Temperature Dependence of Optical Gain and Loss in $lambda approx$ 8.2–10.2 $mu$m Quantum-Cascade Lasers

Temperature-dependent optical gain and waveguide loss have been measured for continuous-wave operated quantum-cascade lasers with wavelengths between 8.2 and 10.2 mum up to room temperature using the Hakki-Paoli method. The gain coefficient decreases with increasing temperature, and is close to the designed value for vertical transition lasers, but smaller than the designed value for diagonal transition lasers. The waveguide loss, however, is two to three times higher than calculated from free carrier absorption, and can be nearly constant, increase or decrease with temperature depending on sample design, which indicates that it is dominated by another mechanism other than plain free carrier absorption. One likely factor resulting in high waveguide loss is intersubband resonant absorption into higher lying states.     

Actively $Q$ -switched and Mode-Locked Diode-Pumped ${hbox {Nd:GdVO}}_{4}{hbox {--KTP}}$ Laser

By using a comparative simple configuration and a short cavity length, a diode-pumped actively Q -switched and mode-locked intracavity frequency doubled Nd:GdVO₄-KTP green laser with the modulation depth 100% was realized, from which the great average output power, the high efficiency were obtained and the mode-locked pulse inside the Q -switched pulse has a repetition rate of 476 MHz. Using the hyperbolic secant function methods and by considering the Gaussian distribution of the intracavity photon density, the influences of continuous pump rate, the upper state lifetime of the active medium and the turnoff time of the acousto-optic Q -switch, we proposed a developed rate equation model for actively Q -switched and mode-locked green lasers. With this developed model, the theoretical calculations are in good agreement with the experimental results and the width of the mode-locked green pulse is estimated to be about 185 ps.     

New Terahertz Laser Lines From $^{13}{hbox {CD}}_{3}{hbox {OH}}$ Pumped by Regular and Hot Bands ${hbox {CO}}_{2}$ Laser

We have used our new pulsed ${hbox {CO}}_{2}$ laser, operating both on regular and hot bands, to excite the $^{13}{hbox {CD}}_{3}{hbox {OH}}$ methanol isotopomer. This has lead to the observation of 13 new high-threshold far-infrared laser emissions (also identified as terahertz laser lines), with frequencies in the range between 24.11 and 102.56 cm$^{-1}$ (0.72–3.07 THz). The absorption transitions leading to these new FIR laser emissions have been located by observing the optoacoustic absorption spectra around the ${hbox {CO}}_{2}$ emissions. Here, we present these new far-infrared laser lines, characterized in wavelength, polarization, offset relative to the center of the pumping ${hbox {CO}}_{2}$ laser transition, relative intensity, and optimum operation pressure.      

A Tunable Pseudo-Differential OTA With $-78~{hbox {dB}}$ THD Consuming 1.25 mW

A novel linear tunable transconductor based on a combination of linearization techniques is presented. The input signal is transferred to the V-I conversion element by means of a high-speed feedback loop. Then, the linear V-I conversion is accomplished using quasi-floating-gate MOS transistors biased in the triode region. Finally, the absence of current mirrors in the signal path provides low sensitivity to transistor mismatch and reduces the harmonic distortion. The operational transconductance amplifier (OTA) was fabricated in a 0.5-mum CMOS technology with a single 3.3-V supply voltage. Experimental results show a total harmonic distortion of -78 dB at 1 MHz with 1-V_pp input signal. High linearity of the OTA is obtained over a two octave tuning range with only 1.25-mW power consumption.     

Reliability of Combined $k{hbox{-out-of-}}n$ and Consecutive $k_{c}{hbox{-out-of-}}n$ Systems of Markov Dependent Components

A combined $k{hbox{-out-of-}}n$ :$F(G)$ & consecutive $k_{c}{hbox{-out-of-}}n{hbox{:}}F(G)$ system fails (functions) iff at least $k$ components fail (function), or at least $k_{c}$ consecutive components fail (function). These models involve two common failure criteria, and can be used in various situations depending on the actual failure criteria involving consecutive components, or all components. Explicit formulas for the reliabilities of these systems are obtained for Markov dependent components using the distribution theory of runs. Some numerical results are also presented.      

