碳化钛可饱和吸收体锁模掺镱光纤激光器
Ti3C2Tx Saturable Absorber Mode-Locked Ytterbium-Doped Fiber Laser
DOI: 10.12677/app.2025.157072, PDF, HTML, XML,    科研立项经费支持
作者: 刘诗晗, 王 蓟*, 晁举庆, 徐斌斌:长春理工大学物理学院,吉林 长春
关键词: 光纤激光器锁模掺镱光纤可饱和吸收体碳化钛Fiber Laser Mode-Locked Yb3+-Doped Fiber Saturable Absorber Ti3C2Tx
摘要: 文章提出了一种基于碳化钛(Ti3C2Tx)可饱和吸收体的锁模掺镱光纤激光器,并对其性能进行了研究。通过以Ti3C2Tx溶液与羧甲基纤维素钠(NaCMC)溶液混合的方式制备了碳化钛可饱和吸收体薄膜,并将其以“三明治”结构集成到环形腔掺镱光纤激光器中,成功实现了稳定的锁模脉冲输出。实验结果表明,在泵浦功率200 mW时,锁模光纤激光器的平均输出功率为6.77 mW,重复频率为27 MHz,脉冲宽度为667 fs。这不仅验证了碳化钛在超快光子学应用中的潜力,也为新型二维材料在激光技术中的进一步开发提供了参考。
Abstract: This paper proposes a mode-locked ytterbium-doped fiber laser based on a titanium carbide (Ti3C2Tx) saturable absorber and investigates its performance. The Ti3C2Tx saturable absorber film was prepared by mixing a titanium carbide solution with a sodium carboxymethyl cellulose (NaCMC) solution as the film-forming agent. The film was integrated into a ring-cavity ytterbium-doped fiber laser in a “sandwich” structure, successfully achieving stable mode-locked pulse output. Experimental results show that, at a pump power of 200 mW, the mode-locked fiber laser achieved an average output power of 6.77 mW, a repetition rate of 27 MHz, and a pulse duration of 667 fs. This study not only verifies the potential of titanium carbide in ultrafast photonics applications but also provides a valuable reference for the further development of novel two-dimensional materials in laser technology.
文章引用:刘诗晗, 王蓟, 晁举庆, 徐斌斌. 碳化钛可饱和吸收体锁模掺镱光纤激光器[J]. 应用物理, 2025, 15(7): 672-680. https://doi.org/10.12677/app.2025.157072

1. 引言

超快激光器以其超短脉冲宽度和高峰值功率的特性,在诸多领域有着广泛应用。在材料加工方面,超短脉冲激光能够避免在加工过程中产生热影响区,提高加工质量和精度,用于高精度微加工、表面处理等[1]。在生物医学领域,可用于眼科手术对角膜组织进行精确切割,也可作为激发光源用于细胞和组织的高分辨率成像,还能对生物组织进行非热损伤处理[2]。在科学研究中,超短脉冲激光是超快光谱学、强场物理和量子信息科学等领域的重要工具[3]

为了构成紧凑的光纤激光器,可饱和吸收体(SA)在调制激光系统以提供超快激光方面起着非常重要的作用。受稳定、高性价比的超快光纤激光器需求的启发,来自不同领域的研究人员都在努力开发新型光纤激光器。随着低维光学材料的发展,碳纳米管(CNT) [4]-[6]、石墨烯[7] [8]、氧化石墨烯(GO) [9]、黑磷(BP) [10]-[13]、拓扑绝缘体(TI) [14]-[16]、金属二硫化物[17]-[19]、过渡金属碳化物(MXene) [20]-[25]等都可以作为可饱和吸收体材料用于锁模光纤激光器。其中,MXene具有宽波段光学响应、高非线性光学性能、易于集成等特点,成为近年来在超快光子学领域研究的主要SA材料之一。2020年Shi等人采用少层Ti3C2Tx纳米片作为SA,成功实现了1530.85 nm处掺铒光纤激光器(EDFL)的稳定锁模输出,锁模脉冲持续时间为265 fs,重复频率为8.46 MHz,信噪比为47 dB。此外还在掺镱光纤激光器(YDFL)中获得了792 ps的锁模激光脉冲,信噪比为75 dB [26]。2021年Afiq Arif Aminuddin Jafry等人制备了MXene薄膜(MXene-film)和将MXene沉积在D形光纤(MXene-DS)上的两种SA器件,并将两种SA器件都放入EDFL腔中,MXene-film能产生3.64 ps的锁模激光,脉冲能量为6.03 nJ,MXene-DS能产生4.6 ps的锁模激光,脉冲能量为7.69 nJ,证明了MXene作为SA具有强饱和吸收能力[27]。2021年Rosol等人采用选择性蚀刻法制备MXene Ti3C2Tx,并将其嵌入聚乙烯醇(PVA)中形成薄膜。在掺铒光纤激光腔中加入Ti3C2Tx薄膜,泵浦功率在55~144 mW之间调节,获得了稳定的孤子锁模激光器。锁模激光的脉宽为3.68 ps,重复频率为1.89 MHz。最大平均输出功率和脉冲能量分别为24.42 m和12.92 nJ [28]

