Showing papers on "Ruby laser published in 2019"

Crystallization of Amorphous Germanium Films and Multilayer a -Ge/ a -Si Structures upon Exposure to Nanosecond Laser Radiation

Abstract: The processes of the crystallization of amorphous germanium films and multilayer germanium/silicon structures upon exposure to nanosecond (70 ns) ruby laser radiation (λ = 694 nm) are studied. The samples are grown on silicon and glassy substrates by plasma-enhanced chemical vapor deposition. Pulsed laser annealing of the samples is conducted in the range of pulse energy densities Ep from 0.07 to 0.8 J cm–2. The structure of the films after annealing is determined by analyzing the scanning electron microscopy data and Raman spectra. It is established that, after annealing, the films are completely crystallized and, in this case, contain regions of coarse crystalline grains (>100 nm), whose fraction increases, as Ep is increased, and reaches 40% of the area. From analysis of the position of the Raman peaks, it is conceived that the crystalline grains, whose dimensions exceed 100 nm, either contain structural defects or stretching strains. The correlation length of optical vibrations is determined from the phonon confinement model and found to increase from 5 to 8 nm, as Ep is increased. Pulsed laser annealing of multilayer Ge(10 nm)/Si(5 nm) structures induces partial intermixing of the layers with the formation of Ge–Si alloys.

Diode pumped cw ruby laser

Abstract: Cw laser oscillation of ruby at 694 nm in linear and ring resonators is reported for the first time, pumped with a 1 W laser diode at 405 nm as well as 445 nm. The ruby laser operates at room temperature with a threshold of 200 mW at 405 nm and 400 mW at 445 nm. So far output powers up to 36 mW have been achieved pumped at 405 nm. With the ruby ring laser highly coherent single frequency operation will be possible.

A New Energy Device for Skin Activation to Acute Wound Using Cold Atmospheric Pressure Plasma: A Randomized Controlled Clinical Trial

Abstract: More than a half-century has passed since Maiman’s first success with ruby laser treatment. Since then, laser devices have been developed for use in diagnosis and treatment across several fields of medical practice..

Diode-Pumped Cryogenically Cooled Microchip Alexandrite Laser Operating at 680.4 nm Wavelength

Abstract: Alexandrite (Cr3+:BeAl 2 O 4 ) is a broadly-tunable vibronic solid-state laser material allowing laser emission mainly in the near-IR wavelength region with a peak centered around 750 nm [1]. Nevertheless, it allows operation at the electronic transitions distinguished by sharp lines around 680 nm, known as R-lines from ruby laser, which is of great interest for spectroscopic purposes.

Directed UV and X-ray generation in nanomaterials at the optical excitation

Abstract: Efficient electromagnetic emission of radiation in the spectral range with wavelengths shorter than exciting light wavelength was observed at the nanomaterials excitation by laser pulses. Emission was registered in a visible (blue-green) range, in vacuum UV and in soft X-ray. Luminescence was registered both in the air and in the vacuum chamber. Synthetic opal matrices and nanocomposites on their base (matrices infiltrated with different liquids) were used as samples. Luminescence was excited with the help of different lasers: ruby laser, second harmonic of Nd:YAG laser and copper vapor laser. In the visible range two regimes of luminescence were observed: fast (few μs) and slow (up to 12 s). Slow luminescence was registered at temperatures lower than 110 K. Spectra of X-ray emission were registered. The connection of this emission with the triboluminescence effect is considered.

Determination of the parameters of associates in dimethylformamide using stimulated low-frequency Raman scattering

Abstract: Stimulated low-frequency Raman scattering (SLFRS) spectrum in dimethylformamide (DMF) was registered in the range from 0.1 to 1 cm-1. SLFRS is a result of the laser pulses interaction with acoustic oscillations of the associates, therefore knowledge of the SLFRS frequency shifts (and consequently associates eigenvibrations frequencies) gives possibility to estimate the size of DMF associates. Scattering was excited by pulses of a ruby laser with a narrow spectral line and recorded by Fabri-Perot interferometers. In the scattering spectrum SLFRS component was recorded with a frequency shift of 0.33 cm–1 (10 GHz), which corresponds to the size of associates of about 150 nm. Simultaneously with the SLFRS, stimulated Brillouin scattering was recorded in the backward scattering spectrum.

