JP2002314180A - Laser oscillator and oscillating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser oscillator and an oscillating method for simultaneously oscillating two wavelengths of a basic wave and simultaneously and efficiently outputting two-fold higher harmonics. SOLUTION: In the laser oscillator which simultaneously oscillates a wavelength 1 and a wavelength 2 as the basic waves on the optical axis S of a laser resonator A, first non-linear crystal 7 and second non-linear crystal 8, which output the two-fold higher harmonics of the respective basic wave wavelengths, are arranged on both sides of a laser active medium 1 disposed on the optical axis. A dielectric which is highly reflected with respect to the basic wave and highly transmits wavelength conversion light by first non-linear crystal arranged nearest is vapor-deposited on a first vertical incident mirror 5 constituting the resonator. A dielectric which is highly reflected with respect to the basic wave and highly transmits wavelength conversion light by second non-linear crystal arranged nearest is vapor-deposited on a second vertical incident mirror 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser oscillator which oscillates two wavelengths simultaneously and an oscillation method, and more particularly to a simultaneous oscillation configuration of a second harmonic and its means.

[0002]

2. Description of the Related Art Means for simultaneously oscillating two wavelengths as fundamental waves in a laser oscillator and outputting the sum wavelength (SF)
An example in which G) is provided in the resonator is reported to International Association CLEO90 as lecture number CFW5.

[0003] Also, JP-A-11-233868 discloses that
A nonlinear optical crystal for generating a second harmonic is provided on a resonance optical path inside the resonator, and when excitation energy exceeding an oscillation threshold is supplied from an excitation light source to a laser medium, laser oscillation starts and the second harmonic is generated. A technique for obtaining a laser beam is disclosed.

[0004] As a two-wavelength simultaneous selection means, by applying a drive voltage of any one frequency, the second harmonic laser light corresponding to the remaining two frequencies is simultaneously obtained.

Japanese Patent Application Laid-Open Nos. 7-142804 and 7-140501 disclose a technique for causing a fundamental wave to resonate in a resonator and converting a part of the fundamental wave to a second harmonic. .

This type of harmonic generation device can be applied to a high-precision optical measurement device that requires two wavelengths of laser light at the same time. Specifically, it is used as a light source for a dust counter in air or gas. It is stated to be valid.

[0007]

However, depending on the application conditions, it is required to oscillate at two wavelengths as a fundamental wave, and to simultaneously output the respective second harmonics efficiently at the same time. There is nothing to satisfy.

For example, in Japanese Patent Application Laid-Open No. 11-233868, a plurality of nonlinear optical crystals are sequentially arranged on an optical axis, and each nonlinear optical crystal generates a second harmonic of each wavelength with respect to each fundamental wave. The wavelength conversion function is performed.

Each nonlinear optical crystal and the mirrors at both ends of the resonator form an output coupling within the resonator. Conditions for efficiently outputting the second harmonic laser light include the wavelength conversion efficiency of the nonlinear optical crystal. And the reflectivity of the mirror (total transmission efficiency).

However, the conversion efficiency of the above-mentioned nonlinear optical crystal is proportional to the electric field intensity. Since a plurality of nonlinear optical crystals are arranged on the same optical axis, not only the fundamental wave corresponding to each nonlinear optical crystal but also However, the fundamental wave which does not correspond also influences.

That is, in any of the nonlinear optical crystals, the electric field strength is deteriorated due to the uncorresponding fundamental wave. As a result, the optimum coupling is not formed and the second harmonic cannot be output efficiently at the same time.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. It is an object of the present invention to simultaneously oscillate a fundamental wave at two wavelengths and simultaneously output the respective second harmonics efficiently. And a method for oscillating the same.

[0013]

SUMMARY OF THE INVENTION In order to satisfy the above object, a first aspect of the present invention is a laser oscillator that oscillates two wavelengths simultaneously as fundamental waves on an optical axis of a laser resonator. Characterized in that two non-linear crystals for simultaneously outputting the second harmonic of each fundamental wave wavelength are located on both sides of the laser active medium.

