Material dispersion evaluation in a fluoride glass

We report for the first time experimental evaluation of the material dispersion in a fluoride glass. Very interesting features are observed as the wavelength of zero material dispersion is around 1.7 ?m and the disperison is about only 45 ps/nm × km at a 4 ?m wavelength.     

Mechanical durability of ZBLAN and aluminum fluoride-based opticalfiber

Zero stress aging and static fatigue experiments were performed on fluoride glass fibers of ZBLAN and aluminum fluoride-based compositions to examine the mechanical durability in aqueous solutions. ZBLAN fiber, which has the higher initial strength, becomes weaker than initially lower strength aluminum fluoride-based fiber in less than one hour in pH 7 buffer solution at 30°C. This is shown to be due to dissolution of the glass and precipitation of crystals at the glass/coating interface. In 1N NaOH the solubility is higher, resulting in less precipitation and hence less strength degradation. Although ZBLAN fiber degrades more quickly when a high strain is applied, at low applied strain the residual strength is higher than is observed when do strain is applied. These results indicate that future work on fluoride glass fibers for use in aqueous environments should focus on optimization of the as-drawn strength of durable glass, such as aluminum fluoride-based material, rather than on making small strength improvements to already strong but less durable glass, since such improvements will be quickly lost in aggressive environments     

Fabrication and characterisation of fluoride-glass single-mode fibres

We report on the fabrication and characterisation of a fluoride glass fibre single-moded at 2.4 ?m. From chromatic dispersion measurements we deduced with a very good accuracy the material dispersion curve of the core glass between 1.1 ?m and 2.1 ?m.     

Low-OH-absorption fluoride glass infra-red optical fibres

Ultralow losses of 10?2 to 10?3 dB/km have been predicted in fluoride glass optical fibres between 2 and 4.5 ?m. At 2.9 ?m, in the central part of this spectral region, the OH? ion presents its fundamental stretching vibration which gives rise to a strong and broad absorption. The attenuation at 2.9 ?m in a step-index fluorozirconate glass fibre has been brought down to 58 dB/km, by reducing the OH? concentration in the glass. It is the lowest attenuation yet reported at this wavelength in any optical fibre.     

34 Mbit/s optical fibre transmission system experiment at a wavelength of 2.4 ?m

Data transmission at 34 Mbit/s has been performed over a fluoride glass fibre at a wavelength close to the 2.55 ?m minimum-loss wavelength of the fibre, using an externally modulated He-Ne laser and a graded-composition GaInAs photodiode with spectral response optimised for 2.55 ?m operation.     

Material dispersion in fluoride glasses

Material-dispersion measurements are reported on fluoride glass for infra-red optical fibres. Bulk glasses prepared by the conventional casting method were measured in the 0.4?4.3 ?m wavelength range. Observed zero-material-dispersion wavelengths were 1.62 ?m for BaF2-GdF3-ZrF4 glass and 1.48 ?m for BaF2-CaF2-YF3-AlF3 glass.     

Transmission properties of 2.55 ?m fluoride glass fibre

Data transmission and bandwidth measurements have been performed on a fluoride glass fibre at the 2.55 ?m minimum loss wavelength of the fibre, using a colour centre laser and an external waveguide modulator. Fibre modal dispersion limited the fibre bandwidth to 360 MHz.     

High-power 10%-tuning-bandwidth varactor-controlled impatt oscillator/amplifier

A simple electronically tuned c.w. GaAs impatt/varactordiode oscillator/amplifier circuit is described which can be tuned over a 10% bandwidth at mid-X-band frequencies at a power level greater than 0.5 W as an oscillator, and greater than 0.8 W at the 6 dB-gain level as a reflection amplifier. Unambiguous electronic tuning without power jumps, frequency hops or `out-of-band? oscillations has been achieved by paying special attention to the circuit design.     

Material dispersion in lightguide glasses

Material dispersion measurements are reported on six characteristic lightguide glass compositions. The measurements were made on bulk specimens and cover the wavelength range from 0.8 to 1.5 ?m. It is observed that in these silicate glasses the wavelength at which material dispersion is zero is in all cases greater than 1.2?m.     

Transmission loss characteristics of fluoride glass single-mode fibre

The transmission loss spectrum of a fluoride glass single-mode fibre as obtained with a new preform fabrication technique is shown. It is clearly confirmed on the loss spectrum that the obtained fibre is a single-mode waveguide in the minimum loss wavelength range (2?4 ?m). The minimum loss of this fibre is 8.5 dB/km at 2.2 ?m and the OH excess loss is 15dB/km at 2.85 ?m. This fabrication technique is effective in eliminating OH contamination.     

