Quantum-classical transition and quantum activation of ratchet currents in the parameter space

The quantum ratchet current is studied in the parameter space of the dissipative kicked rotor model coupled to a zero temperature quantum environment. We show that vacuum fluctuations blur the generic isoperiodic stable structures found in the classical case. Such structures tend to survive when a measure of statistical dependence between the quantum and classical currents are displayed in the parameter space. In addition, we show that quantum fluctuations can be used to overcome transport barriers in the phase space. Related quantum ratchet current activation regions are spotted in the parameter space. Results are discussed {based on quantum, semiclassical and classical calculations. While the semiclassical dynamics involves vacuum fluctuations, the classical map is driven by thermal noise.Comment: 6 pages, 3 figure

Diamond electro-optomechanical resonators integrated in nanophotonic circuits

Diamond integrated photonic devices are promising candidates for emerging applications in nanophotonics and quantum optics. Here we demonstrate active modulation of diamond nanophotonic circuits by exploiting mechanical degrees of freedom in free-standing diamond electro-optomechanical resonators. We obtain high quality factors up to 9600, allowing us to read out the driven nanomechanical response with integrated optical interferometers with high sensitivity. We are able to excite higher order mechanical modes up to 115 MHz and observe the nanomechanical response also under ambient conditions.Comment: 15 pages, 4 figure

Second harmonic generation in phase matched aluminum nitride waveguides

We demonstrate second order optical nonlinearity in aluminum nitride on insulator substrates. Using sputter-deposited aluminum nitride thin films we realize nanophotonic waveguides coupled to micro-ring resonators that simultaneously support cavity resonant modes for both visible and IR light. By using phase matched ring resonators, we achieve efficient second-harmonic generation and are able to generate up to 0.5uW of visible light on the chip with a conversion efficiency of -46dB. From the measured response we obtain a second order non-linear susceptibility (\c{hi}2) of 4.7pm/V. Our platform provides a viable route for realizing wideband linear and nonlinear optical devices on a chip

Reconfigurable nanophotonic devices using phase-change materials

This is the final version of the article. Available from E\PCOS via the URL in this record.Nanophotonic integrated circuits enable realizing functional optical devices using efficient design and fabrication routines. Their inherent stability and scalability makes them attractive for applications where optical signal processing is combined with coupling to external light stimuli. A majority of nanophotonic devices is, however, based on passive materials, which do not provide low-power tuning options or knobs for reconfigurability. We address this shortcoming by combining passive silicon nitride photonic devices with tunable phase-change materials [1]. Such a platform allows realizing both on-chip optical data storage [2] and active photonic components. Implementing on-chip photonic memories has been pursued for a long time, in particular for fabricating memory devices which are able to retain their state after the storage process. Photonic data storage would dramatically improve performance in existing computing architectures by reducing the latencies associated with electrical memories and potentially eliminating optoelectronic conversions. Furthermore, multi-level photonic memories with random access would allow for leveraging even greater computational capability. Thus far, photonic memories have been predominantly volatile, meaning that their state is lost once the input power is removed. We exploit hybrid photonic-phasechange materials to implement robust, non-volatile, all-photonic memories. By using optical near-field coupling within on-chip waveguides, we realize bit storage of up to eight levels in a single device that readily switches between intermediate states. We show that individual memory elements can be addressed using a wavelength multiplexing scheme. Such multi-level, multi-bit devices provide a pathway towards eliminating the von Neumann bottleneck and portend a new paradigm in all-photonic memory and non-conventional computing. We further show that such devices can be operated with short optical pulses, both for write and read operations