Observation and investigation of narrow optical transitions of 167Er3+ ions in femtosecond laser printed waveguides in 7LiYF4 crystal

We produced optical waveguides in the 167Er3+ :7LiYF4 crystal with diameters ranging from 30 to 100 mkm by using the depressed-cladding approach with femtosecond laser. These waveguides were studied (both inside and outside) by stationary and coherent spectroscopy on the 809 nm optical transitions between the hyperfine sublevels of 4I15/2 and 4I9/2 multiplets of 167Er3+ ions. It was found that the spectra of 167Er3+ were slightly broadened and shifted inside the waveguides compared to the bulk crystal spectra. We managed to observe a two-pulse photon echo on this transition and determined phase relaxation times for each of waveguides. The experimental results show that the created crystal waveguides doped by rare-earth ions can be used in optical quantum memory and integrated quantum schemes.