Mode-Locked Laser With Tunable Comb Spacing
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Solution Overview
Problem
Conventional mode-locked semiconductor lasers are unable to change the spacing between carrier frequencies of their output comb, limiting their adaptability in optical transport systems.
Innovation Solution
A hybrid solid-state mode-locked semiconductor laser is developed, comprising a III-V semiconductor chip and a silicon chip, where the silicon chip includes optical waveguides with multiple paths of different lengths, and optical switches are used to change the effective optical length of the laser cavity, allowing for adjustable output-comb frequency spacing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional mode-locked semiconductor laser is used, then the device structure is simple and stable, but the output-comb frequency spacing cannot be changed
Solution Approach 1:
The patent implements dynamic adjustability of the laser cavity length by incorporating optical switches that can dynamically reconfigure the optical path. This allows the cavity length to be changed from a fixed value to a variable parameter, enabling the output-comb frequency spacing to be adjusted dynamically while maintaining a relatively compact device structure through integrated photonic circuit design.
Solution Approach 2:
The laser cavity is segmented into multiple configurable optical paths with different lengths. By dividing the optical path into selectable segments and using optical switches to connect different segments, the system can achieve variable cavity lengths without requiring completely different cavity structures for each frequency spacing value.
2Adaptability or versatility
If multiple optical paths with different lengths are introduced to change frequency spacing, then the frequency spacing becomes adjustable, but the device complexity increases
Solution Approach 1:
The optical switches serve multiple functions: they act as mode-locking elements, cavity length selectors, and optical path configurators simultaneously. This multi-functionality reduces the need for separate dedicated components for each function, thereby limiting the increase in device complexity despite the introduction of multiple optical paths.
Solution Approach 2:
The mode-locking function and the cavity length selection function are merged into a single component system. The optical switches that select different cavity lengths also provide the mode-locking action, combining multiple functions into unified components to minimize overall device complexity.
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
Enables the output-comb frequency spacing to be changed by a factor of at least 1.5, enhancing the flexibility and adaptability of the laser in applications such as wavelength-division-multiplexed systems and RF-photonics carrier generation.
Implementation Method 1
the active section being configured to generate light in response to an electrical current being driven therethrough
Implementation Method 2
the mode-locking section being configured to modulate the light to cause an optical pulse train to be emitted
Implementation Method 3
The silicon chip includes a plurality of optical waveguides arranged to provide multiple optical paths of different effective lengths for the light generated in the laser cavity
Implementation Method 4
Different optical paths can be controllably selected, using one or more optical switches connected between the optical waveguides, to change the effective optical length of the laser cavity
Data Source
AI summary
A mode-locked semiconductor laser capable of changing the spacing between the carrier frequencies of its output comb. In an example embodiment, the mode-locked semiconductor laser is implemented as a hybrid solid-state device comprising a III-V semiconductor chip and a silicon chip attached to one another to form a laser cavity. The III-V semiconductor chip includes a gain medium configured to generate light in response to being electrically and/or optically pumped. The silicon chip includes a plurality of optical waveguides arranged to provide multiple optical paths of different effective lengths for the light generated in the laser cavity. Different optical paths can be controllably selected, using one or more optical switches connected between the optical waveguides, to change the effective optical length of the laser cavity and, as a result, the output-comb frequency spacing. In some embodiments, the output-comb frequency spacing can be changeable at least by a factor of 1.5.