Limits...
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 cross-section of gold nanoparticles.(a) Spatially resolved map of the extinction cross-section for a mirror carrying 40 nm gold nanospheres. Scale bar, 10 μm. (b)Transmission signal of the fundamental cavity mode with sidebands when centered on an individual nanosphere (blue) and on a clean mirror spot (red). (c) Histogram of the measured particle extinction cross-section (blue) and calculated distribution (red solid line). (d) Extinction measurement of a nanoparticle by transmission (left half) and linewidth (right half). Scale bar, 1 μm. (e) Pixel-by-pixel comparison between the extinction cross-section as measured by cavity transmission and linewidth.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4491170&req=5

f2: Extinction cross-section of gold nanoparticles.(a) Spatially resolved map of the extinction cross-section for a mirror carrying 40 nm gold nanospheres. Scale bar, 10 μm. (b)Transmission signal of the fundamental cavity mode with sidebands when centered on an individual nanosphere (blue) and on a clean mirror spot (red). (c) Histogram of the measured particle extinction cross-section (blue) and calculated distribution (red solid line). (d) Extinction measurement of a nanoparticle by transmission (left half) and linewidth (right half). Scale bar, 1 μm. (e) Pixel-by-pixel comparison between the extinction cross-section as measured by cavity transmission and linewidth.

Mentions: Figure 2a shows an example for a measurement where we evaluate the resonant cavity transmission of the fundamental mode. On resonance, the cavity transmission is given by . Here Ti, Li, i={1, 2} is the respective mirror transmission and loss, which can be inferred from measurements on a clean mirror with high precision (∼5% uncertainty), and B is the additional loss introduced by the sample. The mode matching between the fibre mode and the respective cavity mode with mode index (m,n) can be tuned by angular alignment of the fibre with respect to the plane mirror to achieve controlled coupling to modes up to order m+n∼8. From the additional loss, we can quantitatively extract the extinction cross-section of the sample, . The mode waist of the cavity can be obtained from the point spread function (PSF) observed for a point-like particle, see Fig. 2d.


A scanning cavity microscope.

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

Extinction cross-section of gold nanoparticles.(a) Spatially resolved map of the extinction cross-section for a mirror carrying 40 nm gold nanospheres. Scale bar, 10 μm. (b)Transmission signal of the fundamental cavity mode with sidebands when centered on an individual nanosphere (blue) and on a clean mirror spot (red). (c) Histogram of the measured particle extinction cross-section (blue) and calculated distribution (red solid line). (d) Extinction measurement of a nanoparticle by transmission (left half) and linewidth (right half). Scale bar, 1 μm. (e) Pixel-by-pixel comparison between the extinction cross-section as measured by cavity transmission and linewidth.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: Extinction cross-section of gold nanoparticles.(a) Spatially resolved map of the extinction cross-section for a mirror carrying 40 nm gold nanospheres. Scale bar, 10 μm. (b)Transmission signal of the fundamental cavity mode with sidebands when centered on an individual nanosphere (blue) and on a clean mirror spot (red). (c) Histogram of the measured particle extinction cross-section (blue) and calculated distribution (red solid line). (d) Extinction measurement of a nanoparticle by transmission (left half) and linewidth (right half). Scale bar, 1 μm. (e) Pixel-by-pixel comparison between the extinction cross-section as measured by cavity transmission and linewidth.
Mentions: Figure 2a shows an example for a measurement where we evaluate the resonant cavity transmission of the fundamental mode. On resonance, the cavity transmission is given by . Here Ti, Li, i={1, 2} is the respective mirror transmission and loss, which can be inferred from measurements on a clean mirror with high precision (∼5% uncertainty), and B is the additional loss introduced by the sample. The mode matching between the fibre mode and the respective cavity mode with mode index (m,n) can be tuned by angular alignment of the fibre with respect to the plane mirror to achieve controlled coupling to modes up to order m+n∼8. From the additional loss, we can quantitatively extract the extinction cross-section of the sample, . The mode waist of the cavity can be obtained from the point spread function (PSF) observed for a point-like particle, see Fig. 2d.

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