JPH06118357A - Optical modulator - Google Patents

Abstract

PURPOSE:To miniaturize an optical modulator through miniaturization of a single crystal and unification of constitution parts by providing a convergent lens in an optical path, and also, constituting directly an optical thin film corresponding to a phase plate, a plate polarizer for giving a polarization characteristic and a diffraction grating in one end face of this lens or at least one end face of the single crystal and an acid compound for showing an effect. CONSTITUTION:By installing a convergent lens 1l1 between a polarizer 1a and a single crystal 1b, and allowing a convergent light to be made incident on the single crystal 1b, size of the single crystal 1b, and size of a phase plate 1c for modulating furthermore the light which passes through the single crystal 1b and an analyzer 1d are miniaturized. In this case, since a shape of the convergent lens 1l1 passes through the polarizer 1a, a cylindrical lens can utilize it, and it will suffice that only the polarized light is guided into the single crystal 1b. Therefore, it is unnecessary to be the spherical surface, and the value as parts can be reduced due to mass production. Accordingly, a cost reduction and miniaturization are realized in an industrical level, and it takes effect in a field of intensity modulation, phase modulation, etc., of light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in the fields of optical communications, optical information processing, and optical measuring instruments, and is used in the coherent optical field by using electro-optical modulation, magneto-optical modulation, and acousto-optical modulation. The present invention relates to an optical modulator capable of efficiently utilizing the electro-optical effect, magneto-optical effect, and acousto-optical modulation of an optical isolator.

[0002]

2. Description of the Related Art The Pockels effect and Kerr effect are used for electro-optic modulation, the Faraday effect and electromagnetic field change effect are used for magneto-optic modulation, and the refractive index change, Ramanus diffraction effect by ultrasonic waves are used for acousto-optic modulation, The black diffraction effect is used. Most of the substances that cause the Pockels effect, the Faraday effect, or the change in the refractive index, which is the heart of these modulators, are made of single crystals that are difficult to manufacture.

[0003]

However, the conventional technique has a high price, which is the biggest obstacle to the general popularization. On the other hand, when considering, for example, an optical isolator, the higher the optical communication density and the information processing density,
It matches future technological innovation, and further miniaturization is desired. 4, 5 and 6 show principle diagrams of conventional electro-optic, magneto-optic and acousto-optic modulation.

4a, 5a are polarizers, 4b are lithium tantalate and barium niobate, which exhibit the Pockels effect.
Crystals of sodium, strontium barium niobate, lanthanum titanate and the like. 5b ₂ is a yttrium-iron-garnet single crystal exhibiting the Faraday effect surrounded by a cylindrical permanent magnet 5b ₁ or nitrate, phosphate glass or lead containing a large amount of praseodymium, dysprosium, cerium, tvium, etc. Glass, iron nitrate glass,
A composite compound of iron fluoride glass and bismuth oxide glass is shown. FIG. 3 shows an acousto-optic optical polarizer using black diffraction, and a single crystal of lead molybdate, tellurium oxide, or flint glass is used. The above-mentioned modulation capability is expensive because all single crystals are functionally excellent, but at present the quality is high due to epitaxy growth or the like. Also, taking an optical isolator as an example, the amount of light requires a certain area to take in considering the loss in the optical path system, and in addition to the polarizer, the single crystal that forms the skeleton of the modulator must be large. . 4c is a phase plate and 4d
5d indicates an analyzer. FIG. 6 shows that the direction of light was changed as diffracted light by ultrasonic waves, and 6e
Is a transducer, 6b is an ultrasonic absorber, and the light polarization crystal 6b ₁ is lead molybdate or tellurium oxide.

As described above, the conventional optical modulator requires a large block of expensive single crystal, becomes extremely expensive, and is difficult to be small and high performance.

In order to solve the above-mentioned problems, the object of the present invention is to introduce a light focusing means, such as a product such as an optical isolator, which is small in size and can be constructed at low cost. Remarkably reduce the volume of the compound,
And, if necessary, a converging lens (or a diffusing lens) and a diffraction grating are provided on at least one interface of the optical paths of a single crystal or an oxide compound that exerts effects (Pockels, Kerr, Faraday, electromagnetic field displacement), and further simplification , Low cost, downsizing, and resource saving by improving the information density of optical communication, optical information, and optical measuring instruments.

[0007]

In order to solve the above problems, the present invention provides a converging lens in the optical path and exhibits one end surface or effect (Pockels, Kerr, Faraday, electromagnetic field displacement) of this lens. By directly constructing an optical thin film equivalent to a phase plate on at least one end face of a single crystal or an oxide compound, a flat plate polarizer or a diffraction grating that gives polarization characteristics, it is possible to reduce the size of the single crystal and integrate the components. This is a completed miniaturized optical modulator.

The converging lens (or diffusing lens) used in the present invention includes a Fresnel lens, a gradient index lens, an aspherical lens, and a combination lens, and the lens base material is made of glass or plastic. Either may be used, and one having a high refractive index is preferable. Not only the lens but also an organic AR layer or an inorganic AR layer is preferably provided at the optical path interface of the component to improve efficiency.
It is omitted in the drawings of the present invention.

