Nanoscale diamond optomechanical devices allow light to be coherently coupled to mechanical resonators, providing a rich platform for optical information processing, with applications including memory, switching, sensing, and wavelength conversion. Recently, it’s been shown that they also allow optical control of quantum memories formed by impurities in the diamond crystal lattice. This interface, in which nanoscale vibrations excited by light drive spin transitions of the defects, enables photons at telecommunication wavelength to address quantum memories with no intrinsic optical transitions.
Femtosecond laser writing shows great potential for novel 3D photonic architectures and high quality NV- quantum emitters in the bulk of diamond. However, the direct writing method cannot achieve nanometric placement of NV- centers near the surface of diamond, which is required for certain quantum sensing tasks. We will demonstrate a hybrid approach where the advantages of 3D optical waveguides by femtosecond laser writing and precise and shallow placement of NV- centers by ion implantation will be combined to form an integrated quantum sensor with record high performance.
Nonlinear optics provides the functionality of wavelength conversion and switching that allows for photonic signal processing and bioimaging. A major obstacle for extreme photonic integration is the requirement to use ultrafast pulsed lasers or to work above the diffraction limit to activate nonlinear optical processes. Here we show that plasmonic enhancement and two dimensional materials provide a promising pathway to extreme photonic integration with nonlinear functionality in nanoscale while using diode lasers.
Diamond optomechanical devices combine excellent optical and mechanical properties, allowing coherent conversion of information between optical and mechanical domains. Furthermore, they host colour centres that can function as long-lived quantum memories and qubits. By creating precisely engineered diamond optical cavities that also support low loss mechanical resonances, we have succeeded in both reversibly storing information in diamond optomechanical devices, and in optomechanically controlling diamond spin qubits. This talk will review both the fabrication and experimental challenges that needed to be overcome to realize these goals and will discuss on-going efforts to create diamond optomechanical crystal devices.
Quantum networks enable a broad range of practical and fundamental applications. Experimental realization of such networks is hampered by many challenges, one of them being a lack of an efficient interface between stationary and flying qubits working at room temperature. We demonstrate an interface between ensembles of the nitrogen-vacancy centers in diamond and photons with wavelengths near 1550 nm. Photons are coupled to spins via local dynamical stress produced by optomechanical driving of a diamond microdisk. Our approach does not involve intrinsic optical transitions and can be easily adapted to many other colour centers.
Diamond cavity optomechanical devices enable coherent conversion of information between optical and mechanical domains, thanks to a combination of low optical and mechanical loss, the ability to support intense optical fields without suffering from multi-photon optical absorption, and enhanced optomechanical coupling arising from nanoscale device geometry. In this talk we will review our progress in using these devices to create optical memories, wavelength conversion devices, and phase sensitive all-optical switches.
Diamond’s nitrogen-vacancy (NV) center has been shown as a promising candidate for sensing applications and quantum computing because of its long electron spin coherence time and its ability to be found, manipulated and read out optically. An integrated photonics platform in diamond would be useful for NV-based magnetometry and quantum computing, in which NV centers are optically linked for long-range quantum entanglement due to the integration and stability provided by monolithic optical waveguides. Surface microchannels in diamond would be a great benefit for sensing applications, where NV centers could be used to probe biomolecules.
In this work, we applied femtosecond laser writing to form buried 3D optical waveguides in diamond. By engineering the geometry of the type II waveguide, we obtained single mode guiding from visible to the infrared wavelengths. Further, we demonstrate the first Bragg waveguide in bulk diamond with narrowband reflection. We show the formation of single, high quality NV centers on demand in ultrapure diamond using a single pulse from a femtosecond laser. With these building blocks in place, we fabricated an integrated quantum photonic circuit containing optical waveguides coupled to NV centers deterministically placed within the waveguide. The single NVs were excited and their emission collected by the optical waveguides, allowing easy interfacing to standard optical fibers. We also report high aspect ratio surface microchannels, which we will integrate with laser-written NVs and waveguides, paving the way for ultrasensitive, nanoscale resolution biosensors.
