A new modulation technique for high data rate low power UWB wireless optical communication in implantable biotelemetry systems

We report on the development of a novel modulation technique for UWB wireless optical communication systems for application in a transcutaneous biotelemetry. The solution, based on the generation of short laser pulses, allows for a high data rate link whilst achieving a significant power reduction (energy per bit) compared to the state-of-the-art. These features make this particularly suitable for emerging biomedical applications such as implantable neural/biosensor systems. The relatively simple architecture consists of a transmitter and receiver that can be integrated in a standard CMOS technology in a compact Silicon footprint. These parts include circuits for bias and drive current generation, conditioning and processing, optimised for low-volt age/low-power operation. Preliminary experimental findings validate the new paradigm and show good agreement with expected results. The complete system achieves a BER less than 10-7, with maximum data rate of 125Mbps and estimated total power consumption of less than 3mW

Reply to Comment on: Hawking radiation from ultrashort laser pulse filaments

A comment by R. Schutzhold et al. raises possible concerns and questions regarding recent measurements of analogue Hawking radiation. We briefly reply to the opinions expressed in the comment and sustain that the origin of the radiation may be understood in terms of Hawking emission

Laser-assisted guiding of electric discharges around objects

Electric breakdown in air occurs for electric fields exceeding 34 kV/cm and results in a large current surge that propagates along unpredictable trajectories. Guiding such currents across specific paths in a controllable manner could allow protection against lightning strikes and high-voltage capacitor discharges. Such capabilities can be used for delivering charge to specific targets, for electronic jamming, or for applications associated with electric welding and machining. We show that judiciously shaped laser radiation can be effectively used to manipulate the discharge along a complex path and to produce electric discharges that unfold along a predefined trajectory. Remarkably, such laser-induced arcing can even circumvent an object that completely occludes the line of sight

A new optical UWB modulation technique for 250Mbps wireless link in implantable biotelemetry systems

We propose a new UWB modulation technique for wireless optical communications in transcutaneous biotelemetry. The solution, based on the generation of sub-nanoseconds laser pulses, allows for a high data rate link whilst achieving a significant power reduction (energy per bit) compared to the state-ofthe- art. These features make this particularly suitable for emerging biomedical applications such as implantable neural/biosensor systems. The relatively simple architecture consists of a transmitter and receiver that can be integrated in a standard CMOS technology in a compact Silicon footprint (lower than 1mm^2 in a 0.18μm technology). These parts, optimised for low-voltage/low-power operation, include coding and decoding digital systems, biasing and driving analogue circuits for laser pulse generation and photodiode signal conditioning. Experimental findings with prototype PCBs have validated the new paradigm showing the system capabilities to achieve a BER less than 10^-9 with data rate up to 250Mbps and estimated total power consumption lower than 5mW

Optically induced metal-to-dielectric transition in Epsilon-Near-Zero metamaterials

This work was supported by the EPSRC grant EP/ J004200/1. D.F. acknowledges financial support from the European Research Council under the European Union Seventh Framework Programme (FP/2007-2013)/ERC GA 306559 and EPSRC (UK, Grant No. EP/J00443X/1). L.C. and M.C. acknowledge the support from the People Programme (Marie Curie Actions) of the European Union’s FP7 Programme THREEPLE (GA 627478) and KOHERENT (GA 299522). A.C. and C.R. acknowledge support from U.S. Army International Technology Center Atlantic for financial support (Grant No. W911NF-14-1-0315).Epsilon-Near-Zero materials exhibit a transition in the real part of the dielectric permittivity from positive to negative value as a function of wavelength. Here we study metal-dielectric layered metamaterials in the homogenised regime (each layer has strongly subwavelength thickness) with zero real part of the permittivity in the near-infrared region. By optically pumping the metamaterial we experimentally show that close to the Epsilon-Near-Zero (ENZ) wavelength the permittivity exhibits a marked transition from metallic (negative permittivity) to dielectric (positive permittivity) as a function of the optical power. Remarkably, this transition is linear as a function of pump power and occurs on time scales of the order of the 100 fs pump pulse that need not be tuned to a specific wavelength. The linearity of the permittivity increase allows us to express the response of the metamaterial in terms of a standard third order optical nonlinearity: this shows a clear inversion of the roles of the real and imaginary parts in crossing the ENZ wavelength, further supporting an optically induced change in the physical behaviour of the metamaterial.Publisher PDFPeer reviewe

