基于少模光纤被动调Q柱矢量光光纤激光器

通过单模光纤和少模光纤熔融拉锥耦合的方法制备出模式转换器,而后将一层多壁的碳纳米管薄膜作为可饱和吸收体覆盖到拉锥光纤的锥区,形成一种可饱和吸收体柱矢量光器件.结合调Q光纤激光器和模式转换器件的优势,可以简单高效地产生脉冲柱矢量光束,并得到具有峰值功率高、模式纯度高等特点的脉冲高阶模式激光输出.通过实验实现了中心波长为1560nm、最大单脉冲能量和最大峰值功率分别为116nJ和57mW的稳定调Q脉冲输出.通过调节光路中的偏振控制器,可以分别实现径向和角向偏振的调Q脉冲激光的输出.     

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。     

Passively Q-switched cylindrical vector laser based on a black phosphorus saturable absorber

We demonstrate an all-fiber Q-switched cylindrical vector laser based on a black phosphorus saturable absorber and a transverse mode converter. The saturable absorber is prepared by incorporating the polyvinyl alcohol with anti-oxidized black phosphorus nanosheets exfoliated in aqueous poly(dimethyldiallyl ammonium chloride)solution. The mode converter is composed of a tapered two-mode fiber and a single-mode fiber, and it can excite switchable azimuthally and radially polarized beams by modulating the input polarization. By enhancing the pump power from 64.68 to 174.82 mW, the repetition rate of the Q-switched azimuthally/radially polarized laser enlarges from 16.72/19.25 to 30.71/37.82 kHz.     

High-power all-fiber passively Q-switched laser using a doped fiber as a saturable absorber: numerical simulations

We report a design for a power-scalable all-fiber passively Q-switched laser that uses a large mode area Yb-doped fiber as a gain medium adiabatically tapered to an unpumped single-mode Yb-doped fiber, which serves as a saturable absorber. Through the use of a comprehensive numerical simulator, we demonstrate a passively Q-switched 1030 nm pulsed laser with 14 ns pulse duration and 0.5 mJ pulse energy operating at 200 kHz repetition rate. The proposed configuration has a potential for orders of magnitude of improvement in both the pulse energies and durations compared to the previously reported result. The key mechanism for this improvement relates to the ratio of the core areas between the pumped inverted large mode area gain fiber and the unpumped doped single-mode fiber.     

Graphene-based passively Q-switched dual-wavelength erbium-doped fiber laser

We demonstrate a compact Q-switched dual-wavelength erbium-doped fiber (EDF) laser based on graphene as a saturable absorber (SA). By optically driven deposition of graphene on a fiber core, the SA is constructed and inserted into a diode-pumped EDF laser cavity. Also benefiting from the strong third-order optical nonlinearity of graphene to suppress the mode competition of EDF, a stable dual-wavelength Q-switching operation has been achieved using a two-reflection peak fiber Bragg grating as the external cavity mirror. The Q-switched EDF laser has a low pump threshold of 6.5 mW at 974 nm and a wide range of pulse-repetition rate from 3.3 to 65.9 kHz. The pulse duration and the pulse energy have been characterized. This is, to the best of our knowledge, the first demonstration of a graphene-based Q-switched laser.     

脉冲LDA泵浦Nd∶YVO4/GaAs被动调Q锁模激光器

用脉冲激光二极管阵列（LDA）作为泵浦源、微柱透镜阵列和透镜导管作为耦合系统,以As＋注入GaAs可饱和吸收片作为被动调Q锁模元件,实现了Nd∶YVO4激光器调Q锁模运转.调Q运转阶段,激光器每泵浦脉宽内输出一个调Q脉冲,调Q脉宽7ns.调Q锁模运转阶段,初始透过率60％的GaAs晶片对调Q包络内的锁模脉冲的调制深度达到95％以上,锁模脉冲重复频率991 MHz.研究了加在LDA上的电压、方波脉冲的脉宽和重复频率对调Q锁模脉冲特性的影响,并对实验结果进行了讨论.     

Laser spectrum of a high power Tm,Ho:GdVO<Subscript>4</Subscript> laser

In this paper, we report a 18.8 W continuous wave and 18.4 W Q-switched diode-pumped cryogenic Tm(5 at %), Ho(0.5 at %):GdVO₄ laser. The pumping source of Tm, Ho:GdVO₄ laser is a fiber-coupled laser diode with fiber core diameter of 0.4 mm, supplying 42 W power at 802.5 nm. For input pump power of 41.9 W at 802.4 nm, the output power of 18.8 W in CW operation, optical-to-optical conversion efficiency of 45% at 2.05 μm and the average output power of 18.4 W in Q-switched operation, optical-to-optical conversion efficiency of 44% at 2.04 and 2.05 μm have been attained. The emission wavelengths of the Tm(5 at %), Ho(0.5 at %):GdVO₄ laser were firstly compared when it worked in CW mode and Q-switched mode.     

