Single-longitudinal-mode fiber ring laser using fiber grating-based Fabry-Perot filters and variable saturable absorbers

A single-longitudinal-mode (SLM) fiber ring laser is demonstrated by incorporating a fiber Bragg grating (FBG)-based Fabry-Perot (F-P) filter and a variable saturable absorber in a fiber ring cavity. An ultra-narrow bandpass filter is established by the combined mode filtering of the FBG-based F-P filter and the variable saturable absorber. No accurate control for cavity length is required, and stable single longitudinal-mode operation without mode hopping is conveniently achieved.     

Blue laser via IR resonant doubling with 71% fiber to fiber efficiency

We report on high efficiency resonant doubling to 486 nm using periodically poled KTP. The IR laser source is an FBG stabilized semiconductor laser with a maximum polarization maintaining (PM) fiber coupled output of 840 mW. An output power of 680 mW at 486 nm was obtained from our optimized cavity, giving net efficiency of 81%. Also, we report an 87.5% net efficiency in coupling of this blue light from the servo locked cavity into a single-mode PM fiber. This gives a total of 71% fiber to fiber efficiency. Furthermore, a wall plug efficiency of 21.4% was obtained.     

Single-longitudinal-mode erbium-doped fiber laser based on a fiber Bragg grating Fabry-Perot filter

A novel single-longitudinal-mode (SLM) erbium-doped fiber laser with a simple linear cavity based on a fiber Bragg grating Fabry-Perot filter (FBG-FPF) and a narrowband (～0.06 nm) FBG is proposed and demonstrated experimentally. Two uniform FBGs form the FBG-FPF, which has two ultranarrow transmission bands with a bandwidth of 0.12 pm and a wavelength spacing of 0.095 nm. By slightly tuning the central wavelength of the narrowband FBG, SLM lasing at 1549.658 or 1549.563 nm (corresponding to the two transmission peaks of the FBG-FPF) is achieved with a laser output power of ～4 mW, when the pump power is ～75 mW.     

Stable single longitudinal mode fiber ring laser based on polarization maintaining erbium doped fiber

A stable single longitudinal mode (SLM) fiber ring laser that incorporates polarization maintaining erbium doped fiber (PM EDF) acting as gain medium and saturable absorber is proposed and demonstrated. Both theoretical deviation and experimental result prove that optical intensity is time invariant when the laser operates in single longitudinal mode, the SLM operation can be approximately verified by optical intensity analysis, which is practical to analyze longitudinal mode in the application of engineering. The linewidth of the fiber ring laser is measured by the delayed self-heterodyne interferometery, and an acousto-optic frequency shifter is employed to shift the lasing frequency and eliminate zero frequency interfere. The SLM operation is verified by the scanning Fabry–Perot interferometer, whereas the lasing frequency drift slowly during a period of 2 h, PM EDF is proved to be effective on suppressing mode hopping and selecting longitudinal mode.     

7-GHz high-repetition-rate mode-locked pulse generation using short-cavity phosphate glass fiber laser

A compact short-cavity high-repetition-frequency mode-locked fiber laser configured with Er³⁺/Yb³⁺ highly co-doped phosphate glass fiber and a graphene optical deposited film as saturable absorber is proposed and analyzed experimentally. The laser operates in stable mode-locked regime with fundamental repetition rate of 7.02 GHz. The output power is measured to be 1.2 mW with pump power around 80 mW, and the optical spectrum is centered about 1533.768 nm with mode spacing of 0.056 nm. As the pump power increases, the laser operates in multi-wavelength mode-locking emission state with the same longitude mode spacing. Moreover, the measure results show that different wavelength emission operates in different polarization states.     

Tunable single-longitudinal-mode Ytterbium all fiber laser with saturable-absorber-based auto-tracking filter

A broadband tunable, single-longitudinal-mode (SLM) Ytterbium fiber laser with unpumped Ytterbium-doped Sagnac loop is proposed and demonstrated experimentally. The unpumped Ytterbium-doped Sagnac loop is employed as a saturable absorber based auto-tracking filter to ensure single-longitudinal-mode oscillation. And a tunable band pass optical filter with large tuning range is applied to achieve broadband tuning ability. With 1-m Ytterbium-doped fiber as the gain medium, the SLM operation is achieved with over 60-nm wavelength tuning range at 160-mW pump power. The laser is very stable with output power of about 3 dBm and optical signal to noise ratio of higher than 50 dB in all the 60-nm tuning range.     

