JP2007329272A - Semiconductor-laser exciting solid laser oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor-laser exciting solid laser oscillator capable of obtaining laser beams having a high peak and short pulses without using a Q switch element, and capable of making a production cost lower than conventional devices. <P>SOLUTION: The Q switch element is not fitted to the solid laser oscillator 1. A rise time at a time when a pulse current (an excitation current) is conducted through a semiconductor laser 4 as an excitation light source is set to 1 μs or less, while the pulse current is conducted through the semiconductor laser 4 for the time when pulse laser beams begins to oscillate in place of the Q switch element. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor laser-pumped solid-state laser oscillation device, and more particularly to a semiconductor laser-pumped solid-state laser oscillation device capable of obtaining a high peak short pulse laser beam without using a Q switch element.

2. Description of the Related Art Conventionally, a semiconductor laser-excited solid-state laser oscillation device that obtains a high peak short pulse laser beam by using a Q switch element is known (for example, Patent Document 1).
FIG. 3 shows an outline of a conventional apparatus disclosed in Patent Document 1 described above. Here, the solid-state laser oscillation device 1 is provided with a laser medium 2 in which one end face is in contact with the heat sink 3 and an excitation light PL that is disposed outside the laser medium 2 and directed toward the laser medium 2. A plurality of semiconductor lasers 4, an output mirror 5 opposed to the laser medium 2, and a Q switch element disposed between the laser medium 2 and the output mirror 5 are provided.
In the semiconductor laser 4 used in the conventional apparatus, as shown in FIG. 4a, the rise time t1 when energizing the excitation current is about several tens of μs, and when excited by such a semiconductor laser, FIG. As shown, the rise time of the laser beam La was several tens of μs.
For this reason, in order to obtain a high peak short pulse laser, in the apparatus of Patent Document 1, a Q switch element such as an acousto-optic element or an electro-optic element is provided in the resonator.
Japanese Patent No. 2729621

By the way, in the apparatus of the above-mentioned Patent Document 1, the ASE light (amplified spontaneous emission light) emitted from the laser medium is transmitted through the Q switch element provided in the resonator, causing an output loss or the resonator length. However, there is a problem that the length of the oscillator becomes large as a whole, and a driving device for the Q switch element is required.
In addition, if the excitation time by the excitation light source is long, laser light having a low peak value is oscillated after the first laser light oscillation, and depending on the workpiece, excessive heat energy is applied to the irradiated portion of the laser light. And there is a possibility that the workpiece will be affected by heat.

In view of the circumstances described above, the present invention includes a laser medium having an active substance therein and a semiconductor laser that oscillates excitation light by energizing excitation current, and the semiconductor laser is supplied with a pulse current as excitation current. In a semiconductor laser excitation solid-state laser oscillation device that excites the laser medium with excitation light that is energized and oscillated from the semiconductor laser to oscillate pulse laser light,
The rise time when the pulse current is supplied to the semiconductor laser is set to 1 μs or less, and the pulse current is supplied to the semiconductor laser until the pulse laser beam starts to oscillate.

  According to the configuration described above, it is possible to obtain a laser beam having a high peak short pulse equivalent to a Q switch pulse laser beam that can be oscillated by the Q switch element without providing the Q switch element.

Hereinafter, the present invention will be described with reference to the illustrated embodiment. In FIG. 1, reference numeral 1 denotes a solid-state laser oscillation device that oscillates laser light La. In this embodiment, a disk-shaped laser medium 2 made of ceramics is used.
The solid-state laser oscillation device 1 includes a heat sink 3 made of copper as a cooling means, the laser medium 2 having a left end face bonded to a flat cooling surface 3a extending in the vertical direction of the heat sink 3, and the laser medium. The semiconductor laser 4 as an excitation light source disposed at a plurality of locations on the outer surface of the circumferential surface 2 and irradiating the excitation light PL toward the laser medium 2 is opposed to the laser medium 2 on the same axis. And an output mirror 5 that outputs the laser beam La toward the right side of the drawing.
The constituent members of the solid-state laser oscillation device 1 described above are arranged in a casing (not shown) so that the laser light La transmitted through the output mirror 5 as a front mirror is oscillated from the opening (not shown) to the outside of the casing. It has become.

