WANG Jun,ZHOU Feng-xian,LI Qian,HU Zhi-ping,DU Juan,LIU Zheng-zheng,ZHANG Ze-yu,LENG Yu-xin
Abstract：Perovskite materials and devices have obtained great progress due to their significant optoelectronic properties. Especially， quasi-two-dimensional（2D） halide perovskites have shown promising potential in optoelectronic devices due to their large exciton binding energy， strong exciton-photon coupling and enhanced stability. Moreover， the naturally quantum-well structure of 2D perovskite allows exciton energy transfer from the small-n phase to large-n phase， promoting exciton utilization and population inversion to achieve lasing as optical gain media. Herein， we will introduce the crystal structure and advanced optical properties of quasi-2D perovskite at first， and then summarize several strategies about regulating crystal orientation of quasi-2D perovskite. Finally， we will review the development of quasi-2D perovskite based micro- and nanolaser， and present a summary and prospect for quasi-2D perovskite materials and laser devices in the future.
LIU Hong-gang,CHEN Jian-hao,XIAO Zi-fan,PING Wen-liang,DONG Guo-ping
Abstract：Microlasers have huge potential in areas such as integrated optical paths and nanotechnology， owing to the capability of scaling physical dimension of devices down to micro-/nanometer level. In numerous materials， Rare-earth（RE） ion doped laser gain micro/nano materials show many advantages such as low preparation cost， good environmental stability and abundant spectrum bands（ultraviolet to mid-infrared）， making it an ideal laser gain micro/nano material. In recent years， the emergence of various cleverly designed RE ion doped laser gain micro/nano materials and the design and manufacture of new micro/nano optical resonators have greatly promoted the development of new RE ion doped microlasers. In this paper， the design and preparation of novel RE ion doped laser gain micro/nano materials and the basic principle of micro/nano optical resonator are briefly introduced. Then， the representative RE ion doped microlasers are reviewed and their preparation process and laser performance are discussed.
Abstract：The erbium-doped fiber amplifier（EDFA） is a revolutionary breakthrough in the field of optical fiber communication， which makes long-distance， large-capacity， high-speed optical fiber communication possible. To realize long-distance transmission of optical fiber communication systems， it is inseparable from the corresponding optical fiber amplifier. However， with the explosive growth of transmission capacity demand， the existing DWDM communication system is facing huge pressure for capacity expansion. This paper systematically reviews the research progress of expanding the gain bandwidth to improve the transmission capacity， discusses the key issues involved in broadband active fibers and amplifiers， puts forward an understanding of ultra-broadband active fibers and their amplifiers in various bands， and provides a new perspective on future space division multiplexing based on few-mode multi-core fibers.
XU Chong-lei,MA Feng-kai,ZHANG Zhen,JIANG Da-peng,ZHANG Zhong-han,KOU Hua-min,CHEN Zhen-qiang,SU Liang-bi,XU Jun
Abstract：Laser emission in visible spectral regions has attracted much attention due to a wide variety of domains such as material processing in industry， fluorescence microscopy in research science， wireless optical communication， holography， laser display. Recently，Pr3+ activated fluoride laser crystals have achieved watt-level continuous output in various visible spectral ranges for instance， cyan（3P0→3H4）， green（3P1→3H5）， orange（3P0→3H6）， red（3P0→3F2） as well as deep red （3P0→3F3，4）. In this paper， various fluoride and oxide host crystals doped with Pr3+ are used as the research objects， and the spectral characteristics and laser output status of the current Pr3+-activated laser crystals are systematically summarized. The effect of ESA（Excited state absorption）， MPR（Multi-phonon relaxation）， CR（Cross-relaxation） process on Pr3+ laser output is expected to further provide valuable guidance and suggestions for the selection of laser gain medium. Finally， the existing problems in Pr3+-doped laser crystal materials are pointed out， and the follow-up research direction is prospected.
Keywords：Visible region laser crystal;Pr3+ doped;excited state absorption;cross relaxation;Multi-phonon relaxation
Abstract：Mid-infrared rare-earth doped continuous fiber laser has a wild application in the fields of photoacoustic technology， infrared countermeasures， medical surgery， plastic processing， 5G communication， etc. However， the development of high⁃power single-frequency CW fiber lasers is greatly limited by the single fiber matrix material used to prepare mid-infrared rare earth doped CW fiber lasers and the lack of high-gain fibers and devices.In this paper， the traditional silica fiber， fluoride fiber， chalcogenide fiber and heavy metal oxide fiber are compared， and finally tellurite fiber is taken as the elaboration object. At present， the highest output power of 2.0 μm band is 8.08 W， and the highest slope efficiency is 77%. Theoretical simulation results of 3.0 μm band show that the highest output power is up to 5.219 W and the highest slope efficiency is up to 40%.
