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We report the first operation of a direct diode-pumped tunable chromium-doped solid-state laser. A small alexandrite (Cr:BeAl2O4) crystal was longitudinally pumped by two visible laser diodes. The threshold pump power was 12 mW using the R1 line at 680.4 nm for the pump transition, and the slope efficiency was 25%. The measured laser output bandwidth was 2.1 nm.

A Cr:LiSrAlF(6) laser is diode pumped with both commercial 10-mW visible laser diodes and a higher-power 100-mW cw, 265-mW pulsed diode. Polarization combination of pump diodes to reach threshold is demonstrated with two low-power lasers. Pumping with the high-power diode produced powers of 19.9 mW cw and 78 mW pulsed. Details of the Cr:LiSrAlF(6) crystal growth and high-power diode architecture are presented, along with optical characterization data for the laser resonator. Passive losses in the crystal are less than 0.1% cm(-1).

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Fresh seed from seven clones of Populustremuloides Michx., and seed from the same collections stored at −18 °C for 1, 6, 12, and 24 months, were germinated at five water potentials (0, −2, −4, −8, and −12 bars; 1 bar = 100 kPa) and two night–day temperature regimes (20–30 °C and 15–25 °C).Germination was not significantly reduced at any moisture stress used, by storage. Average germination of fresh seed at 0 and −2 bars was 94%. Germination at −4 bars was 61% with much variation among clones and between temperature regimes. When the effect of temperature was significant, the 20–30 °C regime was the better. At −8 and −12 bars, little or no germination occurred.Coronet development occurred on at least 85% of the seedlings from all clones, after all storage times, under either germination temperature regime, at moisture stresses up to and including −8 bars. At −12 bars, coronet development occurred much less frequently, and the 20–30 °C temperature regime was the better. Cotyledon expansion occurred on at least 80% of the seedlings at moisture stresses up to and including −4 bars. At −8 and −12 bars, the frequency of cotyledon expansion dropped, and the 20–30 °C temperature regime was the better.