JPH1174589A - Semiconductor laser pumped solid laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the utilization efficiency of pumping energy for semiconductor laser pumped solid laser by an arrangement wherein a semiconductor laser pumps a solid laser with a wavelength making an optical transition from one specific level to another specific level of the solid laser. SOLUTION: At the time of laser transition from<4> F3/2 level (laser upper level) to<4> I11/2 level (laser lower lower level) of Nd<3+> , the oscillation wavelength of a semiconductor laser for pumping a solid laser corresponds optical transition from<4> I9/2 level (ground level) of Nd<3+> of the solid laser to the laser upper level. The Nd3+ is pumped from the ground level to the laser upper level with a light having such a wavelength and the Nd<3+> of laser upper level makes a transition to the laser lower level through laser transition without passing through a relax process of nonradiative transition. A laser light Y is obtained in that process and the laser lower level is relaxed to the ground level through nonradiative transition. The utilization efficiency of pumping energy on the order of 82-83% is attained and it is higher than ordinary utilization efficiency of 76%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser pumped solid-state laser using a semiconductor laser as a pump light source.

[0002]

2. Description of the ^Related Art As a practical solid-state laser, a laser using Nd ³⁺ as active ions is mainly used, and a YAG laser and a glass laser are known as typical ones. A lamp has been used as a light source for exciting such a solid-state laser, but a light source using a semiconductor laser (LD) has recently been developed to achieve high efficiency and compactness.

FIG. 2 is an energy level diagram of Nd ³⁺ (in a solid crystal field) showing the excitation / emission process of a conventional semiconductor laser-excited solid-state laser using Nd ³⁺ as active ions and a semiconductor laser as an excitation light source. is there.

Conventionally, the oscillation wavelength of the semiconductor laser for exciting the solid-state lasers, ⁴ I _9/2 level position of ^{Nd 3+} in the solid-state laser ⁴ F _5/2 level position from (ground level) and ² H _9/2 level For example, a wavelength around 808 nm is used for a YAG laser, and a wavelength around 803 nm is used for a glass laser. For light of this wavelength, Nd
³⁺ is once excited from the ground level to a level higher in energy than ⁴ F _3/2 (laser upper level) (illustration a), and shifts to the laser upper level in a relaxation process due to non-radiative transition ( Illustration b).

[0005] ^{Nd 3+} laser upper level transitions in the laser transition ⁴ I _11/2 level position (laser low level) (shown c), the laser beam Y is obtained in this process, then ⁴ I
It is relaxed from _11/2 (laser lower level) to the ground level by non-radiative transition (illustrated d).

[0006] It should be noted that FIG. ^{2, 4} from 4 _{F 3/2} level I
_{Although the} case where the laser transition of the _11/2 level is performed is shown, the laser transition from the ⁴ F _3/2 level to the ⁴ I _13/2 level, and the laser transition from the ⁴ F _3/2 level to ⁴ I _9/2. The same pumping process is performed for a laser that makes a level transition.

[0007]

[Problems that the Invention is to Solve In this way ⁴ F _5/2
In the method of exciting levels and ² H _9/2 levels, laser photons ⁽⁴ F which can be extracted from one excitation photon
_(3/2 level to ⁴ I _11/2 level) is at most one. The energy of the excitation photon is about 1.6 eV, while the energy of the laser photon is: (1) about 1.4 eV in the case of a laser transition between the upper laser level and the ⁴ I _9/2 level; The laser transition between the upper level and the ⁴ I _11/2 level is about 1.2 eV. (3) The laser transition between the upper level and the ⁴ I _13/2 level is about 0.9 eV.

Accordingly, the utilization efficiency of the excitation energy (laser photon energy / excitation energy), (1) about 88% when the laser high level laser transitions between ⁴ I _9/2 level (2) on the laser Approximately 75% in the case of a laser transition between the level and the ⁴ I _11/2 level (3) Approximately 56% in the case of a laser transition between the upper level of the laser and the ⁴ I _13/2 level, and in principle more However, there is a problem that the excitation energy utilization efficiency cannot be obtained.

Further, all of the Nd ³⁺ excited to the ⁴ F _5/2 level and the ² H _9/2 level does not always move to the upper level of the laser due to the relaxation process (b in FIG. 2). In general, the transition probability (quantum efficiency) from the level excited by the optical transition by the excitation light to the upper level of the laser is less than 100%.

The present invention has been made in view of such a problem, and has as its object to increase the efficiency of using the excitation energy of a semiconductor laser-excited solid-state laser using Nd ³⁺ as active ions.

[0011]

According to the present invention, there is provided a semiconductor laser pumped solid state laser comprising a solid state laser having Nd ³⁺ as active ions and a semiconductor laser for exciting the solid state laser. characterized in that from ⁴ I _9/2 level of ^{Nd 3+} in the solid-state laser to ⁴ F _3/2 level at the wavelength for optical transition formed by exciting the solid-state laser.

