Fiber Swept Source with Optical Delay Raster Scanning
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Solution Overview
Problem
Conventional optical imaging systems face limitations in scanning speed and signal readout speed, resulting in slow image capture and low instantaneous peak power, which are inadequate for high-speed dynamic imaging applications such as ultrafast diagnosis and multi-photon microscopy.
Innovation Solution
A spatio-temporally incremental fiber swept source (STIFSS) is developed, utilizing a fiber ring cavity for ultrafast femtosecond pulse generation, pulse pre-chirping, and ultrafast spatial sweeping, enabling a 2D spatially-sweeping laser source with peak power up to the kW level and sub-picosecond dwell time, eliminating the need for mechanical or electronic movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If mechanical translation stages are used for point-by-point scanning, then the system can achieve 2D imaging, but the scanning speed is limited to several mm/s due to mechanical inertia
Solution Approach 1:
The patent replaces mechanical translation stages with an acousto-optic deflector (AOD) that uses acoustic waves to steer the laser beam. This substitution eliminates mechanical inertia, enabling scanning speeds in the kHz range compared to mm/s for mechanical stages, while reducing device complexity by removing bulky mechanical components.
Solution Approach 2:
The patent employs periodic acoustic wave modulation in the AOD to achieve rapid beam deflection. By modulating the acoustic frequency and amplitude periodically, the system can sweep the laser beam across the sample at high speeds, achieving 2D imaging frame rates of 100 Hz or higher.
2Productivity
If CCD/CMOS cameras are used for signal readout, then the system can capture images, but the readout speed is limited to 100 Hz resulting in long readout time
Solution Approach 1:
The patent replaces CCD/CMOS camera readout with a photodetector-based detection system that reads optical signals at MHz frequencies. This substitution eliminates the electronic readout bottleneck of cameras, reducing readout time from seconds to microseconds and enabling imaging frame rates of 100 Hz or higher.
Solution Approach 2:
The patent uses periodic modulation of the acoustic wave in the AOD to encode spatial information into temporal signals that can be rapidly detected by the photodetector. This time-encoding approach enables fast readout by converting spatial scanning into temporal frequency domain measurements.
3Productivity
If wavelength-swept source is used to leverage high-speed photodetectors, then the readout speed can be increased to MHz range, but the instantaneous peak power is limited to mW level
Solution Approach 1:
The patent uses periodic acoustic wave modulation in the AOD to sweep the laser beam rapidly across the sample while maintaining high peak power. The periodic modulation enables the system to achieve both fast readout speeds (MHz range) and high instantaneous peak power (kW level) by concentrating energy in short pulses rather than continuous low-power illumination.
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 STIFSS achieves 2D image capture at 10s of MHz, with sub-picosecond dwell time and high peak power, enabling ultrafast imaging and multi-photon applications, such as flow cytometry and confocal microscopy, while being cost-effective and compatible with existing optical systems.
Implementation Method 1
a fiber ring cavity with nonlinear polarization rotation (NPR) mode-locking for ultrafast femtosecond pulse generation
Implementation Method 2
a 2D spatially-sweeping unit (SSU) with a 2D pixel-delay fiber array for spatially-sweeping the sub-ps pulse train in an all-optical manner
Data Source
Figure 1A~2
Figure 3A~4D
Figure 5A~6D
AI summary
A spatio-temporally incremental fiber sweep source includes a laser light pulse generator for generating light pulses and a fiber array (24) of individual optical fibers. The fiber array (24) has an input end (21) and an output end (23), with the fibers at the input end (21) receiving the light pulses substantially simultaneously. The optical fibers at the output end (23) are arranged in a raster scan pattern, e.g., a square pattern, wherein the optical delay in each fiber is greater than the previous one in the scan pattern direction. As a result light exits the array (24) in a completely optical two dimensional raster scan pattern. It has no moving parts, and thus no mechanical inertia, so extremely high speed scanning can be achieved.