We present a fully tunable multistage narrowband optical pole-zero notch filter that is fabricated in a silicon complementary metal oxide semiconductor (CMOS) foundry. The filter allows for the reconfigurable and independent tuning of the center frequency, null depth, and bandwidth for one or more notches simultaneously. It is constructed using a Mach-Zehnder interferometer (MZI) with cascaded tunable all-pass filter (APF) ring resonators in its arms. Measured filter nulling response exhibits ultranarrow notch 3 dB BW of 0.6350 GHz, and nulling depth of 33 dB. This filter is compact and integrated in an area of 1.75 mm 2. Using this device, a novel method to cancel undesired bands of 3 dB bandwidth of 910 MHz in microwave-photonic systems is demonstrated. The ultranarrow filter response properties have been realized based on our developed low-propagation loss silicon channel waveguide and tunable ring-resonator designs. Experimentally, they yielded a loss of 0.25 dB/cm and 0.18 dB/round trip, respectively.

Direct laser writing via two-photon polymerization (2PP) is an emerging micro-and nano-fabrication technique to prepare predetermined and architecturally precise hydrogel scaffolds with high resolution and spatial complexity. As such, these scaffolds are increasingly being evaluated for cell and tissue engineering applications. This article first discusses the basic principles and photoresists employed in hydrogel fabrication in 2PP, followed by an in-depth introduction of various mechanical and biological characterization techniques used to assess the fabricated structures. The design requirements for cell and tissue related applications are then described to guide the engineering, physicochemical, and biological efforts. Three case studies in bone, cancer, and cardiac tissues are presented that illustrate the need for structured materials in the next generation of clinical applications. This paper concludes by summarizing the progress to date, identifying additional opportunities for 2PP hydrogel scaffolds, and discussing future directions for 2PP research.

%'e have performed systematic tunneling measurements on two-dimensional quench-condensed films of Sn and Pb to investigate the destruction of superconductivity by localization effects. With increasing sheet resistance of the films, the energy gaps and T, 's decrease only slightly, but the gap edges broaden until the width becomes comparable to the gap. Associated with this broadening are low-temperature finiteresistance tails in the resistive transitions.Near the metal-insulator transition, both localization and interaction effects have a strong influence on the nature of conduction. ' These effects become even more important as the dimensionality of the system is reduced. Extensive transport, magnetotransport, and tunneling measurements in a variety of three-dimensional (3D), 2D, and 1D samples have resulted in a comprehensive description of these phenomena in the normal state. Recently, there has been a great deal of interest in the role these effects play in the destruction of the superconducting state of a disordered metal. Tunneling studies in 3D granular aluminum samples close to the metal-insulator transition' showed that the superconducting energy-gap edge broadens, possibly due to lifetime effects, as the resistivity of the sample increases.%hen the broadening is comparable to the gap, superconductivity disappears. In this paper, we report our results on a corresponding. 2D experiment using very thin quenchcondensed films of tin and lead.Two-dimensional systems are particularly appealing for studying localization and interaction effects because it is now understood that all the electronic states are localized and that these effects are some~hat independent of the material studied, ' depending only on the sheet resistance (Ro) of the sample. However, this assumption does not seem to hold for studies of the competition between these effects and superconductivity.Differences between our results on quench-condensed films and those of other experimental investigations on several diverse systems4 have led us to recognize the distinction between reducing the pair amplitude and reducing the phase coherence in the destruction of superconductivity. This experiment addresses the latter. Our earlier tunneling measurements5 on quenchcondensed tin films concentrated on the modification of the normal-metal density of states due to Coulomb interactions.In this experiment, we have focused on the changes in the superconducting excitation spectrum. The films were fabricated as previously described: A film of 99.99% Sn or Pb was evaporated onto fire-polished glass substrates held between 1.5 and 8 K. This film straddled four gold contacts and the aluminum (Al) counterelectrode which was previously deposited at room temperature and oxidized in air.Since we were interested in studying films of very high Rp, it was necessary to work with relatively high-resistance junctions. This was accomplished by oxidizing the Al in air for 20 min to obtain resistances &10000 0 for a 0.25 mm' junction area. The films were deposited in a low...

Diamond films and islands grown by chemical vapor deposition were implanted with boron, sodium, and carbon ions at doses of 10 14-10 15 /cm 2. This structural modification at the subsurface resulted in a significant reduction of the electric field required for electron emission. The threshold field for producing a current density of 10 mA/cm 2 can be as low as 42 V/m for the as-implanted diamond compared to 164 V/m for the high quality p-type diamond. When the ion-implanted samples were annealed at high temperatures in order to anneal out the implantation-induced defects, the low-field electron emission capability of diamond disappeared. These results further confirm our earlier findings about the role of defects in the electron emission from undoped or p-type doped diamond and indicate that the improved emission characteristics of as-implanted diamond is due to the defects created by the ion implantation process.

Our nerve interface addresses key challenges in interfacing with small nerves in the peripheral nervous system. Its small size, ability to remain on the nerve over sub-chronic timescales, and ease of implantation, make it a promising tool for future use in the treatment of disease.