JPH11220194A - Semiconductor laser pumped solid-state laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide with a simple constitution a semiconductor laser pumped solid-state laser capable of achieving excitation efficiency which is equivalent to that of an end pump excitation system as a whole by a simple configuration. SOLUTION: A semiconductor laser beam L1 outputted from a semiconductor laser 1 which is used as a pumping light source is applied to an oscillation laser beam transmission surface 5a of a solid-state laser medium 5, without being transmitted through resonator mirrors 3 and 4 from a direction different from the laser optical axis for oscillation, and the solid-state laser medium 5 is excited, thus improving the efficiency of the resonator and at the same time, obtaining satisfactory excitation energy by allowing an oscillation laser mode to nearly match with an excitation laser mode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor laser pumped solid-state laser device.

[0002]

2. Description of the Related Art In a semiconductor laser-pumped solid-state laser device, a solid-state laser medium is disposed in a resonator composed of at least two resonator mirrors, and a laser beam output from a semiconductor laser is collected on the solid-state laser medium. This is a laser device of a system in which light is emitted, irradiated, and excited to cause laser oscillation in a resonator.

Further, as a laser pumping system using such a semiconductor laser as a pumping light source, at present, a solid-state laser device of a side pump pumping system and an end pump pumping system has been proposed.

[0004]

According to the solid-state laser device of the side-pump pumping method, the mode of the semiconductor laser beam for exciting the solid-state laser medium is generally much larger than the mode of the oscillating laser beam. Therefore, the threshold value of laser oscillation becomes high, and especially in a small laser having a limited excitation energy, the high efficiency which is a feature of the semiconductor laser-excited solid-state laser cannot be realized, and the transverse mode of the oscillation laser beam is liable to deteriorate. .

On the other hand, according to the solid-state laser device of the end pump excitation type, the mode of the semiconductor laser beam for exciting the solid-state laser medium and the mode of the oscillation laser beam are arranged by coaxially arranging the semiconductor laser beam and the oscillation laser beam. Has the advantage that it is easy to obtain very high efficiency and good transverse mode, but the configuration in which the semiconductor laser beam is input from the surface of the optical element that requires a high reflectance for the oscillation laser beam wavelength Therefore, there is a demand for an optical element such as a high transmission required for a semiconductor laser beam wavelength, and it becomes difficult to manufacture the optical element, or a state in which substantially high efficiency cannot be obtained. There is a disadvantage of doing so.

The present invention has been made in view of such circumstances, and a semiconductor laser-pumped solid-state device capable of achieving a pumping efficiency comparable to that of an end-pump pumping system with a simple configuration. It is intended to provide a laser device.

[0007]

To achieve the above object, the present invention relates to a solid-state laser device which excites a solid-state laser medium disposed in a resonator using a semiconductor laser and oscillates a laser beam. The semiconductor laser beam is characterized in that the solid-state laser medium is excited by irradiating the semiconductor laser beam to the oscillation laser beam transmission surface of the solid-state laser medium without passing through the resonator mirror from a direction different from the laser optical axis to be oscillated. .

According to the semiconductor laser-excited solid-state laser device of the present invention having the above-described structure, good pumping efficiency can be obtained with a simple structure.

The reason will be described below in comparison with a more efficient end-pump pumping type solid-state laser device among the two pumping methods currently proposed.

First, in an end pump excitation type device,
It is necessary to apply a coating to the coupling mirror constituting the resonator so as to have a high reflectance with respect to the wavelength of the laser beam to be oscillated and to realize a high transmittance with respect to the wavelength of the semiconductor laser beam.

On the other hand, in the solid-state laser device of the present invention, the semiconductor laser beam is irradiated onto the solid-state laser medium without passing through the resonator mirror. Can be separated. Here, due to the nature of the optical thin film, while maintaining the high reflectance required for laser oscillation while maintaining a high transmittance that achieves sufficient excitation efficiency for the semiconductor laser beam wavelength, the laser oscillation It is much easier to realize a high transmittance that realizes a sufficient excitation efficiency with respect to the wavelength of the semiconductor laser beam while maintaining the high transmittance required for the laser beam. Therefore, when the configuration of the present invention is employed, the loss due to coating can be reduced, and an efficient resonator can be configured.

The mode of the semiconductor laser beam in the solid-state laser medium and the mode of the oscillating laser beam required for achieving a good transverse mode are determined by setting the thickness of the solid-state laser medium to the oscillating laser beam of the laser medium. When the incident angle of the oscillating laser beam and the incident angle of the semiconductor laser beam with respect to the transmission surface is within the allowable range, it is possible to secure the solid laser device without largely breaking it. Can obtain good excitation efficiency comparable to the end pump excitation method.

