Absolute non-radiative energy conversion efficiency scanning imaging of growth defects in Ti3+: Al2O3 crystals using quadrature photopyroelectric detection

Deconvolution and measurement of bulk and surface optical absorptions in Ti:Al2O3 crystals using photopyroelectric interferometry

“…Photothermal ͑PT͒ and photoacoustic ͑PA͒ spectroscopic techniques have been used successfully in measurements of optical absorption coefficients and nonradiative quantum efficiencies for a variety of optical materials, including laser crystals. [1][2][3][4][5][6][7][8][9][10][11][12][13] Among the various embodiments of PA and PT techniques, photopyroelectric detection ͑PPE͒, as pointed out elsewhere, [1][2][3][4][10][11][12]14 has a certain number of advantages. A major advantage of PPE detection over other conventional PT techniques is the fact that one can measure directly and self-consistently both the optical absorption coefficient, ␤͑͒, and the nonradiative quantum efficiency, ͑͒.…”

“…A major advantage of PPE detection over other conventional PT techniques is the fact that one can measure directly and self-consistently both the optical absorption coefficient, ␤͑͒, and the nonradiative quantum efficiency, ͑͒. 2,3,12,15,16 Lock-in quadrature photopyroelectric spectroscopy ͑Q-PPES͒ was used in a novel noncontact experimental scheme to obtain high-resolution spectra of the nonradiative quantum efficiency of Ti:sapphire laser crystals with widely different figures of merit ͑FOM͒. 2 Using the same setup, opticalabsorption-coefficient spectra were obtained from the lock-in in-phase ͑IP͒ channel in a separate measurement, in the socalled ''purely optical transmission ͑OT͒ mode.''…”

“…The contributions from the surface and the bulk were thus separated from each other. It was shown, 3,11,12 however, that the sensitivity of conventional single-ended PPE measurements suffers from a large baseline signal, generated by the direct transmission to the detector surface of the incident radiation through the transparent sample under investigation. With regard to transparent materials, this large baseline signal, which appears in the lock-in IP channel, is much larger than that of the Q channel, by more than two orders of magnitude.…”