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  • 1
    Electronic Resource
    Electronic Resource
    Excited state absorption of Sm2+ in SrF2 and SrCl2 (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 6751-6756 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The excited state absorption spectrum of Sm2+ diluted as an impurity in the single crystal hosts SrF2 and SrCl2 has been observed. The absorption peaks associated with the 5D0(4f6) excited state were found to be displaced by approximately 3000 cm−1 from the absorption bands arising from the 7F0(4f6) ground state when the 5D0–7F0 energy was taken into account. The observed peak separation is ascribed to the 4f–5d exchange interaction. From the measured peak positions and band intensities, the exchange energy for the Sm2+ impurity in the two host crystals was determined to be about the same order of magnitude as that expected for the free ion. The implications of the properties of the excited state absorption bands for the performance of CaF2:Sm2+ and SrF2:Sm2+ lasers are considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454420
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  • 2
    Electronic Resource
    Electronic Resource
    Optical properties of Cr3+ in fluorite-structure hosts and in MgF*2 (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 3455-3461 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have examined the optical properties of Cr3+ in MgF2 and in the fluorite-structure hosts: CdF2, CaF2, SrF2, and BaF2. The properties of Cr3+ in MgF2 are similar to those observed for other fluoride crystals that have octahedral substitutional metal sites. Interestingly, Cr3+ is also found to be sixfold coordinated in the fluorite hosts, despite the fact that the metal sites of these crystal lattices are eightfold coordinated. The smaller ionic radius of Cr3+ compared to, say, Ca2+, undoubtedly results in considerable relaxation at the metal site. However, the crystal field stabilization energy present in the 4A2(d3) ground state also provides for the energetic preference of sixfold vs eightfold coordination. The similarity of the observed absorption spectra of Cr3+ in MgF2 and in fluorite give evidence that the ground state is octahedrally coordinated in all of these hosts. The reduction of this electronic stabilization energy in the 4T2(d3) excited state is considered to produce a configurational shift relative to the ground state. This shift may be the reason why Cr3+ luminesces effectively in MgF2 whereas it is largely quenched in the fluorite-structure materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452001
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  • 3
    Electronic Resource
    Electronic Resource
    Investigation of optical damage mechanisms in hafnia and silica thin films using pairs of subnanosecond laser pulses with variable time delay (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 1204-1208 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optical damage thresholds of submicron-thick, electron beam deposited HfO2 and SiO2 films on BK-7 substrates have been measured by monitoring the emission of neutral constituents during excitation with time-delayed pairs of 70-ps laser pulses at a wavelength of 1064 nm. The dependence of the optical damage threshold on time delay provides evidence of the optical damage mechanism. For SiO2, linear absorption is the mechanism for energy deposition into the films by the laser beams. The data for HfO2 are less definitive, although linear absorption is the most likely damage mechanism. The behavior of the single-layer films is compared to multilayer HfO2-SiO2 high-reflector coatings, for which a "conditioning'' effect causes an increased optical damage threshold due to multiple pulse laser excitation at fluences below the single-pulse optical damage threshold.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351288
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  • 4
    Electronic Resource
    Electronic Resource
    High-resolution multiphoton laser-induced fluorescence spectroscopy of zinc atoms ejected from laser-irradiated ZnS crystals (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 281-289 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Time-of-flight (TOF) measurements employing high-resolution multiphoton laser-induced fluorescence spectroscopy (LFS) have been used as a probe to determine the yield and velocity distributions of Zn atoms ejected from a ZnS single crystal under irradiation by 308-nm photons. For fluences between 20 and 80 mJ/cm2 (irradiated area 2 mm2), the velocity distributions could be fitted by Maxwell–Boltzmann distributions where the characteristic temperature increased from 2000 to 9000 K, respectively. The absolute neutral Zn yield also increased from 108 to 1012 atoms per pulse over this same fluence range. Plots of temperature (T) as a function of fluence (F) and yield as a function of 1/T and 1/F suggest thermal evaporation as the mechanism for the Zn emission.The results indicate that with increasing fluence a critical combination of particle density and laser intensity is reached for formation of a plasma which interacts with the surface to cause catastrophic failure. For consecutive laser shots at constant ablation laser fluences, a nearly exponential increase of the Zn particle density was observed, although the measured kinetic temperature remains approximately constant even beyond the onset of visible damage to the ZnS surface. Doppler-shift techniques have been combined with TOF measurements for the first time in order to separate prompt from delayed emission of ablated atoms as well as to probe possible molecular or cluster ejection and fragmentation. Evidence for the latter phenomena was obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343406
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  • 5
    Electronic Resource
    Electronic Resource
