Showing papers on "Ruby laser published in 2008"

Enhancement of the JET edge LIDAR Thomson scattering diagnostic with ultrafast detectors.

Abstract: The edge light detection and ranging (LIDAR) Thomson scattering diagnostic at the Joint European Torus fusion experiment uses a 3 J ruby laser to measure the electron density and temperature profile at the plasma edge. The original system used a 1 GHz digitizer and detectors with response times of ≈650 ps and effective quantum efficiencies <7%. This system has recently been enhanced with the installation of a new 8 GHz digitizer and four new ultrafast GaAsP microchannel plate photomultiplier tube detectors with response times of <300 ps and effective quantum efficiencies in the range of ∼13%−20% (averaged over λ=500–700 nm). This upgrade has enabled the spatial resolution to be reduced to ∼6.3 cm along the laser line of sight for a laser pulse of 300 ps full width at half maximum, which is close to the requirements for the ITER core LIDAR. Performance analysis shows that the new system will have an effective spatial resolution of up to 1 cm in the magnetic midplane via magnetic flux surface mapping.

Progress in the pumping of a gamma‐ray laser

Abstract: A gamma‐ray laser would stimulate the emission of radiation at wavelengths below 1 A from excited states of nuclei. However, the anticipation of a need for very high pump powers tended to discourage early research and the difficulties in demonstrating a device were first assumed to be insurmountable. Over the past decade advances in pulsed power technology have changed these perceptions and studies have built a strong momentum. The concept for a nuclear analog of the ruby laser now appears in the textbooks and many of the component steps for pumping the nuclei have been demonstrated experimentally. A quantitative model based upon the new data and concepts has shown the gamma‐ray laser to be feasible if some real isotope has its properties sufficiently close to the ideals modeled. The greatest positive impact upon feasibility has come from the discovery of giant resonances for pumping nuclei that greatly reduce the levels of pump power needed.

High-speed time-resolved visualisation of laser-induced plasma explosions

Abstract: The early evolution of laser-induced plasma explosions has been investigated by means of a high-speed time-resolved schlieren visualisation. Images were obtained with a high-speed video camera yielding frame rates of up to 1 million frames per second at a frame resolution of 312 by 260 pixels. With this setup it was possible to resolve the temporal development of the ionised plasma kernel and its associated shock wave. The plasma is formed by focusing a pulsed ruby laser beam, with pulse energies of up to 4.5 J. The time-resolved visual data have been used to yield shock speeds, from which, together with direct energy measurements, one can determine the portion of energy released by the plasma explosion to drive the shock. Shock sphericity as well as plasma growth and emission lifetimes have also been evaluated. The location of longest emission lifetime was found to change as a function of laser pulse energy: for high energy pulses, the longest-living plasma luminosity was located ahead of the focal spot, i.e. closer to the laser source, while with lower energy pulses the longest-living plasma luminosity was located behind the focal spot. This behaviour was also observed for double-pulsed plasma explosions, when a second laser pulse was generated with a delay time of 50 μs. The experiments show that for single pulses, more than 50 percent of the laser energy is expended in generating the shock wave.

In situ window cleaning by laser blowoff through optical fiber.

Abstract: The feasibility of a window cleaning system based on the laser blowoff technique is investigated to remove the impurity deposition on vacuum windows of the modified reversed field experiment fusion device. The laser pulse is sent to the window through a fused silica fiber optic (φ=1mm), then focused on its internal surface, single shot ablating up to ∼5mm2 of the impurity layer; the focused pulse is scanned across the window to clean its entire surface. The composition of the deposited layer is studied through the secondary ion mass spectrometry and profilometry techniques. Effectiveness of cleaning is analyzed in terms of quality of the cleaned spot, its dimension, repetition rate of the laser, and its wavelength. The energy damage threshold of the fiber optic is also investigated. Three different lasers (microjoule Nd:YAG, Nd:YLF, and ruby) are first tested directly on the window; then only the ruby laser beam is propagated through an optical fiber and tested.

