RU2729950C2 - Systems and methods of polling parameters in multiple places in a sample - Google Patents

Abstract

FIELD: optical measuring equipment.SUBSTANCE: system (100) for polling one or more parameters in multiple places in sample (108) comprises a first ultrafast laser source (102) configured to supply a first plurality of pulses, wherein first source (102) is configured to supply a frequency comb having a first repetition frequency, wherein the first set of pulses interacts with sample (108) in multiple places in sample (108) to obtain processed pulses. System also comprises a second ultrafast laser source (104) configured to feed a second plurality of pulses, wherein second source (104) is configured to supply a frequency comb having a second repetition frequency which is different from the first repetition frequency. Besides, the system comprises support device (110) configured to supply reference pulses having a variable time delay, variable phase delay, variable path difference, or combinations thereof; detector unit (124) configured to detect processed pulses from first and second sources (102 and 104) and reference pulses; and a data processing unit (128) configured to process the detected pulses and perform measurements of one or more parameters for a plurality of locations in sample (108).EFFECT: technical result consists in enabling increase in resolution and acceleration of measurement process.17 cl, 4 dwg

Description

Background of the invention

[0001] Embodiments of the described invention relate to systems and methods for distributed measurements of one or more parameters. In particular, the systems and methods relate to distributed measurements using optical technology.

[0002] Typically in large gas chambers or in optically transparent samples, the absorption of incident optical radiation is measured as the total amount of optical radiation passing through the sample. It would be desirable to develop optical methods that can provide a distribution of a variety of parameters such as gas temperature, gas concentration and / or gas pressure within a chamber, or high resolution spatially distributed spectrum measurement.

[0003] The use of optical pulses is an optical technology that is used to encode information related to transmission over optical fiber lines, determine the physical properties of molecules in samples, and the like. The identification of sample properties using frequency pulses is based on the duration and stability of the pulses at the desired frequencies to obtain a specific sample resolution. Typically, interferometric measurements are used for optical analysis of samples. However, interferometric measurements usually lead to a decrease in resolution in space and time due to limitations in pulse duration, pulse repetition rate, spectrum range, and the like. The use of optical frequency pulses to transmit information uses a relatively wide bandwidth of individual frequency pulses, which results in pulse overlap at long transmission distances. It is understood that when the frequency pulses propagate along the fiber optic line, the pulse width increases. After a certain distance, overlapping frequency lines due to increased pulse width results in a loss of digital content. In addition, it is difficult to generate many different closely spaced frequencies, which limits the signal resolution when sending optical frequency pulses.

The essence of the invention

[0004] In one embodiment of the invention, a system is provided for polling one or more parameters at multiple locations in a sample. The system comprises a first ultrafast laser source and a second ultrafast source configured to deliver a first plurality of pulses and a second plurality of pulses, respectively, in a picosecond time range or a range of shorter durations. In addition, the first and second ultrafast laser sources are configured to supply frequency combs having first and second repetition rates, respectively, where the second repetition rate is different from the first repetition rate. In addition, the first plurality of pulses interact with the sample at multiple locations in the sample to obtain processed pulses. In addition, the system comprises a reference device configured to supply reference pulses having a variable time delay, a variable phase delay, a variable optical path length difference, or a combination thereof. In addition, the system comprises a detector unit configured to detect at least a portion of the processed pulses from the first ultrafast laser source, a second plurality of pulses from the second ultrafast laser source, and reference pulses. The system also contains a data processing unit configured to process the detected pulses and perform measurements of one or more parameters for multiple locations in the sample.

[0005] In another embodiment, the invention provides a system for polling one or more parameters at multiple locations in a sample. The system comprises a first femtosecond laser source and a second femtosecond laser source configured to deliver a first plurality of pulses and a second plurality of pulses, respectively, in a picosecond time range or a range of shorter durations. In addition, the first and second femtosecond laser sources are configured to supply frequency combs having first and second repetition rates, respectively, where the second repetition rate is different from the first repetition rate. In addition, the first plurality of pulses interact with the sample at multiple locations in the sample to obtain processed pulses. The system also includes a reference device configured to supply reference pulses having a variable time delay, a variable phase delay, a variable path difference, or a combination thereof. In addition, the system comprises a detector unit configured to detect at least a portion of the processed pulses from the first femtosecond laser source, the second plurality of pulses from the second femtosecond laser source, and reference pulses. In addition, the system includes a data processing unit configured to process the detected pulses and perform measurements of one or more parameters for multiple locations in the sample.

