Electro-Optic Phase-Code Mode-Locking for Moderate-Speed CR-OCT
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing frequency comb sources for circular-ranging optical coherence tomography (CR-OCT) are limited to extremely high-speed imaging and do not support moderate-speed applications, leading to challenges in bandwidth requirements and signal capture complexity.
Innovation Solution
A phase-code mode-locking (PCML) laser architecture that uses electro-optic phase modulation and reversible linewidth broadening to generate a frequency comb, allowing operation 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 to provide stepped frequency comb output for CR-OCT, then imaging speed can be increased to several to tens of megahertz, but the system cannot easily scale to slower speeds and does not provide solutions for moderate-speed CR-OCT
Solution Approach 1:
The patent implements dynamic control of the optical phase modulators with electronically adjustable waveforms, allowing the system to adapt its operation across a wide speed range from kilohertz to megahertz. The dynamic phase modulation enables the frequency comb generation to be tuned to different repetition rates by changing the modulation waveform parameters, providing versatility across speed regimes without hardware modifications.
Solution Approach 2:
The invention changes the operational parameters of the optical modulators by applying different drive waveforms with varying frequencies and phases. By adjusting the electrical drive parameters (frequency, amplitude, phase) to the phase modulators, the system can generate frequency combs at different repetition rates, enabling operation from kilohertz to megahertz ranges and resolving the contradiction between high speed and speed adaptability.
2Productivity
If higher imaging speeds are achieved using SPML lasers, then electronic signal capture and processing bandwidths must be increased, but this increases system complexity and cost
Solution Approach 1:
The patent replaces mechanical or high-bandwidth electronic scanning systems with a purely optical frequency comb generation approach using phase modulators. The optical system inherently generates the stepped frequency sequence needed for CR-OCT, eliminating the need for high-speed mechanical scanners or complex high-bandwidth electronic signal capture systems, thus reducing device complexity while maintaining high imaging speeds.
3Adaptability or versatility
If moderate-speed CR-OCT is implemented, then a different source technology is needed compared to high-speed SPML lasers, but this requires hardware modifications and development of new systems
Solution Approach 1:
The patent creates a universal frequency comb generation system that can operate across kilohertz to megahertz ranges using the same hardware platform. The optical resonator with phase modulators serves multiple functions: generating frequency combs at different repetition rates, enabling both high-speed and moderate-speed CR-OCT, and providing a unified architecture that eliminates the need for different source technologies for different speed regimes.
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 moderate-speed CR-OCT imaging with A-line rates from 100 kHz to 5 MHz, providing improved imaging speeds and reduced electronic bandwidth requirements without hardware modifications, while maintaining coherence-length limited imaging depths.
Implementation Method 1
a first optical phase modulator... configured to create spectral broadening by the first optical phase modulator of each of the plurality of wavelength bands
Implementation Method 2
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 3
a second optical phase modulator... configured to create 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 4
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 5
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 6
an optical amplifier
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
Figure 3(a)~3(h)
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 chromatic 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 optical phase modulator and the second optical phase modulator being configured to create spectral broadening by the first optical phase modulator of each of the plurality of wavelength bands and spectral recovery by the second optical phase modulator of a particular wavelength band of the plurality of wavelength bands by modulating a first phase using the first optical phase modulator driven by the first waveform and, after a particular time delay, modulating a second phase using the second optical phase modulator driven by the second waveform comprising an inverse of the first waveform, the particular time delay being determined so as to create spectral recovery for the particular wavelength band of the plurality of wavelength bands, 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, 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 and match a roundtrip frequency for each of the plurality of wavelength bands, and the first and second waveforms being configured to create a periodic phase modulation for recovery of the plurality of wavelength bands at a frequency that is an integer multiple of a roundtrip frequency of the optical resonator.