JPH06241908A - Wavelength measuring method, wavelength measuring apparatus using the same, and laser apparatus - Google Patents

Abstract

(57) [Summary] [Purpose] 1.08 using only a single detector
It is an object of the present invention to provide a wavelength measuring method of laser light in a wavelength region of 3.3 μm, a wavelength measuring device using the same, and a laser device using the same. [Structure] A laser beam 5 is incident on a nonlinear optical element 11 for sum frequency generation, and a wavelength of the generated sum frequency light 13 is obtained.
From the wavelength of the sum frequency light 13, the wavelength of the laser light 5 incident on the sum frequency generating nonlinear optical element 11 is obtained. [Effects] Laser light of a wide range of wavelengths can be measured easily, quickly, and continuously, and the device can be downsized. Further, by using the laser device of the present invention, laser light of various wavelengths can be arbitrarily generated from a single laser device, and the wavelength of the generated laser light can be confirmed at any time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to measurement of the wavelength of laser light emitted from a wavelength tunable laser device using an optical parametric oscillator.

[0002]

2. Description of the Related Art It is well known that when coherent pumping light (λp) is incident on a nonlinear optical element (crystal), coherent light having different wavelengths satisfying the following equation is generated. It is called the parametric effect. Formula 1 1 / λp = 1 / λs + 1 / λi Formula 2 np / λp = ns / λs + ni / λi where λs is signal light, λi is idler light, and λs <λi. Furthermore, np, ns, ni
Indicates the refractive index of the non-linear optical element for each light.

As shown in FIG. 3, the oscillator using the optical parametric effect is provided with a pumping light source 1, a nonlinear optical element 2 for optical parametric oscillation, and an incident side and an emitting side of the nonlinear optical element 2. And a pair of reflecting mirrors 3 and 4. The mechanism of action is as follows.

The laser light 5 emitted from the excitation light source resonates between a pair of reflecting mirrors 3 and 4 provided in the nonlinear optical element 2 for optical parametric oscillation, the wavelength is converted, and the converted wavelength is reflected by the reflecting mirror 4. Is emitted.

Conventionally, KTiO ₄ (KTP), Rb has been used as the nonlinear optical element 2 for inducing optical parametric oscillation of this type.
A nonlinear optical crystal such as TiOPO ₄ (RTP) is used, and the excitation light source has a wavelength of 1.047 to 1.079.
Nd-doped YLF and Nd-doped YA oscillating at 6 μm
Solid-state laser devices using laser rods such as G, Nd-doped GSGG, and Nd-doped YAP are widely used.

By the way, the laser light is characterized in that it has a narrow wavelength distribution and good straightness, and the wavelength of the laser light oscillated is specified by the material of the laser rod used. In recent years, a device that can oscillate laser light of various wavelengths from one device while taking advantage of the good straightness of this laser light and the narrow wavelength distribution, and a wavelength in a region where the current laser rod cannot oscillate There has been an increasing demand for a device that can. For example, it is used for detecting and quantifying various harmful components in the atmosphere.

Various investigations have been made to meet such requirements. For example, there is one that uses an optical parametric oscillator using KTP or RTP to change the propagation angle of laser light in a nonlinear optical element in the oscillator. This is because in optical parametric oscillation using KTP or RTP, by changing the propagation angle in the range of 40 to 90 degrees (up to 50 ° as the variation amount of the propagation angle), for example, the wavelength of 1.
The incident laser light of 064 μm has a wavelength of 1.08 to 3.3 μm.
This is because the wavelength can be converted into the laser light of.

In this way, it is necessary to verify whether the laser light obtained by wavelength conversion has an initial target wavelength. For example, FIG. 4 is an example of a conceptual diagram showing the basic configuration of a conventional measuring device, and includes a monochromator 6 and
An incident light 9 as a light to be measured reaches the detector 7 through the monochromator 6, which is composed of a detector 7 and a computer 8, and indicates the rotation amount of a diffraction grating (not shown) in the monochromator 6. The output signal and the output signal of the detector 7 are input to the computer 8, and the wavelength of the incident light 9 is determined based on these input signals.

When it is attempted to measure laser light in a wide wavelength range of 1.08 to 3.3 μm with a measuring device using such a conventional monochromator 6, a detector 7 used in the measuring device is used. The detector 7 made of Si, InSb, PbS, and Ge had to be sequentially replaced according to the wavelength to be measured. From the sensitivity of the detector, the optical parametric oscillator has a pulse width of several tens of ns.
Since the excitation light of ec is used, the rising speed is as slow as several μsec or more, except for the detector made of Si or InSb, and it is impossible to measure only by irradiating the detector with one laser light pulse. In addition, all the detectors other than the detector made of Si cannot obtain sufficient sensitivity unless the detection element itself is cooled, and a cooling device and a temperature control device for this purpose are indispensable. It was difficult to miniaturize itself.

[0010]

The present invention has been made in view of the above situation, and measures the wavelength of laser light in the wavelength range of 1.08 to 3.3 μm using only a single detector. An object is to provide a method, a wavelength measuring device using this measuring method, and a laser device using this wavelength measuring device.

