Pumping wavelength related population inversion in Nd:doped laser

Abstract

Pumping wavelength related population inversion in an Nd:doped laser has been investigated, where the laser is regarded as two thermodynamic equilibrium systems: the upper state and the lower state. The population inversion limits at various pumping wavelengths and temperatures are compared. The effective metastable lifetime has been derived, where both pump and laser fields within the Nd:doped laser medium reduce the lifetime. The saturation of the lifetime is discussed. As a result, in-band pumping of the Nd:doped laser is good for improving the efficiency and achieving the narrow-linewidth of the laser wavelength due to less population inversion; off-band pumping is beneficial for extracting high pulse energy, thanks to large population inversion.

Study of Active Medium Length Effect on Characteristics of Passive QSwitching and Stokes with Anti-Stokes Pulse

“…Nd +3 ion has many permissible transitions from the metastable level 4 F 3/2 to the lower lying energy Stark sublevels 4 I 13/ 2 , 4 I 11/2 , and 4 I 9/2 , respectively, resulting in possible laser radiations at 1.3, 1.06, and 0.9µ m. Pump bands are placed above the top laser level, beginning with the manifold 4 F 5/2 , which is responsible for absorption around 800 nm. The greatest emission cross-sections in Nd +3 doped laser material for 4 F 3/2 → 4 I 11/2 transitions emitting radiation at 1.06µm are shown in Figure 2 (9) . Stimulated Raman scattering (SRS) is a way that shifts the existing wavelength to a new one (also known as Raman shift).…”