Oxford Instruments Cypher SPM, Руководство пользователя

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Cypher SPM
User Guide
16
16 BlueDrive Photothermal Excitation
blueDrive is an optional accessory mounted onto the Cypher Chassis which focuses a blue laser
spot onto the cantilever. The blue laser provides an alternative drive mechanism to the standard
piezoacoustic drive mechanism used to excite the cantilever (a.k.a piezo drive).
16.1 The principle of photothermal excitation
In addition to the infrared detection laser (850 nm), a blue laser (405 nm) is focused on the base of
the cantilever, causing photothermal excitation: local heating of the cantilever leads to a thermal
stress that changes the cantilever deflection proportionally to laser power. High frequency mod-
ulation of the laser power up to 8 MHz allows the excitation of cantilevers of all sizes, as well as excit-
ation of higher eigenmodes.
The following image shows a schematic of photothermal excitation.
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