[0011]

According to the wavelength measuring method of the present invention for solving the above problems, a laser beam is incident on a nonlinear optical element for sum frequency generation, the wavelength of the generated sum frequency light is determined, and the sum frequency light The wavelength of the incident laser light is obtained from the wavelength, and the wavelength measuring apparatus of the present invention using this method is a sum frequency generation nonlinear optical element on the laser light incident side of a monochromator, or a sum through a beam splitter. A non-linear optical element for frequency generation is provided, and the laser device of the present invention is configured using an excitation light source, an optical parametric oscillator, a non-linear optical element for sum frequency generation, and a beam splitter. A laser beam emitted from an optical parametric oscillator is incident on a nonlinear optical element for generating a sum frequency, which is composed of the wavelength measuring device of the present invention. The incident laser light is emitted to the outside of the system,
The sum frequency light is configured to be incident on the monochromator.

[0012]

The method of the present invention is suitable for measuring the wavelength of laser light in the wavelength range of 1.08 to 3.3 μm. This is because when laser light in this wavelength range is incident on the nonlinear optical element for sum frequency generation, the wavelength of the sum frequency light generated is 0.536-0.
It is 806 μm, and the wavelength can be measured only by using a Si detector as a sensor. That is, an Nd-doped YAG laser (wavelength (λ
p) = 1.064 μm) to explain the method of the present invention, the laser light follows the equations 1 and 2 by changing the propagation angle in the nonlinear optical element in the optical parametric oscillator. Wavelength 1.622 to 1.652μ
It is possible to generate the signal light A of m and the idler light B of wavelength 3.092 to 2.989 μm. When these lights A and B pass through the nonlinear optical element for generating the sum frequency, wavelengths of 0.643 to 0.64 satisfying the expression 3 are satisfied.
7 μm sum frequency light (λsf) A ′ and wavelength 0.792 to
0.785 μm sum frequency light (λsf) B ′ is generated. Formula 3 λs = 1 / (1 / λsf-1 / λp)

Therefore, the laser light emitted from the nonlinear optical element for sum frequency generation is a mixed light (A + A ', B + B') of the signal light A, the idler light B, and the sum frequency light A ', B'. In the present invention, the wavelength of the sum frequency light in this mixed light is measured, and the wavelengths of the signal light and the idler light are obtained by the equation 3. In addition, in order to measure the wavelength of the sum frequency light with higher accuracy, it is preferable to provide a beam splitter between the nonlinear optical element for generating the sum frequency and the monochromator.

As the apparatus after the monochromator applied to the method of the present invention, a commercially available apparatus can be used as it is without any problem, and there is no particular limitation. Hereinafter, a wavelength measuring device using the method of the present invention and a laser device using the wavelength measuring device will be described based on examples.

[0015]

【Example】

(Embodiment 1) FIG. 1 is a conceptual diagram of an example of a wavelength measuring device of the present invention. This apparatus comprises a monochromator 6, a detector 7 made of Si for detecting the light taken out from the monochromator 6, and an output of the monochromator 6 and a computer 8 for obtaining the wavelength of the incident light 9 from the output of the detector 7. And the rotary stage 10 provided on the incident light side of the monochromator 6.
It is composed of a nonlinear optical element 11 for generating a sum frequency (hereinafter abbreviated as “sum frequency generating element”) installed above, and a beam splitter 12 provided between the rotary stage 10 and the monochromator 6. Is a wavelength measuring device, and the type 11 (50 ° ≦ θ
≦ 90 °, φ = 0 ° where θ is the polar coordinate angle measured from the x (a) axis, and φ is the polar coordinate angle measured from the Z (c) axis. ) Cut KTP crystal was used. The beam splitter 12 used in this device has a high transmittance for only the sum frequency light 13,
It has a high reflectance for the incident light 9.

In this apparatus, the incident light 9 passes through the sum frequency generating element 11, passes through the beam splitter 12, and reaches the monochromator 6. During this time, a part of the incident light 9 is wavelength-converted by the sum frequency generating element 11 and is emitted from the element 11 as a mixed light 14 of the sum frequency light 13 and the incident light 9. The mixed light 14 is split into a sum frequency light 13 and an incident light 9 by a beam splitter 12, the sum frequency light 13 is incident on the monochromator 6, and the incident light 9 is emitted outside the system.

The monochromator 6 rotates an internal diffraction grating (not shown) to disperse the incident sum frequency light 13 and emits it to the detector 7. This emitted sum frequency light 13
The output of the detector 7 and the output from the monochromator 6 are input to the computer 8, and the wavelength of the sum frequency light 13 is obtained from the rotation angle of the diffraction grating at which the output of the detector 7 is maximized. Based on this, the wavelength of the incident light 9 is obtained.

The sum frequency generating element 1 used in the present apparatus
KTP, RTP, KTA, BBO, or the like is used as 1, and either type 1 or type 2 is used depending on the polarization state of the incident light 9.