A 3$,times,$5-Gb/s Multilane Low-Power 0.18-$mu{hbox {m}}$ CMOS Pseudorandom Bit Sequence Generator

A low-power, three-lane, pseudorandom bit sequence (PRBS) generator has been fabricated in a 0.18-mum CMOS process to test a multilane multi-Gb/s transmitter that cancels far-end crosstalk. Although the proposed PRBS generator was designed to produce three uncorrelated 12-Gb/s PRBS sequences, measurement results included in this paper have been obtained at only 5 Gb/s due to test setup limitations. The prototype employs a CMOS latch optimized to operate at frequencies close to the of the process and a current-mode logic (CML) MUX with modified active inductor loads for better high-speed large-signal behavior. In order to reduce the power consumption, a quarter-clock rate linear feedback shift register (LFSR) core in a power-efficient parallel architecture has been implemented to minimize the use of power-hungry, high-speed circuitry. Further power reduction has been achieved through the clever partitioning of the system into static logic and CML. In addition, the prototype design produces three uncorrelated 12-Gb/s data streams from a single quarter-rate LFSR core, thereby amortizing the power across multiple channels which lowers the power per channel by 3 times. The total measured power consumption at 5 Gb/s is 131 mW per lane and the calculated figure of merit per lane is 0.84 pJ/bit, which is significantly better than previously published designs.     

300-mm Low-${hbox {k}}$ Wafer Dicing Saw Development

With the further shrinking of IC dimensions, low- material has been widely used to replace the traditional SiO interlayer dielectric (ILD) in order to reduce the interconnect delay. The introduction of low- material into silicon imposed challenges on dicing saw process. ILD and metal layers peeling and its penetration into the sealing ring of the die during dicing saw are the most common defects. In this paper, the low- material structure and its impact on wafer dicing were elaborated. A practical dicing quality inspection matrix was developed to assess the cutting process variation. A 300-mm CMOS90-nm dual damascene low- wafer was chosen as a test vehicle to develop a robust low- dicing saw process. The critical factors (dicing blade, index speed, spindle speed, cut in depth, test pattern in the saw street, etc.) affecting cutting quality were studied and optimized. The selected C90 Dual damascene low- device passed package reliability tests with the optimized low- dicing saw recipe and process. The further improvement and solutions in eliminating the low- dicing saw peeling were also explored.     

Underdetermined Anechoic Blind Source Separation via $ell^{q}$-Basis-Pursuit With $q≪1$

In this paper, we address the problem of underdetermined blind source separation (BSS) of anechoic speech mixtures. We propose a demixing algorithm that exploits the sparsity of certain time-frequency expansions of speech signals. Our algorithm merges lscr^q -basis-pursuit with ideas based on the degenerate unmixing estimation technique (DUET) [Yiotalmaz and Rickard, "Blind Source Separation of Speech Mixtures via Time-Frequency Masking," IEEE Transactions on Signal Processing, vol. 52, no. 7, pp. 1830-1847, July 2004]. There are two main novel components to our approach: 1, our algorithm makes use of all available mixtures in the anechoic scenario where both attenuations and arrival delays between sensors are considered, without imposing any structure on the microphone positions, and 2, we illustrate experimentally that the separation performance is improved when one uses lscr^q-basis-pursuit with q < 1 compared to the q = 1 case. Moreover, we provide a probabilistic interpretation of the proposed algorithm that explains why a choice of 0.1 les q les 0.4 is appropriate in the case of speech. Experimental results on both simulated and real data demonstrate significant gains in separation performance when compared to other state-of-the-art BSS algorithms reported in the literature.     

InGaAs/GaAs 0.98- $mu{hbox {m}}$ Low-Divergence Central-Lobe Semiconductor Lasers With $delta$ -Doped Resonant Tunneling Quantum Wells

In this paper, we describe a new structure design for producing low-threshold, high-efficiency, and high-brightness 0.98-$mu{hbox {m}}$ lasers. In this structure, we incorporated a self-discriminating weak optical confinement asymmetrical waveguide coupled to passive waveguides, and an active region based on three InGaAs quantum wells (QWs) coupled to Te n-type $delta$-doping. Optimized coupling between the $delta$-doping and the three QWs, together with waveguide optimization and doping profile optimization, yields $J_{rm th}=98 {hbox {A/cm}}^{2}$ per QW, ${T}_{0}=80;^{circ}hbox{C}$, and a far-field central lobe angle of $sim 10^{circ}$.      

22.7-dB Gain $-$19.7-dBm $ICP_{1{rm dB}}$ UWB CMOS LNA

A fully differential CMOS ultrawideband low-noise amplifier (LNA) is presented. The LNA has been realized in a standard 90-nm CMOS technology and consists of a common-gate stage and two subsequent common-source stages. The common-gate input stage realizes a wideband input impedance matching to the source impedance of the receiver (i.e., the antenna), whereas the two subsequent common-source stages provide a wideband gain by exploiting RLC tanks. The measurements have exhibited a transducer gain of 22.7 dB at 5.2 GHz, a 4.9-GHz-wide B _3dB, an input reflection coefficient lower than -10.5 dB, and an input-referred 1-dB compression point of -19.7 dBm, which are in excellent agreement with the postlayout simulation results, confirming the approach validity and the design robustness.     

