含寄生网络的激光器小信号调制响应模拟新方法

在高速通信中应准确分析激光器高频调制响应需要计及寄生网络的影响。推导了激光器测试系统散射参数与本征响应传输函数之间的关系，提出用激光器散射参数扣除求取激光器本征响应和模拟激光器整体小信号调制响应的新方法。结合激光器的等效电路和速率方程分析，避免了单独测量寄生网络和估计有源区电路参数。对法布里-珀罗型激光器样品测试发现，仿真与实验的结果吻合。这一模拟方法简便快捷，准确性好。     

Broad-band simultaneous measurement of complex permittivity andpermeability using a coaxial discontinuity

A technique for simultaneously measuring the real and imaginary parts of both the permittivity and the permeability of a given material is discussed. A gap in a coaxial line is filled with the material under test. Complex permittivity and permeability are computed from the S-parameter (S₁₁ and S₂₁) measurement made on the gap, taking into account higher-order modes excited at the discontinuity. Measured ϵ_r and μ_r data for several materials are presented from 45 MHz up to 18 GHz. This technique shows good agreement between calculated and generally accepted values     

The 13CH3OH optically pumped far-infraredlaser: new lines and frequency measurements

We report 18 new laser lines from ¹³CH₃OH generated in an optically pumped far-infrared laser; the laser lines are in the range of 54.2-420 μm and are all characterized in wavelength, polarization relative to the pumping CO₂ radiation, and pump offset relative to the CO₂ center frequency. The frequencies of seven of these new lines along with 10 previously reported lines were measured by an accurate heterodyne technique, mixing them in a metal-insulator-metal (MIM) point contact diode, with another laser line of known frequency     

Nonharmonic large amplitude modulation of a semiconductor laser ina self-homodyne interferometric optical system

A self-homodyne interferometric optical system fed by a modulated semiconductor laser is analyzed theoretically and experimentally. Both the intensity and frequency modulation of the laser diode with large modulation index are considered. For nonharmonic modulation, the effect of the AM-FM transfer function of the laser diode is taken into account. Theoretical and experimental results obtained show good agreement. Applications of the system for the characterization of wideband optical detectors and the measurements of the FM response of the laser diode are discussed. By using triangular modulation, novel characterization techniques are proposed. Results obtained by these techniques are in good agreement with those obtained by other measurement techniques     

Accurate measurement of ground-ring inductance in ball grid arraypackage

A new technique has been developed to measure the ground-ring inductance in a ball grid array (BGA) package. A simple parallel LC circuit is used to model the ground-ring parasitics at frequencies up to 1 GHz. After connecting an SMA connector to the ground ring of the BGA package, a network analyser can be used to measure the reflection coefficient (S₁₁) up to 1 GHz from which the ground-ring inductance can be extracted. It has been found that the ground-ring inductance depends very strongly on the phase of S₁₁. This leads to the advantage of excellent accuracy for the extracted quantities. The experimental ground-ring inductance data for a variety of BGA packages are verified by Ansoft simulation results     

Scattering matrix approach for the design of microwave filters

A synthesis procedure, based on a distributed parameter model, for the design of microwave filters is presented in this paper. The frequency response of the filter is described in terms of the characteristic polynomial T₂₁=S₁₁/S₂₁ where S₁₁ and S₂₁ are the scattering parameters of the filter. Starting from the desired polynomial T₂₁, the design scheme directly yields the scattering parameters of the various junctions, which can be realized by any kind of discontinuity. The capability of synthesizing an arbitrary frequency response allows one to introduce the concept of a “predistorted” characteristic polynomial in order to compensate for the degradations caused by multimodal interactions, frequency dispersion, etc. Comparison with measured data of a Chebyshev-like eight-pole E-plane filter confirms the validity of the method also in the presence of losses     

A Ka-Band CMOS Wilkinson Power Divider Using Synthetic Quasi-TEM Transmission Lines

This work presents a Ka-band two-way 3 dB Wilkinson power divider using synthetic quasi-transverse electromagnetic (TEM) transmission lines (TLs). The synthetic quasi-TEM TL, also called complementary-conducting-strip TL (CCS TL), is theoretically analyzed. The equivalent TL model, whose production is based on the extracted results, is applied to the power divider design. The prototype is fabricated by the standard 0.18 mum 1P6M CMOS technology, showing the circuit size of 210.0 mumtimes390.0 mum without contact pads. The measurement results, which match the 50 Omega system, reveal perfect agreements with those of the simulations. The comparison reveals the following characteristics. The divider exhibits an equal power-split with the insertion losses (S₂₁ and S₃₁) of 3.65 dB. The return losses (S₁₁, S₂₂ and S₃₃) of the prototype are higher than 10.0 dB from 30.0 to 40.0 GHz.     

