Continuous wave synthetic low-coherence wind sensing Lidar: motionless measurement system with subsequent numerical range scanning.

A continuous wave (CW) Lidar system for detection of scattering from atmospheric aerosol particles is presented which is useful in particular for remote sensing of wind velocities. It is based on a low-coherence interferometric setup powered by a synthetic broadband laser source with Gaussian power density spectrum. The laser bandwidth is electronically adjustable and determines the spatial resolution which is independent of range.

Comment on "Nonreciprocal light propagation in a silicon photonic circuit".

We show that the structure demonstrated by Feng et al. (Reports, 5 August 2011, p. 729) cannot enable optical isolation because it possesses a symmetric scattering matrix.

Measurement of nonreciprocal spontaneous Raman scattering in silicon photonic wires.

We report on measurements that show the strength of the spontaneous Raman scattering in strongly confining silicon waveguides to depend significantly on the propagation direction of the amplified signal wave with respect to the pump wave. Furthermore, the strength of this nonreciprocity depends on the orientation of the waveguide with respect to the crystallographic axes. We find that when changing the orientation from ˂011˃ to ˂001˃, the Raman-induced nonreciprocity increases by almost a factor of 3.

Experimental reconstruction of a highly reflecting fiber Bragg grating by using spectral regularization and inverse scattering.

We demonstrate experimentally, for the first time to our knowledge, a reconstruction of a highly reflecting fiber Bragg grating from its complex reflection spectrum by using a regularization algorithm. The regularization method is based on correcting the measured reflection spectrum at the Bragg zone frequencies and enables the reconstruction of the grating profile using the integral-layer-peeling algorithm. A grating with an approximately uniform profile and with a maximum reflectivity of 99.

Analysis of Raman lasing characteristics in silicon-on-insulator waveguides.

Numerical analysis predicts that continuous-wave Raman lasing is possible in silicon-on-insulator (SOI) waveguides, in spite of the detrimental presence of two-photon absorption and free-carrier absorption. We discuss in particular the dependence of the lasing characteristics of SOI Raman lasers on the effective lifetime of the free carriers generated by two-photon absorption. It is shown that the pump-power-dependent cavity losses lead to a rollover of the output-power characteristics at a certain pump-power level and that there exists an upper shutdown threshold at which the laser operation breaks down.