Prisms Littrow

The Littrow prism is also widely used. It is a 30° prism with a mirror back face the light passes through the prism to the mirror face and is reflected back through the prism, the total path being equal to a 60° prism. The prism mounting results in a fairly compact instrument (Section 17.7). 

Littrow prism A prism with a reflecting back surface. 

FIGURE 4-2. Schematic diagram of a Littrow prism spectrometer. 

Fig. 3.5 Experimental arrangement for intracavity Raman spectroscopy with an argon laser CM, multiple reflection four-mirror system for efficient collection of scattered light LM, laser-resonator mirror DP, Dove prism, which turns the image of the horizontal interaction plane by 90° in order to match it to the vertical entrance slit S of the spectrograph FPE, Fabry-Perot etalon to enforce single-mode operation of the argon laser LP, Littrow prism for line selection [315]...

Figure 4.4 Implementation of wavelength selection in a multi-line gas laser (e.g. Ar" laser) resonator, by insertion of a low-loss Littrow-prism reflector...

Fig. 5.27a-c. Line selection in an argon laser with a Brewster prism (a) or a Littrow prism reflector (b). Term diagram of laser transition in Ar" " (c)... 

In case of multiline lasers (e.g., argon or krypton lasers), line selection and mode selection can be simultaneously achieved by a combination of prism and Michelson interferometers. Figure 5.41 illustrates two possible realizations. The first replaces mirror M2 in Fig. 5.39 by a Littrow prism reflector (Fig. 5.41a). In Fig. 5.41b, the front surface of the prism acts as beam splitter, and the two coated back surfaces replace the mirrors M2 and M3 in Fig. 5.39. The incident wave is split into the... 

Two types of prisms, namely 60° Cornu quartz prism and 30° Littrow prism are usually employed in commercial instruments. The latter is preferred. Simple glass prisms are used for visible range. For ultraviolet region silica, fused silica or quartz prism are used. Flourlte is used in vacuum ultraviolet range. Ionic crystalline materials are used in the infrared region. Some examples are NaCl, KBr, CsBr, and the mixed crystalline material commonly called KRS-5. 

Commercial instruments frequently use a so-called Littrow mount. Here a Littrow prism with a 30° angle and one surface silvered, as shown in... 

Commercial instruments frequently use a so-called Littrow moimt. Here a Littrow prism with a 30° angle and one surface silvered, as shown in Fig. 6.20, is used for increased dispersion. Arrangements with lenses or mirrors can be used for coUimating the incoming light onto the prism and for focusing the refracted beams towards the photographic plate or the exit slit. 

Fig.4,26. (a) Michel son interferometer with optical delay line, allowing a large path difference between the two interfering beams, (b) Michel son interferometer with Littrow prism as preselector... 

F1q.6.3. (a) Line selection in a gas laser by use of a prism with refractive index n and prism angle 2cp where tan 2cp = 1/n. (b) Littrow prism reflector which combines line selector and end reflector... 

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