There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

Metal interconnections are expected to become the limiting factor for the performance of electronic systems as transistors continue to shrink in size. Replacing them by optical interconnections, at different levels ranging from rack-to-rack down to chip-to-chip and intra-chip interconnections, could provide the low power dissipation, low latencies and high bandwidths that are needed. The implementation of optical interconnections relies on the development of micro-optical devices that are integrated with the microelectronics on chips. Recent demonstrations of silicon low-loss waveguides, light emitters, amplifiers and lasers approach this goal, but a small silicon electro-optic modulator with a size small enough for chip-scale integration has not yet been demonstrated. Here we experimentally demonstrate a high-speed electro-optical modulator in compact silicon structures. The modulator is based on a resonant light-confining structure that enhances the sensitivity of light to small changes in refractive index of the silicon and also enables high-speed operation. The modulator is 12 micrometres in diameter, three orders of magnitude smaller than previously demonstrated. Electro-optic modulators are one of the most critical components in optoelectronic integration, and decreasing their size may enable novel chip architectures.

Micrometre-scale silicon electro-optic modulator

Optical technology is poised to revolutionize short-reach interconnects. The leading candidate technology is silicon photonics, and the workhorse of such an interconnect is the optical modulator. Modulators have been improved dramatically in recent years, with a notable increase in bandwidth from the megahertz to the multigigahertz regime in just over half a decade. However, the demands of optical interconnects are significant, and many questions remain unanswered as to whether silicon can meet the required performance metrics. Minimizing metrics such as the device footprint and energy requirement per bit, while also maximizing bandwidth and modulation depth, is non-trivial. All of this must be achieved within an acceptable thermal tolerance and optical spectral width using CMOS-compatible fabrication processes. This Review discusses the techniques that have been (and will continue to be) used to implement silicon optical modulators, as well as providing an outlook for these devices and the candidate solutions of the future.

/pdf/silicon-optical-modulators-578o7o6kvr.pdf

Silicon optical modulators

Silicon has long been the optimal material for electronics, but it is only relatively recently that it has been considered as a material option for photonics1. One of the key limitations for using silicon as a photonic material has been the relatively low speed of silicon optical modulators compared to those fabricated from III–V semiconductor compounds2,3,4,5,6 and/or electro-optic materials such as lithium niobate7,8,9. To date, the fastest silicon-waveguide-based optical modulator that has been demonstrated experimentally has a modulation frequency of only ∼20 MHz (refs 10, 11), although it has been predicted theoretically that a ∼1-GHz modulation frequency might be achievable in some device structures12,13. Here we describe an approach based on a metal–oxide–semiconductor (MOS) capacitor structure embedded in a silicon waveguide that can produce high-speed optical phase modulation: we demonstrate an all-silicon optical modulator with a modulation bandwidth exceeding 1 GHz. As this technology is compatible with conventional complementary MOS (CMOS) processing, monolithic integration of the silicon modulator with advanced electronics on a single silicon substrate becomes possible.

A high-speed silicon optical modulator based on a metal–oxide–semiconductor capacitor

We present an adaptive and dynamic hexagonal electro-optic phase array. The proposed device consists of a 2-dimensional hexagonal array of periodically inverted ferroelectric domains, along the z-axis, in lithium niobate crystals. The phase step is achieved via the application of an external electric field, along the z-axis, through transparent electrodes. Thanks to the electro-optic effect the phase step can changed with continuity over all the 0 to 2π by applying a variable voltage. In this way different patterns can be generated. In fact, one important property of this new proposed configuration of array iluminator is the intrinsic flexibility.

Electro-Optic Modulated Phase Array in Hexagonally Poled Lithium Niobate for Flexible Array Illuminator Device


 
 
 Several studies have evaluated the role of QRS duration (QRSd) or QRS narrowing as predictor of response to cardiac resynchronization therapy (CRT) in order to reduce non-responders. However, their results have been conflicting. In our study we analyzed retrospectively a cohort of patients from three centers to better correlate the association between the relative change in QRS narrowing index (QI) and clinical outcome and prognosis in patients who underwent CRT implantation.
 
