From near IR to terahertz photon emission in the LaF₃ crystals heavily doped by Nd³⁺; the use of the Dicke and the Purcell effects

We discuss the novel idea for direct terahertz pulse emission as a result of implementation of Purcell and Dicke effects simultaneously in the Nd³⁺ heavily doped LaF₃ crystals after femtosecond near IR laser excitation with high power density at transitions between crystal-field (Stark) levels of the Nd³⁺ manifolds of the appropriate energy. - Highlights: • Heavily doped Nd³⁺:LaF₃ crystal is considered for direct terahertz emission. • The emission can be provided by Purcell and Dicke effects simultaneously. • The enhancement factors for NIR and terahertz emission are estimated. • Comparison of radiative and multiphonon relaxation rates is done. • The energy of the required femtosecond laser pulse is estimated.