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Strycker BD. The Strehl ratio as a phase histogram. Appl Opt 2023; 62:5035-5041. [PMID: 37707282 DOI: 10.1364/ao.493726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Accepted: 05/30/2023] [Indexed: 09/15/2023]
Abstract
It is shown that the Strehl ratio can always be written as an integral over an apodization-weighted phase histogram. The corresponding mathematical formalism, based on Federer's co-area formula, is enumerated, and a practical numerical method to quickly and accurately calculate apodization-weighted phase histograms is detailed and compared with similar methods. Conditions for expressing the Strehl ratio as a product S=S 1 S 2 are investigated.
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Strycker BD. Zernike-like Laguerre-Gaussian orthonormal polynomials for optical field reconstruction. Opt Lett 2022; 47:6137-6140. [PMID: 37219191 DOI: 10.1364/ol.475979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Accepted: 10/31/2022] [Indexed: 05/24/2023]
Abstract
Analytic closed form expressions for orthonormal polynomials exhibiting both rotational and Gaussian symmetries are derived for both circular and elliptical geometries. They exhibit a close correspondence to the Zernike polynomials but are of Gaussian shape and orthogonal over the (x,y) plane. Consequently, they may be expressed in terms of Laguerre polynomials. Formulas for calculating the centroid of a real function are also presented and, along with the analytic expressions for the polynomials, may prove to be of especial use in reconstruction of the intensity distribution incident on a Shack-Hartmann wavefront sensor.
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Strycker BD, Han Z, Duan Z, Commer B, Wang K, Shaw BD, Sokolov AV, Scully MO. Identification of toxic mold species through Raman spectroscopy of fungal conidia. PLoS One 2020; 15:e0242361. [PMID: 33227000 PMCID: PMC7682877 DOI: 10.1371/journal.pone.0242361] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 10/30/2020] [Indexed: 02/08/2023] Open
Abstract
We use a 785 nm shifted excitation Raman difference (SERDS) technique to measure the Raman spectra of the conidia of 10 mold species of especial toxicological, medical, and industrial importance, including Stachybotrys chartarum, Penicillium chrysogenum, Aspergillus fumigatus, Aspergillus flavus, Aspergillus oryzae, Aspergillus niger, and others. We find that both the pure Raman and fluorescence signals support the hypothesis that for an excitation wavelength of 785 nm the Raman signal originates from the melanin pigments bound within the cell wall of the conidium. In addition, the major features of the pure Raman spectra group into profiles that we hypothesize may be due to differences in the complex melanin biosynthesis pathways. We then combine the Raman spectral data with neural network models to predict species classification with an accuracy above 99%. Finally, the Raman spectral data of all species investigated is made freely available for download and use.
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Affiliation(s)
- Benjamin D. Strycker
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, Texas, United States of America
- Baylor University, Waco, Texas, United States of America
| | - Zehua Han
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, Texas, United States of America
| | - Zheng Duan
- Center for Optical and Electromagnetic Research, South China Academy of Advanced, Optoelectronics, South China Normal University, Guangzhou, China
| | - Blake Commer
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, Texas, United States of America
| | - Kai Wang
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, Texas, United States of America
| | - Brian D. Shaw
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, Texas, United States of America
| | - Alexei V. Sokolov
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, Texas, United States of America
- Baylor University, Waco, Texas, United States of America
| | - Marlan O. Scully
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, Texas, United States of America
- Baylor University, Waco, Texas, United States of America
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Han Z, Strycker BD, Commer B, Wang K, Shaw BD, Scully MO, Sokolov AV. Molecular origin of the Raman signal from Aspergillus nidulans conidia and observation of fluorescence vibrational structure at room temperature. Sci Rep 2020; 10:5428. [PMID: 32214112 PMCID: PMC7096407 DOI: 10.1038/s41598-020-62112-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Accepted: 03/03/2020] [Indexed: 11/24/2022] Open
Abstract
Successful approaches to identification and/or biological characterization of fungal specimens through Raman spectroscopy may require the determination of the molecular origin of the Raman response as well as its separation from the background fluorescence. The presence of fluorescence can interfere with Raman detection and is virtually impossible to avoid. Fluorescence leads to a multiplicity of problems: one is noise, while another is “fake” spectral structure that can easily be confused for spontaneous Raman peaks. One solution for these problems is Shifted Excitation Raman Difference Spectroscopy (SERDS), in which a tunable light source generates two spectra with different excitation frequencies in order to eliminate fluorescence from the measured signal. We combine a SERDS technique with genetic breeding of mutant populations and demonstrate that the Raman signal from Aspergillus nidulans conidia originates in pigment molecules within the cell wall. In addition, we observe unambiguous vibrational fine-structure in the fluorescence response at room temperature. We hypothesize that the vibrational fine-structure in the fluorescence results from the formation of flexible, long-lived molecular cages in the bio-polymer matrix of the cell wall that partially shield target molecules from the immediate environment and also constrain their degrees of freedom.
