Measurement of tissue absorption coefficients by use of interferometric photothermal spectroscopy

We describe a spectroscopic technique called interferometric photothermal s pectroscopy (IPTS) that can measure the absorption coefficient of pulsed la ser radiation in nonscattering tissue samples. The technique is suitable fo r measuring effective absorption coefficients from 10(3) to 10(5) cm(-1). I PTS is particularly attractive because it requires minimal disturbance of t he sample. These features indicate potential use for in vivo measurements o f tissue absorption coefficients. To validate the technique, the absorption coefficient of pulsed Q-switched Er:YSGG (2.79-mu m) radiation in pure wat er was measured to be 5200 (+/- 500) cm(-1) when IPTS was used, in agreemen t with other published values. IPTS was also used to measure the absorption coefficient of pulsed ArF excimer laser radiation (193 nm) in bovine corne al stroma (in vitro), giving a value of 1.9 (+/- 0.4) x 10(4) cm(-1). (C) 1 999 Optical Society of America. OCIS codes: 120.3180, 120.4290, 120.6810, 1 70.3660, 170.6930, 300.6430.