JPH04156423A - Light waveguide path type polarizer, light waveguide path device provided with such polarizer and manufacture of such device - Google Patents

Abstract

PURPOSE:To obtain a characteristic such as a desirable extinction ratio by forming metal layers on both sides of a light waveguide path formed on a waveguide path base and provided with a higher index of refraction than the base. CONSTITUTION:Metal layers 3 are formed on both sides of a light waveguide path formed at a waveguide path base 1 and provided with a higher index of refraction than the base 1. With this formation of the metal layers 3 on both sides of the light waveguide path 2, absorbing action to the light having the plane of polarization parallel to the base face is generated by the complex index-of-refraction of the metal layers 3. Accordingly, when the light provided with a light element having the plane of polarization parallel to the base face and a light element having the plane of polarization vertical to the base face is injected, the output light is to be only the light having the plane of polarization vertical to the base face. A characteristic such as a desirable extinction ratio can be thereby obtained.

Description

Detailed Description of the Invention Overview Regarding an optical waveguide type polarizer, an optical waveguide device equipped with the polarizer, and a method for manufacturing the device, the main objective is to realize an optical waveguide device with good characteristics such as extinction ratio. For example, an optical waveguide type polarizer formed by forming an optical waveguide with a higher refractive index on a waveguide substrate than that of the substrate and forming metal layers on both sides of the optical waveguide is integrally provided in the optical input part. Configure.

INDUSTRIAL APPLICATION FIELD The present invention relates to an optical waveguide type polarizer, an optical waveguide device equipped with the polarizer, and a method for manufacturing the device.

In the field of optical communication or optical transmission, in addition to transmitters, receivers, and transmission lines, various optical devices such as optical switches and optical couplers are used. One type of optical device is a waveguide type. This type of optical waveguide device has an optical waveguide formed on a waveguide substrate and is configured to control a light beam while confining it within the optical waveguide, and is easy to miniaturize due to its structure. In addition to the advantage that it can be mass-produced using planar technology, etc.
It has the advantage of being able to effectively apply an electric field or magnetic field and dramatically reducing power consumption. Many optical waveguide devices utilize the electro-optic effect of crystals, and since this type of crystal has anisotropy,
Required characteristics may not be obtained unless light with a specific polarization state is incident, and measures must be taken to deal with this.

Conventional technology For example, an optical waveguide is formed by thermally diffusing T1 into a waveguide substrate made of LiNbO2 (lithium niobate whose optical axis is perpendicular to the substrate surface), and an appropriate electrode is loaded on this optical waveguide. In the Matsuhatsu Enda optical modulator, the phase change per unit electric field is the largest for TM light, which has a plane of polarization (plane of vibration of the electric field vector) perpendicular to the substrate surface. so that
It enables low voltage drive. In this case, the incident light has TE
If a component of light (light having a plane of polarization parallel to the substrate surface) is included, the required modulation operation will not be performed because the phase change per unit electric field for TE light is smaller than that for TM light.

Specifically, when the output light is turned on and off in light intensity modulation, the TE light leaks out when it should be turned off, resulting in a significant deterioration of the extinction ratio.

The present invention was created in view of these circumstances, and an object of the present invention is to realize an optical waveguide device with good characteristics such as extinction ratio. “It is also an object of the present invention to provide an optical waveguide type polarizer to achieve this object.It is also an object of the present invention to provide a method for manufacturing the above-mentioned optical waveguide device.

Means for Solving the Problems FIG. 1 is a sectional view showing the structure of an optical waveguide type polarizer of the present invention.

The optical waveguide type polarizer of the present invention is constructed by forming an optical waveguide 2 having a higher refractive index than the substrate on a waveguide substrate l, and forming metal layers 3 on both sides of this optical waveguide 2.

The optical waveguide device of the present invention is configured such that the optical waveguide type polarizer is integrally provided in the optical input section.

