Figure 1

(a) Four level hole-burning spectrum (Zeeman levels) for the class of ions where the laser is in resonance with the $\mid g_{-}⟩\to \mid e_{-}⟩$ transition. The $g_G$ $\left(g_E\right)$ is the $g$ factor for the ground (excited) state, ${\mu }_B$ is the Bohr magneton, and $B$ is the applied magnetic field. The pump transition (solid line) and possible probe transitions (dashed lines) between the four levels are shown in the energy diagram and labeled on the corresponding transmission spectrum of holes and antiholes. (b) Four level hole-burning spectrum with inhomogeneous broadening. The four different classes of ions within the inhomogeneous profile, which are in resonance with the pump beam, are shown along with the resulting transmission spectrum of holes and antiholes (here, the probe transitions are not shown for clarity).Reuse & Permissions

Figure 2

Absorption as a function of wavelength over the inhomogeneously broadened absorption spectrum of the transmission. The inhomogeneous broadening is roughly $2.1\mathrm{GHz}$ and the absorption is strongly polarization dependent, with $\alpha L$ of $-3.7$ for light polarized parallel to the crystal $c$ axis (filled circles) and $-0.6$ for light polarized perpendicular to the crystal $c$ axis (open circles).Reuse & Permissions

Figure 3

Area of the central hole $1\mathrm{ms}$ after spectral hole burning as a function of the applied magnetic field. Here, $B$ was parallel to the $c$ axis with $T=4.2\mathrm{K}$.Reuse & Permissions

Figure 4

Spectral hole for applied magnetic fields $B=15\mathrm{mT}$ (open circles) and $300\mathrm{mT}$ (filled circles) parallel to the crystal $c$ axis. Temperature of the sample, $T=2.1\mathrm{K}$. Points are data and lines are a fit to a Gaussian with full widths at half maximum of $3.8\pm 0.2\mathrm{MHz}$ and $125\pm 4\mathrm{kHz}$, respectively.Reuse & Permissions

Figure 5

Transmission spectra for hole burning with (a) $B\Vert c$ and (c) $B\perp c$. The separation of the holes and antiholes from the central hole as a function of applied field is plotted in (b) for $B\Vert c$ and (d) for $B\perp c$. The lines are fits to the data and the $g$ values extracted are for $B\Vert c$, $g_G=0.92$, $g_E=1.05$, and $g_E-g_G=0.13$, and for $B\perp c$, $g_E=0.28$.Reuse & Permissions

Figure 6

Area of spectral hole as a function of waiting time at $T=2.1\mathrm{K}$ with applied magnetic fields of $5\mathrm{mT}$ (open circles) and $300\mathrm{mT}$ (filled circles). The decay is fit to an exponential with lifetimes of $2.1\pm 0.4$ and $6\pm 1\mathrm{ms}$, respectively.Reuse & Permissions

Figure 7

(Color online) Spectrum after pumping a wide pit in the inhomogeneous absorption profile. (a) Transmission in percentage for two different wavelengths corresponding to initial transmissions of 5% at the center of the inhomogenous profile (red) and 67% off center (black). (b) Percentage of ions that remain in the ground state being probed by the laser, calculated from the data in (a).Reuse & Permissions