JPH0575189A - Laser diode pumping solid laser - Google Patents

Abstract

PURPOSE:To obtain a high efficiency of wavelength conversion in a title laser which pumps a solid laser medium having the function of light wavelength conversion by a semiconductor laser. CONSTITUTION:A semiconductor laser resonator is constituted of the rear end face 11a of a laser diode chip 1 and the mirror face 12a of the resonator mirror 12, and a NYAB crystal 13 that is the solid laser medium is arranged in this resonator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser diode pumping solid-state laser in which a solid-state laser medium is pumped by a semiconductor laser (laser diode), and more specifically, the solid-state laser medium itself has an optical wavelength converting function, and The present invention relates to a laser diode pumped solid-state laser that converts the wavelength of a laser oscillation beam into its second harmonic or the like.

[0002]

2. Description of the Related Art For example, SPIE Vol.1104 p100 March 1
As described in 989, Nd: COANP, Nd: P is used as a solid-state laser medium in which a rare earth element such as Nd (neodymium) is doped and has an optical wavelength conversion function.
NP and the like are known. As such a solid-state laser medium, as described in p132 of the same magazine, N
d: LiNbO ₃ , NYAB (Nd _X Y _1-X Al ₃ (B
O ₃ ) ₄ x = 0.04 to 0.08) and the like are also known, and these are called Self-Frequency-Doubling Crystal.

Laser diode pumping solid-state lasers using these are described in SPIE Vol.1104 p132.
As shown in March 1989 and Laser Research Vol. 17 No. 12 p48 (1989), it is known to use a NYAB crystal to obtain the second harmonic of the oscillation laser beam by laser diode pumping. See also J. Opt. Soc. A
m Vol.3 p140 (1986), Nd: MgO: Li NbO ₃
Is excited by a dye laser having a wavelength of 0.60 μ, and the second harmonic of the oscillation laser beam is obtained.

In any conventional laser diode pumping solid-state laser using this Self-Frequency-Doubling Crystal as a solid-state laser medium, basically, a laser beam as a pumping emitted from a semiconductor laser is one-way through the solid-state laser medium. It was configured to only pass through.

[0005]

However, in the conventional solid-state laser having such a wavelength conversion function,
There is a problem that the wavelength conversion efficiency is low. So, for example, Optics Letters Vo
l. 16, No. 6 / March 15, 1991 p. As shown in 396, it has been proposed to provide an external resonator that resonates pumping light separately from the resonator that a semiconductor laser originally has, and to arrange a solid-state laser medium in this external resonator. ..

Such a structure is effective in improving the wavelength conversion efficiency, but on the other hand, the size of the device is increased due to the provision of the external resonator, and the reliability is lowered due to the increase in the number of parts. It has a problem that it is easy to invite.

On the other hand, in order to improve the wavelength conversion efficiency while avoiding an increase in size of the device, a solid laser medium through which pumping light passes in only one direction is heavily doped with Nd and has a large absorption coefficient for pumping light. It is also considered to use. However, in such a case, since the solid-state laser medium that can be used is limited, the cost is likely to increase.

The present invention has been made in view of the above circumstances and has a small number of parts and can be formed in a small size.
It is an object of the present invention to provide a laser diode pumped solid-state laser that can efficiently obtain a wavelength-converted wave even if a general solid-state laser medium not particularly doped with Nd is used.

[0009]

A laser diode pumping solid-state laser according to the present invention is a laser diode for pumping a solid-state laser medium doped with a rare earth element such as neodymium and having an optical wavelength conversion function by a semiconductor laser as described above. In a pumping solid-state laser, a resonator of a semiconductor laser is configured with one end face of a laser diode chip and an end face of an element separate from the laser diode chip as mirror surfaces, and the solid-state laser medium is the semiconductor laser. It is characterized in that it is arranged inside the resonator.

In the present invention, as the solid-state laser medium, a usual material called Self-Frequency-Doubling Crystal, that is, the above-mentioned NYAB, NAB, Nd:
MgO: LiNbO ₃ , Nd: PNP or the like can be used. In addition, KTP and β-B which are inorganic materials
It is also possible to use a nonlinear optical material for wavelength conversion in which BO, LiB ₂ O ₃ , KNbO ₃ , or chalcopyrite semiconductor is doped with a rare earth element such as Nd. In particular, since KTP has a large non-linear optical constant and a wide temperature allowable range and a wide angle allowable range, high wavelength conversion efficiency can be realized.

