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Formation and Stabilization of a Decanuclear Cu(II) Wheel Linked by Chloride and O…H-N Hydrogen Bonds
No full text[[abstract]]The reaction of Ru-3(CO)(12) with three equivalent of 3,5-bis(trifluoromethyl) pyrazole [(3,5-(CF3)(2)-pz)H] at 180degreesC produces the double pyrazolate-bridged ruthenium complex [Ru(CO)(3)(3,5-(CF3)(2)-pz)](2), (1), in high yield. Ibis ruthenium complex has been characterized by spectroscopic methods, revealing a molecular structure similar to that of the diosmium analogue [OS(CO)(3)(3,5-(CF3)(2)-pz)](2). Thermogravimetric analysis (TGA) of complex 1 showed an enhanced volatility compared to the parent carbonyl compound Ru-3(CO)(12) and the closely related, unsaturated 3,5-di-tert-butyl pyrazole complex (2) [Ru-2(CO)5(3,5-t-Bu-2-pz)(2)]. Using complex 1 as the CVD source reagent, ruthenium metal with a preferred (002) orientation can be deposited at 400 degreesC using H-2 as the carrier gas. If, however, O-2 is used as the carrier gas, RuO2 thin films with a (101) orientation are obtained. The as-deposited metal thin films were characterized by various surface techniques, as well as by electrical resistivity measurements.[[fileno]]2010311010069[[department]]化學
A Thermal Phase-Locked Loop for Frequency Stabilization of Internal-Mirror He-Ne Lasers ( = 0.633m)
No full text[[abstract]]A new servo circuit based on the thermal phase-locked loop (TPLL) has been developed for frequency stabilization of internal-mirror He-Ne laser. A feedback signal proportional to the fluctuation in the frequency of the laser is down-converted through a voltage-controlled oscillator (VCO) and compared in a phase/frequency circuit with that of a frequency reference. The detected phase difference then drives a heater wrapped around the laser tube for tuning the laser cavity length. The frequency stability achieved is +/- 1.0 x 10(-9) over a period of several hours[[fileno]]2010144010025[[department]]物理
A Laser-Diode-Based Photoconductive Harmonic Mixer for Microwave waveform and Spectrum Measurement
No full text[[abstract]]Microwave waveform and spectrum measurement via a low frequency replica using a laser-diode-based photoconductive harmonic mixer is demonstrated. Waveforms of optoelectronically phase-locked 12.01-GHz microwave signals as well as waveform and spectrum of picosecond electrical pulses generated by a step recovery diode measured by this technique are presented. In comparison with previous experiments using main-frame lasers, the principal advantages of the present system are compactness, a large number of sampling points, and the ability to display the waveform and spectrum on any convenient time scale or frequency range[[fileno]]2010144010045[[department]]物理
Broadly tunable self-starting passively mode-locked Ti:sapphire laser with triple strained-quantum-Well saturable Bragg Reflector
No full text[[abstract]]We demonstrate broadband mode-locking of femtosecond Ti:sapphire lasers with a new type of saturable Bragg reflector (SBR). Triple-strained quantum wells with separate and sequential bandgaps were used as the absorbing layer. The saturation fluence was as low as 7 mu J/cm(2). Self-starting sub-100 fs pulses tunable from 768 to 804 nm were generated in a standard X-folded cavity without intracavity tight focusing on the SBR or temperature tuning. The threshold fluence for self-starting mode-locking was 1 mu J/cm(2)[[fileno]]2010144010082[[department]]物理
Efficient terahertz radiation generation from a bulk InAs mirror as an intracavity terahertz radiation emitter
No full text[[abstract]]Terahertz (THz) radiation is generated efficiently from a bulk InAs mirror with a shallow incidence angle inside the cavity of a femtosecond, mode-locked Ti:sapphire laser self-started by a strained saturable Bragg reflector A magnetic field is also applied to the InAs mirror to enhance THz radiation[[fileno]]2010144010089[[department]]物理
Generation of Femtosecond Laser Pulses Tunable from 380 nm to 465 nm via Cascaded Nonlinear Optical Mixing in a Noncollinear Optical Parametric Amplifier with a Type-I Phase Matched BBO Crystal
Get PDF[[abstract]]We report the generation of tunable femtosecond pulses from 380nm to 465nm near the degenerate point of a 405-nm pumped type-I BBO noncollinearly phase-matched optical parametric amplifier (NOPA). The tunable UV/blue radiation is obtained from sum frequency generation (SFG) between the OPA output and the residual fundamental beam at 810-nm and cascaded second harmonic generation (SHG) of OPA. With a fixed seeding angle, the generated SFG and SHG covers from 385 nm to 465-nm. With a pumping energy of 75 muJ at 405 nm, the optical conversion efficiency from the pump to the tunable SFG is more than 5% and the efficiency of SHG of the OPA is about 2%[[fileno]]2010144010100[[department]]物理
Formation of the Transverse Modes with Y-Junction Structures in Broad-Area Oxide-Confined Vertical-Cavity Surface-Emitting Laser
No full text[[abstract]]We performed experimental and theoretical investigations on the transverse-mode emission behavior of a broad-area oxide-confined vertical-cavity surface-emitting laser (VCSEL). The far-field emission pattern with y-junction structures is observed in the VCSEL with a 20-mum-diameter aperture when the injection current is significantly above the thermal roll-over point. In order to provide a quantitative understanding of these emission characteristics, we present a numerical simulation to model and fit the experimental results. The numerical simulation adopts the high-order Laguerre-Gaussian mode due to the assumptions of a parabolic refractive-index profile and ring-shaped carrier distribution in the laser. From the numerical simulation results, the formation of y-junction structures is inferred to be caused by the superposition of two high-order Laguerre-Gaussian modes. The results of this numerical simulation are in good agreement with the experimental findings[[fileno]]2010144010101[[department]]物理
Ultrabroadband terahertz field detection by photoconductive antennas based on multi-energy arsenic-ion-implanted GaAs and semi-insulating GaAs
No full text[[abstract]]The photoconductive antennas based on multi-energy arsenic-ion-implanted GaAs and semi-insulating GaAs are demonstrated to have a useful bandwidth beyond 20 THz for a gating laser pulse width of 15 fs. The bandwidth and signal-to-noise ratio are compared with those of reference photoconductive antennas based on low-temperature grown GaAs[[fileno]]2010144010102[[department]]物理
Room Temperature Electrically Controlled Terahertz Phase Shifter
No full text[[abstract]]We present the use of electrically controlled bire-fringence in a nematic liquid crystal cell for phase shifting of electromagnetic waves up to terahertz frequencies. This device. was operated at room temperature and a maximum phase shift of 4.07degrees was demonstrated at 1.07 THz when the interaction length was 38.6 mum. The driving voltage and corresponding field were 176.8 V (rms) and 589.3 V/cm, respectively[[fileno]]2010144010107[[department]]物理