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Mandelis, Andreas; Vanniasinkam, J.; Budhudu, S.; Othonos, Andreas; Kokta, Milan R.

doi:10.1103/physrevb.48.6808

Cited by 42 publications

(35 citation statements)

References 33 publications

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“…The surface nonradiative quantum efficiency NR (s) ϭ 1 assumed here is consistent with our earlier findings 9,11 in Ti:sapphire laser rods with polished surfaces. This value appears physically reasonable as the result of some degree of damage to the crystal incurred during the polishing process.…”

Section: ͑32͒supporting

confidence: 91%

“…A few theoretical treatments of photothermal effects as related to solid-state laser media have appeared, dealing with the effects of bounding surfaces 7 and of bulk-distributed optical absorption on the thermal profiles. 2, 6 With the optical quality of laser materials improving substantially in recent years, 9 photothermal transients from laser-irradiated laser media can be used as powerful diagnostic probes of the optical, thermal, and photonic quality of the medium. Unlike early laser materials, the high-crystal growth quality may no longer be the limiting factor in the optical behavior of manufactured laser rods.…”

Section: Introductionmentioning

confidence: 99%

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Theory of nonradiative decay dynamics in intensely pumped solid-state laser media via laser photothermal diagnostics

Mandelis

Vanniasinkam

1996

Journal of Applied Physics

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A rigorous analytical treatment of nonradiative deexcitation and thermal-conduction transient evolution in solid-state laser media, resulting from intense optical pumping with rectangular pulses from a time-gated laser source, is presented. This situation arises in rate-window photothermal detection from laser rods with bulk and surface absorptions, the latter being due to polishing during the manufacturing of the rod. Numerical simulations of the theory show that the surface nonradiative ͑optical-to-thermal͒ energy conversion term is likely to dominate even at absorptances on the order of 1%-2%. Therefore, polishing optimization appears to be necessary in order to minimize laser losses at the surfaces when laser rods are active in a resonator cavity. The present theory also provides physical insights into the very different nature of the bulk-and surface-originating heat-conduction transients, as well as on the profile of the superposition photothermal wave form and its dependence on the optical, thermal, and metastable-state relaxation parameters. As a prelude for input to the photothermal theory, a treatment of the excited-state dynamics of a typical laser manifold pumped by an intense laser beam, away from or near saturation, is developed, and the luminescence and photothermal energy source profiles are calculated analytically.

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Section: ͑32͒supporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Theory of nonradiative decay dynamics in intensely pumped solid-state laser media via laser photothermal diagnostics

Mandelis

Vanniasinkam

1996

Journal of Applied Physics

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“…An IBM PC collected data from both lock-in IP and Q channels. Since the aluminum foil is opaque, the PPE signal, under the assumption of one-dimensionality of the thermal-wave response of the cavity, can be expressed as [ 16,17 ] 2I°bg' (1) where…”

Section: Methodsmentioning

confidence: 99%

“…However, the recent development of a photopyroelectric (PPE) detector with a variable sample-to-source distance [ 16,17] has introduced the possibility of measuring thermal diffusivity by monitoring the spatial behavior of the thermal wave. Subsequently, a thermal-wave cavity was built, [ 18] and resonance-like extrema of the thermal wave were demonstrated in both lock-in in-phase and quadrature channels when the cavity length was varied.…”

Section: Introductionmentioning

confidence: 99%

Thermal-wave resonant-cavity measurements of the thermal diffusivity of air: A comparison between cavity-length and modulation-frequency scans

1996

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The application of a thermal-wave resonant cavity to thermal-diffusivity measurements of gases has been investigated. The cavity was constructed using a thin aluminum foil wall as the intensity-modulated laser-beam oscillator source opposite a pyroelectric polyvilidene fluoride wall acting as a signal transducer. Theoretically, cavity-length and modulation-frequency scans both produce resonance-like extrema in lock-in in-phase and quadrature curves. These extrema can be used to measure the thermal diffusivity of the gas within the cavity. It was found experimentally that one can obtain very accurate and reproducible measurements of the thermal diffusivity of the gas by using simple cavity-length scanning without any signal normalization procedure, rather than traditional modulation-frequency scanning normalized by the frequency-dependent transfer function of the instrumentation. By scanning the cavity length, the thermal diffusivity of room air at 299 K was measured with three-significant figure precision as 0.216_ 0.001 cm 2-s-1, with a standard deviation 0.5 %. Only two significant figure accuracy could be obtained by scanning the frequency: 0.22 __+ 0.03 cm 2. s-t, with a standard deviation of 14%. Cavity-length scanning consistently exhibited a much higher signal-to-noise ratio.

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“…Several methods have been used to measure , including pure optical measurements such as using integrating spheres, comparing the measured and radiative lifetime values of the investigated energy state and employing photothermal methods such as photoacoustic, photocalorimetry, photopyroelectric, and thermal lens ͑TL͒. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] Various methods provide good results but some of them require relatively complicated experimental setups, the need of absolute photodetector calibration, knowledge of absolute concentrations of impurity ions, and the availability of a suitable standard.…”

Section: Introductionmentioning

confidence: 99%

Normalized-lifetime thermal-lens method for the determination of luminescence quantum efficiency and thermo-optical coefficients: Application toNd3+-doped glasses

et al. 2006

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We present a new method based on thermal lens ͑TL͒ technique to determine the fluorescence quantum efficiency, , and thermo-optical coefficients of fluorescent materials. These parameters can be obtained from the linear dependence of the TL signal with the experimental lifetimes of a set of samples with different luminescent ion concentrations. The method was applied in Nd 3+ -doped materials ͑Q-98 Phosphate, fluorozirconate, and fluoroindate͒. The obtained values are in agreement with those determined by other approaches based on TL methods and the ratio between experimental and radiative lifetime values ͑Judd-Ofelt theory͒. The method hereafter presented is very simple and does not require comparison with a reference sample or the use of multiple excitation wavelengths. In addition, the nature of concentration quenching taking into account the achieved and values and respective energy transfer microparameters, is discussed.

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Absolute nonradiative energy-conversion-efficiency spectra inTi3+:Al2

Cited by 42 publications

References 33 publications

Theory of nonradiative decay dynamics in intensely pumped solid-state laser media via laser photothermal diagnostics

Theory of nonradiative decay dynamics in intensely pumped solid-state laser media via laser photothermal diagnostics

Thermal-wave resonant-cavity measurements of the thermal diffusivity of air: A comparison between cavity-length and modulation-frequency scans

Normalized-lifetime thermal-lens method for the determination of luminescence quantum efficiency and thermo-optical coefficients: Application toNd3+-doped glasses

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