Optical Modulator Waveguide Groove and Expanded Electrode Design
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Solution Overview
Problem
Optical modulators face challenges in reducing size while maintaining low DC bias control voltage and preventing radiation loss due to the need for long electrodes and high-frequency signal integrity, which is compromised by the proximity of RF and DC electrodes and variations in manufacturing processes.
Innovation Solution
The optical modulator design features a substrate with optical waveguides bent by 180 degrees, grooves along the outer curve to reduce radiation loss, and signal electrodes with expanded cross-sectional areas at intersections with grooves to prevent disconnection and maintain impedance stability, allowing for compact size and reliable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the radius of curvature of the bending waveguides is decreased to reduce chip size, then the chip size is reduced, but the radiation loss of light increases
Solution Approach 1:
A low-refractive-index part (intermediary structure) is introduced between the bending waveguide and the substrate. This intermediary structure prevents light from escaping toward the outer curve of the bending waveguide, thereby reducing radiation loss while allowing the waveguide to be bent with a smaller radius of curvature for chip size reduction
Solution Approach 2:
The low-refractive-index part is specifically positioned only at the outer curve of the bending waveguide where light escape occurs. This localized modification addresses the radiation loss problem only where needed, without affecting other parts of the waveguide structure
2Length of stationary object
If the DC input terminals and RF input terminals are arranged on the same side to reduce package length, then the package length is reduced, but crosstalk between DC signals and RF signals occurs
Solution Approach 1:
A ground terminal is introduced as an intermediary element between the DC input terminal and RF input terminal. This ground terminal acts as a shielding barrier that prevents crosstalk between the DC and RF signals while allowing both input terminals to be arranged on the same side of the package for compactness
3Device complexity
If the space between DC electrodes and turn-back part is reduced to accommodate RF electrodes, then the electrode layout is optimized, but the DC electrode length becomes short causing increased DC control voltage level
Solution Approach 1:
The electrode layout is optimized by utilizing the spatial arrangement in multiple dimensions. The DC electrodes are extended along the optical waveguide path, and the RF electrodes are positioned in a different spatial plane, allowing both electrode types to coexist without excessive spacing requirements while maintaining adequate DC electrode length
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration achieves a compact optical modulator with reduced radiation loss and stable high-frequency signal transmission, maintaining low DC bias control voltage and ensuring high production yield by preventing electrical disconnection and impedance variations.
Implementation Method 1
an optical waveguide pair provided in the substrate and configured to form a Mach-Zehnder interferometer
Implementation Method 2
a groove provided along the optical waveguide pair in the bending part
Implementation Method 3
a signal electrode that applies a high- frequency electrical signal to the optical waveguide pair
Data Source
AI summary
An optical modulator has an optical input port and an optical output port provided on a same end of a substrate; an optical waveguide pair formed in the substrate and configured to form a Mach-Zehnder interferometer, one end of the optical waveguide pair being connected to the optical input port and the other end of the optical waveguide pair being connected to the optical output port, the optical waveguide pair having a bending part; a groove provided along the optical waveguide pair in the bending part; and a signal electrode that applies a high-frequency electrical signal to the optical waveguide pair, wherein the signal electrode has an expanded section having an increased cross sectional area at a section intersecting the groove.