Optical Properties And Applications Of Rare-earth Ions Doped Materials

The application of optical high-tech to security and laser protection fields hasalways being a hot topic. Frequency conversion and laser absorption materials dopedwith rare-earth ions are the most promising candidates for applications in such fields.With the development of our market economy, newly forgery techniques have beenproducing kinds of counterfeits. However, these situations bring opportunities andchallenges to the progress of anti-counterfeiting technology. Rare-earth dopedmaterials have more superior optical properties comparing with other materials. Itwould be very important to the stability and development of our economy, if we couldcombine these materials with optical anti-counterfeiting technologies and develop anew kind of detection equipment. Furthermore, with the universal application ofmodern laser weapons and laser detection technologies, information war is key to thediscovery, aim, lock and destruction areas of modern war. Anti-discovery, anti-aimand anti-lock are the preerquisites of anti-destruction. Consequently, the developmentof novel laser protection materials is a pressing issue. Rare-earth doped materials thatcan absorb lasers of various wavelengths and dramatically reduce reflectance with thehelp of their abundant energy levels would have great potential applications in laserprotection.In this thesis, several synthesis methods of rare-earth ions doped material arefirstly introduced with an emphasis on the high-temperature solid-state reaction andnew microwave heating process methods. Based on the microwave heating theory andthe coupling effects between graphite and microwaves, the rare-earth doped materialswith low dielectric loss were synthesized. A microwave coupling insulation apparatusis designed to realize microwave-conventional hybrid heating. It can also improve theheating uniformity while keeping insulation.By conventional high-temperature solid-state reaction, two anti-counterfeitcoatings doped with Nd³⁺and co-doped with Er³⁺/Yb³⁺, respectively, weresynthesized. Their structure and photoluminescence mechanisms were analyzed, andthe anti-counterfeiting features were also verified by a new security instrument madeby ourselves. The results indicated that these coatings were more covert than others,because their exciting and emitting lights were both in the near infrared （NIR） region,which were invisible to by human eyes. Besides, they were also a kind of multiple anti-forgery coatings very convenient for use as well. These make them a kind of veryuseful and novel anti-counterfeit product.The new microwave heating method is applied to synthesize anti-counterfeitmaterials. Using the self-made instrument mentioned above, CaF2: Er³⁺/Yb³⁺wassynthesized for the first time in a microwave furnace. The X-ray diffraction （XRD）test results verified that RE³⁺ions have been successfully doped into CaF2lattice. Theformation mechanism was explained by ponderomotive theory and the up-conversionemission spectrum was analyzed in detail as well. We found that its red emission ismuch stronger then the green and explained the reason of it. Afterwards, potentialapplications of the synthesis method and as-prepared material in anti-counterfeitingfield are discussed.The new microwave heating meathod is applied to synthesize laser protectionmaterials. Rare-earth doped ultra-fine powders with low reflectance at several wavenumbers were synthesized in our microwave heating apparatus. Relationships amongreflectance, RE³⁺concentration and hearting time were discussed. By mixing thepowders with coatings, the property of strong absorption could be transplanted tothem. Experiments of spectral reflectance, temperature and laser ranging wereperformed. The results verifed that these coatings could achieve excellent laserprotection. These findings may have potential applications in the fields of laserprotection and camouflage.