The stark energy level split of (2F7/2, 2F5/2) of ytterbium ion in glasses are derived from room temperature absorption and emission spectra. It is shown that the stark energy split increases as the base varies from phosphate to tellurite glasses, and the first and second stark energy levels lay in range of 150 - 250 cm-1, 350 - 450 cm-1 over ground, the first over ground has smaller energy and thus larger Boltzmann heat effect and is difficult in lasing at this terminal level. The second level is 350 cm-1 over ground and can be considered as the terminal level whose lasing wavelength varies from 1000 nm to 1020 nm. The partition function ratio of the upper and lower levels of ytterbium ion is calculated and more accurate reciprocity equation by which emission cross section is determined from absorption spectra is obtained from stark energy levels.
A detailed analysis is presented of the possibility of an Er3+ and Pr3+ codoped fiber as an amplifier for 1.3 and 1.5 μm transmission windows. The numerical models with 1010/1480 nm and 986/1480 nm pump lasers are proposed, the rate and power propagation equations are solved numerically, and the dependence of the gains at 1310, 1530, and 1600 nm windows on pump wavelength and power, active ion concentrations, and signal wavelength are calculated. The results show that with 1010/1480 nm pumps of 200/100 mW and with fixed Pr3+ and Er3+ concentrations at 8.0×1024 and 2.0×1024 ions/m3, the signals at 1310 and 1530 nm windows may be equally amplified with a gain of 26.0 dB in the active fiber with a length of 7.0 m, and with a 1480/986 nm pump power of 100/300 mW and Pr3+ and Er3+ ion concentrations of 2.0×1024 and 2.0×1024 ions/m3, the signals at 1310 and 1530 nm may be nearly equally amplified with a gain of 8.0 dB in a 10.0 m long active fiber.
A macroporous silica with azimuthally shifted double-diamond frameworks has been synthesized by the self-assembly of an amphiphilic ABC triblock terpolymer poly(tert-butyl acrylate)-b-polystyrene-b-poly(ethylene oxide) and silica source in a mixture of tetrahydrofuran and water. The structure of the macroporous silica consists of a porous system separated by two sets of hollow double-diamond frameworks shifted 0.25c along ⟨001⟩ and adhered to each other crystallographically due to the loss of the mutual support in the unique synthesis, forming a tetragonal structure (space group I41/amd). The unit cell parameter was changed from a = 168 to ∼240 nm with c = √2a by tuning the synthesis condition and the wide edge of the macropore size was ∼100 to ∼140 nm. Electron crystallography was applied to solve the structure. Our studies demonstrate electron crystallography is the only way to solve the complex structure in such length scale. Besides, this structure exhibits structural color that ranged from violet to blue from different directions with the bandgap in the visible wavelength range, which is attributed to the structural feature of the adhered frameworks that have lower symmetry. Calculations demonstrate that this is a new type of photonic structure. A complete gap can be obtained with a minimum dielectric contrast of 4.6, which is inferior to the single diamond but superior to the single gyroid structure. A multilayer core–shell bicontinuous microphase templating route was speculated for the formation of the unique macroporous structure, in which common solvent tetrahydrofuran in hydrophobic shell and selective solvent water in hydrophilic core to enlarge each microphase sizes.
In this paper the fluorescence quantum efficiencies and branch ratios of ytterbium doped oxide glasses are firstly calculated with equation derived from the reciprocity principle. It is shown that using absorption spectra of ytterbium doped glasses including borate, phosphate, niobosilicate, telluorogermanate and tellurite glasses, the fluorescence quantum efficiencies are obtained and varies from 80% to 99%, increasing with decreasing phonon energy of glass hosts. The branch ratios change slightly as glass hosts with different phonon energy and are about 40%, 30%, 30%, 0% around 970 nm, 1000 nm, 1020 nm, 1050 nm wavelength, respectively.
AlInP commonly serves as the window layer in high bandgap III-V solar cells where it is responsible for reducing surface recombination by reflecting minority carriers. It must be optically transparent and conductive to majority carriers, and so is typically thin, 25 nm, and doped. It is the semiconductor layer most exposed to the environment during operation, which consists of high temperature and concentrated light in a terrestrial concentrating system. In this paper, the oxidation of AlInP was studied as it relates to III-V terrestrial solar cells. The effects of heat, humidity, and light were investigated. Undoped AlInP samples in a light-soaked, damp heat condition grew more than 20 nm of oxide in 2400 hours, as compared to 3 nm of oxide when in the same damp heat condition without light. Under the light-soaked, damp heat condition, n-type material oxidized faster than p-type material. These effects are indicative of a photoelectrochemical oxidation reaction between the semiconductor and an electrolyte, which is provided by the humidity in this case. The removal of UV light by the use of UV absorbing glass reduced much of this additional oxidation. The removal of humidity and UV limited oxide growth to 1.2 nm after 700 hours exposure. Although direct exposure of AlInP caused oxidation, GaInP solar cells utilizing n-AlInP windows were directly exposed to light and damp heat for over 2800 hours and found stable, an effect attributed to differences between n-AlInP window layers and n-AlInP epilayers.
We report the transmission and reflection properties of graphene-SiO2, graphene-Si interface with normal incidence. We analyze the real and imaginary parts of Graphene in a broad wavelength range 0.5–4.0 µm and use both Fresnel theory and Finite-difference Time-domain (FDTD) numerical simulations to calculate the transmittance and reflectance. The theoretical and numerical results show that the transmission and reflection on the interfaces mentioned above have a anormal phenomenon. The physical mechanism for anormal phenomenon is analyzed. Between 100 nm and 500 nm wavelength, the transmission and the reflection of graphene-SiO2 layer and graphene-Si layer have some sharp change. When the wavelength is more than 500 nm, the transmission and reflection of the two layers mentioned above have been a regular curve without sharp change. The transmission and reflection of the graphene layers is the order of 1.0, zero, respectively. These findings can pave new way for the active optoelectronic devices.
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