JP2002287190A - Infrared light generator - Google Patents

Abstract

(57) [Summary] [Problem] To provide a compact, high-output infrared light generator capable of wavelength tuning. In an infrared light generating apparatus that emits two types of excitation light having different wavelengths into a nonlinear optical crystal and mixes them to generate an infrared light by generating a difference frequency, a short wavelength side incident on the nonlinear optical crystal is used. N as the light source of the excitation light of the first wavelength
d: Using a YAG laser 12 as a light source for the excitation light of the second wavelength on the long wavelength side incident on the nonlinear optical crystal 10,
An r: forsterite laser 14 is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared light generator, and more particularly, to two types of excitation light having different wavelengths which are incident on a nonlinear optical crystal and mixed, and generate infrared light by a difference frequency generation. The present invention relates to an infrared light generator configured to generate light.

[0002]

2. Description of the Related Art Generally, wavelengths λ ₁ and λ ₂ (λ ₁ <λ
₂ ) By mixing the two pump lights in the nonlinear optical crystal, a longer wavelength λ ₃ (1 / λ ₃ = 1 / λ ₁ −1 /
The principle of the difference frequency generation of generating coherent light of λ ₂ ) is known.

Conventionally, two types of pumping lights having different wavelengths are made incident on a nonlinear optical crystal and mixed using the principle of the above-described difference frequency generation, and infrared light is generated by the difference frequency generation. Infrared light generators are known.

[0004] Specifically, 2
Regarding the light source of the excitation light having different wavelengths, a wavelength tunable laser Ti: Sapphire laser is used as the light source of the first excitation light having the wavelength λ ₁ on the short wavelength side, and the second light having the wavelength λ ₂ on the long wavelength side is used. 1.064μ wavelength as excitation light source
There is an infrared light generator using an Nd: YAG laser that oscillates at m.

Here, in the principle of difference frequency generation, difference frequency light is generated by wavelength conversion of light on the short wavelength side in a nonlinear optical crystal.

That is, in the above-mentioned conventional infrared light generating device, the difference frequency light (infrared light) is a wavelength tunable laser that generates the first pumping light having the wavelength λ ₁ on the short wavelength side, Ti: Sa.
The light generated by the pphire laser is generated by wavelength conversion in the nonlinear optical crystal.

Therefore, in this infrared light generator, the output of the difference frequency light (infrared light) is determined by Ti: Sapph.
This is the output of the ire laser, and the output of the difference frequency light (infrared light) depends on the output of the Ti: Sapphire laser.

Since the Ti: Sapphire laser needs to be pumped by the second harmonic of a Nd: YAG laser having a wavelength of 0.532 μm, in order to improve the output of the difference frequency light (infrared light), There is a problem that the size of the entire apparatus cannot be avoided.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to provide a high-output, compact, wavelength-tunable red light. It is intended to provide an external light generation device.

[0010]

In order to achieve the above object, an infrared light generating device according to the present invention, as shown in the conceptual configuration diagram of FIG. An external light generating device, which uses an Nd: YAG laser 12 as a light source of excitation light (excitation light 1) of a first wavelength on the short wavelength side incident on the nonlinear optical crystal 10 and emits the light incident on the nonlinear optical crystal 10 A Cr: forsterite laser 14 is used as a light source of the excitation light of the second wavelength on the wavelength side (excitation light 2).

More specifically, an Nd: YAG laser 12 oscillating at a wavelength of 1.064 μm,
The fundamental wave of the Nd: YAG laser 12 is used as the excitation light (the excitation light 1) of the first wavelength on the short wavelength side by using a Cr: forsterite laser which is a wavelength variable solid-state laser that oscillates at 1.35 μm. As a result, high output and compactness, wavelength of 5 to 14 μm
The infrared light generation device capable of tuning the wavelength in the infrared region can be realized.

As the Cr: forsterite laser, an Nd: YAG laser 16 can be used as an excitation laser.

When the infrared light generating device according to the present invention is operated by a pulse operation, the excitation light of the first wavelength (excitation light 1) and the excitation light of the second wavelength (excitation light 2) are mixed. Since the synchronization of the two pulsed laser beams is important, the time jitter of the pulsed laser beam generated by the Cr: forsterite laser, which is a tunable solid-state laser, is used to synchronize the two pulsed laser beams. time
Jitter) is important.