[0009]

As described above, according to the present invention, the size of the single crystal exhibiting the effect of light convergence can be extremely small, the distance between the electrodes can be short in electro-optical modulation, and the voltage loss for obtaining the necessary refractive index can be reduced. Can be reduced. Further, as shown in FIG. 7, a flat plate polarizer 7a was formed on the surface of the light converging lens 7L ₁ by a vacuum evaporation method. Similarly, the light that was diffracted and emerged was also electro-optically modulated by configuring a phase plate and an analyzer with a part of 7 cd. As a result, the volume of single crystals such as lithium tantalate, barium sodium niobate, strontium barium niobate, and lanthanum titanate is 1/20 to 1/10, which is equivalent to the conventional performance. I was able to get In addition, the number of parts is reduced by using the polarizer, phase plate, and analyzer as multi-functional parts, and the assembled product becomes compact, and it does not become bulky at the joint with the laser light transmitter or optical fiber, and it can be used as an optical isolator. It was enough to satisfy the function.
Although details will be described with reference to Examples, the same applies to magneto-optical modulation and acousto-optical modulation.

[0010]

【Example】

(Embodiment 1) FIGS. 1, 2, 3, 7, 8, 9 and 10 show the principle of the present invention. Fig. 1 shows the size of the single crystal and the phase plate and analyzer that further modulate the light passing through the single crystal by installing a converging lens between the polarizer and the single crystal, and allowing the converged light to enter the crystal. It is a smaller size. Since the shape of the converging lens at this time passes through the polarizer, a cylindrical lens can be used, and since only polarized light needs to be introduced into the crystal, it does not need to be spherical, and 11L ₁ shown in FIG. Need only be set according to the polarization angle, and the price of the parts is low because mass production is possible.

In FIG. 2, although it depends on the diffusion state of the incident light, the size of the polarizing plate can be reduced by converging to make the polarizing plate smaller, and thus the crystal body of 2b ₂ or the electromagnet of 2b ₁ Since the magnetic flux density of the permanent magnet can be increased in inverse proportion to the size of the crystal, a compact and efficient specification is possible. Also in FIG. 3, the oscillation efficiency of ultrasonic waves is made possible by downsizing the crystal, and the extraction efficiency of diffracted light can be improved.

(Embodiment 2) FIGS. 7 to 10 show a type in which further miniaturization of the present invention is realized.
a · 10a is a flat plate polarizer formed by vapor deposition method in which two λ / 4 thin films are formed, or a holographic diffraction grating using mechanical, chemical or photoresist, and the thin film serves as a polarizer. There is. On the other hand, the light exiting the crystal has a phase plate and an analyzer, as well as 8c, as indicated by 7cd.
8d and 9d and 8d of the thin film analyzer are shown. The 8d substrate was further converged by a gradient index converging lens to introduce the light into an optical fiber. The manufacturing method is based on the method of the polarizer.

[0013]

According to the present invention, the light converging means is installed in the optical path system of the optical modulator, and the effect (Pockels, Kerr, Faraday, electromagnetic field displacement, ultrasonic refraction, Ramanus diffraction, black diffraction) is obtained.
Express. The volume efficiency of single crystals or oxide compounds is improved, and the number of parts is reduced by adding polarization, phase, and light-analyzing functions to each component in a composite manner. It is realized and effective in the fields of light intensity modulation, phase modulation, polarization plane rotation, switching, deflection, frequency shift, and spectrum analysis.

[Brief description of drawings]

1 to 3 are perspective principle views for explaining an embodiment of the present invention, and FIGS. 7 to 10 are principle side views of other embodiments of the present invention. FIG. 11 is a perspective view for explaining an actually used portion of the cylindrical lens described in the first embodiment.

FIG. 1 is a perspective view showing an electro-optic modulator.

FIG. 2 is a perspective view showing a magneto-optical modulator.

FIG. 3 is a perspective view showing an acousto-optic modulator.

FIG. 4 is a perspective view showing an electro-optic modulator.

FIG. 5 is a perspective view showing a magneto-optical modulator.

FIG. 6 is a perspective view showing an acousto-optic modulator.

FIG. 7 is a side view showing an electro-optic modulator.

FIG. 8 is a side view showing the electro-optic modulator.

FIG. 9 is a side view showing the magneto-optical modulator.

FIG. 10 is a side view showing a magneto-optical modulator.

FIG. 11 is a perspective view showing a cylindrical converging lens.

[Explanation of symbols]

(1,2,4,5) a Polarizer (7,8,9,10) a Thin-film polarizer (1-10) b Single crystal or oxide compound unit (2,5,9,10) that exhibits a modulation effect ) B ₂ Single crystal or oxide compound expressing a modulation effect (1, 4) c Phase plate (1, 2, 4, 5) d Analyzer (9, 10) d Thin film analyzer (7, 8) cd Thin film Phase plate + thin film analyzer (3,6) e Transducer (3,6) e ₁ Ultrasonic absorber ( _{1 to} 3,7 to 11) l ₁ Convergent lens

Claims (1)

[Claims] 1. An optical modulator, characterized in that means for converging light is provided in the optical path system before and after the effect is exhibited.