Ytterbium-Doped P$_2$O$_5$-TeO $_2$ Glass for Laser Applications

Ytterbium-doped sodium phospho-tellurite glasses are made with different P₂O₅:TeO₂ ratio, and Yb³⁺ concentrations. Physical properties of the new Yb hosts are favorable for laser applications. The glasses show high absorption and emission cross sections and higher lifetime of Yb³⁺:²F_5/2rarr²F_7/2 transition. The emission cross sections are calculated using two different methods and compared. The laser parameters of these Yb³⁺ -doped glasses are better than many reported glasses and crystals making them potential to fabricate high power laser and broadband optical amplifier in the wavelength region around ~1 mum     

Low Half-Wave Voltage X-Cut Thin LiNbO $_{3}$ Sheet Optical Phase Modulator With Asymmetric Coplanar Waveguide Electrode

We present a novel X-cut lithium niobate optical phase modulator. Low driving voltage was realized by adopting both an X-cut thin LN sheet structure and an asymmetric coplanar waveguide electrode. A low half-wave voltage of 2.9 V in 20-GHz operation was obtained.      

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     

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.     

Reliability Bounds for Multi-State $k$-out-of- $n$ Systems

Algorithms have been available for exact performance evaluation of multi-state k-out-of-n systems. However, especially for complex systems with a large number of components, and a large number of possible states, obtaining "reliability bounds" would be an interesting, significant issue. Reliability bounds will give us a range of the system reliability in a much shorter computation time, which allow us to make decisions more efficiently. The systems under consideration are multi-state k-out-of-n systems with i.i.d. components. We will focus on the probability of the system in states below a certain state d, denoted by Q_sd. Based on the recursive algorithm proposed by Zuo & Tian [14] for performance evaluation of multi-state k-out-of-n systems with i.i.d. components, a reliability bounding approach is developed in this paper. The upper, and lower bounds of Q_sd are calculated by reducing the length of the k vector when using the recursive algorithm. Using the bounding approach, we can obtain a good estimate of the exact Q_sd value while significantly reducing the computation time. This approach is attractive, especially to complex systems with a large number of components, and a large number of possible states. A numerical example is used to illustrate the significance of the proposed bounding approach.     

Lifetime of Combined $k$-out-of-$n$ , and Consecutive $k_{c}$ -out-of-$n$ Systems

A combined k-out-of-n:F(G) & consecutive k_c -out-of-n :F(G) system fails (functions) iff at least k components fail (function), or at least fcc consecutive components fail (function). Explicit formulas are given for the lifetime distribution of these combined systems whenever the lifetimes of components are exchangeable, and have an absolutely continuous joint distribution. The lifetime distributions of the aforementioned systems are represented as a linear combination of distributions of order statistics by using the concept of Samaniego's signature. Formulas for the mean lifetimes are given. Some numerical results are also presented.     

Optimal $ Sigma Delta$ Modulator Architectures for Fractional-$ {N}$ Frequency Synthesis

This paper presents a comparative study of $Sigma Delta$ modulators for use in fractional-$ {N}$ phase-locked loops. It proposes favorable modulator architectures while taking into consideration not only the quantization noise of the modulator but also other loop nonidealities such as the charge pump current mismatch that contributes to the degradation in the synthesized tone's phase noise. The proper choice of the modulator architecture is found to be dependent upon the extent of the nonideality, reference frequency, and loop bandwidth. Three modulator architectures are then proposed for low, medium, and high levels of nonidealities.      