For this reason, in the infrared light generating apparatus according to the present invention, Cr: forste is produced by using both-side excitation.
By exciting a write laser or oscillating a Cr: forsterite laser by forming a cavity having a short optical path length, a tunable solid-state laser C is obtained.
The time jitter of the pulse laser light generated by the r: forsterite laser is suppressed so that the two pulse laser lights are synchronized.

That is, the invention according to claim 1 of the present invention is an infrared light that emits infrared light by generating a difference frequency by mixing and mixing two types of excitation light having different wavelengths into a nonlinear optical crystal. In the generator, an Nd: YAG laser is used as a light source of the excitation light of the first wavelength on the short wavelength side incident on the nonlinear optical crystal, and the excitation light of the second wavelength on the long wavelength side incident on the nonlinear optical crystal is used. Cr: forste as a light source for
A write laser is used.

According to a second aspect of the present invention, in the first aspect of the present invention, the Nd: YAG laser has a wavelength of 1.0 nm as the first wavelength of pumping light. A 064 μm pulsed laser beam is generated and incident on the nonlinear optical crystal, and the Cr: forsteri
The te laser is a wavelength tunable laser that oscillates in a wavelength range of 1.15 to 1.35 μm, suppresses the time jitter of the pulsed laser light by both-side excitation, and generates 1 as the excitation light of the second wavelength. .15 to 1.35 μm in a wavelength range of selectively generated and incident on the non-linear optical crystal, and according to the wavelength of the pulsed laser light generated by the Cr: forsterite laser, 5-14μm due to difference frequency generation
Infrared light in the wavelength range described above is selectively generated.

According to a third aspect of the present invention, in the first aspect of the present invention, the Nd: YAG laser has a wavelength of 1.10 as the first wavelength of pumping light. A 064 μm pulsed laser beam is generated and incident on the nonlinear optical crystal, and the Cr: forsteri is generated.
The te laser uses a cavity with a short optical path length to achieve 1.1.
A wavelength tunable laser that oscillates in a wavelength range of 5 to 1.35 μm, using a cavity having a short optical path length to suppress time jitter of pulsed laser light, and to generate 1 μm as pump light of the second wavelength. .15 to 1.35
A laser beam having a wavelength range of μm is selectively generated and incident on the nonlinear optical crystal, and the Cr: forsterite is formed.
Depending on the wavelength of the pulsed laser light generated by the laser, a difference frequency of 5 to 1
The infrared light having a wavelength range of 4 μm is selectively generated.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an infrared light generator according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a diagram illustrating the configuration of an infrared light generator as an example of an embodiment of the present invention.

The infrared light generator shown in FIG. 2 is operated by a pulse operation, and Nd which oscillates at a wavelength of 1.064 μm, which is a light source of a short-wavelength side pulsed laser light, is:
A YAG laser 100 and a tunable solid-state laser Cr: forster that oscillates in a wavelength range of 1.15 to 1.35 μm, which is a light source of pulsed laser light on the long wavelength side.
An Nd: YAG laser 104 serving as a light source for exciting the item laser 102, the Cr: forsterite laser 102, and a trigger for operating the Nd: YAG laser 100 in a pulse operation are output to the Nd: YAG laser 100, and the Cr is output. : Trigger to operate the Nd: YAG laser 104 in pulse operation to operate the forsterite laser 102 in pulse operation
d: Pulse generator 10 for outputting to YAG laser 104
6, Nd: YAG laser 100 and Cr: forste
and a non-linear optical crystal 108 which mixes and emits pulsed laser light generated by the write laser 102 and generates infrared light by generating a difference frequency.

The nonlinear optical crystal 108 is, for example, an AgGaS ₂ crystal which is a chalcopyrite crystal,
HgGa ₂ S ₄ crystal, GaSe crystal, or the like can be used.

As described above, Cr: forsteri
The excitation light source of the te laser 102 has a wavelength of 1.064.
Although the Nd: YAG laser 104 oscillating at μm is used, the Nd: YAG laser 104
Wavelength 1.06, which is the fundamental wave emitted from laser 104
The 4 μm excitation light is adjusted to a predetermined beam diameter by a telescope composed of lenses 110 and 112,
The beam is split in two directions by a beam splitter 114.