Spectroscopy and Lasing of Yb-Doped ${hbox {NaY}}{({hbox {WO}}_{4})}_{2}$: Tunable and Femtosecond Mode-Locked Laser Operation

Tetragonal (space group f4 macr) single crystals of NaY(WO₄)₂ doped with Yb to a density of 4.52 times 10²⁰ cm^-3 have been employed as laser active materials for the 1-mum spectral range, operating at room temperature. Using Ti:sapphire laser pumping, slope efficiencies as high as 74.6% were achieved without special cooling for the pi-polarization. The Yb-laser was continuously tunable from 1003.7 to 1073.0 nm with a birefringent filter. Pulses as short as 53 fs were obtained at 1035 nm by SESAM passive mode-locking with intracavity dispersion compensation and additional extracavity pulse compression using analogous prism pairs. Experimental data on the spectroscopic properties of Yb³⁺ in the 5-300 K temperature range and the room temperature optical properties of this novel Yb-host is also presented.     

High-Performance $hbox{In}_{0.7}hbox{Ga}_{0.3}hbox{As}$ -Channel MOSFETs With High-$kappa$ Gate Dielectrics and $alpha$-Si Passivation

Long and short buried-channel $hbox{In}_{0.7}hbox{Ga}_{0.3}hbox{As}$ MOSFETs with and without $alpha$-Si passivation are demonstrated. Devices with $alpha$-Si passivation show much higher transconductance and an effective peak mobility of 3810 $hbox{cm}^{2}/ hbox{V} cdot hbox{s}$. Short-channel MOSFETs with a gate length of 160 nm display a current of 825 $muhbox{A}/muhbox{m}$ at $V_{g} - V_{t} = hbox{1.6} hbox{V}$ and peak transconductance of 715 $muhbox{S}/muhbox{m}$. In addition, the virtual source velocity extracted from the short-channel devices is 1.4–1.7 times higher than that of Si MOSFETs. These results indicate that the high-performance $hbox{In}_{0.7}hbox{Ga}_{0.3} hbox{As}$-channel MOSFETs passivated by an $alpha$ -Si layer are promising candidates for advanced post-Si CMOS applications.      

High-Power Continuous-Wave Single-Longitudinal-Mode Operation of an Optically Pumped DFB Laser at $lambda sim 3.64~ mu$m

High-power continuous-wave (CW) single-longitudinal-mode emission at 3.64 mum is obtained from an optically pumped distributed-feedback (DFB) laser. The Bragg stopband and two degenerate DFB modes are observed at certain pump powers. The laser incorporates 14 InAs-InGaSb-InAs type-II quantum wells imbedded in an InGaAsSb waveguide. The index-coupled 1-D grating is fabricated in the top clad using interference lithography and plasma etching. A 110-mum-wide stripe from a 1.9-mum CW laser provides both optical pumping and gain guiding. Record high output power of more than 560 mW per side is obtained at 80 K. The wavelength is tunable over a 6.8-nm range by varying the pump power from 1 to 8.1 W.     

Effect of Si-nc to ${hbox {Er}}^{3+}$ Coupling Ratio in EDWAs Longitudinally Pumped by Visible Broad-Area Lasers

We present a finite element based model for Si-nc sensitized ${hbox {Er}}^{3+}$ doped waveguide amplifiers (EDWA), longitudinally pumped by a novel pumping scheme using broad-area visible lasers, which accurately describes the effect of the Si-nc to ${hbox {Er}}^{3+}$ coupling ratio on the amplifier performance.      

Scattering Analysis for Layered Cylindrical Object Perpendicularly Piercing the Wider Walls of a Rectangular Waveguide and Its Application to ${varepsilon _{r}}$ and ${mu _{r}}$ Measurement

This paper describes a novel analysis for the scattering problem of a layered cylindrical object that pierces a rectangular waveguide through a pair of holes made at the center of the wider walls. In this analysis, the $S$-parameters are rigorously formulated in terms of the modal scattering coefficients of the cylindrical object. Here, the modal scattering coefficients are expressed as solutions to a set of linear equations of infinite extent. The layered object is represented by the admittance function, which can readily be calculated for an arbitrary number of layers, using a recurrence formula. To show the applicability of the presented formulas, two types of dielectric samples (polytetrafluoroethylene and polyacetar) and a ferrite sample were measured, and reasonable values were obtained. In addition, the complex permittivity of water was determined by using a glass capillary tube as a liquid container, and an excellent agreement was shown with the value predicted by Debye's formula.      

