?-ray irradiation effect on transmission loss for ZrF4-based optical fibres

The ?-ray irradiation effect on the transmission loss of ZrF4-BAF2-GdF3-AlF3 and ZrF4-BaF2-GdF3-AlF3-PbF2 optical fibres is investigated. Absorption bands are induced in the ultraviolet to near infrared region, and their tails increase the transmission losses in the mid-infrared region. Induced transmission losses for a dose of 106 R are 1000?2300 dB/km in the 2?4 ?m band. These values are comparable to those at 1.5 ?m for doped silica fibres.     

Design optimisation of erbium-doped fibres for use in L-bandamplifiers

An analysis based on numerical simulations of the optimum erbium-doped fibre (EDF) design for use in L-band amplifiers is presented. The efficiency of the EDF is found to peak at a cutoff wavelength of ~1100 nm, when operated in an L-band amplifier. The gain per length increases monotonously with the cutoff wavelength independent of numerical aperture     

Lasing at 1.00 mu m in erbium-doped fluorozirconate fibres

Continuous-wave lasing has been obtained at 1.00 mu m in erbium-doped fluorozirconate fibres. This laser operates as a three-level system. Data concerning saturation of absorption at 488 and 514.5 nm, and absorption and fluorescence from the lasing level are also reported.<>     

Investigation and optimisation of fusion splicing abilities between erbium-doped optical fibres and standard singlemode fibres

Fusion splice loss between erbium-doped fibres (EDFs) and standard singlemode fibre is discussed. Special attention is paid to the wavelength dependence of splice loss. It is suggested that, for a conventional EDF step index profile, it is difficult to meet both common EDF cutoff requirements and minimising wavelength dependence at the same time. Therefore, a new refractive index profile is suggested. With this design an actual fibre has been made to demonstrate how splice loss as well as wavelength dependence can be reduced.     

Behavior of Bragg gratings, written in germanosilicate fibers,against γ-ray exposure at low dose rate

Bragg gratings have been written within four germanosilicate fibers either by a pulsed or by a continuous-wave exposure of each fiber to a coherent UV two-beam interference pattern. These gratings have been exposed under steady state conditions to γ-ray doses as high as 10 ⁴ Grays. The dose rates ranged between 10 Gy/h and 1.3×10² Gy/h. The transmission spectra of the fibers have been recorded during and after the ⁶⁰Co irradiation, near the grating Bragg wavelengths. Whereas the induced loss reached 600 dB/km near 1.3 μm, no significant change in the spectral characteristics of the gratings could be detected within the experimental accuracy, enabling their future use in a nuclear environment     

Spectral tuning and linewidth narrowing of shallow-junction surface emitting GaAs LED́s through γ-ray irradiation

Alterations of device characteristics as a result of γ-ray irradiation of shallow-junction surface emitting devices are different from those of deep-junction devices with respect to LED emission intensity reduction, I-V curve, line shape, and spectral shift. In particular, much larger spectral shifts in the opposite direction-toward longer wavelengths-are reported here than those found in the literature for deep-junction devices. A qualitative model based upon photochemical doping and changes in surface band bending is proposed to explain these phenomena. Changes in surface emitting shallow-junction optical radiation source device characteristics brought about by γ-ray irradiation are desirable ones for utilization in most optical fiber communication systems. These changes include linewidth narrowing, decreased time response, and decreased material dispersion because of the emission wavelength change.     

Induced γ-ray emission

The extension of optical maser techniques to the γ-ray region is considered. It is shown that under certain conditions induced γ rays can be produced. The condition of criticality rather than that of oscillation is used because a γ-ray maser does not have a resonant structure. The main observable effects are the shortening of lifetimes of some γ excitations and the appearance of two or more coherent γ quanta. It appears to be difficult to prepare samples that will become critical. The principles are applied to a specific example.     

γ-radiation-induced attenuation in photonic crystal fibre

Results are presented of what, to the knowledge of the authors, is the first study of the sensitivity of a photonic crystal fibre (PCF) under steady-state gamma irradiation. Radiation-induced attenuation of a PCF has been measured at 1.55 μm. This new type of fibre showed a higher attenuation level than a standard monomode fibre but had a fast kinetic of recovery after irradiation     

Enhancement of photoluminescence of structures with nanocrystalline silicon stimulated by low-dose irradiation with γ-ray photons

The spectra of infrared transmittance and photoluminescence of thin-film nc-Si/SiO₂ structures containing nanocrystalline silicon (nc-Si) and subjected to ionizing radiation (⁶⁰Co) in the dose range D= 10⁴?10⁷ rad are studied. It is shown for the first time that low radiation doses (5 × 10³ rad < D < 10⁵ rad) lead to significant (as large as 40%) increases in the intensity of the photoluminescence band at 1.33 eV. The infrared spectra indicate that there is no variation in the composition and structure of the nanocomposite. The observed effect is accounted for by structural ordering of the nanocrystal-matrix interface; this ordering is stimulated by low-dose irradiation, i.e., removal of defects (recombination centers) at the nc-Si/SiO₂ interfaces and resulting enhancement of the radiative-recombination channel.     

