Calibration methods of a 2 GHz evanescent microwave magnetic probe for noncontact and nondestructive metal characterization for corrosion, defects, conductivity, and thickness nonuniformities Rev. Sci. Instrum. 76, 054701 (2005); 10. 1063/1.1900683 Planar evanescent microwave imaging probes for nondestructive evaluation of materials with very high spatial resolutions and scan rates AIP Conf.In this article we describe evanescent field imaging of material nonuniformities with a record resolution of 0.4 m at 1 GHz ( g /750 000), using a resonant stripline scanning microwave probe. A chemically etched tip is used as a point-like evanescent field emitter and a probe-sample distance modulation is employed to improve the signal-to-noise ratio. Images obtained by evanescent microwave probe, by optical microscope, and by scanning tunneling microscope are presented for comparison. Probe was calibrated to perform quantitative conductivity measurements. The principal factors affecting the ultimate resolution of evanescent microwave probe are also discussed.
We achieve laser frequency stabilization by a simple technique based on sub-Doppler dichroic atomic vapor laser lock (DAVLL) in atomic cesium. The technique that combines saturated-absorption spectroscopy and Zeeman splitting of hyperfine structures allows us to obtain a modulation-free dispersion-like error signal for frequency stabilization. For the error signal, the dependence of peak-to-peak amplitude and the slope at the zero-crossing point on the magnetic field is studied by simulation and experiment. Based on the result, we obtain an available sub-Doppler DAVLL error signal with high sensitivity to the frequency drift by selecting an appropriate strength of the magnetic field. Ultimately, the fluctuation of the locked laser frequency is confined to below 0.5 MHz in a long term, exhibiting efficient suppression of frequency noise.
Tapered nanofiber is an efficient tool for enhancing light-matter interactions. Here, we experimentally demonstrate the ladder-type electromagnetically induced transparency (EIT) in one-dimensional atomic lattices near an optical nanofiber (ONF). A typical EIT signal is well fitted from experimental data according to a semiclassical model and implies a transmission nearly 35%. We investigate the dependence of EIT transmission on the coupling power and its saturation condition. In addition, we show a large fraction of the transmission spectral broadening is induced by lattice effects. Our results may pave the road towards generating correlations and entanglement through four-wave mixing with ONFs, which may facilitate the realization of efficient quantum optical networks.
We demonstrate the optomechanical cooling of a tapered optical nanofiber by coupling the polarization of light to the mechanical angular momentum of the system. The coupling is enabled by birefringence in the fiber and does not make use of an optical resonator. We find evidence for cooling in the distribution of thermally driven amplitude fluctuations and the noise spectrum of the torsional modes. Our proof-of-principle demonstration shows cavity-less cooling of the torsional degree of freedom of a macroscopically extended nanofiber.
Optical nanofiber (ONF) is a special tool for effectively controlling coupling of light and atoms. In this paper, we study the ladder-type electromagnetically induced transparent (EIT) under ultralow power level in a warm cesium vapor by observing the transmission of ONF that couples the 6S → 6P Cs atoms in the presence of a 6P → 8S control beam through the same fiber. The linewidth and transmission of the EIT signal are investigated at different intensities of the control laser. In addition, we theoretically study the nonlinear interaction at the ONF interface using the multi-level density matrix equations, and obtain good agreements between theory and experiments. The results may have great significance for further study of optical nonlinear effect at low power level.
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