[0006] In yet another embodiment of the invention, the method includes supplying a first plurality of pulses in a picosecond or shorter duration range and a frequency comb having a first repetition rate. In addition, the method includes interacting a portion of the first plurality of pulses at multiple locations in the sample to produce processed pulses. The method also includes injecting a variable time delay, a variable phase delay, a variable path difference, or combinations thereof into another portion of the first plurality of pulses to obtain reference pulses, and supplying a second plurality of pulses in a picosecond or shorter duration range, and a frequency comb, having a second repetition rate that is different from the first repetition rate. In addition, the method includes detecting at least a portion of the processed pulses from the first ultrafast laser source, the second plurality of pulses from the second ultrafast laser source, and reference pulses. The method also includes processing the detected pulses to perform measurements of one or more parameters for multiple locations in the sample.

List of drawings

[0007] These and other distinctive features and aspects of the embodiments of the invention will become better understood upon reading the following detailed description with reference to the accompanying drawings, in which like symbols represent like parts throughout the drawings, and in which:

[0008] FIG. 1 is a schematic diagram of a system for distributed sample measurement for interrogating one or more parameters at multiple locations in a sample in accordance with aspects of the specification.

[0009] FIG. 2 (a) -2 (i) are graphical illustrations of distributed measurements using the system of FIG. 1 in accordance with aspects of the specification.

[0010] FIG. 3 is a schematic diagram of a system for distributed long-distance measurements at multiple locations in a sample in accordance with aspects of the disclosure.

[0011] FIG. 4 is an example flowchart for distributed measurements for multiple locations in a sample.

Detailed description

[0012] In some embodiments, systems and methods are provided for the distributed measurement of one or more sample parameters. In some other forms of implementation of the description, distributed measurement of absorption, transmission, reflectance, phase spectrum, or combinations can be used to determine one or more parameters, but not limited to them, such as concentration, pressure, temperature and chemical composition at one or more locations in the sample. Additionally, in some embodiments of the invention, the systems may be configured to perform short-range distributed measurements, long-range distributed measurements, or both. In one example, a distributed measurement can be performed on a sample to determine the chemical composition of the sample at two or more locations in the sample. In another embodiment, the distributed measurement can be performed to determine the temperature of the sample at two or more locations in the sample.

[0013] In some embodiments of the invention, the systems and methods may be used for multiparameter measurement with high spatial resolution along with wavelength resolution. For example, the systems and methods can be used for spatial profiling of gas, oil, water, or combinations thereof in downhole systems, measuring gas concentration in space, for example, in the exhaust of a gas turbine, monitoring the condition of coatings such as thermal barrier coatings on turbine blades, but not limited to this.

[0014] In some embodiments, a system is provided for distributed measurement of a sample to interrogate or examine one or more parameters at multiple locations in the sample. The system comprises a first ultrafast laser source configured to supply a frequency comb having a first repetition rate. The first ultrafast laser source is configured to deliver the first plurality of pulses in the picosecond time range or in the range of shorter durations to interact with one or more locations from a plurality of sample locations to obtain processed pulses. The system also includes a second ultrafast laser source that is configured to provide a comb of frequencies with a second repetition rate that is different from the first repetition rate. The second ultrafast laser source is configured to deliver the second plurality of pulses in the picosecond time range or in the range of shorter durations. The difference between the repetition rates of the first and second ultrafast laser sources can be based on a system parameter. In addition, the difference between the repetition rates of the first and second ultrafast laser sources determines the range of the spectrum that can be measured. For example, if the difference in repetition rates is below a certain value, the measured spectrum range may be narrower than the range of the spectrum that is measured if the difference in repetition rates is above a certain value.

