What is the blaze angle and blaze wavelength of a grating and how are they related?

The sawtooth shaped groove profile of a ruled grating (the longer face) forms a specific angle relative to the surface of the flat substrate. This angle is known as the blaze angle. The wavelength of light that yields the greatest absolute efficiency of the ruled diffraction grating is called the blaze wavelength. Light equal to the blaze wavelength will have a diffraction angle equal to the blaze angle when the incident angle of the light is also equal to the blaze angle.