High-power passively Q-switched mode-locking Nd:GdVO4 laser with LT-InGaAs saturable absorber

The generation of passively Q-switched mode-locking (QML) pulse has been obtained from a diode-pumped Nd:GdVO₄ laser with a LT-InGaAs wafer as saturable absorber as well as output coupler. Under the incident pump power of 10 W, an average output power of QML was 1.8 W with a Q-switched repetition rate of 280 kHz. The pulse duration of Q-switched pulse is about 160 ns and mode-locked pulse within the Q-switched envelope had a repetition rate of 410 MHz. It is indicated that the present LT-InGaAs is a very promising device in the field of mode locking solid-state laser, and we are sure that it will be complete pure cw mode locking with single beam output easily after further optimizing in the parameter such as saturation fluence, modulation depth, recovery time and damage threshold in semiconductors.     

26 mJ, 130 W Q-switched fiber-laser system with near-diffraction-limited beam quality

We demonstrate a Q-switched fiber laser system emitting sub-60 ns pulses with 26 mJ pulse energy and near-diffraction-limited beam quality (M2<1.3). In combination with a repetition rate of 5 kHz, a corresponding average output power of 130 W is achieved. This record performance is enabled by a large-pitch fiber with a core diameter of 135 μm. This fiber allows for effective single-mode operation with mode field diameters larger than 90 μm even at average output powers exceeding 100 W.     

A study of a Q-switched double-clad ytterbium-doped fiber laser with amplifying effect

A high repetition rate ytterbium-doped double-clad (YDDC) fiber laser with amplifying effect is described by using acousto-optic modulator. The characteristic of Q-switched pulses are studied with accurate control of opening gate time of modulator. The stable Q-switched pulses with tens of nanoseconds width can be observed at high repetition rate varied from 50 kHz to 500 kHz using this laser. The stable operation area of the Q-switched fiber laser is discussed and the analysis results agree well with that of the experiment.     

High power Q-switched Yb-doped photonic crystal fiber laser producing sub-10 ns pulses

We report on a Q-switched fiber laser producing pulse durations well below 10 ns by using a short-length ytterbium-doped rod-type photonic crystal fiber as gain medium. At repetition rates up to 100 kHz pulse energies up to 0.5 mJ and average powers in excess of 30 W have been obtained in single-transverse mode beam quality. The compact short pulse laser system possesses further power and energy scaling potential.     

High-peak-power second-harmonic generation of single-stage Yb-doped fiber amplifiers

A high-peak-power and high-repetition-rate fiber laser architecture is successfully demonstrated using a single-stage fiber amplifier. Nonlinear optical effects in a fiber amplifier degrade the monochromaticity of amplified laser pulses. In general, it is difficult for a non-monochromatic laser pulse to realize high-order harmonic generation with bulk nonlinear optical crystals. To overcome this problem, a single-stage amplifier architecture and a gain fiber with a high cladding absorption coefficient are employed. Furthermore, single-stage amplification enables the use of a multi-longitudinal mode electro-optically (EO) Q-switched micro seed laser. This architecture can generate a peak power of 100 kW at 50 kHz and an average power of 10 W. A second-harmonic conversion efficiency of 51% is obtained using this architecture and a LiB₃O₅ (LBO) crystal.     

Active Q switching of a fiber laser with a microsphere resonator

We propose and demonstrate an active Q-switched fiber laser using a high-Q microsphere resonator as the Q-switching element. The laser cavity consists of an Er-doped fiber as the gain medium, a glass microsphere reflector (coupled through a fiber taper) at one end of the cavity, and a fiber Bragg grating reflector at the other end. The reflectivity of the microsphere is modulated by changing the gap between the microsphere and the fiber taper. Active Q switching is realized by oscillating the microsphere in and out of contact with the taper. Using this novel technique, we have obtained giant pulses (maximum peak power approximately 102 W, duration approximately 160 ns) at a low pump-power threshold (approximately 3 mW).     

掺铒石英光纤中的受激拉曼散射

掺铒石英光纤中的受激拉曼散射刘邦群高晖＊刘祖荫王琳（武汉大学物理系武汉４３００７２）（＊武汉物理数学研究所武汉４３００７２）ＳｔｉｍｕｌａｔｅｄＲａｍａｎＳｃａｔｅｒｉｎｇｉｎＥｒ－ｄｏｐｅｄＳｉｌｉｃａＦｉｂｅｒＬｉｕＢａｎｇｑｕｎ，ＧａｏＨｕｉ＊...     

