In general, transmission gratings are used in the way shown in Fig. 11, with light entering at an angle perpendicular to the reverse side of the grating. In this case, *α* = 0 and so grating equation (8) gives the following:

Fig. 11 Transmission Grating

Light is refracted at the facet face of the grooves and by **Snell's Law** the following equations is given:

Here, *n* is the refractive index of resin and *θ*_{B} is the blaze angle. Combining equations (19) and (20) gives the following:

The reflective Littrow-configuration blaze wavelength, λ_{B(Litt)}, corresponding to the wavelength λ to be picked out with a high efficiency can be obtained by substituting *θ*_{B} into equation (11).

If *θ*_{B} + *β* ≥ 90°, however, diffracted light cannot be obtained. Also, internal reflection can cause stray light and so this method is not suitable for high-precision spectroscopy.

- SHIMADZU DIFFRACTION GRATINGS
- 01. Introduction to Diffraction Gratings
- 02. What are Diffraction Gratings
- 03. The Grating Equations
- 04. Dispersion
- 05. Grating Resolution
- 06. Free Spectral Range
- 07. Blaze Wavelength
- 08. Diffraction Efficiency & Relationship between Diffraction Efficiency and Polarization
- 09. Anomalies
- 10. Profile of Grating Grooves
- 11. Toroidal Diffraction Gratings
- 12. Replicas
- 13. Coatings
**14. Transmission Gratings**- 15. Choice of a Grating
- 16. Handling of Gratings