In order to satisfy the above object, a second aspect of the present invention is a laser oscillator which simultaneously oscillates two wavelengths as fundamental waves on an optical axis of a laser resonator, wherein both sides of a laser active medium arranged on the optical axis are provided. At the same time, two non-linear crystals for outputting the second harmonic of each fundamental wave wavelength are located, and the mirror constituting the resonator is highly reflected with respect to the fundamental wave and is disposed closest to the resonator. High transmission with respect to the second harmonic caused by the nonlinear crystal.

[0015] Claim 3 is Claim 1 and Claim 2
The laser oscillator according to any one of the above, further comprising: an exciting unit that excites the laser active medium from a direction orthogonal to an optical axis direction.

According to a fourth aspect of the present invention, there is provided a laser oscillator which simultaneously oscillates two wavelengths as fundamental waves on an optical axis of a laser resonator, wherein both sides of a laser active medium disposed on the optical axis are provided. At the same time, two nonlinear crystals for outputting a second harmonic of each fundamental wave wavelength are located, and the mirrors constituting the resonator are composed of first and second normal incidence mirrors installed at both ends of the resonator. And at least first to fourth bending mirrors for bending the optical axis in the resonator, and between the first normal incidence mirror and the second bending mirror, the first wavelength is twice the first wavelength from the first normal incidence mirror. A first nonlinear crystal for outputting a harmonic is arranged, and the first nonlinear mirror is disposed on the optical axis of the cavity in the resonator, which is constituted by the first bending mirror and second, third, and fourth bending mirrors installed subsequently thereto. A second non-linear crystal in which a laser active medium is installed on the other side and a second harmonic of a second wavelength is output from the second normal incidence mirror between the fourth bending mirror and the second normal incidence mirror; Is installed.

In order to satisfy the above object, a fifth aspect of the present invention is a laser oscillator which oscillates two wavelengths simultaneously as fundamental waves on an optical axis of a laser resonator, wherein both sides of a laser active medium arranged on the optical axis are provided. At the same time, two nonlinear crystals for outputting a second harmonic of each fundamental wave wavelength are located, and the mirrors constituting the resonator are composed of first and second normal incidence mirrors installed at both ends of the resonator. And at least a first to a fourth bending mirror for bending the optical axis in the resonator, and a first normal incidence mirror and a second normal mirror between the first normal incidence mirror and the second normal mirror. A first nonlinear crystal for outputting a second harmonic of the first wavelength from the first bending mirror and the second, third,
A laser active medium is provided at any point on the optical axis of the cavity in the cavity constituted by the fourth bending mirror, and a second normal incidence mirror is provided between the fourth bending mirror and the second normal incidence mirror. And a second nonlinear crystal for outputting a second harmonic of the second wavelength from the fourth bending mirror is provided.

As claim 6, claims 4 and 5
The laser oscillator according to any one of the above, further comprising: an exciting means for exciting the laser active medium through a bending mirror arranged on both sides of the laser active medium.

As claim 7, claims 3 and 6
In the laser oscillator described in any one of the above, the excitation means irradiates a laser beam.

[0020] In order to satisfy the above object, the invention of claim 8 provides a laser oscillation method, comprising:
In addition, two harmonics of each fundamental wave wavelength are simultaneously output from two nonlinear crystals on both sides of the laser active medium.

According to a ninth aspect of the present invention, there is provided a laser oscillation method comprising the steps of:
In addition, the two nonlinear crystals on both sides of the laser active medium simultaneously output the second harmonic of each fundamental wave wavelength, reflect the fundamental wave highly from the mirrors at both ends of the resonator, and use the nonlinear crystal arranged closest. It is characterized by high transmission of the second harmonic.

According to a tenth aspect, in the laser oscillation method according to any one of the eighth and ninth aspects, the method is applied to remote sensing as a laser radar by using a laser beam that outputs a double harmonic at two wavelengths simultaneously. Features.

