Laser Cavity Partial Return Device Mode Hopping Reduction
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Solution Overview
Problem
Lasers in optical communications systems face mode hopping issues due to changes in the index of refraction caused by temperature and electrical current variations, leading to undesirable wavelength changes in the light signal output, which complicates the device design and increases costs with the need for temperature control and feedback control devices.
Innovation Solution
A laser cavity with a partial return device, such as a Bragg grating, is configured to reflect different wavelengths at varying intensities, providing a broader reflection profile that redistributes power among multiple modes instead of hopping between two modes, thereby reducing the impact of refractive index changes and eliminating the need for additional control devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a narrow reflection range grating is used to limit laser output to a single wavelength, then wavelength precision is improved, but mode hopping occurs when refractive index changes due to temperature or current variations
Solution Approach 1:
The patent changes the parameter of the reflection profile from narrow to broad by configuring the partial return device to reflect multiple wavelengths with different intensities. This allows the laser to maintain stable operation across temperature and current variations without mode hopping, as the broader reflection range accommodates refractive index changes while the intensity distribution maintains a preferred operating mode.
2Reliability
If temperature control devices and feedback control devices are added to stabilize refractive index, then mode hopping is reduced, but device complexity and cost increase
Solution Approach 1:
The patent extracts the need for external temperature control and feedback control devices by incorporating the mode stabilization function directly into the partial return device's reflection profile. The broad reflection profile with specific intensity distributions inherently compensates for refractive index changes, eliminating the requirement for separate control systems.
Solution Approach 2:
The partial return device with a broad reflection profile provides self-stabilization of the laser mode. The intensity distribution across multiple wavelengths automatically adjusts to maintain stable operation under varying temperature and current conditions, making the system self-regulating without external control mechanisms.
3Reliability
If a broad reflection profile is used to reduce mode hopping, then mode stability is improved, but wavelength precision may be compromised
Solution Approach 1:
The patent applies local quality by creating a non-uniform intensity distribution within the broad reflection profile. Specific wavelengths are reflected with higher intensities while others are reflected with lower intensities, allowing the system to maintain a preferred operating mode with precise effective wavelength while still benefiting from the broad overall reflection range that prevents mode hopping.
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 stabilizes the average wavelength of the output light signal, reducing its responsiveness to external effects like temperature and current changes, thus minimizing mode hopping and eliminating the requirement for temperature control devices and feedback control systems.
Implementation Method 1
The partial return device reflects different wavelengths of the laser light signal at different intensities
Implementation Method 2
A laser cavity with a partial return device, such as a Bragg grating, is configured to reflect different wavelengths at varying intensities
Data Source
AI summary
The laser cavity is positioned on a substrate and includes a cavity waveguide guiding a laser light signal between a gain medium and a partial return device. The partial return device receives the laser light signal from the cavity waveguide and returns a first portion of the laser light signal to the cavity waveguide. The partial return device transmits a second portion of the laser light signal to an output waveguide. The partial return device reflects different wavelengths of the laser light signal at different intensities. Additionally, the partial return device is configured such that when the most intense wavelength of the laser light signal reflected by the partial return device is the same as a wavelength of one of modes of the laser light signal, the mode with the next longest wavelength and the mode with the next shortest wavelength are each reflected by the partial return device at an intensity greater than 80% of the intensity of the most intensely reflected wavelength.