[0015] The system also comprises a detector unit that is configured to detect at least a portion of the processed pulses and at least a portion of the second plurality of pulses. In addition, the system includes a data processing unit configured to process the detected pulses and perform measurements of one or more parameters corresponding to multiple locations in the sample.

[0016] In some embodiments, the methods and systems can be used to perform a distributed measurement of a variety of parameters to help optimize operations such as, but not limited to, gas turbine operation. For example, distributed measurement of multiple parameters facilitates the identification of hot spots in a gas turbine, reduction of harmful emissions from a gas turbine, detection of impurities in thermal barrier materials of turbine blades, etc., or combinations thereof. In addition, the methods and systems can provide measurements for samples having one or more phases, such as two or more of a solid, liquid and gaseous phase. The systems and methods are configured to measure high-resolution broadband spectrum and are used in environmental studies where samples can be in one or more phases such as solid, liquid and gaseous phases. In addition, the methods and systems use synchronized ultrafast laser sources that provide distributed measurements over long distances.

[0017] FIG. 1 illustrates an example of a system for distributed sample measurement for polling one or more parameters at multiple locations in the sample. In the illustrated embodiment, system 100 comprises an interferometric configuration that uses a sample arm and a support arm. The term "sample arm" is used to refer to a shoulder or portion of system 100 that includes a sample, and the term "support arm" is used to refer to a shoulder or portion of system 100 that includes a support device.

[0018] In the illustrated embodiment, the system 100 comprises a first ultrafast laser source 102, a second ultrafast laser source 104, and a reference device 110. The first and second ultrafast laser sources 102 and 104 are configured to deliver a first and second plurality of pulses, respectively. The first and second ultrafast laser sources 102 and 104 are characterized by their individual frequency combs and repetition rates. The reference device 110 is operatively coupled to the first laser source 102 and is configured to provide reference pulses that have a time delay, phase delay, or optical path difference relative to the pulses of the first laser source 102.

[0019] In one embodiment, the frequency difference between the first and second ultrafast laser sources 102 and 104 may be greater than the line width of some predetermined comb line of the ultrafast laser sources 102 and 104. In addition, the frequency difference between the first and second ultrafast laser sources 102 and 104 may be less than half the repetition rate of ultrafast laser sources 102 and 104.

[0020] In some examples, ultrafast laser sources 102 and 104 may be pico or femtosecond laser sources. The use of pico or femtosecond laser sources in the system 100 results in relatively higher spatial resolution compared to the use of laser sources that emit optical pulses with durations exceeding picoseconds. The repetition rates of the first and second ultrafast laser sources 102 and 104 are different. In one example, the repetition rate of the first ultrafast laser source 102 is referred to as the “first repetition rate” and the repetition rate of the second ultrafast laser source 104 is referred to as the “second repetition rate” (fr +/- df). In particular, the first and second repetition rates are different. The difference in the repetition rates of the first and second ultrafast laser sources 102 and 104 is represented by the value df, where df is a ratio that represents the spatial distribution of the laser pulse duration for a particular ultrafast laser source repetition rate. The repetition rate can be determined based on the required spectral resolution. In one embodiment, df can be represented by equation (1) as:

where c represents the speed of light and fr represents the repetition rate of the first ultrafast laser source 102.

[0021] It can be noted that optical paths for multiple pulses from ultrafast laser sources 102 and 104 may be formed with or without optical fibers. In one embodiment, the optical fiber may be operatively coupled to the first ultrafast laser source 102 such that at least a portion of the first plurality of pulses pass through at least a portion of the optical fiber. In the same or other embodiments, the optical fiber may be operatively coupled to the second ultrafast laser source 104 such that at least a portion of the second plurality of pulses pass through at least a portion of the optical fiber. In some embodiments, in the optical configuration of FIG. 1 and 3 of this application, the first, second and / or third plurality of pulses from the first, second and / or third ultrafast laser sources 302, 304 and 306, respectively, can pass through the surrounding atmosphere (eg, air) or optical fiber. In embodiments where a different plurality of pulses pass through an optical fiber, the interconnect lines between the various components of systems 100 and 300 may be optical fibers.

