Optical Circuit With Half-Length Waveguide for Modulator Error Inspection
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Solution Overview
Problem
Existing silicon photonics optical circuits face challenges in accurately inspecting manufacturing errors in modulators, leading to increased chip area and complex inspection processes, particularly due to the difficulty in reproducing characteristic degradation in modulators with manufacturing errors.
Innovation Solution
An optical circuit with a Mach-Zehnder interferometer type modulator and an inspection circuit using test light to accurately reflect manufacturing errors in modulators, incorporating a rectangular waveguide and optical branch for splitting and propagating light beams in opposite directions, allowing for downsized inspection without requiring electric signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If circuit elements for inspection are integrated in addition to the main circuit, then inspection capability is improved, but chip area increases
Solution Approach 1:
The patent creates a simplified copy of the modulator circuit called an 'equivalent circuit' that reproduces the essential characteristics of the main modulator without including all its components. This equivalent circuit contains only the critical elements needed for inspection, thereby reducing the chip area required for inspection functionality while maintaining inspection capability.
Solution Approach 2:
The patent extracts only the essential inspection-related components from the full modulator circuit to create a dedicated inspection circuit. By taking out only the necessary elements (the equivalent circuit) and separating them from the main modulator, the patent reduces the overall chip area while preserving the ability to inspect manufacturing errors.
2Area of stationary object
If the modulator area is reduced for downsizing, then chip area is reduced, but the ability to accurately reproduce manufacturing error characteristics deteriorates
Solution Approach 1:
The patent applies local quality by concentrating the inspection functionality in a specific localized region (the equivalent circuit) with precisely configured components. The equivalent circuit is designed with specific PN junction configurations that locally reproduce the characteristic degradation patterns of manufacturing errors, ensuring accurate inspection without requiring the full modulator area.
Solution Approach 2:
The patent changes the parameters of the inspection circuit by creating an equivalent circuit with modified but representative characteristics. The equivalent circuit uses PN junctions configured to reproduce the electrical and optical characteristics of the main modulator under various manufacturing error conditions, allowing accurate inspection with reduced area through parameter optimization rather than full-scale replication.
3Measurement precision
If both light and electric signals are used for inspection, then inspection comprehensiveness is improved, but inspection complexity and cost increase
Solution Approach 1:
The patent substitutes the complex dual-signal inspection system with an optimized electrical inspection approach using the equivalent circuit. By replacing the need for simultaneous light and electric signal inspection with an electrical measurement system that uses the equivalent circuit's PN junctions, the patent reduces inspection complexity and device cost while maintaining the ability to detect manufacturing errors through electrical characteristic measurements.
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
The solution enables accurate estimation of modulator characteristics while reducing chip size and simplifying the inspection process by using only test light, thus improving inspection efficiency and reducing costs.
Implementation Method 1
an optical branch for splitting the test light to two branch light beams having equal intensity and propagating the two branch light beams to the inspection waveguide in opposite directions to each other
Implementation Method 2
a refractive index of Si is very large, and thus, confinement of light is strong
Implementation Method 3
a Mach-Zehnder interferometer type modulator including two arm waveguides in which a PN junction is formed in a cross section
Data Source
AI summary
An inspection circuit that accurately reflects influence of a manufacturing error generated in a modulator of a main circuit in manufacturing process of an optical circuit, and at the same time, achieves downsizing, is disclosed. The inspection circuit includes an inspection waveguide having a length of half of a length of an arm waveguide of the main circuit and is configured such that test light propagates in two directions on the inspection waveguide, thereby implementing reproduction of characteristics equivalent to those of the modulator of the main circuit. In order to propagate the test light in two directions of the inspection waveguide in the inspection circuit, a loop-shaped path configured between branch ports of the optical branches is utilized. Embodiments of different configurations are disclosed in accordance with aspects where two branch light beams of the test light are guided to the inspection waveguide.