• Special Issue
  • Two Dimensional Layered Materials for Ultrafast Lasers (Invitation only)
  • 8 Article (s)
Graphene-decorated microfiber knot as a broadband resonator for ultrahigh-repetition-rate pulse fiber lasers
Meng Liu, Rui Tang, Ai-Ping Luo, Wen-Cheng Xu, and Zhi-Chao Luo
Searching for an ultrahigh-repetition-rate pulse on the order of hundreds of gigahertz (GHz) is still a challenging task in the ultrafast laser community. Recently, high-quality silicon/silica-based resonators were exploited to generate a high-repetition-rate pulse based on the filter-driven four-wave mixing effect in fiber lasers. However, despite their great performance, the silicon/silica-based resonators still have some drawbacks, such as single waveband operation and low coupling efficiency between the fiber and resonators. To overcome these drawbacks, herein we proposed an all-fiber broadband resonator fabricated by depositing the graphene onto a microfiber knot. As a proof-of-concept experiment, the graphene-deposited broadband microfiber knot resonator (MKR) was applied to Er- and Yb-doped fiber lasers operating at two different wavebands, respectively, to efficiently generate hundreds-of-GHz-repetition-rate pulses. Such a graphene-deposited broadband MKR could open some new applications in ultrafast laser technology, broadband optical frequency comb generation, and other related fields of photonics.
Photonics Research
  • Publication Date: Jul. 26, 2018
  • Vol. 6, Issue 10, 100000C1 (2018)
Saturated absorption of different layered Bi2Se3 films in the resonance zone
Jun Zhang, Tian Jiang, Tong Zhou, Hao Ouyang, Chenxi Zhang, Zheng Xin, Zhenyu Wang, and Xiang’ai Cheng
Here, we used the micro P-scan method to investigate the saturated absorption (SA) of different layered Bi2Se3 continuous films. Through resonance excitation, first, we studied the influence of the second surface state (SS) on SA. The second SS resonance excitation (~2.07 eV) resulted in a free carrier cross section that was 4 orders of magnitude larger than usual. At the same time, we found that the fast relaxation process of the massless Dirac electrons is much shorter than that of electrons in bulk states. Moreover, the second SS excitation resonance reduced the saturation intensity. Second, we studied the effect of the thickness on the SA properties of materials. The results showed that the saturation intensity was positively correlated to the thickness, the same as the modulation depth, and the thicker the Bi2Se3 film was, the less the second SS would influence it. This work demonstrated that by using Bi2Se3 as a saturable absorber through changing the thickness or excitation wavelength, a controllable SA could be achieved.
Photonics Research
  • Publication Date: Aug. 02, 2018
  • Vol. 6, Issue 10, 100000C8 (2018)
Nonlinear optical properties of WSe2 and MoSe2 films and their applications in passively Q-switched erbium doped fiber lasers
Wenjun Liu, Mengli Liu, Hainian Han, Shaobo Fang, Hao Teng, Ming Lei, and Zhiyi Wei
Transition metal dichalcogenides (TMDs) are successfully applied in fiber lasers for their photoelectric properties. However, in previous work, how to improve the modulation depth of TMD-based saturable absorbers (SAs) has been a challenging issue. In this paper, WSe2 and MoSe2 SAs are fabricated with the chemical vapor deposition method. Compared with previous experiments, the modulation depths of WSe2 and MoSe2 SAs with sandwiched structures are effectively increased to 31.25% and 25.69%, respectively. The all-fiber passively Q-switched erbium doped fiber lasers based on WSe2 and MoSe2 SAs are demonstrated. The signal-to-noise ratios of those lasers are measured to be 72 and 57 dB, respectively. Results indicate that the proposed WSe2 and MoSe2 SAs are efficient photonic devices to realize stable fiber lasers.
