Contents
2018
Volume: 16 Issue 2
20 Article(s)

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PHOTONICS BASED ON 2D NONCARBON MATERIALS
Highly responsive broadband black phosphorus photodetectors
Yan Liu, Tian Sun, Weiliang Ma, Wenzhi Yu, Shivananju B. Nanjunda, Shaojuan Li, and Qiaoliang Bao
Black phosphorus (BP) is a promising material for ultrafast and broadband photodetection because of its narrow bandgap from 0.35 eV (bulk) to 1.8 eV (monolayer) and high carrier mobility. Although photodetectors based on BP with different configurations have been reported, high photosensitivity was mostly observed in the visible range. A highly efficient BP-based infrared photodetector operated in the telecom spectral range, especially at 1550 nm, has not been demonstrated. Here, we report a Schottky-type photodetector based on thin BP flakes, operating in a broad spectral range from visible (635 nm) to infrared (1550 nm). A responsivity as high as 230 A·W 1 was achieved at 1550 nm with a source-drain bias of 1 V. The rise time is 4.8 ms, and the fall time is 6.8 ms. Under light illumination and external bias, the Schottky barrier between the BP and metal was reduced, leading to efficient photocurrent extraction. The unprecedented performance of the BP photodetector indicates intriguing potential for sensing, imaging, and optical communication.
Chinese Optics Letters
  • Publication Date: Feb. 10, 2018
  • Vol. 16, Issue 2, 020002 (2018)
2D noncarbon materials-based nonlinear optical devices for ultrafast photonics [Invited]
Bo Guo
Ultrafast lasers play an important role in a variety of applications ranging from optical communications to medical diagnostics and industrial materials processing. Graphene and other two-dimensional (2D) noncarbon materials, including topological insulators (TIs), transition metal dichalcogenides (TMDCs), phosphorene, bismuthene, and antimonene, have witnessed a very fast development of both fundamental and practical aspects in ultrafast photonics since 2009. Their unique nonlinear optical properties enable them to be used as excellent saturable absorbers (SAs) that have fast responses and broadband operation, and can be easily integrated into lasers. Here, we catalog and review recent progress in the exploitation of these 2D noncarbon materials in this emerging field. The fabrication techniques, nonlinear optical properties, and device integration strategies of 2D noncarbon materials are first introduced with a comprehensive view. Then, various mode-locked/Q-switched lasers (e.g., fiber, solid-state, disk, and waveguide lasers) based on 2D noncarbon materials are reviewed. In addition, versatile soliton pulses generated from the mode-locked fiber lasers based on 2D noncarbon materials are also summarized. Finally, future challenges and perspectives of 2D materials-based lasers are addressed.
Chinese Optics Letters
  • Publication Date: Feb. 10, 2018
  • Vol. 16, Issue 2, 020004 (2018)
Passively Q-switched green laser operation using CdTe/CdS quantum dots (Invited Paper)
Xigun Yan, Saiyu Luo, Bin Xu, Huiying Xu, Zhiping Cai, Jingzhou Li, Hongxing Dong, Long Zhang, and Zhengqian Luo
Chinese Optics Letters
  • Publication Date: Feb. 10, 2018
  • Vol. 16, Issue 2, 020005 (2018)
Layer-number determination of two-dimensional materials by optical characterization
You Zheng, Changyong Lan, Zhifei Zhou, Xiaoying Hu, Tianying He, and Chun Li
Initiated by graphene, two-dimensional (2D) layered materials have attracted much attention owing to their novel layer-number-dependent physical and chemical properties. To fully utilize those properties, a fast and accurate determination of their layer number is the priority. Compared with conventional structural characterization tools, including atomic force microscopy, scanning electron microscopy, and transmission electron microscopy, the optical characterization methods such as optical contrast, Raman spectroscopy, photoluminescence, multiphoton imaging, and hyperspectral imaging have the distinctive advantages of a high-throughput and nondestructive examination. Here, taking the most studied 2D materials like graphene, MoS2, and black phosphorus as examples, we summarize the principles and applications of those optical characterization methods. The comparison of those methods may help us to select proper ones in a cost-effective way.
