The present invention relates to a solid-state laser device, a machining apparatus using the same, and a solid-state laser device having a movable laser medium holding means.
Recently, the development of laser devices as light source devices has been pushed and is now approaching a practical application stage. Particularly, a laser device wherein a laser medium crystal is excited by the emission of light from an excitation lamp is laser beam over a wide wavelength range from visible to infrared, depending on the kind of the crystal used.
Such lasers using crystals are generically called solid-state lasers and various kinds of solid-state lasers have been developed and used practically, using yttrium-aluminum-garnet doped with neodymium (hereinafter referred to as Nd:YAG), titanium-doped sapphire, ruby, alexandrite, etc. as laser media.
A low beam divergence is a characteristic feature of laser beam, and by utilizing this feature it is made possible to radiate a small dense spot of energy. Among the aforementioned laser crystals, Nd:YAG has a wavelength of 1.06 .mu.m falling under the infrared region and is in wide use mainly for machining using laser.
Laser devices using Nd:YAG laser, as well as machining apparatus using the laser devices such as laser welders and cutters, have been used for welding or cutting of small parts, e.g. electronic parts, because of small power. In these welders or cutters, the laser output is 400 W or so in normal use.
For increasing the laser power, there have been adopted a laser device using two excitation lamps to double the excitation energy; a laser device of a cascade structure wherein two laser rods are arranged in series and there are also arranged two excitation lamps, as shown in FIG. 11; a machining apparatus using laser wherein a plurality of laser rods are arranged in series, as shown in FIG. 12; and a machining apparatus using laser wherein a plurality of laser rods are arranged in parallel, as shown in FIG. 13.
In FIGS. 11 to 13, the reference numeral 1 denotes an excitation lamp, the numeral 2 denotes a laser rod, numeral 3 a power source, numeral 4 a total reflection mirror, numeral 5 an output mirror, numeral 6 a magnifying optical system, numeral 7 a coupling lens for fiber, numeral 8 an optical fiber, and numeral 9 an optical output coupler (emitting unit).
Such machining apparatus using plural laser rods have gradually come to be used as welders in response to the demand for "replacing a contact type electric welding with a non-contact type laser welding to improve the working efficiency" from the industrial world. Like cutters using laser have also been provided.
Further, as a high power type machining apparatus using laser, there has been provided a laser cutter using a carbon dioxide gas laser of 10.6 .mu.m in wavelength as a light source. This type of a laser cutter having an output power of 1 kW or more can be obtained easily.
In such machining apparatus using plural laser rods, however, there is a common problem that since the number of parts is increased accordingly in comparison with the use of a single laser rod, it is not easy to effect maintenance and inspection, the apparatus becomes larger in size or complicated, and the power consumption also increases.
In the foregoing laser welders and cutters using plural laser rods, the adjustment of the laser device itself takes much time although such a maintenance item as electrode replacement in electric welding is excluded. More particularly, in the apparatus of such construction as illustrated in FIG. 12, since the rods are arranged in series, it is difficult to make the characteristics of the laser rods conform to one another, e.g. alignment of the optical axes of the laser rods. Also, in the apparatus of such construction as illustrated in FIG. 13, a problem is encountered in the adjustment of a resonator system of each laser device because there are used plural resonator systems, excitation lamp sources and cooling-water circulating systems.
As to a cutter using a carbon dioxide gas laser, it is difficult to use it in a cutting operation requiring flexibility because laser beam cannot be transmitted using an optical fiber. Further, the material of a reflecting mirror, etc. used in an optical system is restricted to zinc selenide for example and the damage caused by splash of molten metal occurs very frequently during the cutting operation, thus requiring replacement, with the result that the operating cost becomes very high.
On the other hand, in a solid-state laser device using a laser rod of Nd:YAG for example as a laser medium, at the time when the laser rod is excited by means of an excitation lamp, cooling water is circulated continually to cool the laser rod and thereby prevent the storage of heat caused by the excitation. In this laser device, both ends of the laser rod are each held by a cylindrical holder. More specifically, one end portion of the laser rod is inserted into one cylindrical holder and fixed thereto in a liquid-tight state using an O-ring, while the other end portion of the laser rod is inserted into the other cylindrical holder and fixed thereto also in a liquid-tight state using an O-ring. Consequently, both end faces of the laser rod are isolated from the cooling water; that is, the end faces are prevented from coming into contact with the cooling water which would cause the adhesion of foreign matter in the cooling water to the end faces resulting in impairment of the laser oscillation. The cylindrical holders are fixed to the resonator body.
Even if the laser rod is cooled by the cooling water as mentioned above, it is difficult to completely remove a thermal influence on the laser rod. With increase in the luminous intensity of the excitation lamp, the thermal influence on the laser rod becomes more conspicuous to the extent of causing expansion of the laser rod. In this case, if both ends of the laser rods are fixed completely, there may occur breakage of the laser rod. The longer the laser rod, the more conspicuous this tendency.
Conversely, if the rod is not fixed, there will arise a deviation problem of the optical axis of laser beam.