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Ablations of Cr film on fused silica with ultrashort double pulses were investigated. Periodic microripple structures were formed on the Cr film after irradiating by trains of double laser pulses. Experimental results should be helpful for us to understand the electron phonon relaxation time for femtosecond laser micromachining.
The theoretical and experimental studies on the observation of adjustable multiple sub-Doppler traps in the six-beam magneto-optical trap (MOT) with unequal laser detunings are presented. When the detuning of the longitudinal lasers along the magnetic field axis is different from that of the transverse lasers, we obtain an array of three sub-Doppler traps; one usual but suppressed trap at the origin...
We report on temperature dependence of the radial breathing mode(RBM) frequency and its decay time in single walled carbon nanotubes (SWCNTs), which were studied by the femtosecond pump and probe technique. With increasing temperature, we found out that the RBM frequency and phonon decay time shows on abnormal dramatic change around 70degC for a certain type of carbon nanotubes, which may be originated...
A novel method (pulse-on-background) to reduce pulse distortion in fast light pulse propagation through an erbium-doped fiber amplifier by adding a background of appropriate power is suggested. The pulse-on-background method depends on pulse width, pump power, pulse power and background-to-pulse power ratio.
We demonstrate the coherent control of an excited atom in photonic crystals, in which its relaxation is strongly suppressed compared with that in the control using the photonic bandgap (PBG) switching. This suggests the possibility of extending the atomic system to a low-loss quantum logic gate for quantum information processing.
We propose a simple and new method which is able to characterize internal device parameters such as the internal quantum efficiency, nonradiative recombination rate, radiative recombination rate, and the internal carrier density in a light emitting diode. The method utilizes measurements of both the power versus current curve and the carrier lifetime.
An oxide-confined holey light-emitting diode (LED) on p-type GaAs substrate in the 830 nm range is reported. The device is consisted of bottom DBR, quantum wells, and top DBR, with a holey structure for light extraction. The internally reflected spontaneous emission can be extracted out of the etched hole.
A frequency-doubled pulsed dye laser at a 10 kHz-repetition-rate has been developed by elliptically focusing a dye laser at 580 nm onto a BBO type-I crystal. We report on the conversion efficiency and beam quality of the frequency-doubled pulsed dye laser in this paper.
The accuracy of a three-dimensional horizontally wide-angle beam-propagation method is assessed in detail through the analysis of a tilted step-index waveguide. Special attention is paid to the case where a waveguide is tilted to the vertical direction.
The radiation loss of a grating-outcoupled surface-emitting laser at transitions is analyzed. We simulate the forward and backward radiated power at interfaces of a ridge, a transition and a grating region. A total of 11.32% (0.52 dB) of the power is radiated at transitions.
The efficiency of drug release from polymeric nanoparticles was observed using real-time fluorescence microscopy. The movements of polymeric nanoparicles were controlled by magnetic force as fluorescence imaging of doxorubicin was performed during a 5-day period. This result may be applied to investigations of novel cancer therapy in future.
Optical measurement techniques were continuously applied for glucose sensing for several years. Optical polarimetry is an effect method for the measurement of glucose concentration. In this paper, we introduce a new optical polarimetry probe system which has a variable optical path length.
Combination of intra-cavity SHG and passively-Q-switching demonstrated on 473 nm quasi-four-level Nd:YAG laser. Periodically-poled MgO:SLT was inserted into the 10 mm length cavity of passively-Q-switched Cr:Nd:YAG laser. A longitudinally pumping with 4 W laser diode shows beam quality of M2 ap1. The output energy of 29 muJ and pulse duration of 3.1 ns were obtained.
We measured the diffraction efficiency in porphyrin:Zn doped nematic liquid crystals by using a two beam coupling experiment under the influence of an applied dc field. The maximum diffraction efficiency of eta = 38.7% was obtained with a writing beam intensity of 207 mW/cm2 and an electric field of 1.28 V / mum.
We propose a pre-optical system for a stellar coronagraph to reduce the speckle noise. It consists of an (amplitude-) unbalanced nulling interferometer (UNI) and phase and amplitude correction (PAC) with two deformable mirrors. We have demonstrated that an initial wavefront error of lambda/82 is 3.9 times magnified to lambda/22 by the UNI.
A new contacting probe is presented to measure the topography of samples in micro/nano scale. The displacement of the probe is monitored by a photodetector, which receives a diffracted beam from the probe. Analysis results of the probe, which are based on the scalar diffraction theory, are discussed.
A new method for real-time and simultaneous measuring the refractive index and thickness of thin films is proposed. The method is based on spectral dependence of phase-shifting on reflection at one of film's surface. The measurement consists in localizing pi-phase shift observed in a channel spectrum.
We have successfully measured a space distance with the accuracy of less than 10-5 based on TPA process in a silicon photodetector. The two signal processing technologies including the Fourier transform method and the curve fitting method were investigated.
Practical all fiber three dimensional measurement system is demonstrated. The sensitivity and axial resolution are as high as 85 dB and 2 mum. The high resolution images of metaric samples are clearly obtained from - a few meter long distance at the speed of 52 points/s.
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