R. Lettow

ETH Zurich, Zürich, ZH, Switzerland

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Publications (12)89.56 Total impact

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    ABSTRACT: Efficient interaction of light and matter at the ultimate limit of single photons and single emitters is of great interest from a fundamental point of view and for emerging applications in quantum engineering. However, the difficulty of generating single-photon streams with specific wavelengths, bandwidths, and power as well as the weak interaction probability of a single photon with an optical emitter pose a formidable challenge toward this goal. Here, we demonstrate a general approach based on the creation of single photons from a single emitter and their use for performing spectroscopy on a second emitter situated at a distance. While this first proof of principle realization uses organic molecules as emitters, the scheme is readily extendable to quantum dots and color centers. Our work ushers in a new line of experiments that provide access to the coherent and nonlinear couplings of few emitters and few propagating photons.
    Physical Review Letters 03/2012; 108(9):093601. · 7.73 Impact Factor
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    ABSTRACT: Single emitters have been considered as sources of single photons in various contexts such as cryptography, quantum computation, spectroscopy, and metrology. The success of these applications will crucially rely on the efficient directional emission of photons into well-defined modes. To accomplish a high efficiency, researchers have investigated microcavities at cryogenic temperatures, photonic nanowires, and near-field coupling to metallic nano-antennas. However, despite an impressive progress, the existing realizations substantially fall short of unity collection efficiency. Here we report on a theoretical and experimental study of a dielectric planar antenna, which uses a layered structure for tailoring the angular emission of a single oriented molecule. We demonstrate a collection efficiency of 96% using a microscope objective at room temperature and obtain record detection rates of about 50 MHz. Our scheme is wavelength-insensitive and can be readily extended to other solid-state emitters such as color centers and semiconductor quantum dots.
    Nature Photonics 09/2010; · 27.25 Impact Factor
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    ABSTRACT: Single emitters have been considered as sources of single photons in various contexts such as cryptography, quantum computation, spectroscopy, and metrology. The success of these applications will crucially rely on the efficient directional emission of photons into well-defined modes. To accomplish a high efficiency, researchers have investigated microcavities at cryogenic temperatures, photonic nanowires, and near-field coupling to metallic nano-antennas. However, despite an impressive progress, the existing realizations substantially fall short of unity collection efficiency. Here we report on a theoretical and experimental study of a dielectric planar antenna, which uses a layered structure for tailoring the angular emission of a single oriented molecule. We demonstrate a collection efficiency of 96% using a microscope objective at room temperature and obtain record detection rates of about 50 MHz. Our scheme is wavelength-insensitive and can be readily extended to other solid-state emitters such as color centers and semiconductor quantum dots.
    Nature Photonics 09/2010; · 27.25 Impact Factor
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    ABSTRACT: We demonstrate strong coupling of single photons emitted by individual molecules at cryogenic and ambient conditions to individual nanoparticles. We provide images obtained both in transmission and reflection, where an efficiency greater than 55% was achieved in converting incident narrow-band photons to plasmon-polaritons (plasmons) of a silver nanoparticle. Our work paves the way to spectroscopy and microscopy of nano-objects with sub-shot noise beams of light and to triggered generation of single plasmons and electrons in a well-controlled manner.
    Optics Express 06/2010; 18(13):13829-35. · 3.55 Impact Factor
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    ABSTRACT: We demonstrate two-photon interference using two remote single molecules as bright solid-state sources of indistinguishable photons. By varying the transition frequency and spectral width of one molecule, we tune and explore the effect of photon distinguishability. We discuss future improvements on the brightness of single-photon beams, their integration by large numbers on chips, and the extension of our experimental scheme to coupling and entanglement of distant molecules.
    Physical Review Letters 03/2010; 104(12):123605. · 7.73 Impact Factor
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    ABSTRACT: We demonstrate strong coupling of single photons emitted by individual molecules at cryogenic and ambient conditions to individual nanoparticles. We provide images obtained both in transmission and reflection, where an efficiency greater than 55% was achieved in converting incident narrow-band photons to plasmon-polaritons (plasmons) of a silver nanoparticle. Our work paves the way to spectroscopy and microscopy of nano-objects with sub-shot noise beams of light and to triggered generation of single plasmons and electrons in a well-controlled manner.
    11/2009;
