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

Mandelis, Andreas; Vanniasinkam, J.

doi:10.1063/1.363685

Cited by 12 publications

(16 citation statements)

References 22 publications

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“…As discussed in more detail elsewhere [17], [18], the PTR technique has the ability to monitor nonradiative processes occurring in the bulk and surface simultaneously. By detecting the IR emission from a laser material at very short times after pulse cutoff, one can characterize the laser material surface.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

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Diagnostics of nonradiative defects in the bulk and surface of Brewster-cut Ti:sapphire laser materials using photothermal radiometry

Vanniasinkam

Munidasa

Othonos

et al. 1997

IEEE J. Quantum Electron.

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The understanding of the problem of nonradiative energy conversion in solid-state laser materials is a key factor in improving the overall efficiency of solid-state lasers. Furthermore, the reduction of the heat generated in an optically pumped laser crystal can lead to several new applications of solid-state lasers, especially in the high-power region. To improve the quality of grown crystals, laser crystal growers require accurate techniques to perform the quality control that is so vital to improving the growth process.Using a time-domain approach and a time-domain theoretical treatment of the IR radiative emission signal, it was determined that one may probe nonradiative surface and bulk processes by monitoring different time ranges. Our results show that photothermal radiometry can be used as a single-ended technique to evaluate both the bulk and surface nonradiative energy conversion rates in a solid-state laser material. This technique was compared to the standard laser cavity technique and it was concluded that photothermal radiometry can provide additional information to the standard technique by identifying the sources of heat generation as either surface-or bulk-originating.

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Section: Theoretical Backgroundmentioning

confidence: 99%

“…Since this approach calls for time-domain detection, a theoretical model of the timedependent IR emission from a crystal in response to a laser pulse was developed. The details of this treatment are given elsewhere [17], [18]. However, the final expressions for the early-time and late-time IR emission are shown below.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Diagnostics of nonradiative defects in the bulk and surface of Brewster-cut Ti:sapphire laser materials using photothermal radiometry

Vanniasinkam

Munidasa

Othonos

et al. 1997

IEEE J. Quantum Electron.

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“…[1][2][3] The basis of photothermal spectroscopy is a photo-induced change in the thermal state of the sample. The advantage of the photothermal technique is that it can be used to investigate the optical properties of materials that are unsuitable with traditional spectrophotometry.…”

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confidence: 99%

Effect of the Excitation Source on the Quantum-Yield Measurements of Rhodamine B Laser Dye Studied Using Thermal-Lens Technique

Bindhu

Harilal

2001

ANAL. SCI.

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Photothermal spectroscopy is a group of highly sensitive methods used to measure the optical absorption and thermal characteristics of a sample. [1][2][3] The basis of photothermal spectroscopy is a photo-induced change in the thermal state of the sample. The advantage of the photothermal technique is that it can be used to investigate the optical properties of materials that are unsuitable with traditional spectrophotometry. In fact, both thermal and fluorescence spectroscopy are complementary: thermal spectroscopy measures the photon energy, which has been converted to heat, while fluorescence spectroscopy observes re-emitted photons. When a medium is illuminated with laser radiation, some of the incident energy is absorbed by the molecules in the ground state, and becoming excited to higher energy states in the process. Following the absorption of a photon, any excess energy of a molecule can be dissipated in many ways.When the decay involves a radiationless process, localized temperature increases are produced, leading to heating of the sample. The thermal fluctuations produced by nonradiative relaxations may be probed optically, since the resulting density change also produces a change in the refractive index. Specifically, the transient refractive index forms an effective lens, which diverges the light as it passes through a sample. This phenomenon is called thermal lensing, and provides a nice example of laser spectroscopy.The fluorescence quantum yield (Qf), one of the key photophysical quantities, is a measure of the rate of nonradiative transitions that compete with the emission of light. The absolute values of Qf of organic laser dyes are practically important, because they are necessary to calculate thresholds for laser action. 4 Measurements based on photothermal effects are capable of giving absolute fluorescence yields of highly fluorescent solutions with high accuracy and reproducibility. In order to evaluate the absolute fluorescence efficiency, we must consider both radiative and nonradiative processes taking place in the medium. Because the contribution from nonradiative processes is not directly measurable using the traditional optical detection methods, thermo-optic techniques, such as photoacoustic (PA) and thermal lens (TL) spectroscopic methods, have been adopted for this purpose. 5,6 In this present study, the sensitivity and viability of photothermal lensing technique were exploited to determine the absolute fluorescence quantum yield of Rhodamine B (RhB) laser dye. The Qf values were found to be strongly influenced by different parameters, like environmental effects, concentration of the dye solution and type of excitation (cw or pulsed) source used for the thermal lens measurements. ExperimentalDetails of the experimental set up used for the cw thermal lens 7 and pulsed thermal lens 8 are given elsewhere. For a transient thermal lens, 532 nm radiation from a frequency-doubled Qswitched Nd:YAG laser (FWHM 9 ns) was used as the pump source to generate a thermal lens in the medium. A 632...

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“…The probe beam was provided by a cw He-Ne laser at 632. 8 nm. An open jet of N 2 gas seeded with 0.53% NO 2 was used for the medium.…”

Section: Methodsmentioning

confidence: 99%

“…Mandelis and Vanniasinkam have developed a complicated transient fourlevel model to treat the dynamics of solid-state laser materials. 8 Repond and Sigrist 9 have considered the saturation effect in photoacoustic spectroscopy. Poston and Harris have discussed the effect of saturation in connection with the determination of relaxation kinetics of the excited states and measurements of optical cross sections in benzophenone using the photothermal technique, 10 and Georges et al 11 have considered saturation effects in Rhodamine 6G dye.…”

Section: Introductionmentioning

confidence: 99%

Effect of optical saturation on pulsed photothermal deflection signals in flowing media

Gupta

2000

Journal of Applied Physics

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

Cited by 12 publications

References 22 publications

Diagnostics of nonradiative defects in the bulk and surface of Brewster-cut Ti:sapphire laser materials using photothermal radiometry

Diagnostics of nonradiative defects in the bulk and surface of Brewster-cut Ti:sapphire laser materials using photothermal radiometry

Effect of the Excitation Source on the Quantum-Yield Measurements of Rhodamine B Laser Dye Studied Using Thermal-Lens Technique

Effect of optical saturation on pulsed photothermal deflection signals in flowing media

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