Continuous-wave and Q-switched microchip laser performance of Yb : Y3Sc2Al3O12 crystals

Optical properties of Yb:Y3Sc2Al3O12 crystal were investigated and compared with those from Yb:YAG crystals. The broad absorption and emission spectra of Yb:Y3Sc2Al3O12 show that this crystal is very suitable for laser-diode pumping and ultrafast laser pulse generation. Laser-diode pumped continuous-wave and passively Q-switched Yb:Y3Sc2Al3O12 lasers with Cr4+: YAG crystals as saturable absorber have been demonstrated for the first time. Continuous-wave output power of 1.12 W around 1032 nm ( multi-longitudinal modes) was measured with an optical-to-optical efficiency of 30%. Laser pulses with pulse energy of over 31 mu J and pulse width of 2.5 ns were measured at repetition rate of over 12.7 kHz; a corresponding peak power of over 12 kW was obtained. The longitudinal mode selection by a thin plate of Cr4+: YAG as an intracavity etalon was also observed in passively Q-switched Yb:Y3Sc2Al2O12 microchip lasers. (C) 2008 Optical Society of America

Concentration-dependent laser performance of Yb:YAG ceramics

Laser performance of Yb:YAG ceramics and single-crystals doped with different Yb concentrations was investigated using two-pass pumping miniature laser configuration. Better laser performance was observed for heavy-doped Yb:YAG ceramic than single-crystal (C-Yb = 20 at.%). (C) 2008 Optical Society of Americ

Multi-pulse oscillation and instabilities in microchip self-Q-switched transverse-mode laser

Xiamen University (NCETXMU); Ministry of Education, Science and Culture of JapanMulti-transverse-mode competition, coupling induced instabilities and multi-pulse or satellite pulse oscillations were investigated experimentally and theoretically in laser-diode-pumped Cr, Nd:YAG self-Q-switched microchip lasers under large pump beam diameter. The different transverse modes have great effects on the laser pulse temporal characteristics such as pulse profile, pulse width, instability of peak power and repetition rate jitter. Multi-transverse-mode, multi-pulse oscillation and periodical pulsation were observed by varying the pump beam diameter. The effect of transverse modes on the instability and multi-pulse oscillation were studied by modified coupled rate equations by taking into account the transverse-mode competition of inversion population under different pump conditions. The numerically simulated results are in good agreement with the experimental results. These results show that the multi-pulse oscillation and instability in the pulse train were attributed to different transverse mode coupling and competition. The peak power instabilities and pulse repetition rate jitter of the laser pulses due to transverse mode coupling were also investigated. (C) 2009 Optical Society of Americ

Composite Yb : YAG/Cr4+: YAG ceramics picosecond microchip lasers

Efficient laser-diode pumped picosecond self-Q-switched all-ceramic composite Yb: YAG/ Cr4+: YAG microchip lasers with 0.72 MW peak power has been developed. Lasers with nearly diffraction-limited beam quality (M-2 < 1.09), oscillate at stable single- and multi- longitudinal-modes due to the combined etalon effects in the Yb:YAG and Cr4(+:) YAG parts of its binary structure. (C) 2007 Optical Society of America

Effect of ytterbium concentration on Yb : YAG microchip laser performance at ambient temperature

The microchip laser performance of Yb:YAG crystals doped with different ytterbium concentrations (10, 15, and 20 at.%) has been investigated at ambient temperature. Efficient laser oscillation for 1-mm-thick YAG doped with 10 at.% Yb3+ ions was achieved at 1030 and 1049 nm with slope efficiencies of 85 and 81%, correspondingly

Transient temperature profile in the gain medium of CW- and end-pumped passively Q-switched microchip laser

The transient temperature profile in CW- and end-pumped passively Q-switched (PQS) microchip laser is investigated qualitatively by treating the population inversion (thereby the thermal load) as the sawtooth function of the time. The numerical results reveal not only the dynamics of thermal buildup, but also the dependence of the quasi-steady-state temperature rise and the repetitively oscillatory amplitude on the incident pump power and the pulse repetition rate of PQS laser. The abruptly ascending branch of the repetitive temperature oscillation is synchronized with the pulsing stage of PQS laser. As the result, the abrupt temperature transition during the pulsing stage would introduce the fluctuation into the PQS pulse parameters (pulse energy, pulse width, and peak power) via temperature-dependent stimulated emission and thermal lensing effect. (c) 2006 Elsevier B.V. All rights reserved

Maximum value of the pulse energy of a passively Q-switched laser as a function of the pump power

The finite recovery time T-s of the bleached absorber is presented as one of the possible mechanisms accounting for the increase-maximum-decrease in pulse energy E with the pumping rate W-p in cw-pumped passively Q-switched solid-state lasers. by analytically evaluating the sign of the derivative partial derivative E/partial derivative W-p. The results show that. in the low punipinie (T > T-s, T is the interpulse period). the initial repopulation density n, remains constant. the final population density n(i) decreases with W-p. and this results in a monotonic increase of E with W-p. In the high pump regime (T < T-s). n, decreases but n(i) remains the same with W-P; this results in a monotonic decrease of E with W-p. At the critical region (T approximate to T), E reaches its maximum value. A cw-pumped Yb:YAG laser passively Q switched by a Cr4-:YAG absorber is demonstrated to confirm this model. The theoretical model is also applied to the analysis of three previously reported passive Q switching solid-state [Nd:GdVO4, Nd-:LaSc3(BO3)(4) (Nd-:LSB), and Nd:YAG] lasers experiments. (c) 2006 Optical Society of America

A star-bursting proto-cluster in making associated to a radio galaxy at z=2.53 discovered by H_alpha imaging

We report a discovery of a proto-cluster in vigorous assembly and hosting strong star forming activities, associated to a radio galaxy USS 1558-003 at z=2.53, as traced by a wide-field narrow-band H_alpha imaging with MOIRCS on Subaru Telescope. We find 68 H_alpha emitters with dust-uncorrected SFRs down to 8.6 Msun/yr. Their spatial distribution indicates that there are three prominent clumps of H_alpha emitters, one surrounding the radio galaxy and another located at ~1.5 Mpc away to the south-west, and the other located in between the two. These contiguous three systems are very likely to merge together in the near future and may grow to a single more massive cluster at later times. Whilst most H_alpha emitters reside in the "blue cloud" on the color--magnitude diagram, some emitters have very red colors with J-Ks>1.38(AB). Interestingly, such red H_alpha emitters are located towards the faint end of the red sequence, and they tend to be located in the high density clumps. We do not see any statistically significant difference in the distributions of individual star formation rates or stellar masses of the H_alpha emitters between the dense clumps and the other regions, suggesting that this is one of the notable sites where the progenitors of massive galaxies in the present-day clusters were in their vigorous formation phase. Finally, we find that H_alpha emission of the radio galaxy is fairly extended spatially over ~4.5 arcsec. However it is not as widespread as its Lya halo, meaning that the Lya emission is indeed severely extended by resonant scattering.Comment: 14 pages, 11 figures, 3 tables, accepted for publication in Ap