[0022] The first ultrafast laser source 102 is operatively associated with a reference device 110. As a non-limiting example, the reference device 110 may be a time delay device such as a mirror. Other non-limiting examples of reference devices may include phase difference or delay generators, path difference generators, liquid crystal devices, microarrays, Micro Electro Mechanical System (MEMS), or any other optical structure that is configured to introduce a time delay, phase delay. or a phase difference, or a difference in optical path lengths into an optical path, for example, in system 100. The support arm, generally represented by reference numeral 112, comprises a support device 110, such as a support mirror. In addition, the sample arm, generally represented by reference numeral 114, contains the sample 108 and an optical path that leads to the sample 108. The reference device 110 is configured to provide a time delay between the optical pulses propagating in the reference arm 112 and the optical pulses propagating in arm 114 with the sample to create the necessary interference between the pulses in the two arms 112 and 114.

[0023] In some embodiments, the reference device may be configured to introduce a time delay, delay, or phase difference, or optical path length difference to a portion of the first plurality of pulses delivered by the first ultrafast laser source 102. In addition, the time delay, phase or the difference in optical path lengths can vary over time. In particular, the time delay, phase delay, path difference introduced by the reference device 110 into a portion of the first plurality of pulses are such that these delays and differences can vary according to the location in the sample to be interrogated. By way of example, in the illustrated embodiment, if the support device 110 is a time delay device such as a mirror, the mirror may be movable along the optical path represented by the reference numeral 111 to introduce a variable delay time into the path of a portion of the first plurality pulses from the first ultrafast laser source 102. This part of the first plurality of pulses is called reference pulses. In addition, the speed or frequency of movements of the time delay device can be adjusted based on the desired scan speed at which it is necessary to scan various locations of the sample 108. In addition, the time delay, phase delay, or travel difference introduced by the reference device 10 can be adjusted to correspond the spatial resolution of the sample 108. It can be noted that the minimum spatial resolution for scanning the sample 108 may be similar to the pulse width of the laser sources 102 and 104.

[0024] The system further comprises beamsplitter 116 and 117. In a non-limiting example, beamsplitter 116 may be, for example, a 50:50 beamsplitter. The beam splitter 116 is configured to divide the radiation propagating from the first ultrafast laser source 102 into at least 2 parts so that the first part of the radiation passes to the support device 110 and the second part of the radiation passes to the sample 108. In addition, as in the reference collimators 120 and 122 can be used in arm 112 and sample arm 114. Collimators 120 and 122 may be similar in function and structure, or may be different. The collimator 120 collimates and directs the radiation to the reference device 110; the delayed radiation from the reference device 110 is received back by the collimator 120. Likewise, collimator 122 collimates and directs radiation towards sample 108 to interact the radiation with at least a portion of sample 108 and to collect processed pulses or interacting pulses.

[0025] During operation, a portion of the reference pulses, such as time-delayed pulses, from the first ultrafast laser source 102 may interact with one or more sample locations at a given time. Sample locations 130, 132, 134, and 136 are interrogated or probed based on the refractive index of the sample medium 108. In one example, where the reference device 110 is a time delay device such as a reference mirror, the distance the reference mirror travels along an optical path that extends along the direction 111 can determine the amount of optical delay or travel difference introduced into the sample arm, or both. In one embodiment of the invention, the reference mirror may be connected to a motor (not shown in FIG. 1) to effect movement of the mirror. In other examples, when a piezoelectric device or a MEMS mirror is used as the reference device 110, electric current may be supplied to the reference device to effect the required movement of the reference device 110 to provide an appropriate time delay or phase delay at a particular point in time.

[0026] Interacting pulses from the sample 108 in the sample arm 114 and reference (eg, time-delayed) pulses from the reference arm 112 may interfere with pulses from the second ultrafast laser source 104. This pulse interference is detected using the detector 124. In one example, the detector unit 124 may be an RF detector.

