The Fabrication And Property Investigation Of Ion-Implanted Waveguides In Optical Glasses

Optical waveguide is a basic structure in integrated optics, as signal propagationchannels and equipments connected some devices with others. It plays an importantrole in the fabrication of various optical devices because of its excellentcharacteristics, possibility in integration and rather low cost in manufacturing. Theresearchers are always exploring the effective methods to fabricate waveguidespossessed excellent performances. Ion implantation is one of the most importanttechniques for modifying surface properties, and it has been proved to be animportant method to fabricate waveguides, owing to its superior controllability andreproducibility. In addition, ion implantation is not limited to the Curie temperature ofsubstrate materials. During implantation processes, the losses of incident ions includetwo different kinds of physical mechanisms called nuclear energy deposition andelectronic energy deposition. Those energy depositions would cause the distortion ofthe substrate material near the surface region and induce the variation of refractiveindex. At the end of the ion range, an optical barrier with a relatively low refractiveindex compared with the substrate is formed by the nuclear energy deposition.Meanwhile, refractive index would increase or be slightly disturbed between the airand the optical barrier, which is mainly decided by electronic energy deposition. Thepropagation light would be well confined by air and optical barrier in opticalwaveguide. Therefore, we can control the ion species, energies, doses andpost-annealing treatments to fabricate valuable waveguides.The ion implanted waveguide technology is sorted to two different strategiesnamed light-ion implantation and heavy-ion implantation, according to the mass ofimplanted ions. The ions used in the light-ion implantation are protons or Helium ions,however, the ions used in the heavy one usually are C+, O+and Cu+etc. The light-ionimplantation requires higher dose than the heavy-ion implantation to form waveguidestructures. In some materials, fluence of only10¹³ions/cm²magnitude is sufficient forthe heavy-ion implanted waveguide formation. Most optoelectronics devices such as optical coupler, modulator, optical switchand waveguide laser are based on channel waveguide structures. The attempt offabrication of such waveguide structure is necessary for both optoelectronicstechnology itself and the combination between nuclear technology andoptoelectronics.In this dissertation we report the waveguide formation and characterization onYb³⁺-doped silicate glasses, Er3+/Yb³⁺co-doped silicate glasses, Yb³⁺-dopedphosphate glasses, and Nd3+-doped phosphate glasses. The prism coupling method isused to measure the dark mode spectra of the implanted waveguides. The end-firecoupling system is carried out to obtain the near-field profile and the propagationlosses of the waveguides. The refractive index profile is reconstructed using the ICMor RCM simulation packages. The formation mechanism of the waveguides isdiscussed to some extent. The absorption and fluorescence spectra of the part of thewaveguide samples are investigated to obtain the relative information. The channelwaveguide is fabricated by ion implantations plus the photolithography process inYb³⁺-doped silicate glasses. The main results are given as follows:Yb³⁺-doped silicate glasses are interesting as diode-pumped, tunable andultrafast high-power laser sources because of their broad absorption （850¹100nm）and emission band-widths （900¹200nm） and low thermal loading. The absorptionband is located at about970nm, with a large cross-section, which enables efficientpumping by high power Ⅲ-Ⅴdiode lasers that are commercially available. Comparedwith Yb³⁺-doped phosphate and borate glasses, Yb³⁺-doped silicate glasses have theirown benefits such as stable physical and chemical properties, low cost, and possiblefused coupling with silica fibers.（1） We have demonstrated the fabrication of planarwaveguides in Yb³⁺-doped silicate glasses by （470.0+500.0） keV proton implantationat the doses of （1.0+2.0）×10¹⁶ions/cm². By combining damages and the ion exchangebetween the proton and Na+ions, we illustrate the formation of the optical barrier andpoint out that the dose of proton is an important factor to obtain excellent waveguidelasers.（2） Optical planar waveguides are fabricated in Yb³⁺-doped silicate glasses by（450.0+500.0+550.0） keV helium ion implantation at the doses of （2.0+2.0+2.0） ×10¹⁶ions/cm². The refractive index profile of the planar waveguide is reconstructedby ICM, which shows a typical “enhanced well+optical barrier” distribution. Bycombining the compaction effect and the influence of nonbridging oxygens, weillustrate the formation of the “enhanced well”.（3） We have examined the fabricationof monomode optical planar waveguides in Yb³⁺-doped silicate glasses by4.0MeV Cion implantation at a fluence of2.0×10¹⁴ions/cm². The guided modes are measuredusing a model2010prism coupler at633nm. The near-field profiles of the planarwaveguide are obtained with an end-face coupling system. The refractive indexprofile of the waveguide is reconstructed by the intensity calculation method.