本文针对当前基于Ti3C2Tx可饱和吸收体的超快激光器研究中存在的系统结构复杂、光学器件冗余及成本过高的问题,提出了一种创新性解决方案。通过自主研发的Ti3C2Tx-NaCMC可饱和吸收体,并构建其三明治式锁模器件结构,实现了掺镱光纤激光器谐振腔的优化集成。NaCMC为阴离子型水溶性聚合物,其胶体溶液表现出优异的分散稳定性,尤其在高剪切或长时间储存条件下不易发生相分离。这一特性使得碳化钛前驱体浆料更易均匀成膜,减少微观缺陷。相比之下,PVA溶液黏度受温度波动影响显著(高温黏度下降,冷却后恢复),可能引发成膜过程中的厚度不均问题。实验表明,该新型器件在仅需200 mW泵浦功率条件下,即可输出中心波长1064.78 nm的稳定锁模脉冲,脉冲持续时间压缩至677 fs量级,信噪比提升至34 dB,同时维持6.77 mW的输出功率与250.7 nJ的单脉冲能量。相较于传统方案,本研究的突破性在于通过材料界面工程与器件结构创新,显著降低了系统复杂度与光学元件数量,为低成本、高可靠性的超快光纤激光器开发提供了新的技术路径。

2. 实验装置

实验中使用的SA是自制的Ti3C2Tx SA,将Ti3C2Tx溶液与适量的NaCMC溶液混合,放入离心管中进行超声处理,为了使Ti3C2Tx与NaCMC溶液充分混合,对该混合溶液进行超声作用超过10 h。超声处理过的溶液静置后,未发现沉淀,得到均匀分散的Ti3C2Tx-NaCMC溶液。用取液枪将超声分散后的溶液均匀滴涂在洁净的载玻片上,在超净环境下隔尘,沉积成均匀的薄膜。将制备好的Ti3C2Tx可饱和吸收体薄膜切成直径2 mm的正方形小块,夹在由法兰盘连接的两个FC/PC光纤连接器的端面中间,这样就形成了“三明治”结构的Ti3C2Tx可饱和吸收体器件。

碳化钛可饱和吸收体锁模掺镱光纤激光器实验结构如图1所示,采用环形腔结构,由一台中心波长为976 nm的激光二极管(LD)经由980/1064 nm波分复用器(WDM)对一段掺镱光纤(YDF,LUSTER LightWave Co., Ltd., Yb-1200-4/125)进行泵浦,YDF的纤芯直径为4 μm、数值孔径为0.2、色散系数为24 ps2/km,在980 nm的峰值吸收为280 dB/m,长度为1 m。自制的“三明治”结构Ti3C2Tx SA为锁模元件。保偏隔离器(PD-ISO)使光信号只能单向传输,同时保持光信号的偏振状态,进而提高系统的稳定性和可靠性。为了使锁模脉冲更加稳定,在环形腔内加入了一个偏振控制器(PC)。最后,经过耦合器(OC)将环形腔内20%的光作为输出,80%的光继续留在腔内循环。激光器腔内所有器件的尾纤型号均为HI1060,其色散系数为23 ps2/km。实验中使用功率计(Thorlabs-PM100D)、光谱仪(YOKOGAWA-AQ6375)、示波器(TeKtronix-MDO3054)、频谱分析仪(Agilent-E4407B)、自相关仪(PulseCheck-SM-2000),对激光器输出信号的功率、光谱和脉冲特性进行测量。

Figure 1. Schematic diagram of a fiber laser with a Ti3C2Tx SA

1. 碳化钛可饱和吸收体光纤激光器结构图

3. 实验结果与分析

图2为锁模光纤激光器输出功率随泵浦功率的变化曲线,在锁模光纤激光器的性能分析中,泵浦功率与输出功率的关联性呈现出典型的线性响应。实验数据表明,当泵浦功率从50 mW提升至200 mW时,输出功率由0.75 mW线性增长至6.77 mW,对应的斜率效率为4.66%。这一数值反映了激光器在阈值以上工作区间的能量转换效率,该线性区间内光腔损耗保持相对稳定,符合理想激光工作模型。

Figure 2. The curve of the output power of the laser versus the pump power

2. 激光器输出功率随泵浦功率的变化曲线

图3为锁模光纤激光器输出的光谱图,激光输出中心波长为1064.78 nm,3 dB光谱带宽达到8.60 nm。结合功率特性曲线可知,在有效工作区间内,激光器同时实现了功率的线性增长和光谱质量的稳定维持,表明系统在200 mW泵浦功率以下具备良好的工作可靠性。

