Pulse Delay Control in Pump-Probe Spectroscopy
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Solution Overview
Problem
Current methods for generating two separate laser pulses with a known and variable delay are limited by precision, complexity, and cost, making it difficult to achieve picosecond accuracy over a wide time range using standard femtosecond lasers.
Innovation Solution
A device that uses two free-operating laser oscillators, with pulse selectors and a computer-controlled system to select and align pulses, allowing for precise control of the delay between pulses to achieve picosecond accuracy without requiring complex synchronization or control systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single laser system with mechanical delay line is used, then the delay can be adjusted in the picosecond-nanosecond range, but the system requires special attention to maintain pointing stability during mechanical scanning and is limited by the length of the delay line
Solution Approach 1:
The patent replaces the mechanical delay line system with an optical-based solution using two synchronized laser oscillators. The delay is controlled by varying the relative time phase between oscillators through electronic means rather than mechanical scanning, eliminating pointing stability issues while maintaining picosecond precision.
Solution Approach 2:
The system dynamically adjusts the relative time phase between two laser oscillators to achieve variable delay. This dynamic control allows the delay to be changed from picoseconds to seconds without mechanical movement, resolving the stability problem while maintaining precision.
2Duration of action of moving object
If two unsynchronized laser oscillators are used, then arbitrarily long delays can be achieved, but the time jitter and asynchronism limit the accuracy to the oscillation period, typically ten nanoseconds
Solution Approach 1:
The patent introduces synchronization mechanisms and feedback control to maintain a fixed phase relationship between the two laser oscillators. This feedback system corrects for drift and jitter, enabling picosecond accuracy while maintaining the ability to achieve long delays through phase variation.
Solution Approach 2:
The system changes the operational parameters of the laser oscillators by varying their relative time phase rather than relying on their natural oscillation periods. This parameter control allows precise delay adjustment from picoseconds to seconds independent of the oscillators' inherent frequency stability limitations.
3Measurement precision
If two synchronized laser oscillators with variable relative time phase are used, then long delays can be achieved with picosecond precision, but the implementation is costly and complex and cannot be achieved retrospectively on standard commercial laser oscillators
Solution Approach 1:
The patent designs a system that can be integrated with standard commercial laser oscillators, making the advanced functionality accessible to a broader user base. The solution provides picosecond precision delay control over a wide range using conventional components, reducing both cost and complexity while maintaining high performance.
Data Source
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Figure 4a
AI summary
The invention relates to a device for managing light pulses in order to measure the reaction of a sample exposed to a first light pulse, the measurement being performed by analysing a signal emitted by the sample subjected to a second light pulse that is offset relative to the first pulse by a predetermined time interval, including two optical detectors (21, 23) for detecting the pulses of two light beams emitted by two pulsed laser sources (1, 3), respectively, each beam emitting pulses with different respective repetition frequencies, which are arbitrary and stable over a predetermined period, toward said sample, the detectors being connected to a computer (25) in order to determine the time interval between two pulses coming from the first and second beam, respectively, and constituting the first and second pulses, said computer being connected to an analyser (15) for measuring the reaction of the sample, which has the time interval between the two pulses as an input parameter. Moreover, the computer (25) uses an algorithm which processes the stability of the repetition frequencies in order to determine the time interval.