三种聚合物光纤γ射线辐照光谱特性实验研究

分析了聚合物光纤在辐照环境下的物理化学变化，实验研究了聚甲基丙烯酸甲脂（PMMA）.聚碳酸脂（PC）、聚苯乙烯（PS）三种光纤在不同剂量的γ射线辐照下的辐照损伤效应，测量了三种聚合物光纤在可见光波段的辐照光谱。测量结果表明，光纤的辐照损伤和恢复都有波长相关性，在0.1kGy和1kGy辐照剂量时，三种光纤的透过率光谱趋势类似，整个可见光波段透过率光谱都较平坦；在5kGy和10kGy辐照剂量时，测得的辐照光谱在不同波长段出现峰值，辐照剂量越高剂量率越大，光谱的峰值效果越明显，透过率起伏越多，透过率峰值也向长波段偏移     

高精度光纤陀螺用掺铒光纤光源辐照性能试验

针对高精度光纤陀螺的空间应用,理论分析了用于高精度光纤陀螺的不同结构掺铒光纤光源的抗辐照性能,指出了单通后向结构的掺铒光纤光源具有更好的抗辐照性能。对单通后向结构采用不同掺杂浓度的掺铒光纤设计并研制了掺铒光纤光源,在实验室用Co60辐照源进行了大小两个剂量率的辐照试验,监测了掺铒光纤光源平均波长和输出光功率随辐照总剂量的变化,试验结果表明:掺铒光纤掺杂浓度较高时,掺铒光纤光源的抗辐照能力较强;辐照剂量率较小时,掺铒光纤光源功率随辐照总剂量的降低速度更慢。掺杂浓度较高的掺铒光纤光源可以满足高精度光纤陀螺空间应用的要求。     

Improvement of diamond X-ray mask membrane: Optical transmittance, surface roughness and irradiation durability

A viable method for the improvement of the polycrystalline diamond X-ray mask membrane is proposed. The use of an ionized cluster beam yields the smoothest surface. Sol-gel planarization film coating with indium tin oxide is the most effective method for obtaining high optical transmittance without sacrificing high synchrotron irradiation durability.     

γ射线、β射线诱变固体DNA的发射光谱研究

利用发射光谱研究固体脱氧核糖核酸(DNA)经γ射线、β射线诱变后结构的变化。图谱显示出：11312．2nm、9901．0nm和9363．3nm诱变后消失；12722．6nm、12345．6nm和9090．9nm诱变后减弱：7668．7nm、6553．0nm和5966．6nm诱变后增强。说明经过γ射线、β射线辐照后，DNA碱基受损，主链断裂，双螺旋结构遭到破坏，失去了其复制、转录的生物学功能，     

Spectral gain hole-burning at 1.53 μm in erbium-doped fiberamplifiers

Spectral gain hole-burning at λ₀=1.53 μm was observed in an erbium-doped fiber amplifier at temperatures between 4.2 and 77 K. The hole width was found to broaden with temperature for T ⩾20 K according to a T^1.73 law. From the data, the room-temperature homogeneous linewidth associated with the 1.531-μm transition in the ⁴I_13/2-⁴I_15/2 laser system was determined to be Δλ_h=11.5 nm for aluminosilicate fibers     

β射线、γ射线诱变固体DNA 的拉曼光谱分析

利用拉曼光谱仪得到了固体DNA在β射线、γ射线诱变前后的拉曼光谱。实验结果表明：经过β射线、γ射线诱变以后，归属于腺嘌呤(A)的1304cm^-1和1340cm^-1频率发生了改变；归属于胸腺嘧啶(T)、胞嘧啶(C)的786cm^-1、归属于脱氧核糖磷酸盐链的884cm^-1、归属于脱氧核糖(d)中C-O的对称伸缩振动1010cm^-1强度有不同程度的减弱；归属于C-O伸缩振动的1068cm^-1和归属于脱氧核糖的1468cm^-1消失；分析认为：DNA经过β射线、γ射线的诱变后，脱氧核糖的振动、脱氧核糖磷盐链的振动以及C-O的伸缩振动都会发生不同程度的减弱；硷基和胸腺嘧啶发生变化；与DNA垂直的硷基-硷基相互作用遭到破坏。     

