Multi-wavelength Q-switched Erbium-doped fiber laser with photonic crystal fiber and multi-walled carbon nanotubes

A simple multi-wavelength passively Q-switched Erbium-doped fiber laser (EDFL) is demonstrated using low-cost multi-walled carbon nanotubes (MWCNTs)-based saturable absorber, which is prepared using polyvinyl alcohol as a host polymer. The multi-wavelength operation is achieved based on non-linear polarization rotation effect by incorporating 50?m long photonic crystal fiber in the ring cavity. The EDFL produces a stable multi-wavelength comb spectrum for more than 14 lines with a fixed spacing of 0.48?nm. The laser also demonstrates a stable pulse train with the repetition rate increasing from 14.9 to 25.4?kHz as the pump power increases from the threshold power of 69.0?mW to the maximum pump power of 133.8?mW. The minimum pulse width of 4.4?μs was obtained at the maximum pump power of 133.8?mW while the highest energy of 0.74 nJ was obtained at the pump power of 69.0?mW.     

High-speed actuation of a piezoelectric actuator by pulse driving and stopping of its residual mechanical vibration

The driving method for high-speed actuation and prevention of residual vibration of a piezoelectric actuator is described. The driving voltage is composed of a pulse voltage and a step voltage. As a result, the risetime of the piezoelectric actuator can be reduced to approximately 1/4 of its mechanical response period by setting the pulse width, and the residual vibration can be prevented by adjusting the step voltage. The high-speed stopping of a piezoelectric actuator driven by AC power at its resonance is discussed.     

A CuBr laser with high efficiency in the double-pumping-pulse mode

The results of examination of characteristics of a CuBr laser operated in the double-pumping-pulse mode with a lasing pulse repetition rate of 50 Hz are presented. The potential to enhance the laser efficiency by choosing the optimum voltages of dissociation and excitation pulses and time delay values is discussed. It is confirmed that a more than twofold increase in the laser efficiency may be achieved through optimization and matched injection of the excitation-pulse energy into the active medium plasma. A laser efficiency as high as 2.6% (with respect to an excitation pulse) with an average power of 16 mW, an energy of 0.32 mJ, a halfamplitude laser pulse duration of 40 ns, and a time delay of 150 μs is demonstrated. The maximum average radiation power is 37 mW with an energy of 0.7 mJ and a laser efficiency of 0.7% at an energy density of 24 (2.7) mJ/cm³ of a dissociation (excitation) pumping pulse.     

The effect of passive Q-switching observed in an erbium-doped fiber laser at a low pumping power

The effect of passive Q-switching was observed in an erbium fiber laser at a pumping power below 100 mW. The phenomenon is explained by a cascade process of the Rayleigh light scattering and the induced Mandelshtam-Brillouin scattering in a fiber resonator of the laser. In the Q-switched mode, the laser produced giant output pulses with a duration below 15 ns, a peak power up to 200 W, and a repetition period of 300–500 μs. The proposed Q-switching mechanism is inferred from the characteristic features of the laser pulse oscillograms measured at a ∼1 ns resolution. Previously, this effect was observed only in high-power fiber lasers at a pumping power of ∼2 W.     

High peak-power single-frequency pulses using multiple stage, large core phosphate fibers and preshaped pulses

We have developed a monolithic high power pulsed fiber laser in a master oscillator power amplifier (MOPA) configuration, which is capable of reaching 0.38 mJ pulse energy and 128 kW peak power for 3 ns pulses at ~1550 nm while maintaining transform-limited linewidth. The fiber laser pulse seed was achieved by directly modulating a CW single-frequency fiber laser using an electro-optic modulator. We used an arbitrary waveform generator to preshape the fiber laser pulses before amplification to avoid pulse steepening and dynamic gain saturation. Single-mode, polarization maintaining highly Er/Yb codoped large core phosphate fibers were used in the power amplifier stages to scale the transform-limited fiber laser pulses, avoiding any nonlinearities.     

