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A spectroscopic study of the near-infrared emission (NIR) properties of Tm(super 3+) doped oxyfluroride glass ceramics are performed in order to investigate the partitioning of the dopant ions and the influence of the Tm(super 3+) location on the near-infrared NIR emissions. Two main bands centered at 1465 and 1800 nm were detected under excitation at around 780 nm in 0.1 and 1 mol% Tm(super 3+) doped glass ceramics.

1.3-mu m emission of Nd:LaF3 thin films grown by molecular beam epitaxy on LaF3 and CaF2 substrates, is reported.

A spectroscopic analysis of hetero- and homoepitaxial Nd3+-doped LaF3 thin films grown by molecular beam epitaxy is performed using two different orientations of CaF2 substrates, (111) and (110), for the heteroepitaxial structures. Results indicate the existence of one Nd3+ in the LaF3 layers grown on CaF2 substrates and that on CaF2(110) substrates, two similar Nd3+ centers are found.

A study was conducted on the effects of the host lattice on the optical properties of Rb1-xCsxCaF3 and RbCa1-xCdxF3 crystals doped with Ni2+ ions. Results show that changing matrix composition will alter emission band position and Ni2+ emitting level lifetimes in solid solutions. Results also indicate that changes in lattice parameters and matrix composition influence bands in Cs+, Ni2+ centers.

An Yb3+ to Tm3+ energy-transfer quantum yield close to one has been found in phase-separated yttrium-alumina silicate optical fiber preform glasses. Optical absorption, luminescence, lifetime measurements, and rare-earth concentration dependence have been performed to investigate the feasibility of efficient blue upconversion fiber lasers through convenient Yb3+ sensitation. Luminescence decay measurements have demonstrated the co-existence of two phases. One of the phases is characterized by an yttrium-rich composition. Most of the RE ions partition into the yttrium-rich phase and produce the intense upconversion emission. [ABSTRACT FROM AUTHOR]

In view of the emergence of wide ranging applications in the areas such as environmental monitoring, medical diagnostics, defense, security and sensing etc., it is indispensable to develop resourceful mid-infrared photodetectors. In this article, we present potential design considerations exploiting plasmonic effects in the conventional heterojunction mid-infrared detectors, optimized for their operation in 8-14 μm spectral range. Design issues concerning GaAs-AlGaAs based plasmonic photodetectors are investigated using modal expansion method (MEM) in conjunction with Rayleigh expansion. Simple but insightful fitting expressions useful for designing practical photodetectors are presented. The effects of crucial design parameters on the photodetector performance are discussed in detail. Using metallic grating based plasmonic element, about 20 fold absorption enhancement is predicted, which is comparable or greater than that recently reported for InAs (Quantum Dots) and GaInNAs (Quantum Well) detectors. Photodetector designs showing considerable improvement in the responsivity and the specific detectivity, compared to their nonplasmonic but otherwise identical counterpart are presented. [ABSTRACT FROM AUTHOR]

Positive optical gain around 5 cm-1 (∼21 dB/cm) has been observed in Er3+-doped Ba2NaNb5O15 single crystal using a pump and probe experimental setup. High power laser pulses at 532 nm have been used as the pump source in order to strongly populate the 4S3/2(2H11/2) levels of the Er3+ ions due to ground state absorption. Low signal beam cw laser radiation at 850 nm has been used as the probe beam to stimulate the emission associated with the 4S3/2(2H11/2)→4I13/2 electronic transition of the Er3+ ions. The process has been modelized as a four level system, and its population has been analyzed and simulated in order to study the gain dynamics. Optical amplification of the probe signal has been observed during the first 60 μs, which represents a good agreement between the measured lifetime of the 4S3/2(2H11/2) levels and the reported simulation. [ABSTRACT FROM AUTHOR]

