Nikolaj A. Es'kov

Calcium niobium gallium and calcium lithium niobium gallium garnets doped with rare earth ions––effective laser media

Abstract The results of spectroscopy and laser action of disordered calcium niobium gallium (CNGG) and calcium lithium niobium gallium (CLNGG) garnets doped with Nd3+, Eu3+, Er3+, Ho3+ and Tm3+ were displayed. The structure and some optical and physical properties of CNGG and CLNGG-crystals were studied. Activator centers construction and the mechanism of inhomogeneous broadening and splitting of spectral lines of rare earth ions (TR3+) in CNGG and CLNGG-crystals were analyzed. Possibilities of laser media based on CNGG and CLNGG with TR3+-ions for pulse free running, Q-switch, CW and ultrashort pulse operation regimes were considered.

Spectroscopic and lasing properties of calcium niobium gallium garnet activated with Cr3+ and Nd3+

An investigation was made of the luminescence and lasing spectra of a calcium niobium gallium garnet crystal activated with Cr3+ and Nd3+ ions. An effective nonradiative energy transfer from the chromium to the neodymium ions was discovered. The probability of an elementary Cr→Nd interaction event was determined. A detailed study was made of the Stark structure of the ground (4I9/2) and metastable (4F3/2) levels of Nd3+. Selective laser excitation was used to identify four main optical Nd3+ centers for which the splitting schemes of the 4I9/2 and 4F3/2 levels were constructed. Lasing was observed at 300 K as a result of the 4F3/2→4I11/2 transition in crystals activated with Cr3+ and Nd3+.

Calcium-niobium-gallium garnets with Nd: a new active medium for lasers with ultrashort pulse duration

Results of spectroscopic and radiation investigations of disordered calcium-niobium-gallium garnets (CNGG) with wide inhomogeneously broadened lines in absorption and luminescence of Nd3+ are presented. A method of a selective and frequency tuned laser excitation at T equals 77 K provided discovery of four groups of optical centers and development of Stark multiplet 4F3/1 and 4I9/2 levels schemes for these centers. Laser excitation at the 4I11/2 yields 4F3/2 transition at T equals 300 K during time resolved luminescence spectra recording at the same transition resulted in discovery of an inhomogeneous character of amplification spectrum broadening as well as in estimation of spectral energy migration among the centers. This time it was found to be longer than the 4F3/2 level lifetime (150 microsecond(s) ec). Results of the investigation of free-generation and passive mode-locking regimes in lasers based on disordered garnets with neodymium are presented. It is shown that energy parameters of the lasers based on CNGG are higher than those of glass lasers. In the passive mode-locked regime pulses are generated with (lambda) equals 1.06 micrometers and duration time 5 - 7 psec. The pulses have positive linear frequency chirp and spectrum broadening up to 60 cm-1. Compression of the chirped pulses in an external compressor provides transfer to femtosecond time scale.