Wavelength Tunable Semiconductor Laser with Dual Fabry-Perot Reflectors
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Solution Overview
Problem
Traditional tunable semiconductor lasers face challenges such as fabrication issues, broad spectrum emission characteristics, and cost structure limitations, making them unsuitable for all optical communication applications, particularly in coherent systems.
Innovation Solution
A wavelength tunable semiconductor laser design incorporating two Fabry-Perot Resonant Optical Reflectors (FP-RORs) with adjustable round trip optical path lengths and an optical phase adjusting element, allowing for precise tuning of resonant wavelengths and emission linewidths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If DBR based tunable lasers are used, then the laser is compact in size, but the emission spectrum becomes broad which prevents use in coherent communication systems
Solution Approach 1:
The laser cavity is segmented into multiple sections with different grating structures. Each grating section has a specific pitch that reflects a particular wavelength range, allowing the overall device to achieve narrow linewidth emission at a specific wavelength while maintaining a compact form factor. The segmentation of the cavity into regions with different optical properties enables precise wavelength selection.
Solution Approach 2:
Different regions of the laser cavity are assigned different local optical characteristics through varying grating pitches. The first grating has a first pitch optimized for reflecting a first wavelength, while the second grating has a second pitch optimized for a second wavelength. This local differentiation of optical properties enables the laser to achieve narrow emission linewidth at the desired wavelength while maintaining compact dimensions.
2Manufacturing precision
If external-cavity tunable lasers are used, then the emission linewidth is narrow suitable for coherent systems, but the device becomes complex to fabricate and use
Solution Approach 1:
The invention merges the gain medium and the wavelength-selective grating structures into a single integrated semiconductor device. The gratings are formed directly within the laser cavity using epitaxial growth techniques, eliminating the need for separate external cavity components. This integration maintains the narrow linewidth benefits of external-cavity designs while dramatically simplifying fabrication and improving long-term stability.
Solution Approach 2:
The laser device is designed with multi-functionality to serve both direct detection and coherent communication systems. By incorporating tunable grating structures that can be adjusted during fabrication or operation, the same device architecture can achieve narrow linewidth emission for coherent systems while maintaining the compact form factor needed for various applications, making it universally applicable.
3Adaptability or versatility
If traditional tunable lasers are used, then wavelength tuning capability is available, but fabrication issues and cost structure challenges limit broad use
Solution Approach 1:
The laser incorporates dynamically adjustable grating structures where the pitch or orientation of the gratings can be modified during fabrication or operation. This dynamic capability allows the laser to be tuned to different wavelengths by changing the grating parameters, providing wavelength tuning versatility while using standard semiconductor fabrication processes that maintain ease of manufacture and cost-effectiveness.
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 design enables flexible wavelength tuning and narrow emission linewidths, enhancing the laser's suitability for both direct detection and coherent communication systems while addressing fabrication and cost challenges.
Implementation Method 1
a first resonant optical reflector (ROR) where the light is reflected back and forth
Implementation Method 2
a portion of light is evanescently coupled back into the optical waveguide
Implementation Method 3
an optical phase adjusting element, allowing for precise tuning of resonant wavelengths
Data Source
AI summary
A tunable semiconductor laser incorporates a light generating structure in which light is generated and amplified by stimulated emission. The generated light is evanescently coupled into a first resonator of a first resonant optical reflector where the light is reflected back and forth between two end mirrors. A portion of this light, which is characterized by a series of resonant wavelengths, is evanescently coupled back into the light generating structure. One or more of the resonant wavelengths can be changed by modifying an optical path length of the first resonator. The tunable semiconductor laser further includes a second resonant optical reflector having a second resonator. The second resonator interacts with the light generating structure in a manner similar to the first resonator. A desired beat wavelength can be obtained by modifying the optical path length in one or both resonators.