High-speed electroabsorption modulators buried with ruthenium-doped SI-InP

InGaAlAs-InAlAs electroabsorption modulators are successfully fabricated using ruthenium (Ru)-doped semi-insulating (SI)-InP burying technology. A comparison of measured and calculated microwave characteristics reveals that there is no additional microwave loss because zinc diffusion is inhibited by the use of Ru-doped SI-InP layers. A small-signal electrooptical response with a -3-dB electrical bandwidth of over 50 GHz is demonstrated.     

Gain saturation dependence on signal wavelength in a travelling-wave semiconductor laser amplifier

Gain saturation dependence on signal wavelength in a 1.5 ?m InGaAsP travelling-wave semiconductor laser amplifier is experimentally studied. Saturation output powers were 6.9dBm, 8.3dBm and 10.6dBm for signal wavelengths of 1490 nm, 1510 nm and 1540 nm, respectively. This saturation dependence on wavelength, i.e. higher saturation output power for longer signal wavelength, results from signal gain peak shift towards longer wavelength with increasing input power.     

Specific Heat Anomaly in Solid 3He due to Vacancy Waves

We observed the excess specific heat (anomaly) other than nuclear origins above 10 mK in bcc solid ³ He of 24.21 cm ³/mole. We checked whether it arises from spin polarons due to vacancies out of equilibrium by applying a strong magnetic field, in which vacancies should diffuse and vanish due to high polarization. The specific heat is the same before and after applying a magnetic field of 10 T. This fact indicates that vacancies did not vanish even in a strong field or the anomaly arises from the origin different from vacancies.     

Chemical vapor deposition of SiO2 films by TEOS/O2 supermagnetron plasma

A TEOS/O₂ supermagnetron double electrode plasma system was used to deposit SiO₂ films. Deposition rates were measured as a function of rf power and substrate stage temperature. With an increase of rf power on both electrodes from 40 to 80W, the deposition rate increased; however, with a further increase of rf power from 80 to 120W, the deposition rate ceased to increase or decreased only a small amount. The presence of O-H bonds from bonded water in the film was evaluated using buffered HF (BHF) etching solution. With an increase of rf power from 40 to 120W, the BHF etch rate decreased; i.e., the number of O-H bonds were reduced. A minimum BHF etch rate was observed at a rf phase difference of 180° between the two rf power sources. A SiO₂ film was deposited on a trench-patterned quartz substrate. A flat surface SiO₂ layer with air gaps (voids) was formed on the high-aspect ratio (depth/width=1.5-2) trench area.     

A novel design for dispersion compensating photonic crystal fiber Raman amplifier

This letter presents a novel design for dispersion compensating photonic crystal fiber (DCPCF) which shows inherently flattened high Raman gain of 19 dB (/spl plusmn/1.2-dB gain ripple) over 30-nm bandwidth. The proposed design module has been simulated through an efficient full-vectorial finite element method. The designed DCPCF has a high negative dispersion coefficient (-200 to -250 ps/nm/km) over C-band wavelength (1530-1568 nm). The proposed fiber module of 5.2-km length not only compensates the accumulated dispersion in conventional single-mode fiber (SMF-28) but also compensates for the dispersion slope. Hence, the designed DCPCF module acts as the gain-flattened Raman amplifier and dispersion compensator.     

Modeling of two-dimensional photonic crystal resonant cavities incorporating elliptically shaped dielectric cylinders

Modeling of photonic crystal structures is an ongoing challenge. This letter is devoted to the theoretical modeling of photonic crystal resonant cavities, composed of elliptically shaped dielectric pillars. Through this rigorous study, we can examine the impact of the elliptical-shape deformations to important quantities related to the photonic crystal cavity performance, such as the quality factor and the resonance frequency.     

Single-polarization single-mode photonic crystal fibers

A new structure of single-polarization single-mode (SPSM) photonic crystal fiber (PCF) is proposed and analyzed by using a full-vector finite element method with anisotropic perfectly matched layers. From the numerical results it is confirmed that the proposed fiber is low-loss SPSM-PCF within the wavelengths ranging from 1.48 to 1.6 /spl mu/m, where only the slow-axis mode exists and the confinement loss is less than 0.1 dB/km.     

Generalized concatenated codes for channels where unidirectionalbyte errors are predominant

Codes are considered for correction and detection of unidirectional byte errors. A code construction based on the generalized concatenated code construction is proposed. This construction gives a large number of efficient codes. For example, from this construction, a 72-input-bit encoder of the triple unidirectional 8-bit-byte error-correcting and fourfold unidirectional 8-bit-byte error-detecting code with a length of 112 bits and rate 9/14 is obtained, whereas the ordinary triple 8-bit-byte error-correcting and fourfold 8-bit-byte error-detecting code of the same length has only 56 information bits and is of rate 1/2. The proposed construction is generalized to one that gives efficient short-length codes     

Diagnosis of childhood BK virus cystitis by electron microscopy and PCR

A case of BK virus cystitis in a 5 year old boy is reported. This patient, who was not immunocompromised, had had acute cystitis for two weeks. Many intracytoplasmic inclusions were observed in urinary sediment smears stained by the Papanicolaou method. Electron microscopic examination showed virus particles, presumed to be human polyomavirus, in the nuclei of the degenerated urothelial cells. A DNA sequence of the BK virus was detected in 200-300 urothelial cells in Papanicolaou stained smears by the polymerase chain reaction. BK virus is an unusual cause of symptomatic cystitis in a healthy child.     

Recoveries of post-tetanic twitch and train-of-four responses after administration of vecuronium with different inhalation anaesthetics and neuroleptanaesthesia

We have studied recovery of post-tetanic twitch (PTT) and train-of-four (TOF) responses after administration of vecuronium in 100 patients under different inhalation anaesthetics and neuroleptanaesthesia. Patients were allocated randomly to five groups of 20 patients each to receive: neuroleptanaesthesia (droperidol and fentanyl), halothane, isoflurane, enflurane or sevoflurane (1 MAC in nitrous oxide and oxygen). The times from initial administration of vecuronium 0.2 mg kg-1 to the first appearances of T1, T2, T3 and T4 differed significantly between groups. However, the intervals to the first appearance of PTT1, PTT10 and PTT20 did not differ significantly between groups.