掺Yb3+光纤F-P腔被动锁模激光器的实验研究

 掺镱(Yb³⁺光纤被动锁模激光器谐振腔采用线性腔结构，腔内插入二分之一波片和偏振分束器引入偏振旋转，结合半导体可饱和吸收镜的自起动，实现稳定的被动锁模运转。腔内插入光栅对，提供负的群速度色散，以补偿光纤所带来的正色散，达到压缩脉宽的目的。当泵浦功率为300 mW、光栅对的距离为10 cm时，获得稳定的锁模运转，锁模输出功率28 mW，脉冲重复频率20 MHz，输出光谱宽度达15 nm，按脉冲变换极限公式，其脉冲时间宽度与频带宽度的乘积为0.315计算，脉宽可达100 fs以下。     

氧化石墨烯被动调Q掺铒光纤激光器

报道了基于氧化石墨烯的被动调Q掺铒光纤激光器。激光器采用环形腔结构,调Q器件为自制的氧化石墨烯可饱和吸收镜。泵浦功率在81~505 mW范围内时,得到了重复频率68~124 kHz的稳定的调Q脉冲输出,脉宽为0.47~1.60 s。由于泵浦功率限制,激光器最大输出功率为10 mW, 相应单脉冲能量为80.6 nJ。此种基于氧化石墨烯可饱和吸收体的被动调Q光纤激光器体积小、成本低廉、结构简单、稳定性高、光束质量高,具有广阔的应用前景。     

Achieving single-longitudinal-mode output about Tm:YAG laser at room temperature

We report on the single-longitudinal-mode Tm:YAG laser with a volume Bragg grating pumped by laser diode at room temperature. The maximum SLM power of 142 mW was achieved under incident pump power of 3.22 W. The central wavelength was 2012.6 nm accords with the resonant wavelength of the VBG. Three cavity lengths were used to achieve high efficiency and clear spectrum. The maximum output power were measured to be 450.5, 451.4, and 457.3 mW at incident pump power of 3.22 W, corresponding to a slope efficiency of 17.1, 16.9, and 16.7% for the cavity length of 30, 40, and 50 mm, respectively. 40 mm cavity length having the cleanest spectrum among the three was used for SLM laser with one 1 mm F-P etalon inserted into the cavity.     

Medium power single-mode single-wavelength fiber laser

Medium-power, single-mode, single-wavelength fiber laser working at room temperature using a polarization-maintaining erbium-ytterbium co-doped fiber as the gain medium, and an un-pumped elliptical core erbium-doped fiber as a saturable absorber to reduce linewidth and mode hopping of the lasing wavelength is reported. The effects of length, erbium ion concentration, and polarization-maintaining property of the saturable absorber were explored. The output power of the laser was more than 100 mW and the lasing line was stable for more than 3 h with an intensity fluctuation of less than 0.2 dB. The laser linewidth (FWHM = Full width at half maximum) was 7.5 MHz and the signal to noise ratio was more than 50 dB. The output of the laser was measured using an optical spectrum analyzer (OSA) of resolution 1.25 GHz and a scanning Fabry-Perot spectrum analyzer (SFPSA) of resolution 6.7 MHz.     

Passively Q-switched Er-doped fiber laser using a semiconductor saturable absorber mirror

A passively Q-switched Er-doped fiber laser using a semiconductor saturable absorber mirror (SESAM) is demonstrated. Q-switching is observed with the output power produced at a slope efficiency of 29.4% with respect to the absorbed pump power. The maximum average output power of 8.37 mW is achieved. The pulse repetition frequency obtained can be turned from 1.72 to 7.95 kHz. The pulse energy of 17.2 nJ has been obtained at the pump power of 46.75 mW, and the pulse width is 30 μs.     

Stable nanosecond pulse generation from a graphene-based passively Q-switched Yb-doped fiber laser

We demonstrate stable 70?ns pulse generation from a Yb-doped fiber laser passively Q-switched by a graphene-based saturable absorber mirror in a short linear cavity. The maximum output power was 12?mW and the highest single pulse energy was 46?nJ. The repetition rate of the fiber laser can be widely tuned from 140 to 257?kHz along with the increase of the pump power. To the best of our knowledge, this is the first report for passively Q-switched sub-100-ns pulse operation of a graphene-based saturable absorber in a Yb-doped fiber laser.     

An Efficient Single-Frequency Yb-Doped All-Fiber MOPA Laser at 1064.3 nm

An efficient narrow-linewidth single-frequency(SF) Yb-doped all-fiber master oscillator power amplifier(MOPA)laser operating at 1064.3 nm is demonstrated experimentally.A ring cavity SF fiber laser is used as the seed source for the MOPA system and the Yb-doped fibers are employed as the gain medium or the saturable absorber.The SF operation is observed to be stable without mode hopping.The highest output power of 266 mW is obtained under the 400 mW pump power with the corresponding slope efficiency of 66.2%.The linewidth of the amplified output laser is approximately 1 kHz and its optical signal-to-noise ratio is over 45 dB.     

