Contents
2018
Volume: 6 Issue 10
16 Article(s)

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TWO DIMENSIONAL LAYERED MATERIALS FOR ULTRAFAST LASERS (INVITATION ONLY)
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, C1 (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, C15 (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, C29 (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, C36 (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, C44 (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, C8 (2018)
Research Articles
Integrated Optics
Lasers and Laser Optics
Integration of nanoscale light emitters: an efficient ultraviolet and blue random lasing from NaYF4:Yb/Tm hexagonal nanocrystals
Ya-Pei Peng, Wei Lu, Pengpeng Ren, Yiqun Ni, Yunfeng Wang, Long Zhang, Yu-Jia Zeng, Wenfei Zhang, and Shuangchen Ruan
Near infrared light-controlled release of payloads from ultraviolet-sensitive (UV-sensitive) polymer hydrogels or nanocarriers is one of the most promising strategies for biotherapy. Here, we propose the concept of light activation of NaYF4:20%Yb,2%Tm nanocrystals (NCs). NaYF4:20%Yb,2%Tm NCs are synthesized by a solvothermal method. Effective upconversion luminescence from NaYF4:20%Yb,2%Tm NCs excited by a continuous wave (CW) 980 nm laser is obtained. The NaYF4:20%Yb,2%Tm NCs are then used as a laser gain medium and sandwiched between Al and quartz reflectors to form laser microcavities. UV and blue upconverted random lasing is obtained from the laser microcavities. Hence, we verify explicitly that the NaYF4:Yb,Tm NCs support UV and blue upconversion random lasing via a 980 nm nanosecond laser excitation. Our work provides what we believe is a new concept for precision and localized cancer therapy by external light excitation.
Photonics Research
  • Publication Date: Sep. 07, 2018
  • Vol. 6, Issue 10, 943 (2018)
Passively Q-switched femtosecond-laser-written thulium waveguide laser based on evanescent field interaction with carbon nanotubes
Esrom Kifle, Pavel Loiko, Javier Rodríguez Vázquez de Aldana, Carolina Romero, Airán Ródenas, Sun Yung Choi, Ji Eun Bae, Fabian Rotermund, Viktor Zakharov, Andrey Veniaminov, Magdalena Aguiló, Francesc Díaz, Uwe Griebner, Valentin Petrov, and Xavier Mateos
Surface channel waveguides (WGs) were fabricated in a monoclinic Tm3+:KLu(WO4)2 crystal by femtosecond direct laser writing (fs-DLW). The WGs consisted of a half-ring cladding with diameters of 50 and 60 μm located just beneath the crystal surface. They were characterized by confocal laser microscopy and μ-Raman spectroscopy, indicating a reduced crystallinity and stress-induced birefringence of the WG cladding. In continuous-wave (CW) mode, under Ti:sapphire laser pumping at 802 nm, the maximum output power reached 171.1 mW at 1847.4 nm, corresponding to a slope efficiency η of 37.8% for the 60 μm diameter WG. The WG propagation loss was 0.7±0.3 dB/cm. The top surface of the WGs was spin-coated by a polymethyl methacrylate film containing randomly oriented (spaghetti-like) arc-discharge single-walled carbon nanotubes serving as a saturable absorber based on evanescent field coupling. Stable passively Q-switched (PQS) operation was achieved. The PQS 60 μm diameter WG laser generated a record output power of 150 mW at 1846.8 nm with η=34.6%. The conversion efficiency with respect to the CW mode was 87.6%. The best pulse characteristics (energy/duration) were 105.6 nJ/98 ns at a repetition rate of 1.42 MHz.
Photonics Research
  • Publication Date: Sep. 26, 2018
  • Vol. 6, Issue 10, 971 (2018)
Materials
Anomalous transport of light at the phase transition to localization: strong dependence with incident angle
Ernesto Jimenez-Villar, M. C. S. Xavier, Niklaus U. Wetter, Valdeci Mestre, Weliton S. Martins, Gabriel F. Basso, V. A. Ermakov, F. C. Marques, and Gilberto F. de Sá
