Analysis of electro-optic switches with series-coupled multiple microring resonators

In terms of the coupled mode theory, microring resonance and electro-optic modulation princeple, a reasonable project is proposed for designing an electro-optic switch with the series-coupled multiple microring resonators. The simulation and optimization are performed at the resonant wavelength of 1550 nm. The results are as follows: the core size of the microring is 1.6 μm×1.6 μm, the confined layer between the core and the electrode is 1.6 μm, the thickness of the electrode is 0.15 μm, the radius of the m...     

Delay-Dependent Robust H ∞ Admissibility and Stabilization for Uncertain Singular System with Markovian Jumping Parameters

This paper investigates the problem of delay-dependent robust H _∞ admissibility and stabilization for uncertain singular time delay systems with Markovian jumping parameters. The considered systems are not necessarily assumed to be regular and impulse-free. In terms of the linear matrix inequality (LMI) approach, a delay-dependent stochastic admissibility criterion is given to ensure that the nominal system is regular, impulse-free and stochastically stable. Based on this criterion, the problem is solved. A numerical example is provided to demonstrate the efficiency of the proposed methods in this paper. This work is supported by the National “863” Key Program of China (2008AA042902), the National Natural Science Foundation of China (60874113), the Doctor Base Foundation of Colleges and Universities by the Ministry of Education of China (200802550007) and the Key Scientific Research and Innovation Program of Shanghai Education Committee (09zz66).     

P-μc-Si1-xGex ：H thin film by VHF-PECVD

In this paper, a series of boron doped microcrystalline hydrogenated silicon-germanium （p-μc-Si1-xGex：H） was deposited by very high frequency plasma-enhanced chemical vapor deposition （VHF-PECVD） from SiH4 and GeF4 mixtures. The effect of GeF4 concentration on films＇ composition, structure and electrical properties was studied. The results show that with the increase of GeF4 concentration, the Ge fraction x increases. The dark conductivity and crystalline volume fraction increase first, and then decrease. When the GC is 4%, p-μc-Si1-xGex：H material with high conductivity, low activation energy （σ= 1.68 S/cm, E8=0.047 eV）, high crystalline volume fraction （60%） and with an average transmission coefficient over the long wave region reaching 0.9 at the thickness of 72 nm was achieved. The experimental results were discussed in detail.     

A new type photonic crystal fiber with high birefringence

Highperformancepolarization maintainingfibers (PMFs)havepotentialforanumberofapplicationssuchashighbitratecommunicationsystem,PMfibre loopsforgyroscopesandsoon.Theindex guidingPCFs arecharacterizedbyaseriesofholesrunningthroughou thelengthofthefiberarrangedinamicroscalestructurearoundahighindexcore.Thisoffersanewpossibilityto createhighbirefringenceintheindex guidingPCFs,be causethestack and drawprocessallowstheformationoftherequiredsymmetricorasymmetricmicrostructure andtheindexcontrasto…     

