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US 12,590,894 B1Granted
Systems and methods for measuring transient surface reflectivity of an optically excited sample
AssigneeBoard of Trustees of the University of Alabama, for and on behalf of the University of Alabama in Huntsville
InventorsLingze Duan, Hemang Jani
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Abstract
The present disclosure generally pertains to systems and methods for measuring the surface reflectivity of an excited sample. Such systems may be useful in understanding the transient processes created when materials are energetically excited and how they subsequently evolve. By using various techniques to reduce dispersion and improve signal quality, the disclosed systems are capable of accurately measuring these transient processes across a wide spectral range. In addition, the systems can achieve this accuracy with a far less expensive and complicated setup than would be required for many other optical spectroscopy approaches.
Claims21
A system for measuring surface reflectivity of a sample, comprising:
- a laser source configured to transmit a laser pulse along a first optical path to a beam splitter configured to split the laser pulse into a pump pulse and a probe pulse;
- a first plurality of beam-reflecting components configured to reflect the pump pulse from the beam splitter along a second optical path to the sample;
- a second plurality of beam-reflecting components configured to reflect the probe pulse from the beam splitter along a third optical path to the sample, wherein a length of the third optical path is greater than a length of the second optical path such that the probe pulse arrives at the sample subsequent to the pump pulse while the sample is excited by the pump pulse;
- a dispersion-compensating system positioned within the first optical path and configured to induce dispersion into the laser pulse to compensate for dispersion that is induced by the second optical path and the third optical path, wherein the dispersion-compensating system is configured such that the dispersion induced by the dispersion-compensating system (1) is of a type opposite to a type of the dispersion induced by the second optical path and the third optical path and (2) has a magnitude substantially similar to a magnitude of the dispersion induced by the second optical path and the third optical path such that the dispersion induced by the dispersion-compensating system substantially cancels the dispersion induced by the second optical path and the third optical path;
- a photodetector configured to detect a reflection of the probe pulse from the sample transmitted along a fourth optical path;
- and
- a controller configured to determine a value indicative of a surface reflectivity of the sample based on the detected reflection of the probe pulse,
- wherein the dispersion-compensating system comprises:
- a dispersion-compensating mirror positioned within the first optical path, the dispersion-compensating mirror configured to compensate for coarse-grained group-velocity dispersion induced by the second optical path and the third optical path;
- and
- a dispersion-compensating wedge positioned within the first optical path after the dispersion-compensating mirror, the dispersion-compensating wedge configured to compensate for fine-grained group-velocity dispersion induced by the second optical path and the third optical path.
8 more elements
A method for measuring surface reflectivity of a sample, comprising:
- transmitting a laser pulse along a first optical path;
- splitting the laser pulse into a pump pulse and a probe pulse with a beam splitter positioned within the first optical path;
- reflecting the pump pulse to direct the pump pulse to the sample along a second optical path;
- reflecting the probe pulse to direct the probe pulse to the sample along a third optical path, wherein a length of the third optical path is greater than a length of the second optical path such that the probe pulse arrives at the sample subsequent to the pump pulse while the sample is excited by the pump pulse;
- inducing first dispersion into the laser pulse to compensate for second dispersion that is induced by the second optical path and the third optical path, wherein the first dispersion (1) is of a type opposite to a type of the second dispersion and (2) has a magnitude substantially similar to a magnitude of the second dispersion such that the first dispersion substantially cancels the second dispersion, wherein the inducing the first dispersion into the laser pulse comprises:
- (1) using a dispersion-compensating mirror positioned within the first optical path to compensate for coarse-grained dispersion induced during by the second optical path and the third optical path, and (2) using a dispersion-compensating wedge positioned within the first optical path to compensate for fine-grained group-velocity dispersion induced by the second optical path and the third optical path;
- detecting a reflection of the probe pulse from the sample transmitted along a fourth optical path;
- and
- determining a value indicative of a surface reflectivity of the sample based on the detected reflection of the probe pulse.
6 more elements
Dependencies are inferred from the claim text.