Showing papers on "Ruby laser published in 1981"

Orientation and velocity dependence of solute trapping in Si

Abstract: Interface segregation coefficients have been measured for Bi in Si for melt growth as a function of velocity for (111) and (100) crystals. Surface layers were melted by ruby laser irradiation and liquid‐solid interface velocities varied from 0.8 to 5 m/s by changing Si substrate temperatures or laser pulse length. Segregation coefficients are strongly dependent on velocity and orientation in this range.

Low energy laser initiation of single crystals of β-lead azide

Abstract: Unfocused low energy Q-switched and non-Q-switched ruby laser irradiation of individual single crystals ofβ-lead azide of size 40μm×200μm×10mm has been studied using high-speed photography. It was found that the initiation of fast reaction occurs at isolated sites which are probably defects and act as absorption centres in the dielectric which is otherwise transparent to the ruby wavelength of 694.3 nm. It has also been shown that it is the power and not the energy of the incident beam that controls the initiation under these low energy irradiation conditions. Finally, the variation of the time delay to initiation with the incident laser energy suggests a thermal mechanism of initiation.

Versatile high-power single-longitudinal-mode pulsed dye laser

Abstract: A versatile high-spectral-energy density dye laser suitable for lidar applications and high-resolution spectroscopy is reported. The dye laser includes an oscillator and preamplifier and two amplifier stages. With transverse pumping by the second harmonic of a Nd:YAG laser, an efficiency of 55% was achieved at 589 nm, providing 165 mJ in a single-longitudinal mode. Second harmonic generation results in a dye laser-to-UV conversion efficiency of 33%. Optimization of dye solutions covering the 565–880-nm range is presented. The laser was also pumped with a ruby laser, producing an output energy of 400 mJ at 770 nm.

cw CO2 and ruby laser annealing of ion‐implanted Hg1−xCdx Te

Abstract: The effects of cw CO2 and Q‐switched ruby laser beam irradiation on donor (B, In) and acceptor (P) ion‐implanted Hg1−xCdx Te (x = 0.2, 0.3) are reported. Rutherford backscattering and particle induced x‐ray emission measurements for channeled and nonchanneled particles were used to investigate the crystal quality and its composition near the surface. It is shown that annealing by cw CO2 laser irradiation (120 W/cm2, 0.2 s) results in good crystal regrowth. Irradiation by light from pulsed ruby lasers (0.15 J/cm2, 50 ns) even though to a certain extent does anneal the damage, is accompanied by the dislodging of Hg atoms from the near‐surface region. The present results thus explain our findings that electrical activation of donor and acceptor implants in HgCdTe can be achieved by cw CO2 laser annealing, but not by pulsed ruby laser irradiations.

Laser‐induced diffusion by irradiation of silicon dipped into an organic solution of the dopant

Abstract: A new method for preparation of p‐n junctions is presented. It consists in dipping the silicon to be doped into an organic liquid containing the dopant and irradiating its surface through the liquid with a high‐energy pulsed ruby laser. It is shown that by this treatment the dopant is driven into the crystal and that abrupt junctions with high doping levels can be realized. Using this simple technique, solar cells with AM1 efficiencies above 13% can be prepared.

Lack of importance of ambient gases on picosecond laser‐induced phase transitions of silicon

Abstract: A 10‐nsec pulsed ruby laser was used to prepare atomically clean silicon surfaces in UHV. With picosecond Nd:YAG laser pulses at 532 amd 266 nm, the amorphous patterns formed on the atomically clean silicon surfaces in UHV were compared with those formed in air and other ambient conditions. Results show that the picosecond laser‐induced phase transition of silicon does not depend on the ambient conditions or on the native surface oxide layer of silicon.

