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Tishchenko A, Geernaert T, Vermeulen N, Berghmans F, Baghdasaryan T. Simultaneous modal phase and group velocity matching in microstructured optical fibers for second harmonic generation with ultrashort pulses. OPTICS EXPRESS 2022; 30:12026-12038. [PMID: 35473132 DOI: 10.1364/oe.453844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Accepted: 03/18/2022] [Indexed: 06/14/2023]
Abstract
Optical fibers provide a favorable medium for nonlinear optical processes owing to the small mode field size and concurrently high optical intensity combined with the extended interaction lengths. Second harmonic generation (SHG) is one of those processes that has been demonstrated in silica glass optical fibers. Since silica is centrosymmetric, generating SHG in an optical fiber requires poling of the glass. In addition and when one wants to use ultrashort pulses for SHG, achieving both phase and group velocity matching is crucial. Although fibers that feature either modal phase velocity or group velocity matching for SHG have been reported, the possibility of simultaneous modal phase and group velocity matching was never reported before. In this paper we address this challenge, and for the first time to our knowledge, we show that it is feasible to do so with silica microstructured optical fibers featuring at least one ring of air holes in the cladding and a heavily Germanium doped core (above 25 mol.%) by exploiting the LP01(ω) and LP02(2ω) modes at 1.06 µm pump and 0.53 µm second harmonic wavelengths. This finding can greatly impact applications requiring waveguide based SHG generation with ultrashort pulses, including microscopy, material characterization and nonlinear imaging.
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Hu C, Field JJ, Kelkar V, Chiang B, Wernsing K, Toussaint KC, Bartels RA, Popescu G. Harmonic optical tomography of nonlinear structures. NATURE PHOTONICS 2020; 14:564-569. [PMID: 34367322 PMCID: PMC8341385 DOI: 10.1038/s41566-020-0638-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Second-harmonic generation microscopy is a valuable label-free modality for imaging non-centrosymmetric structures and has important biomedical applications from live-cell imaging to cancer diagnosis. Conventional second-harmonic generation microscopy measures intensity signals that originate from tightly focused laser beams, preventing researchers from solving the scattering inverse problem for second-order nonlinear materials. Here, we present harmonic optical tomography (HOT) as a novel modality for imaging microscopic, nonlinear and inhomogeneous objects. The HOT principle of operation relies on inter-ferometrically measuring the complex harmonic field and using a scattering inverse model to reconstruct the three-dimensional distribution of harmonophores. HOT enables strong axial sectioning via the momentum conservation of spatially and temporally broadband fields. We illustrate the HOT operation with experiments and reconstructions on a beta-barium borate crystal and various biological specimens. Although our results involve second-order nonlinear materials, we show that this approach applies to any coherent nonlinear process.
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Affiliation(s)
- Chenfei Hu
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- These authors contributed equally: Chenfei Hu, Jeffrey J. Field
| | - Jeffrey J Field
- Microscope Imaging Network Core Facility, Colorado State University, Fort Collins, CO, USA
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, USA
- Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, CO, USA
- These authors contributed equally: Chenfei Hu, Jeffrey J. Field
| | - Varun Kelkar
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Benny Chiang
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Keith Wernsing
- Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, CO, USA
| | | | - Randy A Bartels
- Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, CO, USA
- School of Biomedical Engineering, Colorado State University, Fort Collins, CO, USA
| | - Gabriel Popescu
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
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Lu B, Torchinsky DH. Fourier domain rotational anisotropy-second harmonic generation. OPTICS EXPRESS 2018; 26:33192-33204. [PMID: 30645475 DOI: 10.1364/oe.26.033192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 11/09/2018] [Indexed: 06/09/2023]
Abstract
We describe a novel scheme of detecting rotational anisotropy-second harmonic generation (RA-SHG) signals using a lock-in amplifier referenced to a fast scanning RASHG apparatus. The method directly measures the nth harmonics of the scanning frequency corresponding to SHG signal components of Cn symmetry that appear in a Fourier series expansion of a general RA-SHG signal. GaAs was used as a test sample allowing comparison of point-by-point averaging with the lock-in based method. When divided by the C∞ signal component, the lock-in detected data allowed for both self-referenced determination of ratios of Cn components of up to 1 part in 104 and significantly more sensitive measurement of the relative amount of different Cn components when compared with conventional methods.