There has been a growing interest in disordered optical media in recent years due to their potential applications in solar collectors, random lasers, light confinement, and other advanced photonic functions. This paper studies the transport of light for different incidence angles in a strongly disordered optical medium composed of core-shell TiO2@Silica nanoparticles suspended in an ethanol solution. A decrease of optical conductance and an increase of absorption near the input border are reported when the incidence angle increases. The specular reflection, measured for the photons that enter the sample, is lower than the effective internal reflection undergone by the coherently backscattered photons in the exact opposite direction, indicating a nonreciprocal propagation of light. This study represents a novel approach in order to understand the complex physics involved at the phase transition to localization.
Photonics Research
  • Publication Date: Sep. 07, 2018
  • Vol. 6, Issue 10, 929 (2018)
Nonlinear Optics
Soliton regulation in microcavities induced by fundamental–second-harmonic mode coupling
Xiaoxiao Xue, Xiaoping Zheng, and Bingkun Zhou
Microcomb generation with simultaneous χ(2) and χ(3) nonlinearities brings new possibilities for ultrabroadband and potentially self-referenced integrated comb sources. However, the evolution of the intracavity field involving multiple nonlinear processes shows complex dynamics that are still poorly understood. Here, we report on strong soliton regulation induced by fundamental–second-harmonic (FD-SH) mode coupling. The formation of solitons from chaos is extensively investigated based on coupled Lugiato–Lefever equations. The soliton generation shows more deterministic behaviors in the presence of FD-SH mode interaction, which is in sharp contrast with the usual cases where the soliton number and relative locations are stochastic. Deterministic single soliton transition, soliton binding, and prohibition are observed, depending on the phase-matching condition and coupling coefficient between the fundamental and second-harmonic waves. Our finding provides important new insights into the soliton dynamics in microcavities with simultaneous χ(2) and χ(3) nonlinearities and can be immediate guidance for broadband soliton comb generation with such platforms.
Photonics Research
  • Publication Date: Sep. 10, 2018
  • Vol. 6, Issue 10, 948 (2018)
Broadband quasi-phase matching in a MgO:PPLN thin film
Licheng Ge, Yuping Chen, Haowei Jiang, Guangzhen Li, Bing Zhu, Yi’an Liu, and Xianfeng Chen
Future quantum information networks operated on telecom channels require qubit transfer between different wavelengths while preserving quantum coherence and entanglement. Qubit transfer is a nonlinear optical process, but currently the types of atoms used for quantum information processing and storage are limited by the narrow bandwidth of upconversion available. Here we present the first experimental demonstration of broadband and high-efficiency quasi-phase matching second-harmonic generation (SHG) in a chip-scale periodically poled lithium niobate thin film. We achieve a large bandwidth of up to 2 THz for SHG by satisfying quasi-phase matching and group-velocity matching simultaneously. Furthermore, by changing the film thickness, the central wavelength of the quasi-phase matching SHG bandwidth can be modulated from 2.70 μm to 1.44 μm. The reconfigurable quasi-phase matching lithium niobate thin film provides a significant on-chip integrated platform for photonics and quantum optics.
Photonics Research
  • Publication Date: Sep. 13, 2018
  • Vol. 6, Issue 10, 954 (2018)
Nonlinear distortion and spatial dispersion of intense terahertz generation in lithium niobate via the tilted pulse front technique
Baolong Zhang, Shangqing Li, Shusu Chai, Xiaojun Wu, Jinglong Ma, Liming Chen, and Yutong Li
Photonics Research
  • Publication Date: Sep. 18, 2018
  • Vol. 6, Issue 10, 959 (2018)
Plasmonics
Sequential trapping of single nanoparticles using a gold plasmonic nanohole array
Xue Han, Viet Giang Truong, Prince Sunil Thomas, and Síle Nic Chormaic
Photonics Research
  • Publication Date: Oct. 01, 2018
  • Vol. 6, Issue 10, 981 (2018)

About the Cover

Special issue on two-dimensional layered materials for ultrafast lasers.