基于多层石墨烯可饱和吸收体的被动调Q Ho∶YAG激光器

报道了2μm被动调Q的Ho∶YAG激光器,该激光器采用Tm~(3+)光纤激光器作为泵浦源,使用多层石墨烯作为可饱和吸收体。在连续波激光输出模式下,当泵浦功率为4.2 W时,获得了750 mW激光输出,输出激光中心波长为2.09μm,斜率效率为29.6%。在连续波激光器谐振腔中插入多层石墨烯可饱和吸收体并调整谐振腔,获得了脉冲激光输出。当泵浦功率为4.2 W时,获得最小脉冲宽度3.1μs、重复频率66.6 kHz的脉冲激光输出,其最大平均输出功率为170 mW,斜率效率为12.6%,光束质量因子M_x~2=1.15,M_y~2=1.12。     

All-fiber actively Q-switched fiber laser tuned by a pair of temperature controlled fiber Bragg gratings

We report an all-fiber actively Q-switched erbium-doped fiber laser, where the linear laser cavity mirrors are composed of two fiber Bragg gratings (FBGs). The laser oscillation wavelength could be tuned by this pair of temperature controlled FBGs. The Q-switching is achieved by an all-fiber phase modulation device. Using this system, we could obtain stable Q-switched laser pulses output, which could be optimized by tuning the reflection wavelengths of the two FBGs to be adjacent to each other. Instead of being modulated by the FBG filter in high-speed oscillation, this fiber laser system is operating in the Q-switched regime using an all-fiber phase modulator, producing a more stable laser output spectrum.     

High-efficiency Q-switched erbium fiber laser using a Bragg grating-based modulator

In this work we analyze the behavior of an erbium-doped fiber laser which is based on a simple scheme. Excitation of the active medium is performed in the 980 nm pump band with a CW semiconductor laser source. Two fiber Bragg gratings acting as mirrors of the Fabry–Perot laser cavity were used. One of these gratings was mounted over a piezoelectric (PZT) element. By applying voltage pulses to the piezoelectric, the laser cavity was temporally modulated and Q-switched laser pulses up to 530 mW peak powers at 3 kHz were obtained. Typical laser emission of 2–3 μs temporal widths and 0.1 nm of optical bandwidth have been achieved when the system was operated at 18.5 kHz repetition rates. Different behaviors were observed depending on the pumping level of the active medium and on the amplitude and frequency of the signal applied on the PZT. Q-switched laser output, in the erbium spectral gain region, with high laser efficiency of energy conversion was generated. Pumping at 76 mW and operating the laser at 18.5 kHz, an efficiency of 26% was obtained.     

Erbium-doped CW and Q-switched fiber ring laser with fiber grating Michelson interferometer

The band-pass characteristic of fiber grating Michelson interferometer is analyzed, which acts as bothband-pass filter and Q-switch. An erbium-doped fiber ring laser based on fiber grating Michelsoninterferometer is implemented for producing single longitudinal mode CW operation with 5 MHz spectrallinewidth and up to 6 mW output power. In Q-switched operation, stable fiber laser output pulses withrepetition rate of 800 Hz, pulse width of 0.6 μs, average power of 1.8 mW and peak power of 3.4 W aredemonstrated. The peak power and average power of the Q-switched pulses are varied with the repetitionrate.     

Tandem-pumped 1120-nm actively Q-switched fiber laser

We report on a tandem-pumped actively Q-switched fiber laser system emitting at 1120 nm.Parasitic oscillation is challenging in Yb-doped Q-switched 1120-nm fiber laser,which is suppressed by pumping with a fiber laser at 1018 nm.At least four times improvement in output peak power is demonstrated in a single laser setup with 1018-nm fiber laser pumping instead of 976-nm laser diode pumping.This is,to the best of our knowledge,the first demonstration of a tandem-pumped Q-switched fiber laser.     

Phase locking and supermode selection in multicore photonic crystal fiber lasers with a large doped area

We report on the laser properties of multicore photonic crystal fiber lasers. A stable phase locking of six- and seven-core structures through evanescent coupling is observed. Effective supermode selection is obtained by using both diffraction losses and the Talbot effect. A pure in-phase supermode is obtained (1.1 times diffraction limited). The laser operating in this mode has a slope efficiency of 70% with up to 44 W of output power. The modal area of the in-phase supermode multicore fiber is 1150 microm2, which makes it, to our knowledge, the single-mode fiber laser with the largest mode field area. In-phase laser action is stable when the fiber is bent.