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Affiliation(s)
- Zehua Han
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, Texas, USA.
| | - Benjamin D Strycker
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, Texas, USA. .,Baylor University, Waco, Texas, USA.
| | - Blake Commer
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, Texas, USA
| | - Kai Wang
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, Texas, USA
| | - Brian D Shaw
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, Texas, USA
| | - Marlan O Scully
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, Texas, USA.,Baylor University, Waco, Texas, USA
| | - Alexei V Sokolov
- Institute for Quantum Science and Engineering, Texas A&M University, College Station, Texas, USA. .,Baylor University, Waco, Texas, USA.
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Springer MM, Strycker BD, Wang K, Sokolov AV, Scully MO. Femtosecond Laser Filaments for Use in Sub-Diffraction-Limited Imaging and Remote Sensing. J Vis Exp 2019. [PMID: 31081804 DOI: 10.3791/58207] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Probing remote matter with laser light is a ubiquitous technique used in circumstances as diverse as laser-induced breakdown spectroscopy and barcode scanners. In classical optics, the intensity that can be brought to bear on a remote target is limited by the spot size of the laser at the distance of the target. This spot size has a lower bound determined by the diffraction limit of classical optics. However, amplified femtosecond laser pulses generate intensity sufficient to modify the refractive index of the ambient air and undergo self-focusing. This self-focusing effect leads to the generation of highly intense laser filaments which maintain their intensity and small sub-millimeter diameter size at distances well beyond the classical Rayleigh length. Such intensity provides the capability of remote scanning, imaging, sensing, and spectroscopy with enhanced spatial resolution. We describe a technique for generating filaments with a femtosecond regenerative chirped-pulse amplifier, and for using the resulting filament to conduct imaging and spectroscopic measurements at remote distances of at least several meters.
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Strycker BD, Springer MM, Traverso AJ, Kolomenskii AA, Kattawar GW, Sokolov AV. Femtosecond-laser-induced shockwaves in water generated at an air-water interface. Opt Express 2013; 21:23772-23784. [PMID: 24104289 DOI: 10.1364/oe.21.023772] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We report generation of femtosecond-laser-induced shockwaves at an air-water interface by millijoule femtosecond laser pulses. We document and discuss the main processes accompanying this phenomenon, including light emission, development of the ablation plume in the air, formation of an ablation cavity, and, subsequently, a bubble developing in water. We also discuss the possibility of remotely controlling the characteristics of laser-induced sound waves in water through linear acoustic superposition of sound waves that results from millijoule femtosecond laser-pulse interaction with an air-water interface, thus opening up the possibility of remote acoustic applications in oceanic and riverine environments.
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Strycker BD, Wang K, Springer M, Sokolov AV. Chemical-specific imaging of shallowly buried objects using femtosecond laser pulses. Appl Opt 2013; 52:4792-4796. [PMID: 23852190 DOI: 10.1364/ao.52.004792] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Accepted: 05/07/2013] [Indexed: 06/02/2023]
Abstract
We demonstrate that objects buried in sand (1 to 4 mm deep) may be selectively imaged according to their chemical composition through spectral analysis of the laser-induced breakdown signal. The signal is generated by loosely focused femtosecond laser pulses having energies ranging from 0.5 to 2.5 mJ. We determine the depth from which a spectral signal may be measured as a function of pulse energy. Having in mind applications to remote sensing, chemical-specific imaging of shallowly buried objects may find use in various fields ranging from space exploration to landmine detection.
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Affiliation(s)
- B D Strycker
- Institute for Quantum Science and Engineering, Department of Physics and Astronomy, Texas A&M University, College Station, Texas 77843-4242, USA.
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Wang K, Strycker BD, Voronine DV, Jha PK, Scully MO, Meyers RE, Hemmer P, Sokolov AV. Remote sub-diffraction imaging with femtosecond laser filaments. Opt Lett 2012; 37:1343-1345. [PMID: 22513680 DOI: 10.1364/ol.37.001343] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Achieving super-resolution has become a scientific imperative for remote imaging of objects and scenes needing increased detail and has motivated the development of various laser-based techniques. We demonstrate a scheme which achieves subdiffraction imaging of remote objects by using femtosecond laser filaments. The use of laser filaments for imaging is destined to have applications in many environments.
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Affiliation(s)
- Kai Wang
- Institute for Quantum Science and Engineering, Department of Physics and Astronomy, Texas A&M University, College Station, Texas 77843-4242, USA.
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Strycker BD, Springer M, Trendafilova C, Hua X, Zhi M, Kolomenskii AA, Schroeder H, Strohaber J, Schuessler HA, Kattawar GW, Sokolov AV. Energy transfer between laser filaments in liquid methanol. Opt Lett 2012; 37:16-18. [PMID: 22212776 DOI: 10.1364/ol.37.000016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We demonstrate energy exchange between two filament-forming femtosecond laser beams in liquid methanol. Our results are consistent with those of previous works documenting coupling between filaments in air; in addition, we identify an unreported phenomenon in which the direction of energy exchange oscillates at increments in the relative pulse delay equal to an optical period (2.6 fs). Energy transfer from one filament to another may be used in remote sensing and spectroscopic applications utilizing femtosecond laser filaments in water and air.