Diamond’s nitrogen-vacancy (NV) centers show great promise in sensing applications and quantum computing due to their long electron spin coherence time and their ability to be located, manipulated and read out using light. The electrons of the NV center, largely localized at the vacancy site, combine to form a spin triplet, which can be polarized with 532- nm laser light, even at room temperature. The NV's states are isolated from environmental perturbations making their spin coherence comparable to trapped ions. An important breakthrough would be in connecting, using waveguides, multiple diamond NVs together optically. However, the inertness of diamond is a significant hurdle for the fabrication of integrated optics similar to those that revolutionized silicon photonics. In this work we show the possibility of buried waveguide fabrication in diamond, enabled by focused femtosecond high repetition rate laser pulses. We use μRaman spectroscopy to gain better insight into the structure and refractive index profile of the optical waveguides.
A novel type of photonic crystal nanocavity nanocavity tailored to sensitively measure torques is theoretically investigated. Suspended low-mass elements (< pg) in the nanomechanical resonator are sensitive to environmental stimuli, such as a magnetic field from external sources or from embedded nanomagnetic systems. The torsional mechanical motion of these elements directly influences the optical field concentrated inside the optical nanocavity, resulting in a strong cavity optomechanical coupling rate up to 90 GHz/nm. The actuation of the mechanical resonator is readout with high sensitivity using evanescent coupling between the photonic crystal nanocavity and an optical fiber taper. A sub-100nm physical air gap in the middle of the nanobeam cavity allows torsional mechanical degrees of freedom as well as strong optical field confinement in a small mode volume. Numerical simulations show that high-Q ~ 106 optical cavities with a gap are possible. Potential applications incorporating these devices include sensitive magnetometry and probing the quantum properties of nanomagnetic systems.
We demonstrate coupling between the zero phonon line (ZPL) of nitrogen-vacancy centers in diamond and the
modes of optical micro-resonators fabricated in single crystal diamond membranes sitting on a silicon dioxide
substrate. A more than ten-fold enhancement of the ZPL is estimated by measuring the modification of the
spontaneous emission lifetime. The cavity-coupled ZPL emission was further coupled into on-chip waveguides
thus demonstrating the potential to build optical quantum networks in this diamond on insulator platform.
Nitrogen-vacancy centers in diamond are widely studied both as a testbed for solid state quantum optics and for
their applications in quantum information processing and magnetometry. Here we demonstrate coupling of the
nitrogen-vacancy centers to gap plasmons in metal nano-slits. We use diamond samples where nitrogen-vacancy
centers are implanted tens of nanometers under the surface. Silver nano-slits are patterned on the sample such
that diamond ridges tens of nanometers wide fill the slit gap. We measure enhancement of the spontaneous
emission rate of the zero photon line by a factor of 3 at a temperature of 8K.
The combination of the long electron state spin coherence time and the optical coupling of the ground electronic
states to an excited state manifold makes the nitrogen-vacancy (NV) center in diamond an attractive candidate
for quantum information processing. To date the best spin and optical properties have been found in centers
deep within the diamond crystal. For useful devices it will be necessary to engineer NVs with similar properties
close to the diamond surface. We report on properties including charge state control and preferential orientation
for near surface NVs formed either in CVD growth or through implantation and annealing.
The understanding of the coherence properties of photons emitted from negatively charged nitrogen-vacancy (NV)
centers in diamond is essential for the success of quantum information applications based on indistinguishable
photons. Here we study both the polarization of photons emitted from and the linewidth of photons absorbed by
single NV centers as a function of temperature T. We find that for T < 100 K the main dephasing mechanism
contributing to the linewidth broadening is phonon-mediated population transfer between the two excited orbital
states. The observed T5 temperature dependence of the population transfer rate and linewidth is experimental
evidence of a dynamic Jahn-Teller effect in the excited states.
We describe research on new optical structures in diamond for quantum information and sensing applications
based on the nitrogen-vacancy (NV) center. Results include etching experiments that reveal the vertical distribution
of NV centers produced by ion implantation and annealing, and gallium phosphide waveguides fabricated
on diamond with evanescent coupling to NV centers close to the diamond surface.
Spatial and k-space properties of subwavelength cross-section GaP waveguides supported by a diamond substrate are
analyzed theoretically. These waveguides are suitable for optically coupling to nitrogen vacancy centers located near the
surface of a single crystal diamond sample.
We observe the coupling of nitrogen-vacancy centers in single-crystal diamond to GaP waveguides on the diamond
surface. We describe the fabrication procedure and characterize the waveguide performance. Our results
indicate that the GaP/diamond hybrid system is a promising system for coupling nitrogen-vacancies to optical
microstructures for quantum information processing and sensing applications.
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