Frequency tunable monopole coupled loop antenna with broadside radiation pattern

A frequency tunable antenna made with an open-circuit monopole coupled loop antenna associated to a varactor diode is presented. The proposed antenna shows a 35.8% relative bandwidth, covering the 470?675 MHz frequency range. Theoretical and experimental results of S₁₁, radiation patterns and gain have been performed and show good agreement.     

2.5 dB NF 3.1-10.6 GHz CMOS UWB LNA with small group-delay variation

A 3.1-10.6 GHz ultra-wideband low-noise amplifier (UWB LNA) with excellent phase linearity property (group-delay variation is only plusmn 16.7 ps across the whole band) using standard 0.13 mum CMOS technology is reported. To achieve high and flat gain and small group-delay variation at the same time, the inductive peaking technique is adopted in the output stage for bandwidth enhancement. The UWB LNA achieved input return loss (S₁₁) of -17.5 to -33.6 dB, output return loss (S₂₂) of -14.4 to -16.3 dB, flat forward gain (S₂₂) of 7.92 plusmn 0.23 dB, and reverse isolation (S₁₂) of -25.8 to -41.9 dB over the 3.1-10.6 GHz band of interest. A state-of-the-art noise figure (NF) of 2.5 dB was achieved at 10.5 GHz.     

Long-wavelength (9.5-11.5 μm) microdisk quantum-cascade lasers

Quantum-cascade whispering-gallery-mode disk lasers emitting at 9.5-μm and 11.5-μm wavelength are reported. Taking advantage of the high-quality resonator (Q≈200), the threshold current density of disk lasers emitting at 9.5 μm is reduced below the value of the corresponding ridge waveguide geometry (J_th,disk=2.39 kA.cm ^-2 versus J_th,ridge=3.0 kA.cm^-2). Additionally, the increase in wavelength compared to previously reported disk lasers at 5.0 μm is a significant step toward the microcavity regime (by an effective scaling factor of 2.5, comparing identical disk sizes), disk diameters from 125 μm down to 20 μm are used to study the approach to the microcavity regime by size reduction. Far-field pattern measurements identify scattering from the pedestal as an important outcoupling mechanism for microdisk lasers. An excellent agreement between the measured and calculated free spectral range of the whispering gallery modes allows us to estimate the beta factor of the microdisks, resulting in β≈0.05 for a 20-μm diameter disk. A two-level rate equation model is evaluated for the quantum-cascade disk laser as a tool for a direct measurement of β. Nevertheless, the actual measurement is at present blurred by luminescence (light-emitting diode) from the disk center accompanied by an unbalanced carrier distribution between the whispering gallery laser and the center light-emitting diode     

Recursive simulation models of the semiconductor laser modulationcharacteristics for accurate performance evaluation of coherent opticalCPFSK systems

Modeling of the semiconductor laser nonuniform FM response and residual IM modulation is essential for the computer-aided design of coherent optical communication systems. This paper presents an accurate simulation model, in which the FM and IM responses are represented by recursive digital filters derived directly from measurements. A comparison with previous models of the bibliography reveals the advantages of the current approach. The proposed modeling procedure is applied in the case of a single-electrode DFB laser. This DFB model, in combination with a semi-analytical technique for the evaluation of the error probability, is used to study the influence of the modulation characteristics on the performance of a coherent heterodyne CPFSK system with differential receiver operating at 1 Gb/s. Theoretical and experimental results are in excellent agreement     

A new characterization of sub-μm parallel multilevelinterconnects and experimental verification

This paper describes the generation of a new universal design chart for submicron multilevel interconnection and its verification using test-structures. This has been developed to give the precise interconnect-capacitance for parallel submicron multilevel interconnections. Parasitic effects of a passivation film (Si₃N₄) on the interconnect capacitance have been also studied. The results of the test-structures designed have shown an excellent agreement with the design-chart with a maximum error of 8%. Furthermore, a simple propagation delay and response voltage model to a step voltage input have been developed incorporating the parallel-interconnect capacitance model. The new model is based on a lossy-transmission line equation and demonstrates an excellent agreement with RC lumped circuit simulations, resulting in a new simple and accurate prediction method for interconnect delay for use in VLSI timing design     