Oriented Crystal Growth of Si on SiO2Patterns by Pulse Ruby Laser Annealing

Abstract: Poly-Si films 200–600 nm thick deposited on (100) Si substrates having SiO2 stripe patterns have been transformed by Q-switched pulse ruby laser irradiation with energy densities between 1.0 and 2.0 J/cm2 into single crystals on the SiO2 patterns as well as on the Si. The regrowth of poly-Si on SiO2 starts laterally from regrown poly-Si on Si just after or during the vertical growth of poly-Si on Si by liquid phase epitaxy. Such lateral growth of poly-Si on SiO2 makes single crystal Si film formation possible on entire SiO2 patterns up to 4 µm wide under appropriate laser power and poly-Si thickness conditions. However, straight stacking faults in the direction remain in Si films grown on SiO2, although dislocations generated in the Si regrown on Si escape to the sample surface along the inclined plane of the SiO2 window edges.

Rare-earth plasma light source for VUV applications

Abstract: A compact versatile light source for producing VUV radiation from laser produced plasmas is described Measurements of the spectral irradiance from CO(2) laser-produced plasmas on targets of gadolinium and ytterbium in the 115-220-nm range are given, and a comparison is made with analogous results obtained using a ruby laser

Laser annealed Ta/Ge and Ni/Ge ohmic contacts to GaAs

Abstract: Refractory metal ohmic contacts to n-type GaAs have been developed using epitaxial Ge films and pulsed laser annealing. Laser annealing was carried out with a 22 ns pulse from a Q-switched ruby laser operating in the TEM 00 mode. The specific contact resistivity of the contacts Ta/Ge and Ni/Ge on 2 × 1017cm-3dopes GaAs exhibited sharp minima as a function of laser energy density at 1 × 10-6Ω-cm2and 2 × 10-6Ω-cm2, respectively, which occurred near the melting point of the layered contacts. Auger electron sputter profiles revealed Ge migration into the GaAs surface after laser annealing at sufficient energy density to form ohmic contact. The contacts have applications to high temperature devices and to devices which experience high channel or contact temperatures, such as power FETs and TEDs.

Time-resolved reflectivity during pulsed-laser irradiation of GaAs

Abstract: The first comparison of time‐resolved reflectivity (TRR) signatures for crystalline and ion implantation amorphized GaAs, during pulsed ruby laser irradiation, is reported. The inferred durations of surface melting are strikingly different for the crystalline and ion‐implanted cases. The measurements are in good agreement with the results of thermal melting model calculations for the crystalline case.

High‐intensity narrow light pulse produced by self‐focusing in laser spark

Abstract: The shape of the laser light pulse transmitted through the spark produced in air by the same light pulse is investigated. A single‐mode and single‐frequency ruby laser is used. A narrow spike, overriding the amplitude of the original light pulse, is observed in the transmitted light. The spike is explained as the result of self‐focusing taking place in the plasma. The amplitude and the time of the appearance of the spike, i.e., of the self‐focused pulse, is investigated independently of the different experimental parameters. The light scattered by the spark is also observed; furthermore, clear experimental evidence of the self‐focusing taking place during the cascade ionization process is presented.

Optical Excitation of Zeeman Coherence in Ruby

Abstract: Optically induced Zeeman coherences between various pairs of sublevels in the ground state 4 A 2 of a sample ruby (0.05 wt.%) were observed at room temperature by using impact excitation with circularly polarized resonant light pulses from a mode-locked ruby laser. The precessing magnetization associated with Zeeman coherence was detected magnetically in UHF, VHF and X-band microwave regions. The observed signals can be regarded as various types of ESR free induction decay signals and the decay times were of the order of nanosecond. Sustained precession signals were also observed. Characteristics of the signals were explained by numerical solutions of the Liouville equation.

Nonthermal acoustic signals from absorption of a cylindrical laser beam in water

Abstract: A Q‐switched ruby laser has been used to study the generation of acoustic signals in water. The presence of a predominant thermal expansion mechanism is verified by the dependence of the signal amplitude on the ambient temperature. Qualitative agreement with the theory for a cylindrical source is implied by the amplitude dependence on the distance from the source. An additional nonthermal mechanism is evident from the existence of a leading compression, tripolar pulse at 4°C, where the thermal signal must vanish. This pulse may indicate microbubble production by the laser beam.

