Huang Guang-ming

Extended Measurement of the v2(1−←0+) Band of H3O+ by Mid-Infrared Diode Laser Spectroscopy

Twenty-five new R-branch lines of the v2 (1−←0+) band of H3O+ are measured using diode laser velocity modulation spectroscopy between 1070 and 1230 cm−1. The H3O+ ions are produced in a high voltage ac discharge with water diluted in helium. The observed lines together with all the previously published measurements are fit to the standard vibration-rotational Hamiltonian of an oblate symmetric top, yielding a set of improved molecular constants. All the sextic centrifugal distortion constants for both 0+ and 1− states are determined precisely. The observed R(13,0) transition is shifted about -0.129 cm−1 from its calculated value, indicating that a near degeneracy exists between the (13, 0)+ and (13, 3)− ground-state rotation-inversion levels.

A new analysis of the ν2 fundamental band of H2O

This paper reports that the absorption spectra of H2O+ have been measured by tunable mid-infrared diode laserspectroscopy in the spectral range of 1100–1380 cm-1. The H2O+ ions are generated in an AC glow discharge of the gaseous mixtures of H2O/He and detected with the velocity modulation technique. Forty new lines are assigned to theν2 fundamental band of H2O+(2B1). The observed lines together with other data published previously are fitted to the standard effective Hamiltonian of an asymmetric top, yielding a set of improved rotational constants, spin-rotation constants and their quartic and sextic centrifugal distortion constants for the ν2=1 vibrational state of H2O+.

Ultra-Long Haul L-Band WDM Transmission over a Standard Single-Mode Fibre Loop Using DCF+CFBG Hybrid Dispersion Compensation

We demonstrate a 10.7 Gb/s-line-rate L-band wavelength-division-multiplexer (WDM) loop transmission over a 1890-km standard single-mode fibre (SSMF) with a 100-km amplifier spacing as well as non-return-to-zero (NRZ) format. The dispersion compensating fibre (DCF) plus chirped fibre Bragg grating (CFBG) is employed for hybrid inline dispersion compensation. The power penalty of each channel is less than 3 dB after three-loop transmission. The experimental results show that high-performance CFBGs can be successfully used in ultra-long haul (>1000 km) WDM systems. We also point out that the all-CFBG compensation scheme is not suitable for re-circulating loop transmissions.

Population Inversion of a V-type Three-Level Atom due to the Effect of Cavity-Induced Quantum Interference

A cavity-modified master equation is derived for a coherently driven V-type three-level atom coupled to a single-mode cavity in the bad cavity limit. The influences of the cavity-induced quantum interference on the steady-state populations are analysed. We show that the population inversion can occur due to the effect of cavity-induced quantum interference. PACS: 42. 50. Dv, 42. 50. Gy

Absorption Spectrum of a Driven Two-Level Atom in a Tunable Cavity with Injected Squeezed Vacuum

The absorption spectrum of a driven two-level atom in a frequency tunable cavity with injected squeezed vacuum is investigated. The line shape of the spectra depends on the relative phase between the driving field and the squeezed vacuum, and the frequency detuning between the driving field and the cavity mode. Line narrowing and probe gain can occur and be enhanced by adjusting the phase and detuning.

GLOBAL ANALYSIS OF SPECTRA OF THE PO 2 RADICAL IN THE GAS PHASE

A global analysis of all available and identified spectra of the PO2 radical has been performed. In this analysis, the infrared spectra of the nu(3) band, the microwave and far infrared laser magnetic resonance transitions in the ground state are fitted simultaneously to the effective Hamiltonian for asymmetric top molecules. Since the analysis absorbs reliable experimental data extensively, it bears the most precise and most complete set of molecular constants for PO2. These molecular constants can, be used to reproduce the spectra of PO2 accurately. Attention is also paid to the similarity and difference between PO2 and NO2.

Coherent population trapping in multilevel laser-induced continuum structure system including cascade two-photon processes

We have investigated the atomic coherent population trapping in a multilevel laser-induced continuum structure system including cascade two-photon processes, in which two sets of quasicontinua of excited levels to be modeled as the Bixon-Jortner quasicontinuum are laser-embedded into a previously structureless atomic continuum. The condition leading to the atomic coherent population trapping and the coherent population trapping state are given explicitly. And the effects of the Fano factors, the laser intensities and the detunings on the amount of population trapped in the atomic bound states and the populations distributed in the two sets of quasicontinua are also examined.

Nonlocality and purity in atom—field coupling system

The effects of initial field state and thermal environment on quantum nonlocality and linear entropy in an atom–field coupling system are investigated. We found that if the cavity is lossless and the reservoir is in vacuum, the atom–field state can exhibit quantum nonlocality periodically and the linear entropies of the atom and the field also oscillate periodically with a period the same as that of quantum nonlocality. And if the cavity dissipation is very weak and the average photon number of the reservoir is very small, the quantum nonlocality will be lost and the linear entropies of the atom and the field oscillate with a decreasing amplitude. The rapidity of the loss of the quantum nonlocality depends on the amplitude of the initial squeezed coherent state, the cavity damping constant κ and the average photon number N of the thermal reservoir. The stronger the field and the larger the constant κ and the average photon number N could be, the more rapidly the nonlocality decreases.

Quantum nonlocality in atom-field coupling system via degenerate Raman processes with cavity damping

The property of quantum nonlocality in the atom-field coupling system via degenerate Raman processes with cavity damping is investigated. It is found that if the cavity dissipation is very weak, the atom-field state can exhibit quantum nonlocality periodically. The rapidity of the loss of the quantum nonlocality depends on the amplitude of the initial coherent state and the cavity damping constant. The stronger the field is and the larger the damping constant could be, the more rapidly the nonlocality decreases.