Low-Power, High-Speed InGaAs/InP Photoreceiver for Highly-Parallel Optical Data Links

Low-power photoreceivers based on InGaAs/InP heterojunction bipolar transistors (HBTs) and p-i-n diodes for highly-parallel optical data links have been designed, fabricated and characterized. The receivers and designed to operate from 980 nm to over 1.3 {mu}m and interface directly with 3.3 V CMOS. SPICE was utilized to investigate circuit topographies that minimize power dissipation while maintaining large signal operation required to interface directly with CMOS. Low-power dissipation of {approximately}10 mW/channel has been achieved at bit rates up to 800 Mbits/sec. Performance characteristics of discrete HBTs and of low-power photoreceivers fabricated with p-i-n/HBT circuits are reported

Multi-level interconnects for heterojunction bipolar transistor integrated circuit technologies

Heterojunction bipolar transistors (HBTs) are mesa structures which present difficult planarization problems in integrated circuit fabrication. The authors report a multilevel metal interconnect technology using Benzocyclobutene (BCB) to implement high-speed, low-power photoreceivers based on InGaAs/InP HBTs. Processes for patterning and dry etching BCB to achieve smooth via holes with sloped sidewalls are presented. Excellent planarization of 1.9 {micro}m mesa topographies on InGaAs/InP device structures is demonstrated using scanning electron microscopy (SEM). Additionally, SEM cross sections of both the multi-level metal interconnect via holes and the base emitter via holes required in the HBT IC process are presented. All via holes exhibit sloped sidewalls with slopes of 0.4 {micro}m/{micro}m to 2 {micro}m/{micro}m which are needed to realize a robust interconnect process. Specific contact resistances of the interconnects are found to be less than 6 {times} 10{sup {minus}8} {Omega}cm{sup 2}. Integrated circuits utilizing InGaAs/InP HBTs are fabricated to demonstrate the applicability and compatibility of the multi-level interconnect technology with integrated circuit processing

Ultra-low-power, long-wavelength photoreceivers for massively-parllel optical data links

An ultra-low-power, long-wavelength photoreceiver based on InGaAs/InP heterojunction bipolar transistors is reported. The photoreceivers were designed for massively parallel applications where low-power density is necessary for both electrical and thermal reasons. We demonstrate two-dimensional, four-by-four arrays of photoreceivers for free-space optical data links that interface directly with 3.3 V CMOS ASICs and dissipate less than 12 mW/channel; lower power is possible. Propagation delays of {approx}1 nsec were measured and large signal operation of 800 Mbits/sec is demonstrated. The array is on a 500 {mu}m pitch and can be easily scaled to much higher density. The photoreceivers can be utilized in both free-space and guided-wave applications

Low-power modular parallel photonic data links

Many of the potential applications for parallel photonic data links could benefit from a bi-directional Optoelectronic Multi-Chip Module (OEMCM), where the optical transmitter, receiver, and first-level interface electronics are combined into a single package. It would be desirable for such a module to exhibit low power consumption, have a simple electronic interface that can operate at a variety of speeds, and possess a capability to use interchangeable optics for a variety of external connections. Here, we describe initial results for a parallel photonic link technology that exhibits those properties. This link uses high-efficiency, back-emitting, two-dimensional Vertical Cavity Surface-Emitting Laser (VCSEL) arrays operating at 980 nm. The lasers are matched, via integrated microlenses, to corresponding monolithically-integrated photoreceiver arrays that are constructed in a InGaAs/InP Heterojunction Bipolar Transistor (HBT) technology. In initial breadboard-level tests, the photonic data channels built with these devices have been demonstrated with direct (3.3 V) CMOS drive of the VCSELs and a corresponding CMOS interface at the photoreceiver outputs. These links have shown electrical power consumption as low as 42 mW per channel for a 50% average duty cycle while operating at 100 Mb/s

Therapeutic management of chronic spontaneous urticaria in clinical practice: results from a pilot survey

BACKGROUND: The therapeutic approaches to patients with chronic spontaneous urticaria (CSU) differ among health care professionals and may be influenced by many factors. OBJECTIVES: This cross-sectional survey was aimed at evaluating physicians\u2019 attitudes regarding therapeutic management of CSU on clinical practice. METHODS: A study-specific questionnaire was administered to a group of physicians (n=21) with a specialist interest in CSU from different areas of Italy (Group A) and also to other physicians (n=25) who manage CSU only occasionally in their clinical activity (Group B). RESULTS: In case of ineffectiveness of second-generation antihistamines at standard doses, higher doses of the same drug were always or frequently prescribed by most physicians in both groups, and 64% in group B and one third in group A usually increased the dose up to twice. Old-generation antihistamines were never used in clinical practice by 14% of survey participants in group A and 24% in group B, with the remaining physicians reporting rare or occasional uses. The prescription of systemic corticosteroids appeared to be more common among physicians in group B. The question concerning the use of alternative drugs in refractory CSU produced different answers between the two groups. Costs and access to specialist reference centers were indicated as the most important barriers to the use of medications different from antihistamines. CONCLUSIONS: These preliminary results suggest that therapeutic approaches to CSU seem to be heterogeneous in clinical practice and could be at least in part conditioned by the different medical settings where physicians usually work

Chronic spontaneous urticaria in clinical practice: a pilot survey about attitudes and perceptions on assessment, diagnostic work-up and dietary management

Background: Chronic spontaneous urticaria (CSU) is a heterogeneous condition whose management can be complex and challenging. The 0bjectives is to evaluate physicians' attitudes regarding practical aspects of CSU management, including adherence to international guidelines, criteria and instruments for CSU assessment, prescription of laboratory investigations and role of dietary measures. Methods: A cross-sectional survey was conducted using a study-specific questionnaire. It was administered to a group of physicians with a specialist interest in CSU from different areas of Italy definable as "CSU experts" (Group A; n=21) and subsequently to other physicians who managed CSU only occasionally in their clinical activity (Group B; n=25). Results: The EAACI/GA\ub2LEN/EDF/WAO guidelines were considered very or moderately useful by the majority of participants. Significantly more physicians in group A reported that such guidelines were always followed in clinical practice (P=0.0008). Instruments for the assessment of CSU severity/activity and quality of life were used in clinical practice significantly more often by CSU experts as compared to group B. Dietary measures were frequently suggested for CSU patients by nearly three quarters of group B members and by only 5% of CSU experts (P<0.00001). When physicians were asked to indicate the type of laboratory examinations that were commonly performed in patients with longstanding and/or uncontrolled CSU, regardless of history, the investigations most frequently reported were full blood count and thyroid autoantibodies, followed by erythrosedimentation rate and/or C-reactive protein and thyroid function tests. Conclusions: The results of the present pilot survey seem to suggest the heterogeneity of the approaches used for CSU management in clinical practice