According to the present invention, Nd ³⁺
Is directly excited from the ground level to the upper laser level by an optical transition without a relaxation process accompanied by a non-radiative transition, so that the quantum efficiency is 100% and necessary to form one upper laser level. The energy of the excitation photons is also small, and the utilization efficiency of the excitation energy can be improved.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an energy level diagram of Nd ³⁺ (in a solid crystal field) showing an excitation / emission process of a semiconductor laser-excited solid-state laser using Nd ³⁺ as active ions and a semiconductor laser as an excitation light source according to an embodiment of the present invention. It is.

In this embodiment, Nd ^{3+ 4} F _3/2
In case of the laser transition level (laser high level) from ^{4 I} _11/2 level position (laser low level), the oscillation wavelength of the semiconductor laser for exciting the solid-state laser, a solid-state laser of Nd ^3+
The wavelength corresponds to the optical transition from the ⁴ I _9/2 level (ground level) to the laser upper level.

In the light of this wavelength, Nd ³⁺ is excited from the ground level to the upper level of the laser (illustration A), and Nd ^{3+ of the} upper level of the laser does not undergo a relaxation process due to non-radiative transition.
Changes to a laser lower level by laser transition (illustration C),
In this process, a laser beam Y is obtained, which is then relaxed from the lower laser level to the ground level by a non-radiative transition (D in the drawing). Although it is shown for those in the case of the laser low level to ⁴ I _11/2 level in this figure, ⁴ I
_13/2 level ^position, the same excitation process also the 4 _{I 9/2} level which the laser low level.

In the case of a YAG laser, the wavelength is 870 nm rather than the absorption band around 808 nm conventionally used.
There is an absorption band showing relatively strong absorption in the vicinity and near the wavelength of 885 nm, and this absorption band corresponds to the optical transition from the ground level of Nd ³⁺ to the laser upper level. Therefore, it is only necessary to excite with a semiconductor laser that can oscillate at a wavelength of about 870 nm or about 885 nm. As a semiconductor laser that oscillates a laser having such a wavelength, GaAlA is used.
There is an s type or an InGaAs type.

In this embodiment, the lower level of the laser is ⁴ I
_In the case of _11/2 level, since the laser transition wavelength of the YAG laser is 1064 nm, the utilization efficiency of the excitation energy is about 82 to 83%, which can be higher than the conventional utilization efficiency of the excitation energy of 76%.

In the case of a glass laser, the wavelength 875 is larger than the absorption band around 803 nm conventionally used.
There is a broad absorption band having a peak near nm, and this absorption band corresponds to the optical transition from the ground level of Nd ³⁺ to the laser upper level. Therefore, the wavelength 8
What is necessary is just to pump with the semiconductor laser which can oscillate around 75 nm. As the semiconductor laser in this case, there is a GaAlAs system or an InGaAs system.

In this embodiment, the lower level of the laser is ⁴ I
_In the case of _11/2 level, since the laser transition wavelength of the glass laser is 1053 nm, the pump energy use efficiency is about 83%, which can be higher than the conventional pump energy use efficiency of 76%.

In the above embodiment, ^four lasers
While advantage of the laser transition between I _11/2 level use, between ⁴ I _9/2 level from the upper laser level, the laser transitions between ⁴ I _13/2 level from the laser upper level You may. Utilization efficiency of excitation energy in this case, in the from the upper laser level to laser transitions between the ⁴ I _9/2 level of about 1
For the laser transition between the upper laser level and the ⁴ I _13/2 level, about 75% is possible.

Although the above description has been made by taking a YAG laser and a glass laser as examples, the present invention can be applied to all semiconductor laser-excited solid-state lasers using Nd ³⁺ as active ions.

[0022]

As it is evident from the foregoing description, a semiconductor laser oscillating wavelength to optical transition from ⁴ I _9/2 level to ⁴ F _3/2 level of Nd ³⁺ in the solid-state laser according to the present invention as an excitation light source Since the solid-state laser is excited, the utilization efficiency of the excitation energy is improved, the quantum efficiency is also made 100%, and the efficiency of the entire semiconductor laser-excited solid-state laser using Nd ³⁺ as active ions can be improved. This improvement in efficiency leads to a reduction in the heat load on the solid-state laser medium, and the demand for cooling the solid-state laser pumped solid-state laser is also eased.

[Brief description of the drawings]

FIG. 1 shows an energy level of Nd ³⁺ (in a solid crystal field) showing an excitation / emission process of a semiconductor laser-excited solid-state laser using Nd ³⁺ as active ions and a semiconductor laser as an excitation light source according to an embodiment of the present invention. FIG.

FIG. 2 is an energy level diagram of Nd ³⁺ (in a solid crystal field) showing an excitation / emission process of a conventional semiconductor laser-excited solid-state laser using Nd ³⁺ as active ions and a semiconductor laser as an excitation light source.

[Explanation of symbols]

 A Optical transition C Laser transition D Non-radiative transition Y Laser light

Claims (1)

[Claims] 1. A solid-state laser pumped solid-state laser comprising: a solid-state laser having Nd ³⁺ as active ions; and a semiconductor laser for exciting the solid-state laser, wherein Nd ^{3+ 4} I of the solid-state laser oscillated by the semiconductor laser is provided. _9/2
The semiconductor-laser-pumped solid-state laser, characterized in that formed by exciting the solid-state laser with a wavelength to optical transition from level to ⁴ F _3/2 level.