V. Petričević

Laser action in chromium‐doped forsterite

Room‐temperature vibronic pulsed laser action in trivalent chromium‐activated forsterite (Cr3+:Mg2SiO4) is reported for the first time. The free‐running laser emission is centered at 1235 nm of the broad 4T2→4A2 fluorescence band, and has a bandwidth of ∼22 nm.

Laser action in chromium‐activated forsterite for near‐infrared excitation: Is Cr4+ the lasing ion?

Room‐temperature pulsed laser action has been obtained in chromium‐activated forsterite (Cr:Mg2SiO4) for excitation of the near‐infrared absorption band of the system by the 1064 nm radiation from a Nd:YAG laser. The characteristics of laser emission are similar to those observed for 532 nm pumping. It is suggested that the laser action is due to a ‘‘center’’ other than the trivalent chromium (Cr3+), presumably the tetravalent chromium (Cr4+).

Continuous-wave laser operation of chromium-doped forsterite

Room-temperature continuous-wave laser action in chromium-activated forsterite (Cr:Mg(2)SiO(4)) has been achieved for longitudinal pumping in a nearly concentric cavity by the 1064-nm radiation from a cw Nd:YAG laser. The laser emission is centered at 1244 nm and has a spectral bandwidth of 12 nm. An output-power slope efficiency of 6.8% is measured. The effective emission cross section is estimated to be ~1.1 x 10(-19) cm(2).

Self-mode-locked chromium-doped forsterite laser generates 50-fs pulses.

Stable transform-limited (ΔνΔτ = 0.32) femtosecond pulses with a FWHM of 50 fs were generated from a self-mode-locked chromium-doped forsterite laser. The forsterite laser was synchronously pumped by a cw mode-locked Nd:YAG (82 MHz) laser that generated picosecond pulses (200–300 ps) and provided the starting mechanism for self-mode-locked operation. Maximum output power was 45 mW for 3.9 W of absorbed pumped power with the use of an output coupler with 1% transmission. The self-mode-locked forsterite laser was tuned from 1240 to 1270 nm.

Slope efficiency measurements of a chromium-doped forsterite laser

The slope efficiency of the continuous-wave chromium-doped forsterite (Cr:Mg(2)SiO(4)) laser has been measured by using four different output mirrors. The maximum slope efficiency of 38% was achieved with an 11% output coupler. The extrapolated limiting slope efficiency in the absence of passive losses is estimated to be 65%. This value corresponds to an intrinsic quantum efficiency of 77%, which is similar to the efficiencies determined for mature tunable solid-state laser systems.

Nonradiative transition dynamics in alexandrite

The first direct picosecond time‐resolved measurement of the nonradiative transition dynamics between the excited 4T2 pump band and the metastable 2E storage level of the trivalent chromium ion in alexandrite is reported. The nonradiative relaxation times of 17 ps for intra‐4T2 vibrational transitions, and 27 ps for 4T2→2E electronic transition are obtained. The thermal repopulation rate of the 4T2 state from the metastable 2E level is of the order 3.5×109 s−1.

Picosecond excite‐and‐probe absorption measurement of the 4T2 state nonradiative lifetime in ruby

In a picosecond excite‐and‐probe absorption measurement, a 527‐nm picosecond pulse excites the 4T2 state of the Cr3+ ion in ruby and a 3.4‐μm picosecond probe pulse monitors the growth and decay of population in the 2E state as a function of pump‐probe delay. From the growth of population in the metastable 2E state, an upper limit of 7 ps for the nonradiative lifetime of the 4T2 state is determined.

Picosecond excite-and-probe absorption measurement of nonradiative transition dynamics in emerald

Abstract The nonradiative transition dynamics between the excited 4T2 state and the metastable 2E storage state of the trivalent chromium ion in emerald is investigated using the picosecond excite-and-probe absorption technique. An intra-4T2 state vibrational relaxation time of 23 ps, and a 4T2→2E electronic relaxation time of 20 ps are obtained. The thermal repopulation rate of the 4T2 state from the metastable 2E level is ~9.0×109 s-1.

Picosecond excite‐and‐probe absorption measurement of the intra‐2EgE3/2‐state vibrational relaxation time in Ti3+:Al2O3

The kinetics of vibrational transitions in the 2EgE3/2 electronic state of Ti3+:Al2O3 is studied by exciting higher lying vibrational levels of the state by a 527‐nm picosecond pump pulse, and monitoring the subsequent growth of population in the zero vibrational level and lower lying vibrational levels by a 3.9‐μm picosecond probe pulse. An upper limit of 3.5 ps for intra‐2EgE3/2 ‐state vibrational relaxation time is estimated.

Laser and spectroscopic properties of chromium‐activated forsterite

Room‐temperature pulsed laser action has been obtained in chromium‐activated forsterite (Cr:Mg2SiO4) for both 532‐nm and 1064‐nm pumping. Free running laser emission in both cases is centered at 1235 nm and has bandwidth of ∼20 nm. Slope efficiency as high as 22% has been measured. Using different sets of output mirrors and a single birefringent plate as the intracavity wavelength‐selecting element tunability over the 1167–1268 nm spectral range has been demonstrated. Continuous‐wave laser operation at room temperature has been obtained for 1064‐nm pumping from a cw Nd:YAG laser. The output power slope efficiency is 6.8%. The gain cross section is estimated to be 1.1×10−19 cm2. Spectroscopic studies suggest that the laser action is due to a ‘center’ other than the trivalent chromium (Cr3+), presumably the tetravalent chromium (Cr4+) in a tetrahedrally coordinated site.