A Credit-Based On-Demand QoS Routing Protocol Over Bluetooth WPANs

The quality-of-service (QoS) communication that supports mobile applications to guarantee bandwidth utilization is an important issue for Bluetooth wireless personal area networks (WPANs). In this paper, we address the problem of on-demand QoS routing with interpiconet scheduling in Bluetooth WPANs. A credit-based QoS (CQ) routing protocol is developed which considers different Bluetooth packet types, because different types of Bluetooth packets have different bandwidth utilization levels. This work improves the bandwidth utilization of Bluetooth scatternets by providing a new interpiconet scheduling scheme. This paper mainly proposes a centralized algorithm to improve the bandwidth utilization for the on-demand QoS routing protocol. The centralized algorithm incurs the scalability problem. To alleviate the scalability problem, a distributed algorithm is also investigated in this work. The performance analysis illustrates that our credit-based QoS routing protocol achieves enhanced performance compared to existing QoS routing protocols.This work was supported by the National Science Council of the Republic of China under grant nos. NSC-92-2213-E-194-022 and NSC-93-2213-E-194-028. Yuh-Shyan Chen received the B.S. degree in computer science from Tamkang University, Taiwan, Republic of China, in June 1988 and the M.S. and Ph.D. degrees in Computer Science and Information Engineering from the National Central University, Taiwan, Republic of China, in June 1991 and January 1996, respectively. He joined the faculty of Department of Computer Science and Information Engineering at Chung-Hua University, Taiwan, Republic of China, as an associate professor in February 1996. He joined the Department of Statistic, National Taipei University in August 2000, and joined the Department of Computer Science and Information Engineering, National Chung Cheng University in August 2002. Dr. Chen served as Co-Editors-in-Chief of International Journal of Ad Hoc and Ubiquitous Computing (IJAHUC), Editorial Board Member of Telecommunication System Journal, International Journal of Internet Protocol Technology (IJIPT) and The Journal of Information, Technology and Society (JITAS). He also served as Guest Editor of Telecommunication Systems, special issue on “Wireless Sensor Networks” (2004), and Guest Editor of Journal of Internet Technology, special issue on “Wireless Internet Applications and Systems” (2002) and special issue on “Wireless Ad Hoc Network and Sensor Networks” (2004). He was a Vice Co-Chair, Wireless IP Symposium of WirelressCOM2005, USA (2005) and a Workshop Co-Chair of the 2001 Mobile Computing Workshop, Taiwan. Dr. Chen also served as IASTED Technical Committee on Telecommunications for 2002–2005, WSEAS International Scientific Committee Member (from 2004), Program Committee Member of IEEE ICPP'2003, IEEE ICDCS'2004, IEEE ICPADS'2001, ICCCN'2001–2005, MSN'2005, IASTED CCN'2002–2005, IASTED CSA'2004–2005, IASTED NCS'2005, and MSEAT'2003–2005. His paper wins the 2001 IEEE 15th ICOIN-15 Best Paper Award. Dr. Chen was a recipient of the 2005 Young Scholar Research Award given by National Chung Cheng University to four young faculty members, 2005. His recent research topics include mobile ad-hoc network, wireless sensor network, mobile learning system, and 4G system. Dr. Chen is a member of the IEEE Computer Society, IEICE Society, and Phi Tau Phi Society. Keng-Shau Liu received the M.S. degree in Computer Science and Information Engineering from National Chung Cheng University, Taiwan, Republic of China, in July 2004. His research includes wireless LAN, Bluetooth, and mobile learning.     

A 2× 2 SOI mach-zehnder thermo-optical switch based on strongly guided paired multimode interference couplers

A silicon-on-insulator 2× 2 Mach-Zehnder thermo-optical switch is developed based on strongly guided paired multimode interference couplers. The multimode-interference couplers were etched deeply for improving coupler characteristics such as self-imaging quality, uniformity and fabrication toierance. The proposed switch achieves good performances, including a low insertion loss of -11.0dB, a fiber-waveguide coupling loss of-4.3dB and a fast response speed measured to be 3.5 and 8.8 μs for raise and fall switching time, respectively.     

Flat-top silica-based arrayed waveguide grating with 40-channels

A wavelength multiplexer or demultiplexer plays ani mportant role in all wavelength division multiplexing( WDM) system.Silica-basedarrayed waveguide gratings(AWGs) offer attractive featuresinthis area due to theadvantage of large output channels and lowlo…     

COMBINATORIAL DESIGN APPROACHES FOR AUTOMATIC TEST GENERATION

The n-way combination testing is a specification-based testing criterion, which requires that for a system consisted of a few parameters, every combination of valid values of arbitrary n(n ≥ 2) parameters be covered by at least one test. This letter proposed two different test generation algorithms based on combinatorial design for the n-way coverage criterion. The automatic test generators are implemented and some valuable empirical results are obtained.     

Silica-based 71-channel arrayed waveguide grating

With the rapid increase of global information capaci-ty,all optical wavelength division multiplexing(WDM)networks are very attractive because they are capable ofprocessing broadband optical signals without convertingthem to electronic signals.Large channe…     