Photoluminescence in laser-annealed neutron transmuted silicon: isoelectronic traps

Abstract: A Q-switched ruby laser is used to laser-anneal neutron transmuted silicon. The starting material was ultra high purity silicon. Approximately 2 × 1014 P/cm3 were created by the neutron transmutation doping. Photoluminescence measurements at T = 1.7, 4.2, and 20 K revealed long-lived sharp emission lines which were identified with an isoelectronic trap remaining in the laser-annealed material. P-related luminescence was not observed before or after laser annealing.

Luminescence and lasing of ZnSe single crystals subjected to one- and two-photon excitation

Abstract: A study was made of the luminescence and of the amplification, and generation of coherent radiation in ZnSe single crystals subjected to two-photon excitation by ruby laser radiation. Lasing appeared at pump power densities 10?20?MW/cm2, depending on the resonator length, and the emitted photon's energy was in the range 2.73?2.76 eV. The divergence of the output radiation was approximately 10?. An investigation of the luminescence spectra obtained under one-photon excitation conditions together with the gain spectra indicated that the main mechanisms responsible for lasing were exciton?phonon and exciton?exciton interactions.

Pulsed laser annealing of selenium implanted InP

Abstract: Rutherford back-scattering, Hall effect and Nomarski interference microscopy have been used to study 200 keV selenium ions implanted into InP in the dose range 1*1014 to 1*1015 cm-2. Samples were irradiated with single pulses from a Q-switched ruby laser in the energy range 0.2 to 2.2 J cm-2. It was found that capless laser irradiation does not allow complex recrystallisation of damaged InP, and an energy density of 0.3 J cm-2 causes surface decomposition, thus producing indium-rich surface layers. To ensure that the measured electrical properties were due to the implanted atoms alone it was found necessary to thermally anneal samples at 4000DC for 5 min after the laser irradiation. The activity was 26% and the mobility of 300 cm2 V-1 s-1 for a dose of 1*1015 Se+ cm-2 irradiated at 0.5 J cm-2.

Change in Reflectivity of Metals under Intense Laser Radiation. Revision

Abstract: : The reflectance behavior of a target surface during laser irradiation determines the laser energy which is directly absorbed. Experimentally, the reflectance of a metal surface has been reported to undergo a sharp and substantial decrease during an intense laser pulse. Explanations have been offered based on an increase in electron-photon collision frequency as the temperature of the metal surface rises to the melting point of the metal. For high conductivity metals such as copper, we have shown that the temperature dependence of a Drude-type free-electron model can not explain the substantial reflectance changes reported. Three other classes of explanations have been proposed: (1) deformation of the metal surface, (2) plasma formation in the front of the target, or (3) a nonlinear process causing enhanced absorption within the metal. Specular and total reflectances of metal surfaces during ruby laser irradiation have been measured at the Polytechnic. The laser energy absorbed has been calculated and the temperature history of the metal surface determined using a one-dimensional heat-conduction approach. Reflectance and temperature histories have been related to permanent changes observed in the metal target surface. Only at temperatures significantly above the melting point of the metal does a substantial decrease in the total reflectance occur. (Author)

Real-time response of a rotating disk using image-derotated holographic interferometry

Abstract: A recently developed technique that shows great promise for studying the structural response of rotating objects is that of image-derotated holographic interferometry The technique consists of optically subtracting the rotational motion of a disk by passing the image of the rotating disk through a prism that is rotating at half the disk's angular velocity Heretofore, a pulsed ruby laser had to be used to record the rotating object's out-of-plane modes of vibration This study reports on the extension of the technique to the real-time analysis of rotating objects by replacing the pulsed ruby laser with an acousto-optically modulated argon laser Using the strobed argon laser in conjunction with the optical derotator, the rotating disk's normal displacement can be observed as it is being excited in real-time This technique offers the distinct advantage of being able to observe the rotating disk's structural response over a wide range of pulse frequencies at any point in the disk's cycle of revolution

Anomalous Residual-Stress in Pulsed-Laser-Annealed Silicon-on-Sapphire Revealed by Raman Scattering

Abstract: Raman scattering measurements have been made in silicon-on-sapphire (SOS) annealed by irradiation of Q-switched ruby laser light. It is found that Raman signals from the optic mode show downward shifts of 4 to 5.5 cm-1 compared with the Raman shift in unstressed single crystal silicon, and that large tensile stress exists reaching 10–13.7 kbar in the recrystallized SOS. The origin of this anomalous stress is discussed on the basis of the laser annealing models that have been proposed to date.

