| As one of the greatest inventions of the 20th century,lasers have been widely used in agricultural,military and medical fields owing to its high spatial and temporal coherence,especically the mid-infrared laser in modern defense.The laser beam can be obtained directly from laser gain medium;however,the laser wavelengths obtained in this way have a limited range.One of the most efficient ways to obtain new laser is frequency conversion via second-order nonlinear optical(NLO)crystals and simulated Raman scattering(SRS)crystals.Meanwhile,the application of photoelectric devices in modulation,deflection and information processing were driven by the invention of laser.Recently,a series of compounds,including the transition metal cations(Mo6+,W6+,Ti4+,V5+,Nb5+,etc.)and the lone-pair electrons cations(Pb2+,Sb3+,Se4+,Te4+,I5+,etc.),have attracted the scientists' attention,since most of them have a strong frequency doubling effect.Crystals in noncentrosymmetrical structure exhibits anisotropy of physical properties,like nonlinear optics,electric-optic,piezoelectric properties,as well as the special linear optics,laser,and magneto-optics.In recent years,our group have been engaged in exploring novel photoelectric-function quaternary oxides that containing Te4+ and Mo6+/W6+.Since the introduction of heavy atoms Te and Mo/W makes a wider transmission band.In addition,the large band gap of these oxides enables larger laser threshold,which has application prospects in high power frequency conversion.In recent years,we have devoted huge efforts to the research on the series of crystals containing tellurium and molybdate/tungstate.Bulk ?-BaTeMo2O9(?-BTM)has been grown for the first time in 2008 by our group,and its optical properties,Raman properties,piezoelectric properties,and electro-optic properties have been systemically studied.The results show that ?-BTM is a potential multifunctional crystal.In the course of growing large dimensions of ?-BTM crystal,a new polymorph a-BaTeMo2O9(a-BTM)was discovered.The systemically studies on physicochemical properties indicate that a-BTM is a potential photoelectric crystal.On the other hand,there are also some shortcomings in these crystals:1)Color mutation in ?-BTM;2)Mixed crystal and inclusion in ?/?-BTM crystals;3)Lack of studies on the growth mechanism and photoelectric devices based on these crystals.In this thesis,the growth of large-sized ?/?-BTM crystals with high quality,the growth mechanism and photoelectric devices based on these crystals were carried out.The main contents and conclusions are as follows:?.Optimizations on the growth system for ?/?-BTM,growth mechanism,and growth and gain boundary characterization in dual-phasic BTMLarge-sized ?-and ?-BTM in high quality have been obtained by optimizing the growth parameters,including concentration,temperature field,cooling speed,seed-orientation.Transparent crystals of ?-/?-BTM with dimensions of 105×77×27 mm3 and 51×48×43 mm3,respectively,were obtained.The as-grown ?-BTM crystals using[100]-,[010]-,and[001]-orientated seeds have comparable quality,with optical homogeneity of 10-5.The solubility of ?-/?-BTM in the flux system TeO2-MoO3(TeO2:MoO3=1.2:1)was measured.Results show that the saturation temperatures of both polymorphs BTM in the same solution are almost the same,indicating that both ?-/?-BTM can be grown from a same solution.Viscosity of the solution was measured,as well as the similarities in structure between ?-BTM and ?-BTM,the two seeds oriented along the[100]?-BTM and[010]?-BTM direction or the(204)?-BTM and(012)/?-BTM planes were tied together to perform multi-seeds growth.Comprehensive characterizations have been performed on the dual-phase BTM.The lattice mismatch rate gives us the direction for the coherent grain boundary,and the first-principle calculation on free energy exhibits the rearrangement of the eutectic layer,forming O5Mo-O-MoO5 bipyramidal structure.In addition,Laue diffraction and SEM make sure that ?-and ?-BTM grew together rather than being simply attached to each other by the flux.?.The design and fabrication of the polar prism by biaxial ?-BTMPolar prism based on biaxial ?-BTM crystal was designed and fabricated since its wide transmission and large birefringence.At first,the feasibility of the biaxial crystal for polar prism was theoretically analyzed;the origin of the birefringence for a-BTM has been calculated and interpreted on the basis of the crystal structure combined with theoretical studies.Furthermore,polarized prism based on a-BTM covered the mid-infrared region was designed and characterized.The extinction ratio was up to 30000:1,which would satisfy the practical requirements.And the optimization on the design,the structure and field angle with the spectral characteristic were performed.Then the Wollaston-prism was designed using a-BTM and systemically characterized.The results show that the a-BTM is a promising material for polarized prism in high quality and broadband.III.The acousto-optic(AO)modulator made by biaxial BTM crystalsA novel biaxial a-BTM crystal is deem to be a promising AO medium,and the validity and feasibility of the biaxial crystals as AO mediums have been theoretically analyzed and confirmed by experiments.The design optimization of the modulator based on the a-BTM crystal has been carried out before the fabrication.This work provides a relatively simple technique for making accurate,direct measurement of the figure of merit of a-BTM crystal,which is obtained to be 10.18 ×10-18 s3/g.Then an AO Q-switch device made of the biaxial a-BTM crystal was fabricated and characterized for the first time with the electrode layer using Au of a thickness of 2.52?m,the bonding layer using tin of a thickness of 4.93 ?m and the thickness of piezoelectric transducer of 35 ?m.At a radio frequency signal of 100 MHz,the diffraction angle and diffraction efficiency of the a-BTM AO Q-switch were determined to be 1.432° and 82.1%,respectively,with a minimum pulse width of 8 ns,which could satisfy the requirements of practical experiments.The results with the insensitivity to the polarization of the incident light show that this biaxial a-BTM crystal is a promising material for acousto-optic devices.Since ?-BTM crystal exhibits excellent piezoelectric properties,to avoid the influence of the piezoelectric effect of this ?-BTM crystal on the A/O interaction,the propagation of acoustic wave along X axis is selected for the poorest piezoelectricity according to the matrix of piezoelectric constant.Then ?-BTM was fabricated as an AO modulator and characterized.The diffraction angle and diffraction efficiency are determined to be 1.420° and 78.1%,the sensitivity of the polarization may be influenced by the higher asymmetry.The minimum of the modulated pulse width can be achieved to be 6 ns,which can satisfy the practical requirement of the experimental.?.Raman shift combined with AO modulation on a ?-BTM crystalA more compact AO ?-BTM Raman laser driven by a pulsed laser diode(LD)pumped Nd:YVO4 laser for the first time based on the Raman and AO performance of the ?-BTM.the maximum pulse energy of 46 mW at 1178.12 nm was obtained with the absorbed LD pump energy of 9 W,giving an optical-to-optical conversion efficiency of 5.2 ‰,and a slope conversion efficiency of 7.5 ‰.The pulse output characteristics of the AO ?-BTM Raman laser were analyzed detailly. |
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