An integrated coupled-cavity 16-wavelength digitally tunable laser

We present a digitally tunable laser that was realized by coupling two wavelength periodical four-channel lasers. The lasers were coupled with a multimode interference coupler, in such a way that the device has a common intracavity output waveguide containing the full multiplexed signal. In the two laser cavities, 1 /spl times/ 4 PHASARs were used with a channel spacing of 100 and 400 GHz, respectively. By coupling each PHASAR to four semiconductor optical amplifiers, 4 /spl times/ 4 channels were generated. The measured SMSR for each of the 16 wavelengths is better than 40 dB.     

Uncooled DBR laser directly Modulated at 3.125 gb/s as athermal transmitter for low-cost WDM systems

An uncooled three-section tunable distributed Bragg reflector laser is demonstrated as an athermal transmitter for low-cost uncooled wavelength-division-multiplexing (WDM) systems with tight channel spacing. A /spl plusmn/0.02-nm thermal wavelength drift is achieved under continuous-wave operation up to 70/spl deg/C. Dynamic sidemode suppression ratio of greater than 35 dB is consistently obtained under 3.125-Gb/s direct modulation over a 20/spl deg/C-70/spl deg/C temperature range, with wavelength variation of as low as /spl plusmn/0.2 nm. This indicates that more than an order of magnitude reduction in coarse WDM channel spacing is possible using this source.     

High-mobility ultrathin strained Ge MOSFETs on bulk and SOI with low band-to-band tunneling leakage: experiments

For the first time, the tradeoffs between higher mobility (smaller bandgap) channel and lower band-to-band tunneling (BTBT) leakage have been investigated. In particular, through detailed experiments and simulations, the transport and leakage in ultrathin (UT) strained germanium (Ge) MOSFETs on bulk and silicon-on-insulator (SOI) have been examined. In the case of strained Ge MOSFETs on bulk Si, the resulting optimal structure obtained was a UT low-defect 2-nm fully strained Ge epi channel on relaxed Si, with a 4-nm Si cap layer. The fabricated device shows very high mobility enhancements >3.5/spl times/ over bulk Si devices, 2/spl times/ mobility enhancement and >10/spl times/ BTBT reduction over 4-nm strained Ge, and surface channel 50% strained SiGe devices. Strained SiGe MOSFETs having UT (T/sub Ge/<3 nm) very high Ge fraction (/spl sim/ 80%) channel and Si cap (T/sub Si cap/<3 nm) have also been successfully fabricated on thin relaxed SOI substrates (T/sub SOI/=9 nm). The tradeoffs in obtaining a high-mobility (smaller bandgap) channel with low tunneling leakage on UT-SOI have been investigated in detail. The fabricated device shows very high mobility enhancements of >4/spl times/ over bulk Si devices, >2.5/spl times/ over strained silicon directly on insulator (SSDOI; strained to 20% relaxed SiGe) devices, and >1.5/spl times/ over 60% strained SiGe (on relaxed bulk Si) devices.     

Arrayed waveguide grating of 70/spl times/60 /spl mu/m/sup 2/ size based on Si photonic wire waveguides

A miniature arrayed waveguide grating of 70/spl times/60 /spl mu/m/sup 2/ size consisting of Si photonic wire waveguides was designed using complete modelling in the finite-difference time-domain simulation. The device was fabricated onto a silicon-on-insulator substrate and evaluated in the wavelength range around 1.55 /spl mu/m. The clear demultiplexing characteristics were observed with a channel spacing of 11 nm and a loss of less than 1 dB.     

Lattice-form CWDM interleave filter using silica-based planar lightwave circuit

We demonstrate an eight-channel coarse wavelength-division-multiplexing interleave filter that employs a silica-based lattice-form filter. The filter incorporates phase-generating couplers to convert a conventional frequency interleave filter into a wavelength interleave filter with a constant channel spacing with respect to wavelength. We fabricated the designed interleave filter on a 1.5%-/spl Delta/ silica-based waveguide and realized a constant channel spacing of 20 nm with a wavelength displacement of within /spl plusmn/0.5 nm and an insertion loss of less than 1.7 dB over eight channels.     

硅基竖直耦合三环谐振波分复用器的特性

对1×N信道硅基竖直耦合三环谐振波分复用器的传输特性进行了分析,给出了光学传递函数的公式.在中心波长1550.918nm、波长间隔1.6nm的情况下,对其振幅耦合比率、波谱响应、分光光谱、插入损耗、信道间的串扰进行了数值模拟.计算结果表明,该器件具有以下良好性能:若取小环与信道间的振幅耦合比率为0.27,小环与大环间的振幅耦合比率为0.06,该器件具有箱形波谱响应,输出光谱中的次峰值已被抑制到-25dB,谐振峰平坦且陡峭,3dB带宽约为0.28nm,每条输出信道的插入损耗及串扰较小,插入损耗小于0.71dB,串扰可降至-53dB以下.     