Ruby laser pulse effects in ion implanted semiconductors

Abstract: The effects of Q‐switched ruby laser irradiations in ion implanted semiconductros will be reviewed with the main emphasis on the amorphous to single crystal transition. To compare with experiments, the heat equation is solved numerically to give the time evolution of temperature and melting as a function of the pulse energy density and time duration. The transition to single crystal occurs above a well defined threshold energy density at which the liquid layer wets the underlying single crystal substrate. The influence of the absorption coefficient in determining the threshold energy density is discussed for ruby and Nd wavelength irradiation in silicon samples with different amorphous thicknesses. Measurements in As and Cu implanted silicon indicate the occurrence of an As broadening and a Cu accumulation at the sample surface after ruby laser irradiations. These results can be explained in terms of matter transport in a liquid phase governed by diffusion and segregation coefficients. Local accumulation ...

Laser annealing of ion implanted silicon

Abstract: The physical and electrical properties of ion implanted silicon annealing with high powered ruby laser radiation are summarized. Results show that pulsed laser annealing can lead to a complete removal of extended defects in the implanted region accompanied by incorporation of dopants into lattice sites even when their concentration far exceeds the solid solubility limit. Implanted dopants are redistributed considerably by pulsed laser annealing, and parameters influencing the profiles are discussed. Calculations and experimental results provide strong evidence that the pulsed laser annealing mechanism involves melting of the crystal to a depth of several thousand angstroms, dopant diffusion in liquid silicon, and subsequent liquid phase epitaxial regrowth from the underlying substrate. The application of pulsed laser irradiation to materials processing areas other than ion implantation is briefly discussed.

Transmission electron microscopy and electrical properties measurements of laser doped silicon and GaAs

Abstract: High quality silicon p‐n junctions have been prepared by alloying a vacuum evaporated Al film into n‐type Si and by epitaxial regrowth of an As doped Si amorphous layer onto p‐type (100) Si by a single short pulse of ruby laser radiation. Transmission electron microscopy investigations indicated that a defect‐free epitaxial layer was grown on the (100) Si surface; however, some polycrystalline structure in the very near‐surface region was observed, which does not seem to affect the junction characteristics. Laser assisted junction formation in GaAs was demonstrated by alloying Mg films into n‐type GaAs; however, diode characteristics show a large leakage current which may have been caused by the surface damage.

Uv light generation by frequency conversion of radiation of a ruby laser pumped with a second harmonic of a solid-state laser

Abstract: A system and method for generating ultraviolet laser radiation by pumping a ruby based active laser medium in a second complex laser cavity with an output from a first complex laser cavity. The laser system includes a first complex optical cavity a second complex optical cavity, an output from the first complex optical cavity at a second harmonic of the first fundamental frequency pumps a ruby based active medium of the second complex optical cavity. In some embodiments, the ruby based active medium can be Cr:Al 2 O 3 type ruby.

Some electro-physical properties of InSb and InAs layers that were received with the help of methods of relaxed optics

Abstract: The basic problems of the receiving p-n junctions in ion implanted InSb Mg+/InSb after CO2-laser irradiation and in p-InSb and p-InAs after Ruby laser irradiation are represented. Proper Volt-Ampere characteristics are analyzed. The basic physical mechanisms of receiving these structures are discussed too. Basic cause of difference these p-n junctions is various mechanisms of irreversible interaction light and semiconductor (self-absorption for Ruby laser irradiation and "damage"-absorption for CO2-laser irradiation).© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Pulsed annealing of implanted semi‐insulating GaAs

Abstract: Experiments are reported on the annealing of Se+ implanted semi‐insulating GaAs by a laser pulse or an electron beam pulse. Laser annealing was accomplished by a ruby laser pulse (λ=0.694μm, tp?15ns); an electron beam with an average electron energy of ∠20keV and a pulse duration of ∠0.1μs was employed for electron beam annealing. The implanted and annealed samples were analyzed electrically with the standard Van der Pauw type of resistivity measurements. In some cases, differential Hall‐effect measurements were used for determining the electron concentration profiles. The results indicate that after both types of annealing, better activation of Se+ ions occurred in the layers that were amorphous following implantation, when compared to the layers that remained crystalline after implantation.

