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Slow and stopped light by light-matter coherence control
KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics. (Photonics and Microwave Engineering)
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis we study light-matter coherence phenomena related to the interaction of a coherent laser field and the so-called Λ-system, a three-level quantum system (e.g., an atom). We observe electromagnetically induced transparency (EIT), slow and stored light in hot rubidium vapor. For example, a 6 μs Gaussian pulse propagate at a velocity of ~1 km/s (to be compared with the normal velocity of 300 000 km/s). Dynamic changes of the control parameter allows us to slow down a pulse to a complete stop, store it for ~100 μs, and then release it. During the storage time, and also during the release process, some properties of the light pulse can be changed, e.g., frequency chirping of the pulse is obtained by means of Zeeman shifting the energy levels of the Λ-system. If, bichromatic continuous light fields are applied we observe overtone generation in the beating signal, and a narrow `dip' in overtone generation efficiency on two-photon resonance, narrower than the `coherent population trapping' transparency. The observed light-matter coherence phenomena are explained theoretically from first principles, using the Lindblad master equation, in conjunction with the Maxwell's equations. Furthermore, we analyze an optical delay-line based on EIT and show that there is in principle (besides decoherence) no fundamental limitation, but the usefulness today is scant. The combination of EIT and a photonic crystal cavity is inquired into, and we show that the quality value of a small resonator (area of 2.5λ×2.5λ with a missing central rod) can be enhanced by a factor of 500 due to the increased modal density close to two-photon resonance. Open system effects (decoherence effects) are thoroughly investigated using a coherence vector formalism, furthermore, a vector form of the Lindblad equation is derived. Specifically we find an open system channel that lead to slow light and gain.

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , xii, 105 p.
Series
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2009:09
Keyword [en]
slow light, stored light, stopped light, light-matter coherence, electromagnetically induced transparency, rubidium atoms
National Category
Physical Sciences Telecommunications
Identifiers
URN: urn:nbn:se:kth:diva-11212ISBN: 978-91-7415-429-0 (print)OAI: oai:DiVA.org:kth-11212DiVA: diva2:242285
Public defence
2009-10-29, C1, Electrum, Isafjordsgatan 22, Kista, 13:15 (English)
Opponent
Supervisors
Note
QC 20100812Available from: 2009-10-07 Created: 2009-10-06 Last updated: 2012-03-27Bibliographically approved
List of papers
1. Limits on optical pulse compression and delay bandwidth product in electromagnetically induced transparency media
Open this publication in new window or tab >>Limits on optical pulse compression and delay bandwidth product in electromagnetically induced transparency media
2005 (English)In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 23, no 11, 3893-3899 p.Article in journal (Refereed) Published
Abstract [en]

Delay bandwidth products (DBPs) and physical pulselengths obtainable in media exhibiting electromagnetically induced transparency (EIT) are analyzed. The study is performed in stationary media as well as for dynamic storing of light pulses in such media. In the latter case; the dispersion inherent in storage and readout of the pulses is analyzed. It is shown that absorption and the group velocity dispersion (GVD) are limiting factors. Analytical expressions for the minimum compressed 'pulselength and DBP are derived, and these expressions show good agreement with simulations of pulse propagation in EIT media.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-6664 (URN)10.1109/JLT.2005.857733 (DOI)000234116800053 ()
Note
QC 20100903Available from: 2006-12-15 Created: 2006-12-15 Last updated: 2017-12-14Bibliographically approved
2. Delay bandwidth product of electromagnetically induced transparency media
Open this publication in new window or tab >>Delay bandwidth product of electromagnetically induced transparency media
2007 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 75, no 5, 053803- p.Article in journal (Refereed) Published
Abstract [en]

The limitations on the delay-bandwidth product (DBP) in an electromagnetically induced transparency medium are investigated analytically by studying the susceptibility of the system, derived through Lindblad's master equation, including dephasing. The effect of inhomogeneous broadening is treated. It is shown that the DBP for a given material is fundamentally limited by the frequency-dependent absorption, while the residual absorption limits the penetration length of a pulse. Simple expression for the optimal choice of parameters to maximize the DBP are derived. Also, the length of a device is presented as a function of DBP and control-field Rabi frequency. Supporting these results, numerical calculations are carried out through the Maxwell-Bloch equations in the slowly varying envelope approximation. The results are scalable, hence they apply to the case of atoms or molecules in a gas as well as quantum dots and wells.

