JPH03256030A - Optical device - Google Patents

Abstract

PURPOSE:To eliminate the need for temperature control and to make an optical axis of projection constant by inputting incident light to an optical waveguide, and outputting higher-harmonic projection light with wavelength 1/n except from the optical waveguide. CONSTITUTION:The incident light 4 is made inputted to the optical waveguide 2 and the higher-harmonic projection light 6 with the wavelength 1/n is outputted except from the optical waveguide 2. Even when the projection angle of the higher harmonic varies with temperature, a voltage applied to a provided electrode 3 to vary the refractive index of the optical waveguide 2 or a substrate 1 by electrooptic effect, thereby making the projection angle constant. Consequently, the need for the temperature control is eliminated and the optical device which can be expected to perform stable operation with a constant optical axis is obtained.

Description

[Detailed Description of the Invention] Industrial Application Field Invention 41 This relates to an optical device that shortens the wavelength of laser light to 1/n, and is particularly expected to eliminate the need for temperature control and provide stable operation with a constant output optical axis. Regarding optical devices that can be used, SHG (
second harmonic generation
n, n = 2), THG (third h
armonic generation n = 3
) etc. 4 An example of SHG is the one shown in Figure 2 (Taniuchi et al. “Second harmonic generation of semiconductor lasers”, Applied Materials Science Vol. 56, No. 12, 1637
Wind 1987). As the substrate 1, a LiNbO5 crystal having a second-order nonlinear effect is used. Even if one part is made into an optical waveguide 2 with a high refractive index by proton exchange, a semiconductor laser beam 4 with a wavelength of 0.84 μm is emitted from the end face of the optical waveguide 2. When the light is incident, SHG is generated by Cerenkov radiation, the wavelength of the incident light is halved, and a harmonic wave 6 with a wavelength of 0.42 μm is emitted from the end face of the substrate l or the plate at an angle α. Problems to be Solved In the conventional optical device shown in Figure 2, the harmonic output angle α
Force exchange Film thickness of optical waveguide I Refraction wind Depends on the refractive index of the substrate 1, etc., and even though these values depend on temperature, the output angle of harmonics changes as the temperature changes. When using the incident light 6 as a light source, there was a problem that the optical axis was twisted.Therefore, this optical device required a precise temperature control system of 1°C, and the present invention 1 was made in view of the above problems. The present invention provides an optical device that does not require mold temperature control and has a constant output optical axis.To solve this problem, a substrate is provided, and an n (
(n is an integer of 2 or more) an optical waveguide having the following nonlinear optical effect, and an electric field in the optical waveguide provided on or in the optical waveguide or on or in the substrate so as to sandwich the optical waveguide. The present invention also works by inputting incident light into the optical waveguide and outputting harmonic light with a wavelength of 1/n from a source other than the optical waveguide. Focusing on the fact that it has an optical effect, the output angle of harmonics changes with temperature changes, and by applying a voltage to the electrodes provided, the electro-optical effect changes the refractive index of the optical waveguide or substrate. Therefore, although the optical device of the present invention does not require temperature control and stable operation with a constant output optical axis is achieved, FIG. The constituent countries of optical equipment
An embedded optical waveguide 2 is formed in a substrate 1. Electrodes 3 are provided to sandwich the optical waveguide 2. As a substrate 1, for example, a second-order nonlinear optical effect of a Z plate with a volume of 2 x 2 x 6 mm is used. For example, an embedded optical waveguide 2 with a width of 2μ, a depth of 0.4μ and a length of 6mm was formed on the substrate 1 by proton exchange using LiNbO5 crystal with birophosphoric acid (H,P!○〒〉). Electrodes 3 with a radius of 0.5 mrrc and a length of 6 mm are placed on the substrate 1 with a metal such as ALAu so as to sandwich the optical waveguide 2 therebetween.