Semiconductor saturable absorber mirror passively Q-switched fiber laser near 2 μm

A passively Q-switched fiber laser near 2?μm is achieved with a semiconductor saturable absorber mirror (SESAM) as a saturable absorber. Stable Q-switched pulses are generated from an extremely compact setup with a central wavelength of 1958.2?nm. Under the bidirectional pump configuration, the repetition rate of the fiber laser can be widely tuned from 20 to 80?kHz by increasing the pump power at the same time the pulse width decreases from 1?μs to 490?ns. When the incident pump power is 1.3?W, the average output power, the pulse repetition rate, the pulse width, and the highest single pulse energy are 91?mW, 80?kHz, 490?ns, and 1.14?μJ, respectively. To further optimize the system configuration, the pulse width can be reduced to 362?ns when the cavity length is reduced.     

摩擦系数变化式压电叠堆惯性直线驱动器

以压电叠堆和质量块组成的压电叠堆振子为动力元件,通过利用驱动器向左运动和向右运动时接触足与接触面摩擦系数的不同,设计并制作完成了一套摩擦系数变化式压电叠堆惯性直线驱动器．分析了该驱动器的工作原理并对驱动器的运动情况作了详细分析．搭建了专用测试系统,并采用该系统对摩擦系数变化式压电叠堆惯性直线驱动器进行了性能测试．试验结果表明：当频率为10Hz时,该试验装置最小稳定步长为0．19μm,最大移动速度为11．82μm／s,最大承载能力不低于900g．     

Intracavity frequency doubling and Q switching in diode-laser-pumped Nd:YVO(4) lasers

A highly efficient and compact Nd:YVO(4) laser is proposed. In cw operation, a single-longitudinal-mode output of 95 mW and a multilongitudinal-mode output of 435 mW have been observed at 1.06 μm with a 1-W diode laser. Using a KTP crystal in the short laser cavity, a green output of 105 mW was generated. A Q-switched pulse with a peak power of 230 W and a pulse width of 8 ns was obtained with the intracavity KTP crystal, which was used as both an electro-optic Q switch and a frequency doubler.     

Tunable graphene-based Q-switched erbium-doped fiber laser using fiber Bragg grating

A graphene-based Q-switched erbium-doped fiber laser (EDFL) with a tunable fiber Bragg grating (TFBG) acting as a wavelength tuning mechanism is proposed and demonstrated. The proposed setup utilizes a newly-developed ‘ferrule-to-ferrule transfer’ technique to obtain a single graphene layer that allows for Q-switch operation in the EDFL using a highly doped-gain medium. A TFBG is used as a wavelength tuning mechanism with a tuning range of 10 nm, covering the wavelength range from 1547.66 nm to 1557.66 nm. The system has a wide repetition rate range of over 206.613 kHz from 1.387 kHz to 208.000 kHz with pulse durations of between 94.80 μs to 0.412 μs. The laser output is dependent on the pump power, with energy per pulse of 4.56 nJ to 16.26 nJ. The system is stable, with power and wavelength variations of less than 0.47 dBm and 0.067 nm. The output pulse train is free from self-mode locking and pulse jitters.     

Photothermal delivery of microscopic objects via convection flows induced by laser beam from fiber tip

We report a photothermal delivery of microscopic objects based on convection flows at the surface of water. The convection flows were induced by photothermal effect through a laser beam of 1.55 μm wavelength from a fiber tip. A 206 μm diameter oil drop was delivered forward and backward by changing the laser beam at a power of 28.5-40 mW. In addition, the delivery has been further demonstrated with a cluster of carbon and red blood cells at the laser powers of 14 and 20 mW, respectively.     

Pure antimony film as saturable absorber for Q-switched erbium-doped fiber laser

This paper reports on the use of Antimony (Sb) polymer film to generate stable Q-switching pulses in Erbium-doped fiber laser (EDFL) cavity. The SA is fabricated by coating a thin layer of Sb on a polyvinyl alcohol (PVA) film through physical vapour deposition (PVD) process. A 1 × 1 mm area of the film SA is cut and integrated into between two fiber ferrules inside the laser cavity for intra-cavity loss modulation. Self-starting and stable Q-switched pulses are obtained within a pump power range from 60 to 142 mW. Within this range, the repetition rate increases from 70.82 to 98.04 kHz, while pulse width decreases from 7.42 to 5.36 μs. The fundamental frequency signal-to-noise ratio of the pulse signal is 74 dB, which indicates the excellent stability of the pulses. The maximum output power and pulse energy are 8.45 mW and 86.19 nJ, respectively. Our demonstration shows that Sb film SA capable of generating stable pulses train operating at 1.55-micron region.     

