The first infrared wavelength band has wavelengths less than wavelengths of the second infrared wavelength band.

Further, each wavelength band contains two or more optical wavelength channels within that wavelength band.

The first radiation may have a first wavelength band, and the second radiation may have a second wavelength band.

A band of emitted wavelengths of the first crystal is adapted to the at least one band of wavelengths.

The emissivity is inferred from reflectivity measured at two wavelengths in an irradiation wavelength band and extrapolated to a wavelength in an emission wavelength band.

A band of emitted wavelengths of the second crystal also is adapted to the at least one band of wavelengths.

A center wavelength of the second band of wavelengths is greater than a center wavelength of the first band of wavelengths.

A center wavelength of the second band of wavelengths is greater than a center wavelength of the first band of wavelengths.

The active region is configured to emit light having a first band of wavelengths selected from a first group of wavelengths.

The active region is configured to emit light having a first band of wavelengths from a first group of wavelengths.

The phosphor layer is configured to convert the first band of wavelengths of light emitted from the active region to a second band of wavelengths.

Multiple waveplates are combined to produce any of wavelength band specific retarders and multiple non contiguous wavelength band specific retarders.

The phosphor layer is configured to convert the first band of wavelengths of light emitted from the active region to a second band of wavelengths.

The at least one layer of undoped quantum dots absorbs at one or more wavelengths outside the band of wavelengths and outputs at least partially in the band of wavelengths.

The first wavelength band may be substantially different from the second wavelength band.