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

Abstract

The spin-lattice relaxation time in the 4 A 2 ground state of C r 3 + in ruby can be on the order of magnitude of seconds at liquid helium temperatures in low magnetic fields B | | c . This allows for highly efficient optical pumping of the spin levels in this system. Such pumping can then in turn be employed to drastically increase the optical density of the inhomogeneously broadened R 1 ( ± 3 / 2 ) or R 1 ( ± 1 / 2 ) lines and also to narrow the spectral hole width because Cr–Cr electron-spin flips (cross relaxation) are suppressed in the ground state, leading to longer dephasing times T 2 ∗ . Both effects can be employed to further reduce the group velocity of light pulses propagating through a transient spectral hole.

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*

“…Ruby has also been the subject of many investigations into electron spin-lattice relaxation in the 4 A 2 ground state and the 2 E excited state, both by theoretical and experimental studies [26][27][28][29]. Typically, the reported electron spin-lattice relaxation times were up to ∼500 ms around 2 K for the ground state but in our recent work, we reported a spin-lattice relaxation time of ∼1 s at 2 K for the |+3/2 level in a low magnetic field B c = 59 mT [12]. Experiments were also conducted at temperatures as low as ∼140 mK where a spin-lattice relaxation time T 1 of ∼3.7 s was measured [30].…”

“…with g ex = 2.445 and 1.6 for the E ( 2 E) and 2A ( 2 E) levels, respectively [11]. In figure 1(c), the absorption spectrum in the region of the R 1 transitions is displayed for zero field and a low magnetic field B c = 235 mT at ∼2 K. The inhomogeneous width of the transitions is ∼1.4 GHz as is typical for Czochralski-grown rubies [12]. This relatively narrow width allows the detection of the transitions of the 50, 53 and 54 isotopes with natural abundancies of 4.35, 9.50 and 2.36%, respectively.…”

“…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].…”

Persistent Spectral Hole-Burning and Zeeman Effect of X-ray-Induced Sm2+ in CaF2:Sm3+ Nanocrystals

“…Such a depletion (or frequency selective bleaching) creates a spectral hole (dip) in the absorption (or photoluminescence excitation) band. − The hole is either stable, which leads to a persistent hole, − or it can be based on metastable population storage, i.e. it decays on the microsecond to millisecond time scale, creating a transient spectral hole. , Importantly, inhomogeneous broadening is strongly dependent on the local environment of a system such as point defects, impurities, strains, and isotope distributions. , …”

“…it decays on the microsecond to millisecond time scale, creating a transient spectral hole. 1,8 Importantly, inhomogeneous broadening is strongly dependent on the local environment of a system such as point defects, impurities, strains, and isotope distributions. 2,9 Spectral hole-burning of Sm 2+ doped inorganic materials has been intensively investigated for both fundamental research 10−14 and possible applications, including frequencydomain optical data storage (FDOS) by persistent spectral hole-burning (PSHB).…”