[0027] In addition, the system uses a processing unit 128 to process the combined radiation received at the detector unit 124. As used herein, the term "data processing unit" refers to a processor having integrated circuits incorporated into a computer, as well as a controller, microcontroller, microcomputer, Programmable Logic Controller (PLC), specialized microprocessors, digital signal processing (Digital Signal Processor, DSP), Application Specific Integrated Circuit (ASIC), Field Programmable Gate Array (FPGA), and / or any other programmable circuitry. In some embodiments, processing unit 128 may be associated with or may contain memory (s) (not shown in FIG. 1). Memory device (s) may typically comprise memory element (s) including, but not limited to, a computer-readable medium (for example, random access memory (RAM), computer-readable non-volatile medium (for example, flash memory), one or multiple hard disks, a floppy disk, a Compact Disk-Read Only Memory (CD-ROM), a Compact Disk-Read / Write (CD-R / W) , Magneto-Optical Disk (MOD), Digital Versatile Disc (DVD), flash drives, optical disk drives, semiconductor memory devices and / or other suitable memory elements. Detected radiation processed by processing unit 128 data, may provide data that represent distributed measurements of one or more sample parameters, as described further in Fig. 2 (a) -2 (h). In addition, the method of operation of the system 100 by f ig. 1 will be described with reference to FIG. 2 (a) -2 (h).

[0028] FIG. 2 (a) -2 (h) show the interference of pulses from a reference arm, eg, reference arm 112 in FIG. 1, and a sample arm, such as a sample arm 114 in FIG. 1. In FIG. 2 (a) -2 (f), ordinate 202 represents the intensity of the optical pulses. In addition, in FIG. 2 (a) -2 (f) abscissa 204 represents time, in FIG. 2 (g) -2 (h), the abscissa 206 represents the pulse frequency and the ordinate 208 represents the amplitude of the pulses. In particular, FIG. 2 (a) represents the reference pulses (I _R ) or pulses from the reference arm 112. At a certain point in time, the position of the reference device 110, such as the location of the time delay device along the direction 111, is selected such that one or more sample locations in a particular location (or depth) along the optical path. FIG. 2 (b) represents the pulses ( _IS ) from the sample arm 114 that correspond to sample locations X1, X2, X3 and X4 shown in FIG. 1 by reference numerals 130, 132, 134 and 136, respectively. In particular, pulses that return after interacting with sample position X1 130 are indicated by reference numerals 212, and pulses returning from sample position X2 132 are indicated by reference numerals 214. Similarly, pulses returning from sample positions X3 134 and X4 136 are indicated reference numerals 216 and 218. It should be noted that the sample 108 may have less or more than 4 locations that need to be detected for distributed measurement.

[0029] FIG. 2 (c) represents a second plurality of pulses 210 that are received from a second ultrafast laser source 104. FIG. 2 (d) represents the combined pulses from the reference device 110, sample 108, and pulses from the second ultrafast laser source 104 in the detector unit 124. In particular, FIG. 2 (d) is the summation of the reference pulses (I _R ) from the reference arm 112, the second plurality of pulses from the second ultrafast laser source 104 and the processed or interacting pulses from multiple locations such as locations X1, X2, X3, X4 130-136 in sample 108; these impulses have the ability to interfere. In one embodiment, the detector unit 124 is configured to perform non-linear operations to obtain an interferogram signal (I _D ) as shown in equation (2) below:

where I _D is the interferogram signal, I _R are the reference pulses from the reference arm, Is are the pulses from the sample arm, and I _L is the second plurality of pulses from the second ultrafast laser source 104.

[0030] Multiplication of pulses from different locations X1, X2, X3, X4, 130-136 and pulses (I _R) from the reference arm 112 causes the signals other than those signals that have the same path length as the pulses from the reference shoulder 112, decrease to zero. Accordingly, as shown in FIG. 2 (e), when the support is moved such that the length of the support path overlaps with the signals from X1 130, the interferogram signal ( _ID ) includes an interferogram of the signal from location X1 130 in sample 108. Similarly generated interferogram signals for X2 132 are shown in FIG. ... 2 (e). In addition, signal interferograms from other locations X3 and X4, 134 and 136, may be obtained by adjusting the reference device 110 appropriately, such as by moving the reference mirror.

