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Patterns composed of micron‐sized surface structures can abruptly change the properties of an optical wave front, including its phase, amplitude, polarization, and dispersion. Optical components featuring surface micro‐gratings not only possess optical functionalities that can rival or exceed those of traditional bulky components but can also significantly improve the compactness of optical systems. Herein, the design and fabrication process of As2S3 glass‐based micro‐gratings as well as their resulting optical functionality in the infrared regime are reported. The novel two‐step photochemical process consists of spatially controlled direct laser writing and subsequent selective solution etching. The process yields surface micro‐gratings that possess arbitrarily tunable geometries and design patterns on large‐area flat and curved optical surfaces or substrates, offering a potential new avenue for developing aberration‐corrected infrared‐imaging systems. [ABSTRACT FROM AUTHOR]

The morphological features of Candida albicans cell populations were analyzed by X-ray microscopy utilizing a single shot of laser plasma. X-ray micrography of Candida albicans cells produced detailed atomic force images without utilizing sample preparation steps. X-ray micrography with pulsed laser plasmas also provide kinetic and chemical snapshots of the biological ultrastructures of Candida albicans. Furthermore, the microscopic technique eliminates the need for sample preparation steps or colour dyes.

We present a detailed investigation on higher order mode suppression due to differential gain in large mode area step index fiber amplifiers with confined Yb doping using spatially and spectrally resolved imaging (S2). A novel active fiber with Yb doping confined to the central 30% of the core area is fabricated and its performance is directly compared to a fiber with a conventional homogeneously doped core with almost identical parameters. At high pump rates, S2 and beam pointing stability measurements clearly demonstrate fundamental mode operation of the confined doping few mode fiber, even under imperfect launching conditions and environmental perturbations. In addition, we discuss the mode content as a function of gain in co-pumped fiber amplifiers with and without confined rare earth core doping using a power propagation model for fibers with similar parameters to those used in our experiments. Our simulation results as well as amplification experiments indicate the great potential of the confined doping concept for single mode high power operation. [ABSTRACT FROM AUTHOR]

Beam confinement or “no free-space optics” via fiber transmission can achieve improved reliability, lower cost, and reduced component count for active sensing systems. For midinfrared delivery, mechanically robust chalcogenide (arsenic sulfide) single-mode fibers are of interest. A 12-μm core diameter fiber is shown to transport >10 W at 2053 nm, and a 25-μm core diameter fiber enables single-mode beam transport from a 4550-nm quantum cascade laser. As midinfrared sources continue to increase their output power capabilities, chalcogenide fibers will eventually be limited in their power-handling capacity due to optical nonlinearities or thermal failure. These limitations are discussed and analyzed in the context of single-mode chalcogenide fibers in order to provide a framework for power transmission limitations in various operating regimes. [ABSTRACT FROM AUTHOR]

Thulium-doped fiber lasers (TDFLs) have had the second highest growth in average output power next to ytterbiumdoped fiber lasers. This has been enabled by access to high power, high brightness ∼790-nm pump diodes in conjunction with the cross-relaxation process that improves laser efficiency. While numerous high power TDFLs have been recently demonstrated, a 1-kW result from 2010 remains the highest output power system reported to date. This paper reviews these systems and the concepts behind high power TDFLs. The spectroscopic properties of Tm3+ -doped silica are first detailed, revealing complex processes and large variations among published measurements. Notable multi-100 W TDFLs are then summarized, with outputs ranging from 1908 to 2130 nm. Another route for power scaling is to inband pump with another TDFL to enable>90% efficiencies. Both 790- and 1900-nm pumped TDFL architectures are theoretically modeled based on currently available systems. Hindered by high background losses and available pump sources, achieving >4 kW like ytterbium-fiber systems will be a substantial challenge. [ABSTRACT FROM AUTHOR]

Stimulated Brillouin scattering (SBS) is the first nonlinear effect that limits power scaling of narrow linewidth fiber lasers. Nonlinearities typically have a reduced impact when operating at longer wavelengths. However, the SBS gain is considered wavelength independent. To investigate this further, a pulsed 2053 nm source with MHz-linewidth is amplified to >100 W peak powers in single-mode, thulium-doped fiber. The SBS thresholds were measured while varying the pulse duration. Analyzing the SBS threshold measurements suggests that the peak Brillouin gain coefficient is ∼12.2 pm/W with a spontaneous Brillouin bandwidth of ∼17.5 MHz in the passive single-mode fiber at 2053 nm. While the peak Brillouin gain coefficient is comparable to those reported at shorter wavelengths, the spontaneous Brillouin bandwidth is significantly narrower. This indicates that long wavelength sources can inhibit the onset of SBS more readily than short wavelength sources. [ABSTRACT FROM PUBLISHER]