Chinese Optics Letters
  • Publication Date: Feb. 10, 2018
  • Vol. 16, Issue 2, 020006 (2018)
High-power MoTe2-based passively Q-switched erbium-doped fiber laser
Mengli Liu, Wenjun Liu, Peiguang Yan, Shaobo Fang, Hao Teng, and Zhiyi Wei
Materials in the transition metal dichalcogenide family, including WS2, MoS2, WSe2, and MoSe2, etc., have captured a substantial amount of attention due to their remarkable nonlinearities and optoelectronic properties. Compared with WS2 and MoS2, the monolayered MoTe2 owns a smaller direct bandgap of 1.1 eV. It is beneficial for the applications in broadband absorption. In this letter, using the magnetron sputtering technique, MoTe2 is deposited on the surface of the tapered fiber to be assembled into the saturable absorber. We first implement the MoTe2-based Q-switched fiber laser operating at the wavelength of 1559 nm. The minimum pulse duration and signal-to-noise ratio are 677 ns and 63 dB, respectively. Moreover, the output power of 25 mW is impressive compared with previous work. We believe that MoTe2 is a promising 2D material for ultrafast photonic devices in the high-power Q-switched fiber lasers.
Chinese Optics Letters
  • Publication Date: Feb. 10, 2018
  • Vol. 16, Issue 2, 020007 (2018)
Coexistence of bound soliton and harmonic mode-locking soliton in an ultrafast fiber laser based on MoS2-deposited microfiber photonic device
Meng Liu, Aiping Luo, Wencheng Xu, and Zhichao Luo
As the typical material of two-dimensional transition metal dichalcogenides (TMDs), few-layered MoS2 possesses broadband saturable absorption and a large nonlinear refractive index, which could be regarded as a promising candidate for dual-function photonic device fabrication. In this work, the coexistence of a bound soliton and harmonic mode-locking soliton was demonstrated in an ultrafast fiber laser based on a MoS2-deposited microfiber photonic device. Through a band-pass filter, each multi-soliton state was investigated separately. The bound soliton has periodic spectral modulation of 1.55 nm with a corresponding pulse separation of 5.16 ps. The harmonic mode-locking soliton has the repetition rate of 479 MHz, corresponding to the 65th harmonic of the fundamental repetition rate. The results indicated that there exist more possibilities of different multi-soliton composites, which would enhance our understanding of multi-soliton dynamics.
Chinese Optics Letters
  • Publication Date: Feb. 10, 2018
  • Vol. 16, Issue 2, 020008 (2018)
Passive Q-switching in an erbium-doped fiber laser using tungsten sulphoselenide as a saturable absorber
H. Ahmad, Z. C. Tiu, and S. I. Ooi
A highly stable Q-switched laser incorporating a mechanically exfoliated tungsten sulphoselenide (WSSe) thin sheet saturable absorber (SA) is proposed and demonstrated. The SA assembly, formed by sandwiching a thin WSSe sheet between two fiber ferrules within the erbium-doped fiber laser, is used to effectively modulate the laser cavity losses. The WSSe-based SA has a saturation intensity of ~0.006 MW/cm2 and a modulation depth of 7.8%, giving an optimum Q-switched laser output with a maximum repetition rate of 61.81 kHz and a minimum pulse width of 2.6 μs. The laser’s highest output power of 0.45 mW and highest pulse energy of 7.31 nJ are achieved at the maximum pump power of 280.5 mW. The tunability of the cavity’s output at the maximum pump power is analyzed with a C-band tunable bandpass filter, giving a broad tunable range of ~40 nm, from 1530 nm to 1570 nm. The output performance of the tunable Q-switched laser correlates well with the gain spectrum of erbium-doped fibers, with the shift in the gain profile as a result of the saturated SA.
Chinese Optics Letters
  • Publication Date: Feb. 10, 2018
  • Vol. 16, Issue 2, 020009 (2018)
High-power all-fiber 1.0/1.5 μm dual-band pulsed MOPA source
Xiaogang Ge, Jun Yu, Weiqi Liu, Shuangchen Ruan, Chunyu Guo, Yewang Chen, Peiguang Yan, and Ping Hua
The simultaneous dual-band pulsed amplification is demonstrated from an Er/Yb co-doped fiber (EYDF), and consequently a high-power all-fiber single-mode 1.0/1.5 μm dual-band pulsed master oscillator power amplifier (MOPA) laser source is realized for the first time, to the best of our knowledge, based on one singlegain fiber. The simultaneous outputs at 1061 and 1548 nm of the laser source have the maximum powers of 10.7 and 25.8 W with the pulse widths of 9.5 ps and 2 ns and the pulse repetition rates of 178 and 25 MHz, respectively. This EYDF MOPA laser source is seeded by two separate preamplifier chains operating at 1.0 and 1.5 μm wavebands. The dependence of the laser output powers on the length of the large-mode area EYDF, the ratio of the powers of the two signals launched into the booster amplifier, and the wavelength of the 1 μm seed signal are also investigated experimentally.
