[en] Dear readers and authors, First of all, we would like to inform you on our main achievement over the past year: The impact factor of Laser Physics Letters reached 5.502 in 2009. This has promoted the journal to one of the leading journals in the world in the field of laser physics. We are very grateful to all friends of the journal who have sent us their congratulations with this success. Of course, we understand that this success is caused by several reasons. One of them is a high quality of papers submitted by our authors. Thanks are due to all of the authors for their contributions to this success of the journal. The second reason is the hard work of our referees who have the highest qualification, and, moreover, who are capable of providing their reports within just a few days. We acknowledge the important role of the annual International Laser Physics Workshop (LPHYS) attracting the authors for writing articles for LPL. The last, though not the least, we are very grateful to our distinguished publisher Wiley for its valuable contribution and endless efforts to make things better and, especially, to Wiley's V-P Steven Miron for his useful counsels. The location of the annual Workshop LPHYS varies each year, which makes it possible to attract scientists from different countries. In 2010, the annual international Laser Physics Workshop (LPHYS'10) was held in Brazil. Using the occasion, we stress the great work done by Prof. Bagnato for organizing this conference. In 2011, the conference LPHYS'11 will be held from July 11 to July 15 in the city of Sarajevo, Bosnia and Herzegovina, in the Congress Center of the Hotel Hollywood. We plan the participation of about 600 scientists from more than 30 countries. Concluding, we hope that Laser Physics Letters, with the help of our authors, will support and further strengthen the status of a leading journal in the field of laser physics. Sincerely Yours,

[en] We demonstrate clear inhomogeneous linewidth broadening for the disordered laser crystal Nd:BaLaGa₃O₇ (Nd:BLG), which is very promising for the replacement of Nd:glass for ultrafast sources in multiwatt power applications. A Nd:BLG laser oscillator passively mode-locked and pumped by a Ti:sapphire laser generated pulses of 316-fs duration at 1060 nm, whose spectrum completely fills the fluorescence peak at such wavelength. More interestingly, sub-picosecond pulses were smoothly tunable in a 20-nm range, from 1070 to 1090 nm. The shortest pulses achieved were 290 fs long, centered at 1075 nm. (letter)

[en] The scattering effect of a circular aperture, located in an impedance plane, on a Bessel beam is investigated by decomposing the scattered wave into two subcomponents, namely the geometrical optics and diffracted fields. The diffracted waves are investigated with the aid of the geometrical theory of diffraction. The detour parameter is evaluated and the existence zones of the geometrical optics fields are determined. The various aspects of the reflected and transmitted scattered waves, including the self healing of the beam, are studied numerically. (letter)

[en] We proposed a short-linear-cavity fiber laser with a virtual-folded-ring configuration, which combines the advantages of ring lasers and short-linear-cavity lasers. An all-fiber quarter-wave plate was used inside the cavity to introduce polarization retardation. By retarding the polarization of the travelling waves, the spatial-hole-burning effect was weakened and the efficient cavity length was extended to nearly twice its physical length. As a result, a single-frequency laser output with a linewidth of less than 820 Hz was obtained from the free-running fiber laser. The relaxation oscillation frequency was observed to be around 280 kHz and the signal to noise ratio of the laser output was >72 dB. (letter)

[en] We demonstrated efficient vacuum and extreme ultraviolet third harmonic generation driven by intense ultrashort fundamental-wave pulses. As the driving pulses were tightly focused upon an argon gas jet to reach relatively high peak intensities, we achieved vacuum ultraviolet pulse energy of 6.4 μJ at 133 nm and extreme ultraviolet (XUV) pulse energy of 199 nJ at 89 nm, with the corresponding conversion efficiency up to 0.26‰ and 0.008‰, respectively. In addition, the intense 400-nm ultrashort driving pulse was up-converted to a 79-nm XUV pulse with pulse energy of 251 nJ and the harmonic generation efficiency was 0.01‰. (letter)

[en] We demonstrate a source producing 45 fs laser pulses with 273 GHz repetition rate centered at 1550 nm based on compression of beatnotes from two single-frequency distributed feedback lasers inside a highly nonlinear fiber (HNLF). Phase distortion measurements performed with line-by-line pulse shaping yield primarily second order dispersion (SOD). The magnitude and sign of the SOD depends on the length of the HNLF and the power of the radiation launched. The results of spectral phase measurements allowed source optimization to yield the shortest pulses. (letter)

[en] We demonstrate a compact Raman all-fiber oscillator for cylindrical vector beam generation. The laser is based on a strongly guiding passive fiber with two fiber Bragg gratings inscribed in it, which separates the different transverse modes in wavelength. Additionally, the impact of core ellipticity in strongly guiding fibers for the generation of cylindrical vector beams is theoretically analyzed. In this work, the elliptical core is compensated by introducing stress. Thereby, an azimuthally polarized beam with an output power of 480 mW and a radially polarized beam with an output power of 400 mW are generated, limited only by the onset of nonlinear effects inside the Raman fiber oscillator. Switching between these two cylindrical vector beams is possible by rotating the polarization of the pump. The presented concept is well suited for all-fiber microscopic applications. (letter)

[en] Squeezed vacuum can be obtained by an optical parametric amplifier (OPA) with the quantum vacuum state at the input. We are interested in a degenerate type-I OPA based on parametric down-conversion (PDC) where, due to phase matching requirements, an extraordinary polarized pump must impinge onto a birefringent crystal with a large χ⁽²⁾ nonlinearity. As a consequence of the optical anisotropy of the medium, the spatial spectrum of the generated radiation is affected by the transverse walk-off. In this work we describe a method that reduces the spatial distortions, by using two consecutive crystals instead of one. We show that after anisotropy compensation the two-photon amplitude becomes symmetric, allowing for a simple Schmidt expansion, a procedure that in practice requires states that come from experimental systems free of anisotropy effects. Qualitative experimental observations are made for the case of high-gain PDC. (letter)

[en] We present a new technique for stabilizing and monitoring Bloch oscillations of ultracold atoms in an optical lattice under the action of a constant external force. In the proposed scheme, the atoms also interact with a unidirectionally pumped optical ring cavity whose one arm is collinear with the optical lattice. For weak collective coupling, Bloch oscillations dominate over the collective atomic recoil lasing instability and develop a synchronized regime in which the atoms periodically exchange momentum with the cavity field. (letter)

[en] Sub-micron quasi-regular surface textures were fabricated on surfaces of pure titanium (VT1-0) with micro- and ultrafine-grained bulk structures by multiple femtosecond laser pulses in the scanning mode and characterized by scanning electron and atomic force microscopy. Their wetting characteristics acquired for the initial non-textured and as-textured samples, as well as upon ultrasonic and plasma cleaning, demonstrate corresponding drastic changes of the wetting angles from 87° to ≤ 10°, with much more pronounced contamination, cleaning and wetting effects for the ultrafine-grained titanium. (letter)