Abstract：The yellow lasers are of great importance as they have potential applications in the areas such as medical aesthetics， atomic cooling and trapping， and radar. Dy3+ is the best activating ion for yellow lasers due to its 4F9/2→6H13/2 radiative transition， but its spin-forbidden transition in the visible wavelength leads to a small absorption and emission cross section， which causes difficulties in yellow laser output. In this paper， Dy3+∶Sr3Gd（BO3）3（abbreviation Dy3+∶SGB）， Dy3+/Tb3+∶SGB and Dy3+/Eu3+∶SGB crystals were successfully grown by the Czochralski method， and their spectral properties and energy transfer mechanisms were analyzed by room-temperature polarization absorption spectra， emission spectra， fluorescence decay curves and Judd-Ofelt theoretical calculations. It is shown that the co-dopant of Tb3+ and Eu3+ increases the emission cross section and fluorescence quantum efficiency of Dy3+ in the yellow emission band， which is favorable to the yellow laser output of Dy3+. In addition， it is demonstrated that a mutual energy transfer process between Dy3+ and Tb3+ occurs in Dy3+/Tb3+∶SGB crystals and only Dy3+→Eu3+ in Dy3+/Eu3+∶SGB crystals.
Keywords：Sr3Gd（BO3）3;Dy3+;yellow emission;spectral properties;energy transfer
Abstract：3%Dy，1%Tb∶LuAG（Dy，Tb∶LuAG） nanopowders with good dispersibility were synthesized by the co-precipitation method using NH4HCO3 as a precipitant. The thermal decomposition behavior of the precursor， and the phase and microstructure of powders were studied. Dy，Tb∶LuAG ceramics with high transparency were fabricated by vacuum pre-sintering and hot isostatic pressing（HIP） post-treatment without any sintering additives for the first time. The influences of pre-sintering temperature on the microstructure and the optical quality of the ceramics were investigated. When the pre-sintering temperature is 1 600 ℃， the in-line transmittance of the annealed Dy，Tb∶LuAG ceramics（1.5 mm in thickness） reaches 83.6% at 578 nm， and the average grain size of the annealed ceramics is 0.9 μm. In addition， the absorption cross section of the 3%Dy，1%Tb∶LuAG ceramics at 447 nm is calculated to be 1.3×10-21 cm2， with a full width at half maximum（FWHM） of 3.0 nm， which matches that of commercial GaN blue laser diodes. This study shows that Dy，Tb∶LuAG transparent ceramics have potential application value in the yellow lasers.
TAN Hui-yu,ZHANG Pei-xiong,NIU Xiao-chen,SONG Jia-wan,ZHENG Wei-bi,CHEN Yan,LI Zhen,CHEN Zhen-qiang
Abstract：The Czochralski method was used to successfully grow the Sm3+-doped CaDyAlO4 crystal， and its optical properties in visible light were investigated. Important spectral performance parameters such as intensity parameters， spontaneous emission probability， and fluorescence branching ratio were obtained using the Judd-Ofelt theory. The crystal has a strong absorption peak at 353 nm， a full width at half maximum（FWHM） of 13 nm， and an absorption cross section of 9.76×10-20 cm2. When excited at 353 nm， an ultra-broadband orange-yellow emission from 500 nm to 650 nm is obtained， with Dy3+ ions and Sm3+ ions. The main emission peaks of Dy3+ ions and Sm3+ ions are at 570 nm and 620 nm， respectively， and the emission cross sections are 4.15×10-20 cm2 and 4.03×10-20 cm2， respectively. The above findings suggest that Sm3+∶CaDyAlO4 crystals could be a promising gain material for orange-yellow tunable lasers from 500 nm to 650 nm.