Welding with High Power Lasers

Abstract: Lasers date back to 1960(1) which earmarked the initial operation of a ruby laser. For the following years, average laser output power remained low and, as a result, the development of materials processing applications progressed slowly. An important commercial application evolved in 1965(2) when the Western Electric Company adapted a pulsed system for production drilling of diamond wire drawing dies. In this application the processing time for drilling of a die was reduced from 24 hours for conventional techniques to less than one hour with lasers. A variety of commercial drilling applications have since been developed; one of the most successful being laser drilling of cooling passages in gas turbine parts (2,3). The success of these initial production applications hinged on the laser’s ability to accurately deliver a precisely controlled amount of energy to a highly localized region of a workpiece.

Stimulated emission from (F2+)A color centers in an NaF crystal

Abstract: Lasing in (F2+)A centers was observed when an NaF crystal was pumped with ruby laser radiation. A tunable color-center laser was constructed and its parameters were found to be as follows: tuning range 0.95–1.3 μ, threshold 400 kW/cm2, efficiency 15%, output power 1 MW. It was found that the (F2+)A centers were highly stable at room temperature. A study was made of the conversion of these (F2+)A centers by the high-power pump radiation and the existence of a stable component of these centers was established.

Improvement of Crystalline Quality of SOS with Laser Irradiation Techniques

Abstract: The crystalline quality of silicon layers grown on sapphire substrates by vapor-phase epitaxial growth is improved by exposing the layers to multiple doses of laser irradiation of a suitable energy density. SOS wafers have been irradiated with 25 ns pulses from a Q-switched ruby laser. The samples have been analyzed by Hall mobility, defect density and channeling. The electron Hall mobilities of samples exposed 2–4 times at an energy density of 1.5 J/cm2 are twice those of as-grown SOS. Under the same conditions, etch pit density and stacking fault density decreased by a factor of 3–4 and 10, respectively.

High power laser optical isolator using NaCl

Abstract: A new optical isolator was constructed especially suitable for high power laser applications. The magneto-optic active material was a crystal of NaCl and the magnetic field was pulsed. An insertion loss of 1.4 dB and an isolation as high as 33 dB was achieved when tested with a high power ruby laser. The dispersion of the Verdet constant of NaCl in the wavelength region from 0.4680 to 0.6943 mu m was measured at room temperature.

The role of plasma diffusion in heat dissipation during laser annealing

Abstract: The role of the plasma contribution to the heat dissipation during laser annealing of monocrystalline silicon was investigated. The experiments were performed with a Q‐switched ruby laser with a pulse length of 25–30 nsec. It was found that for samples with larger values for the minority carrier diffusion length, the threshold energy for annealing was increased and the depth of melting was reduced. The experimental results were compared with a thermal model which takes into account the modification of the distribution of laser energy coupled to the lattice due to the diffusion of the minority carriers which occurs prior to recombination. It is concluded that, due to the significant reduction of the minority carrier diffusion length which occurs under the exteremely high generation rates achieved during laser annealing, the plasma diffusion does not dominate the thermal behavior. However, the effects of plasma diffusion can be observed experimentally and they should not be neglected in a completed description of the laser annealing process.

Defects and AlSb Precipitate Nucleation in Laser Irradiated Aluminum

Abstract: Lattice defects and precipitates induced in unimplanted and Sb-implanted single crystal Al by single pulse irradiation with a Q-switched ruby laser were studied using ion beam analysis and electron microscopy. The absorbed laser energy during irradiation is directly measured in these studies to allow precise numerical modeling of the melt times and temperature profiles. For unimplanted Al, slip deformation gives rise to increased channeled yields throughout the analyzed depth and occurs for energies well below the melt threshold energy of 3.5 J/cm/sup 2/. Slip deformation is also observed for irradiation energies above the melt threshold energy, and melting is accompanied by a discontinuous increase in the minimum channeling yield.