RU187990U1 - OPTICAL MODULATOR - Google Patents

Abstract

The utility model relates to integrated optics devices. The integrated optical modulator comprises sequentially formed first plate, second plate, buffer layer and three electrodes. The second plate is made of a crystal having an electro-optical effect. A waveguide is made in the second plate. The first plate is made of a material that absorbs electromagnetic radiation in the microwave region. The thickness d of the second plate is in the range from 0.5 mm inclusive to 1 mm inclusive. The technical result consists in providing mechanical strength and uniformity of the second plate and in simplifying the manufacturing technology of the modulator. 5 cp f-ly, 2 ill.

Description

This utility model relates to integrated optics devices such as waveguide channels, splitters, polarizers and light modulators located on a single substrate.

Integrated-optical modulators based on lithium niobate are the key components of fiber-optic transmission lines for digital and analog signals, transmitters. Due to the high modulation rates, such modulators are widely used in areas such as high-speed optical networks, photonic analog-to-digital converters, photon communication lines, and other microwave photonics systems. In photonic lines, due to external modulation, the use of a broadband modulator is necessary to achieve a wide band. The amplitude-frequency characteristic of the modulator (AFC), as a rule, is determined by the mismatch of the speeds of the microwave traveling wave and the optical wave, as well as frequency-dependent losses in the electrodes. However, resonant phenomena often occur, causing a dip in the amplitude-frequency response of the modulator monotonically decreasing with the frequency of the curve until the -3 dB point is predicted from the values of the losses in the electrodes and the speed mismatch. These dips are sometimes a factor limiting the operating frequency band of the modulator. In this case, the dips are caused by resonant excitation of the substrate modes. There are broadband integrated optical-modulators in which the energy leakage to spurious modes is controlled by reducing the thickness of the crystalline substrate or replacing it with another material, but this worsens the mechanical strength of the substrate and complicates the modulator manufacturing technology.

Known integrated optical microwave modulator (see patent US 8135241, IPC G02F 1/035, G02B 6/10, published March 13, 2012), comprising a plate of an electro-optical crystal, a waveguide formed in the plate, three electrodes made on the surface plates for applying an electric field to the waveguide, a buffer layer and a volume of material with a low dielectric constant, recessed to avoid crossing with the waveguide into a plate from a crystal having an electro-optical effect.

The advantage of the well-known integrated optical modulator is to achieve smoothness of the amplitude-frequency characteristic. A disadvantage of the known integrated optical modulator is the fact that the introduction of a material with a different dielectric constant into the plate requires additional complex technological operations, the mechanical uniformity is lost, and the influence of temperature changes and other external factors is amplified accordingly.

The elimination of resonance peaks in the frequency response of the modulator is achieved by placing material with a low dielectric constant in the microwave range in the thickness of the crystal plate.

Known integrated optical modulator (see patent US 7068863, IPC G02F 1/035, G02F 1/295, G02B 6/10, published 06/27/2006), including sequentially formed the first reinforcing plate, the conductive layer, the second thin (for example, 10 μm) a plate of a crystal having an electro-optical effect, in which a waveguide is formed, and three electrodes.

The small thickness of the plate of the electro-optical material provides a high cutoff frequency (more than 40 GHz) for its resonance modes, and the conductive layer prevents the penetration of microwave radiation into the reinforcing plate and the excitation of its resonance modes.

The advantage of the known integrated optical modulator is to achieve smoothness of the amplitude-frequency characteristic due to the presence of a conductive layer. The structural strength is ensured by the use of a supporting structure. A disadvantage of the known integrated optical modulator is the need for complex technological operations for attaching a thin and brittle plate of electro-optical material to the reinforcing plate, as well as the need to select the material of the reinforcing plate with thermal expansion coefficients close to the plate of the electro-optical material and mechanical characteristics.

Known integrated optical modulator (see patent US 7856155, IPC G02F 1/035, G02B 26/00, published 12/21/2010), which coincides with this decision for the largest number of essential features and adopted for the prototype. The integrated optical modulator includes a series-formed first reinforcing plate, a second thin (20 μm or less) plate from an electro-optical crystal, a buffer layer and three electrodes. A waveguide is made in the second plate.

The smoothness of the amplitude-frequency characteristic (AFC) in the known integrated optical modulator is achieved due to the small (20 μm or less) thickness of the second plate, in which the optical radiation is modulated due to the electro-optical effect, which leads to the technological complexity of manufacturing the modulator, due to the need to create a thin (less than 20 microns) crystalline layer and ensuring its mechanical fastening to the first reinforcing plate without damage. In this case, the standard thickness of the second plate from the crystal having an electro-optical effect, providing sufficient mechanical strength for carrying out technological operations with it, is 0.5-1.0 mm.

