Interferência de Múltiplas OndasO interferômetro de Fabry-Perot

Um aparato muito importante que utiliza esses princípos é o interferômetro deFabry-Perot

Basta fazer |h| = |r | e ' = k2d = 2⇡⌫/ (c/2d)

Túlio Brito Brasil (IFUSP/LMCAL) Introdução a Ótica Supervisor: Adriano M. Alencar 29 / 32

Introdução à Óptica (4300327)

Prof. Adriano Mesquita Alencar Dep. Física Geral

Instituto de Física da USP

Interferometria

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Atomic Force Microscopy

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Atomic Force MicroscopyRevealing the hidden atom in graphite by low-temperature atomic force microscopy

904 A Bergmann et al

Figure 2. Fabry–Perot interferometer.

is used for engaging the cantilever tip. This component is not essential; however, we found itto be a very helpful tool of high educational value (see section 2.3). The hardware-to-softwareinterface is realized by a customary analogue-to-digital converter.

Our experience with visiting secondary-school students has shown that this simpleoperating principle can easily be understood. Using a constant height mode instead of themore complex constant force mode makes the setup more transparent and less expensive sinceadditional feedback control systems are not needed.

2.2. The AFM setup in detail

Figure 3 shows our AFM setup. The positioning unit consists of a Thorlabs NanoMax-TSpiezo stage (1) with additional differential drives for coarse positioning (2). With a homemadestage attachment (3), it is possible to rotate the sample and compensate for sample tilts. Thisis very useful and convenient, but not essential or necessary for operation.

The optical single mode fibre (4) is positioned above the cantilever via a six-axis kinematicmount (5), so that optimal adjustment of the fibre is possible. The fibre is coupled to a diodelaser system which provides a single mode 635 nm, 2.5 mW laser beam for the interferometerfunction. The cantilever is placed on a simple cantilever holder (6) which is attached to anadditional one-axis piezo stage (7) that can be oscillated via a conventional frequency generator.In this way, the engaging of the tip can be performed manually (see section 2.3). Both thelaser system and the frequency generator are not shown in figure 3. The interference signal,i.e. the light intensity which represents the cantilever deflection, is detected by a ThorlabsPDA100A-EC Si photo diode detector (not shown either). The detector converts the intensity

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Atomic Force MicroscopyInterferência de Múltiplas OndasO interferômetro de Fabry-Perot

Um aparato muito importante que utiliza esses princípos é o interferômetro deFabry-Perot

Basta fazer |h| = |r | e ' = k2d = 2⇡⌫/ (c/2d)

Túlio Brito Brasil (IFUSP/LMCAL) Introdução a Ótica Supervisor: Adriano M. Alencar 29 / 32

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All AFMs have a microfabricated probe tip, mounted on a cantilever (figure 2). The cantilever can bend due to local steps on the surface (figure 3, left). A laserbeam and sensor register the cantilever deflections, giving the machine a high sensitivity to local surface variations. A positioning stage controls the movements of the sample in all directions. !In a metrological AFM all motions are registered by three orthogonally placed interferometers (figure 3, right). This property offers the machine its high accuracy. Errors can be limited to a few nanometres.