Lattice location of As and Sb implanted in silicon after annealing with a pulsed ruby laser

Abstract: The lattice location of implanted arsenic and antimony in single crystal silicon [(100) orientation] after pulsed laser annealing has been studied using positive ion channeling‐backscattering. The samples have been implanted with 100 keV 75As or 121Sb to doses in the range 1×1015 to 3×1016/cm2. The samples were subsequently annealed using the Q‐switched output of a pulsed ruby laser (1.5–1.7 J/cm2, ∠50×10−9 sec pulse duration). Channeling measurements (2.5 MeV He+ ions) along major axial directions ([100], [110] and [111] and detailed scans across the axes were used to determine the lattice location of the implanted dopants after annealing. It was determined that, in the dose range investigated, 98–99% of the As occupy substitutional sites. Antimony doses less than 1.5×1016/cm2 yield similar results. Electrical measurements of the number of electrically active dopants support the high substitutional fractions observed by the ion channeling‐backscattering measurements. Also reported are channeling results ...

Phase transformations and transitions in relaxed optics and its possible applications

Abstract: The questions of the formation and modeling of phase transformations and transitions in the of relaxed optics are discussed. An influence of basic parameters of laser irradiation on the phasepsilas transformations in irradiated materials is analyzed. The problems of the creation of various structures are represented as phasepsilas transformations. Types of possible phase transformations are discussed. Problems of stability and applications proper phases are discussed too.

Lessons learned: the laser from theory to practice

Abstract: In September 1959, Theodore Maiman attended the first International Quantum Electronics Conference to present a paper describing an exceptionally compact microwave-emitting ruby maser he had developed at the Hughes Research Laboratories. On May 16, 1960 he succeeded in demonstrating the first working laser, also using ruby, a historic breakthrough that stunned others trying to develop a working laser. Maiman's success, described in my book Beam: The Race to Make the Laser (Oxford, 2005) teaches some important lessons in taking on challenging optical tasks.

Nanopulsed laser modification of Ge/Si heterostructures

Abstract: Laser-induced phase transitions in a-Ge/Si heterostructures (amorphous Ge films on crystalline Si substrate) have been studied by optical diagnostics and numerical simulation methods. The samples were irradiated by (i) a ruby laser with pulse duration 80 ns (FWHM) and wavelength 694 nm and (ii) an ArF excimer laser (10 ns and 193 nm). Time resolved reflectivity measurements showed the discrepancy in dynamics of reflectivity of probing beam for different regimes of laser irradiation. This discrepancy can be explained by differing kinetics of solid-liquid phase transitions in Ge films: (i) intermediate crystallization or (ii) simultaneous solidification of molten Ge layer from the surface and from the substrate.

Comparison of effects of pulsed ruby laser and pulsed electron beam annealing of 75As+ implanted silicon

