Short-wavelength lasers based on a transient collisional excitation (TCE) have extensively been studied using neon (Ne)-like and nickel (Ni)-like ions. In this study, we have examined the possibility of amplified spontaneous emission (ASE) at 111.9 nm in a Ne-like aluminum (Al) plasma using the TCE scheme. Al targets in vacuum were irradiated with two time-delayed Nd:YAG laser pulses (wavelength: 1,064 nm). A pre-pulse laser generated a pre-formed plasma, and subsequently a grazing-incidence main-pulse laser axially heated it to excite 3p (1S0)–3s (1P1) transition of Al3+ ion. To achieve effective energy deposition in the region of electron density of ∼ 1018 cm−3, the main-pulse was introduced at 3.5° incidence angle. Under optimized conditions, a sharp spectral line at 111.9 nm, corresponding to the 3p–3s lasing transition in Ne-like Al ion, was observed. Although clear ASE was not observed, this work confirms the feasibility of vacuum ultraviolet (VUV) ASE generation by means of this scheme. Further improvements in pulse synchronization and irradiation conditions would show the prominent evidence of 111.9-nm ASE phenomenon.
Takehiro et al. (Thu,) studied this question.