Abstract

There has been considerable interest in the development of fibre optic temperature probes for bio-medical applications. The dielectric property of the fibre optic probe is essential for some applications, e.g., the monitoring of the human body temperature during treatment employing rf or microwave heating and for use with C.T. scanners using large electro-magnetic fields. The potentially high measurement sensitivity of fibre optic probes can cater for the particular requirement to monitor slight body temperature variance and their small size and flexibility also make such probes valuable for bio-medical applications. An extensive review of fibre optic techniques for temperature measurement has been presented by one of the authors [1], and one of the more successful schemes is that based on fluorescence lifetime. Apart from the high measurement sensitivity achievable, the measurement of temperature using the fluorescence lifetime of appropriate materials has a significant advantage in that it is independent of an accurate measurement of light intensity. Therefore, the corresponding fibre optic probe can be free of the impact of fibre sterilising and bending, and be potentially robust enough for harsh day-to-day usage. An early proof-of-principle demonstration of a optical temperature probe using the fluorescence decay of ruby was presented by Sholes and Small [2] with a bulky optical configuration, and lately various probes using the fluorescence lifetime with a fibre optic configuration have been developed [3-7] together with the introducing of new signal processing schemes [7,8]. Herein, a highly sensitive fibre optic temperature probe based on the fluorescence lifetime of a newly developed laser material, 3+ CrsLiSAF (Cr -doped LiSrALF ) is presented over temperature range from 6 o o 10 c to 100 C. The material may be pumped with light from a solid state laser diode operating in the visible region.

© 1992 Optical Society of America