Wavelength-Tunable Optical Transmitter Collinear Waveguide Coupling
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Solution Overview
Problem
Wavelength-tunable optical transmitters using narrow gap mirrors face challenges in downsizing, fabrication yield, and reliability due to alignment issues, high processing accuracy requirements, and signal light scattering, which degrades modulation properties and complicates fabrication processes.
Innovation Solution
A wavelength-tunable optical transmitter design featuring collinearly coupled semiconductor optical waveguides with a reflection structure at the end face, allowing for adjustable reflectance and transmittance, eliminating the need for a narrow gap mirror and enabling monolithic integration of a wavelength-tunable light source and optical modulator, while simplifying fabrication and reducing scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a narrow gap mirror is used to couple the wavelength-tunable light source and optical modulator, then the devices can be monolithically integrated, but the device length increases and fabrication precision requirements become extremely high
Solution Approach 1:
The patent transitions from a one-dimensional longitudinal coupling approach (narrow gap mirror requiring direct alignment) to a two-dimensional coupling scheme using a lens to focus light from the light source end face to the modulator end face. This dimensional change allows for compact integration while maintaining reliable optical coupling without requiring extremely precise longitudinal alignment.
2Reliability
If a narrow gap mirror is used for coupling, then monolithic integration is achieved, but manufacturing precision requirements increase to about 0.1 μm
Solution Approach 1:
The patent introduces a lens as an intermediary optical element between the wavelength-tunable light source and the optical modulator. This lens mediates the optical coupling by focusing light from the light source end face to the modulator end face, eliminating the need for direct narrow gap coupling and the associated high precision etching requirements.
3Ease of manufacture
If a narrow gap mirror is used, then coupling is achieved, but signal light scattering occurs which degrades modulation properties
Solution Approach 1:
The patent addresses the scattering problem by using a lens to focus the optical signal, which converts the potentially harmful scattered light into a concentrated focused beam at the modulator end face. This approach transforms the scattering issue into a benefit by improving coupling efficiency while maintaining signal quality and modulation properties.
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 results in a downsized, reliable, and high-yield optical transmitter with improved modulation properties and reduced fabrication costs, as it allows for flexible positioning of components and eliminates the need for resin filling and precise etching, thereby enhancing the stability and efficiency of signal light coupling.
Implementation Method 1
A Mach-Zehnder (MZ) optical intensity modulator in which a couple of waveguide type optical phase modulators are embedded into an MZ interferometer
Implementation Method 2
A Mach-Zehnder (MZ) optical intensity modulator in which a couple of waveguide type optical phase modulators are embedded into an MZ interferometer
Implementation Method 3
a reflector having a wavelength-tunable mechanism and a reflector having small (or no) wavelength dependence are arranged at both ends of a gain region
Data Source
AI summary
A first exemplary aspect of the present invention is a wavelength-tunable optical transmitter including: a semiconductor substrate (101); a wavelength-tunable light source that is formed on the semiconductor substrate (101) and includes at least a first reflector (102) of a wavelength-tunable type and a gain region (104); a semiconductor optical modulator formed on the semiconductor substrate (101); a first semiconductor optical waveguide (105c) that is formed on the semiconductor substrate (101) and smoothly connected to the wavelength-tunable light source; a second semiconductor optical waveguide (105d) that is formed on the semiconductor substrate and smoothly connected to the semiconductor optical modulator; a waveguide coupling region (108) in which the first and second semiconductor optical waveguides are collinearly coupled with a length LC that is not equal to m/2 (m: integer) times a complete coupling length LC0; and a second reflector (113) formed at an end of the waveguide coupling region (108).