Fabry-Pérot Stabilized Tunable Laser for Discrete Frequency Steps
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Solution Overview
Problem
Current discretely tunable laser systems, such as coupled cavity laser systems, are inherently unstable and chaotic, requiring expensive high-resolution wavemeters for precise frequency tuning, which increases system costs and complexity.
Innovation Solution
A discretely tunable laser system incorporating an externally optically coupled Fabry-Pérot interferometer and a proportional-integral-derivative (PID) controller to stabilize the continuously tunable laser, allowing precise frequency tuning by locking it to Fabry-Pérot resonance edges, thereby achieving stable and consistent frequency steps without the need for expensive wavemeters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a continuously tunable laser is used to achieve discrete frequency tuning, then frequency stability is improved, but system cost increases due to the need for expensive wavemeters
Solution Approach 1:
The patent introduces a Fabry-Pérot interferometer as an intermediary device between the continuously tunable laser and the control system. The interferometer provides reference frequencies through its resonance modes, serving as a mediator that enables precise frequency control without requiring expensive wavemeters. The interferometer's transmission peaks act as stable reference points for locking the laser frequency.
Solution Approach 2:
The patent implements a feedback control system using photodiodes to detect the laser output and generate error signals. These error signals are fed back to the laser control mechanism to adjust and lock the laser frequency to the desired reference frequencies. The feedback loop continuously monitors and corrects frequency deviations, achieving stable discrete tuning.
2Device complexity
If a coupled cavity laser system is used for discrete tuning, then system cost is reduced, but frequency stability deteriorates due to inherent instability and chaos
Solution Approach 1:
The patent extracts the stabilization function from the laser cavity itself and implements it externally using a Fabry-Pérot interferometer. By taking out the frequency reference generation from the potentially unstable laser cavity and placing it in a stable external interferometer, the system achieves frequency stability without the chaos inherent in coupled cavity systems.
Solution Approach 2:
The Fabry-Pérot interferometer serves as an intermediary that provides stable frequency references independent of the laser cavity's instability. The interferometer's well-defined resonance modes act as a stable mediator that the laser can lock onto, eliminating the frequency chaos problem of coupled cavity systems.
3Device complexity
If coupled cavity laser systems are used for discrete tuning, then system cost is reduced, but manufacturing precision deteriorates due to sensitivity to parameter changes
Solution Approach 1:
The Fabry-Pérot interferometer provides a stable external reference that is insensitive to laser diode parameter variations. The interferometer's resonance frequencies serve as precise manufacturing references that ensure consistent frequency steps, overcoming the sensitivity to reflectivity and gain profile changes in coupled cavity systems.
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 provides a low-cost, stable, and precise method for achieving discrete frequency tuning across a range of wavelengths, improving frequency stability and reducing system costs by eliminating the need for high-cost wavemeters.
Implementation Method 1
a Fabry-Pérot interferometer configured to produce a plurality of resonances upon incidence of the fourth beam, the plurality of resonances equally spaced in frequency, each of the plurality of resonances defining one of the plurality of selectable frequencies
Implementation Method 2
a first photodiode configured to generate a first electrical signal corresponding to a transmission power of the third beam, a second photodiode configured to generate a second electrical signal corresponding to a transmission power of the transmission beam
Data Source
AI summary
Discretely tunable laser systems include a continuously tunable laser for outputting a beam tunable among selectable frequencies, the selectable frequencies are separated in frequency by discrete frequency intervals, the discrete frequency intervals include a maximum interval and a minimum interval, where a difference between the maximum interval and the minimum interval is 100 MHz or less, and an external stabilization circuit coupled to the continuously tunable laser and a controller. The external stabilization circuit includes a first photodiode generating a first signal corresponding to a portion of the beam and an interferometer that produces resonances upon incidence of another portion of the beam. The resonances are equally spaced in frequency, with each defining one of the selectable frequencies. A second photodiode generates a second signal corresponding a transmission beam generated by the interferometer. The controller tunes the continuously tunable laser among the selectable frequencies based on the first and second signals.