Bi-doped Crystals Research Articles

Ultra-broadband and enhanced near-infrared emission in Bi/Er co-doped PbF2 laser crystal

A Bi/Er co-doped PbF2 laser crystal was successfully grown. The use of Er3+ co-doping for enhancing the near-infrared emission in Bi/Er co-doped single crystal was obtained for the first time, to the best of our knowledge. The results show that compared with the single Bi-doped crystal, in Bi/Er co-doped PbF2 crystal, Er3+ can act as an effective charge compensation ion to promote the conversion from Bi2+ to Bi+, which would effectively enhance the NIR fluorescence emission of the Bi/Er doubly doped PbF2 crystal. Besides, it was demonstrated that two different Bi-related active centers (Bi (I) and Bi (II)) located around the NIR fluorescence emission peak of 1015 and 1080 nm. The results above strongly suggest that Bi/Er co-doped laser crystal may be an attractive gain host for developing NIR solid-state lasers.

Recent Advances in Super Broad Infrared Luminescence Bismuth-Doped Crystals.

SummaryBismuth (Bi)-doped materials are capable of exhibiting broadband near-infrared (NIR) luminescence in 1,000–1,700 nm; driven by the potential use in lasers and broadband optical amplifiers for modern fiber communication systems, Bi-activated NIR luminescencent glasses and related devices have attracted much attention. Compared with glass systems, Bi-doped crystals as gain media usually have more regular crystal structures to produce stronger NIR signals, and developing such materials is highly desirable. Regarding the recent advances in Bi-doped NIR crystals, here, for the first time, we summarized such crystals listed as two main categories of halogen and oxide compounds. Then, by comparing the substitution site, coordination environment, emission and excitation luminescence peaks, emitting center species, and decay times of these known Bibased NIR crystals, discussion on how to design Bi-doped NIR crystals is included. Finally, the key challenges and perspectives of Bi-doped NIR crystals are also presented. It is hoped that this review could offer inspiration for the further development of Bi-doped NIR luminescent crystals and exploit its potential applications.

Bandgap Narrowing in Bi-Doped CH3NH3PbCl3Perovskite Single Crystals and Thin Films

Single crystals of heterovalent Bi-doped CH3NH3PbCl3 perovskite have been successfully grown through the inverse temperature crystallization method. Bandgap narrowing of 300 meV (a 55 nm red-shifting absorption edge) is obtained for the nominal 20% Bi-doped crystal with the host structure and the energy at the top of the valence band invariable. It is observed that the contact between the Au electrodes and single crystals transforms from Ohmic to Schottky, and the conductivity increases with increasing Bi doping level. By contrast, the Bi-doped CH3NH3PbCl3 thin films are also prepared, and the similar bandgap narrowing is found, although the narrowing degree is less than that in single crystals. This work has a comprehensive understanding of Bi-doped single crystals and thin films, providing further optoelectronic applications for these promising solution-processed hybrid perovskite semiconductor materials.

Broadband NIR photoluminescence from Bi-doped Ba_2P_2O_7 crystals: Insights into the nature of NIR-emitting Bismuth centers

We report on a novel type of Bi-doped crystal that exhibits ultrabroadband photoluminescence in the near infrared (NIR). Emission centers can be generated and degenerated reversibly by annealing the material in CO atmosphere and air, respectively, indicating that emission is related to the presence of Bi-species in low valence states. Correlating static and dynamic excitation and emission data with the size and charge of available lattice sites suggests that two types of Bi(0)-species, each located on one of the two available Ba(2+) lattice sites, are responsible for NIR photoemission. This is further confirmed by the absence of NIR emission in polycrystalline Ca(2)P(2)O(7):Bi and Sr(2)P(2)O(7):Bi. Excitation is assigned to transitions between the doubly degenerated ground state (4)S(3/2) and the degenerated excited levels (2)D(3/2), (2)D(5/2) and (2)P(1/2), respectively. NIR emission is attributed to (2)D(3/2)?(4)S(3/2). The NIR emission center can coexist with Bi(2+) species. Then, also Bi(2+) is accommodated on one of the two Ba(2+)-sites. Energy transfer between Bi(2+) ions occurs within a critical distance of 25.9 A.

Growth and properties of CdTe:Bi-doped crystals

CdTe:Bi crystals were grown by the vertical Bridgman method, varying the nominal Bi-dopant concentration in the range of 1×10 17–1×10 19 at/cm 3. Bi and Bi 1.8−2.3Te precipitates are the most characteristic structural defects in these crystals. Raman spectroscopy studies have shown that Bi traps Te from the CdTe host lattice. Low-temperature photoluminescence in the 1.2–1.6 eV energy region is presented. Several new emissions related to the incorporation of Bi are observed. Semi-insulating CdTe was obtained ( ρ=2×10 10 Ω cm) for dopant concentration of the order of 1×10 17 at/cm 3. The resisitivity decreased to values as lower as 1×10 5 Ω cm for higher concentrations. Photosensitivity studies show an evolution from typical conductivity to shallow acceptor defects-related conduction when the Bi concentration is increased.

Simulation and characterization of CdTe:Bi crystals grown by the Markov method

CdTe pure and Bi-doped crystals were grown by the Markov method using an insulating element between the ampoule and the furnace. The numerical simulation performed shows that the presence of a graphite element causes a diminution of the axial temperature gradient, reducing the natural convection inside the growth chamber. This leads to a more stable growth process, improving the crystal quality. Morphological surface studies, Raman spectroscopy and photoluminescence mapping, support our prediction about the improved crystal quality when the graphite insulating element is included in the growth system. Its influence on different defects of the crystal is also discussed.

Laser characteristics of Cr:Nd:GdCOB self-frequency-doubling crystal

The phase matching angle of GdCOB crystal is calculated. By using Xenon flash lamp as pump source, we have realized the free run from 1.06 μm to 0.53 μm in self-frequency-doubling Cr:Nd:GdCOB (bi-doped) crystal and Nd:GdCOB (uni-doped) crystal. The experimental results show that the threshold energies for bi-doped crystal and uni-doped crystal are 0.92 J and 1.00 J, respectively; when the pump energy is 10 J, the output energies of green laser for two kinds of crystals are 2.46 mJ and 1.96 mJ, respectively. The output energy of Cr:Nd:GdCOB crystal has an increase of 25% in comparison to that of Nd:Gd:COB crystal. In addition, we discuss ways to improve efficiency.