Output characteristic of a gain guided, index anti-guided fiber amplifier under the condition of gain saturation.

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.

Ultralow Dispersion Multicomponent Thin-Film Chalcogenide Glass for Broadband Gradient-Index Optics.

A novel photothermal process to spatially modulate the concentration of sub-wavelength, high-index nanocrystals in a multicomponent Ge-As-Pb-Se chalcogenide glass thin film resulting in an optically functional infrared grating is demonstrated. The process results in the formation of an optical nanocomposite possessing ultralow dispersion over unprecedented bandwidth. The spatially tailored index and dispersion modification enables creation of arbitrary refractive index gradients. Sub-bandgap laser exposure generates a Pb-rich amorphous phase transforming on heat treatment to high-index crystal phases. Spatially varying nanocrystal density is controlled by laser dose and is correlated to index change, yielding local index modification to ≈+0.1 in the mid-infrared.

13.5 nm EUV generation from tin-doped droplets using a fiber laser.

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.

Virtual hyperbolic metamaterials for manipulating radar signals in air.

Microwave beam transmission and manipulation in the atmosphere is an important but difficult task. One of the major challenges in transmitting and routing microwaves in air is unavoidable divergence because of diffraction. Here we introduce and design virtual hyperbolic metamaterials (VHMMs) formed by an array of plasma channels in air as a result of self-focusing of an intense laser pulse, and show that such structure can be used to manipulate microwave beams in air. Hyperbolic, or indefinite, metamaterials are photonic structures that possess permittivity and/or permeability tensor elements of opposite sign with respect to one another along principal axes, resulting in a strong anisotropy. Our proof-of-concept results confirm that the proposed virtual hyperbolic metamaterial structure can be used for efficient beam collimation and for guiding radar signals around obstacles, opening a new paradigm for electromagnetic wave manipulation in air.

Comparative extreme ultraviolet emission measurements for lithium and tin laser plasmas.

Detailed spectroscopic studies on extreme UV emission from laser plasmas using tin and lithium planar solid targets were completed. At 13.5 nm, the best conversion efficiency (CE) for lithium was found to be 2.2% at intensities near 7 x 10(10) W/cm(2). The highest CE measured for tin was near 5.0% at an intensity close to 1 x 10(11) W/cm(2).

Solid-state laser spectral narrowing using a volumetric photothermal refractive Bragg grating cavity mirror.

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.

High resolution X-ray micrography of live Candida albicans using laser plasma pulsed point X-ray sources.

Electron microscopy is still the most frequently used method for visualization of subcellular structures in spite of limitations due to the preparation required to visualize the specimen, High resolution X-ray microscopy is a relatively new technique, still under development and restricted to a few large synchrotron X-ray sources. We utilized a single-shot laser (nanosecond) plasma to generate X-rays similar to synchrotron facilities to image live cells of Candida albicans. The emission spectrum was tuned for optimal absorption by carbon-rich material. The photoresist was then scanned by an atomic force microscope to give a differential X-ray absorption pattern. Using this technique, with a sample image time of 90 min, we have visualized a distinct 152.24 nm thick consistent ring structure around cells of C albicans representing the cell wall, and distinct 'craters' inside, one of 570-90 nm diameter and three smaller ones, each 400 nm in diameter. This technique deserves further exploration concerning its application in the ultrastructural study of live, hydrated microbiological samples and of macromolecules.