics converted by the crystal 4 are provided between the beam splitter 2 and nonlinear crystal 4. Consequently, the polarized light component of light which is incident on the beam splitter 2 is changed by operating the polarizing optical element 5 to convert the light into higher harmonics through the crystal 4 and guide the fundamental wave out as it is not through the crystal 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention (Field of Industrial Application) This invention relates to a harmonic generation device that selectively converts laser light output from a laser device into a fundamental wave and harmonics.

(Prior Art) For example, when repairing wiring in a semiconductor process, the laser beam output from an Nd:YAG laser device is divided into a fundamental wave with a wavelength of 1.06 μm and a harmonic wave (harmonic wave) with a wavelength of 532 nm. It may be necessary to alternately use two harmonics (two harmonics). Conventionally, in such a case, a harmonic generator was attached to and detached from the output side of the laser device. That is, to switch the laser beam from harmonics to fundamental waves, it is sufficient to remove the harmonic generator from the laser device, but when to switch from the fundamental wave to harmonics, remove the harmonic generator from the laser device. Must be installed on the output side.

The above-mentioned harmonic generation device is formed of a nonlinear crystal and an optical element such as a mirror that reflects the fundamental wave and transmits the harmonic wave. Therefore, each time a harmonic generator is attached to the output side of a laser device, optical elements such as nonlinear crystals and mirrors must be aligned. Therefore, since it takes a lot of effort to install the harmonic generator, it is difficult to use it when switching between the fundamental wave and the harmonics must be performed frequently.

Furthermore, the harmonic generator may not be precisely aligned, resulting in misalignment of the optical axes of the fundamental wave and harmonics.

(Problem to be solved by the invention) In this way, in the past, the harmonic generator had to be attached and detached to switch between the fundamental wave and harmonics, which not only resulted in poor operability, but also caused the fundamental wave and harmonics to change. This has had problems such as the optical axis of the lens may shift.

This invention was made based on the above circumstances, and its purpose is to provide a harmonic generator that can switch between the fundamental wave and harmonics by simple operation without shifting the optical axis. It is about providing.

[Structure of the Invention (Means and Effects for Solving the Problems)] In order to solve the above problems, the present invention provides a polarizing beam splitter on the incident side and an output side that are arranged on the same optical axis so as to transmit the same polarized light components. a polarizing beam splitter, a nonlinear crystal that converts a fundamental wave into a harmonic, which is placed between the incident side polarizing beam splitter and the output side polarizing beam splitter, and a nonlinear crystal that is placed on the incident surface side of the incident side polarizing beam splitter and which is placed between the incident side polarizing beam splitter and the output side polarizing beam splitter. a first polarizing optical element that rotates the plane of polarization of the polarized fundamental wave; and a first polarizing optical element that rotates the plane of polarization of the fundamental wave that is disposed between the incident-side polarizing beam splitter and the nonlinear crystal and rotates the polarization plane of the fundamental wave that has passed through the incident-side polarizing beam splitter. It is characterized by comprising a second polarizing optical element to be rotated, and a light guiding means for guiding the fundamental wave reflected by the incident-side polarizing beam splitter onto the same optical axis as the harmonic wave converted by the nonlinear crystal. do.

According to such a configuration, by operating the first polarizing optical element to change the polarization component of the light incident on the incident-side polarizing beam splitter, the light can be passed through the nonlinear crystal and converted into harmonics. , it is possible to extract the fundamental wave as it is without passing it through a nonlinear crystal.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

A harmonic generation device 1 shown in FIG. 1 includes an input polarizing beam splitter 2 and an output polarizing beam splitter 3, which are placed on the same optical axis 0 and spaced apart from each other at a predetermined interval. These pair of beam splitters 2.3 are arranged so as to transmit the same polarized light component. That is, these beam splitters 2.3 are arranged so as to transmit the p-polarized light of the linearly polarized light wave traveling along the optical axis O, and reflect the S-polarized light.

A nonlinear crystal 4 for converting the fundamental wave into a second harmonic is arranged between the incident side polarizing beam splitter 2 and the output side polarizing beam splitter 3. This nonlinear crystal 4 has TYPE I for the incident fundamental wave of wavelength ω.
When a fundamental wave of S-polarized light is incident, a part of the fundamental wave is converted to p of wavelength 2ω.
It is designed to convert into the second harmonic of polarized light.

On the incident surface side of the incident side polarizing beam splitter 2, a first (λ/2) plate 5 serving as a first optical polarizing element that rotates the polarization plane of the linearly polarized fundamental wave by 90 degrees is arranged so that the optical axis O is It is rotatably provided around the center by a support mechanism (not shown). A laser beam L (fundamental wave) output from the Nd:YAG laser device 6, for example, which is linearly polarized light, enters the first (λ/2) plate 5. This laser light is converted into S-polarized light or p-polarized light depending on the rotation angle of the first (λ/2) plate 5, and enters the incident side polarizing beam splitter 2.

Between the exit surface side of the incident side polarizing beam splitter 2 and the incident surface side of the nonlinear crystal 4, there is a second optical system that converts the p-polarized fundamental wave transmitted through the incident side polarizing beam splitter 2 into S-polarized light. A second (λ/2) plate 7 as a polarizing element is arranged. A part of the fundamental wave converted into S-polarized light by this second (λ/2) plate 7 is converted into a harmonic (second harmonic) of p-polarized light by the nonlinear crystal 4 as described above, The light is transmitted through the polarizing beam splitter 3 on the output side.

