Study On Er³⁺/Tm³⁺co-doped Ti:LiNbO₃ Waveguides And Related Material

The realization of Ti:Er:Tm:LN optical waveguide not only allows the combination of the emissions of both ions but also allows the utilization of the optical-damage-resistant merit of Tm³⁺dopants,which enables the development of the amplifier or laser operating at S+C+L band.The main work of dissertation is to fabricate Ti:Er:Tm:LN optical waveguide with Er/Tm co-doped.The work can be summarized as below:1.Characteristics of Er³⁺and Tm³⁺ions in LiNbO₃crystal with Er/Tm-codoped have been studied,which is as follows:The result shows Er3+/Tm3+co-doped have negligible contribution to Li₂O-content in the crystal plates and the major factor for Li out-diffusion is diffusion temperature.The Tm³⁺or Er³⁺ion diffusivity is the same for both single diffusion case and co-diffusion cases.The different Er and Tm metal films deposition thicknesses result in different solubility in the Tm³⁺/Er³⁺co-diffusion case,however,the total solubility of co-diffusion case is the same to the value in the single diffusion case.2.Crystalline phase,profile characteristics and spectroscopic properties of Er³⁺/Tm³⁺-diffusion-codoped LiNbO₃ crystal was investigated.The X-ray single crystal diffraction shows that Er³⁺and Tm³⁺ions are in the form of LN crystalline phase.The Er³⁺and Tm³⁺ions in crystals plate obey a Gaussian type and have a21.5?m diffusion depth.The surface Er³⁺and Tm³⁺ions concentration is evaluated as0.42±0.02,0.44±0.02 mol%.Both ions keep their respective spectroscopic features and do not affect each other.The Er³⁺and Tm³⁺co-doped enables combine the wavelength emissions of both ions and the resultant emission band around 1.5?m is as wide as 150 nm,which offers the possibility of S+C+L broadband amplication and laser by employing 980 nm and 795 nm laser diodes as the pump sources.3.Composition effect on Emission and absorption cross sections of Er³⁺only doped and Er³⁺/Mg²⁺-codoped LiNbO₃ crystals was studied.The results show that increasing Er³⁺concentration tends to decrease the cross section,while increasing crystal composition tends to increase the cross section.As the composition is close to the stoichiometry,the cross section value tends to a constant.In the Er³⁺/Mg²⁺co-doped case,the increasing Mg²⁺concentration tends to increase the cross section value.These effects are related to Er³⁺site redistribution in the crystal plates which was induced by doping or crystal composition alteration.4.A Z-cut Y-propagating and a X-cut Z-propagating Er³⁺/Tm⁴⁺co-doped Ti⁴⁺-diffused waveguide were fabricated and characterizations were performed:The surface Er³⁺/Tm³⁺concentration of waveguides is evaluated as 0.81/0.83×10²⁰atom/cm³?Z-cut?and 0.82/0.84×10²00 atom/cm³?X-cut?.The near-field pattern of guided mode show that the two waveguide support TM or TE single-mode propagation at the 1.547?m wavelength.Comparing the Er³⁺/Tm³⁺co-doped waveguide with the case of Er³⁺-only doped,there has a certain resistance to the optical damage for Er³⁺/Tm³⁺co-doped waveguide under 980 nm LD pumping because of the lower Tm³⁺doping concentration?0.43mol%?.The lower Tm³⁺doping concentration and the fewer the number of particles on³H₄ contribution to a smaller signal gain for the two waveguides.The maximum of signal enhancement is0.21dB/cm?Z-cut?and 0.51dB/cm?X-cut?.In the end,small signal's enhancement of1547nm wavelength under 980 nm or1480nm LD pumping and 795nm for 1450 nm were dynamically simulated in details,which can help us understand the evolutionary relationship between signal and pump light and to provide guidance on the theory and direction for Ti:Er:Tm:LiNbO₃ waveguide amplifier and laser system in the future.5.Ti⁴⁺-diffused Zr⁴⁺/Er³⁺-codoped waveguide was fabricated on an X-cut LiNbO₃substrate with Y-propagating.and the optical damage resistant was studied:Secondary ion mass spectrometry study shows that the Ti⁴⁺ions follow a sum of two error functions in the width direction and a Gauss function in the depth direction of the waveguide.Both Er³⁺ions and Zr⁴⁺ions profiles follow the Gauss function,which entirely cover the Ti⁴⁺profile.In the case of 980 nm pumping,the waveguide shows stable 1547 nm signal output under high pump level without optical damage observed,and a net gain of the 1.1 dB/cm is obtained for the available pump power of 120 mw.The study provides a reference for the improvement of photorefractive properties of the Er³⁺/Tm⁴⁺co-doped Ti⁴⁺-diffused waveguide.The innovation of this dissertation as follows:?1?Taking the lead in fabrication and comprehensive spectroscopic characterization of Er³⁺/Tm³⁺-diffusion-co-doped LiNbO₃ crystal with off-congruent.?2?Combination of Li-poor VTE,Er³⁺/Tm³⁺-co-doping and Ti diffusion treatments was first used to fabricate Ti:Er:Tm:LiNbO₃waveguide successfully.?3?The 795nm LD as the pump sources was first used to pump the Er³⁺/Tm³⁺in the waveguides and the 1450 nm small signal enhancement under 795 nm pumping was measured successfully.?4?Ti:Er:Zr:LiNbO₃ waveguide was fabricated for the first time and the photorefractive properties of the waveguide were studied,which provided a good platform for the development of integrated optics.