MEH-PPV organic material as saturable absorber for Q-switching and mode-locking applications

ABSTRACT

Q-switched and mode-locked pulse generation in Erbium-doped fiber lasers (EDFLs) are demonstrated using Poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) organic semiconductor material as a saturable absorber (SA) for the first time. The MEH-PPV was prepared in the form of a thin film having a modulation depth of 12% and saturation intensity of 40?MW/cm². The SA was placed in a laser cavity to produce a stable Q-switched operating at 1564.0?nm. The maximum repetition rate of 78.62?kHz, minimum pulse width of 3.54?µs and maximum pulse energy of 59.45?nJ were attained at 125.2?mW pump power. On the other hand, by incorporating an additional 100?m long single mode fiber, the mode locked EDFL self-started as the pump power was raised above 125.2?mW. The soliton pulse was obtained due to the enhancement of the nonlinearity in the cavity. The mode-locked laser operated at 1568.5?nm with a fixed repetition rate of 1.859?MHz and pulse width of 2.97?ps.     

Q-switched thulium-doped fiber laser operating at 1940 nm region using a pencil-core as saturable absorber

Q-switched thulium-doped fiber laser (TDFL) is demonstrated using pencil-core flakes as a saturable absorber (SA) for the first time. The SA was fabricated by exfoliating pencil-core flakes on adhesive tape surface, then repeatedly folded over the tape until the flakes homogenously deposited on the tape. A small piece of the tape is sandwiched between two ferrules and incorporated in TDFL cavity to realize a stable Q-switching pulse train. By increasing the 1552-nm pump power from 389 to 431 mW, the repetition rate of the TDFL increases from 14.95 to 34.60 kHz while the pulse width decreases from 6.70 to 4.69 μs. The maximum pulse energy of 46.05 nJ is generated with repetition rate and pulse width of 21.25 kHz and 6.27 μs, respectively. To the best our knowledge, this is a first demonstration SA from mundane object as alternative to commercial bulk graphite for Q-switched fiber laser.     

Passively Q-switched fibre laser utilizing erbium-doped fibre saturable absorber for operation in C-band region

In this paper, a stable and robust all-fibre passively Q-switched erbium-doped fibre laser (EDFL) emitting at 1558?nm is described. The proposed laser utilizes an 11?cm long erbium-doped fibre as saturable absorber (SA). The fibre SA features a linear optical absorption of about 13?dB in the Q-switched EDFL operating regime. By elevating the input pump power from the threshold of 60?mW to the maximum available power of 142?mW, a pulse train with a maximum repetition rate of 86?kHz, minimum pulse width of 3.39?µs, maximum average output power of 10.5?mW, maximum pulse energy of 122?nJ and maximum peak power of 36?mW are obtained. The signal to noise ratio (SNR) of the spectrum is measured to be around 70?dB. This fibre SA is simple, reliable, compact and alignment free. Thus it is suitable for making a portable pulse laser source.     

Wideband tunable Q-switched fiber laser using graphene as a saturable absorber

An ultra-wide wavelength tuning range, which covers three different band regions consisting of the S-, C-, and L-bands, is proposed and demonstrated for a graphene-based Q-switched erbium-doped fiber laser using a tunable bandpass filter as the wavelength tuning and filtering mechanism. A 3?m length of erbium-doped fiber is used as the gain medium in a ring laser cavity configuration, with absorption coefficients of between 11 and 13 dB?m^?1 at 980?nm and about 18?dB?m^?1 at 1550?nm. The tuning range of the Q-switching pulses covers a wide wavelength range of 58?nm, which spans from 1512.5?nm to 1570.5?nm. In addition, the lasing and Q-switching thresholds are considerably low, with respective values of ～11.0?mW and ～18.4?mW. A repetition rate of 55.3?kHz is obtained at the maximum pump power of 100.4?mW, together with pulse width and pulse energy of 1.6?μs and 25.8?nJ, respectively.     

