摘要
针对光频梳、医学光声成像及痕量气体探测等应用需要,研制了一种InP基碰撞锁模半导体激光器,可在1.74μm波段实现重复频率为19.3GHz的高效锁模,其射频(RF)谱半高全宽(FWHM)约14kHz。在可饱和吸收区未加偏压时,激光器的阈值电流为83mA,最大出光功率可达到25.83mW。固定吸收区偏置电压在-1.6V,增益区驱动电流高于130mA时,锁模激光器开始输出微波射频信号,并且RF谱的FWHM随着电流增加可下降至十几kHz。固定驱动电流为520mA,在吸收区偏置电压从-1.4V降至-2V过程中,激光发射光谱逐渐展宽,在-2V偏压下,光谱的FWHM为9.88nm,包含40多个间隔为0.2nm的纵模。对比分析了不同驱动电流和偏置电压下的射频频谱和发射光谱的变化趋势,证明了该锁模器件具有高效、稳定的锁模机制。
Objective The InP-based mode-locked semiconductor lasers have attracted considerable interest for their ability to generate pulses with high repetition frequency.However,they can hardly reach 1.7μm wavelength range due to the difficulty on growing indium-rich highly strained quantum wells,which limits their application on optical frequency combs,medical photoacoustic imaging and gas detection.For the purpose of chip-scale sensing in the mid-infrared region,this paper designs a 1.7μm InP-based monolithic mode-locked semiconductor laser.Methods The laser structure was grown an(100)oriented n-InP substrate by Metal-organic Chemical Vapor Deposition(MOCVD).The undoped active zone of the laser contains three compressively strained 8-nm-thick InxGa1-xAs quantum wells separated by 12-nm-thick InxGa1-xAsyP1-y,which is enclosed between 300-nm-thick InGaAsP layers(Fig.1(a)).The MOCVD-grown wafer is processed into~1.9-μm-wide ridge waveguide using standard optical processing(Fig.1(b)).The 4178-μm-long colliding-pulse mode-locked laser(MLL)is achieved with an~168-μm-long saturable absorber located at the center of the cavity(Fig.1(c)).Results and Discussions The threshold current of the device is 83 mA without bias voltage,and the maximum output power is 25.83 mW(Fig.3(b)).According to the relation between external quantum differential efficiency and cavity length(Fig.3(a)),the internal loss of this epitaxial structure is calculated to be 14.378 cm−1.An efficient mode locking has been achieved at 1.74μm with a repetition frequency of 19.3 GHz,the narrowest linewidth of RF spectra is 14 kHz(Fig.4(a)),and the period of pulse train is 51.88 ps(Fig.4(b)).A microwave signal appears at a gain current of 130 mA when VSA=−1.6 V,and its RF spectrum drops down to tens kHz with increasing current(Fig.5).Decreasing the reverse bias voltage from−1.4 V to−2 V with forward current at 520 mA,the laser emission spectrum gradually broadens(Fig.6).The 9.88-nm-wide spectrum contains more than 40 longitudinal modes spaced by 0.2 nm
作者
段阳
林中晞
苏辉
DUAN Yang;LIN Zhongxi;SU Hui(Key Laboratory of Optoelectronic Materials Chemistry and Physics,Fujian Institute of Research on the Structure of Matter,Chinese Academy of Sciences,Fuzhou 350002,China;University of Chinese Academy of Sciences,Beijing 101408,China;Fujian Science&Technology Innovation Laboratory for Optoelectronic Information of China,Fuzhou 350108,China;Fujian Z.K.Litecore Co,Ltd,Fuzhou 350003,China)
出处
《红外与激光工程》
EI
CSCD
北大核心
2024年第6期90-97,共8页
Infrared and Laser Engineering
基金
国家重点研发计划项目(2023YFB2804803)
中国科学院海西研究院自主部署项目(CXZX-2022-GH09)
闽都创新实验室自主部署项目(2021ZR114)。