Biological effects of EF24, a curcumin derivative, alone or combined with mitotane in adrenocortical tumor cell lines

Background: Curcumin has numerous properties and is used in many preclinical conditions, including cancer. It has low bioavailability, while its derivative EF24 shows enhanced solubility. However, its effects have never been explored in adrenocortical tumor cell models. The efficacy of EF24 alone or combined with mitotane (reference drug for adrenocortical cancer) was evaluated in two adrenocortical tumor cell lines, SW13 and H295R. Method and Results: EF24 reduced cell viability with an IC50 (half maximal inhibitory concentration) of 6.5 \ub1 2.4 \ub5M and 4.9 \ub1 2.8 \ub5M for SW13 and H295R cells, respectively. Combination index (EF24 associated with mitotane) suggested an additivity effect in both cell lines. Cell cycle analysis revealed an increase in subG0/G1 phase, while motility assay showed a decrease in migratory cell capacity, and similarly, clonogenic assay indicated that EF24 could reduce colony numbers. Furthermore, Wnt/\u3b2-catenin, NF-\u3baB, MAPK, and PI3k/Akt pathways were modulated by Western blot analysis when treating cells with EF24 alone or combined with mitotane. In addition, intracellular reactive oxygen species levels increased in both cell lines. Conclusion: This work analyzed EF24 in adrenocortical tumor cell lines for the first time. These results suggest that EF24 could potentially impact on adrenocortical tumors, laying the foundation for further research in animal models

Blackbody emission from light interacting with an effective moving dispersive medium

Intense laser pulses excite a nonlinear polarisation response that may create an effective flowing medium and, under appropriate conditions, a blocking horizon for light. Here we analyse in detail the interaction of light with such laser-induced flowing media, fully accounting for the medium dispersion properties. An analytical model based on a first Born-approximation is found to be in excellent agreement with numerical simulations based on Maxwell's equations and shows that when a blocking horizon is formed, the stimulated medium scatters light with a blackbody emission spectrum. Based on these results, diamond is proposed as a promising candidate medium for future studies of Hawking emission from artificial, dispersive horizons

Controlling hybrid nonlinearities in transparent conducting oxides via two-colour excitation

Nanophotonics and metamaterials have revolutionised the way we think about optical space (epsilon, mu), enabling us to engineer the refractive index almost at will, to confine light to the smallest of the volumes, and to manipulate optical signals with extremely small footprints and energy requirements. Significant efforts are now devoted to finding suitable materials and strategies for the dynamic control of the optical properties. Transparent conductive oxides exhibit large ultrafast nonlinearities under both interband and intraband excitations. Here, we show that combining these two effects in aluminium-doped zinc oxide via a two colour laser field discloses new material functionalities. Owing to the independence of the two nonlinearities the ultrafast temporal dynamics of the material permittivity can be designed by acting on the amplitude and delay of the two fields. We demonstrate the potential applications of this novel degree of freedom by dynamically addressing the modulation bandwidth and optical spectral tuning of a probe optical pulse

Enhanced nonlinear refractive index in ε-near-zero materials

New propagation regimes for light arise from the ability to tune the dielectric permittivity to extremely low values. Here, we demonstrate a universal approach based on the low linear permittivity values attained in the ε-near-zero (ENZ) regime for enhancing the nonlinear refractive index, which enables remarkable light-induced changes of the material properties. Experiments performed on Al-doped ZnO (AZO) thin films show a sixfold increase of the Kerr nonlinear refractive index (n2) at the ENZ wavelength, located in the 1300 nm region. This in turn leads to ultrafast light-induced refractive index changes of the order of unity, thus representing a new paradigm for nonlinear optics.Publisher PDFPeer reviewe