以自激注入锁定方式生成边模抑制比高的可调谐双波长超短光脉冲

介绍一种简单的以自激注入锁定方式、生成边模抑制比改善的、可调谐双波长超短光脉冲的实验系统.系统通过调整两个B ragg光纤光栅和光延迟线,可方便地调谐两个不同波长及其间距,从而获得双波长光脉冲输出.实验显示,在20.7nm的波长调谐范围内,可获得边模抑制比接近或高于30dB的双波长光脉冲输出.系统简单,且波长调谐方便.

Observation of controllable tightly and loosely bound solitons with an all-fiber saturable absorber

A hybrid no-core fiber(NCF)–graded index multimode fiber(GIMF) structure is used as a saturable absorber(SA)for mode-locked laser operation. Such an SA supports various types of soliton outputs. By changing the cavity parameters, not only the spatiotemporal mode-locking states with a stable single pulse but also tightly and loosely bound solitons are generated. Single 35.5 pJ solitons centered at 1568.5 nm have a 4 nm spectral full-width at half-maximum and an 818 fs temporal duration. Tightly bound soliton pairs with continuously tunable wavelength from 1567.48 nm to 1576.20 nm, featured with an ~700 fs pulse train with a separation of 2.07 ps, have been observed by stretching the NCF-GIMF structured device. Meanwhile, several different pulse separations from 37.57 ps to 56.46 ps of loosely bound solitons have also been realized. The results provide help in understanding the nonlinear dynamics in fiber lasers.

Generation of wavelength-tunable and coherent dual-wavelength solitons in the C + L band by controlling the intracavity loss

A wavelength-tunable and dual-wavelength mode-locking operation is achieved in an Er-doped fiber laser using a hybrid no-core fiber graded index multimode fiber as the saturable absorber. In the tuning operation, continuously wavelength-tunable pulses with a tuning range of 46.7 nm, stable 3-dB bandwidth of around 5 nm, and pulse duration of ~850 fs are obtained by increasing the intracavity loss of a variable optical attenuator. In the dual-wavelength operation, the two solitons at different wavelengths demonstrate the characteristics of mutual coherence. By increasing the intracavity loss, the spectral spacing can be tuned from 11 to 33.01 nm while maintaining the coherence of the solitons. Such coherent solitons have high potential for applications in dual-comb frequency and multicolor pulses in nonlinear microscopy.

Graded index fiber as an all-fiber saturable absorber for large energy conventional soliton and dissipative soliton generation

In this work, we investigate the possibility of achieving nanojoule level pulse energy in an all-fiber Er-doped oscillator by using a graded index multimode fiber(GIMF) as the saturable absorber(SA). This GIMF-based SA demonstrates the desirable characteristics of high-power tolerance, large modulation depth of 29.6%, and small saturation fluence of7.19 × 10^-3μJ∕cm^2, which contribute to the high-energy soliton generation. In the experiments, the oscillator generates stable ultrafast pulse trains with high pulse energy/average output power up to 13.65 nJ/212.4 m W in the anomalous regime and 6.25 nJ/72.5 m W in the normal regime, which are among the highest energy/average output power values achieved by all-fiber Er lasers. The results obtained demonstrate that the GIMF-based SA can be used as an effective photonic device for high-energy wave-breaking free pulse generation.

Effects of spacing on dynamics of two coupled Bose-Einstein condensates in two finite traps

Interaction between two coupled Bose-Einstein condensates （BECs） is investigated by the variational approach in two finite traps, and the effects of the spacing between the two traps on dynamics of the two BECs are analyzed. The spacing determines the stable condition of stationary states, affects the existence condition of each BEC, and changes the switching and self-trapping effects on the two BECs. The dynamic mechanism is demonstrated by performing a coordinate of classical particle moving in an effective potential field, and confirmed by the evolution of the atom population transferring ratio.