The molecular strong-field approximation is applied to calculate angle-resolved photoelectron spectra in the process of high-order above-threshold ionization of carbon-monoxide molecules by an elliptically polarized laser field. The theory is formulated to include the Stark shift of the initial bound state of the valence electron. It is shown that the angle-resolved photoelectron spectra of aligned CO molecules exhibit pronounced minima which can be explained by destructive interference of two partial T-matrix contributions. The dependence of contributing partial amplitudes on the laser field ellipticity is analyzed in detail.
We have experimentally observed three types of sidebands in a passively mode-locked soliton fiber laser with large anomalous dispersion for the first time to our best knowledge. By appropriately adjusting the polarization state of laser cavity, the conventional peak sidebands, peak-dip sidebands, and dip sidebands appear in the soliton spectra, respectively. The peak-dip and dip sidebands exhibit distinct characteristics from the conventional peak sidebands. The formation mechanism of the new type sidebands can be attributed to the periodic power variation. This work could help to a deeper insight of the spectrum shaping mechanism of conventional solitons.
The experimental results of a high efficiency infrared laser are demonstrated on a quasi phase matched optical parametric generator in PPMgLN (5% MgO doping) pumped by a 1064 nm Nd:YAG laser. A broad continuous signal spectrum 1.56–1.67 μm are obtained by tuning the crystal temperature from 20°C to 200°C. When the average pump power is 1.82 W with about 70 ns pulse duration operating at a repetition rate of 10 kHz, the maximum total output power of the PPMgLN OPG is about 323.58 mW consisting of 210 mW of 1.639 μm signal radiation and 113.58 mW of 3.02 μm idler radiation.
We investigate the dynamics of a tri-beam laser interacting with a closed three-level atomic system. The Bloch equations are obtained using Hesinberg’s equation of motion. The impact of the resulting parameters on the atomic occupation probabilities and information entropy is discussed. It is shown that the populations are affected by the detuning in different ways which are then compared in order to simulate realizations entanglement through the information entropy.
The hybrid Q-switched and mode-locked (QML) operation of Nd:Lu0.15Y0.85VO4 crystal at 1.34 μm with V:YAG saturable absorber and acousto-optic (AO) modulator has been realized. The laser characteristics are distinctly improved by the hybrid QML if compared to those with the single V:YAG QML. At the pump power of 5.04 W, the Q-switched pulse energy is enlarged to 5.6 times and the Q-switched pulse width is shortened to 40% by the AO modulator in contrast to those of the single passively QML.
Based on our recent realization concerning the geometrically dependent gain coefficient in self-terminating gas lasers, where it is shown that in one-dimensional approach it is z-dependent, we applied the gain formulation to explain, both numerically and analytically, the behavior of the amplified spontaneous emission (ASE) output energy vs. excitation length of the active medium. As an example, we used experimental measurements reported for a KrF excimer laser. In the approach it was realized that it is needed to present a gain-profile slightly lower than the gain-profile deduced from different reports appeared in the literature, where it is also indicating that the contribution of the ASE on the laser output is significant and it is the active medium length dependent. The present analytical presentation of the ASE output energy behavior, also, introduces a generalized formulation compared to that appeared in the literature. With this approach it is possible to remove most of the present ambiguities existing on understanding of the ASE behavior.
A novel configuration of fiber ring laser acoustic sensor, which adopts single-mode fiber as sensing element, is proposed and demonstrated. Linewidth less than 1 kHz is achieved by introducing a segment of erbium-doped fiber in the reflecting arm as saturable absorber. A polarization independent unbalanced Michelson interrogation interferometer and phase generated carrier demodulation technique are adopted to recover signal. Experiments demonstrate that the phase sensitivity is 0.018 rad/nm in good linearity and equivalent minimum detect able length change reaches 19.1 pm.
The nth harmonic emission rate has contributions of the components of the T-matrix element in the direction of the laser-field polarization and in the direction perpendicular to it. Using both components of the T-matrix element we present a theoretical approach for calculation of the ellipticity and the offset angle of high harmonics. The molecular bound state is represented by HOMO or by HOMO-1. We show that high harmonics, generated by molecules oriented by an angle θL with respect to the major semiaxis of the laserfield polarization ellipse, are elliptically polarized even if the applied field is linearly polarized. Using examples of N2 and O2 molecules we show the existence of extrema and sudden changes of the harmonic ellipticity and the offset angle for particular molecular alignment. The interference between different contributions to the T-matrix element depends on the molecular symmetry.
A high stable wavelength-tunable fiber laser is experimentally demonstrated by using a digital-micromirror-device (DMD) processor and a polarization-maintaining erbium-doped fiber amplifier (EDFA).The electronic-addressed DMD processor is able to select and couple a waveband from of the polarization-maintaining EDFA back into the fiber ring to generate a narrow line-width laser output. The tunable fiber laser shows a line-width of 0.02 nm, a tuning step of 0.08 nm over the c-band and a side mode suppression ratio (SMSR) greater than 50 dB. The output power uniformity of 0.01 mW is achieved by using the automatic power control (APC) system under room temperature. The center wavelength fluctuation during 1 h is below 0.01 nm.
We investigate high-order above-threshold ionization (HATI) of homonuclear diatomic molecules by a few-cycle laser pulse. In order to describe molecular HATI in ultrashort laser pulses we have modified our molecular improved strong-field approximation (MISFA), which was developed for long laser pulses and in which the rescattering of the ionized electron off the parent ion was described using the first-order Born approximation (1BA). Now, we introduce the so-called molecular low-frequency approximation (MLFA) in which the elastic rescattering amplitude is calculated exactly. The angle-resolved electron energy spectra for HATI of N2 and O2 obtained using the MLFA are compared with those obtained within the MISFA. The difference between these spectra becomes significant for larger (re)scattering angles. This is due to the fact that the exact scattering amplitude, used in the MLFA, has minima for some values of the rescattering angles that are absent in the 1BA. Also, the rescattering plateau is lower for the MLFA spectra.