Multimodal nonlinear spectral microscopy based on a femtosecond Cr:forsterite laser

Chu, Shi‐Wei; Chen, I-Hsiu; Liu, Tzu-Ming; Chen, Ping Chin; Sun, Chi‐Kuang; Lin, Bai-Ling

doi:10.1364/ol.26.001909

Cited by 145 publications

(121 citation statements)

References 12 publications

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“…Second harmonic generation (SHG) microscopy has been developed as a powerful nonlinear optical imaging tool for examining endogenous structures in biological samples [1][2][3][4][5][6][7]. SHG only takes place in a non-centrosymmetric environment, and provides the imaging contrast of specific endogenous biological structures, such as collagen, muscle, and microtubules in a mostly isotropic environment.…”

Section: Introductionmentioning

confidence: 99%

Second harmonic generation from nanocrystals under linearly and circularly polarized excitations

Hsieh¹,

Pu²,

Grange³

et al. 2010

Opt. Express

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Abstract:We study second harmonic generation (SHG) from noncentrosymmetric nanocrystals under linearly polarized (LP) and circularly polarized (CP) excitations. Theoretical models are developed for SHG from nanocrystals under both plane-wave and focused excitations. We find that the focused excitation reduces the polarization dependency of the SHG signal. We show that the SHG response under CP excitation is generally inferior to the average of LP excitations over all orientations. We verify the theory by measuring the SHG polar responses from BaTiO 3 nanocrystals with a scanning confocal microscope. The experimental data agrees well with the theory. ©2010 Optical Society of America References and links1. I. Freund, M. Deutsch, and A. Sprecher, "Connective tissue polarity. Optical second-harmonic microscopy, crossed-beam summation, and small-angle scattering in rat-tail tendon," Biophys. J. 50(4), 693-712 (1986). 2. S. W. Chu, I. H. Chen, T. M. Liu, P. C. Chen, C. K. Sun, and B. L. Lin, "Multimodal nonlinear spectral microscopy based on a femtosecond Cr:forsterite laser," Opt. Lett. 26(23), 1909-1911 (2001). in polarization second-harmonic generation microscopy without specimen rotation," J.

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Section: Introductionmentioning

confidence: 99%

Second harmonic generation from nanocrystals under linearly and circularly polarized excitations

Hsieh¹,

Pu²,

Grange³

et al. 2010

Opt. Express

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“…1 MPM typically uses near-infrared ͑NIR͒ excitation at 700 to 1000 nm to generate fluorescence in the visible wavelengths. 2 Although the excitation wavelength of MPM has been extended [3][4][5][6][7][8] beyond 1000 nm, to our knowledge no imaging has been performed with NIR-emitting contrast agents. Conventional ͑linear͒ fluorescence imaging has shown that molecular imaging with NIR ͑ Ͼ 700 nm͒ agents minimizes the contribution from endogenous fluorescence and increases penetration depth.…”

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confidence: 99%

Multiphoton microscopy with near infrared contrast agents

et al. 2010

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Abstract. While multiphoton microscopy ͑MPM͒ has been performed with a wide range of excitation wavelengths, fluorescence emission has been limited to the visible spectrum. We introduce a paradigm for MPM of near-infrared ͑NIR͒ fluorescent molecular probes via nonlinear excitation at 1550 nm. This all-NIR system expands the range of available MPM fluorophores, virtually eliminates background autofluorescence, and allows for use of fiber-based, turnkey ultrafast lasers developed for telecommunications. Multiphoton microscopy ͑MPM͒ has become an indispensable optical imaging modality due to its intrinsic threedimensional localization, low photobleaching and photodamage outside the focal volume, and improved imaging depth. 1MPM typically uses near-infrared ͑NIR͒ excitation at 700 to 1000 nm to generate fluorescence in the visible wavelengths.2 Although the excitation wavelength of MPM has been extended 3-8 beyond 1000 nm, to our knowledge no imaging has been performed with NIR-emitting contrast agents. Conventional ͑linear͒ fluorescence imaging has shown that molecular imaging with NIR ͑ Ͼ 700 nm͒ agents minimizes the contribution from endogenous fluorescence and increases penetration depth.9 Since conventional MPM efficiently images endogenous molecules such as collagen, elastin, and reduced nicotinamide adenine dinucleotide ͑NADH͒, 10 the signal from these and other endogenous fluorophores restricts molecular imaging with exogenous contrast agents. This is particularly problematic when target concentrations are low, and strategies to reduce autofluorescence become critical to image contrast. Here, we measure twophoton-induced fluorescence of NIR dyes and demonstrate their use for autofluorescence-free biological imaging.Heptamethine cyanine dyes were selected as NIR contrast agents because of their biocompatibility and the availability of diverse structures with single photon ͑1P͒ absorption and emission between 700 and 850 nm. Cypate, a derivative of indocyanine green, was prepared as previously reported, 11 and 3,3Ј-diethylthiatricarbocyanine iodide ͑DTTCI͒ were purchased from a commercial source ͑Sigma-Aldrich, Saint Louis, Missouri͒. These dyes exhibit an absorption/emission peak of 799/ 817 nm and 771/ 800 nm, respectively. Fortuitously, these absorption maxima of NIR dyes correspond to roughly half the telecommunications spectral window at 1550 nm. As this overlaps with the gain spectrum of erbium, we perform all-NIR MPM using a simple, turnkey erbiumdoped fiber laser. A mode-locked femtosecond fiber laser ͑Mercury 1000, PolarOnyx, Sunnyvale, California͒ provided 100 mW of excitation light at ϳ1550 nm through a ϳ1-m optical fiber ͑Fig. 1͒. At the output of the fiber, the pulse duration was nominally 100 fs with a repetition rate of 50 MHz, although positive material dispersion of the optical components in the system leads to pulse broadening and reduces excitation efficiency at the sample. These losses can be recovered if the pulses arriving at the sample are transformlimited by precompensating for material...

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“…The same idea has been recently applied to two-photon fluorescence microscopy, where several groups have attained much deeper imaging capabilities when longer excitation wavelength was employed. [17][18][19] For example, by utilizing the fundamental wavelength of a Cr:forsterite laser (around 1250 nm), a substantial improvement has been achieved in terms of the imaging depth for the two-photon excitation.…”

Section: Introductionmentioning

confidence: 99%

Hyperspectral coherent anti-Stokes Raman scattering microscopy imaging through turbid medium

2011

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Abstract. Coherent Raman microspectroscopy imaging is an emerging technique for noninvasive, chemically specific optical imaging, which can be potentially used to analyze the chemical composition and its distribution in biological tissues. In this report, a hierarchical cluster analysis was applied to hyperspectral coherent anti-Stokes Raman imaging of different chemical species through a turbid medium. It was demonstrated that by using readily available commercial software (Cytospec, Inc.) and cluster analysis, distinct chemical species can be imaged and identified through a rather thick layer of scattering medium. Once the clusters of different chemical composition were distinguished, a phase retrieval algorithm was used to convert coherent anti-Stokes Raman spectra to Raman spectra, which were used for chemical identification of hidden microscopic objects. In particular, applications to remote optical sensing of potential biological threats and to imaging through a layer of skin tissue were successfully demonstrated. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

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Multimodal nonlinear spectral microscopy based on a femtosecond Cr:forsterite laser

Cited by 145 publications

References 12 publications

Second harmonic generation from nanocrystals under linearly and circularly polarized excitations

Second harmonic generation from nanocrystals under linearly and circularly polarized excitations

Multiphoton microscopy with near infrared contrast agents

Hyperspectral coherent anti-Stokes Raman scattering microscopy imaging through turbid medium

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