Ultra-slow light propagation by self-induced transparency in ruby in the superhyperfine limit

Abstract

Self-induced transparency is reported for circularly polarized light in the R₁(-3/2) line of a 30 ppm ruby (α-Al₂O₃:Cr³⁺) at 1.7 K in a magnetic field of B‖c=4.5 T. In such a field and temperature, a 30 ppm ruby is in the so-called superhyperfine limit resulting in a long phase memory time, T_M=50 μs, and a thousand-fold slower pulse propagation velocity of ∼300 m/s was observed, compared to the ∼300 km/s measured in the first observation of self-induced transparency (SIT) ∼50 years ago, that employed a ruby with a 500 ppm chromium concentration in zero field and at 4.2 K. To date, this is the slowest pulse propagation ever observed in a SIT experiment.

Optical spin polarization in ruby enhances slow light by high-contrast transient spectral hole-burning

“…In contrast, we have recently reported slow and fast light effects based on transient spectral hole-burning in the R 1 -line at low temperatures [42,43]. We have also reported the generation of ultraslow solitons by self-induced transparency [44,45]. The latter could quantitatively be modeled by simulations applying the optical Bloch equations [44].…”

“…We have also reported the generation of ultraslow solitons by self-induced transparency [44,45]. The latter could quantitatively be modeled by simulations applying the optical Bloch equations [44]. For the hole-burning-caused slow light, the linear filter theory as presented in Refs.…”

Ultra-slow electron spin-lattice relaxation in a low magnetic field enables massive optical spin polarization in the 4A2 ground state of Cr3+ in ruby*

“…In the following four decades, Szabo et al explored a wide range of subtle details in the spectroscopy of the R-lines [17][18][19][20]. In recent years, slow light effects based on spectral hole-burning have been reported [21] and SIT [22] has been re-examined, resulting in demonstrating solitons that propagate with a very low group velocity of ∼300 m s −1 . Very recently we have shown that electron spin polarization by optical pumping could make slow light in ruby slower, that is, this was an experiment where the propagation of light was controlled by two light pulses in the conditioning step [12].…”