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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

Schematic of a scanning cavity microscope.(a) A cavity built from a laser-machined and mirror-coated optical fibre and a planar mirror serving as a sample holder. Transverse scanning of the sample mirror is used for spatial imaging, axial scanning of the fibre for resonance tuning. (b) Cavity transmission signal when tuning the cavity length. The PSFs of different transverse modes (insets) are measured by scanning the cavity across a single Au nanoparticle and evaluating the resonant transmission for each mode.
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f1: Schematic of a scanning cavity microscope.(a) A cavity built from a laser-machined and mirror-coated optical fibre and a planar mirror serving as a sample holder. Transverse scanning of the sample mirror is used for spatial imaging, axial scanning of the fibre for resonance tuning. (b) Cavity transmission signal when tuning the cavity length. The PSFs of different transverse modes (insets) are measured by scanning the cavity across a single Au nanoparticle and evaluating the resonant transmission for each mode.

Mentions: In this work, we report on a versatile approach that combines cavity enhancement with high-resolution imaging and provides high sensitivity for both sample absorption and dispersion simultaneously. It is based on an open-access optical microcavity1516171819 made of two highly reflective mirrors, which permits imaging a sample by raster-scanning it through a microscopic cavity mode. Fig. 1a shows the basic set-up used in our experiments. Multiple round trips of light between the mirrors accumulate loss and dispersive phase shifts caused by the sample. For a sample localized in the field maximum, the enhancement compared with a single pass amounts to , given by the number of reflections and the increased intensity owing to the standing wave in the cavity. Here is the cavity finesse and R the reflectivity of both mirrors. Notably, the same enhancement is available for absorption, scattering, fluorescence and dispersive signals2021. At the same time, the overall signal scales inversely with the mode cross-section , such that a cavity that maximizes the figure of merit is desired.


A scanning cavity microscope.

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

Schematic of a scanning cavity microscope.(a) A cavity built from a laser-machined and mirror-coated optical fibre and a planar mirror serving as a sample holder. Transverse scanning of the sample mirror is used for spatial imaging, axial scanning of the fibre for resonance tuning. (b) Cavity transmission signal when tuning the cavity length. The PSFs of different transverse modes (insets) are measured by scanning the cavity across a single Au nanoparticle and evaluating the resonant transmission for each mode.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: Schematic of a scanning cavity microscope.(a) A cavity built from a laser-machined and mirror-coated optical fibre and a planar mirror serving as a sample holder. Transverse scanning of the sample mirror is used for spatial imaging, axial scanning of the fibre for resonance tuning. (b) Cavity transmission signal when tuning the cavity length. The PSFs of different transverse modes (insets) are measured by scanning the cavity across a single Au nanoparticle and evaluating the resonant transmission for each mode.
Mentions: In this work, we report on a versatile approach that combines cavity enhancement with high-resolution imaging and provides high sensitivity for both sample absorption and dispersion simultaneously. It is based on an open-access optical microcavity1516171819 made of two highly reflective mirrors, which permits imaging a sample by raster-scanning it through a microscopic cavity mode. Fig. 1a shows the basic set-up used in our experiments. Multiple round trips of light between the mirrors accumulate loss and dispersive phase shifts caused by the sample. For a sample localized in the field maximum, the enhancement compared with a single pass amounts to , given by the number of reflections and the increased intensity owing to the standing wave in the cavity. Here is the cavity finesse and R the reflectivity of both mirrors. Notably, the same enhancement is available for absorption, scattering, fluorescence and dispersive signals2021. At the same time, the overall signal scales inversely with the mode cross-section , such that a cavity that maximizes the figure of merit is desired.

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