Poincaré Sphere Method for Optimizing the Phase Modulation Response of a Twisted Nematic Liquid Crystal Display

We report an experimental procedure for achieving spatial modulation of the phase of an input wave field with an off-the-shelf twisted nematic liquid crystal display. This method involves illumination of an addressed liquid crystal display (LCD) with circularly polarized light and measurement of the Stokes parameters of the outgoing beam as the applied voltage is changed. The analysis of the distribution of the polarization states in the S₁-S₂ plane suggests a simple way to optimize the liquid crystal phase response by means of a properly oriented quarter wave-plate followed by an analyzer. Laboratory results for a commercial display are presented. A phase modulation depth of 240deg is obtained at 514 nm with a residual intensity variation which is lower than 4%     

Theoretical and experimental investigations of a diode-pumpedquasi-three-level laser: the Yb3+-doped Ca4GdO(BO3)3 (Yb:GdCOB) laser

We present a theoretical and experimental analysis of a diode-pumped Yb³⁺-doped Ca₄GdO(BO₃)₃ (Yb:GdCOB) laser. A new model for a diode-pumped quasi-three-level laser is described. The effects of absorption saturation, temperature profile, and the beam quality M² factor of the pump diode have been taken into account, for the first time to our knowledge. We have obtained a good agreement between experimental measurements and theoretical calculations with two different pump wavelengths, 902 and 976 nm. Our model has given good predictions of the laser performances for different crystal temperatures and different M² factors of the pump beam. As much as 440 mW of output power (at 1082 nm) have been achieved for 640 mW of absorbed pump power at 976 nm, corresponding to one of the highest slope efficiencies (81%) ever obtained with Yb-doped lasers     

A microwave oscillation loop for dielectric constant measurement

We designed and analyzed a microwave oscillation loop formed by a dielectric loaded cavity, amplifiers and transmission lines for the dielectric constant measurement of samples at both room and very high temperature. An oscillation condition for an arbitrary loop is derived in S-parameter notation, by which the commonly used oscillation condition in loop phase and gain notation is proved to be valid only in the special case when either S₁₁=S₂₁=0 or S₂₂ =S₁₂=0. Based on the S-parameter oscillation condition, a theoretical model is established and verified with a discrepancy of less than 0.041% between the calculated and the measured oscillation frequencies. With this model, the loop characteristics are investigated. From the measured loop oscillation frequency, the cavity resonant frequency, and thereby the dielectric constant of the sample in the cavity, can be predicted. Based on this analysis, an active dielectrometer is constructed with resultant errors of less than 4% for ϵ'<20 and less than 11% for ϵ'<80. This dielectrometer requires no tuning and no external microwave power source. Moreover, a high power (>100 W) oscillation loop for the dielectric constant measurement of a microwave heated sample (1000°C) is developed     

Laser diodes in photon number squeezed state

A laser diode with an intrinsic layer as the space charge limited current region is expected to emit a low noise (less than the shot noise level) light. However, when one applies the intrinsic layer to the laser diode, severe difficulty is faced. Because the intrinsic layer has a very high resistivity, the applied voltage to operate the laser diode is too large and causes catastrophic damage to the laser diode. Here we propose novel laser diodes which emit a low noise light. The first is an AlGaAs laser diode having an undoped layer between the active layer and the cladding layer which acts as the space charge limited current region. Fano factor, F_m, of this laser diode is 28% smaller than the shot noise level (standard quantum limit, F_m=1) at 21 mA (output power, P₀=20 mW). The second one is an InGaAsP laser diode having two tunnel barrier layers whose bandgap energy is larger than that of the cladding layer. The region between the barriers acts as the space charge limited current region, Fano factor, F_m of this laser diode is 47% smaller than the shot noise level at 21 mA (P₀=10 mW). On the other hand, an AlGaAs laser diode with the two tunnel barrier layers has Fano factor, F_m which is 43% smaller than the shot noise level at 21 mA (P₀=20 mW). The calculated amplitude noise spectral densities of the latter two laser diodes are in good agreement with the calculated values from Langevin method. However, the calculated amplitude noise spectral density of the former laser diode does not agree with the calculated value from Langevin method. This disagreement is also discussed     

