The absolute frequency of the In(+) 5s(2) (1)S(0)5s5p (3)P(0) clock transition at 237 nm was measured with an accuracy of 1.8 parts in 10(13). Using a phase-coherent frequency chain, we compared the (1)S(0)(3)P(0) transition with a methane-stabilized HeNe laser at 3.39 microm, which was calibrated against an atomic cesium fountain clock. A frequency gap of 37 THz at the fourth harmonic of the HeNe standard was bridged by a frequency comb generated by a mode-locked femtosecond laser. The frequency of the In(+) clock transition was found to be 1,267,402,452,899.92 (0.23) kHz, the accuracy being limited by the uncertainty of the HeNe laser reference. This result represents an improvement in accuracy of more than 2 orders of magnitude over previous measurements of the line and now stands as what is to our knowledge the most accurate measurement of an optical transition in a single ion.s.

Article (Published Version) http://sro.sussex.ac.uk Meyer, V, Boshier, M G and et al, (2000) Measurement of the 1s-2s energy interval in muonium.

The principal spectroscopic and lasing characteristics of a Tm(15%) : KY(WO 4 ) 2 crystal were investigated. The transition cross sections, the luminescence quantum yield, and the lifetime and the nonlinear depopulation coefficient of the upper active state were also determined. The slope efficiency of lasing at the 1950 nm wavelength was 45%. The feasibility of tuning in the spectral range 18501 950 nm was demonstrated in principle. S N Bagaev, S M Vatnik, A P Maiorov, D V Plakushchev Institute of Laser Physics, Siberian Division of the Russian Academy of Sciences, prospekt akad. Lavrent'eva 13/3,

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We report on a high-energy ceramic Nd3+:Y3Al5O12 laser. Under the pyrotechnic explosion pumping, quasi-CW output power of about 1.1 KW (≈5.5 J) at 1.06415 μm wavelength (4F3/2 → 4I11/2 lasing channel) was achieved. Pyrotechnically pumped crystalline lasers are characterized by low size and cost, and the highest reported ratio of output energy to their weight.

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We report on the first experimental realization of coherent combining of parametrically amplified femtosecond pulses. The proposed and implemented two-loop active stabilization system allows us to achieve 110 as relative timing jitter between combined pulses, which is necessary for efficient coherent beam combining. In each channel of the two-channel laser setup, pulses were parametrically amplified in β-BaB2O4 (BBO) crystals to 50 μJ energy, compressed to 49 fs duration, and then coherently combined with efficiency as high as 97%. Currently, it is the shortest duration of amplified pulses for which coherent combining is demonstrated.