Time delay and broadening of six isolated pulses are studied and experimentally demonstrated in electromagnetically induced transparency (EIT) slow light medium. The optimal pulse for largest delay (smallest broadening) is amplitude-shaped by Single-Exponential (Cosine).
The effect of a proper shaping of the temporal envelope of isolated pulses in slow-light systems based on stimulated Brillouin scattering in optical fibers is studied and experimentally demonstrated. The pulse shape can be optimized to lead to a substantial enhancement of the delaying effect. The spectrum of the optical pulses is engineered so that the spectral width of the pulse is minimized while preserving the pulse duration, making possible to match at best the Brillouin spectrum. Exponentially shaped pulses show the minimal FWHM spectral width and experience the largest time delay when compared to Gaussian or rectangular pulses.
We have experimentally studied the propagation behaviors of light pulses in an electromagnetically induced transparency (EIT) medium. Both phase variation in different parts of a pulse and distortion of the pulse shape are observed. The consistency between the experimental data and theoretical predictions is satisfactory. Our study explains the physical origins of the phase variation and the shape distortion, shows that the phase variation should be taken into consideration in applications utilizing the EIT scheme in which two-photon detuning must exist, and provides better understanding of the propagation behavior of the slow light.
The slow light effects of an amplitude modulated Gaussian (AMG) pulse in a cesium atomic vapor are presented. In a single-Λ type electromagnetically induced transparency (EIT) medium, more severe distortion is observed for an AMG pulse than a Gaussian one. Using Fourier spectrum analysis, we find that the distortion, as well as the loss, is dominantly caused by linear absorption than dispersion. Accordingly, a compensation method is proposed to reshape the slow light pulse based on the transmission spectrum. In addition, we find a novel way to obtain simultaneous slow and fast light.