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Ali Elshaari

Profile picture of Ali Elshaari

Associate Professor



About me

Dr. Ali Elshaari received his B.S. degree from University of Benghazi in Electrical Engineering (2007), and Ph.D. in Microsystems Engineering from Rochester Institute of Technology (2011).  His research is focused on hybrid quantum integrated photonics with the goal of realizing novel high performance quantum circuits for communication, sensing, and metrology that leverage the quantum nature of photons. Currently at KTH, Dr. Elshaari is actively working on combining single photon genration, manipulation and detection on a single CMOS compatible chip. Dr. Elshaari received number of awards recognizing his work, including VR starting grant from the Swedish research council, Marie Curie individual fellowship, and ATTRACT grant (Horizon 2020) for developing breakthrough technologies for science and society.

Selected publications:

  • Elshaari A. W., Skalli A., Gyger S., Nurizzo M., Schweickert L., Esmaeil Zadeh I., Svedendahl M., Steinhauer S., Zwiller V., ''Deterministic Integration of hBN Emitter in Silicon Nitride Photonic Waveguide'' Advanced Quantum Technologies, 2100032 (2021) Adv. Quantum Technol., 2100032 (2021) (Journal cover)
  • Gyger S., Zichi J., Schweickert L., Elshaari A. W., Steinhauer S., Covre da Silva S. F., Rastelli A., Zwiller V., Jöns K. D., Errando-Herranz C. ''Reconfigurable photonics with on-chip single-photon detectors'' Nature Communcations 1408, 12 (2021)
  • Elshaari A. W., Pernice W., Srinivasan K., Benson O., Zwiller V., ''Hybrid integrated quantum photonic circuits'' Nature Photonics, 14, 285-298 (2020)
  • Elshaari A. W., Büyüközer E., Zadeh I. E., Lettner T., Zhao P., Schöll E., Gyger S., Reimer M. E., Dalacu D., Poole P. J., Jöns K. D., Zwiller V. "Strain-tunable quantum integrated photonics", Nano Lett. 18, 12, 7969-7976 (2018)
  • Elshaari A. W., EsmaeilZadeh I., Fognini A., Reimer M. E., Dalacu D., Poole P. J., Zwiller V., Jöns K. D., " On-chip single photon filtering and multiplexing in hybrid quantum photonic circuits", Nature Communications 8, 379 (2017)
  • Esmaeilzadeh I., Elshaari A. W., Jöns K. D., Fognini A., Dalacu D., Poole P. J., Reimer M. E., Zwiller V., "Deterministic integration of single photon sources in silicon based photonic circuits",Nano Lett. 16 (4), 2289–2294 (2016)

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  • Hybrid Quantum Photonics

We developed a hybrid process for integrating high quality single photon emitters in a CMOS compatible platform. The process is deterministic in terms of selecting the quantum emitter, using a nano-manipulator, and the design of the photonic circuit. The developed hybrid platform exploits the advantages of high quality single-photon sources grown on III-V platforms with well-developed silicon based photonics.  Moreover, a major problems with integrated quantum photonics is the suppression of excitation lasers and filtering of emission lines. This proved to be a considerably difficult task which hindered the demonstration of on-chip sub-Poissonian light without the use of external bulky filters. We experimentally demonstrated, all-on-chip, generation and filtering of single-photons. The emission from a nanowire QD embedded in a photonic waveguide is filtered with a tunable ring. The process was generalized, as shown in the figure, to multiplex two nanowires quantum emitters in a single waveguide coupled to an electrically tunable ring resonator filter.

We develop a site-controlled process to deterministically integrate hBN quantum emitters in silicon nitride photonic waveguides. The hybrid integration methods allows to intrdouce quantum light sources to photonic platforms with no inherent light emitting properties. hBN is an exciting quantum material with potential with capability of emitting single light particles with high quantum efficiency at room temperature , without the need of extreme refrigiration.

We realize a hybrid system combining site-controlled Cu2O micro-crystals and silicon nitride photonic circuits. In the work, we couple Cu2O exciton emission to a SiN waveguide,  the emission shows excellent quality on par with micro-crystals  grown on thermal oxide. The platform offers exciting possibilities through exploring rydberg excitons in Cu2O for strong light matter interaction, mediated by high order rydberg states in Cu2O.

We developed a strain tunable hybrid quantum photonic platform through fabricating silicon nitride photonic waveguides with preselected III-V single nanowire QDs, directly on a piezoelectric crystal substrate. A piezoelectric substrate sandwiched between two electrodes controls the emission frequency of a single-photon emitter and the pass frequency of a ring resonator by means of strain. By applying an electric field across the piezoelectric substrate, we stretched the photons wavelength and shifted the bandpass frequency of a ring resonator filter. The device shows excellent stability, suitable for locking to atomic memories due to the direct integration of the photonic layer on the piezoelectric substrate, no bonding is involved.

We perform bandgap dispersion eingeering of superconducting transmission lines to slow down RF signals to record speed of 0.0019 speed of light in vacuum. We use the slow RF transmission line for time division multiplexin go superconducting single photon detectors, the article is featured in APL Photonics.

We develop superconducting single photon detectors with high detection efficiencies, low dark counts, and high time resolution. The detectors are fabricated by patterning thin NbTiN layers on photonic integrated circuits. Using these detectors, we realized a fully integrated, proof of concept, quantum channel, combining nanowire single photon emitter, a silicon nitride waveguide, and a ring resonator filter terminated with a single photon detector.

We study both theoretically and experimentally the dynamic tuning of optical resoantors and its effects on a trapped single photon in an optical resonator. We show that the effect of changing the refractive index of the optical cavity on the photon is equavelant to changing the tension on a guitar string while a note is resonating. The dynamic tuning f the cavity results in changing the frequence of the trapped photon. We also show that this process is linear, within the adiabatic tuning limits.

  • Photonic-Analogue of Electromagnetically-Induced Transparency

On chip dynamic optical buffers and storage elements are difficult to realize in silicon photonics. The dynamic tuning of silicon circuitry involves introducing loss through free carrier dispersion effect, which limits the achievable storage time. We experimentally demonstrated a carrier free optical storage element in silicon using a photonic analogue of an atomic Electromagnetic-Induced-transparency. It is capable of arbitrarily storing and releasing a light pulse through dynamic tuning of a system of microcavities. The storage is performed through the creation of a supermode between the ring resonators with EIT peaks that can be opened and closed depending on the dynamic control of the system.

Accurate characterization of material properties such as the thermo-optic cofficient and second/third order nonlinearities are important for designing photonic integrated circuits. We performed quantitative study of SiN and SiO2 thermo-optic cofficients at low temperatures, which is important for quantum applications requireing cryogenic temperatures and low thermal budget. The low-temperature result of the thermo-optic coefficient is critical for providing design/operation guidelines for many important low-temperature photonic circuits. We find the Thermo-optic coefficients of PECVD silicon nitride and silicon oxide to be 2.51 + 0.08 E-5 K -1 and 0.96 + 0.09 E-5 K -1 at room temperature while decreasing by an order of magnitude when cooling to 18 K.


Degree Project in Applied Physics, Second Cycle (SK202X), examiner | Course web

Nanophotonics and Bionanophotonics (SK2560), teacher | Course web

Nanophotonics and Bionanophotonics (FSK3560), teacher | Course web

Optical Physics (SK2300), course responsible, teacher | Course web

Quantum Photonics (SK2900), teacher | Course web

Quantum Technology (SK2903), assistant | Course web

Solid State Physics (SK2758), assistant | Course web