A novel current injected strained quantum well laser grown by MOVPE

Conventional long wavelength (1.3 and 1.55 μm emitting) GalnAsP alloy lasers suffer from two disadvantages. Firstly, carriers in the highest lying valence band have a heavy effective mass relative to carriers in the conduction band. This asymmetry leads to an increase in the carrier density required for lasing action to occur. Secondly, non-radia-tive recombination processes, such as Auger Recombination (AR) and Inter Valence Band Absorption (IVBA), which involve occupancy of the heavy-hole (HH) states, are thought to be significant in these materials. These again lead to higher thresholds and lower values ofT ₀than might otherwise be the case. Recently, there has been considerable interest in the prospect of “engineering” the band structure of a 1.5 μm emitting device so as to overcome these problems. It has been reported that for a quantum well under biaxial compression, the light-hole/heavy-hole (LH/HH) degeneracy at the gamma point will be lifted such that the highest lying valence band will be LH-like in the in-plane direction. This should reduce both the effective mass asymmetry and the thermal occupancy of the HH states, lowering the threshold carrier density and reducing the AR and IVBA rates. This paper describes MOVPE growth and characterisation of the first 1.55 μm emitting current injected strained layer laser structure. The active region contains 3.5 nm thick strained quantum wells of Ga_o.3In_o.7As situated in the central region of a quaternary waveguide and grown on InP. TEM micrographs and x-ray data demonstrate that the lattice mismatch (approximately 1%) has been accommodated elastically, without the formation of misfit dislocations. Broad area lasers have been fabricated with lengths of 200–1200 μm and threshold current densities as low as 930 Acm^-2 have been measured from the longer devices. Similar 1.55 μm emitting structures containing unstrained 7.5 nm thick Ga_o.47In_o.53As wells have also been grown and characterised for comparison. As yet, no significant improvement in either threshold current orT ₀has been observed for strained lasers over unstrained devices.     

VE-mobicast: a variant-egg-based mobicast routing protocol for sensornets

In this paper, we present a new “spatiotemporal multicast”, called a “mobicast”, protocol for supporting applications which require spatiotemporal coordination in sensornets. The spatiotemporal character of a mobicast is to forward a mobicast message to all sensor nodes that will be present at time t in some geographic zone (called the forwarding zone) Z, where both the location and shape of the forwarding zone are a function of time over some interval (t _start ,t _end ). The mobicast is constructed of a series of forwarding zones over different intervals (t _start ,t _end ), and only sensor nodes located in the forwarding zone in the time interval (t _start ,t _end ) should be awake in order to save power and extend the network lifetime. Existing protocols for a spatiotemporal variant of a multicast system were designed to support a forwarding zone that moves at a constant velocity, , in sensornets. To consider the path of a mobile entity which includes turns, this work mainly develops a new mobicast routing protocol, called the variant-egg-based mobicast (VE-mobicast) routing protocol, by utilizing the adaptive variant-egg shape of the forwarding zone to achieve high predictive accuracy. To illustrate the performance achievement, a mathematical analysis is conducted and simulation results are examined. Yuh-Shyan Chen received the M.S. and Ph.D. degrees in Computer Science and Information Engineering from the National Central University, Taiwan, Republic of China, in June 1991 and Jan. 1996, respectively. He joined the faculty of Department of CSIE, Chung-Hua University, Taiwan, in 1996. He joined the Department of Statistic, National Taipei University in Aug. 2000, and joined the Department of CSIE, National Chung Cheng University in Aug. 2002. Dr. Chen is an associate Professor from Aug. 2003. Since 2006, he has been a Professor at the Department of CSIE, National Taipei University, Taiwan. Dr. Chen served as Co-Editors-in-Chief of International Journal of Ad Hoc and Ubiquitous Computing (IJAHUC); Editorial Board Member of Telecommunication System; Guest Editor of Telecommunication Systems, special issue on “Wireless Sensor Networks” (2004). He was a Vice Co-Chair, Wireless IP Symposium of WirelressCOM, USA (2005); Workshop Co-Chair, IEEE AHUC06, Taiwan (2006); Program Co-Chairs, IFIP NCUS06, Korea (2006). Dr. Chen also served as Program Committee Member of ICPP’03, ICDCS’04, ICCCN’01–06, MSN’05, CCN’02–06, CSA’04 06, NCS’06, MSEAT’03–06, WASN06, USN06, MHNET06, PESYS06, ML06, IWWN06, UIC06, ICWMC06, and HWN-RMQ06; IASTED Technical Committee on Telecommunications (2002–2005); WSEAS International Scientific Committee Member (from 2004). His paper wins the 2001 IEEE 15th ICOIN-15 Best Paper Award. Dr. Chen was a recipient of the 2005 Young Scholar Research Award given by National Chung Cheng University to four young faculty members, 2005. His recent research topics include mobile ad-hoc network, wireless sensor network, and 4G system. Dr. Chen is a member of the IEEE Computer Society and Phi Tau Phi Society. Shin-Yi Ann received the B.S. degree in computer science and engineering from the National Taiwan Ocean University, Taiwan, Republic of China, in June 2002 and the M.S. degree in computer science and information engineering from National Chung Cheng University, Taiwan, Republic of China, in July 2004. His research interest includes wireless sensor network. Yun-Wei Lin received the B.S. degree in computer and information science from the Aletheia University, Taiwan, Republic of China, in June 2003 and the M.S. degree in computer science and information engineering from National Chung Cheng University, Taiwan, Republic of China, in July 2005. His research interests include mobile ad hoc network and wireless sensor network.     

