Optical regenerative oscillation and monostable pulse generation in electrooptic bistable devices

Optical regenerative oscillation is discussed theoretically and experimentally in three types of mirrorless bistable optical devices based on the electrooptic light modulator. The devices have two feedback signals proportional to the optical output power, and the oscillation condition and oscillation frequency depend on the time constants and conversion factors for two feedback voltages and biasing phase retardation in the light modulator. Analysis is done by treating the coupled differential equations for the time dependent feedback signals. The experimental results agree with the theoretical prediction. We show also that optical monostable pulses can be generated in the three types of bistable optical devices.     

Bifurcations in electrooptic bistable devices with short delay times in the feedback

We have investigated experimentally the behavior of a hybrid bistable electrooptic device with a delayed feedback when the delay time is comparable to the time constant of the device. The behavior is governed by a nonlinear difference-differential equation. The threshold of instability and the period of the oscillations observed close to threshold agree relatively well with the predictions obtained from a linear stability analysis of this equation. For larger input signals or feedback, bifurcations take place. We then observe period-2, period-4, and chaotic behavior following the period-doubling scheme of Feigenbaum. For delay times shorter than the time constant this bifurcation behavior can still be observed for large input signals. Furthermore, for such short delay times the threshold for onset of instabilities was observed to exhibit hysteresis, so different thresholds were observed when the input signal was increasing and decreasing.     

Measurements of the electrooptic effect in CdS, ZnTe, and GaAs at 10.6 microns

Low-frequency electrooptic coefficients have been measured for three semiconductors at 10.5 microns. The results arer_{c} = (5.5 pm 1) times 10^{-12}m/V for CdS,r_{41} = (1.4 pm 0.2) times 10^{-12}m/V for ZnTe, andr_{41} = (1.6 pm 0.1) times 10^{-12}m/V for GaAs. A comparison is made of the efficiencies of these materials in different modulator configurations. The effect of photoelectrically induced space charge is discussed briefly.     

Logic self-electrooptic effect devices: quantum-well optoelectronicmultiport logic gates, multiplexers, demultiplexers, and shift registers

Two-dimensional arrays of logic self-electrooptic effect devices (L-SEEDs), consisting of electrically connected quantum-well p-i-n diode detectors and modulators are demonstrated. The topology of the electrical connections between the detectors is equivalent to the connections between transistors in CMOS circuits. Three different L-SEED arrays were built and tested. Each element in one array can implement any of the four basic Boolean logic functions (i.e., NOR, NAND, AND, OR). Each element in the second L-SEED array can implement the function E=AB+CD. The third L-SEED array consists of 32×16 arrays of symmetric SEEDs (S-SEEDs) connected with optoelectronic transmission gates. Photonic switching nodes, multiplexers, demultiplexers, and shift registers have been demonstrated using this array     

Molecular electronics: from devices and interconnect to circuits and architecture

As the dominating CMOS technology is fast approaching a "brick wall," new opportunities arise for competing solutions. Nanoelectronics has achieved several breakthroughs lately and promises to overcome many of the limitations intrinsic to current semiconductor approaches. Most of the results in this area reported until now focus on devices and interconnect; this work goes several steps further and presents issues related to circuits and architecture. Based on proposed nanoscale interconnect and device structures, we explore the design space available to the nanoelectronic circuit designer and system architect.     

Field-effect transistor self-electrooptic effect device: integrated photodiode, quantum well modulator and transistor

The authors propose and demonstrate the integration of a photodiode, a quantum-confined Stark-effect quantum-well optical modulator, and a metal-semiconductor field-effect transistor (MESFET) to make a field-effect transistor self-electrooptic effect device. This integration allows optical inputs and outputs on the surface of a GaAs-integrated circuit chip, compatible with standard MESFET processing. To provide an illustration of feasibility, the authors demonstrate signal amplification with a single MESFET.<>     

The quantum well self-electrooptic effect device: Optoelectronic bistability and oscillation, and self-linearized modulation

We report extended experimental and theoretical results for the quantum well self-electrooptic effect devices. Four modes of operation are demonstrated: 1) optical bistability, 2) electrical bistability, 3) simultaneous optical and electronic self-oscillation, and 4) self-linearized modulation and optical level shifting. All of these can be observed at room-temperature with a CW laser diode as the light source. Bistability can be observed with 18 nW of incident power, or with 30 ns switching time at 1.6 mW with a reciprocal relation between switching power and speed. We also now report bistability with low electrical bias voltages (e.g., 2 V) using a constant current load. Negative resistance self-oscillation is observed with an inductive load; this imposes a self-modulation on the transmitted optical beam. With current bias, self-linearized modulation is obtained, with absorbed optical power linearly proportional to current. This is extended to demonstrate light-by-light modulation and incoherent-to-incoherent conversion using a separate photodiode. The nature of the optoelectronic feedback underlying the operation of the devices is discussed, and the physical mechanisms which give rise to the very low optical switching energy (∼4 fJ/ μm²) are discussed.     

