Photopyroelectric deconvolution of bulk and surface optical-absorption and nonradiative energy conversion efficiency spectra in Ti:Al2O3 crystals

Abstract

The extension of an earlier monolithic photopyroelectric spectroscopic model [A. Mandelis et al., Phys. Rev. B 48, 6808 (1993)] to include surface and bulk optical absorptions and the subsequent optical-to-thermal (nonradiative) energy conversion efficiencies associated with these sites has allowed the self-consistent determination of visible spectra of these quantities, using a very sensitive noncontact experimental configuration to obtain in-phase and quadrature photopyroelectric spectra of Ti:sapphire crystals of two thicknesses and figures of merit.

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

“…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…”

“…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.…”

High-Precision and High-Resolution Measurements of Thermal Diffusivity and Infrared Emissivity of Water–Methanol Mixtures Using a Pyroelectric Thermal Wave Resonator Cavity: Frequency-Scan Approach

“…(3)) includes the thermal diffusivity α n of the n-th layer. Comparison of the simple thermal-wave model [16], which takes into account only conduction heat transfer in the cavity, with experimental results shows that the model is unable to describe the signals obtained from the cavity filled with water. To improve this model, we took into account radiation heat transfer inside the cavity.…”

Diffusive-to-ballistic transition of the modulated heat transport in a rarefied air chamber

“…In its simplest configuration, the TWRC consists of three parallel layers: the first one is a thin film called heater, which is heated up with a laser beam of modulated intensity; while the second one is a fluid sample supporting the propagation of the temperature oscillations induces by the heater towards the pyroelectric detector (third layer) that records the amplitude and phase delay of the thermal-wave signal, in the form of a voltage. These two signals have been theoretically modeled taking into account not only the pure heat diffusion, 15,16 but also the contribution of heat radiation from the heater to the detector. [17][18][19][20] Previous experimental works [22][23][24] (conductivity) of the air inside the TWRC increases (remains nearly constant) as the intra-cavity pressures reduces, as predicted by the kinetic theory of ideal gases.…”

“…[12][13][14][15][16][17][18][19][20][21][22][23][24][25] The thermal-wave resonant cavity (TWRC) has demonstrated to be a simple, reliable, and accurate technique to study the heat transport in a large variety of fluids. [12][13][14] This photothermal technique involves the use a lock-in amplifiers and filters that allow us measuring very low signals even in highly noisy environments.…”