Harmonic Mode-Locked Er-Doped Fiber Laser Based on a Microfiber-Based PbS Nanoparticle Saturable Absorber

Lead sulfide (PbS) is a nanomaterial with excellent optical and chemical properties, such as a narrow bandgap (0.37 eV), high thermal damage threshold, and high stability. Obviously, it is appropriate as a saturable absorber (SA) device for ultrafast photonics. However, PbS nanoparticles (NPs) as the SA of ultrashort harmonic mode-locked pulse still haven't been demonstrated at present. In this paper, the PbS NPs are made into an SA-device-based microfiber by optical deposition method and connected in an integrated Erbium-doped fiber laser. And both characteristics and nonlinear optical properties of PbS NPs have been systemically investigated. A fundamental frequency mode-locked pulsed laser is proposed, whose central wavelength is 1560 nm, and the pulse width is 1 ps. In addition, high repetition rate operations are achieved, with a maximum repetition rate of 833 MHz. This is the first time that PbS NPs are used to generate 96th-order harmonic mode-locking, and the corresponding pulse duration is 987 fs. It is demonstrated that PbS NPs are a kind of SA photonic material with excellent performance. It can improve the communication capacity by applying fiber communication, and it has potential application value even in material processing and optical comb.     

Q-Switched Thulium-Doped Fiber Laser with Pure Titanium-Film-Based Saturable Absorber

ABSTRACT

We demonstrate the generation of Q-switching pulse train in thulium-doped fiber laser (TDFL) cavity by employing titanium-based saturable absorber (Ti-SA). The Ti-SA was fabricated by depositing titanium particles molecules using electron beam evaporation on the surface of a polyvinyl alcohol (PVA) film. Subsequently, stable Q-switched pulses were obtained within the 1,552 nm pump power range from 272.1 to 467 mW, with repetition rate tuned from 21.8 to 39.1 kHz. At the maximum pump power, the TDFL showed that the pulse duration of 2.22 μs and the maximum pulse energy of 124 nJ.     

Mode-Locked Erbium-Doped Fiber Laser Using Vanadium Oxide as Saturable Absorber

A mode-locked erbium doped fiber laser(EDFL) is demonstrated using the vanadium oxide(V_2O_5) material as a saturable absorber(SA). The V_2O_5 based SA is hosted into poly ethylene oxide film and attached on fiber ferule in the laser cavity. It shows 7% modulation depth with 71 MW/cm~2 saturation intensity. By incorporating the SA inside the EDFL cavity with managed intra-cavity dispersion, ultrashort soliton pulses are successfully generated with a full width at half maximum of 3.14 ps. The laser operated at central wavelength of 1559.25 nm and repetition frequency of 1 MHz.     

Q-Switched Ytterbium-Doped Fiber Laser Using Black Phosphorus as Saturable Absorber

We demonstrate a Q-switched ytterbium-doped fiber laser(YDFL) using a newly developed multi-layer black phosphorous(BP) saturable absorber(SA).The BP SA is prepared by mechanically exfoliating a BP crystal and sticking the acquired BP flakes onto a scotch tape.A small piece of the tape is then placed between two ferrules and incorporated in a YDFL cavity to achieve a stable Q-switched operation in a 1.0 μm region.The laser has a pump threshold of 55.1 mW,a puise repetition rate that is tunable from 8.2 to 32.9kHz,and the narrowest pulse width of 10.8 μs.The highest pulse energy of 328 nJ is achieved at the pump power of 97.6mW.Our results show that multi-layer BP is a promising SA for Q-switching laser operation.     

Q-Switched Raman Fiber Laser with Molybdenum Disulfide-Based Passive Saturable Absorber

We demonstrate a Q-switched Raman fiber laser using molybdenum disulfide(MoS_2) as a saturable absorber(SA).The SA is assembled by depositing a mechanically exfoliated MoS_2 onto a fiber ferrule facet before it is matched with another clean ferrule via a connector.It is inserted in a Raman fiber laser cavity with a total cavity length of about 8 km to generate a Q-switching pulse train operating at 1560.2 nm.A 7.7-km-long dispersion compensating fiber with 584 ps·nm~(-1)km~(-1) of dispersion is used as a nonlinear gain medium.As the pump power is increased from 395 mW to 422 mW,the repetition rate of the Q-switching pulses can be increased from 132.7 to137.4kHz while the pulse width is concurrently decreased from 3.35μs to 3.03μs.The maximum pulse energy of 54.3nJ is obtained at the maximum pump power of 422 mW.These results show that the mechanically exfoliated MoS_2 SA has a great potential to be used for puise generation in Raman fiber laser systems.     

Cadmium Selenide Polymer Microfiber Saturable Absorber for Q-Switched Fiber Laser Applications

We demonstrate the generation of a Q-switching pulse train in an erbium-doped fiber laser(EDFL) cavity using a newly developed cadmium selenide(CdSe) based saturable absorber(SA). The SA is obtained by embedding CdSe nanomaterials into a polymethyl methacrylate(PMMA) microfiber. It is incorporated into an EDFL cavity to generate a Q-switched laser operating at 1533.6 nm. The repetition rates of the produced pulse train are tunable within 37-64 kHz as the pump power is varied from 34 mW to 74 mW. The corresponding pulse width reduces from 7.96μs to 4.84μs, and the maximum pulse energy of 1.16 nJ is obtained at the pump power of74 mW.     