According to the first to tenth aspects of the present invention, by adopting the means for solving the above problems, two wavelengths are oscillated simultaneously via only necessary elements,
In addition, the respective second harmonics can be efficiently output to the outside of the resonator at the same time.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows the configuration of the laser oscillator according to the first embodiment.

In the center of the figure, a laser active medium 1 is arranged. For example, Ti: Saphire leather is used as the laser active medium 1 and has a wavelength of 500 n.
pump laser light oscillating at a wavelength of 540 nm from m
To be excited by

The above-mentioned excitation laser beams 2 and 3 are supplied to a separately provided first laser beam oscillation section (excitation means) 2A and a second laser beam oscillation section (excitation means) 2A.
The laser beam is oscillated from the laser light oscillating section (excitation means) 3A, and its oscillation direction is a direction orthogonal to the optical axis S formed in the laser active medium 1.

A first mirror 5 is arranged on the optical axis S at the right end of the laser active medium 1 in the figure, and a second mirror 4 is arranged on the optical axis at the right end. The first mirror 5 and the second mirror 4 form a resonator A, and the mirrors 4 and 5 oscillate a fundamental wave.

Further, a two-wavelength transmission filter 6 is arranged on the optical axis S between the laser active medium 1 and the first mirror 5 in the resonator A. Therefore, in the resonator A, a 780 nm laser beam having a wavelength of 1 and a 830 nm laser beam having a wavelength of 2 are oscillated as fundamental wave oscillating lights.

On the optical axis S between the two-wavelength transmission filter 6 and the first mirror 5, a first nonlinear crystal 7 is arranged. The first non-linear crystal 7 is formed of a crystal material selected with respect to the wavelength 1 at a selected cutting angle.

On the optical axis S between the laser active medium 1 and the second mirror 4, a second nonlinear crystal 8 is arranged. The second nonlinear crystal 8 is formed of a crystal material selected for the wavelength 2 at a selected cutting angle.

The first mirror 5 constituting the resonator A
Is made of a dielectric material that is highly reflective by two fundamental waves (wavelengths 1 and 2) and highly transparent to light 10 having a wavelength of 390 nm, which is a second harmonic of wavelength 1.

The second mirror 4 is formed of a dielectric material that reflects the two fundamental waves (wavelengths 1 and 2) with high reflectivity, and that is highly transmissive with respect to the second harmonic 415 nm of the wavelength 2 at 415 nm. It has been done.

The laser oscillator constructed as described above is composed of a first laser light oscillating section 2A and a second laser light oscillating section 3A.
Oscillation as a fundamental wave occurs in the laser active medium 1 by the excitation laser light oscillating at nm.

At this time, the two-wavelength transmission filter 6 installed in the resonator A oscillates 780 nm as the wavelength 1 and 830 nm as the wavelength 2 as the fundamental wave oscillation.

The first non-linear crystal 7 is formed with a crystal material and a cutting angle selected with respect to wavelength 1.
Further, since the first mirror 5 highly reflects the fundamental waves of the wavelengths 1 and 2 and makes high transmission of the 390 nm light of the second harmonic of the wavelength 1, the first mirror 5 transmits the second harmonic 390n.
m light 10 is output.

The second non-linear crystal 8 is formed with a crystal material selected for the wavelength 2 and a cutting angle.
In addition, the second mirror 4 reflects the fundamental waves of the wavelengths 1 and 2 with high reflectivity and makes high transmission with respect to the 415 nm light of the second harmonic of the wavelength 2, so that the second harmonic 415n is transmitted from the second mirror 4 to the second harmonic 415n.
The m light 9 is output.

As described above, two wavelengths are simultaneously oscillated as fundamental waves, and the two fundamental wavelengths are simultaneously emitted on the optical axis S in the laser resonator A and on both sides of the laser active medium 1.
Two non-linear crystals 7, 8 for outputting a harmonic are arranged.