Linear electrooptic effect in HgS (Cinnabar) at 0.63 and 3.39 microns

Nonlinear optical properties of HgS have been of interest lately. The electrooptic effect has been measured in a natural crystal and values for the two independent coefficients are reported here at wavelengths of 0.63 and 3.39 microns. The results agree well with predictions of purely electronic theories, but the wavelength dependence indicates an appreciable contribution of ionic motion to the optical polarizability.     

1 110 nm Nd:GGG 激光器与555 nm 倍频激光器

采用紧凑的直腔设计和精确的膜系设计, 实现了LD 侧面泵浦1 110 nm Nd:GGG 和腔内倍频的555 nm 激光.当泵浦功率为168 W时, 得到了25.5 W的1110 nm 连续激光输出.在10 kHz 的声光调Q 情况下, 应用II 类非临界相位匹配LiB3O5(LBO)倍频晶体, 得到了最大输出功率为3.1 W的555 nm 倍频光输出, 光-光转换效率为1.8 %, 相应的脉冲宽度为176 ns, 在水平和竖直方向上的M2因子分别为19.6 和21.3.     

Simulation of interconnect inductive impact in the presence of process variations in 90 nm and beyond

The on-chip inductive impact on signal integrity has been a problem for designs in deep-submicrometer technologies. The inductive impact increases the clock skew, max timing, and noise of bus signals. In this letter, circuit simulations using silicon-validated macromodels show that there is a significant inductive impact on the signal max timing (/spl sim/ 10% pushout versus RC delay) and noise (/spl sim/2/spl times/RC noise). In nanometer technologies, process variations have become a concern. Results show that device and interconnect process variations add /spl sim/ 3% to the RLC max-timing impact. However, their impact on the RLC signal noise is not appreciable. Finally, inductive impact in 65- and 45-nm technologies is investigated, which indicates that the inductance impact will not diminish as technology scales.     

Symmetric self-electrooptic effect device: optical set-reset latch,differential logic gate, and differential modulator/detector

The symmetric self-electrooptic-effect device (S-SEED), a structure consisting of two p-i-n diodes electrically connected in series and acting as an optically bistable set-reset latch, is discussed. Applications and extensions of this device are also discussed. The devices do not require the critical biasing that is common to most optically bistable devices and thus is more useful for system applications. They have been optically cascaded in a photonic ring counter and have been used to perform different NOR, OR, NAND, and AND logic functions. Using the same device, a differential modulator that generates a set of complementary output beams with a single voltage control lead and a differential detector that gives an output voltage dependent on the ratio of the two optical input powers have been demonstrated     

A transient Poole-Frenkel effect at the semiconductor surface of MAOS devices

The generation of the inversion layer in MOS and MAOS structures shows remarkable differences. Whereas for MOS samples free minority carriers build up the inversion layer, the positive layer in n-type silicon MAOS devices is mainly caused by a trap charging process. This trap charging shows peculiar properties. After a voltage step which depletes the semiconductor surface from majority carriers the gate current has a maximum at a time of about 10⁻⁴s after the step. This current which is proved to be related to the increase of the trap charge is strongly temperature and field dependent. It is shown that the time dependent maximum in the current is caused by a transient Poole-Frenkel effect at the semiconductor surface.     

Electroabsorption and electrooptic effect in SiGe-Si quantum wells:realization of low-voltage optical modulators

We have calculated the behavior of the band-to-band absorption coefficient in square, coupled, and graded bandgap Si_0.6Ge _0.4-Si quantum wells as a function of the transverse electric field. It is seen that due to the weak confinement of the electrons (ΔE_c⩽20 meV) the absorption of photons with energy equal to the interband transition energy can be reduced at very small values of the transverse electric field. This phenomenon lends itself to the design of efficient amplitude modulators. In addition, the resulting change in the refractive index is also large and the corresponding linear electrooptic coefficient is calculated to be as large as 1.9×10^-10 m/V in square wells. This effect could prove to be the basis for the realization of efficient Si-based electrooptic modulators. Device designs are discussed     

Multi-gate devices for the 32 nm technology node and beyond

Due to the limited control of the short channel effects, the high junction leakage caused by band-to-band tunneling and the dramatically increased V_T statistical fluctuations, the scaling of planar bulk MOSFETs becomes more and more problematic with every technology node. The ITRS roadmap predicts that from the 32 nm technology node on, planar bulk devices will not be able to meet the stringent leakage requirements anymore and that multi-gate devices will be required. In this paper, the suitability of FinFET-based multi-gate devices for the 32 nm technology and beyond will be discussed. Apart from the benefits, some technological challenges will be addressed.     