 
 
 We included 398 patients in whom a CRT device was implanted in accordance with current guidelines in our three centres. Baseline clinical variables, echocardiographic parameters and pharmacological therapies were included. QRS duration before and after CRT implantation and QI [(pre implant QRS duration - QRS duration during CRT)/pre implant QRS duration × 100] were measured.
 
 
 
 Respect to echocardiographic follow up at 6 months, a significant improvement in all parameters (EF, LVEDV, LVESV) was observed. In 68% of patients, LVESV decreased by 10% or more. QI was significantly related to reverse remodelling (r = + 0.22; 95% CI: 0.11 to 0.32, p = 0.001). The cut-off value of QI that predicted best LV reverse remodelling after 6 months of CRT was 12.25% (sensitivity 65,49%, specificity 75%, area under the curve 0.7, p = 0.001).
 Regarding clinical outcomes at 12 mounths, a statistically significant difference was found between patients with a QI ≤ 12.25%, and those with a QI > 12.25%, in terms of NYHA class worsening (p 0,04). Another statistically significant difference was found analyzing the relation between QI and the causes of deaths, the mean of the QI of patients who died from cardiovascular causes was lower than patients who died of other causes. (p 0,0179).
 
 
 
 Therefore decrease in QRSd after CRT initiation was related to greater echocardiographic reverse remodelling and better outcome from death or cardiovascular hospitalization.
 Even if larger studies are needed, QI seems to be an easy-to- measure variable that could be used or evaluated to predict CRT response.


640 qrs index to predict cardiac resynchronization therapy response: a tricentric study

An electrically controlled filter for the selection of channels in a DWDM optical network is proposed. The wavelength selectivity is obtained by combining the electrical injection of free carriers in a forward biased p-i-n diode with a Bragg grating realized over the top of a Silicon on Insulator (SOI) rib waveguide. Apodization of the duty-cycle of the grating has been investigated in order to reduce the crosstalk between adjacent channels; in this way the performances of the filter in terms of spectral bandwidth for 100 GHz and 50 GHz DWDM spacing become attractive.

Numerical simulations of a silicon-based optoelectronic filter based on a Bragg grating and p-i-n diode for DWDM optical networks

— The authors analyze the feasibility of laser action inerbium-doped silicon devices. The recent experimental results onspontaneous light emission at 1.54 m from erbium-doped silicondiodes and theoretical calculation on Bragg grating technology areused to evaluate the best scenario performances. The effects of pro-cesses-inducederrorsonthethresholdconditionsaretakenintoac-count. They show that laser action in the Er:Si system is feasible.Index Terms— Bragg gratings, DBR, semiconductor laser,Si-based erbium laser. I. I NTRODUCTION I N THE LAST decade, silicon photonic integrated circuitshaveattractedaconsiderableinterest[1],[2].Infact,Siisthesemiconductor of choice for the fabrication of advanced elec-tronic devices. Hence, implementation of efficient optical func-tions in Si would allow us to use the mature and low cost SiUltra Large Scale Integration (ULSI) technology for the fabri-cation of integrated optoelectronics circuits. Recent works [2]have shown that infrared light ( m) can be guided,modulated, detected, and emitted in silicon. For several appli-cations, such as intra-chip or chip-to-chip optical interconnects,a key role would certainly be played by a silicon-based, narrowband, fixed frequency, coherent light source. So far, an Si-basedlaser has not been demonstrated. However, it has been recentlyshown [3]–[5] that efficient light emission at 1.54 m can beachieved using Er-doped Si diodes. In this work, we explore thefeasibility of a laser action at 1.54 m using Er-doped Si. In par-ticular, we propose a structure consisting of an Er-doped lightemitting diode, which can be used as an electrically pumped op-tical amplifier operating at 1.54 m, integrated into a rib wave-guide.In order to achieve a laser, a proper resonant optical cavityneeds to be realized. Although the cavity can be fabricated byincreasing the reflectivity of the input and output faces of thewaveguide by means of the deposition of thin films, this so-lution presents several drawbacks. In fact, in order to ensurea high performance optical cavity, any technological processwould hardly guarantee the perfect perpendicularity between

