Blaze wavelength

The blaze wavelength is that wavelength for which the angle of reflectance from the groove face and the angle of reflection (usually the angle of incidence) from the grating are identical. 

Physically a blaze of white light is observed in the visible region. A grating will typically be useful from approximately one-third of the blaze wavelength to three times the blaze wavelength in the first order. 

The dispersion of the grating is almost linear. However, as already mentioned, individual orders overlap so that either an order filler must be fitted or a predispersion device (prism) must be used. If the grooves are blazed, reflected intensities of mainly one order can be collected. This is at a maximum for a particular angle (blaze angle) and a particular wavelength (blaze wavelength). 

Blaze wavelengths of ca. 320 nm ensure good measurements down to 200 nm even if the transmission of the optical components and sensitivity of the detector decrease in this range. However, this short blaze wavelength cannot usually be compensated for by higher detector. sensitivity if wavelengths of 800- 1000 nm arc measured. 

The form and depth of the grooves determine the blaze angle p defined earlier. The blaze wavelength for order m is ... 

---