Numerical aperture dependence of damage and supercontinuum generation from femtosecond laser pulses in bulk fused silica
- Department of Physics and Division of Engineering and Applied Sciences, Harvard University, 9 Oxford Street, Cambridge, Massachusetts 02138 (United States)
Competing nonlinear optical effects are involved in the interaction of femtosecond laser pulses with transparent dielectrics: supercontinuum generation and multiphoton-induced bulk damage. We measured the threshold energy for supercontinuum generation and bulk damage in fused silica using numerical apertures (NAs) ranging from 0.01 to 0.65. The threshold for supercontinuum generation exhibits a minimum near 0.05 NA and increases quickly above 0.1 NA. For NAs greater than 0.25, we observe no supercontinuum generation. The extent of the blue broadening of the supercontinuum spectrum decreases significantly as the NA is increased from 0.01 to 0.08, showing that weak focusing is important for generating the broadest supercontinuum spectrum. Using a light-scattering technique to detect the onset of bulk damage, we confirmed bulk damage at all NAs studied. At a high NA, the damage threshold is well below the critical power for self-focusing.
- OSTI ID:
- 20861066
- Journal Information:
- Journal of the Optical Society of America. Part B, Optical Physics, Vol. 23, Issue 11; Other Information: DOI: 10.1364/JOSAB.23.002317; (c) 2006 Optical Society of America; Country of input: International Atomic Energy Agency (IAEA); ISSN 0740-3224
- Country of Publication:
- United States
- Language:
- English
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