Feasibility Analysis of Laser Action in Erbium-Doped


 
 
 Myocardial Infarction with Non-Obstructive Coronary Arteries (MINOCA) is a pathology characterized by clinical evidence of myocardial infarction (according to the 4th Universal Definition of Myocardial Infarction) with normal or near-normal coronary arteries. This condition is extremely variable in etiology, pathogenic mechanisms, clinical manifestations, prognosis and therapeutic approach. Several studies have been described new markers as independent predictors of acute coronary events, severe coronary disease and major adverse cardiovascular events (MACEs), like remnants of cholesterol and monocyte/HDL-C ratio. These new markers have never been studied in MINOCA. The objective of the study is the evaluation of remnant cholesterol (RC) and monocyte/HDL-C ratio (MHR) in patients with MINOCA, in order to establish their validity as predictors of this event.
 
 
 
 We enrolled 114 patients who received diagnosis of MINOCA and performed a coronary angiography compared to 110 patients without previous cardiovascular events. Data were analyzed consulting medical records and related attachments. Remnants were calculated with the following formula: RC = Total Cholesterol (TC) – HDL-C – LDL-C. Since laboratory findings were obtained from blood samples at admission, we determined non-fasting remnants. The difference between levels of fasting and post-prandial circulating RC is irrelevant, so we could perform an accurate estimation of RC levels. Monocyte/HDL-C ratio was calculated by dividing monocytes count of peripheral blood by HDL-C levels; platelet/lymphocyte ratio was obtained by dividing platelet count by lymphocyte count. We have also calculated various lipoproteins ratios, like TC/HDL-C, LDL-C/HDL-C, Triglicerides/HDL-C, non-HDL-C/HDL-C.
 
 
 
 Patients with MINOCA had higher mean levels of RC (21,3 ± 10,6 vs 13,2 ± 7,7 mg/dL), monocyte/HDL-C ratio (23±0,009 vs 18,5± 8,3) and platelet/lymphocyte ratio (179,8 ± 246,1 vs 135 ± 64,7) rather than the control group. Only the mean values of all calculated lipoproteins ratios were lower in MINOCA patients. Statistical significance was achieved only in the remnant cholesterol evaluation.
 
 
 
 Higher levels of RC and monocyte/HDL-C ratio were found in patients with MINOCA, compared to patients without previous cardiovascular events. We also observed higher levels of platelet/lymphocyte ratio rather than the control group. Only various lipoprotein ratios resulted lower in MINOCA group. This finding could reflect the extreme heterogeneity underlying the pathogenetic mechanism of MINOCA. Unlike patients with MI-CAD, therefore, dyslipidemia could play a minor role in the pathogenic mechanism of MINOCA. In patients who receive diagnosis of MINOCA with a baseline alteration of the lipid profile and higher levels of cholesterol at admission as well, the evaluation of these parameters could play an important role, providing more detailed informations about their cardio-metabolic risk. Nevertheless, further studies with larger samples are needed to validate these parameters in clinical practice.


123 evaluation of remnant cholesterol levels and monocyte -to-hdl -cholesterol ratio in patients with myocardial infarction with normal coronary arteries

Giuseppe Coppola

Papers

Electro-Optic Modulated Phase Array in Hexagonally Poled Lithium Niobate for Flexible Array Illuminator Device

640 qrs index to predict cardiac resynchronization therapy response: a tricentric study

Numerical simulations of a silicon-based optoelectronic filter based on a Bragg grating and p-i-n diode for DWDM optical networks

Feasibility Analysis of Laser Action in Erbium-Doped

123 evaluation of remnant cholesterol levels and monocyte -to-hdl -cholesterol ratio in patients with myocardial infarction with normal coronary arteries