LIU Jian,WANG Wu-di,SONG Qing-song,DONG Jian-shu,XUE Yan-yan,WANG Qing-guo,XU Xiao-dong,SU Liang-bi,XU Jun
Abstract：A series of 10%Tb∶x%Y∶CaF2（x = 0， 3， 5， 10） crystals have been successfully grown by the temperature gradient technique（TGT）. The crystal structure was analyzed by X-ray diffraction， and the results showed that the high concentration of rare earth ion doping increased the unit cell parameters， but still maintained the fluorite cubic structure of CaF2. The absorption spectra， fluorescence spectra， and fluorescence decay curves were measured and analyzed at room temperature. By co-doping Y3+ ions， the spectral quality factor Ω4/Ω6 increased from 0.75 to 0.80. Using F-L formula， the emission cross sections of 10%Tb∶CaF2 were calculated to be 0.89×10-21 cm2 and 0.082×10-21 cm2 for the 545 nm and 587 nm， respectively， and the emission cross sections of 10% Tb，10%Y∶CaF2 were calculated to be 0.89×10-21 cm2 and 0.077×10-21 cm2 for the 545 nm and 587 nm. The fluorescence lifetime of 5D4 level is more than 5 ms， and there is no fluorescence lifetime quenching phenomenon caused by high concentration doping. The long fluorescence lifetime means that Tb3+ ion has excellent energy storage capacity. The experimental results show that Tb∶CaF2 and Tb，Y∶CaF2 crystals are gain mediums with great potential to realize visible laser output.
Keywords：Tb∶CaF2;Visible laser;spectral properties;J-O theory
Abstract：As a popular inorganic luminescent materials， up-conversion fluorescent fluosilicate glass ceramics are promising in solid-state laser， solid-state illumination， optical anti-counterfeiting encode and optical thermometry. Research and applications of up-conversion fluorescent fluosilicate glass ceramics containing binary-elements nanocrystal， ternary-elements nanocrystal were reviewed. In which， we compared the effect of composition on nanocrystallization and up-conversion photoluminescence， and listed the issues need to be solved for the further development. We hope this review can provide inspiration and guidance to the future research of up-conversion fluorescent fluosilicate glass ceramics.
Keywords：fluosilicate glass;glass ceramics;composite glass with nanocrystal;up-conversion photoluminescence;rare earth ions
Abstract：A high quality Yb∶GdScO3 crystal was grown by Czochralski method. The X-ray diffraction was refined by Rietveld method， and the calculated crystal density and doping concentration were obtained. The effective segregation coeﬃcient of Yb3+ is calculated to be 1.04.Its absorption spectrum， emission spectrum and fluorescence lifetime were measured at room temperature. The absorption， emission oscillator strength， spectral line strength， transition probability， energy level lifetime and integral emission cross section of Yb3+ in GdScO3 matrix were calculated for the first time. The laser performance is preliminarily evaluated. The results show that Yb∶GdScO3 is easy to output laser near 1 030 nm and 1 060 nm， while the laser output near 1 000 nm is only possible under the condition of high population inversion.
Abstract：The repetitive nanosecond high energy laser plays an important role in scientific inquiry， industrial manufacturing， military defense and other fields. In this paper， the research progress of Yb3+ or Nd3+ rare-earth ion doped laser crystals， laser glasses and laser ceramics， as well as the representative results of the corresponding repetitive nanosecond high energy lasers， are introduced in detail. The influence of the laser gain medium emission cross section， thermal conductivity， upper level life and other parameters on the laser system is analyzed. We discussed the selective preparation， thermal management and control of spontaneous emission amplification effect of gain medium for repetitive nanosecond high energy lasers， and sorted out the solutions. Finally， the prospect of its future development is discussed.
Keywords：heavy frequency pulse laser;large energy laser;Yb3+， Nd3+， gain medium
WANG Gui-ji,DING Xiao-yuan,YIN Yan-ru,JIA Zhi-tai,TAO Xu-tang
Abstract：In this paper， undoped and Dy3+ doped Lu2O3 crystalswere prepared by EFG（Edge-defined film-fed growth technique）. The undoped and doped crystals turned to colorless and pale yellow after annealing in air， respectively. The undoped and doped crystals were characterized by high resolution X-ray diffraction， Raman spectroscopy and absorption spectroscopy. The results indicated that the full width at half maximum（FWHM） of the peaks were 98.4″， 170.4″ and 193.9″， and the maximum phonon energies were 609.0， 611.4， 612.6 cm-1， respectively. The undoped crystal had no obvious absorption in the range of 260-3 000 nm band. While the doped crystals had characteristic absorption peaks of Dy3+ at 350， 742， 798， 884， 1 063， 1 258， 1 681， 2 774 nm. 1 258 nm laser was used for excitation， and fluorescence spectra of 2.7-3 μm were obtained. The lifetime of the 6H13/2 energy level of Dy3+ was calculated as 17.9 μs and 16.3 μs， respectively. The optical parameters of Dy3+∶Lu2O3 crystal were calculated by Judd-Ofelt（hereinafter referred to as J-O） theory， and the results showed that Dy3+∶Lu2O3 crystal has the potential to realize laser output at 3 μm band.