Measurement of the effective optical path length of diffusing integrating cavities using time-resolved spectroscopy

Abstract

A method to measure the effective optical path length (EOPL) of a diffusing cavity using time-resolved spectroscopy is presented. A 710 nm short-pulsed laser was employed as the light source with a FWHM of 0.7 ns. From the temporal response curves, the time to establish a uniform optical field was obtained as approximately 4 ns for this cavity. Correspondingly, light was scattered 5-6 times by the inner coating. EOPLs with different port fractions were obtained by the selection of an appropriate initial time. Moreover, we verified a previously reported theoretical EOPL law using time-resolved spectroscopic results. This work provides a method to measure the EOPL of a diffusing cavity at different wavelengths.

Ratiometric pathlength calibration of integrating sphere-based absorption cells

“…8(b) are the same proportion of L foul as those in Fig. 7(b) are of Q(0), as expected from equation (17), therefore the same comments on errors apply.…”

“…This suggests that some of the errors in Φ 11 (0) and Φ 12 (0) were correlated and have cancelled out. Using these measurements, the value of L foul was estimated according to equation (17). The value of L cal was determined by measuring the gas absorption within the integrating sphere with no contamination and comparing this to the reference gas cell; this gave a value of L cal = 99.2 ± 0.4cm.…”

“…al. [17] have measured the temporal response of a laser pulse to calculate the mean pathlength of the photons from entrance aperture to detector. For a high reflectivity material newly developed by them, Cone et al measured a ringdown time of approximately 35ns for a 5cm diameter sphere, corresponding to a mean reflectivity of ρ=99.686% and an effective pathlength of 10m [18].…”

A New Insight into the Singlet Oxygen Mechanism for Photodynamic Therapy

“…To further verify the energy transfer between the S 1 and oxygen and determine the oxygen quenching rate of S 1 ( k Q ) in eq , the fluorescence dynamic process is considered, as in eq , τ normalF = 1 k normalF + k nF + k normalQ [ O 2 ] where τ F is the fluorescence lifetime of S 1 . Then k Q could be calculated by fitting the oxygen dependence of fluorescence lifetimes, as in eq , 1 τ normalF = k normalQ [ O 2 ] + k normalF + k nF + k ISC The fluorescence lifetimes of HMME under different oxygen concentrations were measured through the fluorescence dynamic curves, as shown in Figure (a), and the corresponding method and equipment has been added in the Supporting Information. The fluorescence decays exhibit intense oxygen-dependent behavior, which further verifies the energy transfer process from S 1 to oxygen, as we proposed above.…”

“…The fluorescence lifetimes of HMME under different oxygen concentrations were measured through the fluorescence dynamic curves, 30 as shown in Figure 4(a), and the corresponding method and equipment has been added in the Supporting Information. The fluorescence decays exhibit intense oxygen-dependent behavior, which further verifies the energy transfer process from S 1 to oxygen, as we proposed above.…”