Cavity-length optimization for high energy pulse generation in a long cavity passively mode-locked all-fiber ring laser

In order to achieve higher pulse energy in a passively mode-locked fiber ring laser, a long cavity length is commonly implemented. However, a long cavity operating in the anomalous dispersion regime also leads to pulse broadening, which reduces the average pulse power. In this paper, the trade-off between cavity length and average pulse power is investigated with the aim of optimizing the cavity length to achieve maximum pulse energy. Numerical simulation results, presented here, indicate that there exists an optimum cavity length for which the pulse energy is maximum and the optimum length shifts as the pump power changes. The simulation results for a pump power of 500 mW are verified by measurements carried out on a long cavity nonlinear polarization rotation mode-locked all-fiber ring laser operating in the anomalous dispersion regime. With a repetition rate of 266 kHz for the dissipative solitons, we achieve a pulse energy of 139.1 nJ for a cavity length of 700 m. Higher pulse energy can be expected by using a pump laser diode with higher pump power.     

A generation of 2 μm Q-switched thulium-doped fibre laser based on anatase titanium(IV) oxide film saturable absorber

We demonstrate a Q-switched thulium-doped fibre laser operating at approximately 1935 nm wavelength using anatase titanium(IV) oxide (TiO₂) embedded in polyvinyl alcohol as the passive newly saturable absorber (SA). The film has absorption loss of 3.5 dB and modulation depth of 33%. It is sandwiched between two fibre ferrules in a ring laser cavity to produce self-started pulse train with a repetition rate that is tuned from 30.12 to 36.96 kHz as the 1552-nm pump power is increased from 289 to 485 mW. At maximum pump power, the laser produced a Q-switching pulse train with pulse duration, output power, pulse energy and peak power of 1.91 μs, 11 mW, 0.3 μJ and 146 mW, respectively. These results show that the TiO₂ is a new potential SA material for pulsed laser applications.     

光纤饱和吸收体稳频窄线宽光纤激光器

结合光纤饱和吸收体与光纤光栅法布里-珀罗标准具,研制出了全光纤结构1550nm单频窄线宽掺铒光纤环形激光器.采用两个976nm激光二极管双向抽运作为抽运源,高掺杂浓度铒光纤作为增益介质,以行波腔消除空间烧孔效应,利用光纤光栅法布里-珀罗标准具窄带选模特性,以10m长低掺铒光纤饱和吸收体稳频,得到了十分稳定的窄线宽激光输出.激光器抽运阈值功率21mW,在抽运光功率为145mW时输出光功率39mW,斜率效率30%,信噪比大于50dB.采用延迟自外差方法精确测量光纤激光器线宽小于10kHz.     

Diode-laser-pumped tunable 896-939.5-nm neodymium-doped fiber laser with 43-mW output power

A diode-laser-pumped neodymium-doped fiber laser is presented. For a launched pump power of 85 mW, the fiber laser had a cw output power of 43 mW, which is approximately an order of magnitude greater output power than any previously reported diode-pumped neodymium fiber laser operating on the(4)F(3/2)-(4)I(9/2) transition, which covers the 900-950-nm region. The fiber laser had a threshold power of 10 mW and a slope efficiency of 58% with respect to launched pump power. Tuning with a diffraction grating was obtained from 896 to 937 nm with narrow-band output powers as high as 32 mW. Emission was also obtained at 939.5 nm with use of a fiber Bragg grating as the output reflector.     

Mode-locked soliton erbium-doped fiber laser using a single-walled carbon nanotubes embedded in polyethylene oxide thin film saturable absorber

We demonstrate a simple, compact, and low cost mode-locked erbium-doped fiber laser (EDFL) using a single-walled carbon nanotubes (SWCNTs) embedded in polyethylene oxide (PEO) thin film as a passive saturable absorber (SA). The film with a thickness of 50?μm was fabricated using a prepared homogeneous SWCNT solution with 0.1% loading percentage, which was mixed with a diluted PEO solution and casted onto a glass Petri dish to form a thin film by evaporation technique. The film is sandwiched between two fiber connectors to construct a SA, which is then integrated in an EDFL cavity to generate a self-started stable soliton pulses operating at 1558?nm. The soliton pulse starts to lase at pump power threshold of 17.6?mW with a repetition rate of 50?MHz, pulse width of 0.67?ps, average output power of 0.158?mW, pulse energy of 3.16?pJ, and peak power of 4.43?W.