Scalable wavelength-converting crossbar switches

Cataloged from PDF version of article.We report scalable low-power wavelength-converting Crossbar switches that monolithically integrate two-dimensional compact arrays of surface-normal photodiodes with quantum-well waveguide modulators. We demonstrate proof-of-concept, electrically reconfigurable 2 x 2 crossbars that perform unconstrained wavelength conversion across 35 nm in the C-band (1530-1565 nm), using only <4.3-mW absorbed input optical power, and with 10-dB extinction ratio at 1.25 Gb/s. Such wavelength-converting crossbars provide complete flexibility to selectively convert any of the input wavelengths to any of the output wavelengths at high data bit rates in telecommunication, with the input and output wavelengths being arbitrarily chosen within the C-band

Multifunctional integrated photonic switches

Cataloged from PDF version of article.Traditional optical-electronic-optical (o-e-o) conversion in today's optical networks requires cascading separately packaged electronic and optoelectronic chips and propagating high-speed electrical signals through and between these discrete modules. This increases the packaging and component costs, size, power consumption, and. heat dissipation. As a remedy, we introduce a novel, chip-scale photonic switching architecture that operates by confining high-speed electrical signals in a compact optoelectronic chip and provides multiple network functions on such a single chip. This new technology features low optical and electrical power consumption, small installation space, high-speed operation, two-dimensional scalability, and remote electrical configurability. In this paper, we present both theoretical and experimental discussion of our monolithically integrated photonic switches that incorporate quantum-well waveguide modulators directly driven by on-chip surface-illuminated photodetectors. These switches can be conveniently arrayed two-dimensionally on a single chip to realize a number of network functions. Of those, we have experimentally demonstrated arbitrary wavelength conversion across 45 nm and dual-wavelength broadcasting over 20 nm, both spanning the telecommunication center band (1530-1565 nm) at switching speeds up to 2.5 Gb/s. Our theoretical calculations predict the capability of achieving optical switching at rates in excess of 10 Gb/s using milliwatt-level optical and electrical switching powers

Self-aligning planarization and passivation for integration applications in III-V semiconductor devices

Cataloged from PDF version of article.This paper reports an easy planarization and passivation approach for the integration of III-V semiconductor devices. Vertically etched III-V semiconductor devices typically require sidewall passivation to suppress leakage currents and planarization of the passivation material for metal interconnection and device integration. It is, however, challenging to planarize all devices at once. This technique offers wafer-scale passivation and planarization that is automatically leveled to the device top in the 1-3-mum vicinity surrounding each device. In this method, a dielectric hard mask is used to define the device area. An undercut structure is intentionally created below the hard mask, which is retained during the subsequent polymer spinning and anisotropic polymer etch back., The spin-on polymer that fills in the undercut seals the sidewalls for all the devices across the wafer. After the polymer etch back, the dielectric mask is removed leaving the polymer surrounding each device level with its device top to atomic scale flatness. This integration method is robust and is insensitive to spin-on polymer thickness, polymer etch nonuniformity, and device height difference. It prevents the polymer under the hard mask from etch-induced damage and creates a polymer-free device surface for metallization upon removal of the dielectric mask. We applied this integration technique in fabricating an InP-based photonic switch that consists of a mesa photodiode and a quantum-well waveguide modulator using benzocyclobutene (BCB) polymer. We demonstrated functional integrated photonic switches with high process yield of >90%, high breakdown voltage of >25 V, and low ohmic contact resistance of similar to 10 Omega. To the best of our knowledge, such an integration of a surface-normal photodiode and a lumped electroabsorption modulator with the use of BCB is the first to be implemented on a single substrate