Crystallization of μc-Si on plastic substrate by using a pulsed double-frequency YAG laser

Thin film transistors （TFTs） of microcrystalline silicon （μc-Si） can provide higher mobility and stability than that of a-Si and better uniformity than that of poly-Si TFTs, and it would be more suitable to be applied to larger-area AMOLEDs. By using 2coYAG laser ann. ealing, crystalline μc-Si thin film on plastic substrate has been investigated and the proper laser energy needed for crystallization has been indicated. It has been found that the dehydrogenation process at 300-450℃ for a few of hours could be omitted by decreasing the H content in the crystallization precursor, which is suitable for laser crystallization on plastic substrates. The crystalline volume fraction （Xc） and the grain size of the resulted μc-Si could be adjusted by controlling the laser energy. By this method, the μc-Si on plastic substrate with Xc and grain size is respectively 85% （at the maximum） and 50 nm.     

Epitaxial Lead Chalcogenides on Si for Mid-IR Detectors and Emitters Including Cavities

Lead chalcogenide (IV–VI narrow-gap semiconductor) layers on Si or BaF₂(111) substrates are employed to realize two mid-infrared optoelectronic devices for the first time. A tunable resonant cavity enhanced detector is realized by employing a movable mirror. Tuning is across the 4 μm to 5.5 μm wavelength range, and linewidth is <0.1 μm. Due to the thin (0.3 μm) PbTe photodiode inside the cavity, a higher sensitivity at higher operating temperatures was achieved as compared to conventional thick photodiodes. The second device is an optically pumped vertical external-cavity surface-emitting laser with PbTe-based gain layers. It emits at ∼5 μm wavelength and with output power up to 50 mW pulsed, or 3 mW continuous wave at 100 K.     

Maskless selective area growth of InP on Sub-μm V-groove patterned Si(001)

Low pressure metalorganic chemical vapor deposition of InP onexactly oriented Si(OOl) substrates with a periodic V-groove pattern of periodicity ≤1.2 μm using a two temperature growth sequence (400 and 640°C) is reported. Planar InP layers with extremely low defect density of 7 × 10⁴ cm⁻² are obtained. For InP on V-grooves of width g ≤1.0μm, a planar surface is formed after less than 1 μm of growth. Formation or suppression of antiphase domains (APDs) is a function of the widths of the (OOl)-oriented ridges. For s ≤1 μm, epilayers are single domain and the direction is oriented parallel to the grooves. At 400°C, nucleation starts homogeneously on {111}-sidewallsand (001)-facets. While heating up to 640°C, InP migrates into the grooves, depleting almost completely the (001)-facets. During growth of the main layer, first the V-grooves are filled up. Subsequently (001)-ridges are overgrown laterally or voids are formed on top of them. This mechanism is responsible for both planarization and APD-suppression. The surface migration length of InP on Si(001) at 640°C is estimated to be ≈0.5 μm.     

Status of HgCdTe Bicolor and Dual-Band Infrared Focal Arrays at LETI

In this paper we show the latest achievements of HgCdTe-based infrared bispectral focal plane arrays (FPAs) at LETI infrared laboratory. We present and compare the two different pixel architectures that are studied now in our laboratory, named “NPN” and “pseudo-planar”. With these two technologies, a wide range of system applications in dual-band detection can be covered. Advantages of both architectures will be pointed out. We also review performances obtained with these different architectures. The first one has been studied for several years in our laboratory, and we review results obtained on FPAs of size 256 × 256 pixels on a 25 μm pitch, in the MWIR/MWIR (3 μm/5 μm) range. Very high noise equivalent temperature difference (NETD) operability is obtained, at 99.8% for the λ_c = 3 μm band and 98.7% for the λ_c = 5 μm band. The second one has been developed more recently, to address other applications that need temporal coherence as well as spatial coherence. We show detailed performances measured on pseudo-planar type FPAs of size 256 × 256 pixels on a 30 μm pitch, in the MWIR/LWIR (5 μm/9 μm) range. The results are also very promising for these prototypes, with NETD as low as 15 mK for an integration time as short as 1 ms, and good operability. The main manufacturing issues are also presented and discussed for both pixel architectures. Challenging process steps are, firstly, molecular beam epitaxy (MBE) HgCdTe heterostructure growth, on large substrates (cadmium zinc telluride) and heterosubstrates (germanium), and, secondly, detector array fabrication on a nonplanar surface. In particular, trenches or hole etching steps, photolithography and hybridization are crucial to improve uniformity, number of defects and performances. Some results of surface, structural and electrical characterizations are shown to illustrate these issues. On the basis of these results, the short-term and long-term objectives and trends for our research and development are presented, in terms of pixel pitch reduction, wavelengths, and dual-band FPA size.     