Figure 3. Spectrum output of the laser at a pump power of 200 mW

3. 泵浦功率200 mW时激光器输出的光谱

泵浦功率从50 mW增加到200 mW时,示波器显示的脉冲序列呈现稳定状态,脉冲峰值没有巨大的抖动。图4为泵浦功率为200 mW时,激光器的脉冲序列,此时每个脉冲的时间间隔为3.7 ns,重复频率为27 MHZ。在2 μs时间窗内连续观测的脉冲序列插图中,整体能够看出脉冲峰值没有巨大的抖动,说明该激光器的脉冲输出表现出很高的稳定性。

Figure 4. Output pulse train of the laser at a pump power of 200 mW

4. 泵浦功率200 mW时激光器输出脉冲序列

当泵浦功率为200 mW时观察频谱仪所得的数据,在频谱仪的分辨率带宽为100 kHz时,如图5所示测得信噪比为34 dB。

Figure 5. Frequency spectrum of the pulse at a pump power of 200 mW

5. 泵浦功率200 mW时脉冲的频谱图

图6所示为输出脉冲的自相关曲线,通过自相关仪测量绘制,设置Gaussian函数对自相关轨迹进行拟合,得到此时的自相关轨迹脉宽944 fs,根据高斯脉冲的时域宽度换算关系(实际脉宽 = 自相关脉宽 × 0.707),计算得到激光器输出脉冲的实际脉宽为667 fs。通过计算可以得到此时激光器输出的单脉冲能量为250.7 nJ。

Figure 6. Autocorrelation curve of the output pulse at a pump power of 200 mW

6. 泵浦功率200 mW时输出脉冲自相关曲线

为了验证基于Ti3C2Tx-NaCMC可饱和吸收体的掺镱锁模光纤激光器输出脉冲信号的稳定性,利用光功率计实时监测了该激光器在系统中长时间连续运转时的平均输出功率。将泵浦功率稳定在200 mW,每隔1小时记录一次该泵浦功率下激光器的输出功率、脉冲宽度。实验结果如图7所示,在激光器连续运行的4小时内,该激光器的平均输出功率为6.77 mW,波动范围为±5%,说明激光器输出具有良好的稳定性。

Figure 7. Average output power graph of a mode-locked laser over a 4-hour period

7. 锁模激光器在4小时内的平均输出功率图

在锁模光纤激光器长时间稳定性测试中,系统展现了优异的光谱维持能力。实验数据表明,在持续4小时的连续锁模运行过程中,激光输出光谱的3 dB带宽中心波长偏移量始终控制在±1.5 nm以内。如图8记录的时域演变图谱显示,未出现谱线分裂现象。

Figure 8. Output spectrum of a mode-locked laser over a 4-hour period

8. 锁模激光器在4小时内的输出光谱图

Table 1. Comparison of output performance in mode-locked fiber lasers using different two-dimensional materials

1. 不同二维材料锁模光纤激光器输出性能的比较

二维材料

中心波长

脉冲宽度

输出功率

单脉冲能量

参考文献

BP

1064.4 nm

51 ps

18.9 mW

1.13 nJ

30

PtSe2

1064.47 nm

470 ps

12.19 mW

2.31 nJ

31

Bi2Te3

1057.82 nm

230 ps

0.86 mW

0.21 nJ

32

Sb2Te3

1047.1 nm

5.9 ps

4 mW

0.21 nJ

33

CH3NH3PbI3

1064 nm

931 ps

15.7 mW

3.85 nJ

34

Ti3C2Tx

1064.78 nm

667 fs

6.77 mW

250.7 nJ

本文

表1列举了本文所述Ti3C2Tx与近年来基于各种二维材料产生脉冲的性能参数[29]-[33]。从表中可以看出,所有材料工作波长都在一微米附近,Ti3C2Tₓ表现出最短脉冲宽度(667 fs)和最高单脉冲能量(250.7 nJ),其中心波长(1064.78 nm)与BP (1064.4 nm)、PtSe2 (1064.47 nm)接近,但脉冲宽度较Sb2Te3 (5.9 ps)缩短3个数量级,单脉冲能量较CH3NH3PbI3 (3.85 nJ)提升65倍,综合性能优势显著,适用于高精度超快激光领域。

4. 结论

综上所述,通过将制备的Ti3C2Tx-NaCMC溶液用常规沉积法沉积在载玻片上获得了Ti3C2Tx可饱和吸收体,并将此制成“三明治”结构的可饱和吸收体器件,然后插入到环形腔掺镱光纤激光器中,实现了锁模激光输出。在50~200 mW的泵浦功率下,均有稳定的锁模脉冲序列。泵浦功率为200 mW时,激光器得到最大平均输出功率为6.77 mW,中心波长为1064.78 nm,脉冲持续时间为667 fs,信噪比为34 dB。这表明Ti3C2Tx可以作为可饱和吸收体应用于1 μm波段锁模掺镱光纤激光器。

基金项目

吉林省科技厅国际合作项目(20220402021 GH)。

NOTES

*通讯作者。

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