Two-Way Handshaking Circular Sequential $k$-Out-of- $n$ Congestion System

Many communication systems require a two-way, or three-way handshaking process to improve their dependability & authenticity in order to achieve a more successful operation. In this paper, we present a new two-way handshaking reliability model based upon threshold-based cryptography systems. Such systems require a two-way handshaking process to i) establish a group of participated servers in the first handshaking process, and ii) calculate a cipher with successfully connected servers collaboratively in the second handshaking process. When the servers are attempted, each server has three known connection probabilities in the following three states: i) successful, ii) breakdown, and iii) congested. These connection probabilities are unchanged in both handshaking processes. During the first handshaking process, we establish connections that more than servers are willing to participate. For the second handshaking process, the system becomes successful as soon as we can connect these servers successfully again. Because we need to connect servers successfully in the second handshaking process, we would rather connect additional servers besides the servers required to be connected successfully in the first handshaking process. This preference will minimize the chance that the system breaks down when fewer than servers can be reconnected successfully in the second handshaking process. We refer to this system as a Two-Way Handshaking Circular Sequential-out-of-Congestion (TWHCSknC) system. In this paper, we derived analytical formulas for the system's successful probability & average stop length, and we showed that the TWHCSknC system is a communication system with an efficient two-way handshaking process.     

High-Quality Grouped-Wavelength Conversion and Dynamic Switching Using Multiple-QPM LiNbO $_{3}$ and TLA

We demonstrate dynamic grouped-wavelength conversion using multiple quasi-phase-matched LiNbO$_{3}$ modules and a tunable laser diode array. A high signal-to-noise ratio of larger than 45 dB is obtained for the converted signals. The power penalty of the wavelength converter is confirmed to be less than 0.2 dB.      

Highly Integrated Optical 4 $,times,$4 Crossbar in Silicon-on-Insulator Technology

In this paper, we present the design, fabrication, and characterization of a highly integrated optical 4$,times,$ 4 crossbar based on microring resonator add-drop filters. The designed crossbar structure, as small as $50,mu{hbox {m}}times50,mu{hbox {m}}$, has been fabricated in CMOS compatible silicon on insulator technology. Finally, experimental results proving the proper operation of the fabricated crossbar structures are discussed.      

Multiwavelength $Q$-switched Laser by Incorporating a LiNbO$_{3}$ Phase Modulator in Fabry–PÉrot Cavity

In this letter, we present a simple and compact laser cavity that can be used for $Q$-switching and multiwavelength oscillation. It is shown that a LiNbO $_{3}$ phase modulator with relatively low driven voltage inserted into a Fabry–PÉrot cavity can act simultaneously as an effective component for suppressing the homogeneous line broadening, switching the $Q$ -value of the laser cavity, and a polarizer. Multiwavelength operation of Yb-doped fiber laser is achieved by phase modulation. $Q$-switching is achieved due to the residual intensity modulation of the phase modulator, and the pulse performance is also impacted by the phase modulation amplitude. Three stable wavelengths with identical wavelength spacing of 3.3 nm and pulsed laser of 0.2 $mu$J per pulse energy at the repetition rate of 55.8 kHz are demonstrated. The full-width at half-maximum pulse duration is of 2 $mu$s, and the polarization extinction ratio is $>$23 dB.      

A Fully Differential Comparator-Based Switched-Capacitor $DeltaSigma$ Modulator

In this brief, a fully differential comparator-based switched-capacitor (CBSC) second-order delta-sigma $(DeltaSigma)$ modulator is presented. To ensure differential operation, the CBSC $DeltaSigma$ modulator utilizes a common-mode feedback circuit to balance the pull-up current and the pull-down current in the ramp generator. This modulator has been fabricated in a standard 0.18-$muhbox{m}$ CMOS process. The active area is 0.21 $hbox{mm}^{2}$, and the power consumption, excluding output buffers, is 0.42 mW from a 1.8-V supply. This modulator achieves 65.3-dB signal-to-noise-plus-distortion ratio and an input dynamic range of 71 dB when sampled at 2.56 MS/s $(hbox{OSR} = 64)$.      

Design Considerations for Cascade $Delta Sigma $ ADC's

This brief discusses the design tradeoffs for cascaded delta-sigma (DeltaSigma) analog-to-digital converters. Increasing the order of the first loop allows a tradeoff between aggressive noise shaping and moderate operational transconductance amplifier (OTA) specifications. A comparison between fourth-order topologies indicates that for a cascade 3-1 topology, 55-dB OTA gain is sufficient for 96-dB signal-to-noise-distortion ratio while 5% coefficient mismatch results in less than 4-dB degradation. Dependent on the ratio between the power consumption of the digital recombination and decimation filter and that of the analog loop filter, the optimal topology can be chosen. A cascade 3-1 converter is most efficient when this ratio lies between 0.54 and 0.97. A design in a 65-nm CMOS technology demonstrates the performance of a cascade 3-1 converter.     

