Time-wavelength optical sampling systems and methods for determining composition of a sample based on detected pulses of different durations
Inventors
Assignees
University of Alabama in Huntsville
Publication Number
US-11300502-B1
Publication Date
2022-04-12
Expiration Date
2039-05-17
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Abstract
A time-wavelength optical sampling system may be configured to determine a substance's composition based on variations in optical pulses caused by the substance's absorption of wavelengths of the pulse. A dispersion medium may disperse pulses to form stretched signal pulses that are incident on a substance under test. Optical gating is used to overlap each signal pulse with a portion of a reference pulse to generate a cross-correlation signal corresponding to a portion of the signal pulse, which may be detected by a slow detection speed detector. A controller controls delay introduced to the reference pulses so that different wavelength ranges are sampled for various signal pulses, thereby enabling the entire wavelength range for the signal pulses to be sampled over time without requiring an expensive high-speed optical detector. By analyzing absorption across the entire wavelength range as indicated by cross-correlation signals, the composition of the substance can be identified.
Core Innovation
The invention provides a time-wavelength optical sampling system configured to determine the composition of a substance by analyzing variations in optical pulses after interaction with the sample. The system disperses optical pulses via a dispersion medium to form stretched signal pulses which are then directed through a sample chamber containing the substance under test. As the stretched pulses pass through the sample, certain wavelengths are absorbed depending on the composition, thereby imprinting power variations specific to those wavelengths.
To detect these power variations without requiring high-speed detectors, the system uses optical gating by overlapping portions of the stretched pulse (signal pulse) with a shorter duration, high-peak-power reference pulse within a combiner. The overlapping produces a cross-correlation signal, which is detected by a detector with relatively slower response time. By systematically varying the delay of the reference pulse using a tunable delay line or similar approach, the system samples different wavelength ranges of the stretched pulse over numerous iterations.
This configuration enables the system to analyze the absorption spectrum of the entire wavelength range by compiling the cross-correlation signals from multiple overlapped portions, allowing for identification of the substance’s composition based on detected absorption features. The technique solves the problem of expensive, high-speed optical detection traditionally needed for time-wavelength optical spectrometry, and achieves improved signal-to-noise ratio through the optical gating approach.
Claims Coverage
The independent claims present three main inventive features relating to an optical sampling system and associated methods for determining sample composition via cross-correlated optical pulses.
Determining sample composition by cross-correlating dispersed and reference pulses
An optical sampling system comprising: - A light source providing an optical signal with a first pulse - A dispersion medium dispersing the first pulse into a stretched (dispersed) pulse - A sample chamber positioned in the path of the dispersed first pulse - A combiner that receives the dispersed first pulse from the sample chamber and a second (reference) pulse, where the duration of the dispersed first pulse is greater than that of the second pulse - An optical detector configured to detect signals resulting from the combination and to provide data indicative of the combined pulse The system determines the composition of the sample based on data acquired from the detection of the cross-correlated (combined) pulses.
Sampling multiple wavelength ranges via time-controlled cross-correlation
A method and system utilizing: - Multiple first pulses dispersed by a dispersion medium and transmitted through a sample - Multiple second (reference) pulses arriving at a combiner with controlled timing - Cross-correlation of each dispersed first pulse with a corresponding second pulse, each overlap sampling a different wavelength range of the stretched pulse - An optical detector acquiring and providing data for each cross-correlated pulse By adjusting the timing of reference pulses, the system samples different wavelength portions, enabling analysis of the absorption spectrum for composition identification.
Optical sampling method combining dispersed and reference pulses with temporal delay control
A method for optical sampling comprising: 1. Transmitting an optical signal with at least one pulse from a light source 2. Dispersing the pulse with a dispersion medium to create a stretched pulse 3. Receiving the stretched pulse from a sample at a combiner 4. Receiving a reference pulse at the combiner and combining them, where the stretched pulse has greater duration 5. Detecting the combined pulse with an optical detector 6. Determining sample composition based on the detected data The method optionally includes splitting pulses to form reference pulses and using a tunable delay line and/or controller to adjust timing such that cross-correlation samples different wavelength ranges.
The inventive features collectively describe a time-wavelength optical sampling system and method that disperses optical pulses, selectively overlaps portions of dispersed signal pulses with reference pulses at controlled delays, and detects cross-correlation signals for determining sample composition. These features enable spectral analysis without the need for expensive high-speed optical detectors.
Stated Advantages
Eliminates the requirement for expensive high-speed optical detectors by enabling the use of detectors with slower response time.
Improves signal-to-noise ratio at the detector by using optical gating and increasing cross-correlation signal strength relative to original signal pulse power.
Allows accurate detection of power variations corresponding to sample absorption across the entire wavelength range by compiling results over multiple pulses and controlled delays.
Permits compact system design, as resolution is not limited by detector size or the need for spatial separation.
Documented Applications
Determining the composition of a trace gas based on wavelength-dependent absorption within a sample chamber.
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