JPS6242116A - Optical modulator - Google Patents

Abstract

PURPOSE:To supply an electric modulated signal of ultra high frequency to an electrode efficiently by coupling a semiridged cable electrically with a slot resonator provided to an optical waveguide intersection part, and supplying an electric signal of resonance frequency from this cable and generating a resonance voltage at a resonator. CONSTITUTION:The slot resonator 21 formed by removing part of a metallic conductor 20 is constituted above the intersection part of crossing optical waveguides, and the center conductor 23 of the semiridged cable is connected electrically. Namely, the center conductor 23 of the semiridged cable is connected to the metallic conductor 20 while crossing the slot resonator 21 and the external conductor 22 of the semiridged cable is connected to the metallic conductor 20. When the length of the slot resonator 21 is set, for example, a half as long as wavelength, a standing wave voltage pattern is generated so that an electric field becomes maximum in the center of the slot resonator during resonance and is zero at both ends, thereby performing optical switching or optical modulating with its voltage similarly to conventional examples.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical modulator for electrically controlling the intensity of guided light waves in optical integrated circuits.

BACKGROUND OF THE INVENTION A conventional example of an optical modulator using crossed optical waveguides is shown in FIG. Optical waveguides 2,
It is created so that 3 intersect.

Electrodes 8 and 9 are provided at the intersections of these optical waveguides, and these electrodes are also connected to electrode pads 10 and 11 at the ends of the substrate.
A voltage from a signal source 13 is applied through a resistor 12 between these electrode pads 10.11 (for example, Applied Optics Vol. 18). No. 3296-
3300 (1979)) It is well known that an element having such a structure operates as an optical switch or an optical modulator.

That is, for example, when light is incident from the terminal 4, the light travels straight toward the terminal 5 when no voltage is applied from the outside. On the other hand, when a voltage is applied from the outside, the electric field generated between the electrodes 8 and 9 causes a change in the refractive index based on the electro-optic effect at the intersection of the optical waveguides, and the light incident from the terminal 4 is directed toward the terminal 7. It starts to come out. Therefore, optical switching becomes possible.

Further, when focusing on the output light from the terminal 5, intensity-modulated light is extracted, and it can also be used as an optical modulator.

Problems to be Solved by the Invention High-frequency electrical signals are usually supplied using coaxial cables, but with this electrode configuration, it is difficult to connect to the coaxial cable, and even if it is connected, the electrode pad and coaxial cable may be connected. An impedance mismatch occurs between the electrodes, and the power of the external switching signal is not efficiently supplied to the electrode section. In addition, with such an electrode configuration, the input impedance seen from the power source is the sum of the load resistor 12 and the capacitance between the electrodes 8 and 9 in parallel, and as the frequency of the switching electrical signal increases, the input impedance increases due to this capacitance. The impedance mismatch with the power supply becomes large, making switching operations difficult at high frequencies.

Means to Solve the Problems In order to solve the above problems, the present invention provides a slot resonator at the intersection of the optical waveguides of the optical modulator, and connects a semi-ridged cable to the slot resonator! An electrical signal having a frequency equal to the resonant frequency of the slot resonator is supplied from the semi-ridged cable to generate a resonant voltage in the slot resonator, thereby performing optical modulation.

Effect of the Invention With the above-described configuration, the present invention can supply a high-frequency electric signal from the semi-ridged cable, and can efficiently utilize the standing wave voltage generated by resonating the slot resonator as a modulation voltage. Ultra high-speed modulation as described above is also possible.

Embodiment An embodiment of the present invention is shown in FIG. The person in FIG. 1 is a top view, and B in FIG. 1 is a sectional view taken along the line A--A in the person in FIG. In FIGS. 1 and 1B, 14 is a substrate made of a substance having an electro-optic effect, and 15 and 16 are intersecting optical waveguides formed near the surface of the substrate 14. A slot resonator 21 is constructed by removing a portion of the metal conductor 20 above the intersection of the crossed optical waveguides. This slot resonator 21
A center conductor 23 of the semi-ridged cable is electrically connected to the center conductor 23 of the semi-ridged cable. This connection is made by connecting the center conductor 23 of the semi-ridged cable to the metal conductor 20 across the slot resonator 21, and by connecting the outer conductor 22 of the semi-ridged cable to the metal conductor 20. For example, if the length of the slot resonator 21 is selected to be an ex wavelength, a standing wave voltage pattern will be generated in which the electric field is maximum at the center of the slot resonator during resonance and zero at both ends, and this voltage will cause Light switching or light modulation will be performed in a similar manner.

Effects of the Invention The present invention uses a slot resonator as an electrode of an optical modulator, connects a semi-ridged cable to the slot resonator, and supplies a modulated electrical signal from the semi-ridged cable, so that the connection is easy. Ultra-high frequency modulated electrical signals can be efficiently supplied to the electrodes without reflection due to discontinuities. In addition, in the present invention, since the resonant standing wave voltage of the slot resonator is used as the modulation voltage, there is no modulation restriction due to mismatch between the phase velocity of the electrical signal and the phase velocity of the light wave, and it is possible to operate at frequencies of several tens of GHz or more. Ultra high-speed modulation becomes possible.

[Brief explanation of the drawing]

FIGS. 1A and 1B are top views of an optical modulator according to an embodiment of the present invention;
FIG. 2 is a basic configuration diagram of a conventional optical modulator. 14... Substrate made of a substance having an electro-optic effect, 20... Slot resonator grounding conductor, 21...
... Slot resonator, 22 ... Semi-ridged 9 cable outer g lead L 23 ... Semi-ridged
Cable center conductor. Name of agent: Patent attorney Toshio Nakao and 1 other person15
, 16--Ikko/I light guiding lacrimal tract 17--Mitsuto/! ｊ蚦子18- 光逢池±Kananako 2nd figure

Claims (1)

[Claims] A slot resonator is provided above the intersection of crossed optical waveguides made near the surface of a substrate made of a substance having an electro-optic effect, a semi-ridged cable is electrically coupled to the slot resonator, and the semi-ridged cable is electrically coupled to the slot resonator. An optical modulator characterized in that an electrical signal having a frequency equal to the resonant frequency of the slot resonator is supplied from a cable.