Hybrid External Cavity Laser Mode-Hopping Reduction
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Solution Overview
Problem
Tunable silicon photonic reflectors in hybrid external cavity lasers are sensitive to temperature changes, leading to optical mode-hopping, which causes data corruption and instability in high-speed communication systems.
Innovation Solution
A hybrid external cavity laser design incorporating a semiconductor optical amplifier with a reflective coating, optically coupled to a photonic chip featuring a ring resonator and thermal-tuning mechanism, which adjusts the resonance wavelength to lock the cavity mode to a carrier wavelength, minimizing mode-hopping through temperature control and phase adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a tunable silicon photonic reflector is used to control and tune the wavelength of the laser, then wavelength tunability is achieved, but optical mode-hopping occurs due to temperature sensitivity
Solution Approach 1:
The patent implements a feedback control system using a photodetector to monitor the laser output and a control circuit to adjust the thermal-tuning mechanism. This closed-loop feedback actively compensates for temperature-induced wavelength drift and prevents mode-hopping, thereby maintaining optical mode stability while preserving wavelength tunability capabilities
Solution Approach 2:
The patent employs a thermal-tuning mechanism that changes the temperature parameter of the silicon photonic reflector to control the resonance wavelength. By precisely adjusting the temperature, the system can tune the laser wavelength while the feedback system ensures smooth transitions without mode-hopping, resolving the contradiction between tunability and stability
2Power
If the optical gain and laser section length is increased to greater than 500 μm, then optical gain is improved, but cavity modes are spaced narrowly causing multiple modes within a single ring resonator resonance
Solution Approach 1:
The patent uses a tunable silicon photonic reflector with selectively adjustable resonance characteristics to create local quality differentiation. The reflector can be tuned to provide high reflectivity at specific wavelengths while maintaining lower reflectivity at other wavelengths, allowing the system to support multiple cavity modes within the gain bandwidth while still achieving sufficient optical gain through the extended laser section
3Reliability
If temperature control is implemented to stabilize the resonance wavelength, then mode-hopping is reduced, but device complexity increases
Solution Approach 1:
The patent implements a self-service control system where the photodetector monitors the laser output and the control circuit automatically adjusts the thermal-tuning mechanism to maintain stable operation. This self-regulating system reduces mode-hopping without requiring complex external temperature control equipment, as the system uses its own output to control itself
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 ensures stable laser operation with reduced optical mode-hops, preventing data glitches and enabling high-speed, low-noise, single-mode laser performance for inter- and intra-chip connections in WDM systems.
Implementation Method 1
a ring resonator, optically coupled to the optical waveguide and having a resonance wavelength, which reflects at least the resonance wavelength in the optical signal
Implementation Method 2
a thermal-tuning mechanism, thermally coupled to the ring resonator, which adjusts the resonance wavelength; control logic, electrically coupled to the thermal-tuning mechanism and the photo-detector, which adjusts the temperature of the ring resonator based on the measured optical power to lock a cavity mode of the optical cavity to a carrier wavelength
Data Source
AI summary
An optical source is described. This optical source includes a semiconductor optical amplifier (with a semiconductor other than silicon) that provides an optical gain medium and that includes a reflector. Moreover the hybrid external cavity laser includes a photonic chip with: an optical waveguide that conveys an optical signal output by the semiconductor optical amplifier; and a ring resonator, having a resonance wavelength, which reflects at least a resonance wavelength in the optical signal, where the reflector and the ring resonator define an optical cavity. Furthermore, the photonic chip includes: a thermal-tuning mechanism that adjusts the resonance wavelength; a photo-detector that measures an optical power output by the ring resonator; and control logic that adjusts the temperature of the ring resonator based on the measured optical power to lock a cavity mode of the optical cavity to a carrier wavelength.