[0031] FIG. 2 (g) -2 (h) show the Fourier transform of the interferogram signals corresponding to positions XI 130 and X2 132. Accordingly, the pulses indicated by reference numerals 230 and 232 represent the Fourier transforms of signals from the positions XI and X2 of the sample. Fourier transforms, such as Fourier transforms 230 and 232, are used to generate an absorption profile of the sample 108 corresponding to these locations in the sample, as shown in FIG. 2 (i). Equation (3) represents the absorption profile at X2 as:

where, A (z) denotes the absolute value of the absorbance at the z-site in the sample and C (z) denotes the accumulated absorbance at the z-site, and C (z-Δz) denotes the accumulated absorbance at the z-Δz site where the z-Δz site is immediately in front of place n in the path of optical pulses. For example, if z represents site X2, z-Δz may represent site X1. The absorption profile shown in FIG. 2 (i) contains a peak 244 and has an abscissa 240, which represents the wavelength, and an ordinate 242, which represents the absorption values. In some embodiments, the height, width, and position of a peak, such as peak 244 in an absorption profile, can be used to measure various parameters such as, but not limited to, temperature, pressure, concentration, composition, and the like. In the example shown, the height 246 of peak 244 represents the concentration of a particular substance or the concentration of sample 108 as a whole. In addition, the width 248 and position 250 of peak 244 represent, respectively, the temperature and pressure of the sample 108 at that particular location. Distributed measurements can be performed at multiple locations in the sample with a spatial resolution that is proportional to the pulse width of ultrafast laser sources 102 and 104.

[0032] In some embodiments, system 100 is configured for short-range measurements in the range of about 100 microns to several centimeters and for long-range measurements in the range of about a few centimeters to several kilometers. Additionally, in some other embodiments, the system 100 is usable up to about c / fr of the laser, where c is the speed of light and fr is the repetition rate of the ultrafast laser source. In some other embodiments, the systems and methods of this application can be configured for distributed measurements over long distances, such as oil and gas pipelines.

[0033] FIG. 3 illustrates another example of a system 300 for distributed measurements of multiple locations in a sample. In addition, the system 300 is configured for long-range measurements, such as downhole applications, spatial profiling of gas, oil, water in downhole systems, spatial measurement of gas concentration in the exhaust of a gas turbine, and monitoring the health of coatings such as, but not limited to, thermal barrier coatings on turbine blades. System 300 includes first, second, and third ultrafast laser sources 302, 304, and 306 configured to deliver a first, second, and third plurality of pulses. In a non-limiting example, the first, second and third ultrafast laser sources 302, 304 and 306 are femtosecond laser sources. In some embodiments, ultrafast laser sources 302, 304, and 306 may be operatively coupled to other components of system 300 through one or more optical fibers. In one embodiment, the optical fiber may be operatively coupled to the first ultrafast laser source 302 such that at least a portion of the first plurality of pulses pass through at least a portion of the optical fiber.

[0034] In addition, ultrafast laser sources 302 and 306 are operatively coupled to a clock reference generator 308 to synchronize the two sources 302 and 306 with respect to each other. In addition, a reference device, such as a phase delay generator 310, is coupled to one of the first and third ultrafast laser sources 302 and 306. In the current example where the phase delay generator 310 is coupled to the third ultrafast laser source 306, the delay phase input by the phase delay generator 310 into the third plurality of pulses of the third ultrafast laser source 306 in turn introduces a phase delay into the reference clock generator 308. In addition, the phase delay introduced in the third plurality of pulses by the phase delay generator 310 results in a time delay introduced in the third plurality of pulses with respect to the first plurality of pulses from the first ultrafast laser source 302. The third ultrafast laser source 306 in conjunction with the generator 308 the reference sync pulse acts as a reference arm for sending reference pulses.

