arXiv subjects

Stefan Kroll

Publications and source records attributed to Stefan Kroll.

5 recordsLinked to original sources

arXiv2013

Spectral Engineering of Slow Light, Cavity Line Narrowing, and Pulse Compression

More than 4 orders of magnitude of cavity-linewidth narrowing in a rare-earth-ion-doped crystal cavity, emanating from strong intracavity dispersion caused by off-resonant interaction with dopant ions, is demonstrated. The dispersion profiles are engineered using optical pumping techniques creating significant semipermanent but reprogrammable changes of the rare-earth absorption profiles. Several cavity modes are shown within the spectral transmission window. Several possible applications of this phenomenon are discussed.

quant-ph↗

arXiv2008

Backward retrieval in optical quantum memory controlled by an external field

A scheme for backward retrieval in optical quantum memories in which information is stored in collective states of an extended resonant atomic ensemble is developed such that phase conjugation can be implemented by application of an external nonuniform electric (magnetic) field without use of coherent exciting pulses. The possibilities of realizing such a scheme using resonant solid-state materials are discussed.

quant-ph↗

arXiv2006

Coherent control of collective spontaneous emission in an extended atomic ensemble and quantum storage

Coherent control of collective spontaneous emission in an extended atomic ensemble resonantly interacting with single-photon wave packets is analyzed. A scheme for coherent manipulation of collective atomic states is developed such that superradiant states of the atomic system can be converted into subradiant ones and vice versa. Possible applications of such a scheme for optical quantum state storage and single-photon wave packet shaping are discussed. It is shown that also in the absence of inhomogeneous broadening of the resonant line, single-photon wave packets with arbitrary pulse shape may be recorded as a subradiant state and reconstructed even although the duration of the wave packets is larger than the superradiant life-time. Specifically the applicability for storing time-bin qubits, which are used in quantum cryptography is analyzed.

quant-ph↗

arXiv2004

Advanced holeburning techniques for determination of hyperfine transition properties in inhomogeneously broadened solids applied to Pr3+:Y2SiO5

A sequence of optical holeburning pulses is used to isolate transitions between hyperfine levels, which are initially buried within an inhomogeneously broadened absorption line. Using this technique selected transitions can be studied with no background absorption on other transitions. This makes it possible to directly study properties of the hyperfine transitions, e.g. transition strengths, and gives access to information that is difficult to obtain in standard holeburning spectroscopy, such as the ordering of hyperfine levels. The techniques introduced are applicable to absorbers in a solid with long-lived sublevels in the ground state and where the homogeneous linewidth and sublevel separations are smaller than the inhomogeneous broadening of the optical transition. In particular, this includes rare-earth ions doped into inorganic crystals and in the present work the techniques are used for spectroscopy of Pr3+ in Y2SiO5. New information on the hyperfine structure and relative transition strengths of the 3H4 - 1D2 hyperfine transitions in Pr3+:Y2SiO5 has been obtained from frequency resolved absorption measurements, in combination with coherent and incoherent driving of the transitions.

cond-mat.other↗

arXiv2003

Experimental investigation of delayed self-interference for single photons

A photon echo experiment has been performed using accumulated highly attenuated laser pulses. We show experimentally that the photon echo process can be performed with, on the average, less than one photon in each pair of excitation pulses. The results support an interpretation where this non-linear process can be performed with, on the average, less than one photon shared between two of the optical fields involved in the degenerate four-wave mixing process. Further, we argue that the experiment can be interpreted as a form of delayed self-interference for photon wave packets that do not overlap in both space and time.

quant-ph↗