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Advances in broad bandwidth light sources for ultrahigh resolution optical coherence tomography
(2004)
Novel ultra-broad bandwidth light sources enabling unprecedented sub-2 pm axial resolution over the 400 nm-1700 nm wavelength range have been developed and evaluated with respect to their feasibility for clinical ultrahigh resolution optical coherence tomography (UHR OCT) applications. The state-of-the-art light sources described here include a compact Kerr lens mode locked Ti:sapphire laser (lambda(c) = 785 nm, Deltalambda = 260 nm, P-out = 50 mW) and different nonlinear fibre-based light sources with spectral bandwidths (at full width at half maximum) up to 350 nm at lambda(c) = 1130 nm and 470 nm at lambda(c) = 1375 run. In vitro UHR OCT imaging is demonstrated at multiple wavelengths in human cancer cells, animal ganglion cells as well as in neuropathologic and ophthalmic biopsies in order to compare and optimize UHR OCT image contrast, resolution and penetration depth
Metrological Applications
(2004)
A passively Q-switched laser with a nonlinear mirror on the basis of stimulated Brillouin scattering (SBS), generates bursts of pulses with a few 10 ns pulse duration and a separation between 20-90 mu s. Percussion drilling and trepanning are performed in different materials with 1 mm thickness. The optimum parameter set of these pulse trains with regard to the burr height and ablation rate is investigated. Differences in the processing results between single pulse and multi pulse structures are discussed. In addition the laser allowed for transiently mode locked operation. Results for mode locked and merely Q-switched operation were compared
A pulsed, diode-laser-pumped Nd:YAG master oscillator power amplifier (MOPA) in rod geometry, frequency stabilized with a modified Pound-Drever-Hall scheme is presented. The apparatus delivers 33-ns pulses with a maximum pulse energy of 0.5 J at 1064 nm. The system was set up in two different configurations for repetition rates of 100 or 250 Hz. The beam quality was measured to be 1.5 times the diffraction limit at a pulse energy of 405 mJ and a repetition rate of 100 Hz. At 250 Hz with the same pulse energy, the M-2 was better than 2.1. The radiation is frequency converted with an efficiency of 50% to 532 nm. This MOPA system will be the pump laser of transmitters for a variety of high-end, scanning lidar systems. (C) 2005 Optical Society of America
We present a flashlamp-pumped Nd: YAG laser simultaneously emitting pulse structures on microsecond, nanosecond and picosecond time scales. Within a microsecond flashlamp pump pulse a nonlinear reflector based on stimulated Brillouin scattering (SBS) generates several Q-switch pulses. The phase-conjugating effect of the SBS reflector provides a compensation of phase distortions generated inside the laser rod, resulting in transverse fundamental mode operation. Additional acousto-optic loss modulation inside the resonator leads to mode locking. As a result, each Q-switch pulse is subdivided into several picosecond pulses. Energies of up to 2 mJ for the mode-locked pulses with durations between 220 and 800 ps are demonstrated. The wide variability of the laser's temporal output parameters as well as its high beam quality make it a splendid tool for fundamental research in laser materials processing