Coupled-Cavity Semiconductor Laser With Vernier Wavelength Tuning
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Solution Overview
Problem
Conventional single mode semiconductor lasers have limited tuning ratios and complex characterization processes, making it difficult to achieve wide tuning ranges and mass production due to the need for multiple control parameters and high-dimensional parameter spaces.
Innovation Solution
A widely tunable single mode semiconductor laser with a monolithic structure featuring two linearly-aligned ridge waveguides and individually controllable heating currents, using the Vernier tuning principle to simplify the characterization process by reducing the number of required tuning parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wavelength selection mechanisms (DFB gratings, DBR structures) are used to achieve single mode operation, then side mode suppression ratio is improved, but tuning ratio is limited to approximately 0.01 or less
Solution Approach 1:
The laser is divided into multiple gain sections (first gain section, second gain section, third gain section) with different gain materials. Each section can be independently controlled through separate current injection, enabling wavelength tuning across a wide range while maintaining single mode operation. The segmentation allows different parts of the laser to contribute to different wavelength ranges, achieving both high side mode suppression and wide tuning ratio.
2Adaptability or versatility
If multi-segment lasers are used to expand tuning range by adjusting effective refractive index, then tuning ratio is improved, but fabrication and characterization complexities increase significantly
Solution Approach 1:
Different gain sections are designed with locally optimized properties: the first gain section uses a first gain material optimized for a specific wavelength range, the second gain section uses a second gain material for another range, and the third gain section uses a third gain material for a third range. This local quality approach allows each section to be independently characterized and controlled, reducing the overall system complexity compared to uniformly designed multi-segment lasers.
Solution Approach 2:
The invention changes the material composition parameter across different gain sections rather than relying solely on geometric or structural variations. By using different gain materials with distinct emission characteristics, the laser achieves wide tuning capability through material properties rather than complex structural adjustments, simplifying both fabrication and characterization processes.
3Adaptability or versatility
If Vernier tuning of coupled cavities is used to achieve wider tuning range, then tuning ratio is improved, but the number of control parameters increases leading to complex characterization
Solution Approach 1:
The multiple gain sections serve multiple functions simultaneously: they provide gain for different wavelength ranges, act as wavelength selection mechanisms through their material properties, and enable independent current control for tuning. This multi-functionality reduces the need for separate control mechanisms, thereby reducing the effective number of control parameters despite the multi-section structure.
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 a tuning ratio of approximately 0.1 or more, allowing for simultaneous control of wavelength and light intensity with high side mode suppression ratios, facilitating mass production and integration into photonic integrated circuits.
Implementation Method 1
control the wavelength selection mechanism. For many applications it is highly desirable to have a fully electronic wavelength selection mechanism. These fully electronic wavelength selection mechanisms are typically based on a tuning of the refractive index of the laser's waveguide material using variations of (i) the temperature of the waveguide material
Implementation Method 2
tuning of the refractive index of the laser's waveguide material using variations of (i) the temperature of the waveguide material, and (ii) the density of the injected current
Implementation Method 3
A different approach to wavelength selection uses the Vernier effect. In this approach, one typically defines two cavities, each possessing its own Fabry-Perot wavelength comb. Tuning is then achieved by manipulating the refractive index of the two cavities individually
Implementation Method 4
single mode emission semiconductor lasers provide light sources for many modern applications
Data Source
AI summary
The present invention provides a widely tunable, single mode emission semiconductor laser which comprises a semiconductor substrate, a first linear ridge waveguide which forms a first coupled cavity, and a second linear ridge waveguide which forms a second coupled cavity, with the first coupled cavity being separated from the second coupled cavity by a gap. The first and second coupled cavities comprise p-contacts and n-contacts for allowing laser currents I1, I2 to be injected into the first and second coupled cavities, respectively. The first and second coupled cavities comprise first and second heating resistors, respectively, for heating the first and second coupled cavities when heating currents H1, H2 are applied to the first and second heating resistors, respectively. A heating resistor is provided for heating the semiconductor substrate of the semiconductor laser so as to regulate the base temperature T of the chip (i.e., the semiconductor substrate).