Abstract

Collagen is an abundant constituent of several types of biological tissue. It has been previously shown [l,2] that collagen-rich tissue pumped by short 1064nm laser pulses emits 532nm radiation. In the present work, this phenomenon of optical frequency-doubling is further investigated in pure type I collagen over a broad spectral range of pump wavelengths in the nanosecond pulse regime, obtained from a tunable Ti:Sapphire gain-switched laser at fluences on the order of several tens of MW/cm². Monochromatic output signal in each case was unambiguously detectable at half the fundamental near-infrared laser wavelength, the latter spanning the 760 to 1070 nm spectral range Furthermore, optical third harmonic generation 1064 → 355nm has been demonstrated in type I collagen using nanosecond Q-switched Nd:YAG laser pulses.

© 2000 IEEE