飞秒激光在可饱和吸收体中的动力学特性

从激光动力学的自洽理论出发，推导出适用于含有可饱和吸收体的激光系统动力学方程组，研究了激光振荡的稳定性与系统参数的依赖关系，包括激励强度参数、饱和系数和能级寿命，并讨论了满足激光振荡稳定性的条件下B类激光的弛豫振荡特性。结果表明，增大激励强度与饱和系数有利于系统形成稳定的振荡输出，而且当激励强度超过一定阈值时，B类激光会产生弛豫振荡行为。     

基于微纳光纤-单壁碳纳米管可饱和吸收体的被动调Q掺镱光纤激光器

为实现具有高脉冲能量的调Q脉冲激光输出,利用微纳光纤-单壁碳纳米管复合的方法制备可饱和吸收体,并对基于该类型可饱和吸收体器件的被动调Q掺镱光纤激光器进行研究。采用拉伸法将普通单模石英光纤拉制成微纳光纤,将其与单壁碳纳米管溶液复合,进一步制备成全光纤集成型器件。将该器件置于环形腔掺镱光纤激光器中,利用976 nm半导体激光器作为抽运源。当抽运功率为53 mW时,实现了调Q脉冲激光输出,激光中心波长为1 039 nm。进一步提升抽运功率至76 mW,可获得脉冲宽度为3.1μs、重复频率为25.5 kHz、单脉冲能量为941nJ的调Q脉冲激光输出。研究表明,利用微纳光纤制备的可饱和吸收体器件具有较高的损伤阈值,可用于实现高脉冲能量的激光输出。     

Q-Switched Erbium-Doped Fiber Laser Using Cadmium Selenide Coated onto Side-Polished D-Shape Fiber as Saturable Absorber

A stable Q-switched erbium doped fiber laser emitting at 1558 nm is demonstrated using a cadmium selenide(CdSe) material coated onto a side-polished D-shape fiber as the saturable absorber(SA). By elevating the input pump power from the threshold of 91 mW to the maximum available power of 136 mW, a pulse train with a maximum repetition rate of 57.44 kHz, minimum pulse width of 3.76 us, maximum average output power of7.99 mW, maximum pulse energy of 0.1391 uJ, and maximum peak power of 36.99 mW are obtained. The signalto-noise ratio of the spectrum is measured to be around 75 dB. This CdSe based SA is simple, robust, and reliable,and thus suitable for making a portable pulse laser source.     

Q-Switched Fiber Laser with a Hafnium-Bismuth-Erbium Codoped Fiber as Gain Medium and Sb2Te3 as Saturable Absorber

Journal of Russian Laser Research - We successfully demonstrate Q-switched fiber laser with a 20 cm long Hafnium-Bismuth-Erbium codoped fiber (HBEDF) as an active medium in conjunction with...     

基于两滤波器级联和饱和吸收体的单纵模双波长光纤激光器

提出和证实了一种光纤环形激光器. 将一个带通滤波器与一个带阻滤波器级联,用一段保偏掺铒光纤作为饱和吸收体,得到了一种单纵模双波长光纤激光器. 结果表明,该激光器波长间隔为0.4 nm,边模抑制比大于49 dB.如果将两个波长进行差拍,该激光器有潜力得到49.85 GHz的微波信号.     

Optically Modulated Tunable O-Band Praseodymium-Doped Fluoride Fiber Laser Utilizing Multi-Walled Carbon Nanotube Saturable Absorber

A tunable and optically modulated fiber laser utilizing a multi-walled carbon nanotube based saturable absorber is demonstrated for operation in the O-band region.A praseod.ymium-doped fluoride fiber is used as the gain medium and the system is capable of generating modulated outputs at 1300 nm.Pulsed output is observed at pump powers of 511 mW and above,with repetition rates and pulse widths that can be tuned from 41 kHz and3.4 μs to 48 kHz and 2.4 μs,respectively,at the maximum pump power available.A maximum average output power of 100μW with a corresponding single pulse energ.y of 2.1 nJ is measured,while the tunability of the proposed laser is forom 1290 nm to 1308 nm.The output is stable,with peak power fluctuations of～4 dB from the average value.     

Laser-diode-pumped Passively Q-switched Nd:Sr5(VO4)3F Laser with Cr4+:YAG Saturable Absorber

Cr4+:YAG is a new saturable absorber for passive Q-switching. As a passive Q-switcher, it has several excellent properties, such as low saturation fluence, high damage threshold, good thermal conductivity, no degradation and so on. By using a laser-diode as pumping source and Cr4+ :YAG as passive Q switcher, the passive Q-switching run in Nd: Sr5(VO4)3F laser at 1. 065 μm is realized. The average output power, the single pulse energy, the pulse width and the repetition rate for different small-signal transmission of Cr4+:YAG and different pumping power were measured. Meanwhile, the coupling rate equations for Cr4+:YAG as passive Q-switcher were given and the experimental results agreed with the numerical solution of equations.     