The objective of this utility model is to develop such a design of an integrated optical modulator in which the frequency response is smooth, but a second plate of such a thickness is used that provides its mechanical strength and mechanical uniformity, which ultimately leads to a simplification of the modulator manufacturing technology.

The problem is solved in that the integrated optical modulator includes sequentially formed first plate, the second plate from the crystal having an electro-optical effect, a buffer layer and three electrodes. A waveguide is made in the second plate. The first plate is made of a material that absorbs electromagnetic radiation in the microwave region, and the thickness of the second plate d satisfies the ratio:

The smoothness of the amplitude-frequency characteristic (AFC) in this technical solution is achieved due to the fact that the first plate is made of a material that absorbs electromagnetic radiation in the microwave region, as a result of which the amount of energy going into spurious modes of oscillations at resonant frequencies decreases. A thickness d of the second plate of more than 0.5 mm provides its mechanical strength. The use of a second plate with a thickness of more than 1 mm is impractical, since this increases its cost, and also complicates the technical operations with it in the manufacture of optical waveguides and electrodes.

The first plate can be made of silicone rubber, urethane and neoprene with carbonyl iron introduced into them.

или

The optical waveguide formed in the second plate can be made in the form of a Mach-Zander interferometer containing

or

The present optical modulator is illustrated by drawings, where: in FIG. 1 shows a top view of the construction of an optical modulator; in FIG. 2 is a cross-sectional view of an optical modulator structure.

The present integrated optical modulator (see Fig. 1, Fig. 2) contains sequentially formed the first plate 1, the second plate 2 from the crystal having an electro-optical effect, in which a waveguide 3, a buffer layer 4 and three electrodes are made, one of which is a signal electrode 5, and two other ground electrodes 6. The first plate is made of a material that absorbs electromagnetic radiation in the microwave region, and the thickness d of the second plate satisfies the relation:

The first plate can be made of silicone rubber, urethane and neoprene with carbonyl iron introduced into them.

или

The optical waveguide formed in the second plate can be made in the form of a Mach-Zander interferometer containing

or

The present integrated optical modulator operates as follows. The optical radiation is introduced from the end into the optical waveguide 3. The mode propagating along the optical waveguide 3 is divided between parallel sections of the optical waveguide 3. The electromagnetic wave propagating in the waveguide formed by the electrodes 5, 6, the buffer layer 4 and the second plate 2 creates a field in the region of the optical waveguide 3, which due to the electro-optical effect creates a change in the refractive index of light in part of the optical waveguide 3. Optical radiation is output from the end of the waveguide 3. The smoothness of the frequency response of the modulator ostigaetsya follows. Due to the fact that the first plate 1 is made of a material that absorbs electromagnetic radiation in the microwave region, the Q factor of the cavity formed by the second plate 2 from the crystal having an electro-optical effect is reduced, as a result of which the amount of energy that goes into the parasitic vibration modes at resonant frequencies is reduced.

Example. An integrated optical modulator was made, which consisted of a successively formed first plate of silicone rubber with 0.7 mm thick carbonyl iron introduced into it, a second plate of lithium niobate crystal 1 mm thick, a buffer layer of silicon dioxide 1 μm thick, a signal electrode 13 microns in size and earth electrodes. The distance between the earth electrodes and the signal electrode was 14 μm. An optical waveguide in the form of a Mach-Zander interferometer containing Y-splitters with a mode diameter of 10 μm was formed in the second plate. In this case, the frequency response unevenness associated with the leakage of microwave radiation at resonant frequencies into the substrate did not exceed 0.3 dB.

Claims (7)

1. An integrated optical modulator comprising a first plate, a second plate of a crystal having an electro-optical effect, a buffer layer and three electrodes, and a waveguide is made in the second plate, characterized in that the first plate is made of a material that absorbs electromagnetic radiation in microwave region, and the thickness d of the second plate satisfies the relation: 0.5 mm≤d≤1 mm. 2. The modulator according to claim 1, characterized in that the first plate is made of silicone rubber with carbonyl iron introduced into it. 3. The modulator according to claim 1, characterized in that the first plate is made of urethane with carbonyl iron introduced into it. 4. The modulator according to claim 1, characterized in that the first plate is made of neoprene with carbonyl iron introduced into it. 5. The modulator according to claim 1, characterized in that the waveguide is made in the form of a Mach-Zander interferometer containing X-splitters. 6. The modulator according to claim 1, characterized in that the waveguide is made in the form of a Mach-Zander interferometer containing Y-splitters.

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