Transient Absorption Measurement Using Asynchronous Pump-Probe
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Solution Overview
Problem
Conventional transient absorption measurement methods face limitations in achieving high time resolution and wide time-range measurements, particularly in the 100 picosecond to 1 millisecond range, due to restrictions in the CW probe and pump-probe methods, and require expensive and complex equipment.
Innovation Solution
A method and apparatus using a pump light source and a probe light source with asynchronous operation, where the probe light pulse is repeatedly generated with a shorter repetition time interval than the pump light pulse, allowing for shifting delay times and higher time-density data collection, enabling measurements across a wide time region without the need for expensive devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the CW probe method is used, then the measurement can cover longer time regions, but the time resolution is limited to about 10-50 nanoseconds
Solution Approach 1:
The probe light is divided into multiple pulses within a single pump light period, creating multiple measurement opportunities. Each probe pulse provides a time-resolved measurement point, and collectively they cover the entire time range from picoseconds to milliseconds, resolving the contradiction between time range and time resolution.
Solution Approach 2:
The probe light source operates at a higher repetition frequency than the pump light, generating periodic probe pulses that sample the transient absorption at different time points. This periodic sampling enables high time resolution measurements across the entire measurement window, overcoming the limitations of both CW and conventional pump-probe methods.
2Measurement precision
If the pump-probe method is used, then the time resolution can reach femtosecond level, but the measurement is limited to time regions shorter than 5 nanoseconds
Solution Approach 1:
The measurement window is segmented into multiple probe pulse intervals, allowing the system to capture transient absorption at different time delays without requiring a single long delay stage. This enables coverage from femtosecond to millisecond ranges while maintaining high time resolution determined by the probe pulse width.
Solution Approach 2:
Instead of extending the delay time in a single dimension (which limits the maximum delay to 5 ns), the invention adds a new dimension by using multiple probe pulses at different repetition rates. This multi-dimensional approach allows simultaneous access to both short and long time scales.
3Adaptability or versatility
If a streak camera is used in CW probe method to measure wide time region, then the measurement capability is improved, but the device becomes exceptionally expensive
Solution Approach 1:
The invention replaces the expensive streak camera with conventional, inexpensive photodetectors. By using multiple short probe pulses instead of a single long integration, the system achieves wide time range measurement capability without requiring costly specialized detectors. The probe pulses act as temporary, disposable measurement probes that enable extended time range with simple detectors.
4Measurement precision
If conventional methods are used to remove concomitant light emission influence, then additional measurements are required, but the measurement time increases
Solution Approach 1:
The measurement of transient absorption and the measurement for removing concomitant light emission influence are merged into a single simultaneous process. Multiple probe pulses serve dual purposes: they measure the transient absorption signal and simultaneously provide data for characterizing and removing concomitant emissions, eliminating the need for separate measurement sequences.
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
This approach allows for transient absorption measurements in a wide time region, including the previously unmeasurable 'gap region', with high time resolution and density, and effectively removes the influence of concomitant light emissions without additional measurements, reducing the complexity and cost of the measurement process.
Implementation Method 1
pump light pulse repeatedly irradiated on a sample
Implementation Method 2
probe light pulse repeatedly irradiated on the sample every time the pump pulse is irradiated
Data Source
AI summary
By use of a pump light source for repeatedly generating a pump light pulse and a probe light source for repeatedly generating a probe light pulse in a shorter repetition time interval than the pump light pulse, the pump light pulse is repeatedly irradiated on a sample, and the probe light pulse is repeatedly irradiated on the sample every time the pump pulse is irradiated. An intensity of a probe light pulse having passed through the sample is detected. A shift in a delay time of the probe light pulse with respect to the pump light pulse is measured every time the pump light pulse is irradiated. Transient absorption measurement data of the sample is obtained based on the detected data of the probe light pulse intensity obtained in higher time density than repetition time density of the probe light pulse based on the measured shift in the delay time.