Preferably, the waveguide substrate is Z force y)LiNb03-5
=, and the optical waveguide is Z-cut L r N b O3 and T
] is thermally diffused, and the metal layer is T1 silicide.

As shown in FIG. 2, the method for manufacturing an optical waveguide device of the present invention includes two steps: (1) forming grooves on both sides of a portion of a waveguide substrate made of LiNbO2 where an optical waveguide is to be formed; 11, and a second filling 81 into the groove.
a third step 13 of forming a T1 film on the Si and a portion of the waveguide substrate where an optical waveguide is to be formed; and a fourth step 14 of thermally diffusing the T1 film. Contains.

Function In the optical waveguide type polarizer of the present invention, since metal layers are formed on both sides of the optical waveguide, the complex refractive index of the metal layer produces an absorption effect on TE light. Therefore, when light having a TE light component and a TM light component is incident on this optical waveguide type polarizer, the output light is only the TM light.

In an optical waveguide device in which the optical waveguide type polarizer is integrally provided in the optical input part, the TE light is removed at the optical input part, so the functional part of the optical waveguide device can be used regardless of the polarization state of the incident light. The light that propagates is only TM light. If the waveguide substrate is made of LiNbO2, T”
Since the required characteristics are obtained when the M light propagates, when the present invention is applied to such an optical waveguide device, the light can be transmitted to the optical waveguide device using a normal ngle mode fiber. injection can be performed. However, in this case, since the TE acid component does not propagate, the loss increases by up to 3d1.Also, when using a polarization-maintaining fiber, the adjustment accuracy of the polarization direction becomes loose, so it is necessary to simplify the adjustment work. I can do it.

Example The present invention will now be described in detail.

FIG. 3 is an explanatory diagram of the manufacturing process of an optical waveguide device showing an embodiment of the present invention. First, as shown in FIG. 3(a), a waveguide substrate 1 made of Z-cut L, IN b O3
Grooves 21 are formed, for example, by etching, on both sides of the portion where the optical waveguide is to be formed. Next, as shown in FIG. 3(b), the groove 21 is filled with Si by forming an S1 film 22 on the waveguide substrate 1- by sputtering or the like. Thereafter, as shown in FIG. 3(C), the S1 film 22 is polished or etched to form the grooves 21.
The surface of the 5122 filled in the waveguide substrate 1 and the surface of the waveguide substrate 1 are made to be exposed on the same plane -11. Thereafter, as shown in FIG. 3(C), a '1'l film 23 is formed on the 5122-F and the portion of the waveguide substrate 1 where the optical waveguide is to be formed, by, for example, a lift-off method. Then, the Ti film 23 is thermally diffused by placing this waveguide substrate in a heating furnace, etc., and 5122 is made into the metal layer 3 made of Ti silicide, and the optical waveguide 2 has a high refractive index due to the thermal diffusion of T1. form. Next, after removing the residue 1゛], as shown in FIG. 3(f), a Hanwha layer 24 made of 5102 and serving as a ground layer is formed. Finally, as shown in FIG. 3(g), an electrode 25 is formed on the buffer layer 24'' as required.

According to the method of this embodiment, the formation of the metal layer 3 and the formation of the optical waveguide 2 can be performed simultaneously in the same process, so it is easy to realize the optical waveguide type polarizer of the present invention. T】
Since silicide has metallic properties, it can absorb the TE light component of the light propagating through the optical waveguide 2 due to its complex refractive index.