Yb-doped fiber oscillator generating 41 fs wave-breaking-free pulses

We report on the generation of wave-breaking-free pulses from an Yb-doped fiber oscillator at 1.03 μm by using the nonlinear polarization rotation mode-locking. The average output power reached 113 mW as limited by available pump power of 578 mW. The generated pulses had a pulse energy up to 2 nJ and could be externally compressed down to 41 fs. The output pulses exhibited a smooth spectrum without any side lobe or temporal wave-packet breaking due to the nonlinear phase modulation in an additional Erdoped fiber acted as a saturable absorber in the fiber laser.     

Passively mode-locked ytterbium fiber laser utilizing chirped-fiber-Bragg-gratings for dispersion control

A robust, self-starting picosecond pulse source based on ytterbium (Yb³⁺) doped fiber laser is described. Utilizing a chirped-fiber-Bragg-grating (C-FBG) for dispersion control, solitary mode-locking is obtained without bulk dispersion compensation elements. A semiconductor saturable absorber (SESAM) is used for stable self-starting. 3.6 ps pulses are produced, with 45 MHz basic repetition-rate and mW scale average output power at 1060 nm. Detailed numerical simulations based on the modified nonlinear Schrödinger equation agree well with the experimental results and are used as a design tool for the solitary mode-locked picosecond laser. The presented design can be simply employed in an all-fiber environmentally-stable system.     

147 fs碳纳米管倏逝场锁模全光纤掺铒光纤激光器

利用化学腐蚀法在光纤包层表面成功制备了调制深度为3.9%的单壁碳纳米管饱和吸收体.组建了环形腔结构的全光纤掺铒光纤激光器,以制备的单壁碳纳米管薄膜为锁模元件,利用倏逝场锁模实现了锁模输出.锁模脉冲的中心波长为1556 nm,3 dB光谱带宽为24 nm,脉冲宽度为147 fs,重复频率为150 MHz.在520mW抽运功率下,平均输出功率为21 mW,相应的单脉冲能量为0.14 nJ.     

Highly stable, passively mode-locked fiber laser with low pump power for subpicosecond pulse generation

We present the design of highly stable, passively mode-locked fiber lasers which are based on a simple configuration and require a low pump power for the generation of optical pulses with subpicosecond pulsewidth. Our designed fiber laser uses a semiconductor saturable absorber mirror to realize the self-starting, passive mode locking at a low pump power of 29 mW, with which a stable optical pulse train is obtained at the fundamental repetition rate of 52.5 MHz and the central wavelength of 1557 nm. The output mode-locked optical pulses have a pulsewidth of 881 fs and an average output power of 1.78 mW, respectively.     

Photonic generation of frequency-switchable microwave signals exploiting polarization-induced spectrum splitting in fiber grating-based Fabry-Perot filters

Frequency-switchable microwave signals are optically generated using a dual-wavelength single-longitudinal-mode erbium-doped fiber ring laser. The splitting of the resonance peak is observed in fiber grating-based Fabry-Perot (F-P) filters depending on the injected light polarization states. Choosing two different resonance peaks of the grating-based F-P filter and using a variable saturable absorber formed by a section of incompletely transparent erbium-doped fiber, wavelength-switchable dual-wavelength single longitudinal-mode operation is achieved in the fiber ring laser. Microwave frequency switched among 8.75, 21.25 and 25.4 GHz is implemented by feeding the output laser to a high-speed photodetector.     

光纤光栅F-P标准具选模单频环形腔光纤激光器

 讨论了光纤光栅法布里-珀罗(F-P)标准具选模光纤激光器的单频运转原理，并研制了全光纤结构单频掺Er³⁺光纤环形激光器。实验中采用两个976 nm激光二极管双向泵浦作为泵浦源，高掺杂浓度掺Er³⁺光纤作为增益介质，以行波腔消除空间烧孔效应，利用光纤光栅F-P标准具窄带选模特性，当泵浦光功率为36 mW时，得到了稳定的单频激光输出。实验中使用了长5和3 m的掺杂光纤，在泵浦光功率为145 mW时输出功率分别为19和42 mW，光-光转换效率分别为13%和29%，斜率效率分别达到了16%和33%。输出谱线3 dB带宽0.01 nm，无跳模现象。