One of the excitation lights A of the excitation lights branched in two directions by the beam splitter 114 passes through one of the folding prisms 116 and 118 to one side of a wavelength tunable laser crystal Cr: forsterite laser crystal 120. The left-side excitation light B is introduced into the left side in FIG. 2, while the other excitation light B among the excitation lights branched in two directions by the beam splitter 114 passes through the reflecting mirror 122 and the folding prisms 124 and 126 to form Cr: forsteri.
Introduced to the other side (the right side in FIG. 2) of the te laser crystal 120, the Cr: forsterite laser crystal 120 is excited on both sides.

Thus, Cr: forsterite
The gain of the laser 102 is increased, and the Cr: forster
The time jitter of the pulse laser light generated by the item laser 102 can be suppressed.

Further, this Cr: forsterite
In the laser 102, Cr: forsterite
With the laser crystal 120 positioned in the middle, Cr:
On one side (left side in FIG. 2) of the forsterite laser crystal 120, an output mirror 128 (the output mirror 128 has a wavelength of 1.15 to 1.
The mirror is configured to transmit 35 μm light at a predetermined transmittance (for example, 30%). ) Is arranged and Cr: f
The other side of the orsterite laser crystal 120 (FIG. 2)
On the right side of the figure, a dispersion prism 130 for wavelength selection functioning as a wavelength selector and a rotating mirror 132 are arranged, and a cavity is formed by the output mirror 128 and the rotating mirror 132. In other words, the output mirror 128 is one of the mirrors forming the cavity, and the rotating mirror 132
Is the other mirror constituting the cavity.

As shown in FIG. 3, the output mirror 128 is formed in a substantially D-shape by cutting a part of a disk-shaped output mirror. Therefore, if it is a conventional disk-shaped output mirror, the Cr: forsterite laser crystal 1
20 so as not to hinder the introduction of the excitation light A into
Although it was necessary to arrange the Cr: forsterite laser crystal 120 at a position C distant from the laser crystal 120, according to the substantially D-shaped output mirror 128, since the excitation light A can pass through the cut region, : Forsterit
Since it can be arranged at the position D near the e-laser crystal 120, the optical path length of the cavity can be shortened,
Time jitter can be suppressed.

The dispersing prism 130 also has a smaller Cr: forsteet than the position E which is generally arranged conventionally.
Since it is arranged at the position F in the vicinity of the write laser crystal 120, the optical path length of the cavity can be shortened and the time jitter can be further suppressed.

In the above configuration, in order to generate infrared light with a difference frequency by the infrared light generating device, first excitation light on the short wavelength side (hereinafter referred to as "excitation light 1").
, And a Cr: forsterite laser 102 that generates second excitation light (hereinafter, referred to as “excitation light 2”) on the long wavelength side. Pulse operation is performed using each of the external triggers. The synchronization between the pump light 1 and the pump light 2 which are pulsed laser lights is performed by adjusting the timing of the two external triggers.

In the infrared light generating apparatus having the above-described configuration, the wavelength λ _{1 of} the excitation light ₁ and the wavelength λ ₂ of the excitation light 2 are
There is a relationship of “λ ₁ <λ ₂ ”. As described above, the principle of the difference frequency generation is that the excitation light 1 having a short wavelength is converted into the difference frequency light, and the output is determined by the output of the excitation light 1.

In this infrared light generating apparatus, the excitation light 1 is 1.
Since the Nd: YAG laser oscillates at 064 μm, the conventional Ti: Sapphire laser and Nd: Y
Compared with the combination with the AG laser, higher output and smaller size can be achieved at the same time.

That is, in this infrared light generating device, N
d: Since the fundamental wave of the YAG laser is the pumping light 1, an infrared light generating device which is high-power and compact, can be tuned in a wide wavelength range of 5 to 14 μm, and has a wide wavelength variable region can be realized.

FIG. 4 is a graph showing the relationship between the wavelength of the Cr: forsterite laser 102 and the time jitter based on the experimental results of the present applicant. By using both-side pumping for the Cr: forsterite laser crystal 120, 1200 to 12
In the 50 ns wavelength range, the time jitter is up to 5
ns.

FIG. 5 shows a laser pulse of the Nd: YAG laser 100, and FIG. 6 shows a Cr: forsteri.
4 shows a laser pulse of the te laser 102. These two laser pulses could be synchronized even when 100 shots each occurred as shown in FIG.

The above-described embodiment may be modified as shown in the following (1) to (3).