[0035] In operation, the first plurality of pulses from the first ultrafast laser source 302 are passed through the circulator 312, and a portion 315 of the first plurality of pulses that are passed through the circulator 312 is used to interrogate the sample 314. The collimator 316 is used to collimate the pulses 315 passing through the circulator 312 to sample 314. Various sample locations in the direction 326 of pulses from collimator 316 are designated XI 318, X2 320, X3 322 and X4 324. After interacting with sample 314, the interacting pulses are combined with a third set of pulses using a combiner 328. The combined pulses are then additionally are combined with the second plurality of pulses from the second ultrafast laser source 304 using another combiner 330 to generate the resulting pulses. The repetition rates of the first and third ultrafast laser sources 302 and 306 are the same. In addition, the repetition rates of the first and third ultrafast laser sources 302 and 306 are relatively different from the repetition rate of the second source 304.

[0036] The resulting pulses are detected by the detector unit 332 and processed using the data processing unit 334. Results such as those shown in FIG. 2 (a) -2 (i) may be displayed on a display 336 such as a monitor, a touch screen, and the like.

[0037] FIG. 4 illustrates an example flowchart 400 of a method for distributed measurement at multiple locations in a sample to determine one or more sample parameters. At 402, the method begins with a first plurality of pulses in a picosecond or shorter time range and a comb of frequencies having a first repetition rate. At 404, a portion of the first plurality of pulses is able to interact at multiple locations in the sample to obtain processed pulses. In step 406, a variable time delay, a variable phase delay, a variable path difference, or combinations thereof, are input to another portion of the first plurality of pulses to generate reference pulses. At 408, a second plurality of pulses in a picosecond or shorter time range and a comb of frequencies are provided having a second repetition rate. The second repetition rate is different from the first repetition rate.

[0038] In step 410, at least a portion of the processed pulses from the first ultrafast laser source, the second plurality of pulses from the second ultrafast laser source, and the reference pulses are detected by the detector. At block 412, the detected pulses are processed to perform measurements of one or more parameters for multiple locations in the sample.

[0039] In some embodiments, a third plurality of pulses may also be provided. In these embodiments of the invention, a time delay, phase delay, or path difference may be introduced into one of the first or third plurality of pulses. In addition, the first and third sets of pulses can be synchronized. In addition, the pulses to be processed can be combined with a third plurality of pulses.

[0040] Systems 100 and 300 of FIG. 1 and 3 and the methods of FIG. 2 (a) -2 (i) and FIG. 4 are configured to detect many substances. As an example, when interrogating a gaseous sample, various gases present in the gaseous sample can be detected using the systems and methods of this application. The systems and methods of this application provide high resolution and faster measurement. High-resolution probing allows multiple materials to be identified simultaneously. In addition, the systems and methods of this application provide a full optical spectrum for determining a variety of parameters, rather than having to measure these parameters individually. In addition, the broadband and coherent output of the frequency combs also provides high signal-to-noise ratios. Also, the short pulse durations of ultrafast lasers provide high spatial resolution.

[0041] Although only a few features of the invention have been illustrated and described herein, many modifications and variations can be suggested by those skilled in the art. Therefore, it should be understood that the appended claims are intended to cover all such modifications and variations that fall within the scope of the invention.

Claims (33)