A low-noise and gain-flattened amplifier composed of a silica-based and a fluoride-based Er/sup 3+/-doped fiber amplifier in a cascade configuration

We propose a novel low noise and gain-flattened Er/sup 3+/-doped fiber amplifier (EDFA) with a cascade configuration for wavelength division multiplexing (WDM) signals. In this configuration, a 1480-nm pumped fluoride-based EDFA is joined to a 980-nm pumped silica-based EDFA through an optical isolator. By adjusting the silica-based Er/sup 3+/-doped fiber length in the silica-based EDFA, we realized an excellent flat gain EDFA with a gain excursion of less than 0.9 dB and noise figure of 5.7/spl plusmn/0.2 dB, and a low noise EDFA with a noise figure of 5/spl plusmn/0.2 dB and a gain excursion of less than 1.4 dB, for 8 channel WDM signal in the 1532-1560-nm wavelength region.     

Multimode optical demultiplexer for DWDM with liquid crystal enabled functionalities

We have developed a liquid-crystal-based multimode optical demultiplexer (DEMUX) with additional functionalities such as switching and power equalization. Demultiplexing 16-channel 100-GHz-spaced signals into a 62.5-/spl mu/m multimode-fiber array is demonstrated. The central wavelength of each channel is designed according to the International Telecommunication Union grid. Adjacent channel crosstalk is less than -30 dB. The average 1and 3-dB passbands of the DEMUX are 12.5 and 22.5 GHz, respectively. A maximum extinction ratio of 16.2 dB is achieved. Different channels can be switched with rise and fall times of /spl sim/10 and /spl sim/70 ms, respectively. The outputs of the channels are equalized to -65 dBm. The variation between different channels reduced from /spl sim/10 dB to less than 0.5 dB.     

Electron beam direct-write tunable polymeric waveguide grating filter

We report a tunable electron beam direct-write polymeric waveguide Bragg grating filter based on a negative tone epoxy, The waveguide filter, with a 5-mm-long first-order grating, exhibits a transmission peak of -27 dB and a 3-dB bandwidth of /spl sim/0.8 nm, and there is an excellent agreement between experimental data and simulation results. The temperature response of the filter is also characterized. The rate of change of refractive index dn/dT is /spl sim/ -1.8 /spl times/ 10/sup -4///spl deg/1C at 1550-nm wavelength for both transverse electric and transverse magnetic polarizations, and the rate of change of peak wavelength d/spl lambda//dT is /spl sim/ -0.14 nm//spl deg/C. The tuning performance is comparable to other grating devices fabricated using multiple processing steps.     

Gating demultiplexer integrated with MSM detector array inInGaAs/AlGaAs/GaAs for WDM

The authors demonstrate the integration of a grating demultiplexer with curved output waveguides and a MSM photodetector array in InGaAs/AlGaAs/GaAs operating in the 1-μm wavelength region. The structure provides 38 channels with 1-nm channel spacing. The total loss, including scattering from the unmetallized grating, is about 17 dB. A channel crosstalk of -11 dB is obtained. The FWHM of the channel pass band is 0.5 nm     

Tunable polymer optical add/drop filter for multiwavelength networks

We present a polymer optical add/drop filter with a channel cross-talk of -18.5 dB, a free spectral range of 12.8 nm and a channel spacing of 400 GHz (4 channels) as well as a tunable optical filter with a free spectral range of 50 nm. Both filter designs are based on a synthesis which provides the minimum number of filter stages for a given channel crosstalk and number of channels. Wavelength tunability over the entire free-spectral range (FSR) is demonstrated with applied heating powers of 500 mW. For the narrow bandwidth filter we used a fluorinated high temperature stable polymer as the waveguiding material, which has proven to exhibit losses as low as 0.25 dB/cm at a wavelength of 1.55 /spl mu/m.     

Application of super-DWDM technologies to terrestrial terabit transmission systems

This paper describes application areas, elemental technologies, and the feasibility of terrestrial terabit wavelength division multiplexing (WDM) transmission systems based on super-dense wavelength division multiplexing (DWDM) technologies with a channel spacing of 12.5 GHz. Numerical simulation results quantitatively show that the merit of super-DWDM transmission is the elimination of the need for dispersion compensation over the several hundreds of kilometers of standard single-mode fiber (SMF). To support super-DWDM transmission, the prototype of a multiwavelength generator, which consists of just an intensity modulator and a phase modulator, is developed as a small-size WDM light source with high-wavelength stability. We use this prototype to conduct a 1.28-Tb/s (512 channels /spl times/ 2.5 Gb/s) transmission experiment with a channel spacing of 12.5 GHz over 320 km (80 km /spl times/ 4 span) of standard SMF without dispersion compensation. The potential and the feasibility of super-DWDM transmission with a channel spacing of 12.5 GHz for terrestrial systems is confirmed by the numerical simulation and the transmission experiment.     

Optical directional coupler based on Si-wire waveguides

We fabricated optical directional couplers with Si-wire waveguides and demonstrated their fundamental characteristics. Their coupling-length was extremely short, several micrometers, because of strong optical coupling between the waveguide cores. Wavelength demultiplexing functions were also demonstrated for devices with a long coupled waveguide. Optical output from a device 800 /spl mu/m long changed reciprocally with 2.5-nm wavelength spacing between the parallel and cross ports.     

