Spectral domain Optical Coherence Tomography using a microchip laser-pumped photonic crystal fiber supercontinuum source

Optical Coherence Tomography (OCT) is a well established biomedical imaging technique, which produces ultrahigh spatial resolution cross-sectional images of biological tissue in the range of a few millimeters. The axial resolution of OCT improves with a larger bandwidth optical source. Traditional OCT often uses a femtosecond laser as the broadband optical source. Recently, supercontinuum spectrum has been demonstrated by using the combination of femtosecond lasers and nonlinear effects of photonic crystal fiber. However, this source has fairly high cost.;This thesis investigates OCT using a more cost effective source based on a microchip laser-pumped photonic crystal fiber. The Q-switched Nd:YAG microchip laser produces 0.6 ns duration pulses at 1064 nm with 8 microJ of energy at a 6.6 kHz repetition rate. These pulses are sent through a photonic crystal fiber with a zero dispersion wavelength of 1040 nm. The generated supercontinuum pulses are coupled into a fiber-based spectral domain OCT system operating at a central wavelength of 800 nm. The axial scan rate is 6.6 kHz, where each scan is produced by a single supercontinuum pulse. Point spread function measurements show excellent resolution, but sensitivity is degraded by spectral fluctuations of individual supercontinuum pulses. Test images show less dynamic range compared to a Ti:Sapphire femtosecond laser based system. However, this supercontinuum source has potential for stroboscopic illumination in time-resolved low coherence interferometry.