JP2671316B2 - Harmonic generation solid state laser device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a solid-state laser device for generating high-frequency laser output harmonics. [Prior art] ND ^3: conventional solid state lasers using crystals such as YAG, which has been using an arc lamp or the like to the excitation light, backward pumping type solid-state laser with high efficiency have been proposed a compact using a semiconductor laser, It is beginning to be used (Fig. 2). This solid state laser is ND ³ :
In the case of YAG, it oscillates at a wavelength of 1064 nm, but since there is a high need for a shorter wavelength, a nonlinear optical element is used to generate the second harmonic, and light of 532 nm is used. In order to efficiently generate this second harmonic, the conversion efficiency of the nonlinear optical element is proportional to the light density, so the nonlinear optical element is arranged in the optical resonator. [Problems to be Solved by the Invention] However, since it is necessary to increase the density of light in order to increase the conversion efficiency of the second harmonic, the optical system such as a lens is complicated. Further, in order to achieve the phase matching of the non-linear optical element, generally, the angle phase matching in a wide operating temperature range is performed without performing the temperature control, but the stability is uncertain because the number of parts increases. [Object of the Invention] The present invention has been made to solve the above-mentioned problems, and by bonding a solid-state laser material and a non-linear optical element with an optical resin, a harmonic of a fixed laser that is highly efficient and easy to adjust is provided. The purpose is to provide a wave generation method. [Means for Solving the Problems] In order to achieve this object, a harmonic-generating solid-state laser device of the present invention is provided with a Brewster angle with respect to the optical axis at one end face of a fixed laser material arranged in an optical resonance system. And the other end surface of the solid-state laser material is perpendicular to the optical axis, and a non-linear optical element is bonded and arranged on either the perpendicular surface or the surface formed by the Brewster angle. It is characterized by becoming. [Operation] In the invention having the above configuration, when excitation light is incident on the fixed laser material, fluorescence is emitted, which is amplified and laser-oscillates in the optical resonance system. At this time, the second harmonic is generated by the nonlinear optical element bonded to the solid-state laser material. Embodiment An embodiment embodying the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the harmonic generating means of the solid-state laser of the present invention. The YAG rod 130 has one surface cut and polished at Brewster's angle with respect to the optical axis and the other end polished perpendicularly to the optical axis. In the case of YAG crystal, Brewster's angle is 61.2 degrees with respect to the optical axis. N
A material having a concentration of d ³ of about 0.8 to 1.0 at% can be preferably used. The angle of the non-linear optical element 120 is adjusted so as to satisfy the angle phase matching condition on this vertically polished surface, and the surface is bonded with an ultraviolet curable resin. For adjustment, after roughly aligning the axial directions, laser oscillation is actually carried out and bonding is performed at an angle at which the intensity of the second harmonic is maximized. KTP or the like is suitable for the nonlinear optical element 120. If the UV curable resin to be adhered has a refractive index of about 1.55, the reflection at the joint is about 1.1%, but it can be further reduced by attaching a dielectric thin film.
On the opposite side of the non-linear optical element 120 from the bonding surface, a thin film is attached so as to transmit 810 nm light and reflect 1064 nm and 532 nm light. The side cut at the Brewster's angle of YAG rod 130 is 10
A thin film is attached so as to transmit light of 64 nm and 532 nm. The exit mirror 140 is 1064nm on the concave side of a plano-concave lens with one side of R60mm.
A thin film that reflects 100% of light and transmits 532 nm light is created. The reflection surface of the non-linear optical element 120 and the reflection surface of the emission mirror 140 are separated by about 35 mm, and have a shape obtained by dividing the confocal optical resonator into two parts. At this time, the beam diameter is 0.2 mm on the reflecting surface of the nonlinear optical element 120 and 0.28 mm on the emitting mirror 140, and the light density is highest on the reflecting surface of the nonlinear optical element 120. The semiconductor laser 100 emits light having a wavelength of 810 nm. Laser diode 10
A condenser lens 110 is arranged between 0 and the nonlinear optical element 120. The 810 nm light of the semiconductor laser 100 is condensed in the optical resonance region by the condenser lens 110. Light of semiconductor laser 100 YAG rod
Nd ^{3 in} 130 is excited and emits fluorescence, which is a nonlinear optical element.
An optical resonator consisting of the mirror surface of 120 and the exit mirror 140
Laser oscillation at 1064nm. At this time, since one of the YAG rods 130 is cut at the Brewster's angle, the laser light becomes linearly polarized light having an electric field vector parallel to the plane including the optical axis and the normal to the emitting surface. This laser light has a high intensity in the optical resonator and has the highest light density in the non-linear optical element 120, so it is efficiently converted into the second harmonic wave and emitted from the emission mirror 140. [Effects of the Invention] As is clear from the above description in detail, according to the present invention, one end face of the solid-state laser material is formed with a surface forming a Brewster angle with respect to the optical axis. It is not necessary to include a so-called Brewster plate for controlling the deflection in the system. Therefore, the loss due to reflection and absorption is reduced, and the output can be increased. Further, since the non-linear optical element is bonded to either one end surface or the other end surface of the solid-state laser material, it is necessary to assemble the respective members such as the non-linear optical element and the Brewster plate as independent parts. In addition, stable harmonics of a solid-state laser can be generated with a simple structure, and a large laser output can be obtained. Therefore, if it is used for a pickup of an optical disk, it is advantageous that the information recording density can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an embodiment embodying the present invention, and FIG. 2 is an example of a conventional back-pumped solid-state laser. In the figure, 100 is a semiconductor laser, 120 is a nonlinear optical element, and 130 is Y.
AG rod, 140 is an output mirror.

Claims (1)

(57) [Claims] In a harmonic generation solid-state laser device in which a solid-state laser material and a nonlinear optical element are integrally arranged in an optical resonance system, one surface of the solid-state laser material has a surface forming a Brewster angle with respect to an optical axis. At the same time, the other end surface of the solid-state laser material forms a vertical surface with respect to the optical axis, and the nonlinear optical element is bonded and arranged on either the vertical surface or the surface forming the Brewster angle. Harmonic generation solid state laser device.