The first mirror 5 constituting the resonator A
And the second mirror 4 is a non-linear crystal which is highly reflected with respect to the fundamental wave and is disposed closest in the resonator, ie, the first mirror 5 has the first non-linear crystal 7 and the second non-linear crystal.
The mirror 4 has such a characteristic that the second nonlinear crystal 8 is highly transmitted to the second harmonic generated by each crystal.

As a result, the wavelength 1
Is output, and at the same time, a second harmonic light 9 having a wavelength of 2 is output from the second mirror 4. That is, two wavelengths are oscillated at the same time via only necessary elements,
The second harmonic can be output simultaneously and efficiently out of the resonator A.

Further, since the laser active medium 1 is provided with the first laser light oscillating portion 2A and the second laser light oscillating portion 3A that excite from a direction orthogonal to the optical axis S direction, the excitation laser light is It does not pass through the first and second nonlinear crystals 7 and 8 and therefore does not need to be absorbed, and has high excitation efficiency.

Next, a second embodiment of the present invention will be described with reference to FIG.

The laser active medium 11 is arranged on the optical axis Sa in the resonator Aa. This laser active medium 1
For example, a Ti: Saphire laser is used as 1 and is excited by pump laser beams 21 and 22 oscillating at wavelengths from 500 nm to 540 nm.

The resonator Aa is composed of a plurality of mirrors. That is, the first normal incidence mirror 12 and the second normal incidence mirror 17 installed at both ends of the resonator Aa,
It comprises at least a first bending mirror 13 to a fourth bending mirror 16 which form a zigzag optical axis Sa between the normal incidence mirrors 12 and 17.

In other words, the first folding mirror 1
The laser active medium 11 is disposed on the optical axis Sa in the cavity Aa including the third mirror 3 and the second, third, and fourth bending mirrors 14 to 16 disposed subsequently thereto.

Here, the laser active medium 11 includes a second bending mirror 14 and a third bending mirror 15.
And is located between. These second and third bending mirrors 14 and 15 are deposited with a dielectric material that is highly reflective to the fundamental wave and highly transparent to the wavelengths of the excitation laser beams 21 and 22.

One of the excitation laser beams 22 transmits the optical axis S of the second bending mirror 14 to the laser active medium 11.
The laser beam is oscillated from a first pump laser oscillating section (excitation means) 22A disposed on the opposite side to the point a.

The other excitation laser beam 21 has an optical axis S with respect to the laser active medium 11 of the third bending mirror 15.
The laser beam is oscillated from a second pump laser oscillating section (excitation means) 21A disposed on the opposite side to the point a.

First folding mirror 13 in resonator Aa
A two-wavelength transmission filter 18 is provided between the second bending mirror 14 and the second bending mirror 14.
It oscillates at 80 nm (wavelength 1) and 830 nm (wavelength 2).

On both sides of the laser active medium 11, two non-linear crystals 19 and 20 for simultaneously outputting the second harmonic of each fundamental wave wavelength are arranged. That is, between the first normal incidence mirror 12 and the first bending mirror 13,
A first nonlinear crystal 19 for outputting a second harmonic of the first wavelength from the first normal incidence mirror 12 is arranged.

The second vertical incidence mirror 1 is located between the fourth bending mirror 16 and the second vertical incidence mirror 17.
A second nonlinear crystal 20 for outputting a second harmonic of the second wavelength from 7 to the second wavelength is provided.

The first non-linear crystal 19 is formed with the crystal material selected for wavelength 1 and the cutting angle, and the second non-linear crystal 20 is formed with the crystal material selected for wavelength 2 and the cutting angle. Is formed.

The first normal incidence mirror 12 disposed at one end of the resonator Aa has high reflection at two fundamental waves (wavelengths 1 and 2), and is high with respect to 390 nm light, which is the second harmonic of wavelength 1. Dielectric deposition is performed so as to be transparent.