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Gao Y, Goodman AJ, Shen PC, Kong J, Tisdale WA. Phase-Modulated Degenerate Parametric Amplification Microscopy. NANO LETTERS 2018; 18:5001-5006. [PMID: 29932677 DOI: 10.1021/acs.nanolett.8b01827] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Second-order nonlinear optical interactions, including second-harmonic generation (SHG) and sum-frequency generation (SFG), can reveal a wealth of information about chemical, electronic, and vibrational dynamics at the nanoscale. Here, we demonstrate a powerful and flexible new approach, called phase-modulated degenerate parametric amplification (DPA). The technique, which allows for facile retrieval of both the amplitude and phase of the second-order nonlinear optical response, has many advantages over conventional or heterodyne-detected SHG, including the flexibility to detect the signal at either the second harmonic or fundamental field wavelength. We demonstrate the capabilities of this approach by imaging multigrain flakes of single-layer MoS2. We identify the absolute crystal orientation of each MoS2 domain and resolve grain boundaries with high signal contrast and sub-diffraction-limited spatial resolution. This robust all-optical method can be used to characterize structure and dynamics in organic and inorganic systems, including biological tissue, soft materials, and metal and semiconductor nanostructures, and is particularly well-suited for imaging in media that are absorptive or highly scattering to visible and ultraviolet light.
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Xiang B, Li Y, Pham CH, Paesani F, Xiong W. Ultrafast direct electron transfer at organic semiconductor and metal interfaces. SCIENCE ADVANCES 2017; 3:e1701508. [PMID: 29159282 PMCID: PMC5694661 DOI: 10.1126/sciadv.1701508] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Accepted: 10/19/2017] [Indexed: 06/01/2023]
Abstract
The ability to control direct electron transfer can facilitate the development of new molecular electronics, light-harvesting materials, and photocatalysis. However, control of direct electron transfer has been rarely reported, and the molecular conformation-electron dynamics relationships remain unclear. We describe direct electron transfer at buried interfaces between an organic polymer semiconductor film and a gold substrate by observing the first dynamical electric field-induced vibrational sum frequency generation (VSFG). In transient electric field-induced VSFG measurements on this system, we observe dynamical responses (<150 fs) that depend on photon energy and polarization, demonstrating that electrons are directly transferred from the Fermi level of gold to the lowest unoccupied molecular orbital of organic semiconductor. Transient spectra further reveal that, although the interfaces are prepared without deliberate alignment control, a subensemble of surface molecules can adopt conformations for direct electron transfer. Density functional theory calculations support the experimental results and ascribe the observed electron transfer to a flat-lying polymer configuration in which electronic orbitals are found to be delocalized across the interface. The present observation of direct electron transfer at complex interfaces and the insights gained into the relationship between molecular conformations and electron dynamics will have implications for implementing novel direct electron transfer in energy materials.
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Affiliation(s)
- Bo Xiang
- Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA 92093–0418, USA
| | - Yingmin Li
- Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA 92093–0418, USA
| | - C. Huy Pham
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093–0358, USA
| | - Francesco Paesani
- Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA 92093–0418, USA
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093–0358, USA
| | - Wei Xiong
- Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA 92093–0418, USA
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093–0358, USA
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Han J, Liu H, Huang N, Wang Z. Stochastic resonance based on modulation instability in spatiotemporal chaos. OPTICS EXPRESS 2017; 25:8306-8314. [PMID: 28380945 DOI: 10.1364/oe.25.008306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A novel dynamic of stochastic resonance in spatiotemporal chaos is presented, which is based on modulation instability of perturbed partially coherent wave. The noise immunity of chaos can be reinforced through this effect and used to restore the coherent signal information buried in chaotic perturbation. A theoretical model with fluctuations term is derived from the complex Ginzburg-Landau equation via Wigner transform. It shows that through weakening the nonlinear threshold and triggering energy redistribution, the coherent component dominates the instability damped by incoherent component. The spatiotemporal output showing the properties of stochastic resonance may provide a potential application of signal encryption and restoration.
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Grechko M, Gonella G, Bonn M. Comment on "Enhancement of Second-Order Nonlinear-Optical Signals by Optical Stimulation". PHYSICAL REVIEW LETTERS 2016; 116:059401. [PMID: 26894740 DOI: 10.1103/physrevlett.116.059401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Indexed: 06/05/2023]
Affiliation(s)
- Maksim Grechko
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Grazia Gonella
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Mischa Bonn
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
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Goodman AJ, Tisdale WA. Goodman and Tisdale Reply. PHYSICAL REVIEW LETTERS 2016; 116:059402. [PMID: 26894741 DOI: 10.1103/physrevlett.116.059402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Indexed: 06/05/2023]
Affiliation(s)
- A J Goodman
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - W A Tisdale
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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