JPH06112559A - End face excitation type solid-state laser - Google Patents

Abstract

PURPOSE:To improve the fundamental wave generating efficiency of the title laser while the spreading angle of the output beam is kept small by constituting one end face of a laser medium in the axial direction in a flat or concave surface and the other end face of the medium in a convex surface and making excited light from the flat or concave surface side to incident, and then, positioning the convex surface on the opposite side of the output mirror of an optical resonator. CONSTITUTION:An exciting light beam E the condensed light spot of which is set near the flat surface F of a laser medium 3 is made incident to the medium 3 after passing through the surface F and excites the medium 3. The beam E which is not absorbed in the medium 3 in this stage is reflected by the convex surface CV of the medium 3 and again excites the medium 3. Since the radius of curvature of the convex surface CV is equal to the focal distance of a focusing lens 22, the shapes of the beam E before and after the reflection by the surface CV become equal to each other and the beam E can be recovered and reused at a high efficient. Therefore, a laser beam having a short resonator length and small spreading angle can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an edge-pumped solid-state laser device.

[0002]

2. Description of the Related Art In an edge-pumped solid-state laser using a semiconductor laser or a dye laser as a pumping light source, an axial end face of a solid-state laser medium has been conventionally included, including one having a wavelength conversion element in its optical resonator. As a shape, both ends are flat, or an end surface on the incident side of the excitation light is a convex curved surface and an output mirror side is a flat surface or a concave curved surface.

[0003]

By the way, in the conventional edge-pumped solid-state laser, of the pumping light incident on the optical resonator, the light not absorbed by the medium is
No measures have been taken to reuse it for excitation, which is one of the causes of reduced efficiency.

Among such lasers, the Nd: YAG 946 nm laser, which is difficult to oscillate, needs to use a concentric resonator or a resonator close to it, which has a long resonator length and spreads the laser output beam. There is a problem that the corners also become large.

Further, in the case of performing mode matching between the pumping light and the beam in the optical resonator, there is a problem that the pumping optical system also becomes long. The present invention has been made in view of the above point, and it is possible to recover pumping light that has not been absorbed by a medium with high efficiency and reuse it for pumping, without increasing the length of the optical resonator, and to The fundamental wave generation efficiency can be improved with the divergence angle kept small, and mode matching between the pumping light and the beam inside the optical resonator can be achieved using a compact pumping optical system, which is compact and highly efficient. It is an object of the present invention to provide an edge-pumped solid-state laser that can be pumped and has a small output beam divergence angle.

[0006]

In order to achieve the above-mentioned object, in the end-pumped solid-state laser of the present invention, one end side of the solid-state laser medium has a flat surface or a concave curved surface and the other end side has a convex shape. It is characterized in that it is a curved surface, and the excitation light is incident from the flat surface or the concave curved surface, and the convex curved surface is arranged to face the output mirror of the optical resonator.

[0007]

By the lens action of the convex curved surface of the solid laser medium placed in the optical resonator and facing the output mirror side, the beam shape in the resonator is as shown in FIG. 1 and FIG. Even if the excitation light is condensed by a lens having a high NA (numerical aperture), the mode matching between the excitation light and the intracavity beam can be achieved.

Further, by setting the focus spot position of the excitation light in the vicinity of the flat surface of the medium, the excitation light reflected by the convex curved surface of the medium can also be mode-matched with the intracavity beam to achieve high-efficiency excitation. It will be possible.

Further, for the excitation light that is not absorbed by the medium, the beam shape in the medium before and after the reflection is made by matching the radius of curvature with the focusing lens of the excitation optical system and reflecting the excitation light there. The reflected light and the reflected light can be matched with each other, and the above-mentioned mode matching can be performed, and highly efficient recovery and reuse of the unabsorbed excitation light can be achieved.

Furthermore, due to the lens action of the convex curved surface of the medium, a concentric resonator structure or a resonator structure close to it can be obtained with a short optical resonator length, and the divergence angle of the output beam can be suppressed to a small value. Becomes

[0011]

1 is a block diagram of an embodiment of the present invention, showing an example in which the present invention is applied to a semiconductor laser pumped solid-state laser.

The output light from the semiconductor laser 1 passes through the excitation optical system 2 including the collimating lens 21 and the focusing lens 22 to become the excitation light beam E, which is applied to the solid laser medium 3.

In the solid-state laser medium 3, one end face in the axial direction is a flat face F and the other end face is formed by a convex curved face CV, and the excitation light beam E is applied to the flat face F. The flat surface F of the laser medium 3 is coated with a film having a high transmittance for the excitation light E and a high reflectance for the laser fundamental wave. The convex curved surface CV of the laser medium 3 is coated with a film having a high reflectance with respect to the excitation light E and a high transmittance with respect to the laser fundamental wave.

An output mirror 4 having a concave curved surface having a high reflectance with respect to the laser fundamental wave is disposed facing the convex curved surface CV of the laser medium 3. The output mirror 4 and the laser medium 3 are arranged.
An optical resonator 5 is formed between the flat surface F and the flat surface F, and an output beam is extracted from the output mirror 4.

The focusing spot of the pumping light beam E by the pumping optical system 2 is set so as to be near the flat surface F of the laser medium 3, and the convex curved surface CV of the laser medium 3 is set.
The radius of curvature of is set to match the focal length of the focusing lens 22.