Abstract: Ion‐backscattering, ion‐channeling, and transmission electron microscopy (TEM) have been used to study a series of ion implanted silicon samples that have been annealed with either a pulsed laser or a pulsed electron beam. Single crystal [(001) orientation] silicon samples were implanted with either 35 or 100 keV 75As+ to a dose of ∠1×1016 As/cm2 and subsequently annealed with either a Q‐switched pulsed Ruby laser or the Spire Corporation SPI‐PULSE 5000 electron beam generator. A series of energy densities was used in both cases to optimize results. It was determined from Rutherford backscattering that the as‐implanted profiles have been redistributed in essentially the same manner for both types of anneals, and this indicates that melting and rapid recrystallization has occurred. For the 35 keV 75As+ implanted samples the two techniques produced equivalent anneals with no remaining damage as indicated by channeling and TEM. However, for the 100 keV implants the anneal was not uniform across the sample in the electron beam case and the channeling minimum yields for the major axes ([110], [111], and [100]) were higher than the laser annealed results. In both cases, however, the As substitutionality (97–99%) and minimum yields are better than results obtained from conventional thermal annealing.Ion‐backscattering, ion‐channeling, and transmission electron microscopy (TEM) have been used to study a series of ion implanted silicon samples that have been annealed with either a pulsed laser or a pulsed electron beam. Single crystal [(001) orientation] silicon samples were implanted with either 35 or 100 keV 75As+ to a dose of ∠1×1016 As/cm2 and subsequently annealed with either a Q‐switched pulsed Ruby laser or the Spire Corporation SPI‐PULSE 5000 electron beam generator. A series of energy densities was used in both cases to optimize results. It was determined from Rutherford backscattering that the as‐implanted profiles have been redistributed in essentially the same manner for both types of anneals, and this indicates that melting and rapid recrystallization has occurred. For the 35 keV 75As+ implanted samples the two techniques produced equivalent anneals with no remaining damage as indicated by channeling and TEM. However, for the 100 keV implants the anneal was not uniform across the sample in...

Laser‐annealing of Te ion implanted GaAs

Abstract: 70 keV Te was implanted in GaAs at temperatures of 300 and 573 K to a dose ranging from 2.5×1013 to 8×1015/cm2, and laser‐annealing effects by a Q‐switched ruby laser were investigated by means of RBS (He‐ion channeling and backscattering technique), Hall effect, C‐V and DLTS (deep level transient spectroscopy) measurements. It was found that damages are annealed at the laser energy above 0.2 J/cm2 and that visible damages are produced at the surface at the laser energy above ∠0.8 J/cm2. Scattering yield indicates high substitutionality of the implanted ions irrespective of the implantation temperature. It was also found from RBS, CV and DLTs measurements that the effect of the surface decomposition is not significant. For annealing at ∠0.64J/cm2, carrier density of 1.6×1014/cm2 and mobility of 729 cm2/vsec were obtained for the implantation at 2×1015/cm2.

Annealing behavior of phosphorus implanted silicon irradiated by several lasers of different wavelength

Abstract: Annealing behavior of ion implanted Si substrates, after irradiation with CO2, Nd;YAG and Ruby lasers, is compared. The effect of substrate carrier concentration, damage degree and SiO2 films on Si surfaces on laser annealing behavior is clarified for each wavelength. Cracking of SiO2 films during Ruby laser irradiation is also observed and investigated.

Laser annealing of ion‐implanted GaAs

Abstract: Ion‐implanted GaAs layers annealed by a Q‐switched ruby laser have been examined by ellipsometry and Hall measurements. The extinction coefficient is shown to be a function of implant fluence for 120KeV Mg ion implants. Depth profile of the implant damage (via the extinction coefficient) shows the damage peak position relative to the LSS peak to be fluence dependent. Effects of laser anneal are evaluated from extinction coefficient measurements as a function of depth into the substrate. depth profile data are also given for C, Te, and Ge implants. Finally, surface extinction coefficient and sheet resistivity measuremenmts are given as a function of incident laser energy for 120KeV Mg implants with 1015/cm2 fluence. The extinction coefficient shows a minimum for a laser energy density of about .2 J/cm2 and increases thereafter. The sheet resistivity which decreases at about .28 J/cm2 and is 750Ω/⧠ at .35 J/cm2, continues to decreases with increasing laser energy.

Ruby laser induced breakdown of argon

Abstract: The physical processes leading to laser induced breakdown of argon are theoretically studied under the action of ruby laser light. A simple model of the argon atom is used. We adopt a previously developed model which was applied successfully to He breakdown. This model is modified by allowing the momentum transfer collision frequency (MTCF) νm(e) to depend on the electron energy. Good agreement is obtained between the calculated thresholds and the experimental ones. Recombination losses are introduced at higher pressures thus giving agreement over the whole pressure range.