Self-aligned via and trench for metal contact in III-V semiconductor devices

A semiconductor processing method for the formation of self-aligned via and trench structures in III-V semiconductor devices (in particular, on InP platform) is presented, together with fabrication results. As a template for such self-aligned via and trench formations in a surrounding polymer layer on a semiconductor device, we make use of a sacrificial layer that consists of either a Si O2 dielectric hard mask layer deposited on the device layers or a sacrificial semiconductor layer grown on top of the device epitaxial layers (e.g., InP on an InGaAs etch stop), both laid down on the device layers before patterning the device geometry. During the semiconductor device etching, the sacrificial layer is kept as a part of the patterned structures and is, therefore, perfectly self-aligned. By selectively removing the sacrificial layer surrounded by the polymer that is etched back within the thickness of the sacrificial layer, an opening such as a via and a trench is formed perfectly self-aligned on the device top area in the place of the sacrificial layer. This process yields a pristine semiconductor surface for metal contacts and fully utilizes the contact area available on the device top, no matter how small the device area is. This approach thus provides as low an Ohmic contact resistance as possible upon filling the via and the trench with metal deposition. The additional use of a thin Si3 N4 protecting layer surrounding the device sidewalls improves the robustness of the process without any undesired impact on the device electrical passivation (or on the optical mode characteristics if the device also includes a waveguide). This method offers metal contacts scalable to the device size, being limited only by the feasible device size itself. This method is also applicable to the fabrication of other III-V based integrated devices. © 2006 American Vacuum Society

Electrically-reconfigurable integrated photonic switches

We report remotely electrically reconfigurable photonic switches that intimately integrate waveguide electroabsorption modulators with surface-normal photodiodes, avoiding conventional electronics. These switches exhibit full C-band wavelength conversion at 5 Gb/s and are remotely reconfigurable within tens of nanoseconds

Panic disorder severity scale: Reliability and validity of the Turkish version

We assessed the reliability and validity of the Turkish version of the seven-item Panic Disorder Severity Scale (PDSS). We recruited 174 subjects, including 104 with current DSM-IV panic disorder with (n = 76) or without (n = 28) agoraphobia, 14 with a major depressive episode, 24 with a non-panic anxiety disorder, and 32 healthy controls. Assessment instruments were Panic Disorder Severity Scale, Panic and Agoraphobia Scale, both the observer-rated (P&Ao) and self-rating (PAsr); Clinical Global Impression Scale (CGI); Hamilton Anxiety Scale, and Beck Depression Inventory. We repeated the measures for a group of panic disorder patients (n = 51) after 4 weeks to assess test-retest reliability. The internal consistency (Cronbach's alpha) of the PDSS was .92-94. The inter-rater correlation coefficient was .79. The test-retest correlation coefficient after 4 weeks was .63. In discriminant validity analyses, the highest correlation for PDSS was with P&Ao, P&Asr (r =. 87 and. 87, respectively) and CGI (r =. 76) and the lowest with Beck Depression Inventory (r =. 29). The cutoff point was six/seven, associated with high sensitivity (99%) and specificity (98%). This study confirmed the objectivity, reliability and validity of the Turkish version of the PDSS. (C) 2004 Wiley-Liss, Inc

Multifunctional integrated photonic switches for nanosecond packet-switched wavelength conversion

We report multifunctional integrated photonic switches that provide optical wavelength conversion across the C-band at 3.5 Gb/s that is electrically packet-switched within a reconfiguration time of <2.5ns. These switches also provide optical packet-switching in <300ps. © 2005 Optical Society of America

Integrated photonic switches for nanosecond packet-switched optical wavelength conversion

We present a multifunctional photonic switch that monolithically integrates an InGaAsP/InP quantum well electroabsorption modulator and an InGaAs photodiode as a part of an on-chip, InP optoelectronic circuit. The optical multifunctionality of the switch offers many configurations to allow for different optical network functions on a single chip. Here we experimentally demonstrate GHz-range optical wavelength-converting switching with only ∼10 mW of absorbed input optical power, electronically controlled packet switching with a reconfiguration time of <2.5 ns, and optically controlled packet switching in <300 ps. © 2006 Optical Society of America