JPH06177471A - Semiconductor laser excited solid-state laser using prism enlarger - Google Patents

Abstract

PURPOSE:To enable an efficient laser beam to be taken out even though a solid-state laser excited by an LD is the type in which only a limited region is partially excited by the laser, and, in the event of taking the laser beam from a lateral direction, to make a section of the discharged laser beam into an easy-to-use round or square form, and to improve its focusing characteristics. CONSTITUTION:In a laser resonator which comprises two mirrors 2 and 6 provided at least on both ends, one or a plurality of prism enlarger 7 are permitted to intervene, thereby enlarging a laser beam section in the laser resonator only in one direction so that the laser beam enters into the fixed laser medium as a rectangular or elliptic laser beam equal to an excitation region of a laser medium 1.

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 prism magnifier, that is, a crystalline or glassy solid-state laser device pumped by a semiconductor laser array.

[0002]

2. Description of the Related Art Lasers made of crystalline or glass, which are generally called solid-state lasers, have hitherto been excited by irradiating a solid-state laser medium with a powerful lamp light from an arc or an incandescent lamp. With the advent of the high-power semiconductor laser, the semiconductor laser (hereinafter, referred to as LD) is being replaced with a lamp light, and a solid-state laser is being excited. However, in a solid-state laser having a long absorption length of LD light (for example, Nd: YAG laser), the absorption length is long in the depth direction as compared with the narrow excitation width obtained by condensing the LD light with a lens. When the solid-state laser light is excited and taken out in the lateral direction (the direction perpendicular to the direction of excitation by the LD light), the cross section of the laser light is not an easy-to-use circular cross section but an elongated rectangle, and the condensing characteristic is also It had the drawback of getting worse.

[0003]

In view of the above point, the present invention makes it possible to efficiently extract laser light from an elongated non-circular pumping region in a solid laser medium by LD pumping, and to use the laser light Even when the light is extracted in the lateral direction (direction orthogonal to the direction of excitation by the LD light), the cross section of the emitted laser beam is formed into a circular or square shape that is easy to use, and the condensing characteristics are improved.

[0004]

To achieve the above object, one or several prism magnifiers are intervened in a laser resonator having at least two mirrors placed at both ends. The structure is such that the cross section of the laser beam in the laser resonator is expanded in only one direction so that a rectangular or elliptical laser beam equal to the excitation region of the laser medium is passed through the solid laser medium.

[0005]

With the above structure, the laser medium is L
Even if only a limited region is partially excited by D, one or a few prism magnifiers intervening the laser medium have a rectangular shape or a long length equal to the active region (optical amplification region) of the laser. The circular laser light is filled without waste, enabling efficient extraction of the laser light from the entire active area and increasing the laser output. Further, the cross-sectional shape of the laser beam emitted from the laser resonator is narrowed down into a circular shape or a square shape to make it easy to use.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a conceptual diagram of a first embodiment relating to a semiconductor laser pumped solid-state laser of the present invention. The solid-state laser is a solid-state laser doped with neodymium (Nd) or other rare earth. As a solid material,
It is vitreous or crystalline, including quartz. The crystals are
It is selected from YAG, YVO4, YLF, YOS, YAP and the like. Among them, especially Nd: YAG, Nd: YL
F and Nd: YOS are important. Here, Nd: YA
A G (Y3Al5O12) crystal will be described as an example. In the present invention,
It is added that the Nd: YAG crystal is not limited. Nd: YAG crystal (hereinafter simply referred to as YAG crystal) 1 is a total reflection mirror with each surface being a vertical surface and the rear end surface being coated with a dielectric multilayer film for total reflection at a laser wavelength of 1.064 microns. 2 to form the upper and lower surfaces 3
Is optically polished, and a non-reflection coating for LD light having a wavelength of 0.808 micron is applied to enable excitation by the LD array 4. Further, heat sinks (not shown) for cooling are closely attached to both side surfaces. The thickness of the YAG crystal 1 varies depending on the Nd mixture ratio in the crystal, but a thickness of 3 to 5 mm is suitable so that the inside of the crystal is uniformly excited by LD light. The crystal length is LD
Choose at least the length of array 4. When using a plurality of LD arrays 4, it is necessary to have a length equal to or greater than the length in which they are arranged. A condenser lens 5 is provided on each of the upper and lower surfaces of the YAG crystal 1.
The LD array 4 is made to face each other via the YAG crystal 1 by collecting the laser light diverging from each LD array by the condenser lens 5.
I try to focus on. The LD array 4, which is also called a laser diode, is composed of an LD that produces a laser output having a wavelength of about 0.8 μm, and is designed to emit a plurality of laser beams from one semiconductor chip. Pulse oscillation or continuous oscillation is performed. The heat generated from the LD of the LD array 4 is removed by a temperature-controlled Peltier cooler or a temperature-controlled water-cooled heat sink (not shown). This allows
Adjust the LD temperature, and adjust the LD to YAG
Tune to the exact wavelength that matches the excitation of crystal 1. YAG
In front of the crystal 1, a partial reflection mirror 6 also serving as an output mirror of the laser resonator is arranged, and the partial reflection mirror is coated with a dielectric material so that a part of the fundamental wavelength of the laser light is transmitted. Therefore, a laser resonator is formed between the total reflection mirror 2 and the reflection mirror 2.