Intensification of electroluminescence of ZnSe:(Te,O) crystals as a result of irradiation with γ-ray photons

The effects of irradiation with γ-ray photons of the ⁶⁰Co isotope and of treatment in zinc vapors on the electroluminescence of ZnSe:(Te, O) crystals were studied with the aim of revealing the potential for fabrication of light-emitting structures. The broadband electroluminescence with a peak at 600 nm is excited in the initial samples at voltages higher than 70 V. The threshold voltage is decreased to several volts irrespective of polarity after treatment of the crystals in zinc vapors. A similar effect is observed after irradiation. The position of the peak in the electroluminescence band does not depend on the magnitude of voltage or on irradiation. This position is related to the recombination of charge carriers at the centers of interstitial zinc according to the mechanism of excitation of the prebreakdown type. Treatment in zinc vapors and irradiation with γ-ray photons of ZnSe:(Te, O) bring about an increase in the electroluminescence intensity at both polarities of applied voltage.     

Energy recycling versus lifetime quenching in erbium-doped 3-μmfiber lasers

Based on recently published spectroscopic measurements of the relevant energy-transfer parameters, we performed a detailed analysis of the population mechanisms and the characteristics of the output from Er ³⁺-singly-doped and Er³⁺, Pr³⁺-codoped ZBLAN fiber lasers operating at 3 μm, for various Er³⁺ concentrations and pump powers. Whereas both approaches resulted in similar laser performance at Er³⁺ concentrations <4 mol.% and pump powers <10 W absorbed, it is theoretically shown here that the Er³⁺-singly-doped system will be advantageous for higher Er³⁺ concentrations and pump powers. In this case, energy recycling by energy-transfer upconversion from the lower to the upper laser level can increase the slope efficiency to values greater than the Stokes efficiency, as is associated with a number of Er³⁺-doped crystal lasers. Output powers at 3 μm on the order of 10 W are predicted     

Design of erbium-doped triangular photonic-crystal-fiber-based amplifiers

The amplification properties of erbium-doped triangular photonic crystal fibers (PCFs) are analyzed by varying the pitch, the hole diameter, and the dopant radius by means of a full-vector finite-element modal formulation combined with a population and propagation rate equation solver. Fiber designs which allow us to greatly reduce splice losses are presented and it is demonstrated that PCF amplifiers may deliver gains of more than 47 dB with splice losses lower than 0.3 dB.     

A novel ASE self-pumping technique for gain-enhanced L-band erbium-doped fiber amplifiers

A novel method of enhancing gain in long-wavelength-band erbium-doped fiber amplifiers is described using the unwanted amplified spontaneous emission (ASE) self-pumping technique. The unwanted ASE from a first stage amplifier is recycled into a second stage amplifier as a secondary pump. Gain improvements in the vicinity of 0.4 and 1.2 dB are obtained in the wavelength range of 1570–1600 nm. This enables support for higher channels in multiwavelength systems with negligible noise figure penalties.     

1.58-μm band gain-flattened erbium-doped fiber amplifiers forWDM transmission systems

This paper describes the amplification characteristics of gain-flattened Er³⁺-doped fiber amplifiers (EDFAs) by using 0.98-μm and 1.48-μm band pumping for a 1.58-μm band WDM signal. Silica-based Er³⁺-doped fiber (S-EDF) and fluoride-based Er ³⁺-doped fiber (F-EDF) have gain-flattened wavelength ranges from 1570 to 1600 nm and from 1565 to 1600 nm, respectively, and exhibit uniform gain characteristics with gain excursions of 0.7 and 1.0 dB, and the figure of merit of the gain flatness (gain excursion/average signal gain) of 3 and 4.3%, respectively, for an eight-channel signal in the 1.58-μm band. We show that 1.48-μm band pumping has a better quantum conversion efficiency and gain coefficient, and that 0.98-μm band pumping is effective for improving the noise characteristics. We also show that the EDFAs consisting of two cascaded amplification units pumped in the 0.98-μm and 1.48-μm bands are effective in constructing low-noise and high-gain 1.58-μm band amplifiers