Photonics Research
  • Publication Date: Aug. 07, 2018
  • Vol. 6, Issue 10, 10000C15 (2018)
212-kHz-linewidth, transform-limited pulses from a single-frequency Q-switched fiber laser based on a few-layer Bi2Se3 saturable absorber
Weiwei Li, Jinhai Zou, Yizhong Huang, Kaijie Wang, Tuanjie Du, Shuisen Jiang, and Zhengqian Luo
Conventional Q-switched fiber lasers operating at multi-longitudinal-mode oscillation usually suffer from self-mode-locking-induced temporal instability, relatively strong noise, and low coherence. Here, we address the challenge through demonstrating, for the first time, to the best of our knowledge, a single-longitudinal-mode (SLM) Er-doped fiber (EDF) laser passively Q-switched by a few-layer Bi2Se3 saturable absorber (SA). The Bi2Se3 SA prepared by the liquid-phase exfoliation method shows a modulation depth of ~5% and saturation optical intensity of 1.8 MW/cm2. A section of 1-m unpumped EDF together with a 0.06-nm-bandwidth fiber Bragg grating is used as an ultra-narrow autotracking filter to realize SLM oscillation. Stable SLM Q-switching operation at 1.55 μm is successfully achieved with the spectral linewidth as narrow as 212 kHz and the pulse duration of 2.54 μs, manifesting near-transform-limited pulses with a time-bandwidth product of 0.53. In particular, we found that the SLM Q-switching possesses the higher signal-to-noise ratios of 62 dB (optical) and 48 dB (radio frequency), exhibiting its advantages of low noise and high stability. Such an SLM Q-switched fiber laser could gain great interest for some applications in coherent detection, coherent optical communications, and high-sensitivity optical sensing.
Photonics Research
  • Publication Date: Aug. 27, 2018
  • Vol. 6, Issue 10, 10000C29 (2018)
Femtosecond mode-locking of a fiber laser using a CoSb3-skutterudite-based saturable absorber
Jinho Lee, Yoontaek Kim, Kyungtaek Lee, and Ju Han Lee
We experimentally demonstrate an ultrafast mode-locker based on a CoSb3 skutterudite topological insulator for femtosecond mode-locking of a fiber laser. The mode-locker was implemented on a side-polished fiber platform by depositing a CoSb3/PVA composite. The measured modulation depth and saturation power for the transverse-electric mode input were ~5% and ~8.7 W, respectively, and ~2.8% and ~10.6 W for the transverse-magnetic mode input. By incorporating this mode-locker into an erbium-doped fiber-based ring cavity, we were able to readily generate mode-locked, soliton pulses having a pulse width of ~833 fs at 1557.9 nm. The 3-dB bandwidth of the output pulses and time-bandwidth product were ~3.44 and 0.353 nm, respectively. To the best of the authors’ knowledge, this is the first demonstration of the use of a skutterudite-based saturable absorber for femtosecond mode-locked pulse generation.
Photonics Research
  • Publication Date: Sep. 10, 2018
  • Vol. 6, Issue 10, 10000C36 (2018)
TiS2-based saturable absorber for ultrafast fiber lasers
X. Zhu, S. Chen, M. Zhang, L. Chen, Q. Wu, J. Zhao, Q. Jiang, Z. Zheng, and H. Zhang
Photonics Research
  • Publication Date: Sep. 26, 2018
  • Vol. 6, Issue 10, 10000C44 (2018)

The emergence of graphene saturable absorbers towards the generation of ultra-short pulses in mode-locked lasers have significantly attracted world-wide attention in the related fields. Graphene-based saturable absorbers have been verified to possess unique properties, such as broad operation bandwidth, ultrafast response time, relatively high modulation depth and low saturation intensity. Inspired by the great success of graphene, graphene-like two-dimensional (2D) layered materials have also been demonstrated for ultrafast pulse generation with distinctive advantages of tunable bandgap, low optical losses, high optical nonlinearities. This feature issue is aimed at scientists, engineers and practitioners interested in understanding the novel nonlinear optical properties of 2D materials and exploring their potential applications in mode locked lasers.