1. A system (100) for polling one or more parameters at multiple locations in a sample (108), comprising: a first ultrafast laser source (102) configured to deliver a first plurality of pulses in a picosecond time range or a range of shorter durations, the first ultrafast laser source (102) configured to supply a comb of frequencies having a first repetition rate, the first plurality of pulses interacting with a sample (108) at a plurality of locations in the sample (108) to obtain processed pulses; a second ultrafast laser source (104) configured to deliver a second plurality of pulses in a picosecond or shorter time range, the second ultrafast laser source (104) configured to supply a comb of frequencies having a second repetition rate that is different from the first repetition rate; a reference device (110) configured to supply reference pulses having a variable time delay, a variable phase delay, a variable path difference, or combinations thereof; a detector unit (124), configured to detect at least a portion of the processed pulses from the first ultrafast laser source (102), a second plurality of pulses from the second ultrafast laser source (104), and reference pulses; and a data processing unit (128), configured to process the detected pulses and perform measurements of one or more parameters for multiple locations in the sample (108). 2. System (100) according to claim 1, wherein the first ultrafast laser source, the second ultrafast laser source, or both are made in the form of a femtosecond laser source. 3. The system (100) of claim. 1, in which the reference device (110) is made in the form of a time delay device, a phase difference generator, or a path difference generator, or a combination thereof. 4. The system (100) of claim 3, wherein the time delay device is a mirror. 5. The system (100) of claim 1, further comprising a third ultrafast laser source (306) configured to deliver a third plurality of pulses. 6. System (100) according to claim 5, further comprising a reference clock generator (308) operatively associated with the first and third ultrafast laser sources (302, 306) to synchronize the first and third ultrafast sources. 7. System (100) according to claim 6, further comprising a phase difference generator operatively coupled to the third ultrafast laser source (306). 8. The system (100) of claim 5, further comprising a circulator (312) operatively coupled to the first ultrafast laser source (102) for directing at least a portion of the interacting pulses such that the interacting pulses are combined with the third plurality of pulses. 9. The system (100) of claim 1, further comprising an optical fiber operably coupled to the first ultrafast laser source (102) such that at least a portion of the first plurality of pulses pass through at least a portion of the optical fiber. 10. The system (100) of claim 1, further comprising an optical fiber operatively coupled to the second ultrafast laser source (104) such that at least a portion of the second plurality of pulses pass through at least a portion of the optical fiber. 11. The system (100) of claim 1, wherein the support device (110) is made in the form of a liquid crystal device, a microarray, a microelectromechanical system (MEMS), or an optical structure that is configured to introduce a time delay, phase delay, or optical path length difference ... 12. System (100) for polling one or more parameters at multiple locations in the sample (108), comprising: a first femtosecond laser source (102) configured to supply a first plurality of pulses in a picosecond time range or a range of shorter durations, the first femtosecond laser source (102) configured to supply a comb of frequencies having a first repetition rate; wherein the first plurality of pulses interact with the sample (108) at multiple locations in the sample (108) to obtain processed pulses; a second femtosecond laser source (104) configured to deliver a second plurality of pulses in a picosecond or shorter time range, the second femtosecond laser source (104) configured to supply a comb of frequencies having a second repetition rate that is different from the first repetition rate; a reference device (110) configured to supply reference pulses having a variable time delay, a variable phase delay, a variable path difference, or combinations thereof; a detector unit (124) configured to detect at least a portion of the processed pulses from the first femtosecond laser source (102), a second plurality of pulses from the second femtosecond laser source (104), and reference pulses; and a data processing unit (128), configured to process the detected pulses and perform measurements of one or more parameters for multiple locations in the sample. 13. The system (100) of claim 12, further comprising a third femtosecond laser source. 14. The system (100) of claim 12, wherein the reference device (110) is operatively coupled to the first femtosecond laser source. 15. System (100) according to claim 12, further comprising a collimator located between the first femtosecond laser source and at least part of the sample. 16. The system (100) of claim 12, further comprising an optical fiber operably coupled to the first femtosecond laser source such that at least a portion of the first plurality of pulses pass through at least a portion of the optical fiber. 17. A method (400) for polling one or more parameters at multiple locations in a sample, comprising: supplying a first plurality of pulses in a picosecond time range or a range of shorter durations, the first plurality of pulses having a first repetition rate (402); interacting a portion of the first plurality of pulses at multiple locations in the sample to obtain processed pulses (404); introducing a variable time delay, variable phase delay, variable path difference, or combinations thereof into another part of the first set of pulses to obtain reference pulses (406); supplying a second plurality of pulses in a picosecond time range or a range of shorter durations, the second plurality of pulses having a second repetition rate that is different from the first repetition rate (408); detecting at least a portion of the processed pulses from the first ultrafast laser source, the second plurality of pulses from the second ultrafast laser source, and reference pulses (410) and processing detected pulses to perform measurements of one or more parameters for multiple locations in the sample (412).

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