Laser annealing of ion implanted GaAs

Abstract: Laser annealing of GaAs implanted at room temperature with 1.1015 or 5.1015 ions/cm2 of Te+, Se+, Sn+ and Ge+ ions has been studied. Depending on the dose, a single pulse from a Q‐switched ruby laser produced, in general, electron concentrations in excess of 1.1019 cm−3 for both coated and non‐coated samples. However, mobility values were low, indicative of the presence of a large concentration of ionised impurities. Significant indiffusion of Te nd Sn atoms was observed following laser irradiation.

Influence of pulsed laser annealing on the properties of Ge quantum dots in Si matrix

Abstract: The laser annealing of Ge/Si heterostructures with Ge quantum dots (QD's) embedded on the depth of 0.15 and 0.3 μm has been studied. The samples were irradiated by 80-nanosecond ruby laser pulses. Irradiation energy density was close to the melting threshold of Si surface. The nanocluster structure was analyzed by Raman spectroscopy. Changes in composition of QD's were observed for both types of samples. The decrease in dispersion of nanocluster sizes after laser irradiation was obtained for samples with QD's embedded on 0.3 μm depth. The numerical simulations on the basis of Stefan problem showed that the maximum temperatures on the depth of QD's bedding differ by ~ 100 K. This difference is likely to lead to different effects of laser annealing of heterostructures with QD's.

An introduction to laser endosurgery

Abstract: PLEASE NOTE THAT A MORE RECENT EDITION OF THIS TITLE IS AVAILABLE IN THE LIBRARYThe term 'laser' is actually an acronym, standing for Light Amplification by the Stimulated Emission of Radiation. The first workable experimental laser, a pulsed ruby laser, was developed in 1960 by Theodore Maiman. A basic knowledge of optical laser physics is useful in understanding the clinical applications of laser energy. This chapter provides a brief introduction to laser physics relevant to veterinary practice. The most commonly used laser in veterinary medicine is the carbon dioxide laser. These efficient, economical and highly effective lasers are excellent for general surgical use. However, the underlying physics of these lasers means that their use in endoscopic applications is limited. This chapter discusses Instrumentation; Mass resection; and Transurethral laser lithotripsy.

Photoluminescence of surface layers of CdTe when nanopulse laser radiation acts on them

Abstract: This paper discusses the dynamics of photoluminescence excited in CdTe when a pulsed(τ=80ns) ruby laser acts on it, modifying a submicron surface layer. The dependences of the maximum photoluminescence intensity on the irradiation-energy density E are obtained for single, double, and triple laser pulses. The dependences thus established are explained by the influence of competing factors: the increase of the photoexcitation level with increasing E, and the temperature quenching of the photoluminescence. A photoluminescence-increase effect for energy densities above the surface-melting threshold of the semiconductor is detected.

Nonlinear Optics of Photonic Crystals

Abstract: Nonlinear effects--photonic flame effect (PFE), stimulated globular scattering (SGS) and stimulated Raman scattering (SRS)--have been investigated in photonic crystals (synthetic opal matrices and nanocomposites on their base) under ruby laser excitation.

Holographic metrology for study and evaluation of vibration in complex structures

Abstract: Holographic interferometry has been applied to in situ measurements of vibration fields of large diameter conduits undergoing unsteady internal excitations. The ambient conditions under which the measurements were carried out were extremely difficult. The measurements, covering an area of several square meters with each holographic recording, were performed using a portable one joule pulsed ruby laser system capable of producing two sequential Q-switched pulses each with duration of ∼25 ns with a variable pulse separation between 10 and 800 μs. The entire assembly of laser and holographic camera was constructed as a single unit incorporating an internal reference beam; the reference beam included a mirror with the facility to make an angular tilt between the two laser pulses with the objective of providing a facility to obtain information relating to the phase of antinodes within the recorded area of the hologram.