Passive Pulse Splitter for Multiphoton Microscopy
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Solution Overview
Problem
Multi-photon fluorescence microscopy (MPFM) techniques face limitations due to small excitation cross-sections, resulting in weak signals, long data acquisition times, and high requisite pulse powers, with excessive photodamage and photobleaching issues when increasing pulse power.
Innovation Solution
A passive pulse splitter system that converts a single high-power laser pulse into multiple sub-pulses with a higher repetition rate and lower power, using different optical path lengths through materials with varying refractive indices to achieve temporal separation and reduce photodamage, while maintaining signal intensity and spatial resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high pulse power is used to increase signal rate, then signal intensity is improved, but photodamage and photobleaching increase
Solution Approach 1:
The patent divides a single high-power laser pulse into multiple lower-power sub-pulses using a pulse splitter. This segmentation allows the total signal rate to be maintained or enhanced while reducing the peak power of individual pulses, thereby minimizing photodamage and photobleaching effects on the sample.
Solution Approach 2:
The patent employs periodic pulse repetition by splitting each input pulse into multiple sub-pulses separated by specific time intervals. This periodic structure increases the effective signal rate while distributing the energy delivery over time, preventing excessive energy accumulation that would cause photodamage.
2Illumination intensity
If high pulse power is used to overcome small excitation cross-sections, then fluorescence signal is improved, but photobleaching increases
Solution Approach 1:
By segmenting the high-power pulse into multiple sub-pulses, the patent maintains sufficient illumination intensity for fluorescence excitation while distributing the total energy exposure, thereby reducing photobleaching of the fluorophores in the sample.
Solution Approach 2:
The patent changes the temporal parameters of the laser pulses by introducing controlled time delays between sub-pulses. This parameter modification allows optimization of fluorescence signal accumulation while keeping individual pulse intensities below the photobleaching threshold.
3Measurement precision
If long data acquisition times are used to compensate for weak signals, then signal quality is improved, but productivity decreases
Solution Approach 1:
The patent uses periodic pulse repetition with multiple sub-pulses per input pulse to increase the effective signal rate. This allows faster data acquisition while maintaining sufficient signal quality through the accumulated fluorescence from multiple sub-pulses within each acquisition window.
Solution Approach 2:
By generating multiple sub-pulses in rapid succession, the patent maintains continuous useful action on the sample, increasing the signal rate without requiring longer acquisition times. This continuous stimulation improves both signal quality and acquisition speed.
4Productivity
If pulse splitting is implemented to increase repetition rate, then signal rate is improved, but device complexity increases
Solution Approach 1:
The patent introduces a pulse splitter as an intermediary device that passively divides input pulses into sub-pulses using optical path length differences. This intermediary component achieves pulse multiplication without requiring complex active control systems, maintaining relatively simple device architecture while improving signal rate.
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 pulse splitter system significantly increases signal rate and reduces photobleaching and photodamage, enabling faster data acquisition with minimal power loss and compatibility with existing laser systems, suitable for nonlinear optical applications.
Implementation Method 1
The pulse splitter includes at least two different materials through which the sub-pulses travel such that each of the sub-pulses travel along different optical path lengths through the different materials to cause a temporal separation between each of the sub-pulses. The optical path length depends on both the distance traveled through the material and the index of refraction of the material.
Data Source
AI summary
An apparatus includes a pulsed laser source that produces a pulsed laser beam at an input repetition rate and an input pulse power; a passive pulse splitter that receives the pulsed laser beam and outputs a signal including a plurality of sub-pulses for each input pulse of the pulsed laser beam, where the sub-pulses have a repetition rate that is greater than the input repetition rate and at least two of the sub-pulses have power less than the input pulse power; a sample accommodating structure configured to accommodate a sample placed in the path of a sample beam that is formed from the beam that exits the pulse splitter; and a detector that receives a signal of interest emitted from a sample accommodated by the sample accommodating structure based on the incident sample beam.