The S-polarized laser beam L (fundamental wave) reflected by the incident-side polarizing beam splitter 2 is sequentially reflected by a first high-reflection mirror 8 and a second high-reflection mirror 9 arranged at an angle of 45 degrees. and enters the polarizing beam splitter 3 on the output side.

The S-polarized laser light incident on the output polarizing beam splitter 3 is reflected in the same optical axis O direction as the second harmonic transmitted through the output polarizing beam splitter 3.

Next, the operation of the harmonic generator having the above configuration will be explained. When the linearly polarized laser light L (fundamental wave) outputted from the laser device 6 enters the first (λ/2) plate 5, this laser light is deflected by the first (λ/2) plate 5. The plane of polarization is rotated to p-polarization. The fundamental wave of wavelength ω, which has become p-polarized light, passes through the incident-side polarizing beam splitter 2 and enters the second (λ/2) plate 7 . Thereby, p
The plane of polarization of the fundamental wave of polarized light is rotated to S-polarized light. The S-polarized fundamental wave is incident on the nonlinear crystal 4, and part of it is converted into p-polarized second harmonic wave with a wavelength of 2ω.

The fundamental wave and second harmonic wave emitted from the nonlinear crystal 4 enter the polarizing beam splitter 3 on the output side.

This exit-side polarizing beam splitter 3 reflects the S-polarized fundamental wave and transmits the p-polarized second harmonic.

Therefore, the second harmonic is emitted coaxially with the optical axis O from the output side polarizing beam splitter 3.

On the other hand, when emitting a fundamental wave of wavelength ω in the 0 direction of the optical axis, the first (λ/2) plate 5 is rotated by 45 degrees from the state shown in FIG. 1 in which the second harmonic is obtained. As a result, the laser light consisting of the fundamental wave of wavelength ω that is incident on the first (λ/2) plate 5 is converted into S-polarized light and emitted. The S-polarized fundamental wave is reflected without passing through the incident-side polarizing beam splitter 2. The S-polarized fundamental wave reflected by the incident-side polarizing beam splitter 2 is reflected by the first high-reflection mirror 8 and the second high-reflection mirror 9, as shown in FIG. incident on . This exit-side polarizing beam splitter 3 reflects S-polarized light and transmits p-polarized light, so S
The fundamental wave of polarized light is reflected in the direction of the optical axis O.

In this way, the harmonic generator 1 configured as described above rotates the polarization plane of the first (λ/2) plate 5 by J44 degrees and converts the laser beam output from the laser device 6 into p-polarized light. , the second harmonic with a wavelength of 2ω can be output on the optical axis 0. Also, from the state where the second harmonic is obtained, the first (λ/2) plate 5 is If you rotate the laser beam to make it S-polarized, it becomes a wave.

A fundamental wave whose length is ω can be output on the optical axis O.

In other words, the fundamental wave or the second harmonic can be selectively output by simply rotating the first (λ/2) plate 5 without attaching or detaching the harmonic generator 1 to the output side of the laser device 6. be able to. Therefore, since there is no need to attach or detach the harmonic generator 1 to the output side of the laser device 6, the fundamental wave or the second harmonic can be selected quickly, and alignment is not required, which improves operability. Good.

In addition, since the fundamental wave of S-polarized light included in the second harmonic of p-polarized light is separated by the output-side polarization beam splitter 3, the separation ratio is lower than in the case of separation using a multilayer mirror. can be significantly improved.

Note that the present invention is not limited to the above embodiment; for example, as the first and second polarization optical elements for rotating the polarization plane of laser light, a magnetic field may be applied to a crystal instead of a (λ/2) plate. It may be a Faraday rotator that rotates the plane of polarization with a 200-degree angle, or it may be a Pockels cell, a Kersel, or the like that can rotate the plane of polarization by applying an electric field. Further, when the light incident on the first polarizing optical element is non-polarized light such as natural light, a polarizer that linearly polarizes the natural light may be installed on the incident surface side of the first polarizing optical element. Furthermore, the harmonic generator having the above configuration can be applied not only to the second harmonic but also to the fourth harmonic.

C Effects of the Invention C As described above, the present invention makes it possible to selectively obtain harmonics or fundamental waves by rotating the plane of polarization of the linearly polarized fundamental wave. Therefore, compared to the conventional method in which the harmonic generator is attached and detached, harmonics or fundamental waves can be selected more easily and quickly, and the optical axis does not shift due to attachment and detachment.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a block diagram of the entire apparatus showing a state in which the second harmonic is extracted, and FIG. 2 is a block diagram of the entire apparatus showing a state in which the fundamental wave is extracted. 2... Incoming side polarizing beam splitter, 3... Outgoing side polarizing beam splitter, 4... Nonlinear crystal, 5...
j! ! 1 (λ/2) plate (first polarizing optical element), 7.
... second (λ/2) plate (second polarizing optical element), 8. 9... High reflection mirror (light guide means -)

Claims (1)

[Claims] An input side polarized beam splitter and an output side polarized beam splitter are arranged on the same optical axis so as to transmit the same polarized light component, and a fundamental wave is arranged between the input side polarized beam splitter and the output side polarized beam splitter. a nonlinear crystal that converts into harmonics; a first polarizing optical element that is arranged on the incident surface side of the incident side polarizing beam splitter and rotates the plane of polarization of the linearly polarized fundamental wave; the above incident side polarizing beam splitter; a second polarizing optical element that is placed between the nonlinear crystal and rotates the plane of polarization of the fundamental wave that has passed through the incident-side polarizing beam splitter; and the fundamental wave reflected by the incident-side polarizing beam splitter is converted by the nonlinear crystal. A harmonic generation device comprising a light guide means for guiding the harmonics onto the same optical axis.