Spectral hole burning in the trivalent thulium ion

Spectral hole burning is reported for the trivalent thulium ion with measurements on the 3H6(1) ↔ 3H4(1) transition of LaF3+ and two sites (A and B) of CaF2+ at 1.5 K. Hole burning occurs by population storage in the metastable 3F4 level. The holes were scanned by an electric-field ramp applied directly to the sample, the frequency being calibrated by burning multiple holes with a frequency-modulated laser. This yielded the hole widths as well as the Stark coefficients for the transition studied, which are 8.3 kHz/V cm−1 parallel to the C2 axis (LaF3+) and for CaF2+ are 25 kHz/V cm−1 (site A), and 4.6 kHz/V cm−1 (site B) for fields along the (001) direction. From the polarization behavior of the holes, the sites in CaF2 are assigned to the F−-compensated C4v and C3v sites, respectively. © 1993 Optical Society of America.