In this article, we illustrate a series of experiments performed in our group in the field of atom interferometry for precision gravity measurements. We show that instruments measuring and testing gravity can be built both with rubidium and with strontium atoms, while keeping the sources of systematic error under control. The application of these devices in the test of the Weak Equivalence Principle with quantum objects, in the measurement of the Newtonian gravitational constant G and in the development of a new type atom interferometer for the detection of gravitational waves is discussed.
The Space Optical Clocks project aims at operating lattice clocks on the ISS for tests of fundamental physics and for providing high-accuracy comparisons of future terrestrial optical clocks. A pre-phase-A study (2007- 10), funded partially by ESA and DLR, included the implementation of several optical lattice clock systems using Strontium and Ytterbium as atomic species and their characterization. Subcomponents of clock demonstrators with the added specification of transportability and using techniques suitable for later space use, such as all-solid-state lasers, low power consumption, and compact dimensions, have been developed and have been validated. This included demonstration of laser-cooling and magneto-optical trapping of Sr atoms in a compact breadboard apparatus and demonstration of a transportable clock laser with 1 Hz linewidth. With two laboratory Sr lattice clock systems a number of fundamental results were obtained, such as observing atomic resonances with linewidths as low as 3 Hz, non-destructive detection of atom excitation, determination of decoherence effects and reaching a frequency instability of 1×10-16.
We experimentally study two Ti:sapphire optical frequency comb femtosecond regimes, respectively, with a linear and a nonlinear dependence of the carrier-envelope offset frequency (fCEO) on pump intensity. For both regimes, we study the effect of single- and multimode pump lasers on the fCEO phase noise. We demonstrate that the femtosecond regime is playing a more important role on the fCEO phase noise and stability than the pump laser type.
Here we report on absolute frequency measurements of a commercial high power CW diode-pumped solid-state laser
(Coherent Verdi-V5). This kind of lasers usually presents large frequency jitter (up to 50 MHz) both in the short term
(1 ms time scale) and in the long term (>10 s time scale). A precise measurement of absolute frequency deviations in
both temporal scales should require a set of different devices (optical cavities, optical wave-meters), each suited for
measurements only at a specific integration time. Here we demonstrate how a frequency comb can be used to overcome
this difficulty, allowing in a single step a full characterization of both short (<1 ms) and long term (> 103 s) absolute
frequency jitter with a resolution better than 1 MHz. We demonstrate in this way the flexibility of optical frequency
combs for absolute frequency measurements not only of ultra-stable lasers but also of relatively unstable lasers. The
absolute frequency calibration of the Verdi laser that we have obtained have been used in order to improve the accuracy
of the measurements of the local gravitational acceleration value with 88Sr atoms trapped in 1D vertical lattices.
We report on our progress toward the realization of a compact optical frequency standard referenced to strontium
intercombination lines. Our current setup allows the production of ultracold Sr atoms in hundreds of ms. For
high resolution spectroscopy of the 1S0-3P0 doubly forbidden transition we have prepared a 698 nm clock laser
stabilized on a high finesse, symmetrically suspended cavity and a high power 813 nm light source for the
optical lattice trap at the magic wavelength. Due to their compactness, reliability, and low power consumption,
semiconductor laser sources represent the best choice for the development of compact and transportable devices
for application both on Earth and in Space. A new Sr trapping and cooling experimental setup is also presented.
We present a new laser setup suited for high precision spectroscopy on atomic strontium. The source is used for an absolute frequency measurement of the visible 5s21S0-5s5p3P1 intercombination line of strontium which is considered a possible candidate for a future optical frequency standard. The optical frequency is measured with an optical comb generator referenced to the SI through a GPS signal. We developed also an all solid state blue laser source that will be used for laser cooling of strontium, which will result in a better control on the systematic effects and a great improvement in the precision of the measurement.