Matrix Methods for the Dynamic Range Optimization of Continuous-Time $G_{m}$- $C$ Filters

This paper presents a synthesis procedure for the optimization of the dynamic range of continuous-time fully differential $G_{m}$-$C$ filters. Such procedure builds up on a general extended state-space system representation which provides simple matrix algebra mechanisms to evaluate the noise and distortion performances of filters, as well as, the effect of amplitude and impedance scaling operations. Using these methods, an analytical technique for the dynamic range optimization of weakly nonlinear $G_{m}$- $C$ filters under power dissipation constraints is presented. The procedure is first explained for general filter structures and then illustrated with a simple biquadratic section.      

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.     

Compact Bends for Achieving Higher Integration Densities for LiNbO$_{3}$ Waveguides

A new waveguide platform is demonstrated that allows the bend radii to be substantially decreased for titanium-diffused lithium-niobate (LiNbO₃) waveguides using vertically integrated arsenic-trisulfide (As₂S₃) overlay waveguides. Power is transferred from a Ti-diffused waveguide into the overlay waveguide using tapers, guided by the As₂S₃ waveguide through the S-bend region and transferred back into another Ti-diffused waveguide. This structure also behaves like a polarization beam splitter. We present simulation results as well as measurements to show the feasibility of achieving low loss and reduced bend radii for electrooptic waveguides.     

Fabrication and Characterization of Coplanar Waveguides on Silicon Using a Combination of SiO $_{2}$ and SRO $_{20}$

In this work, the use of silicon rich oxide (SRO) and chemical vapor deposition SiO$_{2}$ double layers as passivation films of coplanar waveguides (CPW) on high resistivity silicon (HR-Si) with an ${hbox{N}}^{+}$ backside is studied. The microwave performance of the fabricated CPWs is evaluated by computing the attenuation loss of the devices in the 0.045–50 GHz frequency range. Experimental results show that the ${hbox{N}}^{+}$ layer can be used without affecting CPW performance. Also, using a combined dielectric layer (SRO$_{20}$ /SiO$_{2}$ ), the attenuation losses are reduced compared to single dielectric layers.      

A 200-$mu$V/e$^{-}$ CMOS Image Sensor With 100-ke$^{-}$ Full Well Capacity

A high-sensitivity CMOS image sensor keeping a high full-well capacity has been developed by introducing a new pixel having a small floating diffusion (FD) capacitance connected to a lateral overflow integration capacitor (LOFIC) through a MOS switch. The conceptual advantage of the small FD approach over conventional column amplifier approaches is compared and demonstrated. To ensure both the high sensitivity and the high full-well capacity, the low-light and the bright-light signals (S1 and S2) are output and reproduced without a visible SNR degradation at the S1/S2 switching point. As the most critical problem, the increase of the conversion gain variation in this approach is suppressed by applying a self-aligned offset structure to the small FD. A 1/4-in VGA format CMOS image sensor fabricated through 0.18-mum 2P3M process achieves 2.2-e^- rms noise floor with 200-muV/e^- conversion gain and 100-ke^- full-well capacity.     

Experimental Demonstration of Deeply-Etched SiO$_{2}$ Ridge Optical Waveguides and Devices

Deeply-etched ${hbox{SiO}}_{2}$ optical ridge waveguides are fabricated and characterized. A detailed discussion of the fabrication process (especially for the deep etching process) is presented. The measured propagation losses for the fabricated waveguides with different core widths range from $0.33sim {hbox {0.81}}~{hbox {dB}}/{hbox {mm}}$. The loss is mainly caused by the scattering due to the sidewall roughness. The losses in bending sections are also characterized, which show the possibility of realizing a small bending radius (several tens of microns). 1 $,times {rm N}$ ( ${rm N}=2$, 4, 8) multimode interference couplers based on the deeply-etched ${hbox{SiO}}_{2}$ ridge waveguide are also fabricated and show fairly good performances.