Introduction to Spectroscopy of Cr4+:YAG Transparent Ceramics

Fig. 3: XRD pattern of Cr4+:YAG transparent ceramics (red dots), results of Rietveld refinement analysis (black curve), and the difference between experimental and the calculated pattern (blue curve). Fig. 5: Temperature dependence of Cr4+:YAG transparent ceramic absorption spectra measured at 5-300 K in the range of λ: a) 200-1300 nm; b) 580-1300 nm; c) 1200 nm-1300 nm; The measured spectra were shifted by Δy for better visibility. Fig. 6: PLE (black line) and LE (red line) spectra of Cr3+ ions in the Cr3+,Cr4+:YAG ceramic measured at λexc – 430 nm; λem – 686.5: a) T - 5 K, b) T - 295 K; c) phonon sideband of the R-line at 5 K (black line), and 295 K (red line). The x-axis values were calculated using the formula – Δλ = λ(R1-line) – λ. Fig. 7: PLE and LE spectra of Cr3+ ions in Cr:YAG transparent ceramic measured at λem – 707 nm, λexc – 430 nm, and T – 295 K, corresponding to the 4A2g↔2Eg electron transitions. Lines are included for visual guidance. Fig. 8: Spectroscopic properties of Cr4+:YAG transparent ceramics measured at T – 5 K: a) normalize excitation spectra measured at λem – 1277 nm, 1328 nm, 1358 nm, 1400 nm, and 1482 nm; b) normalize emission spectra measured at λexc – 480 nm, 610 nm, 620 nm, 860 nm, and 980 nm; c) luminescence decay curves measured at λexc – 480 nm (diode laser), and λem – 1278 nm, 1328 nm, and 1400 nm. The black square indicates the area with poor correction on the spectrometer sensitivity. Fig. 9: Luminescence spectra of Cr4+:YAG transparent ceramic measured at λexc – 980 nm and temperatures form 5K to 240K. The insert show the change in the overall Cr4+ emission intensity. Fig. 10: (a) Absorption (black dots) and luminescence (red dots) spectra measured at λexc – 980 nm, T – 5K. Temperature dependence of Cr4+ - ZPLs in Cr4+:YAG transparent ceramic (b) λmax, (c) FWHM, (d) band area (stars represent the spectroscopic parameters of ZPLs for Cr4+ ions in Cr:YAG single crystal [14]). Dashed lines are included for visual guidance. Fig. 11: R1/R2 luminescence intensity ratio of Cr3+ (red dots), Cr4+ (black dots) in Cr:YAG transparent ceramic, and Cr4+ ions in Cr:YAG single crystal. Insert shown Cr4+ ZPLs emission spectra of Cr:YAG transparent ceramic (T – 20 K), and Cr:YAG single crystal (T – 15 K). Dashed lines are included for visual guidance. Fig. 12: Transmittance spectra of the measured Cr4+:YAG transparent ceramic. The insert shows the change in transmittance of Cr4+:YAG transparent ceramic under irradiation by 1064 nm pulsed laser (red circles) as a function of the input energy fluence. Fig. 13. Time profile of laser pulse energy of Nd3+:YAG/Cr4+:YAG Q-switched laser with a) Cr4+ absorption of 1 OD, b) Cr4+ absorption of 0.6 OD. Insert the show-lasing performance of Nd3+:YAG active elements using the scheme with lamp pumping in free-lasing mode (red dots) and passive Q-switching mode using Cr4+:YAG saturable absorber.