Invariance of S21/S12 and K-factor underparallel operation of linear two-port devices

Based on a generalized circuit model for parallel-operated amplifiers with linear two-port devices, it has been proved that the S-parameter ratio S₂₁/S₁₂ and hence MSG (maximum stable gain) are invariant as long as the devices have an identical value of S₂₁/S₁₂ and the input and output networks are reciprocal. The invariance of K factor has been shown to hold for two cases: (i) devices are identical and input/output networks are lossless and symmetric with respect to each device, and (ii) identical admittances are added to the networks of case (i) so as to connect every device port with each other. Thus at least in these two cases, MAG (maximum available gain) and U (unilateral gain) are invariant as well as MSG under parallel operation of linear two-port devices. The invariance of S₂₁/S₁₂ and hence MSG applies to a variety of parallel-operated amplifiers such as distributed amplifiers and linear power amplifiers     

Channel coding and decoding in a relay system operated with physical-layer network coding

This paper investigates link-by-link channel-coded PNC (physical layer network coding), in which a critical process at the relay is to transform the superimposed channel-coded packets received from the two end nodes (plus noise), Y₃ = X₁+ X₂+W₃, to the network-coded combination of the source packets, S₁ oplus S₂. This is in contrast to the traditional multiple-access problem, in which the goal is to obtain both S₁ and S₂ explicitly at the relay node. Trying to obtain S₁ and S₂ explicitly is an overkill if we are only interested in S1oplusS₂. In this paper, we refer to the transformation Y₃ rarr S₁ oplus S₂ as the channel-decoding- network-coding process (CNC) in that it involves both channel decoding and network coding operations. This paper shows that if we adopt the repeat accumulate (RA) channel code at the two end nodes, then there is a compatible decoder at the relay that can perform the transformation Y₃ rarr S₁oplusS₂ efficiently. Specifically, we redesign the belief propagation decoding algorithm of the RA code for traditional point-to-point channel to suit the need of the PNC multiple-access channel. Simulation results show that our new scheme outperforms the previously proposed schemes significantly in terms of BER without added complexity.     

Fabrication and Characteristics of 40-Gb/s Traveling-Wave Electroabsorption Modulator-Integrated DFB Laser Modules

We have developed 40-Gb/s traveling-wave electroabsorption-modulator-integrated distributed feedback laser (TW-EML) modules using several advanced technologies. First, we have adopted a selective area growth (SAG) method in the fabrication of the 40-Gb/s EML device to provide active layers for the laser and the electroabsorption modulators (EAMs) simultaneously. The fabricated device shows that the measured 3-dB bandwidth of electrical-to-optical (E/O) response reaches about 45 GHz and the return loss (S₁₁) is kept below -10 dB up to 50 GHz. For the module design of the device, we mainly considered electrical and optical factors. The measured S₁₁ of the fabricated 40 Gb/s TW-EML module is below -10 dB up to about 30 GHz and the 3-dB bandwidth of the E/O response reaches over 35 GHz. We also have developed two types of coplanar waveguide (CPW) for the application of the driver amplifier integrated 40 Gb/s TW-EML module, which is a system-on-package (SoP) composed of an EML device and a driver amplifier device in a module. The measured S₁₁ of the two-step-bent CPW is below -10 dB up to 35 GHz and the measured S₁₁ of the parallel type CPW is below -10 dB up to 39 GHz.     

基于红外TDLAS技术的高精度CO2同位素检测系统的研制

对天然气分布监测,高精度地检测CO₂同位素是非常重要的。采用可调谐二极管激光吸收光谱(TDLAS)技术,通过13CO₂/12CO₂在4.3 μm处的吸收谱线,实现高精度CO₂同位素检测。该检测系统由工作在连续波模式下的中红外间带级联激光器(ICL)、长光程多通池(MPGC)和中红外碲镉汞(MCT)探测器组成。针对13CO₂和12CO₂两条吸收谱线强度受温度影响的问题,研制了MPGC高精度温度控制系统。实验中,配置5种不同浓度的CO₂气体对检测系统进行标定,响应线性度可达0.999 6。结果表明,当积分时间为92 s时,同位素检测精度低至0.013 9‰,具备实际应用价值。