(Embodiment 2) FIG. 2 is a conceptual diagram showing the construction of an example of a laser device of the present invention. An optical parametric oscillator is provided on the incident side of the sum frequency generating element 11 of FIG. The optical parametric oscillator is an excitation light source 1
And a non-linear optical element 2 for parametric oscillation, a rotary stage 15 on which the non-linear optical element 2 is mounted, and reflecting mirrors 3 provided on both sides of the rotary stage 15 on the incident side and the outgoing side of the nonlinear optical element 11 Shown as "rear mirror".)
And an optical parametric oscillator 16 including a reflecting mirror 4 (hereinafter, referred to as “output mirror”).

In this laser device, a solid-state laser device using an Nd-doped YAG crystal as an oscillation rod is used as the excitation light source 1, and a nonlinear optical element 2 for parametric oscillation is used.
As Type 2 (50 ° ≦ θ ≦ 90 °, φ = 0 °, where θ is the polar coordinate angle measured from the x (a) axis,
φ is the polar coordinate angle measured from the Z (c) axis. ), The rear mirror 3 has a high transmittance for the excitation laser light 5, and a high reflectance for the signal light (light having a wavelength shorter than twice the wavelength of the excitation laser light). The dichroic reflecting mirror is used, the dichroic reflecting mirror having a reflectance of 50 to 98% with respect to the signal light is used as the output mirror 4, and the sum frequency generating element 11 is of type 1 (50 ° ≦ 50 ° ≦
θ ≦ 90 °, 0 ° ≦ φ ≦ 50 ° where θ is the polar coordinate angle measured from the x (a) axis, and φ is the polar coordinate angle measured from the Z (c) axis. 1) using the KTP crystal cut in (1).

In the apparatus of the present invention, the pump laser light 5 emitted from the pump light source 1 oscillates in the parametric oscillator 16 and the signal light is incident as incident light 9 on the sum frequency generating element 11 together with the pump laser light 5. . The incident light 9 generates the sum frequency light 13 as described in Example 1, the wavelength is measured, and the wavelength of the output light (incident light 9) of the laser device is obtained from the result.

(Embodiment 3) A-cut (θ = 90 °, φ = 0 °) as the nonlinear optical element 2 for optical parametric oscillation
With an optical path length of 10 mm and a wavelength of 1.6 to 1.8
Optical parametric oscillation is performed by using a mirror that is in a single resonance state at μm, and the RTP is rotated by using the laser device of FIG. Was rotated from 90 ° to 70 and the wavelength of the generated sum frequency light 13 was measured. From this result, the wavelength of the signal light generated by the optical parametric oscillator was obtained. Then, the wavelength of the signal light at the same propagation angle was measured by a conventional measurement method using PbS as a detector.
The results are shown in Table 1. From the results of Table 1, it was found that there was no difference between the value measured by the method of the present invention and the method measured by the conventional method.

[0023]

[0024]

Industrial Applicability The method of the present invention, in which the sum frequency light is generated and measured, and the wavelength of the original laser light is obtained from the result, or the measuring apparatus using the method is used in a monochromator. Since the single detector can be made of Si, the laser light of a wide range of wavelengths can be continuously measured in a simple and quick manner, and the device can be downsized. Further, by using the laser device of the present invention, laser light of various wavelengths can be arbitrarily generated from a single laser device, and the wavelength of the generated laser light can be confirmed at any time.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an example of a wavelength measuring device of the present invention.

FIG. 2 is a conceptual diagram showing a configuration of an example of a laser device of the present invention.

FIG. 3 is a conceptual diagram showing a configuration of a laser oscillator using an optical parametric effect.

FIG. 4 is a conceptual diagram showing a configuration of a conventional wavelength measuring device.

[Explanation of symbols]

1--Excitation light source, 2 --- Nonlinear optical element for optical parametric oscillation, 3,4 --- Reflecting mirror, 5 --- Laser light, 6 ----
Monochromator, 7-detector, 8-computer, 9-incident light, 10, 15-rotating stage, 11
--- Nonlinear optical element for sum frequency generation, 12-- Beam splitter, 13-- Sum frequency light, 14-- Mixed light, 16--
− Optical parametric oscillator

Claims (3)

[Claims] 1. A laser light incident on a nonlinear optical element for sum frequency generation, a wavelength of the generated sum frequency light is obtained, and a laser light incident on the nonlinear optical element for sum frequency generation is calculated from the wavelength of the sum frequency light. A wavelength measuring method characterized by obtaining a wavelength. 2. A wavelength measuring device comprising a nonlinear optical element for generating a sum frequency or a nonlinear optical element for generating a sum frequency provided on a light receiving side of a monochromator via a beam splitter. 3. A laser emitted from an optical parametric oscillator, comprising a pumping light source, an optical parametric oscillator, a wavelength measuring device according to claim 2 configured by using a nonlinear optical element for generating a sum frequency, and a beam splitter. A laser device characterized in that light is incident on a nonlinear optical element for sum frequency generation, incident laser light is emitted outside the system by a beam splitter, and sum frequency light is incident on a monochromator.