Fabrication and characterization of waveguide lasers operating in the infrared spectral range

Abstract: Since the first demonstration of flashlamp pumped ruby laser by Theodore H. Maiman in 1960, lasers have transformed almost every aspect of our lives. They had an estimated worldwide market worth more than $ 13 billion in 2018. Currently, lasers are being applied in various fields such as, astrophysics - for monitoring the velocities of astronomical objects, archaeology - for analysing ancient artefacts, military - for free space communications and target recognition in the battlefields, medicine - for implementing therapeutics and diagnostic procedures, surveillance - for direct remote sensing of greenhouse gases and harmful toxins, optical sensing – for a lab-on-a-chip integrated bio-medical and chemical analysis, lithography, and telecommunications. In recent years, a lot of attention has been given to the development of lasers emitting at ~2 µm. Such an emission corresponds to the absorption bands of a number of atmospheric molecules (H2O, CO2, N2O). Due to the strong water absorption band, such emission falls into the category of “eye-safe” lasers which makes them especially suitable for open-space applications, e.g. in range-finding (LIDAR systems), atmospheric sensing and wind mapping. Due to the moderate absorption of such lasers in plastic materials, they are suited for engraving, marking and welding of transparent plastics. In molecular spectroscopy, where mid-infrared sources are needed, 2 µm lasers are better suited for pumping the nonlinear crystals that are implemented for generating such longer wavelengths. Typically, laser emission at ∼2 μm is achieved using solid-state materials doped with the trivalent rare-earth thulium (Tm3+) or holmium (Ho3+) ions or a combination (co-doping) of them. Based on the type of gain medium they can be bulk, fiber, slab, thin-disk or (planar / channel) waveguide lasers. The unique advantage offered by a waveguide-based laser source is, its compactness as the optical modes are confined and index-guided in a small volume. This would lead to higher gain, lower laser threshold, small footprints, better heat dissipation and good beam quality. High power continuous wave and pulsed waveguide lasers operating ~ 2 μm are potentially suitable for making compact LIDAR devices operating on a surveillance-airplane or a satellite for directly monitoring and mapping atmospheric CO2. By taking advantage of the direct accesses (to the gain media) offered by surface waveguides, integration with nonlinear materials would lead to more compact devices having advanced functionalities. Specific functionalization (with bioreceptor molecules) or decoration (with plasmonic nanoparticles) of the deposited materials may lead towards active-biosensing and on-chip spectroscopic applications. Hence, the potential applications in environmental monitoring, security, and medicine, greatly motivate the development of such waveguide lasers. The goal of this thesis work was, the fabrication and characterization of compact and efficient waveguide lasers operating around 2 μm. To achieve this thulium and holmium doped monoclinic double tungstate crystalline materials were chosen as gain media, owing to their excellent spectroscopic properties. Their polarized laser emission as well as the high absorption and emission cross-sections, makes these gain media suited for making compact and monolithic waveguide lasers. The combinations of the top-seeded solution growth (TSSG), liquid phase epitaxy (LPE), diamond saw dicing and femtosecond direct laser writing (fs-DLW) methods were employed for fabricating and structuring the waveguides. Furthermore, different characterization techniques such as confocal microscopy, μ-Raman, and μ-luminescence mapping were implemented to assess the quality and suitability of the fabricated waveguides for lasing application. The saturable absorbers employed in the passive Q-switching operation included transition-metal-doped chalcogenide crystals (Cr2+:ZnSe or ZnS), few-layer transition metal dichalcogenide (MoS2) and carbon nanostructures such as graphene and single-walled carbon nanotubes deposited on a transparent substrate or directly onto the surface of the sample containing the waveguides. The fabrication of an active (Tm3+- doped) surface channel waveguide, by combining the LPE and the diamond saw dicing methods resulted in a record slope efficiency (82.6%) almost approaching the theoretical limit. Femtosecond laser written buried channel waveguides (with circular and hexagonal optical-lattice-like cladding), surface channel waveguides (with half-ring-shaped cladding) and Y-branch splitters (with rectangular cladding) were fabricated and studied in a monoclinic double tungstate crystalline material, paving the way towards advanced photonic structures such as a Mach – Zehnder interferometer for biosensing application. Fs-DLW Tm3+ waveguide laser capable of delivering a watt-level output power was demonstrated around 2 μm spectral range. In-band pumping of such Tm3+ waveguide laser resulted in a record slope efficiency (85.7%) and output power (1.37 W). Passive Q-switching of Tm3+ surface waveguide laser based on an evanescent field interaction led to stable operation with a high Q-switching conversion efficiency (approaching 90%) and a lower intensity instability in the pulse train (below 15%). In the pulsed operation regime, sub-100 ns pulses with MHz repetition frequency were demonstrated.

Thomson Scattering Setup

Abstract: The development of Thomson scattering as a (plasma) diagnostic was enabled by powerful lasers, first the Ruby laser and then the Nd:YAG laser, predominantly used in high-temperature, high-density plasmas. High efficiency setups with strong stray-light suppression were developed (Kono, Nakatani in Rev Sci Instrum 71:2716–2721, 2000) to further extent the application of Thomson scattering towards low-density plasmas or even single shot measurements at higher densities. As a non-intrusive and active spectroscopy method it is considered one of the most accurate diagnostics for plasma parameters (Warner, Hieftje in Spectrochim Acta Part B AtIc Spectrosc 57:201–241, 2002, Muraoka, Kono in J Phys D Appl Phys 44:043001, 2011).