Laser emission of Er+3 in ZrF4-based fluorideglass

Laser emission is reported in an Er⁺³-doped ZrF₄ -based fluoride glass often referred to as `heavy metal fluoride glass' (HMFG). The laser operates at room temperature at a wavelength of 2.78 μm. The glass is a standard ZBLAN formulation in which all of the LaF₃ (4 mol.%) is replaced by ErF₃. Glass preparation, spectroscopy and laser data are presented and discussed     

基于非线性色散补偿光栅的可调谐光电振荡器

为实现光电振荡器(OEO)输出频率的连续可调,提出一种新型的基于非线性色散补偿光栅(FBG)实现可调谐OEO方案。本文方案不需要电滤波器,且振荡频率随着光源的波长变化而变化。其中,三阶色散补偿FBG可以采用FBG重构算法设计。当光源波长从1 550.6nm变化到1 551.4nm时,相应的色散为340～1 460ps/nm,输出频率的调谐范围为6.5～13.5GHz,实现了振荡频率的大范围可调谐。     

Low-dispersion fluoride glass single-mode fibres operating in twospectral ranges

Chromatic dispersion characteristics of fluoride glass single-mode fibres are investigated experimentally and theoretically. It is proposed that the quasi-single-mode operation at zero material dispersion wavelength is effective in extending the low dispersive spectral range. It is shown that total chromatic dispersion is suppressed within ±1 ps/km/nm in the two spectral ranges of 1.57-1.71 μm and 2.4-3.35 μm     

Zero material dispersion in optical fibres

The material dispersion of optical fibres having cores of silica or phosphosilicate glass falls to zero at a wavelength between 1.2 and 1.3 ?m. A considerable increase in bandwidth can be obtained, especially with an l.e.d. source, by operation in this region.     

Fabrication of SU-8 microreactors for radiopharmaceutical production

SU-8 is a very interesting material for the fabrication of lab-on-chip devices applied to organic synthesis because of its resistance to chemicals and solvents. Among the possible application fields of microreactor technology, radiochemistry is emerging because microfluidic apparatuses allow to perform radiosynthesis in a quicker, safer and more reliable way compared to traditional vessel-based approaches. Microreactors for synthesizing [¹⁸F]-labelled radiopharmaceuticals require the employment of materials that do not adsorb fluoride and are resistant to solvents and chemicals. Pyrex, glass and silicon adsorb fluoride ions, therefore they are not the best choice. SU-8 is stable towards chemicals and solvents but nothing is known about its behaviour with radioactive fluoride. Here we develop a simple fabrication procedure to make fully coated SU-8 microreactors and we demonstrate the potentiality of SU-8 microfluidic architectures to be used for radiosynthesis, giving a proof of their low tendency to trap radioactive fluoride if compared with traditional glass microchannels.     

Prediction of loss minima in infra-red optical fibres

Loss minima in two fluoride glass and chalcogenide glass fibres were calculated. The intrinsic losses are predicted to be 1 × 10?3 dB/km at 3.4 ?m for BaF2-GdF3-ZrF4 glass fibre, 1 × 10?2 dB/km at 2.7 ?m for BaF2-CaF2-YF3-AlF3 glass fibre and 1 × 10?2 dB/km at 4.5 ?m for GeS3 glass fibre.     

光谱辐射计波长定标新方法的研究

在空间、野外等环境下光谱辐射计常常需要进行波长定标,通常的室内定标法无法满足其要求,为此,本文通过对稀土氧化物中氧化铒与氧化镝的光谱特性和稳定性的研究,认为它们非常适合作为光谱辐射计波长定标参考板的主要材料,该种参考板的研制成功将改变现有波长定标仅能在室内进行的限制,从而解决了不同环境要求波长定标的难题。本参考板也可作为室内波长定标的标准。     

Influence of waveguide dispersion in fluoride glass fibres

The dispersive properties of step-index fluoride glass fibres have been evaluated using a computer model. The results show that, by a suitable choice of core diameter and index difference in these materials, the dispersion can be reduced to zero over a broad wavelength range.     

Study of Raman free-electron laser oscillator with Bragg reflectionresonators

A high-gain Raman free-electron laser oscillator is realized by using a Bragg reflection resonator with a limited pulse duration of the electron beam (0.4 MeV/800 A. 60 ns). The practical design of the Bragg reflectors is introduced. A concept of hybrid oscillator configuration which combines the high gain of a superradiant amplifier with the narrow bandwidth of a conventional oscillator (Fabry-Perot resonator) is put forward and is confirmed by experimental results. It shows that 14 MW peak power at 7.7 mm wavelength (bandwidth Δλ/λ<5%) with a 4.4% electronic efficiency is produced. The measured fundamental wavelength of the radiation spectrum is compared with the result of calculations