Laser-induced breakdown spectroscopy (LIBS) has been used to study the surface hardness of special aluminum alloys containing zeolite. The aluminum alloy has acquired pronounced changes in its metallurgical properties due to the zeolite inclusion. The surface hardness of the samples under investigation is determined by measuring the spectral intensity ratios of the ionic to atomic spectral lines in the LIBS spectra of samples having different surface hardness values that have been conventionally measured before for comparison. The presence of aluminum silicate mineral in the studied alloys enabled material volume to expand under compression. This feature gave new results in the measurement of hardness via LIBS. It has been proven that the trend of the alloy density change complies with the increase of ionic to atomic spectral line intensity ratio. [ABSTRACT FROM AUTHOR]

The authors report laser oscillation in what appears to be a single transverse mode with very large mode area in optical fibers having heavily Nd-doped 100 μm diameter cores with refractive index significantly lower in the core than in the surrounding cladding. Since fibers of this type cannot support conventional index-guided modes, their results appear to confirm a recent analysis which predicts gain-guided single-mode propagation in index antiguided fibers, provided the gain coefficient in the core exceeds a threshold value. Fibers of this type may be of significant interest for amplifiers and oscillators having large power outputs and/or small nonlinear pulse distortion. [ABSTRACT FROM AUTHOR]

There is increasing interest in extreme-ultraviolet (EUV) laser-based lamps for sub-10-nm lithography operating in the region of 6.6 nm. A collisional-radiative model is developed as a post-processor of a hydrodynamic code to investigate emission from resonance lines in Kr, Gd, and Tb ions under conditions typical for mass-limited EUV sources. The analysis reveals that maximum conversion efficiencies of Kr occur at 5×1010W/cm2, while for Gd and Tb it was ≃0.9%/2πsr for laser intensities of (2-5)×1012W/cm2. [ABSTRACT FROM AUTHOR]

In this article, the author responds to a comment on article "Confined propagation and near single-mode laser oscillation in a gain-guided, index antiguided optical fiber." The author discusses the work of researcher A. E. Seigman on index antiguided fibers. He further discusses various photographs reflecting the cladding circumference.

Abstract: Double-Pulse Laser-Induced Breakdown Spectroscopy of iron using both Nd:YAG and TEA–CO2 lasers has been investigated to better understand mechanisms of signal enhancement. The signal dependence on the delay between the two laser pulses shows an enhanced signal when the CO2 laser pulse interacts with the sample before the Nd:YAG pulse. Signal kinetics and a simple model of sample heating by the CO2 pulse show that the enhancement during the first 700ns is due primarily to sample heating. Images of the sample surface after ablation as well as time-integrated pictures of the plasma suggest that particles are ejected from the surface during the first microseconds after the arrival of the CO2 pulse and provide fuel for the subsequent plasma created by the Nd:YAG laser. [Copyright &y& Elsevier]

We numerically investigate the output characteristic of a gain guided, index anti-guided fiber amplifier with saturated gain. The result shows that there is an output power limitation depending on the inherent leakage loss of the fiber amplifier. But we find that the amplifier with the multimode condition can operate to get a high power output with keeping a good beam shape like a Gaussian beam.

A comprehensive study of the spectral and Mo-Si mirror inband EUV emission from tin-doped droplet laser plasma targets irradiated with a single 1064 nm beam from an Yb:doped fiber laser is reported.With pre-pulse enhancement, in-band conversion efficiency of approximately 2.1% is measured for laser irradiance intensities near 8 x 10(10) W/cm(2). This is the first study to be reported that uses a high-power, high repetition rate fiber laser with the high repetition rate droplet targets where EUV generation from plasmas is measured.

Dramatic spectral narrowing of two normally broadband lasers, Ti:sapphire and Cr:LiSAF, was achieved by simply replacing the output mirror with a reflective, volumetric Bragg grating recorded in photothermal refractive glass. The output power of each laser was unchanged from that obtained using dielectric coated output mirrors with the same output coupling as the Bragg grating while spectral brightness increased by 3 orders of magnitude.