Optical Frequency Comb Locking Circuit for Narrow Linewidth Channels
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Solution Overview
Problem
Existing lasers with multiple output channels suffer from frequency noise, non-uniform power distribution, and low optical power per channel, which limits their performance in applications like optical communication and sensing.
Innovation Solution
A photonic integrated circuit (PIC) with an optical frequency comb laser and a broadband laser frequency locking circuit stabilizes multiple output channels by measuring frequency fluctuations and generating an error signal to modulate bias current, ensuring high optical power, narrow linewidth, and uniform power distribution across channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a multi-wavelength laser is used to generate multiple output channels, then the number of output channels is increased, but the optical power per channel decreases to a few mW
Solution Approach 1:
The patent divides the multi-wavelength laser system into N independent frequency channels, each with its own error signal generation and feedback control. By segmenting the control system, each channel can be independently optimized to maintain high optical power while providing multiple output channels through the frequency comb structure.
2Quantity of substance
If a multi-wavelength laser is used to generate multiple output channels, then the number of output channels is increased, but the frequency noise increases导致linewidth broadening
Solution Approach 1:
The patent implements a feedback control system where frequency fluctuations of each channel are measured by comparing with a common reference (high-Q optical resonator), and error signals are generated to correct these fluctuations. This feedback mechanism stabilizes the frequency of all N channels simultaneously, reducing frequency noise and narrowing the linewidth despite having multiple output channels.
3Quantity of substance
If conventional multi-wavelength laser is used, then multiple wavelengths are generated, but the power distribution across channels is non-uniform
Solution Approach 1:
The patent applies local quality control by generating separate error signals for each of the N frequency channels based on their individual frequency fluctuations. This allows independent optimization and uniform power distribution across all channels, as each channel's power can be precisely controlled through its dedicated feedback loop while maintaining the multi-wavelength capability.
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 achieves high-power, narrow-linewidth, and highly correlated output channels with uniform power distribution, enhancing performance in applications such as ultra-high baud rate communications and fiber optic sensing.
Implementation Method 1
the optical frequency comb synthesizes multiple wavelengths with high optical power per comb line and uniform power distribution
Implementation Method 2
measures frequency fluctuations of each channel by comparing it with the corresponding resonance frequency of a common reference (i.e., a high-Q optical resonator)
Implementation Method 3
coherently interfering it with a copy of the channel, and generates a corresponding electrical control signal (e.g., error signal) for each channel
Implementation Method 4
The control signal may be used to modulate bias current of the corresponding channel and hence, correct frequency fluctuations and lock all the frequencies simultaneously to a common frequency reference
Data Source
AI summary
An optical circuit includes a frequency comb laser outputting N channels of light on a single path, an optical splitter splitting the output from laser into three light paths, a first light path as a laser output, a second light path as a reference laser, and a third light path. A high quality factor cavity filter is coupled with the third path. A first wavelength demultiplexer (WDM) is coupled with the second light path configured to demultiplex the light in the second light path into N outputs. A second WDM is coupled with the third light path configured to demultiplex the light in the third light path into N outputs. A mixing circuit is coupled with the N outputs from the first WDM and the N outputs from the second WDM, and has 2N outputs. The mixing circuit is configure to directionally couple the 2 signals for each wavelength (λN) and to output into 2N waveguides the directionally coupled light paths.