Coarse wavelength division multiplexer on silicon-on-insulator for 100 GbE

A four-channel cascaded MZl based de-multiplexer at O-band with coarse channel spacing of 20 nm and band flatness of 13 nm is demonstrated on silicon-on-insulator. The device shows a mean crosstalk and insertion loss below -16 dB and 2.5 dB

Road blocks on paleogenomes - polymerase extension profiling reveals the frequency of blocking lesions in ancient DNA

Although the last few years have seen great progress in DNA sequence retrieval from fossil specimens, some of the characteristics of ancient DNA remain poorly understood. This is particularly true for blocking lesions, i.e. chemical alterations that cannot be bypassed by DNA polymerases and thus prevent amplification and subsequent sequencing of affected molecules. Some studies have concluded that the vast majority of ancient DNA molecules carry blocking lesions, suggesting that the removal, repair or bypass of blocking lesions might dramatically increase both the time depth and geographical range of specimens available for ancient DNA analysis. However, previous studies used very indirect detection methods that did not provide conclusive estimates on the frequency of blocking lesions in endogenous ancient DNA. We developed a new method, polymerase extension profiling (PEP), that directly reveals occurrences of polymerase stalling on DNA templates. By sequencing thousands of single primer extension products using PEP methodology, we have for the first time directly identified blocking lesions in ancient DNA on a single molecule level. Although we found clear evidence for blocking lesions in three out of four ancient samples, no more than 40% of the molecules were affected in any of the samples, indicating that such modifications are far less frequent in ancient DNA than previously thought

Low-voltage Ge avalanche photodetector for highly sensitive 10Gb/s Si photonic receivers

We demonstrate low-voltage germanium waveguide avalanche photodetectors (APD) with gain-bandwidth product of 88GHz. A 7.1dB sensitivity improvement is demonstrated for an APD wire-bonded to a 10Gb/s CMOS transimpedance amplifier, at -6.2V APD bias

8x14Gb/s ring WDM modulator array with integrated tungsten heaters and Ge monitor photodetectors

An 8x14Gb/s wavelength-division multiplexed Si ring modulator array is presented with uniform channel performance. Tungsten heaters and Ge monitor photodetectors at the ring modulator drop ports are co-integrated to track and control the modulation quality

Low-voltage waveguide Ge APD based high sensitivity 10 Gb/s Si photonic receiver

We demonstrate low-voltage Ge waveguide avalanche photodetectors (APDs) with gain-bandwidth product over 100GHz. A 5.8dB avalanche sensitivity improvement (1x10(-12) bit error ratio at 10Gb/s) is obtained for the wire-bonded optical receiver at -5.9V APD bias

On the magnetic nature of electron transport barriers in tokamaks

The formation of internal transport barriers in the vicinity of rational magnetic surfaces in tokamaks with braided magnetic fields is studied for a simplified model of the perturbed magnetic field with a broad spatial spectrum and a monotonous shear profile. The island overlap criterion is used to derive a condition for barrier formation. This condition links the amplitude and the spectral width of the perturbation with the shear parameter. Numerical experiments with the MHD Monte-Carlo code E3D, where the problem of plasma heat conductivity is solved in 3D, confirm this formation of transport barriers in the case of a monotonous shear profile. Assuming that experimentally observed electron internal transport barriers are the result of local reduction of electron heat transport due to the magnetic field braiding, the amplitude and spectral width of magnetic perturbations are estimated for the tokamak RTP

Strike point splitting induced by the application of magnetic perturbations on MAST

Divertor strike point splitting induced by resonant magnetic perturbations (RMPs) has been observed on MAST for a variety of RMP configurations in a plasma scenario with Ip=750kA where those configurations all have similar resonant components. Complementary measurements have been obtained with divertor Langmuir probes and an infrared camera. Clear splitting consistently appears in this scenario only in the even configuration of the perturbation coils, similarly to the density pump-out. These results present a challenge for models of plasma response to RMPs.Comment: 9 pages, 4 figures, submitted to the proceedings of the 20th Conference on Plasma Surface Interactions, to be published in the Journal of Nuclear Material

Polarization-insensitive 5x20Gb/s WDM Ge receiver using compact si ring filters with collective thermal tuning

A 5x20Gb/s WDM Ge receiver with 300GHz channel spacing is presented. Uniform flat-top channel responses result in a 0.1A/W fiber-referenced responsivity and crosstalk better than-15dB for all channels and polarization states