Beam deflectors

For second harmonic generation (SHG), the tensor is y(2)(—2co co, co) (useful for frequency doubling and parametric down-conversion) while for the linear electrooptic or Pockels71 effect the tensor is y(2)(— co co, 0) (useful for Q-switching of lasers, for phase or amplitude modulators, and for beam deflectors) for optical rectification the tensor is y 2>(0 00, —co) for frequency mixing the tensor is y(2)(— co3 oolr co2) (useful for frequency up-converters, optical parametric oscillators, and spectroscopy). 

SIMS requires an ultra-high vacuum environment, similar to AES and XPS. The ultra-high vacuum environment ensures that trajectories of ions remain undisturbed during SIMS surface analysis. The SIMS vacuum chamber and pumping system is not much different from that for AES and XPS. Figure 8.5 illustrates common SIMS structure in a vacuum chamber in which there are two main components a primary ion system and a mass analyzer system. The primary ion system includes a primary ion source, a Wien filter and ion beam deflector. The mass analysis system includes a secondary ion extractor filter, mass analyzer and ion detector. 

A system generating a primary ion beam consists of three main parts ion source, ion filter and deflector as schematically illustrated in Figure 8.5. The ion source produces primary ions with a certain kinetic energy. The ion filter purifies the primary ions and rejects unwanted ions in the primary ion beam. The purified ions are condensed to a focused beam using an electromagnetic lens. The deflector makes the focused ion beam raster on the sample surface in two orthogonal directions its function is similar to the electron beam deflector in the scanning electron microscope (SEM). 

The primary ion beam etches a well defined crater in a sample by a beam deflector as illustrated in Figure 8.23. Ideally, only the secondary ions emitted from the crater bottom should be collected for depth profiling. However, secondary ions will be collected at the same time as when the primary ions etch the crater. Thus, the secondary ions from the crater walls may also contribute to the secondary ions in analysis. Such secondary ions from crater walls do not represent the true concentrations of elements at the crater bottom. To avoid this problem,... 

An electron beam is of much shorter wavelength than the radiation used in standard microlithography and, therefore, provides greater resolution possibilities. For resist exposure a beam of electrons can be used whose position is controlled by a computer-driven beam deflector, thus obviating the need for a mask. Both positive- and negative-working resists are used for electron beam lithography. 

We mentioned the MORE apparatus which offers some of the features of pulsed beam data collection for continuous beams. The acronym MORE stands for Muons On REquest. Its basic feature is a fast-switching electrostatic beam deflector (for surface muons only) which extracts one muon out of the beam and sends it towards a pSR spectrometer. After 10T i the system is ready for the next muon to be extracted. This ensrues that at any time only one muon is in the sample and the muon gate circuitry is not needed. Time resolution is not blurred by a finite pulse width when compared to a pulsed beam, but count rates are lower. The system runs parasitically on a beam line which delivers sruface muons to a conventional spectrometer when the beam deflector is off (which is most of the time). 

FIGURE 11 Optical interconnects (a) beam divider (3 dB if x=50), (b) beam deflector, (c) blazed grating, (d) array generator, (e) waveguide interconnect, and (f) substrate interconnect. 

A beam deflector is important in the field of laser printers. A rotating mirror is used now, but some kind of electro-optically controlled device is required to simplify the system. 

Figure 12.1 LC blazed-grating beam deflector by using a glass substrate with a sawtooth surface structure. PI polyimide ITO indium-tin-oxide PMMA poly(methyl-methacrylate).

X. Wang, D. Wilson, R. Muller, et al.. Liquid-crystal blazed-grating beam deflector, Appl. Opt. 39, 6545 (2000). 

FIGURE 8.6. Beam deflector [29] 1, glass prisms 2, film of nematic liquid crystal 3, transparent electrodes and 4, screen. 

Conventionally, electron-beam exposure is carried out using a pencil of focussed electrons to write the pattern using a beam deflector driven by a computer system. The beam in this case is scanned across the substrate to be exposed using either vector scan or raster scan methods (Fig. 7.16). Vector scanning writes patterns in a similar way to which shapes might be filled in with a bail-point pen whilst the raster uses a system similar to that of a television tube where the entire surface is scanned and the beam tinned on and off as necessary. Each method has advantages vector scan machines have to scan smaller areas but this is compromised by the need for a more sophisticated deflection system. The raster scan by contrast, whUst having to irradiate the entire substrate, can be operated at faster scan speeds. Normally the vector scan uses less exposure time when less than around one sixth of the area has to be exposed. 

If an ion-beam deflector electrode is placed in front of the collision cell in the second field-free region of a sector mass spectrometer (see Figure 1), then all mass-selected ions and their charged fragments may be deflected from the beam path, and only the neutral products from ion fragmentation... 

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