50-GHz repetition-rate, 280-fs pulse generation at 100-mW average power from a mode-locked laser diode externally compressed in a pedestal-free pulse compressor

280-fs pedestal-free pulses are generated at average output powers exceeding 100 mW at a repetition rate of 50 GHz by compression of the output of a mode-locked laser diode (MLLD) by use of a pedestal-free pulse compressor (PFPC). The MLLD consists of a monolithically integrated chirped distributed Bragg reflector, a gain section, and an electroabsorption modulator. The PFPC is composed of a dispersion-flattened dispersion-decreasing fiber and a dispersion-flattened dispersion-imbalanced nonlinear optical loop mirror. Frequency modulation for linewidth broadening is used to overcome the power limitation imposed by stimulated Brillouin scattering.     

54-fs, 10-GHz soliton generation from a polarization-maintaining dispersion-flattened dispersion-decreasing fiber pulse compressor

A 10-GHz train of nearly transform-limited 54-fs soliton pulses was generated by adiabatic compression of the output of a mode-locked fiber laser with a polarization-maintaining dispersion-flattened dispersion-decreasing fiber. The peak-to-pedestal ratio exceeded 23 dB. At high input powers, the pulse width was reduced to as short as 43 fs, although the wings of the pulse were degraded and the jitter increased. The compression properties are different for the two polarization axes, owing to their different dispersion characteristics. The output polarization exhibits no drift.     

100-fs diode-pumped Yb:KGW mode-locked laser

We have developed a mode-locked diode-pumped Yb:KGW laser generating 100-fs pulses with an output power of 126 mW. The corresponding optical spectrum has a 13.4-nm FWHM bandwidth and is centered at 1037.4 nm. In the multiple-pulsing regime, bound states of solitons with rotating phase difference and separated by 917.5 fs were observed. We compare the performance of the Yb:KGW crystal to that of an Yb:KYW crystal with the same thickness and Yb concentration. PACS 42.55.Rz; 42.65.Re; 42.65.Tg     

High-power sub-100-fs UV pulse generation from a spectrally controlled KrF laser

High-power sub-100-fs UV pulses were generated from a KrF excimer laser by spectral control and chirped-pulse amplification. The spectral width was broadened to 1.6 nm, resulting in 72-fs, nearly transform-limited pulses. The average output powers at 1 kHz were 0.6 and 1.2 W for pulse widths of 72 and 110 fs, respectively.     

Parabolic pulse generation by use of a dispersion-decreasing fiber with normal group-velocity dispersion

We propose a new method for generating a parabolic pulse by use of a dispersion-decreasing fiber with normal group-velocity dispersion. When a hyperbolic dispersion-decreasing structure is employed, the pulse evolves into a linearly chirped pulse with an exact parabolic intensity profile without radiating dispersive waves. The highly linear chirp in the parabolic pulse allows for efficient and high-quality pulse compression.     

Parabolic pulse generation in a dispersion-decreasing solid-core photonic bandgap Bragg fiber

We analyze the interplay of nonlinearity and dispersion in a dispersion-decreasing photonic bandgap Bragg fiber as a new platform for generating parabolic pulses. A suitably designed linearly tapered, low-index-contrast, solid-core Bragg fiber - amenable to fabrication by conventional modified chemical vapor deposition technology - is shown to yield stable parabolic pulses. The fiber design was optimized through a simple and accurate transfer-matrix formalism and pulse evolution was studied by the well-known split-step Fourier method. Our study revealed feasibility of generating parabolic pulses in such a dispersion-decreasing Bragg fiber of length as short as 1 m. We have also studied the effect of third order dispersion on generated parabolic pulse, which is an important deteriorating factor in such applications. The effective single-mode operation of the proposed device is achieved through appropriate tailoring of the outer cladding layers.     

输出近百纳焦耳脉冲能量的光子晶体光纤锁模激光器

设计并搭建了一种支持百纳焦耳量级的单脉冲能量输出的锁模光纤激光器.激光器基于σ型腔结构,采用掺Yb偏振型大模场面积光子晶体光纤作为增益介质,利用半导体可饱和吸收镜实现自启动锁模.激光器内没有色散补偿机理,使其工作在全正色散锁模状态.通过在谐振腔内引入多通长腔使激光器的重复频率降低至11.1 MHz,直接获得了平均功率为1.08 W,单脉冲能量为 97 nJ,脉冲宽度为4.17 ps的稳定锁模脉冲输出,经腔外色散补偿,脉冲宽度压缩至740 fs.     

Nearly transform-limited optical pulse from a passively mode-locked laser diode

An optical ultra-short pulse train with a duration of 2.9 ps was successfully generated from a passively mode-locked laser diode. The time-bandwidth product was 0.43, and it was very close to the transformlimited value of a Gaussian waveform. The highest peak power of 10 mW in an InP-based passively mode-locked laser has been achieved. The laser is promisng as an optical source for an ultra-high-speed bit rate transmission system, especially for the optical time division multiplexing (OTDM) system.     

High-energy soliton pulse generation with a passively mode-locked Er/Yb-doped multifilament-core fiber laser

We report the generation of high-energy short pulses from a mode-locked erbium/ytterbium-doped large-mode-area multifilament-core fiber laser operating in the purely anomalous dispersion regime. The self-starting fiber laser emits 400 mW of average output power at a pulse repetition rate of 44 MHz, corresponding to a pulse energy of 9.1 nJ. The laser produces near transform-limited output pulses with pulse duration of 1.6 ps, corresponding to 5 kW peak power. This new type of low-nonlinearity fibers demonstrates the power and energy scaling potential of fiber-based short pulse lasers in the eye-safe region.     