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Affiliation(s)
- B D Strycker
- Institute for Quantum Studies and Department of Physics and Astronomy, Texas A&M University, 4242 TAMU, College Station, Texas 77843–4242, USA.
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Abstract
We develop a technique for optimizing the phase of broad spectrally-separated frequency sidebands-a "holey" spectrum. We use a source of multiple-order coherent Raman sidebands, obtained by crossing femtosecond pump and Stokes beams in synthetic single-crystal diamond. We combine the sidebands into a single beam and show the phase coherence among the sidebands by investigating the interference between them in groups of three while varying one sideband phase by an acousto-optics pulse shaper. We then show how we optimize the broad "holey" spectrum by overcoming the limited temporal shaping window of the pulse shaper. We also explore how the resultant second harmonic/sum frequency generation of the full combined broadband spectrum varies as we vary different sideband phases. This step-by-step phase optimization of the "holey" spectrum can be applied to sidebands with similar structure to synthesize arbitrary optical waveforms.
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Affiliation(s)
- Miaochan Zhi
- Institute for Quantum Science and Engineering, Department of Physics and Astronomy, Texas A&M University, College Station, TX 77843-4242, USA.
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Abstract
The equivalent absorption path length in an integrating cavity is examined. In an otherwise excellent paper, Tranchart et al. [Appl. Opt. 35, 7070 (1996)] made an important error in obtaining the expressions for the equivalent path length in an integrating cavity. This error has been propagated through several other publications in the literature. Since the equivalent path length is the sine qua non for obtaining an accurate absorption coefficient when using an integrating cavity, it is our intent here to give the correct formulas to prevent further errors when extracting absorption coefficients.
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Affiliation(s)
- Edward S Fry
- Department of Physics and Institute for Quantum Studies, Texas A&M University, College Station, Texas 77843-4242, USA
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Sokolov AV, Naveira LM, Poudel MP, Strohaber J, Trendafilova CS, Buck WC, Wang J, Strycker BD, Wang C, Schuessler H, Kolomenskii A, Kattawar GW. Propagation of ultrashort laser pulses in water: linear absorption and onset of nonlinear spectral transformation. Appl Opt 2010; 49:513-519. [PMID: 20090819 DOI: 10.1364/ao.49.000513] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We study propagation of short laser pulses through water and use a spectral hole filling technique to essentially perform a sensitive balanced comparison of absorption coefficients for pulses of different duration. This study is motivated by an alleged violation of the Bouguer-Lambert-Beer law at low light intensities, where the pulse propagation is expected to be linear, and by a possible observation of femtosecond optical precursors in water. We find that at low intensities, absorption of laser light is determined solely by its spectrum and does not directly depend on the pulse duration, in agreement with our earlier work and in contradiction to some work of others. However, as the laser fluence is increased, interaction of light with water becomes nonlinear, causing energy exchange among the pulse's spectral components and resulting in peak-intensity dependent (and therefore pulse-duration dependent) transmission. For 30 fs pulses at 800 nm center wavelength, we determine the onset of nonlinear propagation effects to occur at a peak value of about 0.12 mJ/cm(2) of input laser energy fluence.
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Affiliation(s)
- Alexei V Sokolov
- Institute for Quantum Studies and Department of Physics, Texas A&M University, 4242 TAMU, College Station, Texas 77843-4242, USA
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Naveira LM, Strycker BD, Wang J, Ariunbold GO, Sokolov AV, Kattawar GW. Propagation of femtosecond laser pulses through water in the linear absorption regime. Appl Opt 2009; 48:1828-1836. [PMID: 19340136 DOI: 10.1364/ao.48.001828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We investigate the controversy regarding violations of the Bouguer-Lambert-Beer (BLB) law for ultrashort laser pulses propagating through water. By working at sufficiently low incident laser intensities, we make sure that any nonlinear component in the response of the medium is negligible. We measure the transmitted power and spectrum as functions of water cell length in an effort to confirm or disprove alleged deviations from the BLB law. We perform experiments at two different laser pulse repetition rates and explore the dependence of transmission on pulse duration. Specifically, we vary the laser pulse duration either by cutting its spectrum while keeping the pulse shape near transform-limited or by adjusting the pulses chirp while keeping the spectral intensities fixed. Over a wide range of parameters, we find no deviations from the BLB law and conclude that recent claims of BLB law violations are inconsistent with our experimental data. We present a simple linear theory (based on the BLB law) for propagation of ultrashort laser pulses through an absorbing medium and find our experimental results to be in excellent agreement with this theory.
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Affiliation(s)
- Lucas M Naveira
- Institute for Quantum Studies and Department of Physics, Texas A&M University, 4242 TAMU, College Station, Texas 77843-4242, USA
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