On the temperature dependence of the London penetration depth in a superconductor.

Introduction The common notion is that in a clean superconductor the behavior of the London penetration depth ffi L at low temperatures is related fundamentally to the symmetry of the superconducting state and thus to the mechanism of pairing. In an s-wave superconductor with a true gap everywhere on the Fermi surface ffi L is expected to have an exponential temperature dependence while a power law variation of ffi L is treated as an evidence of nodes of some topology in the gap [3]. Although numerous measurements obtained by a variety of technique [4, 5, 6] appear to be consistent with the BCS result for singlet pairing, there are some indications [7, 8] that the low-temperature variation of ffi L obeys a power law and there exists [7, 9] a good physical argumentation that scattering on thermal acoustic phonons should give rise to a nonexponential temperature dependence o

A 50 Gb/s NRZ Modulated 850nm VCSEL Transmitter Operating Error Free to 90\ub0C

We report on the properties of an 850nm VCSEL transmitter running at 50Gb/s with NRZ modulation from 30\ub0C to 90\ub0C. This is the highest transmitter operating temperature at 50Gb/s for a VCSEL link of any wavelength. This achievement is made possible by a combination of a high speed VCSEL design and driver and receiver circuits that incorporate equalization. Without equalization, the highest temperature attained with BE

A 50 Gb/s NRZ Modulated 850nm VCSEL Transmitter Operating Error Free to 90°C

We report on the properties of an 850nm VCSEL transmitter running at 50Gb/s with NRZ modulation from 30°C to 90°C. This is the highest transmitter operating temperature at 50Gb/s for a VCSEL link of any wavelength. This achievement is made possible by a combination of a high speed VCSEL design and driver and receiver circuits that incorporate equalization. Without equalization, the highest temperature attained with BER <1E-12 is 57°C

70+ Gb/s VCSEL-based multimode fiber links

We report on an 850nm VCSEL based link operating error free to 71 Gb/s using an NRZ modulation format. This optical link uses custom transmitter and receiver ICs with 2-tap Feed Forward Equalization implemented in 130nm BiCMOS and GaAs based VCSELs and photodiodes. This paper covers new aspects of the circuits and packaging

A 71 Gb/s NRZ Modulated 850 nm VCSEL-based Optical Link

We report error free (BER<10-12) operation of a directly NRZ modulated 850 nm VCSEL link operating to 71 Gb/s. This is the highest error free modulation rate for a directly modulated laser of any type. The optical link consists of a 130 nm BiCMOS driver IC with 2-tap feed-forward equalization, a wide bandwidth 850 nm VCSEL, a surface illuminated GaAs PIN photodiode and a 130 nm BiCMOS receiver IC

Non-Gaussian noise effects in the dynamics of a short overdamped Josephson junction

The role of thermal and non-Gaussian noise on the dynamics of driven short overdamped Josephson junctions is studied. The mean escape time of the junction is investigated considering Gaussian, Cauchy-Lorentz and L\ue9vy-Smirnov probability distributions of the noise signals. In these conditions we find resonant activation and the first evidence of noise enhanced stability in a metastable system in the presence of L\ue9vy noise. For Cauchy-Lorentz noise source, trapping phenomena and power law dependence on the noise intensity are observed