The laser medium 2 has a doped circle 6 in a virtual circle with a predetermined radius surrounding the axis, and a region outside the doped portion 6 in the laser medium 2 is an undoped portion 7.
In this embodiment, the doped portion 6 of the laser medium 2 is configured by adding rare earth ions (for example, Yb) or transition metal ions as active substances to YAG as a base material.
The end face on the left side of the laser medium 2 is coated with a total reflection film 8 as a rear mirror. The total reflection film 8 is composed of a dielectric multilayer film and ASE light (amplified spontaneous emission) oscillated from an active substance. Light) and excitation light are totally reflected.
On the other hand, the end face on the output mirror 5 side of the laser medium 2 is coated with a partial reflection film 11 made of a dielectric multilayer film that reflects the excitation light PL and transmits the ASE light. The circumferential surface of the disk-shaped laser medium 2 serves as a light incident part 12 for allowing the excitation light PL to pass therethrough.
In this embodiment, a resonator is constituted by the output mirror 5 as a front mirror and the total reflection film 8 as a rear mirror with the dope portion 6 interposed therebetween.

Thus, unlike the conventional example, this example is configured so that a laser beam with a high peak short pulse can be obtained without providing a Q switch element in the solid-state laser oscillation device 1.
In other words, in the present embodiment, the Q switch elements (AO, EO) are not arranged in the solid-state laser oscillation device 1, and instead, the rise time of the pulse current (excitation current) energized to the semiconductor laser 4 is determined. Is set short.
More specifically, as shown in FIG. 2a, the rising time t1 of the pulse current flowing through the semiconductor laser 4 is set to 100 to 200 ns (10 ⁻⁹ s). As a result, in this embodiment, as shown in FIG. 2b, it is possible to obtain the output of the laser beam La having a high peak and short pulse that rises in 100 ns or less. The rise time of the pulse current may be 1 μs or less, more preferably 200 ns or less.
In the present embodiment, the concentration of the active substance Yb in the laser medium 2 is set to 10% or less, and the thickness (axial dimension) of the laser medium 2 is set to 0.5 mm or less.
Note that the higher the concentration of the doped portion 6 is, the higher the output laser beam La can be obtained. However, the amount of heat generation is large and the thermal lens action due to thermal strain occurs, and the quality of the laser beam La is deteriorated. Therefore, in the present embodiment, the thickness of the laser medium 2 is reduced to 0.5 mm or less, so that the laser medium 2 is easily cooled by the heat sink 3.

In the above configuration, the pulse current (excitation current) whose rise time is set to 100 to 200 ns as described above is energized until the laser light La starts to oscillate to the semiconductor laser 4.
As a result, the excitation light PL emitted from the semiconductor laser 4 and incident on the laser medium from the light incident part 12 passes through the undoped part 7 and is incident on the doped part 6, so that the ASE light is emitted from the doped part 6. The laser beam La is emitted and oscillated from the output mirror 5 as laser output light La after being resonated by the output mirror 5 as a front mirror and the total reflection film 8 as a rear mirror.
In this embodiment, the rise time of the pulse current applied to the semiconductor laser 4 is set to 1 μs or less, as shown in FIGS. 2a and 2b, although no Q switch element is provided. It is possible to obtain a laser beam La having a high peak and a short pulse quality.
In addition, according to the present embodiment, since the Q switch element is not provided, the solid-state laser oscillation device 1 can be made smaller than the conventional one, and the solid-state laser oscillation device 1 is manufactured as compared with the conventional one. Cost can be reduced.

The block diagram which shows one Example of this invention. The figure which shows the relationship between the excitation electric current and time in this invention shown in FIG. 1, and the relationship between a laser output and time. The block diagram which shows the conventional solid-state laser oscillation apparatus. FIG. 4 is a diagram showing a relationship between excitation current and time and a relationship between laser output and time in the conventional apparatus of FIG. 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Solid state laser oscillator 2 ... Laser medium 4 ... Semiconductor laser La ... Laser beam

Claims (2)

A laser medium having an active substance therein and a semiconductor laser that oscillates pumping light when energized with an excitation current are provided. The semiconductor laser is oscillated from the semiconductor laser by energizing a pulse current as an excitation current. In a semiconductor laser excitation solid-state laser oscillation device that excites the laser medium with excitation light to oscillate pulse laser light,
A semiconductor laser pumped solid-state laser, wherein a rise time when a pulse current is supplied to the semiconductor laser is set to 1 μs or less, and the pulse current is supplied to the semiconductor laser until the pulse laser beam starts to oscillate. Oscillator.   2. The semiconductor laser pumped solid-state laser oscillation device according to claim 1, wherein a rise time when a pulse current is supplied to the semiconductor laser is set to 100 to 200 ns.

Images