Magneto-optical Properties Of Ge-based Chalcogenide Glasses

Magneto-optical?MO?glasses have been widely used in telecommunication and high-power laser systems as MO isolators,MO switches,MO modulators,optical fiber current sensors and integrated optics due to their excellent properties,such as good optical uniformity,stable chemical properties and easy to fabricate large sizes.Chalcogenide glasses,as a kind of diamagnetic MO materials,possess low temperature coefficient and wavelength dispersion of the Verdet constant?V?.And they also have excellent infrared transmittance so they are good candidate for infrared MO materials with the development of Mid-infrared optoelectronic countermeasures technology.However,chalcogenide glasses have low V values,and the main contribution to obtained large V values in chalcogenide glasses have not been cognized clearly.For clarifying the influence factors of the glass compositional variation on V and pursuing large V values,the MO properties of chalcogenide glasses have been studied systematically in this paper.The interaction between some kind of high polarizability ions(Pb²⁺,In³⁺,Sb³⁺)and the glass parameters such as structure,band gap and V was investigated detailed.The relationship between the diamagnetic V and ion structure parametersl was established,which provided a guidance for further designing new materials with high V.Purification technique was also studied systematically,in order to realize the practical application of chalcogenide glasses.The C,H,O and other impurities ions are effectively eliminated by using a home-made purification system,and the high purity chalcogenide glasses with flat spectrum in mid-infrared band were obtained,which solves the key problems for the application of chalcogenide glass.The main contents of this dissertation are as follows:1.Firstly,the MO properties of GeS₂-Ga₂S₃ glasses were studied systematically.It is found that there is a good linear relationship between the V and the ion content,and V have a linear relationship with the increase of Ga³⁺ion content due to their high polarizability than Ge⁴⁺one.2.Then,GeS₂-Ga₂S₃-Y₂S₃?Y=In or Sb?glasses were prepared by introducing In³⁺/Sb³⁺ions which have larger polarization than Ga³⁺one's into GeS₂-Ga₂S₃ glass.The results show that the V increases linearly with the increase of the In³⁺/Sb³⁺ions,which demonstrates that the diamagnetic Verdet constant of the chalcogenide glasses is positively related to the content of the high-polarization ions.The theoretical calculation of the V based on becquerel formula was carried out,and the results show that the calculation values are in good agreement with the experimental results at the long wavelength where away from the ultraviolet absorption edge.The relationship between V and the ultraviolet absorption edge?^*was also verified.The results show that?^*has no simple relationship with V,demonstrated that?^*is not suitable for predicting V in chalcogenide glass.3.Furthermore,the MO properties of chalcogenide glasses containing Pb²⁺ions were studied.Two new glass systems,i.e.GeS₂-In₂S₃-PbI₂?GIPb?and GeS₂-Sb₂S₃-PbI₂?GSPb?glasses were designed.The glass-forming region diagram of these two new systems was determined firstly,and they are quiet different between these two diagram:in the GIPb system,the glass-forming region is mainly located at the high GeS₂ content region.While in the GSPb system,the diagram is mainly concentrated in the low PbI₂ content region.The results of thermal test show that the?T is all more than 100K for most compositions examined in these two series glass systems,which indicates that the thermal properties of these glasses are excellent.The MO properties of the glass were also examined.The largest diamagnetic Verdet constant(0.200 min·G^-1 cm^-1@980 nm),)is obtained in the 22.5GeS₂·67.5Sb₂S₃·10PbI₂ glass,which is about 33 times higher than that of the quartz material.4.In this paper,a new parameter,that is,average polarizability?_ave,was proposed.It was found that there is a good linear relationship between?_ave and V.This conclusion is important and useful.Because it facilitates the design of new materials.In addition,the temperature coefficient of V was also studied.Compared with paramagnetic materials,it is found that the V of chalcogenide glass can be regarded as a constant,and the wavelength dispersion of V is also smaller than that of paramagnetic glasses,which means the MO devices fabricated by chalcogenide glasses have low sensitivity to the drift of the temperature and wavelength.5.The purification techniques of chalcogenide glasses were studied systematically.The carbon impurities in S and Se raw materials were well removed by three-stage distillation process.The OH^-content in quartz tubes was significantly reduced by dehydroxyl technology.A purification installations based on Cl₂ were built and high purity chalcogenide glasses with flat transmission in middle infrared range were obtained,which solves the key problems for the application of chalcogenide glass.