U-band Amplifiers Research Articles

Tm<sup>3+</sup>-doped Bismuth Tellurite Glasses for S- and U-band Optical Amplifiers

Effective ~1.47mm and powerful ~1.8mm infrared emissions have been observed in Tm3+-doped bismuth tellurite glasses with low phonon energy under the excitation of 793nm diode laser. Judd-Ofelt parameters W2 (4.65´10-20cm2), W4 (1.15´10-20cm2), and W6 (1.16´10-20cm2) indicate a higher asymmetric and stronger covalent environment in the optical glasses. In 0.5wt% Tm3+-doped sample, the peak emission cross-sections of 3H4®3F4 and 3F4®3H6 transitions are derived to be 2.83´10-21 and 6.13´10-21cm2, respectively, and the maximum gain coefficients of 0.38 and 2.21dB/cm at 1.675 (U-band edge) and 1.856mm wavelengths were anticipated in an ideal status. These results indicate the Tm3+-doped bismuth tellurite glasses are a promising candidate in developing S- and U-band amplifiers.

Radiative Transitions and Optical Behaviors in Tm<sup>3+</sup> Doped Mixed Alkali/Alkaline-Earth Modified Heavy-Metal Gallate Glasses

Efficient ~1.48 and ~1.8mm infrared emissions have been recorded in Tm3+doped mixed alkali/alkaline-earth modified heavy-metal gallate glasses (LKBPBG) with low phonon energy under 793nm excitation. Judd-Ofelt parameters W2(4.34´10-20cm2), W4(9.74´10-21cm2) and W6(1.00´10-20cm2) indicate a higher asymmetric and stronger covalent environment in the glass material. The spontaneous transition probability and maximum emission cross-section of3H4→3F4transition are derived to be 283s-1and 2.90´10-21cm2. The maximum emission cross-section of3F4→3H6transition is calculated to be 6.82´10-21cm2, and the ideal net gain coefficients at 1.675 (U-band edge) and 1.872mm are given to be 0.56 and 3.51dB/cm, respectively, as the population inversion equals 1.0, which provide a theoretical anticipation in developing U-band amplifiers and eye-safe medical lasers.

Rare-earth ion doped lead- and cadmium-free bismuthate glasses

Rare-earth ion doped bismuthate (LZBB) glasses without traditional glass formers, lead and cadmium, have been attempted to prepare. In Er3+ doped LKBB glass system, Judd–Ofelt parameters Ω2, Ω4, and Ω6 have been derived to be 3.48×10−20, 9.47×10−21, and 1.01×10−20cm2, respectively, which shows a medium symmetry of the ligand field in the site occupied by Er3+ and a less covalent environment of Er3+. Effective 1.53μm fluorescence was recorded and the peak emission cross section is proved to be more than 9.0×10−21cm2, which is much higher than those in phosphate, silicate, germanate, and tellurite glasses and beneficial to achieving powerful stimulated emission of Er3+ in LZBB glass system. Pr3+, Tm3+, and Ho3+ doped LZBB glasses with the maximum phonon energy of only ∼600cm−1 are potential candidates for developing O-, S-, and U-band amplifiers and medical lasers.

Near-infrared emissions and quantum efficiencies in Tm 3+-doped heavy metal gallate glasses for S- and U-band amplifiers and 1.8 μm infrared laser

Intense 1.8 μm and efficient 1.48 μm infrared emissions have been recorded in Tm 3+-doped alkali-barium-bismuth-gallate (LKBBG) glasses with low phonon energies under the excitation of 792 nm diode laser. The maximum emission cross-sections for 1.8 and 1.48 μm emission bands are derived to be 6.26×10 −21 and 3.34×10 −21 cm 2, respectively, and the peak values are much higher than those in Tm 3+-doped ZBLAN glass. In low-concentration doping, the full-widths at half-maximum (FWHMs) of the two emission bands are 223 and 122 nm, and the quantum efficiencies of the 3F 4 and 3H 4 levels are proved to be ∼100% and 86%, respectively. When the doping concentration increases to 1 wt%, the quantum efficiency of the 3H 4 level is reduced to 60% due to the cross-relaxation processes in high-concentration doping. Efficient 1.8 μm infrared emission in Er 3+/Tm 3+-codoped LKBBG glass has also been achieved under the excitation of 970 nm diode laser, and the probability and the efficiency of non-radiative energy transfer from Er 3+ to Tm 3+ are as high as 354 s −1 and 58.4%, respectively. Efficient and broad 1.8 and 1.48 μm infrared emission bands indicate that Tm 3+-doped LKBBG glasses are suitable materials in developing S- and U-band amplifiers and 1.8 μm infrared laser.

Near-infrared emission character of Tm3+-doped heavy metal tellurite glasses for optical amplifiers and 1.8 µm infrared laser

Intense 1.8 µm and efficient 1.47 µm infrared emissions have been recorded in Tm3+-doped alkali–barium–bismuth–tellurite (LKBBT) glasses with lower phonon energies under the excitation of a 792 nm diode laser. The maximum emission cross-sections for the 1.8 and 1.47 µm emission bands are derived to be 6.643 × 10−21 and 3.551 × 10−21 cm2 and the peak values are obviously higher than those in Tm3+-doped ZBLAN fluoride and TBSN tellurite glasses, respectively. In low concentration doping, the full-widths at half-maximum (FWHMs) of the two emission bands are 206 nm and 109 nm, respectively, and peak intensity ratio between them is about 2. When the doping concentration increases to 1 wt%, the peak intensity ratio exceeds 7 and the quantum efficiency of 3H4 level is only 64.6% due to the cross-relaxation process [3H4, 3H6] → [3F4, 3F4], which benefits to achieve powerful 1.8 µm emission. The efficient and broad 1.8 and 1.47 µm infrared emission bands indicate that Tm3+-doped LKBBT glasses are suitable materials in developing S- and U-band amplifiers and 1.8 µm infrared laser.