Similarly, lasers that provide very rapid modulations could further reduce thermal diffusion lengths.
2.
The thermal diffusion length ( the distance the heat spreads ) is inversely proportional to the root of the modulation frequency.
3.
A typical parameter which governs the signal in this case is the " thermal diffusion length ", which depends on the material and the modulation frequency and ordinarily is in the order of several micrometers.
4.
Compared to earlier work, this approach improved spatial resolution because the use of short laser pulses reduced the duration of the thermal expansion pulse to the point that the thermal diffusion lengths can be on the scale of nanometres rather than microns.
5.
However, this mechanism can be excluded for two reasons; first, cantilever coatings have been stripped experimentally and no change in signal was observed; second, the calculated thermal diffusion length in SiNx and Si cantilevers at the SJEM working frequency ( typically 10 kHz ~ 100 kHz ) is small, much smaller than the length of the cantilever ( typically 100 um ).
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