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    ABSTRACT: The transistor is one of the most influential inventions of modern times and is ubiquitous in present-day technologies. In the continuing development of increasingly powerful computers as well as alternative technologies based on the prospects of quantum information processing, switching and amplification functionalities are being sought in ultrasmall objects, such as nanotubes, molecules or atoms. Among the possible choices of signal carriers, photons are particularly attractive because of their robustness against decoherence, but their control at the nanometre scale poses a significant challenge as conventional nonlinear materials become ineffective. To remedy this shortcoming, resonances in optical emitters can be exploited, and atomic ensembles have been successfully used to mediate weak light beams. However, single-emitter manipulation of photonic signals has remained elusive and has only been studied in high-finesse microcavities or waveguides. Here we demonstrate that a single dye molecule can operate as an optical transistor and coherently attenuate or amplify a tightly focused laser beam, depending on the power of a second 'gating' beam that controls the degree of population inversion. Such a quantum optical transistor has also the potential for manipulating non-classical light fields down to the single-photon level. We discuss some of the hurdles along the road towards practical implementations, and their possible solutions.
    Nature 08/2009; 460(7251):76-80. · 38.60 Impact Factor
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    ABSTRACT: We report on interferometric imaging of single gold nanoparticles using narrow-band single photons resonant with the particle plasmon resonance.
    05/2009;
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    ABSTRACT: The amplification of light by a single excited molecule in free space is demonstrated in this paper. The extinction effect is the result of a destructive interference between the incident laser beam and the coherently scattered light from the molecule in the ground state. Thus, inversion of the population should lead to a phase shift of the scattered light and amplification of the laser light.
    Lasers and Electro-Optics, 2009 and 2009 Conference on Quantum electronics and Laser Science Conference. CLEO/QELS 2009. Conference on; 01/2009
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    ABSTRACT: We report on the triggered generation of indistinguishable photons by solid-state single-photon sources in two separate cryogenic laser scanning microscopes. Organic fluorescent molecules were used as emitters and investigated by means of high resolution laser spectroscopy. Continuous-wave photon correlation measurements on individual molecules proved the isolation of single quantum systems. By using frequency selective pulsed excitation of the molecule and efficient spectral filtering of its emission, we produced triggered Fourier-limited single photons. In a further step, local electric fields were applied to match the emission wavelengths of two different molecules via Stark effect. Identical single photons are indispensible for the realization of various quantum information processing schemes proposed. The solid-state approach presented here prepares the way towards the integration of multiple bright sources of single photons on a single chip. Comment: Accepted for publication in J. Mod. Opt. This is the original submitted version
    Journal of Modern Optics 10/2008; · 1.16 Impact Factor
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    ABSTRACT: We combined high resolution laser spectroscopy and microscopy to identify individual molecules in two independent microscopes. Then the Stark effect was exploited to tune the transition frequencies of the molecules and thus obtain indistinguishable single photons.
    Lasers and Electro-Optics, 2008 and 2008 Conference on Quantum Electronics and Laser Science. CLEO/QELS 2008. Conference on; 06/2008
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    ABSTRACT: We demonstrate two solid-state sources of indistinguishable single photons. High resolution laser spectroscopy and optical microscopy were combined at T = 1.4 K to identify individual molecules in two independent microscopes. The Stark effect was exploited to shift the transition frequency of a given molecule and thus obtain single photon sources with perfect spectral overlap. Our experimental arrangement sets the ground for the realization of various quantum interference and information processing experiments.
    Optics Express 12/2007; 15(24):15842-7. · 3.55 Impact Factor
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    ABSTRACT: We report on the triggered generation of indistingu ishable photons by solid-state single-photon source s in two separate cryogenic laser scanning microscopes. Orga nic fluorescent molecules were used as emitters and investigated by means of high resolution laser spec troscopy. Continuous-wave photon correlation measurements on individual molecules proved the isolation of single quantum systems. By using frequenc y selective pulsed excitation of the molecule and eff icient spectral filtering of its emission, we produ ced triggered Fourier-limited single photons. In a furt her step, local electric fields were applied to mat ch the emission wavelengths of two different molecules via Stark effect. Identical single photons are indispe nsible for the realization of various quantum information processing schemes proposed. The solid-state approa ch presented here prepares the way towards the integra tion of multiple bright sources of single photons o n a single chip.