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. This is the first demonstration of imaging trapped ions with a resolution on the order of the transition wavelength.Comment: 8 pages, 3 figure

Optogalvanic Spectroscopy of Metastable States in Yb^{+}

The metastable ^{2}F_{7/2} and ^{2}D_{3/2} states of Yb^{+} are of interest for applications in metrology and quantum information and also act as dark states in laser cooling. These metastable states are commonly repumped to the ground state via the 638.6 nm ^{2}F_{7/2} -- ^{1}D[5/2]_{5/2} and 935.2 nm ^{2}D_{3/2} -- ^{3}D[3/2]_{1/2} transitions. We have performed optogalvanic spectroscopy of these transitions in Yb^{+} ions generated in a discharge. We measure the pressure broadening coefficient for the 638.6 nm transition to be 70 \pm 10 MHz mbar^{-1}. We place an upper bound of 375 MHz/nucleon on the 638.6 nm isotope splitting and show that our observations are consistent with theory for the hyperfine splitting. Our measurements of the 935.2 nm transition extend those made by Sugiyama et al, showing well-resolved isotope and hyperfine splitting. We obtain high signal to noise, sufficient for laser stabilisation applications.Comment: 8 pages, 5 figure

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

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%. © 2014 Optical Society of America

Effects of flake size on mode-locking behavior for flake-graphene saturable absorber mirrors

After advent of graphene as a saturable absorber, it has been proved as a promising material to generate ultrafast laser pulses. Here, we have measured the properties of flake-graphene saturable absorber mirrors of various flake sizes, dependent on the fabrication technique. These mirrors enabled us to obtain the mode-locking bandwidth of 16 nm in an erbium-doped fiber laser. Mirrors with large flake size and multi-layered thickness induce strong pulse shaping and reflect wideband mode-locked pulse train

High-power ultrafast laser source with 300 MHz repetition rate for trapped-ion quantum logic

Trapped ions are a major candidate technology for scalable quantum computation. However, current methods for performing quantum logic gates with trapped ions are limited to gate times of about 10 μs. This drawback is overcome in a recently proposed scheme that uses pairs of counter-propagating π-pulses, resonant with an allowed ion transition, where the time needed for a gate operation is inversely proportional to the laser repetition rate [1]. Our MOPA architecture allows scaling to high repetition rate at constant pulse energy. © 2011 IEEE