1.11 Defining properties of a spectral line

The peak wavelength of an LED is typically described by a series of physical quantities. It should be noted that in case of a symmetric line spectrum, the centroid, peak and center wavelengths are identical since they coincide. Only the full width at half maximum value (FWHM) gives differing information.

• Peak wavelength, λ_p
  It is defined as the wavelength at which the spectral distribution or line reaches its largest value.

• Centroid wavelength, λ_c
  This wavelength defines the position of the spectral center of mass.

• Centre wavelength, λ_s
  The center wavelength is defined as the center of the FWHM.

• Full width at half maximum (FWHM)
  This quantity gives information about the width of a radiator at half the height of its maximum.

Fig. 1: Defining properties of a spectral line