| Ultra-fast femtosecond laser has the characteristics of high time resolution,high peak power,low thermal effect.It has been widely used in the fields of precision machining,micro-imaging,optical communication and so on.With the rapid development of laser diodes,all-solid-state laser pumped by LD has become one of the most ideal ways to produce ultrashort pulse laser.Laser gain matrix is the core part of laser.In order to realize ultra-fast femtosecond laser operation,the laser gain matrix materials need to have wide emission spectrum,high thermal conductivity and emission cross section at the same time.In the study of new materials,Gd3+ions are doped into YAP laser crystals to form a new mixed-crystal GYAP crystal,which can improve the degree of disorder of the crystals and make the absorption and fluorescence spectra of the activated ions doped with the crystal non-uniformly widened.It is advantageous to realize ultra-fast laser operation.In this paper,the growth process and spectral properties of Nd:GYAP and Yb:GYAP crystals have been studied in detail,and laser experiments were carried out.The possibility of Nd:GYAP and Yb:GYAP crystals as good solid-state ultra-fast laser crystals is comprehensively evaluated.The main contents and achievements of this paper are as follows:1.The first chapter introduces the development of ultra-fast solid-state lasers,briefly describes the advantages and disadvantages of several common broadband laser crystals.and puts forward the research necessity of LD-pumped Nd-doped and Yb-doped ultrafast solid gain materials.It is also pointed out that the GYAP crystal is chosen as the basis of the study in this paper.2.The growth principle and process of GYAP crystal are introduced in detail.Several factors affecting the quality of crystal growth are discussed systematically.The high quality GYAP single crystal was successfully grown by Czochralski method using Al2O3,Y2O3,Gd2O3 with purity of 99.999%as raw materials.The structure of the grown GYAP crystal was characterized by XRD.The crystal structure was consistent with the YAP crystal structure,and the space group is the same as that of Pnma,no structural phase transition occurred during the growth and cooling process.3.The Nd:GYAP crystal was successfully grown by the Czochralski method.And the absorption spectra of the crystal were studied.The J-O intensity parameter,spontaneous radiative lifetime and spontaneous radiative probabilities of Nd:GYAP crystal were analyzed by Judd-Ofelt theory,the J-O intensity parameter of the Nd:GYAP crystal is?2=0.85×10-20cm2,?4=3.71×10-20cm2,and?6=4.13×10-20cm2.The fluorescence spectra of Nd:GYAP crystal have been measured.The emission cross section of the emission peak at 1079nm is9.02×10-20cm2,the half peak width is 46nm,and the corresponding lifetime of 4F3/2 energy level is 189.5?s.Compared with other Nd3+ion doped crystals,Nd:GYAP crystal has a wider emission bandwidth and higher emission cross section,which is beneficial to achieve ultra-fast laser output.At the same time,the laser experiment was carried out on the Nd:GYAP crystal.The b-cut Nd:GYAP crystal was used to obtain the continuous laser output at the 1.08?m spectral line.When the absorbed power was 7.03W,the maximum output power was 2.12W,and the corresponding slope efficiency was 34%.4.The Yb:GYAP crystal was successfully grown by the Czochralski method.The spectral characteristics of the crystal were systematically studied.The highest absorption peak of Yb:GYAP was found at 959nm and the absorption cross section was 1.09×10-20cm2.It is very suitable for pumping by InGaAs laser diode.The main emission band of Yb:GYAP crystal is950-1050nm,which corresponds to the transition between Yb3+ions 2F5/2/2 to 2F7/2 energy level,and its emission cross section is 1.18×10-20cm2 at 1051nm,Compared with Yb:YAP(0.6×10-20cm2),Yb:LuVO4(1.0××10-20cm2)and Yb:CGA(0.75×10-20cm2),Yb:GYAP crystal has a wider emission bandwidth,and the 2F5/2 level lifetime of Yb:GYAP crystal is 1.638ms.Then the laser experiment was carried out on the Yb:GYAP crystal.The b-cut Yb:GYAP crystal was used to obtain the continuous laser output at the 1?m spectral line.When the absorbed power was 5.82W,the maximum output power was 0.51W,and the corresponding slope efficiency was 23.5%. |
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