5I7 Level Research Articles

Optical transitions of Ho3+ in SrLaGa3O7

Abstract We report the optical properties of SrLaGa3O7 crystal doped with Ho3+ ions. Absorption, emission spectra and observed lifetimes of excited states have been measured and discussed using Judd–Ofelt theory. Emissions from 3D3, 5F3, 5S2, 5F5, 5I5, 5I6, and 5I7 levels have been characterized under one-photon excitation. The experimental lifetimes for the 5S2, 5F5, 5I6, 5I7 states have been compared to the theoretical values, calculated using Judd–Ofelt theory.

Conversion of red light into green light in LiTaO3:Ho

Intense green luminescence associated with the S25–5I8 transition of Ho3+ in holmium doped LiTaO3 crystals has been excited at room temperature and at 15 K by a 647.1 nm line of a krypton ion laser. Based upon the analysis of excited states relaxation dynamics and of the rise of upconverted luminescence it is concluded that the mechanism involved is an excited state absorption from the long lived I75 level. Efficient single wavelength excitation of upconverted luminescence in LiTaO3:Ho is due to the advantageous coincidence of transition energies of the ground and excited state absorptions.

Site‐Selective Upconversion Luminescence of Ho3+ ‐Doped CaF2 Crystals

AbstractWith red dye laser excitation, site‐selective upconversion properties of three Ho3+ centres (C4v, C3v, and dimer) in CaF2, : 0.1 at% Ho3+ crystals are studied. The energy level diagrams for the three centres are deduced from the spectral data. The excited state absorption from the 5I7 level plays a very important role in the upconversion coming from C4v, and C3v centres, whereas the ground state absorption of 5I8, dominates for that from the dimer centre. The upconversion of C4v and C3v centres is explained by a sequential two‐photon excitation mechanism. For the dimer centre, the predominant upconversion mechanism is energy transfer.

Ho3+ Doped 2.84.MU.m Laser Glass for Laser Knives, Sensitized by Yb3+.

The fluorescence properties of the Ho3+5I6→5I7 transition in Yb3+-Ho3+codoped aluminozircofluoride glasses were investigated. The emission wavelength of Ho3+ (5I6→→5I7) at 2.84 μm is almost the same as the vibration oscillation absorption of hydroxyl (OH-1) at 2.89 μm. The emission intensity of Ho3+(5I6→→5I7) transition in Yb3+-Ho3+codopedaluminozirco-fluoride glass is 4.5 times higher than commercial 2.7μm Er3+laser glass. As thelifetime of 5I7 level is longer than 5I6 level, the Nd3+, Eu3+, Pr3+, Sm3+ and Tb3+ were investigatedas deactivator for decreasing the lifetime of 5I7 level. Eu3+and Tb3+ are good candidates for deactivator because they have energy levels which are close to the Ho3+5I7 level todecrease the population of Ho3+5I7 level by energy transfer and have not energy levels whichare close to the Ho3+5I6 level or Yb3+2F5/2 level.

Model for an active medium based on a (Cr,Tm,Ho):YSGG crystal

A new model has been constructed for the active medium (Cr,Tm,Ho):YSGG (corresponding to generation on the 5I7→5I8 transition of the Ho3+ ion). Certain features of the filling of the 3H4 level of the Tm3+ ion and of the 5I7 level of the Ho3+ ion during steady-state pumping which affect the basic generation characteristics of this laser—its differential efficiency and its lasing threshold—have been identified on the basis of this model. Experimental data agree with theoretical predictions.

Holmium in ZBLAN: interplay of lasing, co-lasing and excited-state absorption

Abstract Trivalent holmium in ZBLAN can be easily pumped with an argon laser operating around 0.48 μm. Its lasing transitions at 0.55, 0.75, 1.2 and 2.0 μm are now well-known. However, excited-state absorption at pump and signal wavelengths from the 5I7 and 5I6 levels make the problem of maximum efficiency somewhat tricky. Fluorescence and lasing experiments are reported and details of the influence of excited-state absorption and co-lasing on laser operation are given.

Cascade laser oscillation due to Ho3+ ions in a (Cr,Yb,Ho):YSGG yttrium-scandium-gallium garnet crystal

We report obtaining room-temperature laser oscillation in a flashlamp-pumped (Cr,Yb,Ho):YSGG crystal. The laser action, which is due to the Ho3+ ions, is based on the cascade of transitions 5I6→5I7→5I8. We have measured the lifetimes of the working levels and the laser wavelength. The efficiency of the energy transfer process Cr3+→Yb3+→Ho3+ is 90%. We investigated the kinetics of the laser action and measured the lasing parameters for various types of output mirrors. We also measured the contribution of the laser transition 5I6→5I7 to the populating of the 5I7 level. For pump energies above 20 J, we observed saturation of the populations of the 5I6 and 5I7 levels of the Ho3+ ion. The cause of this saturation is assumed to be a stepwise sensitization of the Ho3+ ion. We obtained oscillation in a totally-reflecting resonator at 3-μm without self-limiting.