The second normal incidence mirror 17 disposed at the other end of the resonator Aa is a dielectric material which has high reflection by two fundamental waves and high transmission with respect to light having a second harmonic of wavelength 415 nm. Body deposition has been performed.

In the laser oscillator configured as described above, the excitation laser light is oscillated from the first laser light oscillation part 22A and the second laser light oscillation part 21A.
These excitation laser beams are supplied to the second bending mirror 14.
Then, the light passes through the third bending mirror 15 and is guided to the laser active medium 11.

The laser active medium 11 has a wavelength of 500 nm.
Laser light 22,2 oscillating at a wavelength of 540 nm from
1 and the first to fourth bending mirrors 13 to 16 oscillate as fundamental waves.

The two-wavelength transmission filter 18 disposed on the optical axis Sa oscillates 780 nm (wavelength 1) and 830 nm (wavelength 2) as fundamental wave oscillation light. Then, depending on the selection conditions of the first and second nonlinear crystals 19 and 20, the second normal harmonic 3 of the wavelength 1
The 90 nm light 23 is output, and the second normal incidence mirror 17 is output.
, A 415-nm light 24 of the second harmonic of the wavelength 2 is output.

As a result, the first and second normal incidence mirrors 12 and 17 and the first to fourth bending mirrors 1
While the zigzag optical axis Sa is formed by 3 to 16, two wavelengths are oscillated at the same time via only necessary elements, and the second harmonic can be output simultaneously and efficiently out of the resonator Aa.

Further, since the excitation laser beams 22 and 21 are guided to the laser active medium 11 without passing through the first and second nonlinear crystals 19 and 20,
Excitation laser light is not absorbed by each of the nonlinear crystals 19 and 20, and the excitation efficiency is good.

FIG. 3 shows a third embodiment of the present invention. As will be described later, only the characteristics of the first bending mirror 13A and the fourth bending mirror 16A are different, there is no difference in the components other than these mirrors, and there is no difference in the arrangement of the components. Since there is no change, the same numbers are assigned and new explanations are omitted.

Accordingly, the same applies to the case where the second harmonic light 23 having the wavelength 1 is output from the first normal incidence mirror 12 and the second harmonic light 24 having the wavelength 2 is output from the second normal incidence mirror 17. .

Here, the first bending mirror 13A
Is a high reflection of the fundamental wave and a wavelength of 2
Dielectric deposition is performed so as to have a high transmission with respect to the light 23 of the 390 nm harmonic.

Further, the fourth bending mirror 16A is
Dielectric deposition is performed so as to have high reflection with respect to the fundamental wave and high transmission with respect to the light 24 having a wavelength of 415 nm, which is the second harmonic of wavelength 2.

Therefore, the second harmonic light 23 of the wavelength 1 is output from the first normal incidence mirror 12 and also from the first bending mirror 13A. at the same time,
The second harmonic light 24 of the wavelength 2 is transmitted to the second normal incidence mirror 17.
And the fourth bending mirror 16A
Is also output from In this way, the output units of the second harmonics 23 and 24 of the wavelengths 1 and 2 are increased as compared with the second embodiment, and the adaptation conditions as a laser oscillator are expanded.

The second embodiment (FIG. 2) and the third
In the embodiment (FIG. 3), the excitation laser light 2
The second and the second mirrors are transmitted through the second bending mirror 14 and the third bending mirror 15 to be excited from the end face of the laser active medium 11, but the present invention is not limited to this. As described in the embodiment (FIG. 1), excitation may be performed from a side surface direction orthogonal to the axial direction of the laser active medium 11.

In addition, the laser light which outputs two harmonics simultaneously at two wavelengths can be used as a light source of a remote sensing device such as a laser radar.

[0066]

As described above, according to the present invention, it is possible to oscillate two wavelengths simultaneously from a single oscillator and simultaneously output the respective second harmonic light, thereby expanding the application range. Play.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a laser oscillator according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a laser oscillator according to a second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a laser oscillator according to a third embodiment of the present invention.

