Line-Field Swept Laser OCT With Thin-Film Filter Tuning
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Solution Overview
Problem
Existing swept-source optical coherence tomography (SS-OCT) systems face limitations in effective repetition rates and duty cycle due to four-wave mixing effects in semiconductor optical amplifiers, leading to motion artifacts and reduced imaging speed.
Innovation Solution
A line scan or line field swept source optical coherence tomography system utilizing a tunable laser with a collimating lens, end reflector, focusing lens, thin film bandpass filter, and angle control actuator, where light travels in free space, and employs a galvanometer or servomechanism for scan linearity, enabling high-speed imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If semiconductor optical amplifier (SOA) based ring laser design is used to achieve high-speed swept source, then imaging speed increases, but four-wave mixing effects cause negative wavelength sweeps to suffer significant power loss
Solution Approach 1:
The patent extracts and removes the semiconductor optical amplifier (SOA) component from the laser design, replacing it with a fiber laser architecture. This eliminates the four-wave mixing effects that caused asymmetric power loss during wavelength sweeping, while maintaining high-speed imaging capabilities through the fiber laser's intrinsic properties.
Solution Approach 2:
The patent changes the fundamental operating parameters of the laser system by transitioning from an SOA-based design to a fiber laser design. This parameter change includes modifying the gain medium, cavity structure, and wavelength tuning mechanism, thereby achieving symmetric bidirectional wavelength sweeping without the power loss associated with four-wave mixing effects.
2Speed
If short cavity laser is used to increase sweep speeds, then imaging speed improves, but effective duty cycle is limited to less than 50% due to FWM effects
Solution Approach 1:
The patent removes the source of four-wave mixing effects by replacing the short cavity laser with a fiber laser architecture. This extraction of the problematic component enables symmetric bidirectional wavelength sweeping, doubling the effective duty cycle from less than 50% to potentially 100% while maintaining high sweep speeds.
3Productivity
If fiber spool is used for sweep buffering and multiplexing, then effective repetition rate increases, but significant birefringence is introduced to the laser output
Solution Approach 1:
The patent eliminates the need for long fiber spools for sweep buffering by implementing sweep buffering within the fiber laser cavity itself. This extraction of the external fiber spool component prevents the introduction of birefringence and polarization instability, while still achieving high effective repetition rates through the intracavity buffering mechanism.
4Device complexity
If conventional swept laser technology is used, then system complexity is reduced, but imaging speed is limited
Solution Approach 1:
The patent replaces conventional mechanical swept laser technology with a fiber laser system that uses optical feedback and nonlinear optical effects for wavelength sweeping. This substitution eliminates the need for mechanical moving parts while achieving significantly higher imaging speeds, and the fiber-based architecture actually reduces overall system complexity by integrating multiple functions within the fiber structure.
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 system achieves high-speed imaging with improved effective repetition rates and reduced motion artifacts, facilitating compact and cost-effective optical coherence tomography and spectroscopy applications.
Implementation Method 1
a thin film bandpass filter between the collimating lens and the focusing lens
Implementation Method 2
at least one angle control actuator for changing the angle of the thin film filter to the collimated light
Implementation Method 3
a collimating lens for collimating light from the gain chip
Implementation Method 4
a focusing lens for focusing the collimated light on the end reflector
Implementation Method 5
an end reflector
Data Source
AI summary
A line field optical coherence tomography (OCT) system and an absorption spectrometer system employing a tunable or swept laser architecture. The laser is a cat's-eye configuration with a preferably transmissive tilt tuned interference thin film filter.