Spin-orbit coupling of light in asymmetric microcavities
Optical spin-orbit coupling is known to occur in macroscopic open systems by the refraction across an interface or the propagation along helical waveguides. Here, we enable spin-orbit coupling of light confined to a closed path within an asymmetric optical microcavity and demonstrate a non-cyclic Berry phase acquired in a non-Abelian evolution. This work is relevant to fundamental studies and implies promising applications by manipulating photons in on-chip quantum devices.
Scalable entangled photon sources for the long haul
Constructing a quantum network relies on transferring entangled states over long distances. This scenario can be implemented by “swapping” the entanglement between wavelength-matched entangled photon sources. Semiconductor quantum dots are a promising candidate for this task. Howeve, there is a longstanding challenge on scalability. With an on-chip PMN-PT/silicon MEMS device, we can tune the entangled photon emission from a quantum dot by more than 3000 times of the radiative linewidth without spoiling the entanglement. This work removes a major stumbling block to entanglement swapping with quantum dots.
The fastest entangled photon sources come from IIN
Triggered sources of entangled photon pairs are key components in most quantum communication protocols. Here we demonstrate strain-tunable entangled-light-emitting-diodes with entanglement fidelities as high as 0.83. Electrically driven at the highest speed ever (400 MHz), these entangled photon sources emerge as promising devices for high data-rate quantum applications. This work was carried out in close collaboration with the Johannes Kepler University Linz, Austria.
Monolithic integration of vertical optical ring resonators
We demonstrate full integration of vertical optical ring resonators with silicon nanophotonic waveguides on silicon-on-insulator substrates to accomplish a significant step towards 3D photonic integration. The on-chip integration is realized by rolling up 2D differentially strained TiO2 nanomembranes into 3D microtube cavities on a nanophotonic microchip. In this vertical transmission scheme, resonant filtering of optical signals at telecommunication wavelengths is demonstrated and opens up interesting perspectives towards parallel and multi-routing data processing as well as high-throughput optofluidic sensing applications.
A. Madani et al., Opt. Lett. 40, 3826 (2015) URL PDF
A wavelength-tunable single-photon emitting diode
The first all-electrically operated wavelength-tunable single-photon source is demonstrated. The device consists of an ultra-thin light-emitting diode containing self-assembled quantum dots integrated onto a piezoelectric crystal.Triggered single photons are generated via injection of short electrical pulses at operation speeds up to 0.8 GHz. The wavelength of the emitted single-photons can be tuned over a broad range by the strain field from the piezoelectric crystal.Our work provides exciting perspectives towards high data rate quantum communications relying on remote electrically-driven single-photon sources.
Vertical add-drop filter made from a rolled-up ring resonator
A significant step towards integrated vertically rolled-up microcavities is demonstrated by interfacing SiO2 microtube optical ring resonators with tapered fibers. In this transmission configuration, resonant filtering of optical signals at telecommunication wavelengths is shown in subwavelength thick walled microcavities. Moreover, we present a four-port add-drop filter based on a lifted doubly interfaced vertically rolled-up microcavity. Our work opens opportunities for vertical resonant light transfer in 3D multi-level optical data processing as well as for massively parallel optofluidic analysis of biomaterials in lab-on-a-chip systems.
S. Böttner et al., Appl. Phys. Lett. 102, 251119 (2013) URL PDF
Diamond lattice photonic crystals from rolled-up membranes
A novel method for the fabrication of diamond lattice photonic crystals by rolling strained pre-patterned titania membranes is proposed. Using rolled-up nanotechnology, full band gap and highly customizable partial band gap photonic crystals are possible. A combination of finite element analysis and band structure calculations of our proposed system shows that photonic crystal bending negligibly influences the band gap, and that at least six windings are necessary. These findings motivate further efforts towards the fabrication of rolled-up photonic crystals.
M. R. Jorgensen et al., Phys. Rev. A. 87, 041803 (2013) URL PDF
Dynamic molecular processes detected by nanomembrane based microtube cavities
Dynamic molecular processes of water and ethanol are detected on the surface of rolled-up opto-chemical microtube resonators. Based on perturbation theory, quantitative information about structural changes in molecular layers are acquired. A robust ice-like H2O molecular layer on the microtube surface was revealed through detecting molecular interactions at room temperature. The ability of the self-assembled microtube cavities to probe molecular changes on the sensing surface constitutes a versatile platform for the detection of diverse surface phenomena in a label-free fashion.
L. B. Ma et al., Adv. Mater. 25, 2357 (2013). URL PDF
Engineering the properties of Quantum-Light-Emitting Diodes by strain
We present the first nanomembrane Quantum-Light-Emitting Diodes (QLEDs) integrated onto piezoelectric actuators. We demonstrate that the large strain fields provided by the piezoelectric actuators can be used to engineer the whole emission properties of the quantum emitters (semiconductor quantum dots) without degrading the electrical injection operation of standard QLEDs. The hybrid device presented here has the potential to form the basis of scalable electrically-driven sources for quantum communication.
R. Trotta et al., Adv. Mater. 24, 2668–2672 (2012) URL
Slowing down single photons from quantum dots
Nowadays, the vast majority of information is transferred by light in optical fibers. The single elementary particle of light is called a photon. The advantage of single photons is that they can carry and transfer quantum information over very long distances, enabling 100% secure communication, impossible to crack. We have successfully designed a new type of semiconductor material (quantum dots), which emit photons at a frequency that can be combined with rubidium atoms. By guiding the emitted light through the atoms the speed of the photons is reduced to less than 4% of the speed of light in vacuum. The breakthrough can enable the realization of quantum memories - an essential component in quantum information technology. Merging semiconductor and atomic physics in a hybrid interface opens the way to a series of novel experiments and research directions. For instance, quantum memories and quantum repeaters for quantum dot generated photons can now be fabricated. This work was carried out in close collaboration with the Kavli Institute of Nanoscience at Delft University of Technology in the Netherlands.
Spectral tunability of microtube resonators on glass
The tunability of optical resonant modes of spiral microtube cavities, rolled-up from square patterned SiO/SiO2 thin nanomembranes on glass substrates, is demonstrated experimentally by coating the tube walls by atomic layer deposition. Transverse-electric modes are observed for Al2O3 coatings thicker than approximately 20 nm, as revealed by linear polarization analysis of the emitted light. Such fine tunability, which is essential for realizing optical microdevices, brings a better understanding of the resonant modes in microtubular cavities, suggesting that the microtubes could be used in potential applications for on-chip components like filters and sensors.
Shaped tubular optical microcavities
We have fabricated tubular optical microcavities by releasing pre-defined stressed SiO/SiO2 bilayer nanomembranes from polymer sacrificial layers. Optical measurements at room temperature demonstrate that the resonant optical modes can be accurately tuned along the tube axes. The resonant modes shift to higher energies with decreasing number of tube wall rotations and thickness, which is well-described by simulations. Rolled-up tubular optical microcavities can be produced in large periodic arrays on arbitrary substrates and are therefore highly attractive for on-chip integration technologies.
Si/SiO microtube optical ring resonators
Rolled-up Si/SiO tubes show optically resonant emission in the visible spectral range at room temperature. The mode spacings are inversely proportional to the tube diameter, and the resonant modes recorded are strictly polarized along the tube axis. The Si/SiO microtube optical ring resonators can easily be integrated on a single chip and represent a major step towards Si-based optical signal processing.