Characteristic research of the waveguide by nanosecond laser pulses on LiNbO3
2012
The damage threshold and morphology of optical material have been investigated by 800nm,
75MHz, 30fs laser pulses, in 40 magnification and 0.65 numerical aperture (NA) objective in the
Z-LiNbO 3 crystals. The influence of several experimental parameters, for example energy per
pulse, a ser scanning speed, or repeat time on writing quality and the characters of relative
microstructures has been analyzed and studied in theory. The damage structural change, from
small refractive index changes to micro explosion structure in LiNbO 3 induced by high intensity
nanosecond laser is studied. Nonlinear interactions of nanosecond laser and transparent material
are discussed.
The subsurface morphology of the processed structures inside the LiNbO 3 was obtained by a
Nikon optical microscope. Particularly, we find that the wider width of the buried channel with the
increase of energy per pluse, repeat time and the reduce of scanning speed. It was caused by the
avalanche ionization and multi-photon absorption of lithium on the processed area, and which is
also lead to the refractive index change rang by the writing conditions. The result shows that the
propagation of optical waveguide could achieve ideal effect when the energy per pluse is under
300mW, the scanning speed is from 0.05mm/s to 0.2mm/s, and the focus depth is from 350μm to
400μm.At last, in this approach, the insertion loss of 1×4 optical splitter is less than 1dB/cm.
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