Further, as represented by Nd: PNP,
NPP (N- (4-nitrophenyl) -L-prolinol), NPAN (N- (4-nitrophenyl) N-methylaminoacetonitrile), PRA (3, disclosed in JP-A-62-210432). An organic nonlinear optical material such as 5-dimethyl-1- (4-nitrophenyl) pyrazole) doped with a rare earth element can also be used. Especially PR
A has a nonlinear optical constant larger than that of KTP described above and has a wide temperature allowable range, so that high wavelength conversion efficiency can be realized.

[0012]

If the solid-state laser medium is arranged in the resonator of the semiconductor laser, the pumping light that resonates in the resonator and is in a sufficiently high power state is incident on the solid-state laser medium. However, even if a solid laser medium that is not particularly heavily doped is used, a high-intensity solid-state laser oscillation beam, that is, a fundamental wave is obtained, and high wavelength conversion efficiency is realized.

Since the above-mentioned resonator is not a complete external resonator and one mirror surface is constructed by utilizing the end surface of the laser diode chip, this laser diode pumping solid-state laser has the above-mentioned external resonator. The number of parts can be reduced as compared with the case of using, and it can be formed in a small size and have high reliability.

Further, since a high-intensity solid-state laser oscillation beam is obtained as described above, even when a solid-state laser medium such as NYAB having a relatively low crystal quality is used, a chip of this medium can be used. in that case,
Practical application becomes easy and cost reduction is realized.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in the drawings. FIG. 1 shows a laser diode pumped solid state laser according to a first embodiment of the present invention. This laser diode pumping solid-state laser is a resonator in which a laser diode chip 11 that emits a laser beam 10 as pumping light and a concave end surface 12a having a radius of curvature of 2 mm are arranged to face the laser diode chip 11. It has a mirror 12 and a NYAB crystal 13 arranged between the resonator mirror 12 and the laser diode chip 11. The components described above are mounted and integrated in a common housing (not shown).

The NYAB crystal 13 is formed by the Self-Fre
It is one of the quency-Doubling crystals, and is formed to a thickness of 1 mm in this embodiment. And NYAB crystal 13
In order to collect the laser beam 10 which is divergent light,
The end surface 13a on the laser diode chip 11 side is formed into a convex surface, and the end surface 13a is arranged so as to directly contact the laser diode chip 11.

As the laser diode chip 11, one that emits a laser beam 10 having a wavelength λ ₁ = 804 nm is used. This laser beam 10 is focused and N
It is incident on the YAB crystal 13. The NYAB crystal 13 is pumped by this laser beam 10 and has a wavelength λ ₂ = 1062.
together emit nm laser beam 15 wavelength-converts the laser beam 15 with the wavelength _{λ 3 = λ 2/2 =} 531 second harmonic 16 nm. Here, the coating 17 is formed on the rear end surface 11a of the laser diode chip 11 and also on the NYA.
Coating 1 is applied to the end faces 13a and 13b of the B crystal 13 respectively.
Coatings 8 and 19 and the end face 12a of the resonator mirror 12 are provided with a coating 20. These coatings 17, 1
Wavelengths λ ₁ = 804 nm, λ ₂ = 1062n for 8, 19 and 20
The characteristics for m and λ ₃ = 531 nm are as follows. AR indicates no reflection (transmittance 99% or more), and HR indicates high reflection (reflectance 99.9% or more). λ ₁ = 804 nm λ ₂ = 1062 nm λ ₃ = 531 nm Coating 17 HR − − Coating 18 85% Reflective HR HR Coating 19 AR HR 95% Reflective Coating 20 HR − AR Coating 17, 18, 19 and 20 as described above The laser beam 10, which is the pumping light, resonates between the end faces 11a and 12a to cause laser oscillation. That is, the resonator for the semiconductor laser is configured with these end faces 11a and 12a as mirror surfaces. The second harmonic wave 16 resonates between the end faces 13a and 13b, and then satisfactorily passes through the mirror surface 12a of the resonator mirror 12.

As described above, since the laser beam 10 which is resonated inside the resonator and is in a sufficiently high power state is incident on the NYAB crystal 13, the NYAB crystal 13 is particularly heavily doped with Nd. Even if it is not a thing and is formed as thin as 1 mm in thickness, it can be sufficiently absorbed therein. Therefore, the high-intensity fundamental wave, namely the laser beam 15
And thus high wavelength conversion efficiency is realized. In this embodiment, when the semiconductor laser output is 200 mW,
A second harmonic 16 of 1 mW is obtained.

Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 2, the same elements as those in FIG. 1 are denoted by the same reference numerals, and the duplicated description thereof will be omitted.

In this second embodiment, a NYAB crystal is used.
One end surface 13a of 13 is formed flat, and the laser diode chip 11 is directly bonded to this end surface 13a. Also N
The other end surface 13b of the YAB crystal 13 is a surface having a curvature for focusing the laser beam 10. Note that NYAB
The maximum thickness of the crystal 13 is 0.3 mm, and the radius of curvature of its end face 13b is 2 mm. The laser diode chip 11 and the NYAB crystal 13 are fixed on a common copper block 30, and the Peltier element 31 controls the temperature to a predetermined temperature.

Also in the second embodiment, as the laser diode chip 11, one which emits the laser beam 10 having the wavelength λ ₁ = 804 nm is used. The coating 17 applied to the rear end surface 11a and NYA
The coating 18 applied to the end face 13a of the B crystal 13 is the first
It is similar to that in the embodiment. On the other hand, NYAB crystal 13
On the end face 13b of the laser beam 10 which is pumping light.
A coating 32 that reflects light is applied. The wavelength of these coatings 17, 18 and 32 λ ₁ = 804 nm, λ
_The characteristics for ₂ = 1062 nm and λ ₃ = 531 nm are summarized below. λ ₁ = 804 nm λ ₂ = 1062 nm λ ₃ = 531 nm Coating 17 HR − − Coating 18 85% reflection HR HR coating 32 HR HR 95% reflection Due to the coatings 17, 18 and 32 as described above, , The laser beam 10 which is the pumping light is the end face
Resonance occurs between 11a and 13b to cause laser oscillation. That is, in this embodiment, the resonator for the semiconductor laser is
These end faces 11a and 13b are configured as mirrors.

In this case as well, since the laser beam 10 which is resonated inside the resonator and is in a sufficiently high power state is incident on the NYAB crystal 13, this NYAB crystal 13 is particularly heavily doped with Nd. Even without, the thickness is 0.3 m
Even if it is formed as thin as m, it can be sufficiently absorbed there.
Therefore, a high-intensity fundamental wave, that is, the laser beam 15 is obtained, and high wavelength conversion efficiency is realized. Also in this embodiment, when the semiconductor laser output is 200 mW, 1 m
A second harmonic 16 of W is obtained.

Further, in the second embodiment, since the resonator of the semiconductor laser is constituted by the rear end face 11a of the laser diode chip 11 and the NYAB crystal end face 13b, the resonator mirror as in the first embodiment. There is no need to set twelve. The laser diode pumped solid state laser of this second embodiment is therefore particularly compact,
Moreover, the number of parts can be small. However, the laser diode pumped solid state laser of the first embodiment also
Compared to the case where an external resonator for pumping light emitted from a semiconductor laser is provided separately, the size may be smaller and the number of parts may be smaller.

Although the embodiment constructed so as to convert the solid-state laser oscillation beam into the second harmonic has been described above, the laser diode pumped solid-state laser of the present invention can be used in other embodiments, such as pumping light and solid-state laser oscillation beam. It is, of course, possible to configure so that the wavelength is converted to the sum frequency. In the case of sum frequency generation, the wavelength conversion efficiency tends to be particularly low when the intensity of the pumping light is low, and thus the application of the present invention can be said to be particularly effective.

[Brief description of drawings]

FIG. 1 is a side view of a first embodiment device of the present invention.

FIG. 2 is a side view of a second embodiment device of the present invention.

[Explanation of symbols]

 10 laser beam (pumping light) 11 laser diode chip 11a rear end face of laser diode chip 12 resonator mirror 12a end face of resonator mirror 13 NYAB crystal 13a, 13b end face of NYAB crystal 15 laser beam (fundamental wave) 16 second harmonic 17, 18, 19, 20, 32 coating

Claims (1)

[Claims] 1. A solid laser medium doped with a rare earth element such as neodymium and having a light wavelength conversion function,
In a laser diode pumped solid-state laser pumped by a semiconductor laser, a resonator of the semiconductor laser is configured with one end face of a laser diode chip and an end face of an element separate from the laser diode chip as mirror surfaces, A laser diode pumped solid-state laser, wherein a solid-state laser medium is disposed inside the resonator.