According to the above-described embodiment of the present invention, as shown in FIG. 2 which shows the beam shape in the vicinity of the laser medium 3 in the excited state, the excitation light having a focused spot near the flat surface F of the laser medium 3 is set. The beam E is, as shown by the solid line in the figure,
The excitation light beam E, which is transmitted through the flat surface F and enters the medium 3 to be excited first, and which is not absorbed by the medium 3 in this process, is reflected by the convex curved surface CV of the medium 3 and is again medium. Exciting 3. At this time, the convex curved surface C
Since the radius of curvature of V coincides with the focal length of the focusing lens 22, the shapes of the excitation light beam E before and after reflection by this surface coincide with each other, and the excitation light beam E can be collected with high efficiency. Can be reused.

The laser fundamental wave beam L thus excited resonates between the flat surface F of the medium 3 and the output mirror 4, and the convex curved surface CV of the laser medium 3 is present inside the resonator 5. Since it exists, the fundamental wave beam L in the resonator 5 undergoes shape conversion as shown by the broken line in the figure by the lens effect of the convex curved surface CV, and the beam shape in the medium 3 has a high convergence angle. Even if the excitation light is condensed by the high NA lens, the excitation light beam E and the fundamental wave beam L in the resonator 5 can be mode-matched. Here, since the excitation light beam E has the same beam shape before and after the reflection by the convex curved surface CV as described above, the excitation light beam E and the fundamental wave beam L both before and after the reflection by the convex curved surface CV. Since the mode matching is achieved, the efficiency of collecting and reusing the excitation light beam becomes extremely high.

Further, since the beam shape in the resonator 5 is converted by the convex curved surface CV of the laser medium 3 and has a high convergence angle in the medium 3, even if the radius of curvature of the output mirror 4 is increased,
A concentric resonator or a resonator having a performance close to that can be formed while keeping the length of the resonator 5 short, and the divergence angle of the laser output beam can be suppressed to be small while keeping the short resonator length.

In the above embodiment, the points to be particularly noted are that even if the pumping light is coupled by the high NA lens, the pumping light and the beam inside the resonator can be mode-matched and the divergence angle of the laser output beam can be increased. Is that it gets smaller,
When excitation is performed with a high NA lens in a normal configuration, contradictory matters are achieved at the same time.

In the above embodiments, the flat surface F of the laser medium 3 on the pumping light incident side is highly transmissive to the pumping light and highly reflective to the laser fundamental wave, so that the flat surface F causes resonance. Although one mirror of the container 5 is formed, the flat surface F is made highly transmissive to both the pumping light and the laser fundamental wave, and between the pumping optical system 2 and the laser medium 3,
The same effect can be achieved by separately disposing a mirror that is highly transmissive to the excitation light and highly reflective to the laser fundamental wave.

The convex curved surface CV of the laser medium 3 is also highly transmissive to both the excitation light and the laser fundamental wave, and the output mirror 4 is highly reflective to both the excitation light and the laser fundamental wave. The same effect can be achieved.

In the above embodiments, the end face of the laser medium 3 on the incident side of the excitation light is the flat face F. However, even if this face is a concave curved face, the same effect can be obtained. .

Further, the present invention can be applied to the dye laser pumped solid-state lasers as well as the semiconductor laser pumped solid-state lasers as in the above-described embodiments in the same manner, or the wavelength conversion element in these resonators. Needless to say, the present invention can be applied to the addition of.

[0024]

As described above, according to the present invention,
One of the end faces in the axial direction of the laser medium quality of the end-pumped solid-state laser is a flat surface or a concave curved surface, and the other is a convex curved surface. Since the structure is arranged so as to face the output mirror of, the lens shape of the convex curved surface of the laser medium converts the beam shape in the cavity to a high convergence angle, and the excitation light also enters the medium from a flat surface. It is possible to make the shape of the beam and the light reflected by the convex curved surface the same, and the mode matching between the pump light and the beam inside the cavity, and the high efficiency of the pump light not absorbed by the medium by the first irradiation Recovery and reuse for excitation can be achieved at the same time by using a high-NA excitation light condensing lens, which enables highly efficient excitation.

Further, as a result of the beam shape conversion in the resonator beam due to the lens action of the medium, even if an output mirror having a large radius of curvature is used, the optical length of the resonator is kept short and concentric or close to it. A resonator can be configured, and a laser having a short resonator length and a small beam divergence angle can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment when the embodiment of the present invention is applied to a semiconductor laser pumped solid-state laser.

FIG. 2 is an explanatory diagram of a beam shape in the vicinity of a laser medium 3 in the excited state.

[Explanation of symbols]

 1 Semiconductor Laser 2 Excitation Optical System 21 Collimating Lens 22 Focusing Lens 3 Solid State Laser Medium F Flat Surface CV Convex Curved Surface 4 Output Mirror 5 Optical Resonator

Claims (1)

[Claims] 1. A laser for introducing pumping light from one end face in the axial direction of a solid-state laser medium and confining the generated spontaneous emission light in an optical resonator to cause stimulated emission. The one end side is a flat surface or a concave curved surface and the other end side is a convex curved surface, and the excitation light is incident from the flat surface or the concave curved surface, and the convex curved surface is arranged to face the output mirror of the optical resonator. An edge-pumped solid-state laser characterized by the above.