Wavelength-tunable 40-GHz picosecond harmonically mode-locked fiber laser source

We demonstrate a novel 40-GHz mode-locked fiber laser that utilizes a single active device to provide both gain and mode-locking. The laser produces pulses as short as 2.2 ps, is tunable over a 27-nm band centered at 1553 nm, and exhibits long-term stability without cavity-length feedback control. The pulse train at 1556 nm was used in a 40-Gb/s transmission experiment over 45 km with a low 0.4-dB power penalty.     

Multilayer power printed structures suitable for controlling EMI noises generated in power converters

Electromagnetic interference (EMI) noises generated in power converters are diffused on the surface of conductors. This means influences occur from radiated EMI noises emitted from power transmission lines as well as conducted EMI noises transmitted from them. EMI noises diffusing on the surface of conductors are generally difficult to control using conventional concentrated constant theory. Thus, a new approach based on distributed constant circuit theory is needed in order to control EMI noises. A power converter structure to control EMI noises using multilayer power printed circuit technology is studied in this paper. A structure which can control EMI noises should simultaneously satisfy two conditions, i.e., one to shut down and one to attenuate EMI noises. The structure satisfying these conditions is studied through simulations using the Transmission-Line Modeling Method. The simulations show that the diffusion of EMI noises is controlled by dividing the flow of currents produced by EMI noises into the horizontal and perpendicular directions. That is, the horizontal current flow is controlled inside using the differences in the resistance produced from differences between inner and outer diameter of power transmission lines and the perpendicular current flow can be controlled by properly designing the thickness of the dielectric layer sandwiched between P-and N-power transmission lines with the symmetrical structure. Moreover, it is confirmed by simulations and experiments that the attenuation of EMI noises is affected by the width of the power transmission lines. It is expected that the results obtained in this paper can provide important rules when designing power converters with EMI noise control functions which use the multilayer power printed circuit technology.     

Reliability investigation of 0.07-/spl mu/m InGaAs-InAlAs-InP HEMT MMICs with pseudomorphic In/sub 0.75/Ga/sub 0.25/As channel

The authors have investigated the reliability performance of G-band (183 GHz) monolithic microwave integrated circuit (MMIC) amplifiers fabricated using 0.07-/spl mu/m T-gate InGaAs-InAlAs-InP HEMTs with pseudomorphic In/sub 0.75/Ga/sub 0.25/As channel on 3-in wafers. Life test was performed at two temperatures (T/sub 1/ = 200 /spl deg/C and T/sub 2/ = 215 /spl deg/C), and the amplifiers were stressed at V/sub ds/ of 1 V and I/sub ds/ of 250 mA/mm in a N/sub 2/ ambient. The activation energy is as high as 1.7 eV, achieving a projected median-time-to-failure (MTTF) /spl ap/ 2 /spl times/ 10/sup 6/ h at a junction temperature of 125 /spl deg/C. MTTF was determined by 2-temperature constant current stress using /spl Delta/G/sub mp/ = -20% as the failure criteria. The difference of reliability performance between 0.07-/spl mu/m InGaAs-InAlAs-InP HEMT MMICs with pseudomorphic In/sub 0.75/Ga/sub 0.25/As channel and 0.1-/spl mu/m InGaAs-InAlAs-InP HEMT MMICs with In/sub 0.6/Ga/sub 0.4/As channel is also discussed. The achieved high-reliability result demonstrates a robust 0.07-/spl mu/m pseudomorphic InGaAs-InAlAs-InP HEMT MMICs production technology for G-band applications.     

Hot carrier analysis in low-temperature poly-Si thin-film transistors using pico-second time-resolved emission microscope

We have analyzed degradation of N-channel thin-film-transistor (TFT) under dynamic stress using a pico-second time-resolved emission microscope. We have successfully detected emission at pulse fall edge for the first time. Emission intensity increased with the decrease of pulse fall time. As the degradation depended on the pulse fall time, this dependence clearly illustrates that hot electrons are the dominant cause of the degradation under dynamic stress. Based on these dependences, we proposed a model considering electron traps in the poly-Si.     

Electrical and photoelectric properties of electrochemically fabricated SnO2/Cd0.4Zn0.6S/CdTe solar cells

Solar cells based on SnO₂/Cd_0.4Zn_0.6S/CdTe heterostructures are fabricated by electrochemical deposition, and the dependences of their electrical and photoelectric properties on the thermal annealing conditions are studied. It is shown that thermal annealing reduces the tunnel currents by almost two orders of magnitude. The best conditions of thermal annealing are determined (t = 300°C and τ = 9 min). These conditions provide the highest photosensitivity of the heterostructures under study (I _sc ≈ 21.2 mA/cm², U _oc ≈ 813 mV, and η = 14.7%).     

All-optical seed pulse extraction for packet synchronization based on self-induced effects in a vertical-cavity semiconductor gate

Self-induced effects in a passive polarization-independent vertical-cavity semiconductor gate are investigated numerically and experimentally. We demonstrate all-optical seed-pulse extraction for synchronization of differential phase-shift keying and ON-OFF keying packets at 10 Gb/s. Our results provide evidence that vertical-cavity gates, exploiting saturable absorption in semiconductor quantum-wells, exhibit attractive performances in terms of efficiency, power consumption, and polarization independency.     

The colored revolution of bioimaging

This paper provides an overview of the main aspects of modern fluorescence microscopy. It covers the principles of fluorescence and highlights the key discoveries in the history of fluorescence microscopy. The paper also discusses the optics of fluorescence microscopes and examines the various types of detectors. It also discusses the signal and image processing challenges in fluorescence microscopy and highlights some of the present developments and future trends in the field.     

Self-oscillating dimmable electronic ballast

This paper presents a simple alternative for an electronic ballast operating in self-sustained oscillating mode with dimming capability for fluorescent lamps. A simple modification in one of the gate drivers side circuit allows the lamp to dim without compromising the simplicity, reliability, and low cost which characterize the self-oscillating electronic ballast (SOEB). A qualitative analysis is presented to explain the behavior of the proposed self-oscillating electronic ballast with dimming feature. In addition, the stability and the key equations for the design are derived using the extended Nyquist criterion and describing function method. Experimental results from two 40-W electronic ballasts are presented to demonstrate the performance and to validate the analysis carried out.     

Smooth profile generation for a tile printing machine

In this paper a digital filter is proposed for the generation of smooth set points for motion control systems. The proposed nonlinear filter produces profiles with bounded velocity and acceleration starting from rough reference signals (steps and ramps). An actual implementation of the filter for a tile printing machine is presented and experimental results are reported.     

LiNbO3 optical waveguides formed in a new proton source

Proton-exchanged planar waveguides have been fabricated on Z-cut and X-cut lithium niobate crystals by using a new proton source formed by a mixture of benzoic and adipic acids. Waveguide index profiles and optical characteristics have been obtained at different values of the adipic-benzoic acid concentration ratio. The samples have been structurally characterized by Raman and infrared (IR) absorption spectroscopy and double-crystal X-ray diffraction. Good quality samples have been fabricated by using 30 mol% ratio dilution, showing very low scattering levels (<0.1 dB/cm), relatively high electrooptic coefficient (r₃₃=0.88 pm/V), and low relative percentage of interstitial protons (26%). The main factor limiting the waveguide optical properties is the substitutional-interstitial proton ratio, which can be easily controlled to produce good quality waveguides. A demonstration of the repeatability of the exchange process in the acid mixture is also provided