Selective etch-back and growth of InGaAs ON (100) Fe:lnP by electroepitaxy

Selective etch-back prior to growth of InGaAs islands on SiO₂-masked (100)Fe-doped InP substrates was performed by electroepitaxy. The etch-back of the substrate and the growth of the layer was done at a constant furnace temperature of 640° C by passing a direct electric current from the melt to the substrate for etch-back and from the substrate to the melt for growth. The current density used was 1 to 20 A/cm² for a period from 15 to 60 min. The isolated InP regions were of various sizes (40 × 1000μm to 3000 × 3000μm), and different geometries (narrow and wide strips, square, circular). A uniform etch-back and uniform growth with excellent surface morphology was obtained on strips as wide as 200μm and on circles withd < 500μm. For islands with wider geometry, growth as well as etch-back were uniform up to 100–200μm from the periphery with excellent surface morphology. The etch-back and growth profiles are trapezoid-shaped and are not influenced by the difference in chemical activity between crystalline planes. The orientation dependence of the etch rate was {110} > {100} > {011} > {111} B > {111} A.     

High power output quasi-continuous-wave nanosecond optical parametric generator based on periodically poled lithium niobate

We report on a high power output quasi-continuous-wave nanosecond optical parametric generator （OPG） of congruent periodically poled lithium niobate （PPLN） pumped by a 1 064 nm acousto-optically Q-switched Nd-YVO4 laser （duration. 70 ns,repetition rate：45 kHz,spatial beam quality M2〈 1,3）. The OPG consists of a 38.7 mm long PPLN crystal with a domain period of 28.93 μm. With 5.43 W of average pump power the maximum average output power is 991 mW at 1 517.1 nm signal wave of the PPLN OPG.     

Deposition of GaN thin film on ZnO/Si by DIBD method

The GaNis a semiconductor material witha widefor-bidden band(Eg=3.36eV).It has many unique advan-tages such as high electron drift velocity,small dielectricconstant,goodthermal conduction et al.It is a favorablematerial for making electric devices with hi…     

Annealing kinetics and embrittlement of electrodeposited copper

Two types of 35 μm thick free-standing copper electrodeposits, one amenable to rapid annealing and the other responding sluggishly to thermal exposure, have been subjected to isothermal anneals at 100–250°C for up to 200 min. The apparent activation energy calculations from changes in mechanical properties yield 8.2 k cals/g atom for a “recovery” anneal of foil (i), and 15 k cals/g atom for a “recrystallization” anneal of foil (ii). This is in keeping with the values available in the literature for the electro and vapor deposits. Further, the electrodeposits display embrittlement, that is loss of ductility, at elevated temperature (180°C). The annealing gradually removes embrittlement, the removal rate depends upon the time/temperature parameters of the thermal exposure.     

Growth and characterizations of InP self-assembled quantum dots embedded in InAIP grown on GaAs substrates

We report the characteristics of InP self-assembled quantum dots embedded in In_0.5Al_0.5P on GaAs substrates grown by metalorganic chemical vapor deposition. The InP quantum dots show increased average dot sizes and decreased dot densities, as the growth temperature increases from 475°C to 600°C with constant growth time. Above the growth temperature of 600°C, however, dramatically smaller and densely distributed self-assembled InP quantum dots are formed. The small InP quantum dots grown at 650°C are dislocation-free “coherent” regions with an average size of ∼20 nm (height) and a density of ∼1.5 × 10⁸ mm⁻². These InP quantum dots have a broad range of luminescence corresponding to red or organge in the visible spectrum.