(1) In the above embodiment, the dispersing prism 130 and the rotating mirror 132 are used as the wavelength selector. However, in order to further narrow the spectrum width, the distance between the dispersing prism 130 and the rotating mirror 132 is reduced. The etalon 140 may be inserted into the device (see FIG. 2).

(2) In the above embodiment, the dispersion prism 130 and the rotating mirror 132 are used as the wavelength selector. However, the present invention is not limited to this. Instead of 132, for example, a diffraction grating may be used.

(3) The above-described embodiments and the modifications shown in (1) and (2) above may be appropriately combined.

[0038]

Since the present invention is configured as described above, it has an excellent effect of providing a compact, high-output infrared light generator capable of wavelength tuning.

[Brief description of the drawings]

FIG. 1 is a conceptual configuration diagram of an infrared light generation device according to the present invention.

FIG. 2 is a configuration explanatory diagram of an infrared light generation device as an example of an embodiment of the present invention.

FIG. 3 is a perspective view of a substantially D-shaped output mirror in which a part of a disk-shaped output mirror is cut.

FIG. 4 shows Cr: forst based on the experimental results of the present applicant.
5 is a graph showing the relationship between the wavelength of an erite laser and time jitter.

FIG. 5 is a waveform showing a laser pulse of an Nd: YAG laser.

FIG. 6: Laser of Cr: forsterite laser
It is a waveform showing a pulse.

FIG. 7 shows a laser pulse of Nd: YAG laser and Cr:
It is a waveform which shows the state of synchronization at the time of generating a laser pulse of a forsterite laser and 100 shots, respectively.

[Explanation of symbols]

 Reference Signs List 10 Nonlinear optical crystal 12 Nd: YAG laser 14 Cr: forsterite laser 16 Nd: YAG laser 100 Nd: YAG laser 102 Cr: forsterite laser 104 Nd: YAG laser 106 Pulse generator 108 Nonlinear optical crystal 114 Beam splitter 120 Cr: forsterite Laser crystal 128 Output mirror 130 Dispersion prism 132 Rotating mirror 140 Etalon

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tomoyuki Wada 2-1 Hirosawa, Wako-shi, Saitama Pref. RIKEN (72) Inventor Hideo Tashiro 2-1 Hirosawa, Wako-shi, Saitama Pref. Reference) 2K002 AB12 BA02 BA04 CA02 5F072 JJ20 KK01 KK12 QQ02 RR01 SS06

Claims (3)

[Claims] 1. An infrared light generating apparatus for generating two types of excitation light having different wavelengths which are incident on a nonlinear optical crystal and mix them to generate infrared light by generating a difference frequency. An Nd: YAG laser is used as a light source of the excitation light of the first wavelength, and a Cr: forsterite laser is used as a light source of the excitation light of the second wavelength on the longer wavelength side incident on the nonlinear optical crystal. Generator. 2. The infrared light generating device according to claim 1, wherein the Nd: YAG laser generates a pulsed laser beam having a wavelength of 1.064 μm as the pumping light having the first wavelength and generates the nonlinear laser. Incident on the crystal, and the Cr: forsterite laser
A wavelength tunable laser that oscillates in a wavelength range of 1.35 μm, suppresses the time jitter of the pulsed laser light by both-side pumping, and uses a wavelength of 1.15 to 1.35 μm as the pumping light of the second wavelength. A laser beam in a range is selectively generated and incident on the nonlinear optical crystal, and a difference frequency of 5 to 14 μm is generated by the nonlinear optical crystal according to the wavelength of the pulsed laser beam generated by the Cr: forsterite laser. An infrared light generating device that selectively generates infrared light in the wavelength range described above. 3. The infrared light generating device according to claim 1, wherein the Nd: YAG laser generates a pulsed laser beam having a wavelength of 1.064 μm as the pumping light having the first wavelength and generates the nonlinear optical beam. The Cr: forsterite laser, which is incident on a crystal, is a wavelength tunable laser that oscillates in a wavelength range of 1.15 to 1.35 μm using a cavity with a short optical path length. Suppressing the time jitter of the pulsed laser light, selectively generating laser light having a wavelength range of 1.15 to 1.35 μm as the excitation light of the second wavelength, and making the laser light incident on the nonlinear optical crystal; According to the wavelength of the pulsed laser light generated by the Cr: forsterite laser, a wave of 5 to 14 μm is generated by the difference frequency generation in the nonlinear optical crystal. Range selectively infrared light generating device for generating infrared light.