Frequency shift by optical coherent control

We report the experimental observation of an optically controllable shift of the central frequency of a laser pulse, using a scheme based on dynamical electromagnetically induced transparency. This is evidence of frequency shift controllable by a coherent process. Original theoretical results are in agreement with the experimental data.

Figure 1

Experimental setup. ECDL, extended-cavity diode laser; ND, neutral-density filter; DM, dichroic mirror; GP, glass plate. (Inset) Scheme of sodium levels involved.

Figure 2

Measured values of the central frequency shift as a function of the detuning of the probe laser from resonance at a temperature of $T=250\hspace{0.5em}{}^{°}$C for several control field peak intensities. Black squares, $I_c=150$ kW/cm${}^2$; solid red circles; $I_c=50$ kW/cm${}^2$; open blue circles, $I_c=25$ kW/cm${}^2$. The results of graph (a) were obtained with the probe pulse overlapped with the rising edge of the control pulse, whereas in (b) the probe pulse was overlapped with the falling edge of the control pulse. The insets show the temporal overlapping of the two pulses at $z=0$ (cell entrance) in the two cases. The dashed line is the control pulse, while the solid line is the probe pulse. The two beams are arranged in a counterpropagating configuration.

Figure 3

Measured values of the central frequency shift as a function of the detuning of the probe laser from resonance for a control peak intensity $I_c=150$ kW/cm${}^2$ and for several temperatures of the sample. Black squares, $T=250\hspace{0.5em}{}^{°}$C; solid red triangles, $T=225\hspace{0.5em}{}^{°}$C; open blue squares, $T=200\hspace{0.5em}{}^{°}$C. The results of graph (a) were obtained with the probe pulse overlapped with the rising edge of the control pulse, whereas in (b) the probe pulse was overlapped with the falling edge of the control pulse. The insets show the temporal overlapping of the two pulses at $z=0$ (cell entrance) in the two cases. The dashed line is the control pulse, while the solid line is the probe pulse. The two beams are arranged in a counterpropagating configuration.

Figure 4

Black squares, experimental data obtained at $T=250\hspace{0.5em}{}^{°}$C and $I_c=150$ kW/cm${}^2$ as a function of the detuning of the probe laser from resonance. Red curves, theoretical fit performed using Eqs. (6) and (7) and treating the density $N$ and the control laser peak intensity as free parameters. The curve is reported only in the range of validity of Eqs. (6) and (7).