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Featured Application: High-quality and high-throughput eco-friendly regimes of laser cutting glasses, sapphire and other transparent materials are found based on the model. Possible practical applications are in display manufacturing, the automotive and other industries. A strategy is proposed for achieving a practically important mode of laser processing—a so-called "smooth" laser filamentation cutting (LFC) of transparent materials by a moving beam of a pulse-periodic pico- or subpicosecond laser. With such cutting, the surface of the sidewalls of the cuts have a significantly improved smoothness, and, as a result, the laser-cut plates have increased resistance to damage and cracking due to mechanical impacts during their subsequent use. According to the proposed analytical model, for the case when each filament is formed only by a single laser pulse, the strategy of such cutting is defined by a set of necessary conditions, whose implementation requires, in turn, a certain selection and matching with each other of irradiation parameters (pulse duration and energy, repetition rate, pitch of filaments following) and of material parameters—thermal, optical and mechanical strength constants. The model shows good agreement with experiments on sapphire and tempered glass. Besides, LFC modes are also predicted that provide very high cutting speeds of the order of 1–25 m/s or more, or allow cutting with an extremely low average laser power, but still at a speed acceptable for practical applications. [ABSTRACT FROM AUTHOR]

The mechanisms underlining the cell adaptive and/or activating oxidative stress, called low level light or photobiomodulation therapies (PBMT), still remain unclear for the near-infrared spectrum range (750–3000 nm), especially for the 1265–1270 nm range (highest absorption by molecular oxygen). It is most probable that the mitochondria may also appear to be the main target for these wavelengths. It is known that mitochondria can generate ROS under visible and 800–1060 nm spectrum range irradiation, which in turn control voltage-dependent anion channels (VDAC). Here we investigated cellular damage regarding VDAC activity, level of oxidative stress, malondialdehyde content, cell viability, mitochondrial potential and mass, GSH level, mitochondrial and nuclear DNA damage in the cancer cell culture exposed to low-level laser irradiation at 1265 nm. We used a continuous wave laser with output power 4 mW; the energy densities employed were 0.3–9.45 J/cm 2. We observed that the laser radiation at 1265 nm can induce the oxidative stress, enhance apoptosis, and disturb mitochondrial functioning at the energy density of 9.54 J/cm2. In addition, inhibition of VDAC enhances the observed effects. It has been shown that the laser irradiation at 1265 nm damages mitochondrial DNA but does not affect the nuclear DNA. The performed experiments bring us to the conclusion that the laser irradiation at 1265 nm can affect cells through mitochondrial damage and the inhibition of VDAC enhances effects of PBMT. [ABSTRACT FROM AUTHOR]

In this paper, we report on the analytical study of a first-order quasi-phase-matched structure based on a periodically switched nonlinearity. The general average equations describing parametric wave interaction for this structure are obtained. The theoretical results are then used to analyze the special case of a device based on a semiconductor Alx,Ga1-xAs waveguide for efficient frequency doubling in the mid-infrared to the far-infrared range. The necessary conditions to obtain an optimal configuration are discussed in both continuous wave and femtosecond-pulse regimes. Our analysis indicates that the conversion efficiency obtained should significantly exceed the efficiency obtained with a periodically poled lithium niobate crystal at long wavelengths. Finally, we include the preliminary results of the experimental demonstration of a waveguide device based on alternating domains of GaAs and Al0 .4 Ga0 .6 As. [ABSTRACT FROM AUTHOR]

A response from the authors of the article "SESAM-free mode-locked semiconductor disk laser" in the 2012 issue is presented.

Edge-emitting mode-locked quantum-dot (QD) lasers are compact, highly efficient sources for the generation of picosecond and femtosecond pulses and/or broad frequency combs. They provide direct electrical control and footprints down to few millimeters. Their broad gain bandwidths (up to 50 nm for ground to ground state transitions as discussed below, with potential for increase to more than >200 nm by overlapping ground and excited state band transitions) allow for wavelength-tuning and generation of pico- and femtosecond laser pulses over a broad wavelength range. In the last two decades, mode-locked QD laser have become promising tools for low-power applications in ultrafast photonics. In this article, we review the development and the state-of-the-art of edge-emitting mode-locked QD lasers. We start with a brief introduction on QD active media and their uses in lasers, amplifiers, and saturable absorbers. We further discuss the basic principles of mode-locking in QD lasers, including theory of nonlinear phenomena in QD waveguides, ultrafast carrier dynamics, and mode-locking methods. Different types of mode-locked QD laser systems, such as monolithic one- and two-section devices, external-cavity setups, two-wavelength operation, and master-oscillator power-amplifier systems, are discussed and compared. After presenting the recent trends and results in the field of mode-locked QD lasers, we briefly discuss the application areas. [ABSTRACT FROM AUTHOR]