Traveling-Wave Optical Waveguide Layout for Flatter Frequency Response
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Solution Overview
Problem
Existing optical waveguide elements face challenges in improving frequency characteristics at low cost, particularly in substrates with various crystal orientations, due to limitations in designing polarization direction and increased manufacturing costs associated with substrate tilting and electrode separation.
Innovation Solution
The optical waveguide element features a traveling-wave electrode with a modulation section configured such that the phase change in the first modulation section has an opposite sign to that in the second modulation section, with the first section being shorter than the second, and includes a U-turn waveguide to invert light propagation direction, allowing for improved frequency characteristics without requiring complex substrate adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the polarization direction of the substrate is adjusted by tilting the substrate between parallel plate electrodes, then frequency response characteristics are flattened, but the separation distance between electrodes must be widened and manufacturing complexity increases
Solution Approach 1:
The patent extracts the polarization adjustment function from the substrate itself and transfers it to a separate flattening means (optical element or waveguide structure). This allows the substrate to remain in its original orientation while still achieving frequency response flattening, eliminating the need for substrate tilting and increased electrode separation.
Solution Approach 2:
The patent introduces a flattening means as an intermediary element between the substrate and the optical waveguide. This intermediary component performs the polarization adjustment function, allowing the substrate to maintain its original orientation while still achieving the desired frequency response characteristics.
2Speed
If a traveling-wave electrode is used for broadband optical modulation, then high frequency characteristics are improved, but propagation loss increases and limits the operation frequency band
Solution Approach 1:
The patent changes the electrical parameters (impedance, dimensions, spacing) of the traveling-wave electrode to optimize the balance between high-frequency performance and propagation loss. By adjusting these parameters, the electrode can operate effectively at higher frequencies while minimizing energy loss.
3Productivity
If the operation frequency is increased to improve transmission capacity, then bandwidth is widened, but drive voltage increases and response sensitivity decreases
Solution Approach 1:
The patent changes the electrical and geometric parameters of the optical modulation element to optimize performance at higher frequencies. By adjusting parameters such as electrode spacing, waveguide dimensions, and material properties, the element can operate at higher frequencies with reduced drive voltage requirements.
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 enhances frequency response by up to 2 dB, widens the operation frequency band, and allows for cost-effective improvements in frequency characteristics across different crystal orientations without increasing manufacturing complexity.
Implementation Method 1
an optical modulation element using a lithium niobate (LiNbO3) (hereinafter, also referred to as LN) crystal having an electro-optic effect as a substrate
Data Source
AI summary
An optical waveguide element includes a substrate, an optical waveguide disposed inside the substrate or on the substrate, and an electrode provided along the optical waveguide, working on the optical waveguide to generate a phase change in a light wave propagating through the optical waveguide. The electrode is a traveling-wave electrode. In a modulation section where the light wave is controlled by the electrode, the electrode and the optical waveguide are configured so that the phase change generated in a first modulation section located within a predetermined distance range from a downstream side end portion along a propagation direction of a traveling wave of an electrical signal propagating through the electrode has a sign opposite to a sign of the phase change generated in a second modulation section located within a predetermined distance range from an input end of the electrical signal on an upstream side along the propagation direction.