硅酸盐学报2025，Vol.53Issue(12)：3446-3460,15.DOI:10.14062/j.issn.0454-5648.20250102
Er3+激活的Gd3Ga5O12和Lu3Ga5O12中红外激光晶体的生长、光谱与激光性能
Growth,Spectra,and Laser Performance of Er3+-Activated Gd3Ga5O12 and Lu3Ga5O12 Mid-Infrared Laser Crystals
摘要
Abstract
Introduction Mid-infrared(MIR)lasers operating within a spectral region of 2.7-3.0 μm have a significant importance in applications such as laser surgery and remote sensing.Trivalent erbium(Er3 +)ions are among the most efficient activators for MIR lasers,leveraging the 4I11/2→4I13/2 transition.Nevertheless,the realization of high-power and efficient laser output is often hindered due to the self-terminating effect and substantial thermal loading in Er3+-doped gain medium.This study was to investigate the high-performance Er3+-doped Gd3Ga5O12(GGG)and Lu3Ga5O12(LuGG)laser crystals with the low phonon energy and high thermal conductivity. Methods High-quality single crystals of Er:GGG,Er/Pr:GGG,and Er:LuGG were grown by the Czochralski method in an optimized atmosphere(i.e.,98%N2+2%O2)with iridium crucibles and(111)-oriented seeds.Raw materials underwent multi-step sintering to guarantee the phase purity.Comprehensive spectroscopic analysis was conducted on the polished samples.The room-temperature absorption spectra were determined by a model Lambda 900 spectrophotometer.The fluorescence spectra at the mid-infrared(MIR:2500-3000 nm),near-infrared(NIR:950-1750 nm)and upconversion(UC:500-700 nm)bands were measured under 965/967 nm excitation by an optical parametric oscillator(OPO)or a xenon lamp using models FLS920 and FSP920 fluorescence spectrometers.The fluorescence decay curves for the 4I11/2 and 4I13/2 energy levels were recorded to determine the fluorescence lifetime.The laser performance was assessed under two pumping schemes(i.e.,a xenon lamp and a 965 nm fiber-coupled laser diode(LD)).The crystals were fabricated into laser gain media of various sizes and doping profiles,including a bonded configuration(undoped GGG/56%Er:GGG)to alleviate thermal lensing.The continuous-wave(CW)performance was evaluated via input-output power curves,slope efficiency,laser threshold,and beam quality factor(M2).The passive Q-switching was implemented with two-dimensional materials(i.e.,graphene and a Bi2Te3/graphene heterostructure)as saturable absorbers.The main pulsed laser metrics(i.e.,pulse train profile,average output power,pulse width,repetition rate,and peak power)were systematically determined. Results and Discussion The as-grown crystals display a high optical quality with intense and broad absorption bands centered at 965 nm.The 30%Er,0.5%Pr:GGG composition has a notably high absorption cross-section of 5.13×10-21 cm2 and a full width at half maximum(FWHM)of 15 nm,indicating a superior spectral overlap with commercial 980 nm InGaAs laser diodes and enabling efficient pump coupling.The incorporation of Pr3+ions can enhance the MIR fluorescence emission based on a cross-relaxation energy transfer mechanism,i.e.,4I13/2(Er3+)+3H4(Pr3+)→ 4I15/2(Er3+)+3F4(Pr3+).This process effectively depopulates the lower laser level(4I13/2),leading to a reversal of the intrinsic lifetime ratio between metastable states.Specifically,a ratio of τ(4I11/2)/τ(4I13/2)of 2.348 appears in the sample 30%Er,0.5%Pr:GGG,which is critical for overcoming the self-termination barrier in Er3+-based～3 μm lasers. Under 965 nm LD pumping,a CW laser emission at 2.75 μm is attained.The 56%Er:GGG crystal has a maximum output power of 325 mW with a slope efficiency of 16.15%.The bonded GGG/56%Er:GGG structure improves the thermal management,increasing the maximum power to 453 mW and the slope efficiency to 17.1%,while also improving beam quality(i.e.,M2 reduces from 1.68 to 1.48).The Er/Pr:GGG crystal(11%Er,0.4%Pr)shows a superior thermal performance,reaching 372 mW output and a higher damage threshold,due to the lower Er3+concentration and efficient energy transfer. The passive Q-switching with graphene and Bi2Te3/graphene absorbers produce impressive pulsed outcomes.The graphene-based Q-switched bonded GGG/Er,Pr:GGG/GGG crystal has a maximum average power of 186 mW,a pulse width of 360 ns,and a repetition rate of 120.5 kHz,corresponding to a pulse energy of 1.54 μJ and a peak power exceeding 4.28 W.The Bi2Te3/graphene Q-switched Er:LuGG laser can deliver a higher average power of 274 mW with a shorter pulse width of 340 ns at 135 kHz,yielding a pulse energy of 2.03 μJ and a peak power of>5.97 W.These findings affirm a potential of these materials in high-performance pulsed MIR lasers. Conclusions This work established Er3+-doped GGG and LuGG crystals as highly promising gain media for efficient～2.75 μm mid-infrared lasers.The strategies of Pr3+co-doping and crystal bonding proved effective in mitigating the self-terminating effect and thermal load,leading to the improvement of substantial performance.The effective operation in both continuous-wave and passively Q-switched regimes could underscore the applicability of these crystals in practical high-power MIR laser systems.关键词
铒掺杂钆镓榴石晶体/激光晶体/提拉法生长晶体Key words
erbium-doped gadolinium gallium garnet crystal/laser crystal/Crystal growth by Czochralski method分类
数理科学引用本文复制引用
ZHENG Longxing,ZHU Zhaojie,YOU Zhenyu,WANG Yan,TU Chaoyang..Er3+激活的Gd3Ga5O12和Lu3Ga5O12中红外激光晶体的生长、光谱与激光性能[J].硅酸盐学报,2025,53(12):3446-3460,15.基金项目
国家重点研发计划(2022YFB3605700) （2022YFB3605700）
国家自然科学基金区域创新与发展联合基金(U21A20508) （U21A20508）
福建省科技计划引导性项目(2024H0033,2022H0043). （2024H0033,2022H0043）