Here, in the solid-state laser device of the present invention, as shown in FIGS. 2 and 3, a plurality of semiconductor lasers 1, 11 or 1, 11, 21, 3, 3 are used as excitation light sources.
1, the respective output laser beams are applied to the oscillation laser beam transmitting surfaces 5a and 5b of the solid-state laser medium 5 without passing through the resonator mirrors 3 and 4 from directions different from the oscillation laser optical axis. The solid-state laser medium 5 may be configured to be excited. In this case, the excitation energy can be increased without changing the excitation efficiency and without using an extra element such as a polarization beam splitter. .

As another method for increasing the pumping energy, a high-power semiconductor laser having a wide stripe width (for example, a semiconductor laser having a gain-guided broad stripe structure) is used as an excitation light source and the stripe direction of the semiconductor laser is changed. There is also a configuration in which the solid-state laser medium is excited in a direction substantially perpendicular to the plane including the oscillation laser optical axis and the excitation beam.

In the solid-state laser device according to the present invention, as shown in FIG.
SHG element (wavelength conversion element) in a resonator composed of
6 to arrange a semiconductor laser-excited solid-state laser device capable of efficiently extracting the second harmonic and / or sum frequency of one or more laser beam wavelengths oscillated in the resonator. Can be.

[0016]

FIG. 1 is a block diagram of an embodiment of the present invention.

The solid-state laser device according to the present embodiment has a semiconductor laser 1, which is an excitation light source, a collimator lens 2a, a focusing lens 2b, two resonator mirrors 3 and 4 forming a resonator, and two resonator mirrors. Not very thick solid-state laser medium 5 arranged on the optical axis between the mirrors 3 and 4
And so on.

The semiconductor laser 1 is disposed so that the optical axis of the excitation laser is obliquely inclined with respect to the optical axis of the resonator mirrors 3 and 4 (optical axis of the oscillation laser), and its output laser beam (excitation beam) L1 Are condensed by the collimator lens 2a and the focusing lens 2b, and pass through the oscillation laser beam transmitting surface 5 of the solid-state laser medium 5 without passing through the resonator mirrors 3 and 4 from a direction different from the oscillation laser optical axis.
a.

As a result, the solid-state laser medium 5 is excited,
The laser oscillates in a resonator constituted by the two resonator mirrors 3 and 4, and the oscillated laser beam LB is extracted outside through the resonator mirror 4 on the output side.

In this embodiment, the angle between the optical axis of the oscillation laser and the optical axis of the excitation laser is determined by the oscillation laser mode diameter in the solid-state laser medium 5 and the beam profile near the focus point of the excitation beam L1. In consideration of the thickness of the solid-state laser medium 5 and the thickness of the solid-state laser medium 5, the oscillation laser mode and the pumping laser mode in the solid-state laser medium 5 are set to be in a range substantially coincident with each other. , The pumping beam L1 does not pass through the resonator mirrors 3 and 4 while achieving the pumping efficiency close to the case where the wavelengths are matched. The performance of the resonator mirror is improved by eliminating the characteristics and reducing design constraints.

Here, in the configuration shown in FIG. 1, if a high-output semiconductor laser having a wide stripe width, for example, a semiconductor laser having a gain-guided broad stripe structure is used as the pumping light source, the pumping can be performed by one semiconductor laser. Energy can be increased. Further, in this case, if the stripe direction of the high-power semiconductor laser is made to coincide with a direction substantially perpendicular to the plane including the oscillation laser optical axis and the excitation beam to excite the solid-state laser medium, Since the irradiation area of the solid-state laser medium with the excitation beam can be concentrated on the transmission area of the oscillation laser beam in the solid-state laser medium, the excitation energy can be further increased.

FIG. 2 is a block diagram of another embodiment of the present invention. In this embodiment, two semiconductor lasers 1 and 11 are used as excitation light sources, and one of the semiconductor lasers 1 and 11 is used.
1 and the condensing lenses 2a and 2b are arranged in the same manner as shown in FIG. 1, and the other semiconductor laser 11 and the condensing collimator lenses 12a and 12b are placed with the optical axes of the resonator mirrors 3 and 4 interposed therebetween. The oscillation laser beam transmitting surface 5 a of the solid-state laser medium 5 is disposed at a position symmetrical to the semiconductor laser 1.
It is characterized in that two excitation beams L1 and L11 are simultaneously irradiated to the same region (surface on the side of the resonator mirror 4).