The doping distribution of Tm3+ ions in a transparent oxyfluoride glass ceramic has been investigated. Optical absorption, luminescence, and excitation measurements have been performed in order to determine the environment in which Tm3+ ions and the infrared emissions they give rise to are located. An interesting result has been found: the main contribution to the 1465 nm emission (S band) is due to Tm3+ ions in the crystalline phase for low doping level. However, when the Tm3+ concentration is high the S-band emission comes from the small portion of Tm3+ that remains in the vitreous phase. It has been concluded that cross relaxation (CR) processes are responsible for the quenching of the S-band emission in the crystalline phase for high doping concentration. Lifetime measurements of the 3H4 level have also been taken and the probability of CR processes deduced. [ABSTRACT FROM AUTHOR]

The temperature dependence of the Nd3+→Yb3+ energy-transfer rate in the YAl3(BO3)4 nonlinear laser crystal has been investigated from the analysis of fluorescence decay curves recorded in the 10–600 K range. Three different regimes, independent on the dopant concentration, have been observed in the thermal behavior of the Nd3+→Yb3+ energy-transfer rate. By comparing experimental results with theoretical predictions based on the Dexter model [J. Chem. Phys. 21, 836 (1953)], the origin of these different regimes has been explained. In addition, the influence of temperature and of both Nd3+ and Yb3+ concentrations on the Nd3+←Yb3+ energy back-transfer rate has been also investigated, concluding that it is a migration-assisted energy-transfer process. Finally, the populations of both Nd3+ and Yb3+ metastable states achieved after continuous-wave Nd3+ excitation have been calculated and measured and results have been explained in terms of the thermal behavior of both forward- and back-transfer rates. [ABSTRACT FROM AUTHOR]

The optically active dopant distribution in a Tm[sup 3+]–Yb[sup 3+] doped silica based glass ceramic sample has been investigated. A systematic analysis of the upconversion fluorescence of the Tm[sup 3+]–Yb[sup 3+] codoped glass and glass ceramic has been performed at room temperature. Tm[sup 3+] and Yb[sup 3+] single doped glass and glass ceramics have also been included in the study. Upon infrared excitation at 790 nm into the [sup 3]H[sub 4] level of the Tm[sup 3+] ions a blue upconversion emission is observed, which is drastically increased in the Yb[sup 3+] codoped samples. A rate equation model confirmed the energy transfer upconversion mechanism. Based on these results, the temporal dynamic curves of the levels involved in the upconversion process, [sup 3]H[sub 4], [sup 2]F[sub 5/2], and [sup 1]G[sub 4] were interpreted in the glass ceramic samples. The contribution of the optically active Tm[sup 3+] and Yb[sup 3+] ions in the crystalline and in the vitreous phase of the glass ceramic was distinguished and the ratio of Tm[sup 3+] ions in the crystalline phase could be quantified for the 1 mol % Tm[sup 3+]–2.5 mol % Yb[sup 3+] glass ceramic. A surprising result was obtained for that concentration: the main contribution to the upconversion emission of the glass ceramic is due to Tm[sup 3+]–Yb[sup 3+] ions in the vitreous phase. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

An intense green upconversion emission due to a photon avalanche mechanism has been observed in Ho[sup 3+]–Yb[sup 3+] codoped fluroindate glasses, measured at 200 K, under excitation at around 750 nm. The influence of the Yb[sup 3+] concentration on the photon avalanche process has been studied. The pump power threshold of the avalanche mechanism decreases as the Yb[sup 3+] concentration is increased. A reduction by about a factor of 3 is observed from the 2.25 mol % Ho[sup 3+] single doped glass to the 2.25 mol % Ho[sup 3+]–2.25 mol % Yb[sup 3+] codoped glass. This effect has been related to an extra feeding of the [sup 5]I[sub 7] intermediate level of Ho[sup 3+] ions via Ho[sup 3+]→Yb[sup 3+] and Yb[sup 3+]→Ho[sup 3+] energy transfer and back transfer processes, respectively. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]