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We describe and characterize alternative configurations for Doppler-free polarization spectroscopy. The suggested apparatus enables complete pump/probe beam overlap and allows substantial miniaturization. Its utility and performance for narrow linewidth, high-stability frequency locking is discussed for the |5S1/2F=2>→|5P3/2F′>D2 transition in 87Rb. [ABSTRACT FROM AUTHOR]

In recent years, diamond magnetometers based on the nitrogen-vacancy (NV) center have been of considerable interest for applications at the nanoscale. An interesting application which is well suited for NV centers is the study of nanoscale magnetic phenomena in superconducting materials. We employ NV centers to interrogate magnetic properties of a thin-layer yttrium barium copper oxide (YBCO) superconductor. Using fluorescence-microscopy methods and samples integrated with an NV sensor on a microchip, we measure the temperature of phase transition in the layer to be 70.0(2) K and the penetration field of vortices to be 46(4) G. We observe pinning of the vortices in the layer at 65 K and estimate their density after cooling the sample in a ∼10-G field to be 0.45(1) μm−2. These measurements are done with a 10-nm-thick NV layer, so that high spatial resolution may be enabled in the future. Based on these results, we anticipate that this magnetometer could be useful for imaging the structure and dynamics of vortices. As an outlook, we present a fabrication method for a superconductor chip designed for this purpose. [ABSTRACT FROM AUTHOR]

We present experimental results demonstrating enhanced current modulation of an antireflection-coated edge-emitting laser diode placed in an external cavity. By eliminating the internal cavity of the laser diode and matching the external cavity free spectral range to the modulation frequency we have increased the modulation response up to nearly complete carrier suppression. We demonstrate the tunability of this enhanced modulation over a range of more than 3 GHz. The power of the modulated beam has been measured to be 10 mW. We have recorded a beat note between the first two optical sidebands of width 1 Hz at 6.834 GHz (corresponding to the hyperfine splitting of the 87Rb ground state). This technique enables the generation of two high-power phase-locked beams for coherent manipulation of atomic states. [ABSTRACT FROM AUTHOR]