Crystals of Yb3Sc2Ga3O12:Cr3+:Ho3+as a promising material for cascade lasing of Ho3+ions

An investigation was made of the possibility of lasing of Ho3+ ions in a Yb3Sc2Ga3O12:Cr3+:Ho3+ crystal in accordance with a cascade scheme 5I6→5I7→5I8 using flashlamp pumping at room temperature. The lifetime of the 2F5/2 level of the Yb3+ ion and of the 5I6 and 5I7 levels of the Ho3+ ion were determined. The efficiency of the Cr3+→Yb3+→Ho3+ energy transfer chain was 60%.

Excitation of Ho3+ ions via energy transfers from Cr3+ and Tm3+ ions in (Ca, Zr)-substituted Gd3Ga5O18 single crystals

(Ca, Zr) substituted Gd3Ga5O12 single crystals containing various amounts of Cr3+, Tm3+ and Ho3+ ions were grown using the Czochralski method. The energy transfers from Cr3+ and Tm3+ ions were analysed and their quantum efficiencies calculated. The stimulated emission cross section of the 5I7 level of Ho3+ in the 1800-2200 nm region was determined using McCumber's theory.

Optical Absorption and Emission in Rare Earth Heavy Metal Fluoride Glasses

AbstractTrivalent thulium is a 4-level laser system which operates in the 1.47μm spectral region. A tunable amplifier at this wavelength is of great interest since it falls in one of the telecommunication windows. For lasing action to occur the relatively long lived 3F4 lower laser level must be quenched to eliminate the self-terminating behavior of thulium. Rosenblatt et al. co-doped Tm and Th into a ZBLAN host to quench the 3F4 lower laser level.[1] Co-doping with Ho offers the possibility of more efficient laser operation, but it must be established whether Ho can effectively quench the lower level of Tm. This preliminary study indicated appreciable energy transfer occurred from the 3F4 level of Tm to the 5I7 level of Ho which decreased the lower laser level lifetime by as much as two orders of magnitude. The subsequent decay of the Ho ions is an issue requiring further investigation.

Energy transfer in Cs2NaHo0.99Er0.01Cl6 and assignment of the 5 I 6 and 5 I 4 levels of HoCl 3? 6

Under excitation into the (2H11/2)Γ6+S6 vibronic level of ErCl3–6 at or above liquid-nitrogen temperature, the 5I4→5I8 luminescence transition of HoCl3–6 is observed in Cs2NaHo0.99Er0.01Cl6. This transition is not observed at these temperatures under excitation into vibronic levels of the 5F3, 5F5 terms of HoCl3–6 in neat Cs2NaHoCl6. The three-ion process responsible for the population of 5I4 involves transfer from 2H11/2 or (4S3/2) ErCl3–6 to (5S2) HoCl3–6 followed by a cross-relaxation between Ho3+ neighbours. The 5I6→5I8 infrared luminescence transition of HoCl3–6 is not observed in neat Cs2NaHoCl6 under excitation into vibronic levels of 5F3, but is observed in Cs2NaHo0.99Er0.01Cl6 since luminescence from 5F5 is quenched by energy transfer to ErCl3–6. Together with detailed analyses of the 5F3, 5S2, 5F5→5I6 luminescence transitions of HoCl3–6 in several cubic elpasolite hosts, these results permit the following energy level assignments (in cm–1) for HoCl3–6 in octahedral symmetry: 5I6 levels: Γ3(8620), aΓ5(8628), Γ2(8667), bΓ5(8705), Γ4(8726) and Γ1(8744). 5I4 levels: Γ1(13 232), Γ4(13 241), Γ3(13 247) and Γ5(13 449). The liquid-helium-temperature 5F3â†�5I8 absorption spectrum of Cs2NaHoCl6 has been reanalysed.

5I7 → 5I8 infrared luminescence spectrum of Cs2NaHoCl6

The 300-15 K luminescence spectrum of Cs2NaHoCl6 is reported for the spectral region 4550–5300 cm−1. In agreement with the calculated magnetic dipole (MD) intensity ratios, twenty MD allowed pure electronic transitions are observed and assigned, corresponding to transitions between the crystal field components of 5I7 → 5I8. The ungerade vibronic origins associated with these transitions are at least an order of magnitude weaker. All of the crystal field levels of the 5I7, 5I8 Russell—Saunders terms are assigned from the spectral analysis. The long-term lifetime of the 5I7 levels is near 50 ms at 85 K.