FIG. 3 is a configuration diagram of another embodiment of the present invention. In this embodiment, four semiconductor lasers 1, 11, 21 and 31 are used as excitation light sources, two of which are semiconductor lasers 1 and 11 and a lens 2 for focusing.
a, 2b and 12a, 12b are arranged in the same manner as shown in FIG. 2 so as to irradiate two excitation beams L1 and L11 to the same region of the oscillation laser beam transmitting surface 5a of the solid-state laser medium 5. At the same time, the remaining two semiconductor lasers 21 and 31 and the condensing collimator lenses 22a and 22
b, 32a and 32b are defined as planes passing through the center of the solid-state laser medium 5 (planes orthogonal to the optical axes of the resonator mirrors 3 and 4).
Are disposed symmetrically with the semiconductor lasers 1 and 11 with the two excitation beams L21 and L31 also provided on the other laser beam transmitting surface 5b (surface on the side of the resonator mirror 3) of the solid-state laser medium 5. Is characterized in that it is configured to irradiate light.

By employing the configuration shown in FIGS. 2 and 3, it is possible to increase the pumping energy without changing the pumping efficiency and without using an extra element such as a polarizing beam splitter. Become.

FIG. 4 is a configuration diagram of still another embodiment of the present invention. In the present embodiment, in addition to the configuration of FIG. 1, an SHG element 6 that generates the second harmonic and / or the sum frequency is provided on the optical axis between the two resonator mirrors 3 and 4. In addition to the arrangement, the surface of the resonator mirror 4 on the laser beam output side shows a high reflectance with respect to the laser wavelength oscillated from the solid-state laser medium 5, and its second harmonic
It is characterized by a coating that shows high transmittance for the sum frequency, so that the second harmonic and sum frequency of one or more oscillation laser beam wavelengths can be obtained with high excitation efficiency. There is.

Here, the present invention provides a method as shown in FIG.
In addition to a solid-state laser device having a structure in which a solid-state laser medium is arranged on the optical axis between at least two resonator mirrors, one surface of the solid-state laser medium is coated with a coating exhibiting a high reflectance with respect to the wavelength of the oscillation laser beam. The present invention can also be applied to a so-called edge-pumped semiconductor laser-pumped solid-state laser beam in which a resonator is formed by using the coating surface as one resonator mirror.

The present invention also relates to a second embodiment as shown in FIG.
In addition to a solid-state laser device for obtaining a harmonic and a sum frequency, a second harmonic of a fundamental wave oscillated from a solid-state laser medium is generated in a resonator, and the second harmonic is converted into a wavelength for generating a fourth harmonic. The present invention is also applicable to a wavelength conversion laser device that resonates in a resonator including a conversion element to obtain a fourth harmonic.

[0028]

As described above, according to the semiconductor laser-excited solid-state laser device of the present invention, the solid-state laser medium is irradiated with the excitation beam from the semiconductor laser without passing through the resonator mirror. Therefore, there is no need to consider the transmittance at the excitation beam wavelength in the coating of the resonator mirror, which reduces the design constraints, thereby improving the performance of the resonator mirror and improving the efficiency of the resonator mirror. Can be configured. In addition, since the excitation beam is applied to the oscillation laser beam transmitting surface of the solid laser medium, the oscillation laser mode and the excitation laser mode in the solid laser medium can be substantially matched. Therefore, it is possible to obtain a good pumping efficiency comparable to the end pump pumping system. Moreover, such excitation efficiency can be easily realized with simpler coupling mirror characteristics.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of another embodiment of the present invention.

FIG. 3 is a configuration diagram of another embodiment of the present invention.

FIG. 4 is a configuration diagram of still another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor laser 2a Collimator lens 2b Focusing lens 3,4 Resonator mirror 5 Solid laser medium 5a, 5b Oscillation laser beam transmission surface 6 SHG element L1 Excitation beam LB Oscillation laser beam

Claims (3)

[Claims] 1. A solid-state laser device that excites a solid-state laser medium disposed in a resonator using a semiconductor laser and oscillates a laser beam. The solid-state laser device oscillates a semiconductor laser beam from a direction different from a laser optical axis that oscillates. A semiconductor laser-excited solid-state laser device characterized in that a solid-state laser medium is excited by irradiating an oscillation laser beam transmitting surface of the solid-state laser medium without passing through a resonator mirror. 2. The semiconductor laser-pumped solid-state laser according to claim 1, wherein a plurality of semiconductor lasers are used as the pumping light source, and each output laser beam is applied to the solid-state laser medium under the above-mentioned conditions. apparatus. 3. The semiconductor according to claim 1, wherein an SHG element is disposed in the resonator to generate a second harmonic and / or a sum frequency of an oscillation laser beam wavelength. Laser-excited solid-state laser device.