Growth And Properties Of Nd:CNGS Crystals

Entering the new century, laser technology is driving the optoelectronic technology and industry development with its strong vitality. The systematic study in the scientific problem of the functional crystal materials which is the pivotal, basic and stimulated technology of the laser and optoelectronic technology has important strategic and realistic meaning to our country in the prospective high technology industry and national defense cons truction. Nowadays, the devices are increasingly demanded to be more compact, smaller and easier to adjust and use in the application of laser technology. Thus, the study of the composite function crystal materials that suited for all solid state miniature lasers has become a development direction and research hot spot in the field of crystal materials.CNGS (Ca3NbGa3Si2O14) is a kind of functional crystal with perfective piezoelectric property and good thermal and optical characters, which is suitable for laser materials. It could be used for all solid state miniature lasers if its various excellent properties were composited. However, there are no reports about CNGS crystals doped with active ions except for Co:CNGS until now, especially no report about Nd:CNGS which is important for laser application. If Nd3+ion could be doped into CNGS crystal, it would hopefully composite its various excellent properties, which is of great significance for the development of miniature laser devices.Based on the above purpose, the Nd3+ ion was doped into CNGS crystals and we got the new laser crystals of Nd:CNGS for the first time. The growth, structure and the basic physical properties of Nd:CNGS were systematically researched and the continuous wave laser outputs were realized. The main research contents of this thesis include:1. The growth of Nd:CNGS crystalsCNGS and Nd:CNGS with different doping concentration were grown by Czochralski method. The theory, process and technology of the crystal growth are presented in details, and the reasons of the crystal morphology were analyzed from two aspects of thermodynamics and dynamics combined with the law of the melt growth.2. The structure and basic physical properties of Nd:CNGS crystalsThe Nd3+ ion doping concentration of Nd:CNGS crystals were analyzed by X-ray fluorescence method, which showed that the doping concentrations were 0.483at.%(#4),0.920 at.%(#5),1.685 at.%(#6),1.722 at.%(#7) and 3.860 at.%(#8) respectively. The structures of CNGS and Nd:CNGS crystals were analyzed by X-ray powder diffraction method, and the second harmonic generation effect of Nd:CNGS crystals were found by using the crystal powder.The densities of CNGS and Nd:CNGS crystals were measured by the drainage method. The density of #4 Nd:CNGS crystal was measured to be 4.1348g/cm3 (the measuring temperature is 15℃), which is basically identical with the theoretical value of 4.146625g/cm3. The changes of the thermal expansion coefficient, specific heat and thermal diffusion coefficient with the temperature of CNGS and Nd:CNGS crystals were analyzed, the thermal conductivity was calculated. The thermal parameters of #4 Nd:CNGS crystal were analyzed in details, its linear thermal expansion coefficients are αx=6.98×10-6/K, αy=7.44×10-6/K, αz=6.77×10-6/K; the specific heat at room temperature is cp=0.604Jg-1K-1; the thermal diffusion coefficients are λx=0.68mm2/s, λy=0.70mm2/s, λz=0.897mm2/s; the thermal conductivities are kx=1.676W/m-K, ky=1.768W/m-K, kz=2.227W/m-K.The basic optical performances, including refractive index, optical activity, transmission, absorption and fluorescence properties, were systematically researched. The dispersion equations and curves of the refractive index and specific rotation were obtained by fitting, the refractive index no and ne of #4 Nd:CNGS crystal at 1065 nm wavelength are 1.772 and 1.854 respectively. The absorption of Nd:CNGS crystals were analyzed and the absorption cross-sections were calculated. The absorption cross-sections of#4 Nd:CNGS crystal around 800 nm and 804 nm are 6.14×10-20 cm2 and 6.08×10-20 cm2. The normal and polarized light fluorescence spectra of #4 Nd:CNGS crystal were measured, as well as the fluorescence lifetime. The emission cross-sections were also calculated, the emission cross-section in E//y around 1064nm and 1345nm are 6.81×10-20 cm2 and 3.13×10-20 cm2 respectively.In addition, the effects of the Nd3+ ion doping concentration to the various properties of Nd:CNGS crystals were systematically analyzed, which showed that the properties of Nd:CNGS crystals change regularity with the doping concentration of Nd3+ions.3. The laser performance of Nd:CNGS crystalsThe continuous-wave laser performances of Nd:CNGS crystal at 1065nm and 1345nm were realized. The maximum output power of the continuous-wave laser at 1065nm by 2mm, z tangential #4 Nd:CNGS crystal was 1.43W, optical-to-optical conversion efficiency was 29.3%, and a slope efficiency of 31.0% was achieved, the half-maximum value of the laser spectrum was 1.83nm. The maximum output power of the continuous-wave laser at 1345nm by 6mm, z tangential #4 Nd:CNGS crystal was 0.253W, optical-to-optical conversion efficiency was 5.6%, and a slope efficiency of 7.8% was achieved, the corresponding the half-maximum value of the laser spectrum was 1.14nm.Based on the above study, Nd:CNGS is a kind of laser crystal with good thermal and optical properties. Nd:CNGS crystal is easy to grow, its thermal properties are stable, its absorption and emission line are wide, which shows that Nd:CNGS crystal has good prospects in ultrashort pulse laser application. In addition, Nd:CNGS crystal may be widely used in optical modulators.