[Explanation of symbols]

 4, 5 ... (first and second) resonator mirrors, 7 ... first nonlinear crystal (for wavelength 1), 8 ... second nonlinear crystal (for wavelength 2), 1 ... laser active medium, 12 ... 1st perpendicular incidence mirror, 17 ... 2nd perpendicular incidence mirror, 13-16 ... 1st-4th bending mirror, 11 ... Laser active medium.

Claims (10)

[Claims] 1. A fundamental wave having a wavelength of 2
In a laser oscillator that oscillates two wavelengths simultaneously, two nonlinear crystals that simultaneously output a second harmonic of each fundamental wavelength are positioned on both sides of a laser active medium disposed on an optical axis. Laser oscillator. 2. The method according to claim 1, wherein the fundamental wave is 2
In a laser oscillator that oscillates two wavelengths at the same time, two nonlinear crystals that simultaneously output the second harmonic of each fundamental wave wavelength are located on both sides of a laser active medium arranged on the optical axis, A laser oscillator comprising: a mirror configured to highly reflect a fundamental wave and highly transmit to a second harmonic light by the nonlinear crystal disposed closest in the resonator. 3. The laser oscillator according to claim 1, further comprising an exciting unit for exciting the laser active medium from a direction orthogonal to an optical axis direction. 4. A fundamental wave having a wavelength of 2
In a laser oscillator that oscillates two wavelengths at the same time, two nonlinear crystals that simultaneously output the second harmonic of each fundamental wave wavelength are located on both sides of a laser active medium arranged on the optical axis, The mirror comprises first and second normal incidence mirrors provided at both ends of the resonator, and at least first to fourth bending mirrors for bending the optical axis in the resonator. A first nonlinear crystal for outputting a second harmonic of the first wavelength from the first normal incidence mirror is disposed between the second bending mirrors. A laser active medium is installed on the optical axis of the cavity in the cavity constituted by the third and fourth bending mirrors, and between the fourth bending mirror and the second normal incidence mirror.
A laser oscillator comprising a second non-linear crystal for outputting a second harmonic of a second wavelength from a second normal incidence mirror. 5. A fundamental wave on the optical axis of the laser resonator as 2
In a laser oscillator that oscillates two wavelengths at the same time, two nonlinear crystals that simultaneously output the second harmonic of each fundamental wave wavelength are located on both sides of a laser active medium arranged on the optical axis, The mirror comprises first and second normal incidence mirrors provided at both ends of the resonator, and at least first to fourth bending mirrors for bending the optical axis in the resonator. A first nonlinear crystal that outputs a second harmonic of a first wavelength from each of the first normal incidence mirror and the second folding mirror, between the second folding mirror; A laser active medium is installed on any one of the optical axes of the cavity in the cavity formed by the second, third, and fourth bending mirrors that are subsequently provided, and a fourth bending is performed. Between the mirror and the second normal incidence mirror,
A laser oscillator comprising a second nonlinear crystal for outputting a second harmonic of a second wavelength from the second normal incidence mirror and the fourth bending mirror. 6. The laser-active medium according to claim 4, further comprising: an exciting means for exciting the laser-active medium through a bending mirror disposed on both sides of the laser-active medium. Laser oscillator. 7. The laser oscillator according to claim 3, wherein said excitation means irradiates a laser beam. 8. A laser oscillation method comprising simultaneously outputting a second harmonic of each fundamental wave wavelength from two nonlinear crystals on an optical axis of a laser resonator and on both sides of a laser active medium. 9. Two harmonics of each fundamental wave wavelength are simultaneously output from two nonlinear crystals on the optical axis of the laser cavity and on both sides of the laser active medium, and a fundamental wave is output from mirrors at both ends of the cavity. A laser oscillation method characterized by high reflection and high transmission of a second harmonic by a nearest non-linear crystal. 10. The laser oscillation method according to claim 8, wherein the laser beam is applied to remote sensing as a laser radar by using a laser beam that outputs two harmonics at two wavelengths at the same time.