Keyword
coherent population transfer, slow-light, optical buffers, atomic gas, propagation, ultraslow, dynamics, pulses
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-6665 (URN)10.1103/PhysRevA.75.053803 (DOI)000246890400148 ()2-s2.0-34247875970 (Scopus ID)
Note
QC 20100903Available from: 2006-12-15 Created: 2006-12-15 Last updated: 2017-12-14Bibliographically approved
3. Overtone generation in driven coherent media
Open this publication in new window or tab >>Overtone generation in driven coherent media
2009 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 79, no 6, 063832-1-063832-7 p.Article in journal (Refereed) Published
Abstract [en]

We observe overtone signal generation of a near-resonant bichromatic light field interacting with 85Rb on the Zeeman split F=2F=1,2,3 hyperfine transitions of the D2 line at 780 nm. A nonperturbative theoretical model for electromagnetically induced transparency is developed in order to explain this phenomenon. Assuming a  system, an explicit and convenient expression for the atomic coherence is derived from the Lindblad equation assuming a phase-damping channel. The light field state is parametrically varied through one beat note of the bichromatic field and the spatial properties are studied by numerically solving the coupled-wave equation. The polarization characteristics is analyzed on the Poincaré sphere, which together with field intensity analysis offers a simple explanation of the harmonic beating signal due to Stokes vector rotation around the Poincaré sphere and decoherence effects. The experimental data and theoretical analysis focus on the first and second harmonics, although many higher harmonics are present. A distinct and narrow minimum of the second-harmonic generation is measured on two-photon resonance.

Keyword
light-matter coherence, overtone generation
National Category
Physical Sciences Telecommunications
Identifiers
urn:nbn:se:kth:diva-11223 (URN)10.1103/PhysRevA.79.063832 (DOI)000267700100182 ()2-s2.0-67649382253 (Scopus ID)
Note
QC 20100927Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13Bibliographically approved
4. Open-system effects on slow light and electromagnetically induced transparency
Open this publication in new window or tab >>Open-system effects on slow light and electromagnetically induced transparency
2011 (English)In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 44, no 13, 135501- p.Article in journal (Refereed) Published
Abstract [en]

The coherence properties of a three-level Lambda-system influenced by a Markovian environment are analysed. A coherence vector formalism is used and a vector form of the Lindblad equation is derived. Together with decay channels from the upper state, open-system channels acting on the subspace of the two lower states are investigated, i.e. depolarization, dephasing and amplitude damping channels. We derive an analytic expression for the coherence vector and the concomitant optical susceptibility, and analyse how the different channels influence the optical response. This response depends non-trivially on the type of open-system interaction present, and even gain can be obtained. We also present a geometrical visualization of the coherence vector as an aid to understand the system response.

Keyword
N-LEVEL SYSTEMS, DYNAMICAL SEMIGROUPS, COHERENCE, SPECTROSCOPY, STATES, MEDIA
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-24065 (URN)10.1088/0953-4075/44/13/135501 (DOI)000291870800013 ()2-s2.0-79959799775 (Scopus ID)
Funder
Swedish Research Council
Note
QC 20100812 Updated from submitted to publishedAvailable from: 2010-08-12 Created: 2010-08-12 Last updated: 2017-12-12Bibliographically approved
5. Photonic crystal cavity embedded in electromagnetically induced transparency media
Open this publication in new window or tab >>Photonic crystal cavity embedded in electromagnetically induced transparency media
2010 (English)In: Journal of Optics, ISSN 2040-8978, E-ISSN 2040-8986, Vol. 12, no 3, 035105- p.Article in journal (Refereed) Published
Abstract [en]

Photonic crystal cavities are known for their high quality factor and small modal volume. Electromagnetically induced transparency (EIT) is known for its dramatic dispersion. We study the fundamental cavity mode of a two-dimensional photonic crystal embedded in an EIT medium. Comparison of finite-difference time-domain simulations with an analytical intracavity-EIT model yields similar results: the modal density of the photonic crystal cavity increases and the cavity resonance is pulled from the empty cavity resonance to the two-photon resonance of the EIT medium. As a consequence, the quality factor may be enhanced by more than two orders of magnitude. For a miniature sized 2.5 lambda x 2.5 lambda photonic crystal cavity based on a 5 x 5 high index rod structure with a missing centre rod, the quality factor can be increased from 200 to 40 000.

Keyword
photonic crystal cavity, electromagnetically induced transparency, quality factor, mode pulling
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-29490 (URN)10.1088/2040-8978/12/3/035105 (DOI)000279943100011 ()2-s2.0-77951831328 (Scopus ID)
Funder
Swedish Research Council
Note
QC 20110203. Previous title " Photonic crystal microcavity made of electromagnetically induced transparency  material ".Available from: 2011-02-03 Created: 2011-02-02 Last updated: 2017-12-11Bibliographically approved
6. Manipulating light pulses during storage and readout
Open this publication in new window or tab >>Manipulating light pulses during storage and readout
(English)Manuscript (preprint) (Other academic)
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-24066 (URN)
Note
QC 20100812Available from: 2010-08-12 Created: 2010-08-12 Last updated: 2010-08-12Bibliographically approved

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