Abnormal phenomenon of ac Stark splitting in magneto-optical traps

We experimentally study the ac Stark splitting in D2 line of cold Rb-87 atoms. The frequency span between the Autler-Townes doublets is obviously larger than that derived from theoretical calculation. Two physical effects, which increase the effective Rabi frequency, contribute to the splitting broadening. First, atoms tend to distribute in strong lield places of a inhomogeneous red-detuned light field. Second, atoms reabsorb scattered light when they are huge in number and high in density.

Light-induced evaporative cooling in a magneto-optical trap

This paper presents an experimental demonstration of light-induced evaporative cooling in a magneto-optical trap. An additional laser is used to interact with atoms at the edge of the atomic cloud in the trap. These atoms get an additional force and evaporated away from the trap by both the magnetic field and laser fields. There remaining atoms have lower kinetic energy and thus are cooled. It reports the measurements on the temperature and atomic number after the evaporative cooling with different parameters including the distance between the laser and the centre of the atomic cloud, the detuning, the intensity. The results show that the light-induced evaporative cooling is a way to generate an ultra-cold atom source.

Magnetic field modulated direct overwrite with pulsed laser irradiation for TbFeCo magneto-optical disks

WE have designed a dual-beam magneto-optical (MO) storage system to test the dynamic storage properties of MO disks. The characteristics of this dual-beam system are demonstrated. Magnetic field modulated direct overwrite, which is a promising technique for highspeed MO storage, is realized on TbFeCo MO disks with this dual-beam MO system. The effect of light intensity, magnetic field intensity, and linear velocity of the disk and the modulating frequency variation on carrier-to-noise ratio is investigated. (C) 1997 Society of Photo-Optical Instrumentation Engineers.

Analysis on a new type magneto-optical disk for blue lasers

The conventional TbFeCo magneto-optical (MO) medium has a relatively smaller Kerr rotation angle in the blue region than in the red. With the recording wavelength gradually moving to the short wavelength, if TbFeCo is still used as recording medium, the conventional MO disk structure must be optimized to get a larger carrier to noise ratio (CNR). Sabi et al. have found that adding a metal layer attached to the TbFeCo film as thermal control layer is a useful way to get a high CNR. In this paper, we proved this through calculation, and carried out optimization of the new type of disk. Calculation results showed that the new structure is useful in preventing an excessive temperature increase, and has a better thermal response. (c) 2005 Elsevier B.V. All rights reserved.

Analysis of the additional modulation of semiconductor lasers using optical heterodyne techniques

In this letter, the power spectrum of a cooled distributed feedback laser module is measured using the self-heterodyne technique. Periodical oscillation peaks have been observed in the measurement. Further investigation shows that the additional modulation signal is coupled from the thermal electric cooler (TEC) controller to the laser driver, and then applied to the laser diode. The additional modulation can be eliminated by properly isolating the laser driving source from the TEC controller.

Development of current-based microscopic defect analysis method using optical filling techniques for the defect study on heavily irradiated high-resistivity Si sensors/detectors

Current-based microscopic defect analysis method such as current deep level transient spectroscopy (I-DLTS) and thermally stimulated current have been developed over the years at Brookhaven National Laboratory (BNL) for the defect characterizations on heavily irradiated (Phi(n) >= 10(13) n/cm(2)) high-resistivity (>= 2 k Omega cm) Si sensors/detectors. The conventional DLTS method using a capacitance transient is not valid on heavily irradiated high-resistivity Si sensors/detectors. A new optical filling method, using lasers with various wavelengths, has been applied, which is more efficient and suitable than the traditional voltage-pulse filling. Optimum defect-filling schemes and conditions have been suggested for heavily irradiated high-resistivity Si sensors/detectors. (c) 2006 Published by Elsevier Ltd.

Magneto-optical properties of diluted magnetic semiconductor quantum dots

The magnetoexciton polaron (MP) is investigated theoretically in a diluted magnetic semiconductor quantum dot (QD), with the Coulomb interaction and the sp-d exchange interaction included. The MP energy decreases rapidly with increasing magnetic field at low magnetic field and saturates at high magnetic field for small QDs, and the dependences of the MP energy on magnetic field are quite different for different QD radii due to the different carrier-induced magnetic fields B-MP. The competition between the sp-d exchange interaction and the band gap shrinkage results in there being a maximum exhibited by the MP energy With increasing temperature. Our numerical results are in good agreement with experiment (Maksimov A A, Bacher G, MacDonald A, Kulakovskii V D, Forchel A, Becker C R, Landwehr G and Molenkamp L W 2000 Phys. Rev. B 62 R7767).

Development of current-based microscopic defect analysis method using optical filling techniques for the defect study on heavily irradiated high-resistivity Si sensors/detectors

Current-based microscopic defect analysis method such as current deep level transient spectroscopy (I-DLTS) and thermally stimulated current have been developed over the years at Brookhaven National Laboratory (BNL) for the defect characterizations on heavily irradiated (Phi(n) >= 10(13) n/cm(2)) high-resistivity (>= 2 k Omega cm) Si sensors/detectors. The conventional DLTS method using a capacitance transient is not valid on heavily irradiated high-resistivity Si sensors/detectors. A new optical filling method, using lasers with various wavelengths, has been applied, which is more efficient and suitable than the traditional voltage-pulse filling. Optimum defect-filling schemes and conditions have been suggested for heavily irradiated high-resistivity Si sensors/detectors. (c) 2006 Published by Elsevier Ltd.

DEVELOPMENT OF CURRENT-BASED MICROSCOPIC DEFECT ANALYSIS-METHODS AND ASSOCIATED OPTICAL FILLING TECHNIQUES FOR THE INVESTIGATION ON HIGHLY IRRADIATED HIGH-RESISTIVITY SILICON DETECTORS

Current based microscopic defect analysis methods such as current deep level transient spectroscopy (I-DLTS) and thermally stimulated current (TSC) have been further developed in accordance with the need for the defect analysis of highly irradiated (Phi(n) > 10(13) n/cm(2)) high resistivity silicon detectors. The new I-DLTS/TSC system has a temperature range of 8 K less than or equal to T less than or equal to 450 K and a high sensitivity that can detect a defect concentration of less than 10(10)/cm(3) (background noise as low as 10 fA). A new filling method using different wavelength laser illumination has been applied, which is more efficient and suitable than the traditional voltage pulse filling. It has been found that the filling of a defect level depends on such factors as the total concentration of free carriers generated or injected, the penetration length of the laser (laser wavelength), the temperature at which the filling is taking place, as well as the decay time after the filling (but before the measurement). The mechanism of the defect filling can be explained by the competition between trapping and detrapping of defect levels, possible capture cross section temperature dependence, and interaction among various defect levels in terms of charge transferring. Optimum defect filling conditions have been suggested for highly irradiated high resistivity silicon detectors.

Investigation of ion-atom collision dynamics through imaging techniques

The principle and technique details of recoil ion momentum imaging are discussed and summarized. The recoil ion momentum spectroscopy built at the Institute of Modern Physics (Lanzhou) is presented. The first results obtained at the setup are analyzed. For 30 keV He2+ on He collision, it is found that the capture of single electron occurs dominantly into the first excited states, and the related scattering angle results show that the ground state capture occurs at large impact parameters, while the capture into excited states occurs at small impact parameters. The results manifest the collision dynamics for the sub-femto-second process can be studied through the techniques uniquely. Finally, the future possibilities of applications of the recoil ion momentum spectroscopy in other fields are outlined.