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A scanning cavity microscope.

Mader M, Reichel J, Hänsch TW, Hunger D - Nat Commun (2015)

Bottom Line: Imaging the optical properties of individual nanosystems beyond fluorescence can provide a wealth of information.However, the minute signals for absorption and dispersion are challenging to observe, and only specialized techniques requiring sophisticated noise rejection are available.We demonstrate quantitative imaging of the extinction cross-section of gold nanoparticles with a sensitivity less than 1 nm(2); we show a method to improve the spatial resolution potentially below the diffraction limit by using higher order cavity modes, and we present measurements of the birefringence and extinction contrast of gold nanorods.

View Article: PubMed Central - PubMed

Affiliation: 1] Ludwig-Maximilians-Universität München, Fakultät für Physik, Schellingstraße 4, 80799 München, Germany [2] Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching, Germany.

ABSTRACT
Imaging the optical properties of individual nanosystems beyond fluorescence can provide a wealth of information. However, the minute signals for absorption and dispersion are challenging to observe, and only specialized techniques requiring sophisticated noise rejection are available. Here we use signal enhancement in a high-finesse scanning optical microcavity to demonstrate ultra-sensitive imaging. Harnessing multiple interactions of probe light with a sample within an optical resonator, we achieve a 1,700-fold signal enhancement compared with diffraction-limited microscopy. We demonstrate quantitative imaging of the extinction cross-section of gold nanoparticles with a sensitivity less than 1 nm(2); we show a method to improve the spatial resolution potentially below the diffraction limit by using higher order cavity modes, and we present measurements of the birefringence and extinction contrast of gold nanorods. The demonstrated simultaneous enhancement of absorptive and dispersive signals promises intriguing potential for optical studies of nanomaterials, molecules and biological nanosystems.

No MeSH data available.


Related in: MedlinePlus

Extinction contrast and birefringence imaging.Extinction map of Au-nanorods for H—polarized (a) and V—polarized (b) light. (c) Extinction contrast . (d) Absolute splitting of the two orthogonally polarized fundamental cavity modes. Scale bars, 10 μm. (e,f) Transmission signal of the cavity while scanning over the nanorods denoted in b. (g) Correlation between relative line splitting and extinction contrast. Measured values (green dots), calculated correlation assuming a fixed (red solid line) and variable (blue solid line) cavity mode orientation are shown. (h) Relative line splitting and extinction contrast in dependence of the orientation of the nanorod.
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f4: Extinction contrast and birefringence imaging.Extinction map of Au-nanorods for H—polarized (a) and V—polarized (b) light. (c) Extinction contrast . (d) Absolute splitting of the two orthogonally polarized fundamental cavity modes. Scale bars, 10 μm. (e,f) Transmission signal of the cavity while scanning over the nanorods denoted in b. (g) Correlation between relative line splitting and extinction contrast. Measured values (green dots), calculated correlation assuming a fixed (red solid line) and variable (blue solid line) cavity mode orientation are shown. (h) Relative line splitting and extinction contrast in dependence of the orientation of the nanorod.

Mentions: In our experiment, we have to take into account the intrinsic mode splitting present in our cavity. Owing to ellipticity of the laser-machined mirror surface profiles, the modes of the cavity are split into a linear polarization doublet (denoted by H→fast, V→slow), whose axis and splitting is determined by the mirror shape33. By setting the input polarization, we can excite both modes as shown in Fig. 4e,f, and evaluate their response to study polarization effects.


A scanning cavity microscope.

Mader M, Reichel J, Hänsch TW, Hunger D - Nat Commun (2015)

Extinction contrast and birefringence imaging.Extinction map of Au-nanorods for H—polarized (a) and V—polarized (b) light. (c) Extinction contrast . (d) Absolute splitting of the two orthogonally polarized fundamental cavity modes. Scale bars, 10 μm. (e,f) Transmission signal of the cavity while scanning over the nanorods denoted in b. (g) Correlation between relative line splitting and extinction contrast. Measured values (green dots), calculated correlation assuming a fixed (red solid line) and variable (blue solid line) cavity mode orientation are shown. (h) Relative line splitting and extinction contrast in dependence of the orientation of the nanorod.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4491170&req=5

f4: Extinction contrast and birefringence imaging.Extinction map of Au-nanorods for H—polarized (a) and V—polarized (b) light. (c) Extinction contrast . (d) Absolute splitting of the two orthogonally polarized fundamental cavity modes. Scale bars, 10 μm. (e,f) Transmission signal of the cavity while scanning over the nanorods denoted in b. (g) Correlation between relative line splitting and extinction contrast. Measured values (green dots), calculated correlation assuming a fixed (red solid line) and variable (blue solid line) cavity mode orientation are shown. (h) Relative line splitting and extinction contrast in dependence of the orientation of the nanorod.
Mentions: In our experiment, we have to take into account the intrinsic mode splitting present in our cavity. Owing to ellipticity of the laser-machined mirror surface profiles, the modes of the cavity are split into a linear polarization doublet (denoted by H→fast, V→slow), whose axis and splitting is determined by the mirror shape33. By setting the input polarization, we can excite both modes as shown in Fig. 4e,f, and evaluate their response to study polarization effects.

Bottom Line: Imaging the optical properties of individual nanosystems beyond fluorescence can provide a wealth of information.However, the minute signals for absorption and dispersion are challenging to observe, and only specialized techniques requiring sophisticated noise rejection are available.We demonstrate quantitative imaging of the extinction cross-section of gold nanoparticles with a sensitivity less than 1 nm(2); we show a method to improve the spatial resolution potentially below the diffraction limit by using higher order cavity modes, and we present measurements of the birefringence and extinction contrast of gold nanorods.

View Article: PubMed Central - PubMed

Affiliation: 1] Ludwig-Maximilians-Universität München, Fakultät für Physik, Schellingstraße 4, 80799 München, Germany [2] Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching, Germany.

ABSTRACT
Imaging the optical properties of individual nanosystems beyond fluorescence can provide a wealth of information. However, the minute signals for absorption and dispersion are challenging to observe, and only specialized techniques requiring sophisticated noise rejection are available. Here we use signal enhancement in a high-finesse scanning optical microcavity to demonstrate ultra-sensitive imaging. Harnessing multiple interactions of probe light with a sample within an optical resonator, we achieve a 1,700-fold signal enhancement compared with diffraction-limited microscopy. We demonstrate quantitative imaging of the extinction cross-section of gold nanoparticles with a sensitivity less than 1 nm(2); we show a method to improve the spatial resolution potentially below the diffraction limit by using higher order cavity modes, and we present measurements of the birefringence and extinction contrast of gold nanorods. The demonstrated simultaneous enhancement of absorptive and dispersive signals promises intriguing potential for optical studies of nanomaterials, molecules and biological nanosystems.

No MeSH data available.


Related in: MedlinePlus