Numerical Rate Equation Modeling of a ${sim {hbox {2.1}}-}mu{hbox {m}}-{rm Tm}^{3+}/{rm Ho}^{3+}$ Co-Doped Tellurite Fiber Laser

Judd–Ofelt analysis is performed on measurements of bulk samples of ${rm Tm}^{3+}$ - and ${rm Ho}^{3+}$ -doped tellurite glass from which the host-dependent Judd–Ofelt intensity parameters are extracted. These have then been used to calculate the radiative rates and branching ratios in this particular material system. A rate-equation approach is then used to model an experimentally realized ${sim {hbox {2.1}}},mu{hbox {m}},{rm Tm}^{3+}/{rm Ho}^{3+}$ codoped tellurite fiber laser and extract values of the energy transfer and upconversion rate parameters in ${rm TeO}_{2}-{rm ZnO}-{rm Na}_{2}{rm O}$ (TZN) glass. Excellent agreement is found between simulated and experimental data, which indicates the validity of the approach.      

Time-Resolved Linewidth Enhancement Factors in Quantum Dot and Higher-Dimensional Semiconductor Amplifiers Operating at 1.55 $mu{hbox{m}}$

We report time-resolved measurements of the linewidth enhancement factors (-factors) , and , associated with the adiabatic carrier recovery, carrier heating, and two-photon absorption dynamical processes, respectively, in semiconductor optical amplifiers (SOAs) with different degrees of dimensionality-one InAs/InGaAsP/InP quantum dot (0-D), one InAs/InAlGaAs/InP quantum dash (1-D), and a matching InGaAsP/InGaAsP/InP quantum well (2-D)-all operating near 1.55- wavelengths. We find the lowest values in the QD SOA, 2-10, compared to 8-16 in the QW, and values of and that are also lower than in the QW. In the QD SOA, the -factors exhibit little wavelength dependence over the gain bandwidth, promising for wide-bandwidth all-optical applications. We also find significant differences in the -factors of lasers with the same structure, due to the differences between gain changes that are induced optically or through the electrical bias. For the lasers we find the QW structure instead has the lower -factor, having implications for directly modulated laser applications.     

A Single-Chip UHF RFID Reader in 0.18 $mu{hbox {m}}$ CMOS Process

A single-chip UHF RFID reader that integrates all building blocks—including an RF transceiver, IQ data converters, and a digital baseband—is implemented in a 0.18 $mu{hbox {m}}$ CMOS process. A high-linearity RX front-end and a low-phase-noise synthesizer are proposed to handle the large self-interferer, which is a key challenge in the reader RX design. Highly reconfigurable mixed-signal baseband architecture for channel-selection filtering is proposed to achieve power optimization for multi-protocol operation with different system dynamic ranges and data rates. The reader dissipates a maximum power of 276.4 mW when transmitting maximum output power of 10.4 dBm and receiving the tag's response of $-$70 dBm in the presence of $-$5 dBm self-interferer while occupying 18.3 ${hbox {mm}}^{2}$.      

General Error Locator Polynomials for Binary Cyclic Codes With $t le 2$ and $n < 63$

In this paper, we show that a recently proposed algorithm for decoding cyclic codes may be applied efficiently to all binary cyclic codes with tles2 and n<63. This is accomplished by providing structure theorems for the codes in this range and classifying the relevant cases     

Eigendecomposition of Images Correlated on $S^{1}$, $S^{2}$, and $SO(3)$ Using Spectral Theory

Eigendecomposition represents one computationally efficient approach for dealing with object detection and pose estimation, as well as other vision-based problems, and has been applied to sets of correlated images for this purpose. The major drawback in using eigendecomposition is the off line computational expense incurred by computing the desired subspace. This off line expense increases drastically as the number of correlated images becomes large (which is the case when doing fully general 3-D pose estimation). Previous work has shown that for data correlated on S ¹ , Fourier analysis can help reduce the computational burden of this off line expense. This paper presents a method for extending this technique to data correlated on S ² as well as SO(3) by sampling the sphere appropriately. An algorithm is then developed for reducing the off line computational burden associated with computing the eigenspace by exploiting the spectral information of this spherical data set using spherical harmonics and Wigner-D functions. Experimental results are presented to compare the proposed algorithm to the true eigendecomposition, as well as assess the computational savings.