Continuum suppressed, uniformly repetitive 136 fs pulse generation from an erbium-doped fibre laser with nonlinear polarisation rotation

A new type of femtosecond erbium-doped fibre laser with nonlinear polarisation rotation is presented, in which a polariser is installed at a point-symmetric position against a polarisation-sensitive optical isolator in the ring laser cavity. This technique enables one to remove the continuum (DC component) in the oscillation waveform completely and to obtain a stable pulse train as short as 136-145 fs with a 56 MHz repetition rate.<>     

87 nm bandwidth noise-like pulse generation from erbium-doped fibre laser

Demonstrated is the operation of a passively modelocked erbium-doped fibre laser in noise-like mode and the generation of the pulse train with a bandwidth much wider than the gain bandwidth. Also demonstrated is super-continuum (SC) generation by launching the noise-like pulse into a highly nonlinear fibre and it is shown that the ultra-broadband SC spectra of over 960 nm is obtained by using the noise-like pulse instead of ultrashort pulses.     

Chirp pulse transmission through a single-mode fibre

A pulse-compression phenomenon of a chirp pulse transmitted through a long single-mode fibre is presented. The chirp pulse is obtained by using a carrier density change in a DFB laser diode. The pulse width is 1.7 ns at the single-mode-fibre input and is compressed to 0.35 ns after a 104 km transmission at 1.54 ?m wavelength.     

Picosecond optical pulse compression from gain-switched 1.3 ?m distributed-feedback laser diode through highly dispersive single-mode fibre

The first demonstration to compress the linearly chirped optical pulses from a gain-switched distributed-feedback laser diode (DFB-LD) is described at 1.3 ?m wavelength. By travelling through a highly dispersive single-mode fibre with 48 ps/nm normal dispersion, a 26 ps (FWHM) pulse having red-shift frequency chirping of 85 GHz (FWHM) is compressed to 8.3 ps with the time-bandwidth product of 0.71.     

频率分辨光学开关法测量飞秒脉冲

阐述了频率分辨光学开关法测量飞秒脉冲的原理,详细分析了模式尺寸效应和非线性效应对飞秒脉冲测量的影响.构建了一台用于飞秒脉冲测量的二次谐波-频率分辨光学开关装置,利用该装置对谐振腔输出的飞秒脉冲及压缩后的脉冲进行了测量.得到了飞秒脉冲的时间宽度及光谱宽度、电场及其相位在时域和频域的详细信息.谐振腔直接输出脉冲的时间宽度为56 fs,光谱宽度为27 nm,时间带宽积为0.686,算法中的最小误差为0.001792.脉冲压缩后的测量结果为27 fs,光谱宽度为92 m,时间带宽积为1.27,算法误差为0.0093289.     

Brillouin fibre laser with 20 m-long photonic crystal fibre

Brillouin fibre laser is demonstrated using a very short length of photonic crystal fibre (PCF). A simple ring resonator is used in the experiment which consists of a 20 m long highly nonlinear PCF and 49 cm long Bismuth-based erbium-doped fibre (Bi-EDF). The proposed Brillouin laser is able to generate up to 3 Stokes and 3 anti- Stokes lines in the 1560 nm region at a channel spacing of 0.09 nm.     

All laser diode compression of 5 GHz picosecond pulses using cross-phase modulation in optical fibre

5 GHz pulses from a mode-locked semiconductor laser diode have been compressed from 10.5 to 4.6 ps by means of cross-phase modulation using a separate optically amplified mode-locked laser diode. By tuning the laser wavelengths symmetrically about the 1.55 mu m dispersion zero of an 11 km length of fibre, the effect of group velocity dispersion is minimised, ensuring that the fibre is used efficiently. The spectral broadening induced by the cross-phase modulation enables pulse compression in a dispersive fibre.<>     

Fibre integrated femtosecond sources based on soliton generation from CW noise

The development of simple, fibre integrated femtosecond soliton sources based on the propagation of CW noise through a highly nonlinear fibre is reported. It is shown that pulse compression can be obtained in this format through the use of Raman amplification. A method of wavelength extension to the visible using microstructure is proposed     

Optical pulse compression in 1.5 μm wavelength region usinglarge-positive-dispersion fibre and grating pair

Optical pulse compression at 1.5 μm has been conducted. 20 ps (FWHM) optical pulses from a Tl:KCl-colour-centre laser were compressed into pedestal-free 1.2 ps pulses using a large-positive-dispersion fibre and a grating pair. In addition, 280 fs pulses were obtained from the resultant 1.2 ps through the soliton compression effect in a negative-dispersion fibre     

利用块状介质进行飞秒强激光脉冲的腔外压缩

高强度飞秒激光脉冲的腔外压缩是获得高次谐波阿秒脉冲驱动源的必要手段.实验研究了超强超短飞秒激光脉冲在经过块状介质后的光谱展宽和色散补偿压缩现象.单脉冲能量0.26 mJ,脉宽50 fs的激光脉冲经透镜在空气中聚焦后再入射到块状材料上,出射脉冲光谱被展宽到接近40 nm.由于在块状材料中的自聚焦效应,出射光束质量变好并保持较小的空间啁啾.利用熔融石英棱镜对补偿带有正色散的出射脉冲,最后得到＞0.1 mJ,19 fs的压缩脉冲.利用SPIDER装置测量了出射脉冲的脉宽和光谱相位.整个系统的能量效率大约为35%,压缩后的激光脉冲具有很好的空间分布和平滑的时域包络.实验结果实现了利用块状材料对飞秒激光脉冲的腔外压缩,这种方法将适用于对更高能量飞秒脉冲的压缩.     

Blue light generation in holey fibre using frequency doubled fibre pump source

A report is presented on the efficient generation of 18 mW of 428 nm light by propagating frequency doubled 780 nm pulses from an all-fibre integrated picosecond pulse source with kW level peak power through a length of highly nonlinear holey fibre. The wavelength conversion process is attributed to resonant coupling between solitons and dispersive radiation.     

离散效应对光子晶体光纤中飞秒脉冲压缩影响

为了研究离散效应对光子晶体光纤中飞秒信号脉冲压缩的影响,采用分步傅里叶方法数值求解耦合的非线性薛定谔方程,模拟了双飞秒脉冲在光子晶体光纤中的非线性传输过程;计算和分析了离散效应和非同步耦合对信号脉冲压缩的影响。结果表明,当抽运脉冲在反常色散区进行抽运,而信号脉冲在正常色散区入射时,在群速度色散、3阶色散,自相位调制及交叉相位调制联合作用下,信号脉冲在传输过程中不仅被压缩且存在最佳光纤长度;离散效应导致信号脉冲压缩因子减小,所需最佳光纤长度增加以及压缩后的脉冲频谱呈现不对称,采用非同步耦合有利于改善信号脉冲的压缩质量。     

Vector bending sensors based on fibre Bragg gratings inscribed by infrared femtosecond laser

A direction-sensitive bend sensor in standard singlemode fibre is demonstrated for the first time based on an axially-offset fibre Bragg grating, directly written by an infrared femtosecond laser.     

Picosecond pulse generation with high extinction ratio employing electroabsorption modulator, fibre compressor, and self-phase-modulation-based pulse reshaper

A wavelength-tunable 3.5 ps pulse generator, which employs an electroabsorption modulator (EAM), a fibre pulse compressor, and a self-phase-modulation (SPM)-based pulse reshaper, is developed. An EAM directly generates 21 ps pulses at a repetition rate of 10 GHz, which are compressed to 6 ps by a fibre pulse compressor. An SPM-based pulse reshaper then eliminates the large pedestal of the compressed pulses. Thus, 3.5 ps pulses with extinction ratio larger than 27 dB and timing jitter as small as 150 fs are obtained.     

10fs以下的飞秒激光脉冲的非线性传输

给出了具有几个光振荡周期长的飞秒激光脉冲在不考虑群速色散的情况下传输方程的解,用数值方法模拟了飞秒激光脉冲的非线性传输,考察了非线性效应对脉冲形状和频谱的影响,得到和慢变振幅近似下不完全一致的结论。     

光子晶体光纤中基于交叉相位调制的脉冲压缩

为了研究飞秒双脉冲在光子晶体光纤不同色散区的非线性传输过程,采用分步傅里叶方法求解耦合的非线性薜定谔方程组,并进行了理论分析。讨论了不同抽运功率、不同抽运脉冲啁啾参量以及不同脉宽比对信号脉冲压缩的影响。结果表明,基于交叉相位调制效应,弱信号脉冲不仅能够被压缩,而且光纤存在最佳压缩长度。增大抽运脉冲输入功率,选取正啁啾抽运脉冲,可以得到更大的信号脉冲压缩因子,同时最佳光纤长度减小。另外,不同的脉冲宽度对信号脉冲的压缩产生大的影响,较窄脉宽的抽运脉冲易于产生较短的压缩信号脉冲。这一结果对用光子晶体光纤压缩弱信号脉冲提供了理论参考。     

具有几个光振荡周期长的飞秒脉冲在单模光纤中的传输

发展了飞秒光脉冲在光纤中的传输理论,给出了具有几个光振荡周期长的飞秒脉冲在单模光纤中的传输方程,对方程作了数值解,模拟了具有几个光振荡周期的飞秒脉冲在单模光纤中的非线性传输。     

Coherent combining of two pulsed fibre lasers in phase modulated mutually coupled fibre laser array

A scalable architecture for coherent combining of pulsed fibre lasers is reported. Stable synchronous and phase-locked pulsed fibre laser beams are generated in a phase modulated mutually coupled fibre laser array. The mechanism for generating a pulsed laser is different from previous Q-switching, modelocking or pump modulation methods. Two pulsed fibre lasers are coherently combined with 0.48 J pulse energy at the repetition rate of 115 kHz. The repetition rate can be controlled by adjusting the pump current. The combining efficiency of the two pulsed fibre lasers reaches 90 and the fringe contrast is larger than 40 .     

Technique to generate equal amplitude, higher-order optical pulsesin rational harmonically modelocked fibre ring lasers

A novel technique of pulse amplitude equalisation in higher-order optical pulses in a rational harmonically modelocked fibre ring laser is proposed and demonstrated. The combination of intracavity optical filtering, and even-order modulation sideband generation using nonlinear characteristics of a Mach-Zehnder intensity modulator can effectively eliminate pulse amplitude instability at higher-order rational harmonic modelocking. The generated optical pulse trains exhibit equal amplitudes with a high degree of spectral purity in terms of a large suppression of supermode noise, low amplitude noise, phase noise, and timing jitter