Study of the photosensitivity at 193 nm and comparison withphotosensitivity at 240 nm influence of fiber tension: type IIa aging

The photosensitivity in germanosilicate fibers at 193 nm is studied and compared with that at 240 nm. As previously shown, it is found that, without hydrogen sensitization, the initiation of the phenomenon is a one-photon process for a high germanium content fiber and a two-photon process for a low germanium content fiber. However, when the low germanium content fiber is previously loaded with hydrogen, it is observed that the photo-induced index change initial growth rate varies linearly with the fluence, invoking a one-photon process. It is shown that external strains applied to the fiber strongly influence the mechanisms of the photosensitivity at 193 nm. Finally, an aging study is carried out     

Growth and decay of the electrooptic effect in thermally poled B/Gecodoped fiber

Using an in situ technique for measuring the induced electrooptic effect during poling, we have studied the growth and decay characteristics of thermally poled twin hole B/Ge codoped fiber devices. The decay characteristic measured at elevated temperatures were best fitted with a stretched exponential function, indicating a distribution of relaxation times is present in this material. Using the Arrhenius relation, we calculate an activation energy for the stability of the electrooptic effect with this material and poling geometry in the range from 25 to 28 kJ/mol (0.28-0.31 eV), corresponding to a lifetime at 298 K of approximately 45 days     

The stability analysis and the modulation effect on a Braggacoustooptic bistable system

Modulation effects on an acoustooptic hybrid bistable system that is based on Bragg-type diffraction are analyzed. The dynamic and stationary equations describing the system are derived, and the parameters for bistability are given. The boundary for instability is drawn in an output intensity and a delay-time phase plane. When the input intensity undergoes a sinusoidal modulation, the appearance of frequency locking, period doubling bifurcation to chaos, and resonance phenomena in this system is predicted     

Texture and strain in narrow copper damascene interconnect lines: An X-ray diffraction analysis

The behaviour of submicron damascene copper lines raises a number of fundamental issues such as grain growth in narrow trenches, thermomechanical properties of copper in these confined geometries, etc. This experimental study is aimed at evaluating the influence of annealing, polishing and line width on the room temperature strain and texture of narrow copper damascene lines. X-ray diffraction has been performed on arrays of lines with widths ranging between 3 μm and 0.09 μm. Two annealing conditions (150 °C and 400 °C) have been used either prior or after Chemical Mechanical Polishing (CMP). A clear influence of the Cu overburden on the in-line microstructure is evidenced. X-ray diffraction analysis shows that strains in line longitudinal direction are higher in those annealed at 400 °C and decrease with the width of the lines.Effect of CMP on structure and relationship between both texture and strain and temperature of thermal treatments is discussed in light of these observations.     

铜互连制程中酸碱性抛光液的平坦化效果评估

We observed and analyzed the acid and HEBUT alkaline of Cu chemical mechanical polishing(CMP)slurry to evaluate their effects. Material analysis has shown that the planarity surfaces and the removal rate of alkaline slurry are better than the acid slurry during metal CMP processes. The global surface roughness and the small-scale surface roughness by 1010 m2 of copper film polished by the SVTC slurry are 1.127 nm and2.49 nm. However, it is found that the surface roughnesses of copper films polished by the HEBUT slurry are 0.728 nm and 0.215 nm. All other things being equal, the remaining step heights of copper films polished by the SVTC slurry and HEBUT slurry are respectively 150 nm and 50 nm. At the end of the polishing process, the dishing heights of the HEBUT slurry and the SVTC slurry are approximately both 30 nm, the erosion heights of the HEBUT slurry and the SVTC slurry are approximately both 20 nm. The surface states of the copper film after CMP are tested,and the AFM results of two samples are obviously seen. The surface polished by SVTC slurry shows many spikes.This indicates that the HEBUT alkaline slurry is promising for inter-level dielectric(ILD) applications in ultra large-scale integrated circuits(ULSI) technology.