Rami Arieli: "The Laser Adventure" Chapter 8 Section 2, page 10
Explanations about diffraction grating for choosing specific wavelength
The diffraction grating is made of triangular shaped bumps on a planar surface.

Reflection from diffraction grating is into several diffraction orders. Thus energy is reflected into several directions (as seen in figure 8.12a).

Figure 8.12a: Reflection from diffraction grating.

Each diffraction order contains all the wavelength spectrum of the incident wave.

Within each diffraction order, the longer the wavelength, the higher the deflection.

It is possible to design diffraction grating for a specific wavelength, such that most of the energy will be reflected into the first order. Such design is explained in the following pages.