Phase-Code Mode-Locked Frequency Comb for Moderate-Speed CR-OCT
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Solution Overview
Problem
Existing frequency comb sources for circular-ranging optical coherence tomography (CR-OCT) are limited to extremely high-speed imaging, lacking suitable solutions for moderate-speed applications, and existing stretched-pulse mode-locked (SPML) lasers are poorly suited for scaling to slower speeds.
Innovation Solution
A phase-code mode-locking (PCML) laser architecture using electro-optic phase modulation and reversible linewidth broadening within a ring-shaped optical resonator, enabling a frequency comb source that operates from kilohertz to megahertz ranges with dynamic re-configurability and simplified frequency stepping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If stretched-pulse mode-locked (SPML) lasers are used for CR-OCT, then high-speed imaging is achieved with repetition rates of several to tens of megahertz, but the system cannot easily scale to slower speeds for moderate-speed applications
Solution Approach 1:
The patent implements dynamic control of the laser repetition rate through electro-optic phase modulation, allowing the system to adaptively adjust operating speed from kilohertz to megahertz ranges. The phase modulators dynamically alter the optical path length and phase of wavelength bands, enabling flexible speed adjustment without hardware changes.
Solution Approach 2:
The invention changes the operating parameters of the laser system by using programmable phase modulation waveforms that control the repetition rate. By modifying the phase modulation parameters (frequency, amplitude, waveform shape), the system can operate across a wide speed range, transforming from a fixed high-speed system to a dynamically adjustable system.
2Device complexity
If the number of measurements is reduced for sparsity in depth-domain, then electronic signal capture and processing bandwidths are lowered, but imaging speed is reduced
Solution Approach 1:
The patent replaces the traditional mechanical/time-domain approach of increasing measurement count with an electro-optic phase modulation approach. Instead of using more measurements to achieve sparsity, the system uses phase-coded wavelength modulation to encode depth information, substituting electronic control for traditional measurement multiplication.
Solution Approach 2:
The invention employs periodic phase modulation of wavelength bands at controlled repetition rates to encode depth information efficiently. The periodic modulation creates a frequency comb structure where each tooth corresponds to a specific depth range, allowing sparse sampling at lower electronic bandwidth while maintaining imaging speed through the temporal encoding scheme.
3Adaptability or versatility
If phase modulators and chromatic dispersion devices are added to create spectral broadening and recovery, then moderate-speed CR-OCT is enabled, but device complexity increases
Solution Approach 1:
The patent makes the optical resonator components serve multiple functions: the phase modulators not only control repetition rate but also create spectral broadening for wavelength multiplexing; the chromatic dispersion devices not only separate wavelength bands but also enable temporal encoding. This multi-functionality reduces the need for additional dedicated components.
Solution Approach 2:
The invention merges the functions of spectral shaping, temporal encoding, and repetition rate control into a unified phase modulation scheme within the optical resonator. The chromatic dispersion and phase modulation work together as an integrated system rather than separate subsystems, reducing overall complexity through functional consolidation.
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 CR-OCT imaging at moderate speeds with A-line rates from 100 kHz to 5 MHz, providing high-quality imaging results and flexibility in wavelength selection without hardware modifications, while reducing electronic bandwidth requirements.
Implementation Method 1
a first optical phase modulator... modulating a first phase using the first optical phase modulator driven by the first waveform
Implementation Method 2
the first optical phase modulator and the second optical phase modulator being configured to create spectral broadening by the first optical phase modulator
Implementation Method 3
the second optical phase modulator... modulating a second phase using the second optical phase modulator driven by the second waveform comprising an inverse of the first waveform
Implementation Method 4
spectral recovery by the second optical phase modulator of a particular wavelength band... by modulating a second phase using the second optical phase modulator driven by the second waveform comprising an inverse of the first waveform
Implementation Method 5
the first chromatic dispersion device being configured between the first optical phase modulator and the second optical phase modulator to provide chromatic dispersion so as to subject each of the plurality of wavelength bands to a respective plurality of different time delays
Implementation Method 6
the multi-line spectral domain filter being configured to provide multi-line spectral filtering with narrow bandwidths in order to induce power loss for each of the plurality of wavelength bands except for the particular wavelength band
Implementation Method 7
the second chromatic dispersion device being configured to provide chromatic dispersion compensation to an output of the multi-line spectral domain filter in order to compensate a group delay dispersion within the optical resonator
Implementation Method 8
an optical amplifier
Implementation Method 9
a ring-shaped optical resonator for circulating a plurality of wavelength bands
Data Source
AI summary
A source for providing electromagnetic radiation within a particular spectral range, including: a ring-shaped optical resonator for circulating a plurality of wavelength bands including: a first optical phase modulator, a first chomatic dispersion device, a second optical phase modulator, a multi-line spectral domain filter, a second chromatic dispersion device, and an optical amplifier; a controller coupled to the first optical phase modulator and the second optical phase modulator which is configured to drive the first optical phase modulator with a first waveform and the second optical phase modulator with a second waveform, the first chromatic dispersion device being configured between the first optical phase modulator and the second optical phase modulator to provide chromatic dispersion so as to subject each of the plurality of wavelength bands to a respective plurality of different time delays, the first and second optical phase modulators being configured to create spectral broadening.