1.6-μ m Multiwavelength Emission of an InAs–InGaAsP Quantum-Dot Laser

A multiwavelength laser with maximum signal-to-noise ratio up to 62 dB was demonstrated on the basis of a 461-m-long InAs-InGaAsP quantum-dot waveguide Fabry-Perot cavity chip. It has 24 channels with 0.8-nm channel spacing and 8.0-dB maximum channel intensity nonuniformity over a wavelength range from 1612 to 1632 nm. Its channel spacing irregularity due to linear intracavity waveguide dispersion was also investigated.     

A CMOS finite impulse response filter with a crossover traveling wave topology for equalization up to 30 Gb/s

This paper describes a fully differential 3-tap finite impulse response filter in 90-nm CMOS. A traditional traveling wave filter topology is modified to alleviate its inherent delay-bandwidth-gain tradeoffs. Each tap gain is comprised of two transconductors whose outputs superimpose with the same group delay, similar to a distributed amplifier. This doubles the bandwidth of the filter for a given tap spacing and gain. Digital control is provided for the tap gains, an integrated pre-amplifier, and tuning varactors. Coupled differential spirals are used in the delay lines to help the design fit into an area 600 /spl mu/m/spl times/500 /spl mu/m. A 1-V supply voltage and 25-mW power consumption are enabled by the use of parallel differential pairs for sign control of the transconductances instead of Gilbert cell amplifiers. The input return loss is better than 16 dB and the output return loss is better than 9 dB up to 30 GHz. Equalization of NRZ data over a coaxial cable channel was demonstrated up to 30 Gb/s, making it faster than any previously reported CMOS equalizer.     

Eight-channel microdisk CW laser arrays vertically coupled to common output bus waveguides

1.6-nm spectrally spaced eight-channel semiconductor microdisk laser arrays are presented, where high-Q disk lasing modes are vertically coupled out through a common bus waveguide. The spectral channel spacing is achieved by varying the disk resonator radii from 10.6 to 10.95 /spl mu/m. Typical linewidth of 0.25 nm and side-mode suppression ratio of -20dB are observed under continuous-wave lasing operation near /spl lambda/=1.51 /spl mu/m. This is the first demonstration of integrated microresonator laser arrays.     

Design criteria of high-Voltage lateral RESURF JFETs on 4H-SiC

Integrated power electronics on SiC have great potential in future power electronics applications. In this paper, a novel vertical channel lateral junction field-effect transistor structure with reduced surface electric field effect is proposed for the first time on 4 H-SiC to address existing challenges in lateral power devices on SiC. Based on an experimentally proven channel design, the detailed design procedure of such a device has been investigated. Design criteria to optimize device forward blocking as well as conduction characteristics are studied. Parameter tolerance and design windows are discussed considering practical issues in device fabrication. Designs that will lead to an optimized tradeoff between device breakdown voltage and specific on-resistance are shown. With an 8-/spl mu/m-long drift region, a 1535-V breakdown voltage and 3.24 m/spl Omega//spl middot/cm/sup 2/ specific on-resistance can be achieved. This represents a figure-of-merit of 737 MW/cm/sup 2/, about 100 times higher than that of the best normally off lateral power devices reported in the literature. The proposed device can be an attractive candidate for power integrated circuit on SiC.     

Nondegenerate four-wave mixing wavelength conversion in low-loss passive InGaAsP-InP quantum-well waveguides

Results on wavelength shifters based on four-wave mixing that operate in the 1.5-/spl mu/m regime are reported. These devices utilize the near-bandedge resonant enhancement in the third-order nonlinearity in passive InGaAsP-InP quantum-well waveguides. Over the erbium-doped fiber-amplifier gain band approximately -20 dB conversion efficiency was obtained with /spl ap/18-dBm CW pump power. The conversion efficiency was nearly constant for wavelength shifts up to /spl ap/26 nm (3.3 THz), limited by the phase-matching bandwidth of the 8.5-mm-long device.     

High-performance InP reflection-grating wavelength multiplexer

A high-performance InP reflection-grating wavelength multiplexer for the 1530-1560 EDFA fibre band is reported. The 8 channel 3.6 nm-spacing devices operated with 30-35 dB channel isolation, <0.04 wavelength precision, and <10 dB on-chip loss. Although realised with 3.6 nm spacings, the multiplexer may be adapted for channels as close as 0.5 nm     

基于SOI材料的阵列波导光栅的制作

采用ICP刻蚀的方法,在SOI材料上制作出了中心波长为 1. 5509μm、信道间隔为 200GHz的 5×5阵列波导光栅(AWG).测试中心波长与设计值相差 0. 28nm,测试波长间隔与设计值相差在 0. 02nm之内,相邻信道串扰接近10dB,信道插入损耗均匀性为 0. 7dB,测试结果表明该器件能够初步达到分波功能.