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Fluorescence of Tm3+/Er3+ codoped bismuth-silica (BS) glasses and the sensitization of Ce3+ are investigated. It shows that Ce3+ codoping with Tm3+/Er3+ in BS glasses results in a quenching of Tm3+ ion emission from 3F4 to the 3H6 level. Consequently, the 1.47 μm emission occurs after the population inversion between the 3H4 and 3F4 levels. Furthermore, the codoped glasses show the broad emission spectra over the whole S and C bands with full-width at half-maximum (FWHM) up to about 119 nm, as it combines 1.55 μm emission band of Er3+ with 1.47 μm emission band of Tm3+ under 800 nm excitation.

We investigate the upconversion luminescence of Er3+ and Tm3+ codoped tellurite glasses under both the 975 and 800 nm excitations. By Tm3+ codoping, the Er3+ green emission corresponding to the (4S3/2, 2H11/2)→ 4I15/2 transitions was quenched, while the red emission corresponding to the 4F9/2→ 4I15/2 transition was selectively sensitized. The red emission has a maximum in the range where the ratio of Er3+- to Tm3+-content is about two and its fluorescence intensity becomes 1.5 and 5 times larger at the maximum than those in the absence of Tm3+ for 975 and 800 nm excitations, respectively. The results were explained considering the influence of energy transfers between these two active ions.

We investigate optical near-field distributions of the unconventional C-apertures and the conventional square apertures in preliminary experiment with an aperture scanning near-field optical microscope. These nano-apertures are fabricated in Au film on a glass substrate with focused ion beam technology. The experimental results indicate the uptrend of output light intensity that a C-aperture enables the intensity maximum to increase at least 10 times more than a square aperture with same unit length. The measured near-field light spot sizes of C-aperture and square aperture with 200-nm unit length are 439 nm × 500 nm and 245 nm × 216 nm, respectively.

Evanescent wave interference is studied theoretically and experimentally. The interference patterns were directly measured with a scanning near-field optical microscope. The acquired image of the interference pattern is clear and has better contrast than that previously acquired with a photon-scanning tunnelling microscope or laser-trapped particles. The spatial period of the interference fringes is 180 nm, which agrees with the theoretical value. The results indicate that the probe of the scanning near-field optical microscope has a resolution beyond 100 nm. The relation between the evanescent field intensity and the distance is also measured. When the separation between the probe and the interface is up to 180 nm, the intensity can decrease to 1/e of the maximum.

The niobate phosphate glasses containing Eu3+ ions were fabricated by the melting method. The fluorescence characteristics of the glass at temperatures from 77 K to 700 K were investigated under the excitation of 488 nm light. The results show that the fluorescence intensity of Eu3+ ions first increases and then decreases as temperature increases. The temperature-dependent parameters of the crystal fields and the local structure surrounding Eu3+ ions were investigated and discussed from the situation of splitting energy level of 5D0-7F1. The results indicate that the distance of europium and oxygen become shorter with increasing temperature and the coordination number of Eu3+ ion is near 8, which does not change with temperature.

A novel method of codoping the Er3+, Yb3+, and Ho3+ ions in tellurite glasses is demonstrated to obtain a high efficiency of infrared-to-visible upconversion. Three intense emission bands observed in Er3+, Yb3+, and Ho3+ codoped tellurite glasses centred at 525, 547, and 657 nm correspond to Er3+: 2H11/2→4I15/2, Er3+: 4S3/2→4I15/2+Ho3+: 5S2(5F4)→5I8, and Er3+: 4S3/2→4I15/2+Ho3+: 5F5→5I8 transitions, respectively. No visible upconversion quenching phenomenon is observed when three rare-earth ions are codoped together in tellurite glasses. In contrast, the upconversion intensity of red and green emissions in Er3+, Yb3+, and Ho3+ codoped glasses is enhanced largely when compared with Er3+/Yb3+-codoped glasses. The dependence of upconversion intensities on excitation power and the possible upconversion mechanisms are evaluated. The three emissions are based on two-photon absorption processes.

Er2O3-doped bismuth silicate glasses are prepared by the conventional melt-quenching method, and the Er3+:4I13/2 →4I15/2 fluorescence properties are studied for different Er3+ concentrations. Infrared spectra are measured to estimate the exact content of OH- groups in the samples. Based on the electric dipole–dipole interaction theory, the interaction parameter CEr,Er for the migration rate of Er3+:4I13/2→4I13/2 in proposed glasses is calculated.

The random-phase approximation (RPA) of interacting fermions is recast into a bosonized form and the RPA results are rederived by the standard bosonization method, which shows that there is a natural connection between bosonization and RPA.

A series of new Er3+/Yb3+-codoped 70 TeO2–5 Li2O–(25-x)B2O3–xGeO2 (TLBG, x = 0, 5, 10, 15, 20 mol%) glasses are prepared. The thermal stability and spectroscopic properties of TLBG glasses are studied. It is found that these glasses have the better thermal stability ((Tx−Tg)>150 degrees C) compared with 75 TeO2–20 ZnO–5Na2O (TZN) glass. The fluorescence full width at half maximum (FWHM) is about 77 nm, while the emission intensity and the quantum efficiency of the 4I13/2 level of Er3+ increase with the increasing GeO2 content. The maximum quantum efficiency and stimulated emission cross-section of Er3+ calculated from the McCumber theory are 93.82% and 9.0×10−21 cm2, respectively. The products of FWHM and σepeak of Er3+ in TLBG glasses are larger than those in other reported glasses. The obtained data indicate that this kind of TLBG glasses is a promising candidate host material for Er3+-doped broadband amplifiers.

We propose a general method to prove the uniqueness of the inversion problems described by first-kind integral equations. The method depends on the analytical properties of the Fourier transform of the integral kernel and the finiteness of the total states (or probability, if normalized), the integration of the ``local'' density of states, which is a rather moderate condition and satisfied by many inversion problems arising from physics and engineering.