（4） Theplanar waveguide has been fabricated in the Yb³⁺-doped silicate glass by6.0MeVO³⁺ion implantation at a dose of6.0×10¹⁴ions/cm². The guiding properties arecharacterized by the prism-coupling and end-face coupling methods with a He-Nebeam. The dark-mode spectra and near-field intensity distribution are measuredbefore and after annealing at250oC for1h in air. The SRIM’2006code is carried outto simulate the energy loss during the implantation in order to obtain a betterunderstanding of the waveguide formation. The refractive index profile of the planarwaveguide is reconstructed by the reflectivity calculation method. The results indicatethat the thermal treatment can enhance the propagation properties with preserving theeffective refractive indices well.Erbium （Er3+）-doped optical materials and devices receive much attention fortheir capabilities of providing efficient gains in the telecommunication windowsaround a wavelength of1.55μm and their applications as eye-safe light sources. Wereport on the fabrication of planar waveguides in Er3+/Yb³⁺co-doped silicate glassesby6.0MeV carbon and oxygen implantation with a dose of6.0×10¹⁴ions/cm²,respectively. The guiding properties are measured by the prism-coupling and end-facecoupling methods with a He-Ne beam. The propagation losses are measured byback-reflection method. The refractive index profile of the planar waveguide isreconstructed by the reflectivity calculation method, which shows a typical “enhancedwell+optical barrier” distribution. The micro-luminescence investigation reveals thatfluorescent properties in the waveguide are well preserved with respect to the bulk, exhibiting possible applications for integrated active photonic devices.Yb³⁺-doped phosphate glasses have received much attention owing to theirintriguing properties and potential applications. Yb³⁺-doped phosphate glasses exhibithigh emission cross-section, broad absorption, emission band and long fluorescencelifetime （1-2ms）, making it particularly attractive to generate ultrashort pulses andtunable laser sources. We have reported on the fabrication of planar waveguides inYb³⁺-doped phosphate glasses by （450.0+500.0+550.0） keV helium implantation atthe fluences of （2.0+2.0+2.0）×10¹⁶ions/cm². We make a series of annealingtreatments from260oC to410oC to investigate the annealing properties of the planarwaveguide. We perform prism-coupling measurements of the He-implantedwaveguides after each annealing step at a wavelength of633nm. The near-fieldprofiles and propagation losses of the planar waveguides are obtained with anend-face coupling system. The barrier optical waveguides are also formed inYb³⁺-doped phosphate glasses by using （5.0+6.0） MeV O³⁺ion implantation at dosesof （4.0+8.0）×10¹⁴ions/cm². The dark-mode spectra, near-field profiles, refractiveindex distributions and propagation losses of the planar waveguide are measuredbefore and after annealing at300oC for1h in air. The results indicate that the thermaltreatment can reduce the densities of color centers and defects created during theimplantation process.The Nd3+-doped phosphate glass has received more and more attention owing toits application in both series high power laser devices used as the laser drived inertiaconfined fusion （ICF） and the optical communication. It has excellent laserperformances such as large emission cross-section, long fluorescence lifetime andacceptable thermal-physical properties. The typical barrier optical waveguides areformed in Nd3+-doped phosphate glasses by using （450.0+500.0+550.0） keV heliumimplantation at doses of （2.0+2.0+2.0）×10¹⁶ions/cm²and6.0MeV carbon andoxygen implantation with a dose of6.0×10¹⁴ions/cm², respectively. The guidingproperties of the waveguide are evaluated by the prism coupler and end-face couplingmethods. After the implantation, the sample is annealed to reduce the densities ofcolor centers and defects created during the implantation process. The propagation loss of the waveguide is measured to be less than1.0dB/cm, which means acceptablequality for further guide-wave applications. The micro-luminescence spectra of thewaveguide show fairly good potentials for laser action.Combining the photolithography technique, the channel waveguides arefabricated in Yb³⁺-doped silicate glasses by using （450.0+500.0+550.0） keV heliumion implantation at doses of （2.0+2.0+2.0）×10¹⁶ions/cm². The periodical structure ofthe channel waveguide has been obtained by SEM after implantation. The7.0μmwide channel waveguides distribution in good order, with a50.0μm interval betweenthe stripes. The near field profiles of the channel waveguides are measured through anend-face coupling system. The propagation loss of the channel waveguide ismeasured by the Fabry-Perot resonance method. As we know, channel waveguide isthe basis of many optoelectronics devices such as optical coupler, modulator, opticalswitch and waveguide laser, research on channel waveguide is necessary for practicalapplications.