Picosecond 554 nm yellow-green fiber laser source with average power over 1 W.

We demonstrate a source of 554 nm pulses with 2.7 ps pulse duration and 1.41 W average power, at a repetition rate of 300 MHz. The yellow-green pulse train is generated from the second harmonic of a 1.11 µm fiber laser source in periodically-poled stoichiometric LiTaO3. A total fundamental power of 2.52 W was used, giving a conversion efficiency of 56%.

Wavelength-scale imaging of trapped ions using a phase Fresnel lens.

A microfabricated phase Fresnel lens was used to image ytterbium ions trapped in a radio frequency Paul trap. The ions were laser cooled close to the Doppler limit on the 369.5 nm transition, reducing the ion motion so that each ion formed a near point source. By detecting the ion fluorescence on the same transition, near-diffraction-limited imaging with spot sizes of below 440 nm (FWHM) was achieved. To our knowledge, this is the first demonstration of wavelength-scale imaging of trapped ions and the highest imaging resolution ever achieved with atoms in free space.