Confocal configuration

Figure 2.4 Configurations for a Fabry-Perot optical cavity. The radii indicate the focal point of the mirrors. In (c) the hatched area indicates the beam shape in the confocal configuration (see text)...

Table 5.50 lists the main features of Raman microspectroscopy. Virtually any object which can be observed under a microscope can be analysed with Raman microscopy. Here, the usual constraints inherent in electron beam methods (vacuum, metallisation, etc.) are totally absent. Although micro-Raman spectrometers mainly use visible excitation, the confocal configuration almost eliminates fluorescence which falls outside of the focal volume. The focus area for visible lasers is <1 /xm, whereas the focus diameter for NIR lasers is 20 fim. 

Figure 7.5 Radial integration of the optical sensitivity for a model Schwarschild objective when used in a standard (single-aperture) configuration (solid curve for the encircle intensity) and for the dual-aperture confocal configuration (dashed curve). A wavelength of 6 pm and Schwarschild optic having NA = 0.65 were assumed.

In order to obtain a real confocal configuration, a very accurate optical alignment is required as well as a high degree of stability and reproducibility of the mechanical and optical alignment. 

Figure 9.8 shows optical images of a Au nanocone recorded with our PM-assisted optical microscope in confocal configuration using... 

Similar to PL shown in Figure 14.16, the EL from the 1122 LEDs should be polarized. Because InGaN is compressively strained, the transition between the conduction band and the heavy hole valence band is predominant in the EL, especially at a low driving current. Therefore, the EL should polarize perpendicular to the [0001] direction, that is, along the [1100] direction in the 1122 plane. To demonstrate this, polarization E L measurements on our LEDs were conducted with a driving current of 20 mA. To avoid the contribution of light scattered within the LED dies, a confocal configuration was adopted. 

Fig. 5.15. The spectra of a three layered sample as the sample is translated axially through the laser focus, (a) Confocal configuration (b) super-focal configuration. (Reproduced with permission from Ref. [49]. 1996 Society for Applied Spectroscopy.)...

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