In this laser resonator, two triangular prisms 7 which are prism expanders are intervened to expand the laser light cross section in the laser resonator in only one direction to form a rectangle equal to the excitation region of the laser medium. An oval laser beam is passed through the YAG crystal 1.
The triangular prism 7 is a basic shape of a prism magnifier, but the triangular prism referred to here is a prism having a right angle or an angle close to that, and its material is quartz, various optical glasses, optical crystals such as sapphire. Are suitable. The surface (A surface) of the prism where the laser light is expanded and emitted (incident) from the prism is at a right angle or an angle close to the laser light. An antireflection coating is applied to the surface (A surface) so as to reduce surface reflection loss. Other side (B side)
Choose a Brewster angle or an angle close to it for the laser light. This Brewster angle is an angle at which reflection on the prism surface does not occur with respect to the P-polarized component of the laser, and is 56.5 degrees for BK7 glass. When the Brewster's angle is not used, the surface (B surface) is coated with an antireflection coating to prevent surface reflection. The enlargement ratio by one triangular prism 7 is kept low at about 2 to 5 times, and a plurality of enlargement ratios are used when a large enlargement ratio is required.
The surface B may be provided with a slight surface reflection without using the Brewster angle, and the reflected light may be used as the measurement light of the laser characteristics. In this case, the laser monitor 9 that receives the reflected light is placed in a proper place. Further, an aperture aperture 8 is provided in the vicinity of the partial reflection mirror 6 in the laser resonator in order to improve the shape and condensing characteristics of the laser light. However, the attachment of the opening aperture 8 may reduce the laser output, and is not always necessary depending on the purpose of use.

FIG. 3 shows a second embodiment. In this case, in the case of the previous example, inside the crystal, in the vicinity of the aperture aperture 8 in the laser resonator, particularly in the portion between the partially reflecting reflecting mirror 6 and the triangular prism 7 where the laser intensity per unit area is the highest. A KTP (KTiOPO4) crystal 10 that halves the wavelength of the laser light passing through is interposed. The position where the laser intensity is the highest per unit area is the place where the generation efficiency of the second harmonic is the highest.

FIG. 4 shows a third embodiment. In this example, a steep pulsed laser is desired for some purposes, and in the second example, the KTP crystal is used.
Instead of 10, a Q switch 11 such as an acousto-optic Q switch or an electro-optic Q switch utilizing the Pockel effect is interposed.

FIG. 5 shows a fourth embodiment. In this case, both the second embodiment and the third embodiment, that is, both the KTP crystal 10 and the Q switch 11 are interposed.

6 to 9 show fifth to eighth embodiments. These are obtained by cutting the front end face 12 of the YAG crystal 1 to Brewster's angle and optically polishing it in the first to seventh embodiments. As a result, one triangular prism 7 is omitted.

[0012]

According to the present invention, L
Even if only a limited area is partially excited by D, the active area of the laser is rectangular or elliptical in the solid laser medium due to the intervention of one or several prism expanders. Can be filled without waste, the whole solid-state laser can be efficiently excited, and the laser output can be increased. Further, the prism magnifier can narrow the cross-sectional shape of the laser beam emitted from the laser resonator into a circular shape or a square shape, can be easily used, and can improve the condensing characteristics. Furthermore, on the side of the laser medium,
A high power LD array having a plurality of LD light emitting parts in one package can be used, and an efficient solid-state laser pumped by the high power LD array can be provided. Moreover, by interposing the KTP crystal in the laser resonator, it is possible to provide an efficient solid-state laser whose frequency is doubled, and it is also possible to obtain a steep pulsed laser by intervening the Q switch. It has a very simple structure and is extremely effective and extremely useful.

[Brief description of drawings]

FIG. 1 is a side view conceptual diagram showing a first embodiment of the present invention.

FIG. 2 is a rear conceptual view of the same example.

FIG. 3 is a side conceptual view showing a second embodiment of the present invention.

FIG. 4 is a side view conceptual diagram showing a third embodiment of the present invention.

FIG. 5 is a side view conceptual diagram showing a fourth embodiment of the present invention.

FIG. 6 is a side conceptual view showing a fifth embodiment of the present invention.

FIG. 7 is a side view conceptual diagram showing a sixth embodiment of the present invention.

FIG. 8 is a side view conceptual diagram showing a seventh embodiment of the present invention.

FIG. 9 is a side conceptual view showing an eighth embodiment of the present invention.

[Explanation of symbols]

 1 YAG crystal 2 Reflection mirror for total reflection 3 Upper and lower surfaces 4 LD array 5 Condensing lens 6 Partial reflection mirror 7 Triangular prism 8 Aperture aperture 9 Laser monitor 10 KTP crystal 11 Q switch 12 Front end face

Claims (1)

[Claims] 1. A laser resonator having two mirrors placed at least at both ends, and one or several prism expanders intervene in the laser resonator so that a laser beam cross section in the laser resonator can be changed. A semiconductor laser pumped solid-state laser using a prism expander, which has a structure in which a rectangular or elliptical laser beam equal to the pumping region of the laser medium is passed through the solid-state laser medium by expanding in only one direction.