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.     

Switchable and tunable dual-wavelength ultrashort pulse generation in a passively mode-locked erbium-doped fiber ring laser

A simple switchable and tunable dual-wavelength passively mode-locked erbium-doped fiber ring laser based on nonlinear polarization rotation (NPR) effect is proposed and experimentally demonstrated. The NPR effect effectively induces wavelength- and intensity-dependent loss to readily implement stable dual-wavelength passively mode-locked operation. The wavelength switching and tuning of the dual-wavelength ultrashort pulse laser are achieved only by appropriately rotating the polarization controllers. The side-mode suppression ratio of the output pulse is larger than 41 dB over a wavelength-tuning range of 43.4 nm. Moreover, triple-wavelength ultrashort pulse can also be observed.     

Dual-stage soliton compression of a self-started additive pulse mode-locked erbium-doped fiber laser for 48 fs pulse generation

A dual-stage single-mode fiber (SMF) and large-effective-area fiber (LEAF) link for generating 48 fs pedestal-free pulses from a 40 MHz self-started additive pulse mode-locked erbium-doped fiber laser (APM-EDFL) with output peak power and pulse energy of 16 kW and 500 pJ, respectively, is demonstrated. With the SMF+LEAF link, a maximum pulse-width compression ratio of 7 and an optimized pulse-energy confining ratio of up to 85% can be achieved, and the soliton self-frequency shift effect of the APM-EDFL pulse can be greatly suppressed.     

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.     

Stable noise-like pulse generation in all-PM mode-locked Tm-doped fiber laser based on NOLM

A stable noise-like(NL) mode-locked Tm-doped fiber laser(TDFL) relying on a nonlinear optical loop mirror(NOLM) was experimentally presented. Different from the previous NL mode-locked TDFL with NOLM, the entire polarizationmaintaining(PM) fiber construction was utilized in our laser cavity, which makes the oscillator have a better resistance to environmental perturbations. The robust TDFL can deliver stable bound-state NL pulses with a pulse envelope tunable from～14.1 ns to～23.6 ns and maximum pulse energy of ～40.3 n J at a repetition rate of ～980.6 k Hz. Meanwhile, the all-PM fiber laser shows good power stability(less than ～0.7%) and repeatability.     

Gigahertz-repetition-rate mode-locked fiber laser for continuum generation

We report direct generation of <500-fs pulses at a 1-GHz rate from a self-starting passively mode-locked fiber laser by regeneratively synchronizing the pulses with a phase modulator. The pulses are amplified and passed through a dispersion-decreasing fiber and a normal-dispersion supercontinuum fiber. The resulting continuum is wider than 350 nm.     

Femtosecond pulse generation in a linear passive mode-locked dye laser

The femtosecond pulse generation in a c.w. pumped linear passive mode-locked rhodamine 6G-DODCI (3,3-diethyloxadicarbo cyanine iodide) dye laser is studied experimentally. Colliding pulse mode-locking (CPM) is achieved by placing the saturable absorber jet in the centre of the linear ring resonator. The laser performance is studied as a function of the saturable absorber concentration and of the absorber jet detuning from the central position (CPM position). Without a prism pair in the resonator pulse durations down to 140 fs were obtained. Detuning the absorber jet from the CPM position resulted in a trailing pulse tail ofcirca 900 fs duration. The dependence of the laser performance on the prism pair positioning is investigated experimentally and analysed theoretically. At the prism pair balanced position, stable pulses of about 50 fs duration were generated independent of the lateral detuning of the absorber jet out of the resonator centre. The dependence of the laser wavelength on the absorber concentration is compared with theoretical predictions. In an appendix the ray-tracing inside the linear resonator is simulated by an ABCD matrix calculation for Gaussian beams.     

Scalar soliton generation in all-polarization-maintaining, graphene mode-locked fiber laser

All-polarization-maintaining, self-starting Erbium-doped fiber laser based on graphene-saturable absorber is presented. Scalar soliton pulses with 570 fs duration and 114.1 MHz repetition rate were achieved at a 1557 nm center wavelength and with 6 nm bandwidth. The graphene-saturable absorber was formed by mechanical exfoliation of pure graphite. The laser was environmentally stable and could operate for long periods of time with linearly polarized output and degree of polarization at the level of 98%.     

高重复频率锁模光纤激光器及其超连续谱产生

设计并实验研究了一种结构简单的主动调制锁模高重复频率窄脉宽光纤激光器。采用窄线宽连续激光调制4 GHz高重频后,通过拉曼增益孤子压缩效应将脉宽由27 ps压窄至2.6 ps。该高重频锁模激光泵浦一段300 m长高非线性光纤,同时脉冲被展宽至7.4 ps。产生的超连续谱平坦度20 dB宽带可达250 nm,功率波动为±0.2 dB。     

Near-infrared subpicosecond pulse generation in a synchronously mode-locked cw dye laser

Tunable subpicosecond pulses have been obtained from a synchronously mode-locked Oxazine-1 dye laser by tandem pumping with output pulses of a mode-locked Rhodamine 6G dye laser. The effects of cavity detuning on the pulse-width and the second harmonic power (the peak intensity of the autocorrelation trace) have been investigated. The experimental results are found to be in good agreement with those predicted by a recent model analysis.