Chinese Optics Letters
  • Publication Date: Feb. 10, 2018
  • Vol. 16, Issue 2, 020010 (2018)
Graphene/MoS2 heterostructure: a robust mid-infrared optical modulator for Er3+-doped ZBLAN fiber laser
Pinghua Tang, Yue Tao, Yuliang Mao, Man Wu, Zongyu Huang, Shengnan Liang, Xinhang Chen, Xiang Qi, Bin Huang, Jun Liu, and Chujun Zhao
Chinese Optics Letters
  • Publication Date: Feb. 10, 2018
  • Vol. 16, Issue 2, 020012 (2018)
Dual-wavelength Bi2Se3-based passively Q-switching Nd3+-doped glass all-fiber laser
Xiaofeng Rong, Saiyu Luo, Wensong Li, Shuisen Jiang, Xigun Yan, Xiaofeng Guan, Zhiyong Zhou, Bin Xu, Nan Chen, Degui Wang, Huiying Xu, and Zhiping Cai
Chinese Optics Letters
  • Publication Date: Feb. 10, 2018
  • Vol. 16, Issue 2, 020016 (2018)
Passively Q-switched ytterbium-doped fiber laser using the evanescent field interaction with bulk-like WTe2 particles
Seunghwan Ko, Jinho Lee, and Ju Han Lee
The potential of bulk-like WTe2 particles for the realization of a passive Q-switch operating at the 1 μm wavelength was investigated. The WTe2 particles were prepared using a simple mechanical exfoliation method together with Scotch tape. By attaching bulk-like WTe2 particles, which remained on the top of the sticky surface of a small segment of the Scotch tape, to the flat side of a side-polished fiber, a saturable absorber (SA) was readily implemented. A strong saturable absorption was then readily obtained through an evanescent field interaction with the WTe2 particles. The modulation depth of the prepared SA was measured as ~2.18% at 1.03 μm. By incorporating the proposed SA into an all-fiberized ytterbium-doped fiber ring cavity, stable Q-switched pulses were readily achieved.
Chinese Optics Letters
  • Publication Date: Feb. 10, 2018
  • Vol. 16, Issue 2, 020017 (2018)
Enhanced saturable absorption of MoS2 black phosphorus composite in 2 μm passively Q-switched Tm: YAP laser
Yang Xue, Zhenda Xie, Zhilin Ye, Xiaopeng Hu, Jinlong Xu, and Han Zhang
Chinese Optics Letters
  • Publication Date: Feb. 10, 2018
  • Vol. 16, Issue 2, 020018 (2018)
2  μm mode-locking laser performances of sol-gel-fabricated large-core Tm-doped silica fiber
Yan Ren, Zhipeng Qin, Guoqiang Xie, Zhen Qiao, Ting Hai, Peng Yuan, Jingui Ma, Liejia Qian, Shikai Wang, Chunlei Yu, and Lili Hu
High-power ultrafast fiber lasers operating at the 2 μm wavelength are extremely desirable for material processing, laser surgery, and nonlinear optics. Here we fabricated large-core (LC) double-cladding Tm-doped silica fiber via the sol-gel method. The sol-gel-fabricated Tm-doped silica (SGTS) fiber had a large core diameter of 30 μm with a high refractive index homogeneity (Δn=2×10 4). With the newly developed LC SGTS fiber as the gain fiber, high-power mode-locking was realized. By using a semiconductor saturable absorber mirror (SESAM) as a mode locker, the LC SGTS fiber oscillator generated mode-locked pulses with an average output power as high as 1.0 W and a pulse duration of 23.9 ps at the wavelength of 1955.0 nm. Our research results show that the self-developed LC Tm-doped silica fiber via the sol-gel method is a promising gain fiber for generating high-power ultrafast lasers in the 2 μm spectral region.
Chinese Optics Letters
  • Publication Date: Feb. 10, 2018
  • Vol. 16, Issue 2, 020020 (2018)

About the Cover

Special issue on photonics based on two-dimensional noncarbon materials.