    Laser performance of LiSrAlF6:Cr3+ (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 1051-1056 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have lased the new material, LiSrAlF6:Cr3+ (Cr3+:LiSAF). The single crystals were grown by the horizontal zone melting technique. The spectroscopic properties of Cr3+:LiSAF are similar to those of other low-field Cr3+-doped systems, although the emission cross section is strongly π polarized and is also somewhat larger than has been measured for other fluoride hosts. The free-running lasing wavelength of Cr3+:LiSAF is 825 nm, and the tuning range extends from at least 780 to 920 nm. Using Kr laser pumping, we obtained slope efficiencies of 36% and 14% by utilizing output couplings of 4.8% and 0.8%, respectively. On the basis of these results, the extrapolated maximum efficiency of 53% is determined, to be compared to the quantum defect-limited value of 78%. It is concluded that a moderate level of excited state absorption (ESA) loss is responsible for the reduced efficiency of the Cr3+:LiSAF system. This contrasts with the related results previously obtained for LiCaAlF6:Cr3+, where it was concluded that the effects of ESA were negligible [IEEE J. Quantum Electron. QE-24, 2243 (1988)].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343491
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  • 6
    Electronic Resource
    Electronic Resource
    Investigation of laser-surface interactions and optical damage mechanisms using excitation by pairs of picosecond laser pulses (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 443-445 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is demonstrated that laser-surface interactions that cause optical surface damage of nominally transparent materials can be investigated by observing the effects of excitation by pairs of picosecond pulses separated by a variable time delay. Laser-induced emission of neutrals is used as the detection mechanism in the present experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103660
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  • 7
    Electronic Resource
    Electronic Resource
    Photoluminescence of oxidized silicon nanoclusters deposited on the basal plane of graphite (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 3111-3113 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Silicon (Si) nanoclusters, with an average size of 3–5 nm in diameter, have been deposited on the basal plane of highly oriented pyrolytic graphite in an ultrahigh vacuum chamber, and investigated by scanning tunneling microscopy. Clusters passivated in situ with hydrogen or oxygen showed no detectable visible photoluminescence (PL). Prolonged exposure of the clusters to ambient air, however, resulted in strong stable red to green-blue PL spectra. Further study of these clusters by x-ray photoelectron spectroscopy and Auger electron spectroscopy revealed the existence of only SiO2 for the prolonged air-exposed samples, and the existence of SiOx (x ranged from 0 to 2) for the in situ oxidized samples which did not exhibit any detectable visible PL. We believe that the observed visible PL originated from defects in SiO2. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112452
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  • 8
    Electronic Resource
    Electronic Resource
    Electron emission from insulator and semiconductor surfaces by multiphoton excitation below the optical damage threshold (1986)
    Springer
    Applied physics 39 (1986), S. 163-166 
    Details
    ISSN: 1432-0630
    Keywords: 79.40 ; 79.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Electron emission due to 1.06 and 0.35 μm laser excitation has been measured at several pulse lengths for a number of wide bandgap semiconductors and insulators. The dependence on fluence and wavelength is consistent with multiphoton excitation across the bandgap. The work functions of the materials investigated do not appear to influence the rate-limiting multiphoton excitation process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00620730
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  • 9
    Electronic Resource
    Electronic Resource
    Ground-state depleted solid-state lasers: principles, characteristics and scaling (1990)
    Springer
    Optical and quantum electronics 22 (1990), S. S1 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A novel class of rare-earth-doped solid-state lasers is described. The ground-state depleted laser is pumped by an intense (more than tens of kW cm−2) narrow-band (less than a few nm) laser source and is characterized by: (1) an unusually low laser ion doping density (5 to 10×1018ion cm−3), (2) an unusually large fractional excited population inversion density (4 to 8×1018 ion cm−3, or 〉75%), (3) a gain element that is optically thick at the pump wavelength and (4) a gain element that has a substantially uniform gain distribution due to a bleaching of the pump transition at the pump intensity utilized. These features enable efficient room-temperature operation of rare-earth-ion laser transitions terminating on the ground manifold. The relationships between laser parameters (cross-sections, saturation fluences and fluxes, bleaching wave velocities, etc.) are given and laser performance scaling relationships are presented and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02088996
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  • 10
    Electronic Resource
    Electronic Resource
    Flashlamp-pumped laser performance of LiCaAIF6:Cr3+ (1990)
    Springer
    Optical and quantum electronics 22 (1990), S. S259 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The results of flashlamp pumping of the LiCaAIF6:Cr3+ (Cr:LiCAF) laser crystal are reported. We have so far obtained slope efficiencies as high as 1.55% in a close-coupled, diffusely reflecting cavity. Based on the measured insertion loss of the presently available material, we predict that an efficiency of about 4% will be obtained when low-loss material becomes available. This extrapolated efficiency is comparable with the performance of a high-quality alexandrite laser rod in the same apparatus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02089014
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