FIG. 4 is a plan view of a Matsuhatsu Enda type optical modulator manufactured by applying the above manufacturing method. Note that the illustration of the Matsuha layer interposed between the waveguide substrate and the electrode is omitted. This Matsuhatsu Enda type optical modulator uses the Z cuff surface of a waveguide substrate 1 made of L i N b 03 and forms an optical waveguide 2 by thermally diffusing ]l on this surface as described above. It is constructed by loading an electrode 25 onto an optical waveguide. 1 is a waveguide substrate, 2A is an input end optical waveguide, 2B,
2C is an optical waveguide that branches into two paths from the input optical waveguide 2Δ, 2D is an output optical waveguide where optical waveguides 2B and 2C join, 25A is a traveling wave electrode mainly loaded on the optical waveguide 2B, and 25B is an optical waveguide. This is the ground electrode loaded on 2C. The earth electrode 25B is grounded, and the output side optical waveguide 2D of the earth electrode 25B and the traveling wave electrode 25A
A terminating resistor 31 is connected to the end closer to . The driving voltage is supplied to the side of the ground electrode 25B and the traveling wave electrode 25A where the terminating resistor 3 is not provided. and,
Metal layers 3 made of T i silicide are provided on both sides of the passenger-side optical waveguide 2A.

FIG. 5 is a diagram showing the operating characteristics of the Matsubatsu Endach'1 optical modulator shown in FIG. 4, with the vertical axis representing the optical output intensity and the horizontal axis representing the driving voltage. In this embodiment, since 1'EE light is removed in the input end optical waveguide 2A, the light propagating through the functional part becomes '1'M light.

The solid line curve in FIG. 5 is a graph showing the relationship between optical output intensity and drive voltage for TM light. For reference, the relationship between the optical output intensity and the driving voltage when the TE light propagates in the case where the metal layer 3 is not provided is shown by a broken line. For the modulation signal, when turning on/off the upstream "f' M light = 10-, a modulation signal having an amplitude given by, for example, V. is used. In this example, T
Since the E light component is well removed, when the Matsuhatsu Enda optical modulator is operated under these conditions, an extremely high extinction ratio can be obtained. In the case of the conventional technology, since the metal layer 3 is not provided, in order to ensure that only TM light propagates, a polarization-maintaining optical fiber or the like is used to make the incident light TM light. Ta. In this case, extremely high precision alignment was required when connecting the polarization preserving optical fiber and the input section of the Matsuhatsu Enda optical modulator. On the other hand, in the case of this embodiment, if the polarization state of the incident light is set to approximately TM light, even if a slight TE light component occurs, this TE light component will be absorbed by the metal layer 3. It is absorbed and removed without deteriorating the extinction ratio. In this way, according to this embodiment, it is possible to provide a Matsuhatsu Enda type optical modulator that does not require highly accurate alignment and has good extinction ratio characteristics.

As described in detail, the present invention has the advantage of making it possible to realize an optical waveguide device with good characteristics such as extinction ratio.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the configuration of an optical waveguide type polarizer of the present invention, FIG. 2 is a step diagram showing a method for manufacturing an optical waveguide device of the present invention, and FIG. FIG. 4 is a plan view of a Matsuhatsu Enda type optical modulator manufactured by applying the manufacturing method shown in FIG. 3, and FIG. FIG. 3 is a diagram showing operating characteristics of a modulator. 1... Waveguide substrate, 2... Optical waveguide, 3... Metal layer.

Claims (1)

[Claims] 1. An optical waveguide (2) having a higher refractive index than the substrate is formed on a waveguide substrate (1), and metal layers (3) are formed on both sides of the optical waveguide (2). An optical waveguide type polarizer featuring: 2. An optical waveguide device, characterized in that the optical waveguide type polarizer according to claim 1 is integrally provided in an optical input section. 3. The optical waveguide device according to claim 2, wherein the waveguide substrate (1) is made of Z-cut LiNbO_3, and the optical waveguide (2) is made of Z-cut LiNbO_3.
An optical waveguide device, characterized in that the metal layer (3) is Ti silicide. 4. A first step (11) of forming grooves on both sides of the portion where an optical waveguide is to be formed in a waveguide substrate made of Z-cut LiNbO_3; and a second step (12) of filling the grooves with Si; The S
a third step (13) of forming a Ti film on the i and a portion of the waveguide substrate where an optical waveguide is to be formed; and a fourth step (14) of thermally diffusing the Ti film. A method for manufacturing an optical waveguide device, characterized in that: