High temperature Raman spectra was recorded in this paper.The phase transition of β BaB 2O 4(BBO),a widely used crystal and potassium lithium niobate (KLN)crystal,a newly crystal was studied by the Raman spectra.The ...High temperature Raman spectra was recorded in this paper.The phase transition of β BaB 2O 4(BBO),a widely used crystal and potassium lithium niobate (KLN)crystal,a newly crystal was studied by the Raman spectra.The phase transition temperature of BBO from β BaB 2O 4 to α BaB 2O 4 was confirmed to be about 927℃ and 500℃ of KLN from ferro electric phase to para electric phase.It was observed that the change of the distribution of Ba 2+ and the change of the structure of [B 3O 6] 3- rings were important symbols of the phase transition of BBO.The finger peak (629cm -1 )belonged to [B 3O 6] 3- rings still existed when the temperature was up to 1400K.This indicated that the basic growing unit of BBO was[B 3O 6] 3- rings not atoms.The phase transition of KLN was mainly due to the position shifting of all the particles at the transition point.The movement of Li + ions had great influence on the vibration modes in the crystal. The relation between the phase transition and the efficiency of frequency doubling was also studied.It was often observed that when the power of the incident light was increased to a certain degree,the conversion efficiency was no longer increased.This mainly because the phase transition temperature of the crystal was lower and phase transition occurred in the crystal.展开更多
Potassium Lithium Niobate (KLN) crystal belongs to tetragonal system and is ferroelectric crystal,which point group is 4mm and space group is P4bm .The melt point of KLN crystal is about 1050℃.KLN crystal possesses t...Potassium Lithium Niobate (KLN) crystal belongs to tetragonal system and is ferroelectric crystal,which point group is 4mm and space group is P4bm .The melt point of KLN crystal is about 1050℃.KLN crystal possesses tungsten bronze structure and its structure general expression is(A 1) 2(A 2) 4C 4(B 1) 2(B 4) 8O 3.KLN crystal is full fill up tungsten bronze structure crystal,in which the light of transmission band is 0.35-5.0μm.KLN crystal has excellent electro optical and nonlinear property and is superior double frequency crystal material for blue light.KLN crystal also is acoustic surface wave and photorefractive material.KLN crystal cracks easily during it grows.But when KLN crystal is doped in Mn 2O 3 to grow Mn∶KLN crystal,the crystal crack is reduced and the photorefractive property of the crystal is enhanced.KLN system is solid solution system and not congruent composition.The compounding ratio of Mn∶KLN crystal which we grew is 47.4mol% Nb 2O 5,17.3mol% Li 2CO 3,35mol% K 2CO 3 and 0.1mol% Mn 2O 3.The purity of Nb 2O 5,Li 2CO 3,K 2CO 3 and Mn 2O 3 is all 99.99%.Czochralski method was used to grow Mn∶KLN crystal.The technical parameters include the axial direction temperature gradient,the crystal growth rate and the rotation rate.Mn∶KLN crystal with 6mm×8mm×20mm size was grown in the condition that the axial direction temperature gradient is 30℃-40℃,the crystal growth rate is 0.5mm/h and the rotation rate is 10-15r/min.KLN crystal is one dimension ferroelectrics crystal.It has a paraelectrics ferroelectrics phase transition point curie point.So the crystal needs to be polarized in manual work.The direct current field was used to force the self polarization Ps in the same direction and the crystal turn to single domain.Before polarization,the c face needs to be confirmed exactly.The platinum pole was pasted to the two surfaces of c face and the direct current voltage about 220V was added the pole as the polarization outer electrical field.The polarization temperature is 460℃ and the polarization current density is 2mA/cm 2 .The thermal analyzer in TAS100 model was used to analyze the thermal expansion character of Mn∶KLN crystal and ascertain that the curie point of Mn∶KLN crystal is 435℃.It can be seen from the measurement result that the change of thermal expansion rate of Mn∶KLN crystal is smaller than that of pure KLN crystal. So doping Mn 2O 3 in KLN crystal to grow Mn∶KLN crystal can reduce the crack of the crystal.展开更多
Potassium Lithium Niobate (KLN) crystal can be written as K 2Li 2- x Nb 5+ x O 15+2 x (0.1< x <0.5) in general formula.KLN crystal po ssesses tungsten bronze structure.All the 12 and 9 exponent coordinate are ta...Potassium Lithium Niobate (KLN) crystal can be written as K 2Li 2- x Nb 5+ x O 15+2 x (0.1< x <0.5) in general formula.KLN crystal po ssesses tungsten bronze structure.All the 12 and 9 exponent coordinate are taken place by K + while C site in 9 exponent coordinate is taken place by Li +.KLN crystal is full fill up tungsten bronze crystal.Even if KLN crystal has been i r radiated with hard laser,it would be stable.The twin crystal,unpolarization and multidomain structure cannot appear in KLN crystal when it is in use.KLN cryst al shows excellent electric optical rotation and nonlinear optical property.Fe:K LN crystal was grown using Czochralski method by doping Fe 2O 3 in KLN and pol arized.Using two wave coupled technology,the photorefractive property of Fe:KLN crystal was researched by measuring the erasure curve.The crystal was irradiated by Ar + laser which wavelength is 488.0nm and polarization state is in e p olarization. I 10 and I 20 is signal light and reference light respectively,2 θ ,the angle between the two beam is 48.2° and β 0 ,the initial intensity ratio of the two beams is 100.The direction of e light p o larization parallels c axial of Fe:KLN crystal.First make I 10 and I 20 irradiate the crystal and the grating was recorded.Then block one beam and only one beam was used to irradiate the crystal at the same time, the d iffractive light intensity was recorded in the signal light transmission directi on and turned to electrical signal.We gained the erasure curve of holography gra ting by the computer processing the dependence of time and voltage.The erasure t ime which definition is that the time needed by diffractive light intensity deca ying to its final stable diffractive light intensity (minimum value) achieve 1/ e of the time difference between the initial diffractive light intensity (ma ximum) and the final diffractive light intensity was calculate by voltage taking place the diffractive light intensity.Following lists the erasure time of holog raphic grating of Fe:KLN crystal in different reference light:展开更多
文摘High temperature Raman spectra was recorded in this paper.The phase transition of β BaB 2O 4(BBO),a widely used crystal and potassium lithium niobate (KLN)crystal,a newly crystal was studied by the Raman spectra.The phase transition temperature of BBO from β BaB 2O 4 to α BaB 2O 4 was confirmed to be about 927℃ and 500℃ of KLN from ferro electric phase to para electric phase.It was observed that the change of the distribution of Ba 2+ and the change of the structure of [B 3O 6] 3- rings were important symbols of the phase transition of BBO.The finger peak (629cm -1 )belonged to [B 3O 6] 3- rings still existed when the temperature was up to 1400K.This indicated that the basic growing unit of BBO was[B 3O 6] 3- rings not atoms.The phase transition of KLN was mainly due to the position shifting of all the particles at the transition point.The movement of Li + ions had great influence on the vibration modes in the crystal. The relation between the phase transition and the efficiency of frequency doubling was also studied.It was often observed that when the power of the incident light was increased to a certain degree,the conversion efficiency was no longer increased.This mainly because the phase transition temperature of the crystal was lower and phase transition occurred in the crystal.
文摘Potassium Lithium Niobate (KLN) crystal belongs to tetragonal system and is ferroelectric crystal,which point group is 4mm and space group is P4bm .The melt point of KLN crystal is about 1050℃.KLN crystal possesses tungsten bronze structure and its structure general expression is(A 1) 2(A 2) 4C 4(B 1) 2(B 4) 8O 3.KLN crystal is full fill up tungsten bronze structure crystal,in which the light of transmission band is 0.35-5.0μm.KLN crystal has excellent electro optical and nonlinear property and is superior double frequency crystal material for blue light.KLN crystal also is acoustic surface wave and photorefractive material.KLN crystal cracks easily during it grows.But when KLN crystal is doped in Mn 2O 3 to grow Mn∶KLN crystal,the crystal crack is reduced and the photorefractive property of the crystal is enhanced.KLN system is solid solution system and not congruent composition.The compounding ratio of Mn∶KLN crystal which we grew is 47.4mol% Nb 2O 5,17.3mol% Li 2CO 3,35mol% K 2CO 3 and 0.1mol% Mn 2O 3.The purity of Nb 2O 5,Li 2CO 3,K 2CO 3 and Mn 2O 3 is all 99.99%.Czochralski method was used to grow Mn∶KLN crystal.The technical parameters include the axial direction temperature gradient,the crystal growth rate and the rotation rate.Mn∶KLN crystal with 6mm×8mm×20mm size was grown in the condition that the axial direction temperature gradient is 30℃-40℃,the crystal growth rate is 0.5mm/h and the rotation rate is 10-15r/min.KLN crystal is one dimension ferroelectrics crystal.It has a paraelectrics ferroelectrics phase transition point curie point.So the crystal needs to be polarized in manual work.The direct current field was used to force the self polarization Ps in the same direction and the crystal turn to single domain.Before polarization,the c face needs to be confirmed exactly.The platinum pole was pasted to the two surfaces of c face and the direct current voltage about 220V was added the pole as the polarization outer electrical field.The polarization temperature is 460℃ and the polarization current density is 2mA/cm 2 .The thermal analyzer in TAS100 model was used to analyze the thermal expansion character of Mn∶KLN crystal and ascertain that the curie point of Mn∶KLN crystal is 435℃.It can be seen from the measurement result that the change of thermal expansion rate of Mn∶KLN crystal is smaller than that of pure KLN crystal. So doping Mn 2O 3 in KLN crystal to grow Mn∶KLN crystal can reduce the crack of the crystal.
基金This work was supported by Heilongjiang Province Science Foundation。
文摘Potassium Lithium Niobate (KLN) crystal can be written as K 2Li 2- x Nb 5+ x O 15+2 x (0.1< x <0.5) in general formula.KLN crystal po ssesses tungsten bronze structure.All the 12 and 9 exponent coordinate are taken place by K + while C site in 9 exponent coordinate is taken place by Li +.KLN crystal is full fill up tungsten bronze crystal.Even if KLN crystal has been i r radiated with hard laser,it would be stable.The twin crystal,unpolarization and multidomain structure cannot appear in KLN crystal when it is in use.KLN cryst al shows excellent electric optical rotation and nonlinear optical property.Fe:K LN crystal was grown using Czochralski method by doping Fe 2O 3 in KLN and pol arized.Using two wave coupled technology,the photorefractive property of Fe:KLN crystal was researched by measuring the erasure curve.The crystal was irradiated by Ar + laser which wavelength is 488.0nm and polarization state is in e p olarization. I 10 and I 20 is signal light and reference light respectively,2 θ ,the angle between the two beam is 48.2° and β 0 ,the initial intensity ratio of the two beams is 100.The direction of e light p o larization parallels c axial of Fe:KLN crystal.First make I 10 and I 20 irradiate the crystal and the grating was recorded.Then block one beam and only one beam was used to irradiate the crystal at the same time, the d iffractive light intensity was recorded in the signal light transmission directi on and turned to electrical signal.We gained the erasure curve of holography gra ting by the computer processing the dependence of time and voltage.The erasure t ime which definition is that the time needed by diffractive light intensity deca ying to its final stable diffractive light intensity (minimum value) achieve 1/ e of the time difference between the initial diffractive light intensity (ma ximum) and the final diffractive light intensity was calculate by voltage taking place the diffractive light intensity.Following lists the erasure time of holog raphic grating of Fe:KLN crystal in different reference light:
