基于混合锁模的耗散孤子掺铒光纤激光器

从一种简单、全光纤结构的混合被动锁模掺铒光纤激光器中,得到了高稳定性、宽光谱的耗散孤子。激光器结合了半导体可饱和吸收体和非线性偏振旋转两种锁模机制,并运行在正常色散区内;通过色散管理,激光器能产生光谱宽度39.1 nm和时域宽度178 fs的孤子脉冲序列。激光输出的中心波长为1.55 μm,重复频率约为34.3 MHz,单脉冲能量在0.33 nJ左右。与此同时,激光器的斜效率也约等于15.5%;室温工作下,激光器能实现自启动锁模,且运行在稳定单脉冲输出状态的时长在15 h以上。     

Dual-wavelength dissipative soliton operation of an erbium-doped fibre laser using a nonlinear polarization rotation technique

We report on the generation of dual-wavelength dissipative solitons in a passively mode-locked fibre laser with a net normal dispersion using the nonlinear polarization rotation (NPR) technique. Taking the intrinsic advantage of the intracavity birefringence-induced spectral filtering effect in the NPR-based ring laser cavity, the dual-wavelength dissipative solitons are obtained. In addition, the wavelength separation and the lasing location of the dual-wavelength solitons can be flexibly tuned by changing the orientation of the polarization controller.     

Different operation states of soliton pulses in an erbium-doped fibre ring laser

We report on the experimental observation of soliton pulses in an erbium doped fibre ring laser. The passive mode-locking is achieved using the nonlinear polarization rotation technique. By adjusting the pump power and the intracavity polarization controllers, a normal soliton, a stable 8th harmonic mode-locked pulse and a noise-like pulse have been observed in our laser. The experimental results revealed that the noise-like pulse is not suitable for the optical telecommunication, and in order to obtain the stable harmonic mode-locked soliton, a strong unstable CW laser field is necessary to mediate global soliton interaction. The formation mechanism of the harmonic mode-locked pulse has also been analysed.     

Sequential generation of self-starting diverse operations in all-fiber laser based on thulium-doped fiber saturable absorber

Self-starting Q-switching, Q-switched mode-locking and mode-locking operation modes are achieved sequentially in an all-fiber erbium-doped fiber laser with thulium-doped fiber saturable absorber for the first time. The central wavelengths of Q-switching, Q-switched mode-locking and mode-locking operation modes are 1569.7 nm, 1570.9 nm, and 1572 nm, respectively. The mode-locking operation of the proposed fiber laser generates stable dark soliton with a repetition rate of 0.99 MHz and signal-to-noise ratio of 65 dB. The results validate the capability of generating soliton pulse by doped fiber saturable absorber. Furthermore, the proposed fiber laser is beneficial to the applications of optical communication and signal processing system.     

Asymmetric multimode interference isolator based on nonreciprocal phase shift

This paper presents an asymmetric multimode interference-based (MMI) optical isolator, by utilizing the magneto-optical nonreciprocal phase shift (NPS). Equivalent beam propagation method (BPM) simulation of symmetric and asymmetric isolators are performed using configuration of Air/Ce:YIG/SiO₂ on silicon substrate for integration. The asymmetric isolator is found to be much more compact in size and efficient in isolation compared with symmetric isolator. Simulation results show that the isolation of asymmetric structure is 23.8 dB higher than that of symmetric one. It is mainly because both symmetric mode and anti-symmetric mode are excited in asymmetric structure and hence can interfere destructively. The proposed device may play an important role in the optical communication systems and photonic integrated devices.     

多模1064nm光纤激光器实现一维远失谐光晶格

采用1064 nm多模30 W连续光纤激光器, 搭建了一个周期为25 μm的一维远失谐光学晶格势场. 对铷原子进行磁光阱装载和偏振梯度冷却, 实现了铷冷原子团在光晶格中的装载. 借助于短程飞行时间法, 测量晶格中冷原子温度为20 μK, 为下一步实现量子信息存储实验奠定了基础.     

Zinc-oxide/PDMS-clad tapered fiber saturable absorber for passively mode-locked erbium-doped fiber laser

We propose and demonstrate a passively mode-locked erbium-doped fiber laser(EDFL) based on zincoxide/polydimethylsiloxane(Zn O/PDMS) saturable absorber(SA) that evanescently interacts with the light on a tapered fiber. The Zn O/PDMS composite is coated on the whole surface of the tapered fiber to guarantee the maximum efficiency of the SA device, with a measured insertion loss of 0.87 d B and a modulation depth of 6.4%. The proposed laser can generate soliton mode-locking operation at a threshold power of 33.07 m W. The generated output pulse yields a repetition rate and pulse width of 9.77 MHz and 1.03 ps, respectively. These results indicate that the proposed Zn O/PDMS-clad tapered fiber could be useful as an efficient, compatible, and low-cost SA device for ultrafast laser applications.     

Spatiotemporal mode-locked multimode fiber laser with dissipative four-wave mixing effect

The high degree of freedom and novel nonlinear phenomena of multimode fiber are attracting attention. In this work, we demonstrate a spatiotemporal mode-locked multimode fiber laser, which relies on microfiber knot resonance (MKR) via dissipative four-wave-mixing (DFMW) to achieve high-repetition-rate pulses. Apart from that, DFMW mode locking with switchable central wavelengths can also be obtained. It was further found that high pulse energy induced nonlinear effect of the dominant mode-locking mechanism transforming from DFMW to nonlinear Kerr beam cleaning effect (NL-KBC). The experimental results are valuable for further comprehending the dynamic characteristics of spatiotemporal mode-locked multimode fiber lasers, facilitating them much more accessible for applications.     

Femtoseconds soliton mode-locked erbium-doped fiber laser based on nickel oxide nanoparticle saturable absorber

We demonstrate a femtosecond mode-locked erbium-doped fiber laser(EDFL) using a nickel oxide(Ni O) as a saturable absorber(SA). Ni O nanoparticles are hosted into polyethylene oxide film and attached to fiber ferrule in the laser cavity. The Ni O-SA shows a 39% modulation depth with a 0.04 MW∕cm~2 saturation intensity. Our ring laser cavity based on erbium-doped active fiber with managed intracavity dispersion has the ability to generate ultrashort pulses with a full width at half-maximum(FWHM) of around 2.85 nm centered at 1561.8 nm.The pulses repeat at a frequency of 0.96 MHz and duration of 950 fs.     

Passively mode-locked erbium-doped fiber laser via a D-shape-fiber-based MoS_2 saturable absorber with a very low nonsaturable loss

We report on the generation of conventional and dissipative solitons in erbium-doped fiber lasers by the evanescent field interaction between the propagating light and a multilayer molybdenum disulfide(MoS_2) thin film. The MoS_2 film is fabricated by depositing the MoS_2 water–ethanol mixture on a D-shape-fiber(DF) repetitively. The measured nonsaturable loss, saturable optical intensity, and the modulation depth of this device are 13.3%, 110 MW/cm~2, and 3.4% respectively.Owing to the very low nonsaturable loss, the laser threshold of conventional soliton is as low as 4.8 mW. The further increase of net cavity dispersion to normal regime, stable dissipation soliton pulse trains with a spectral bandwidth of 11.7 nm and pulse duration of 116 ps are successfully generated. Our experiment demonstrates that the MoS_2-DF device can indeed be used as a high performance saturable absorber for further applications in ultrafast photonics.     

Observation of wavelength-switchable solitons in an all-polarization-maintaining erbium-doped fiber cavity based on graphene saturable absorber reflector

We present the generation of wavelength-switchable single-polarization solitons in an all-polarization-maintaining erbium-doped fiber laser mode-locked by a graphene saturable absorber. Ultrashort pulses centered at the wavelength of 1531.6 nm with the duration of 816 fs and centered at the wavelength of 1557.8 nm with the duration of 402 fs are separately obtained from the same fiber laser cavity. The cavity loss adjusted by the gold reflector plays a crucial role in wavelength switching.     

基于石墨烯的1064nm连续锁模超短脉冲激光器

介绍了利用沉积在增透镜上的石墨烯薄膜作为可饱和吸收体、808 nm激光二极管端面泵浦Nd∶YVO4晶体的1 064 nm连续锁模激光输出特性。采用W型折叠谐振腔结构,在808 nm泵浦功率为80 W时,有稳定的连续锁模脉冲输出,平均输出功率达到185 mW;当抽运功率增加到160 W时,获得了中心波长1 0634 nm、脉冲宽度为518 fs、重复频率为667 MHz、最大平均输出功率为323 mW的百飞秒量级超短脉冲激光输出。实验结果表明：石墨烯具有优良的可饱和吸收性,在1 064 nm波段能够实现高功率、百飞秒量级连续锁模脉冲激光输出。     

基于石墨烯的1 064 nm连续锁模超短脉冲激光器

介绍了利用沉积在增透镜上的石墨烯薄膜作为可饱和吸收体、808 nm激光二极管端面泵浦Nd∶YVO4晶体的1 064 nm连续锁模激光输出特性。采用W型折叠谐振腔结构,在808 nm泵浦功率为8.0 W时,有稳定的连续锁模脉冲输出,平均输出功率达到185 mW;当抽运功率增加到16.0 W时,获得了中心波长1 063.4 nm、脉冲宽度为518 fs、重复频率为66.7 MHz、最大平均输出功率为323 mW的百飞秒量级超短脉冲激光输出。实验结果表明:石墨烯具有优良的可饱和吸收性,在1 064 nm波段能够实现高功率、百飞秒量级连续锁模脉冲激光输出。     

Design and optimization of novel ultra-compact SOI multimode interference optical switch

In this paper, an ultra-compact 3 × 3 SOI multimode interference optical switch is presented. There is only one hyperbolic multimode waveguide in the switch. By changing the refractive index of one or two parts within the hyperbolic multimode waveguide, the switch can realize on and off functions between any pair of input and output ports. The various states of the switch were simulated and analyzed using the finite difference beam propagation method (FD-BPM), the structure parameters of the switch were also designed and optimized. The optimized switch has excellent properties and the whole size of the switch is less than 4 mm.     

孤子分子/类噪声脉冲可切换的混合锁模光纤激光器

不同类型脉冲之间的演化是被动锁模光纤激光器丰富动力学的体现。报道了一种可实现多种脉冲切换的混合锁模光纤激光器,当泵浦功率为400 mW时实现了孤子分子、谐波锁模、孤子簇之间的相互切换。增加泵浦功率至600 mW时获得了类噪声脉冲输出,对应的输出功率和单脉冲能量分别为15.2 mW和0.86 nJ。通过调节偏振控制器实现了类噪声脉冲中心波长从1 895 nm到1 930 nm可调谐。所搭建的激光器具有锁模脉冲可切换,波长可调谐,能自启动等优点。     

石墨烯可调谐被动调Q掺铒光纤激光器

基于光学沉积方法,制备了石墨烯可饱和吸收体,并利用此可饱和吸收体搭建了环形腔结构的被动调Q掺铒光纤激光器,实现了稳定的调Q激光脉冲输出,其重复频率为5.1~14.2 kHz,最窄激光脉冲宽度为8 s,最大平均功率为162.3 W,且通过调节偏振控制器,中心波长在1556~1558 nm可调。     

超低频率全正色散半导体可饱和吸收镜被动锁模光纤激光器

通过延长激光器环形腔腔长,利用高浓度掺杂的单模掺镱光纤,搭建了超低重复频率、全正色散结构的半导体可饱和吸收镜被动锁模光纤激光器。激光器的中心波长、重复频率、平均功率及单脉冲能量分别为1 064 nm,281.5 kHz,11 mW和39 nJ。为了稳定中心波长,实现自启动,激光器腔体内接入了一个带通滤波器。该激光器运行稳定,无调Q不稳定现象,极大减小了半导体可饱和吸收镜被损坏的机会。     

偶氮苯光致异构反饱和吸收的光学双稳态开关的理论研究

讨论了稳态条件下,反饱和吸收的偶氮苯分子光学双稳态的开关性能.先根据偶氮苯光致异构的理论模型,计算了影响偶氮苯反饱和吸收系数的因素,然后理论模拟其反饱和吸收的光学双稳态开关过程.模拟结果表明:基于偶氮苯分子的反饱和吸收可实现双稳态全光开关.增大偶氮苯分子的顺式基态吸收截面,减小热弛豫系数K能够降低反饱和吸收偶氮苯光学双稳态的开关能量;反式吸收截面大不利于反饱和吸收光学双稳态的形成.     

Semi-vectorial analysis of a compact wavelength demultiplexer based on the tapered multimode interference coupler

Based on a parabolically tapered multimode interference (MMI) coupler with a deep-etched SiO₂/SiON rib waveguide, a compact wavelength demultiplexer operating at 1.30 and 1.55\mum wavelengths is proposed and analysed by using three-dimensional semi-vectorial finite-difference beam propagation method (3D-SV-FD-BPM). The results show that a MMI section of 330.0\mum in length, which is only 76% length of a straight MMI coupler, is achieved with the contrasts of 42.3 and 39.2dB in quasi-TE mode, and 38.4 and 37.8dB in quasi-TM mode at wavelengths 1.30 and 1.55\mum, respectively, and the insertion losses below 0.2dB at both wavelengths and in both polarization states. The alternating direction implicit algorithm with the Crank--Nicholson scheme is applied to the discretization of the 3D-SV-FD-BPM formulation along the longitudinal direction. Moreover, a modified FD scheme is constructed to approximate the resulting equations along the transverse directions, in which the discontinuities of the derivatives of magnetic field components H_y and H_x along the vertical and horizontal interfaces, respectively, are involved.     

超低频率全正色散半导体可饱和吸收镜被动锁模光纤激光器

 通过延长激光器环形腔腔长,利用高浓度掺杂的单模掺镱光纤,搭建了超低重复频率、全正色散结构的半导体可饱和吸收镜被动锁模光纤激光器。激光器的中心波长、重复频率、平均功率及单脉冲能量分别为1 064 nm,281.5 kHz,11 mW和39 nJ。为了稳定中心波长,实现自启动,激光器腔体内接入了一个带通滤波器。该激光器运行稳定,无调Q不稳定现象,极大减小了半导体可饱和吸收镜被损坏的机会。