Q-Switching Pulse Generation with Thulium-Doped Fiber Saturable Absorber

Q-switched pulsed laser systems operating in the eye-safe wavelength region （λ〉 1.4 μm） are promis- ing for applications such as light detection and ranging （lidar）, differential absorption lidar, optical communi- cation, sensor and instrumentations. Fiber lasers are particularly attractive for such applications due to the fact that the beam quality can be independent of output power and they can be robustly engineered. There is an increasing interest in Q-switched erbium- doped fiber lasers （EDFLs）, which can be generated by using either active or passive techniques. Com- pared with the actively Q-switched ones, passively Q- switched EDFLs have attracted much attention for their advantages of compactness, low cost, flexibility and simplicity of design. Different kinds of saturable absorbers, such as the transition metal-doped crys- tals and semiconductor quantum-well structures, have been applied to realize Q-switched EDFLs.How- ever, when they are used in the laser cavity, additional alignment devices, such as lens, mirrors or U-bench units, have to be applied. This may increase the in- sertion loss and the complexity of the laser cavity.     

Theoretical Study on Passively Mode-Locked Fiber Lasers with Saturable Absorber

In this paper, passively mode-locked erbium-doped fiber lasers based on saturable absorber (SA) have been theoretically studied. The energetics and pulse properties for different fiber laser cavity configurations have been investigated and the effects of each component (active fiber, passive fiber, and SA) in the laser cavity have been studied. This numerical study takes into account the temporal change in the saturable absorption (dq/dt).The presented simulations could be highly useful for understanding, optimizing, and improving passively mode-locked fiber lasers with SA.     

激光二极管侧面抽运Nd∶YAG锁模激光器的研究

利用谐振腔的稳定条件对激光二极管侧面抽运的 Nd∶YAG锁模直腔的稳区特性和谐振腔内的光斑分布进行了分析。根据对腔参量的分析,选取合适的腔参量设计了一个简单的侧面抽运直腔,该谐振腔腔形简单,没有像散,振荡光模式好,有利于激光器的锁模运转。实验中采用国内自行研制的半导体可饱和吸收镜,实现了激光二极管侧面抽运半导体可饱和吸收镜锁模Nd∶YAG激光器的连续锁模运转,平均输出功率为 2 W,锁模脉冲宽度为10 ps,重复频率为100 MHz。结合实验结果进一步讨论了半导体可饱和吸收镜的一些参量如饱和恢复时间、调制深度等对实现稳定连续锁模的影响。     

激光二极管侧面抽运Nd:YAG锁模激光器的研究

利用谐振腔的稳定条件对激光二极管侧面抽运的Nd：YAG锁模直腔的稳区特性和谐振腔内的光斑分布进行了分析。根据对腔参量的分析，选取合适的腔参量设计了一个简单的侧面抽运直腔，该谐振腔腔形简单，没有像散，振荡光模式好，有利于激光器的锁模运转。实验中采用国内自行研制的半导体可饱和吸收镜，实现了激光二极管侧面抽运半导体可饱和吸收镜锁模Nd：YAG激光器的连续锁模运转，平均输出功率为2W，锁模脉冲宽度为10ps，重复频率为100MHz。结合实验结果进一步讨论了半导体可饱和吸收镜的一些参量如饱和恢复时间、调制深度等对实现稳定连续锁模的影响。     

GeO2-Sb22O3-K22O玻璃空芯光纤材料的光学特性研究

系统地研究了传输CO2激光用的新型光纤材料GeO2-Sb2O3-K2O玻璃空芯光纤的光学特性。通过理论计算,得到了该材料nr＜1的波长范围,消光系数Ｋ和损耗系数a,通过工艺和材料的选择,使a理论值达到0.05 dB/m。同时讨论了HE11,TM01,TE01模式损耗和频率的关系。     

Wavelength-Tunable Rectangular Pulses Generated from All-Fiber Mode-Locked Laser Based on Semiconductor Saturable Absorber Mirror

The wavelength-tunable rectangular mode-locking operation is demonstrated in an all-fiber laser based on semiconductor saturable absorber mirror.As the dissipative soiiton resonance signature,the puJse duration varies from 580 ps to 2.1 ns as a function of the increasing pump power.Correspondingly,the maximum pulse energy is9.11 nJ.Moreover,it is found that the wavelength tunable operation with a range of approximately 10 nm could be obtained by properly adjusting the polarization controllers.The characteristics of the rectangular pulses at different wavelengths are similar to each other.The demonstration of the wavelength tunable rectangular pulses would be beneficial to some applications for many fields such as spectroscopy and sensing research.     

Density-Functional-Theory Studies of C20 in Femtosecond Laser Pulses

We study the electron response of C20 excited by strong femtosecond laser pulses by applying the time-dependent local-density approximation, an approach which has proven to provide a robust tool for investigations of fullerene. The optical response as well as the full electronic dipolar response and ionization processes of C20 subject to the laser field are explored. A strong correlation between induced electronic dipole oscillations and electron emission is observed.