We report the laser operation of spinning mirror-based mechanically Q-switched (MQS) 2940 nm Er:YAG with record 805 mJ output energy in a single 61 ns pulse and ~10 ns pulse jitter. The laser was operated at 1Hz repetition rate and 670 Hz rotational rate of the spinning mirror. The highest output energy was achieved with the use of a 300 mm long MQS Er:YAG laser cavity consisting of 70% output coupler, 7x120 mm AR coated Er(50%):YAG crystal, and spinning HR mirror. The maximum output energy was limited by the optical damage of the Er:YAG AR coatings.
We report on mid-IR Fe:ZnSe master oscillator power amplifier (MOPA) laser system operating at room temperature (RT) pumped by a radiation of mechanically Q-switched Er:YAG laser operating at 2.94 m, at 3Hz repetition rate. The maximum output energy was as high as 250mJ in ~250 ns pulses. The RT gain-switched Fe:ZnSe master oscillator demonstrated tunability over 3.60-5.15 µm spectral range with a maximum output energy of ~3 mJ. The output energies of 12 (8), 34 (25) and 60 (48) mJ were demonstrated at 4.4 (4.1) µm in the 1st, 2nd and 3rd stages of amplifier, respectively, with a total pump energy of 200 mJ.
We report the first room temperature gain switched Fe:ZnSe hot-pressed ceramic laser pumped by 2.94 μm radiation of mechanically Q-switched Er:YAG laser. The maximum output energy was obtained to be 2.5 mJ at 32 mJ of pump energy. The measured slope efficiency was 8% with respect to the pump energy. In this experiment, 3.2 mm hot-pressed Fe:ZnSe ceramic sample was used which had 6% active transmission at the pump wavelength. By using absorption cross-section, the concentration of Fe2+ ions was calculated to be N=9*10^18 cm-3.
We report mechanically Q-switched 2.94 µm Er:YAG laser based on spinning mirror with 805 mJ output energy in a single 61 ns pulse at 1 Hz repetition rate and 670 Hz rotational rate of the spinning mirror. This record output energy was achieved with the use of 300 mm long MQS Er:YAG laser cavity consisted of 70% output coupler, 7x120 mm AR coated Er(50%):YAG crystal and spinning HR mirror. The maximum output energy was limited by the optical damage of the Er:YAG AR coatings.
We report laser operation of spinning mirror mechanically Q-switched (MQS), flashlamp pumped 2.94 μm Er:YAG laser depending on the angular speed of the mirror, repetition rate, size and temperature of the gain element, pulse duration and jitter of Q-switch pulses, as well as pump pulse energy. The highest output energy of 260 mJ with a pulse duration of 150 ns was realized with the use of 7×120 mm Er(50%):YAG at 5 Hz repetition rate and 4200 rad/s angular speed of the spinning mirror. The efficiency of Q-switched operation was ~50% with respect to free-running regime. Using optical triggering, the pulse jitter was measured to be smaller than 10 ns for 160 ns Q-switched pulses. Optical triggering could be used for synchronization with mode-locked laser in chirp-pulse and regenerative amplifiers. We also report on development of room temperature gain-switched Fe:ZnSe laser pumped by a radiation of MQS Er:YAG laser. The maximum output energy of 9 mJ from Fe:ZnSe laser was demonstrated using MQS Er:YAG laser as pump source.
There is strong demand for effective gain materials for the 3.0-3.9 μm spectral range not nicely covered by Cr:ZnSe and Fe:ZnSe amplification bands. We characterized, Fe:ZnAl2O4 ceramic sample, Fe:MgAl2O4 and Fe:InP single crystals as promising laser materials for this mid-IR spectral range. In all crystals, the absorption bands corresponding to 5E↔5T2 transition of Fe2+ ions in the tetrahedral sites were measured. In addition, absorption band of Fe2+ ions in the octahedral sites were observed in Fe:ZnAl2O4 sample with maximum absorption cross-section at ~1.0 μm. From the absorption measurements, the radiative lifetime of Fe:MgAl2O4 was calculated to be 60 μs. Saturation absorption of Fe2+ ions in Fe:ZnAl2O4 was studied using Ho:YAG@2.09 μm and Er:YAG@2.94 μm lasers. Saturation measurements were taken up to energy density of 2 J/cm2 and showed no saturation of absorption. This can be explained by a fast non-radiative (<100 ps) relaxation time from the 5T2 level of Fe2+ ions in the Fe:ZnAl2O4 sample at RT. A strong mid-IR photoluminescence (PL) signal in Fe:InP crystal was detected under the direct excitation of the 5E↔5T2 transition of Fe2+ ions using Er:YAG@2.94 μm laser as well as excitation using photo-ionization process under radiation from Nd:YAG@1.064 μm laser. This indicates that Fe:InP crystals could become promising mid-IR laser media with optimization of fabrication technology.
Iron-doped binary and ternary chalcogenide crystals are very promising for tunable solid-state lasers operating over the 3-6 μm spectral range. The most significant results have been reported for iron doped ZnSe crystals with 9.6 W output power in CW at 77K when pumped by radiation of Cr:ZnSe laser, and 1.4 J at ~150 ns pulse duration at room temperature (RT) when pumped by the radiation of HF laser. The lifetime of the upper laser level 5T2 of the Fe2+ ion in a ZnSe matrix falls with temperature from 52µs at 77 K to 370 ns at RT due to the increase of nonradiative relaxation. It allows effective laser oscillation in the gain-switched regime at RT and operation in Q-switched regime at low temperature. We report on RT gain-switched Fe:ZnSe lasers tunable over 3.60-5.15 µm pumped by radiation of mechanically Q-switched Er:YAG laser operating at 2.94 µm. The maximum output energy was measured to be 5 mJ under 15mJ of pump energy. The long upper level lifetime of Fe:ZnSe gain medium is sufficient for energy storage with pumping by radiation of free running Er:YAG lasers. We demonstrated that Q-switched regime of oscillation could be effectively utilized for Fe:ZnSe lasers. The rotating back mirror was used as a mechanical Q-switcher of a Fe:ZnSe laser. The maximum output energy in single 150 ns pulse was measured to be 3mJ which is ~25% from the theoretical limit. This approach could be attractive for development of high-energy short-pulse solid-state mid-IR systems operating over 3.6-5.0 µm spectral range
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