This electrode 3 may be formed so that an electric field is applied to the optical waveguide 2, and may be provided on the optical waveguide 2, in the optical waveguide 2, or in the substrate 1. When the semiconductor laser beam 4 of 0.84 μm is linearly polarized in the vertical direction and is incident on the substrate 1, most of it (very much
A part of the force wave that becomes the fundamental wave output light 5 and exits from the optical waveguide 2 is SHG due to Cerenkov radiation, and a nonlinear combination of the fundamental wave guiding mode and the harmonic radiation mode occurs, which occurs at the wavelength of the incident light. For example, in the case shown in Fig. 1, the end face of the substrate l is
For example, when the temperature is 23°C, the harmonic laser beam 6 with a wavelength of 0.42 μm is emitted at an angle α=16.2°.
This exit angle α is CO8α=N/n n=n*rl@/Jre6 C08α+n@S 1 nα
given so as to satisfy t, where, n・, n・
are the refraction winds of the ordinary light and extraordinary light of LiNb0*, respectively, and the refraction wind N is the effective refractive index of the guided light.In other words, the output angle of the plate is: The refractive index depends on the film thickness of the optical waveguide 2, the refraction wind, and the refractive index of the substrate 1.The value of these refractive indexes also depends on the temperature.Next, a voltage is applied to the electrode 3 so that an electric field is applied to the optical waveguide 2. When an electric field is applied to a medium with a second-order nonlinear optical effect such as LiNbOs, which has a large electro-optic effect, the refractive index changes depending on the magnitude and direction of the electric field. As shown in FIG. When applied, the output angle changes and the initial output angle (16,2°)
It is possible to achieve stable operation with a constant optical axis at the outflow angle.
Although it is estimated that the refractive index change due to the electro-optic effect is significant in the substrate immediately below the optical waveguide 2, the guided light propagating through the optical waveguide 2 leaks. Even if there is no change in the refractive index in the optical waveguide 2, if the refractive index of the substrate l changes, the output angle can be changed. Therefore, even if the optical waveguide 2 has no electro-optic effect, the substrate 1 has an electro-optic effect. If there is, the effect of the present invention will still be t = L i N b Os or LiTa
Since the refractive index of O5 strongly depends on the temperature, the effect of the present invention is large.
・Force pulling, which is the case of SHG using for the substrate and optical waveguide
In particular, when a second-order nonlinear effect is exhibited, the effect of the present invention is that it efficiently exhibits the g & electro-optic effect.
LilOs, KNbOs, KTiOPO4, L
If a polymer containing a π-electron conjugated compound with a benzene ring, such as TaOs'P or MNA (methylnitroaniline), is used for the optical waveguide, the effect can be increased.It can also produce third-order or higher-order nonlinear optical effects. If a substance exhibiting an electro-optic effect is used as a substrate for the optical waveguide, the effect of the present invention will be less because the L-layer exhibits an electro-optic effect. Effects of the Invention The present invention has the effect of making it possible to construct an optical device that does not require temperature control and can be expected to operate stably with respect to the optical axis.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the configuration of an optical device according to an embodiment of the present invention. FIG. 2 is a perspective view showing the configuration of a conventional optical device. @3... Electrode 4
...Incidence i5... Fundamental wave output light 〇... Harmonic wave output 9

Claims (4)

[Claims] (1) a substrate, an optical waveguide provided on or in the substrate and having an n-th order nonlinear optical effect (n is an integer of 2 or more); an electrode for applying an electric field to the optical waveguide, provided in at least one of the optical waveguide, on the substrate, or in the substrate, and inputting incident light into the optical waveguide;
An optical device characterized in that harmonic output light having a wavelength of 1/n is output from a source other than the optical waveguide. (2) The optical device according to claim 1, wherein n is 2. (3) The optical device according to claim 1, wherein the substrate has an electro-optic effect. (4) The optical device according to claim 1, wherein the substrate is LiNbO_3 or LiTaO_3.