Na­no Op­tics

Group Mem­bers

Group LeaderMohamed Benyoucef
PhD StudentsÖzlem Urcan, Mohanad Alkaales, Miriam Gerstel, Muhammad Shaharukh, Ranbir Kaur, Andrei Kors, Patrick Krawiec, Matusala Yacob, Muhammad Usman
Master- & BachelorstudentsBirk Fritsch, Lucas Rickert, Adnan Sayyed, Andreas Körner

Ob­jec­tives

The research group focuses on the development of novel and advanced quantum architectures fabricated on Si, GaAs, (flat and pre-patterned) and InP substrates using molecular beam epitaxy and investigated their specific aspects of quantum optics. The first is considered to be as one of the key technologies combining the best of both materials leading to a highly versatile hybrid photonics platform which opens the way to large scale photonic integration; this could allow a direct combination of photonics and electronics on the same chip. The later could allow the implementation of efficient single-photon sources for long-distance quantum information.

The emphasis is on the fabrication (growth and processing) and studies the fundamental structural and quantum optical properties of the single quantum nano-architectures. Integration of III-V semiconductor light sources with silicon, fabrication and characterization of microcavities (e.g., photonic crystal) in combination with integrated quantum dots and processing of nanostructured surfaces for optical devices.

A new research filed in the group is recently started to work on molecular quantum systems for quantum computer applications. This research work will be developed in the framework of newly funded collaborative priority project in the frame of the state initiative for the development of scientific and economic excellence (LOEWE) entitled "Scalable Molecular Quantum Bits (SMolBits)" by the State of Hesse. This is an interdisciplinary work and will be carried out in collaboration with groups from the Center of Interdisciplinary Nanostructure Science and Technology (CINSaT) (Electrical Engineering, Chemistry and Physics). In this focus, molecular quantum systems will be investigated using for example lanthanoid complexes. We are leading two central sub-areas of the focus (B3-Spectroscopy of immobilized molecules and C-Integration in Photonic Chip).

Pro­jects

 

Open Positions

We are always interested in motivated and ambitious studentswho are eager to embark on a challenging project with us (for Bachelor, Master and PhD level). Do not hesitate to contact me (m.benyoucef@physik.uni-kassel.de). You are also very welcome to bring your own ideas and I will be happy to discuss it with you.

PostDoc and PhD

A funded post-doctoral position is immediately available in the Nano Optics group in the field of spectroscopy and quantum optics of single quantum emitters. Experience with optical characterization of nanostructures or quantum optics is desirable. Also, relevant experience in the field of quantum systems, correlation measurements, nanofabrication is of advantage.

A new open PhD position is available in my group. This position will be offered to a highly motivated student who intends to enhance her/his scientist career in the field of semiconductor quantum optics. She/he should have a high interest in basic experimental research and like working in an interdisciplinary environment.

Tasks:

a)  Growth of high-quality InP-based quantum dots (QDs) and quantum dots molecules (QDM) for quantum communication application. b)  Integration of QDs and QDM in photonic structures. c)  Optical characterizations of the photonic structures.

This work will be performed in cooperation with many other groups in Germany.

Interested candidates should send a CV and short motivation letter directly to m.benyoucef[at]physik.uni-kassel[dot]de.

 

Re­se­arch Ac­tivi­ties

  • Epitaxy growth of semiconductor nanostructures on different substrates using MBE-system
  • Development of single-photon sources at telecom wavelengths for long-distance quantum communication
  • Development of telecom quantum dot emission for spin storage
  • Integration of single InA/GaAs core-shell quantum dots in silicon
  • Processing of nanostructured surfaces for the realization of deterministic optical devices
  • Fabrication and investigation of microcavity structures (e.g., pillar cavities, photonic crystals)
  • Studies the structural properties of self-assembled quantum dots
  • Studies light-matter interaction at the nanoscale of solid-state quantum systems

InP-ba­sed quan­tum dots:

(a) µ-PL spectrum from single InP-based quantum dot (QD). The inset shows the 2x2 µm2 2D AFM image of low density QDs. (b) Single-photon emission at telecom wavelengths from single InP-based QDs (in cooperation with Uni. Stuttgart). (c) Coherent properties of single InP-based QDs (in cooperation with Uni. Paderborn).  (d) The measured electron (full squares) and hole (open circles) g-factors for QDs emitting at telecom wavelengths (in cooperation with TU Dortmund).
(a) µ-PL spectrum from single InP-based quantum dot (QD). The inset shows the 2x2 µm2 2D AFM image of low density QDs. (b) Single-photon emission at telecom wavelengths from single InP-based QDs (in cooperation with Uni. Stuttgart). (c) Coherent properties of single InP-based QDs (in cooperation with Uni. Paderborn). (d) The measured electron (full squares) and hole (open circles) g-factors for QDs emitting at telecom wavelengths (in cooperation with TU Dortmund).

Li­te­ra­tu­re

InP-ba­sed pho­to­nic crys­tal mi­cro­ca­vi­ties:

(a) μ-PL spectra of L3 PhC microcavity taken at 10 K (blue line) and 300 K (red line). Inset: high-resolution μ-PL spectrum of the fundamental mode M1with quality factor of 8700. (b) µ-PL spectra: black line without polarization, red line with horizontal polarization and blue line with vertical polarization. Insets: SEM image of the L3 PhC cavity and polar plot of cavity modes intensities as a function of polarization angle. (c) µ-PL spectra of a single QD, showing X and XX emission lines. (d) X and XX PL intensities as a function of laser excitation power. (e) X and XX transitions recorded at 0° (red) and 90°(black) polarization angles, showing vanishing fine-structure splitting.
(a) μ-PL spectra of L3 PhC microcavity taken at 10 K (blue line) and 300 K (red line). Inset: high-resolution μ-PL spectrum of the fundamental mode M1with quality factor of 8700. (b) µ-PL spectra: black line without polarization, red line with horizontal polarization and blue line with vertical polarization. Insets: SEM image of the L3 PhC cavity and polar plot of cavity modes intensities as a function of polarization angle. (c) µ-PL spectra of a single QD, showing X and XX emission lines. (d) X and XX PL intensities as a function of laser excitation power. (e) X and XX transitions recorded at 0° (red) and 90°(black) polarization angles, showing vanishing fine-structure splitting.

Li­te­ra­tu­re

Si­li­con-ba­sed quan­tum dots

Left: InAs QDs embedded in silicon matrix (in cooperation with PDI Berlin). Right: Light emission from single inAs/GaAs core-shell QDs directly grown on silicon.
Left: InAs QDs embedded in silicon matrix (in cooperation with PDI Berlin). Right: Light emission from single inAs/GaAs core-shell QDs directly grown on silicon.

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GaAs-ba­sed quan­tum dots

 (a & b) Single-photon emission and X lifetime from single QD grown by droplet epitaxy (in cooperation with HU Berlin). (c) Quality factor enhancement in coupled resonators (in cooperation with Uni. Magdeburg and IFW Dresden).
(a & b) Single-photon emission and X lifetime from single QD grown by droplet epitaxy (in cooperation with HU Berlin). (c) Quality factor enhancement in coupled resonators (in cooperation with Uni. Magdeburg and IFW Dresden).

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Site-con­trol­led quan­tum dots on pre-pat­ter­ned GaAs and si­li­con sub­stra­tes

Left: Site-controlled QDs on GaAs substrates. Right: III-V nanostructures localized in the patterned silicon nanoholes.
Left: Site-controlled QDs on GaAs substrates. Right: III-V nanostructures localized in the patterned silicon nanoholes.

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