Energy decay plays a central role in a wide range of phenomena1,2,3, such as optical emission, nuclear fission, and dissipation in quantum systems. Energy decay is usually described as a system leaking energy irreversibly into an environmental bath. Here, we report on energy decay measurements in nanomechanical systems based on multilayer graphene that cannot be explained by the paradigm of a system directly coupled to a bath. As the energy of a vibrational mode freely decays, the rate of energy decay changes abruptly to a lower value. This finding can be explained by a model where the measured mode hybridizes with other modes of the resonator at high energy. Below a threshold energy, modes are decoupled, resulting in comparatively low decay rates and giant quality factors exceeding 1 million. Our work opens up new possibilities to manipulate vibrational states4,5,6,7, engineer hybrid states with mechanical modes at completely different frequencies, and to study the collective motion of this highly tunable system.

Ultralight mechanical resonators based on low dimensional materials are well suited as exceptional transducers of minuscule forces or mass changes. However, the low dimensionality also provides a challenge to minimize resistive losses and heating. Here, we report on a novel approach that aims to combine different two-dimensional (2D) materials to tackle this challenge. We fabricated a heterostructure mechanical resonator consisting of few layers of niobium diselenide (NbSe2) encapsulated by two graphene sheets. The hybrid membrane shows high quality factors up to 245,000 at low temperatures, comparable to the best few-layer graphene mechanical resonators. In contrast to few-layer graphene resonators, the device shows reduced electrical losses attributed to the lower resistivity of the NbSe2 layer. The peculiar low-temperature dependence of the intrinsic quality factor points to dissipation over two-level systems which in turn relax over the electronic system. Our high sensitivity readout is enabled by coupling the membrane to a superconducting cavity which allows for the integration of the hybrid mechanical resonator as a sensitive and low loss transducer in future quantum circuits.

Silicon photonics, due to its compatibility with the CMOS platform and unprecedented integration capability, has become the preferred solution for the implementation of next generation optical interconnects. However, current Si photonics require on-chip integration of several materials, including III-V for lasing, doped silicon for modulation and Ge for detection. The very different requirements of these materials result in complex fabrication processes that offset the cost-effectiveness of the Si photonics approach. We are developing an alternative route towards the integration of optoelectronic devices in Si photonic, relying on the use of single wall carbon nanotubes (SWNTs). SWNTs can be considered as a Si compatible material able to emit, modulate and detect near-infrared light. Hence, they hold a unique potential to implement all active devices in the Si photonics platform. In addition, solution processed SWNTs can be integrated on Si using spin-coating techniques, obviating the need of complex epitaxial growth or chip bonding approaches. Here, we report on our recent progress in the coupling of SWNTs light emission into optical resonators implemented on the silicon-on-insulator (SOI) platform.

Silicon photonics has emerged as a very promising technology platform for the implementation of high-performance, low-cost, ultra-compact circuits that can monolithically cointegrate electronic, opto-electronic and optic functionalities. However, Si neither has efficient light emission or detection in the telecom wavelength range, nor exhibits efficient electro-optic Pockels effect, hindering the implementation of integrated active devices like sources, detectors, or modulators. Current approaches relay on different materials to provide active functionalities in Si photonics, resulting in highly complex integration schemes that compromise cost-effectiveness. Semiconducting single-wall carbon nanotubes (SWNTs) are capable of emitting and detecting near-infrared light at room temperature and exhibit intrinsically fast electro-optic effects. They have also proven promising uses in micro-electronic devices, making them an ideal material to provide active functionalities in the Si photonic platform. In this work, we propose and experimentally validate the possible use of slot photonic waveguides to improve interaction between SWNTs and Si waveguide modes. Fabricated Si slot micro-ring shown an experimental ~ 60% photo-luminescence improvement compared to previous demonstration based on Si strip waveguide resonators. These results prove the potential of Si slot waveguides for the implementation of efficient SWNT-based Si photonic devices.

Semiconducting carbon nanotubes are an emerging material for photonics. We report on the enhancement of semiconducting carbon nanotubes photoluminescence with silicon microring resonators. Polyfluorene extracted semiconducting carbon nanotubes, deposited on such resonators, display sharp emission peaks superposed to nanotube emission, which is attributed to the interaction with the cavity modes of the microring resonators. Ring resonators with radii of 5 and 10  μm were used, to demonstrate the tuning of the spectral distance between two successive emission resonances. Quality factors ranged between 3000 and 4000 in emission. These are among the highest values reported so far for carbon nanotubes coupled with optical microcavity on the silicon platform, highlighting the bright perspectives for carbon nanotube photonics.

This paper reports on recent results on the integration of carbon nanotubes on the silicon photonic platform. Light coupling from carbon nanotubes in a fully integrated silicon resonator will be presented.

A deep-subwavelength imaging of the optical-guided modes localized in silicon microring resonators, obtained with a polarization-sensitive Fano-imaging technique, is demonstrated. We merge together near-field scanning optical microscopy and resonant forward scattering spectroscopy, leading to near-field hyperspectral imaging without the need of embedded light emitters or evanescent light coupling into the microring. The combined analysis of the observed Fano-like spectral line shapes and of the near-field intensity spatial distributions, supported by accurate numerical calculations, gives a clear discrimination between the TE and the TM modes.