Xintong Xu

Passively Q-switching induced by the smallest single-walled carbon nanotubes

We report a passively Q-switched erbium-doped fiber laser (EDFL) by using the smallest single-walled carbon nanotubes (SWNTs) with a diameter of 0.3u2009nm as the saturable absorber. These small SWNTs are fabricated in the nanochannels of a ZnAPO-11 (AEL) single crystal. By inserting one of the AEL crystal into an EDFL cavity pumped by a 980u2009nm laser diode, stable passive Q-switching is achieved for a threshold pump power of 206.2 mW, and 4.73u2009μs pulses with a repetition rate of 41.78u2009kHz and an average output power of 3.75 mW are obtained for a pump power of 406 mW.

A Thresholdless Tunable Raman Nanolaser using a ZnO–Graphene Superlattice

A ZnO-graphene superlattice is synthesised via a spatially confined reaction. When illuminated by a pump laser, the Stokes photons of the superlattice are greatly amplified by the surface plasmon at the interface of the graphene and the ZnO. Benefitting from the special geometry, the ZnO-graphene superlattice allows the generation of a tunable nanolaser that operates from the visible to near-infrared range at room temperature.

Passively mode-locking erbium-doped fiber lasers with 0.3 nm single-walled carbon nanotubes.

We demonstrate a passively mode-locked erbium-doped fiber laser (EDFL) by using the smallest single-walled carbon nanotubes (SWNTs) with a diameter of 0.3u2005nm as the saturable absorber. These ultrasmall SWNTs are fabricated in the elliptical nanochannels of a ZnAPO4-11 (AEL) single crystal. By placing an AEL crystal into an EDFL cavity pumped by a 980u2005nm laser diode, stable passive mode-locking is achieved for a threshold pump power of 280u2005mW, and 73u2005ps pulses at 1563.2u2005nm with a repetition rate of 26.79u2005MHz.

Synthesis of large MgAPO-11 single crystals in a F− free system

The synthesis process of large magnesium substituted AlPO4-11 single crystals (MgAPO-11) under hydrothermal conditions has been reported. The crystal size and morphology sensitively depend on crystallization conditions and gel compositions. The addition of HF acid in the gel undermines rather than favours the growth of MgAPO-11 single crystals. Using the optimal gel composition with magnesium oxide as the magnesium source, large MgAPO-11 single crystals with good quality have been synthesized in a F− free system. The typical crystal dimensions are 25 × 157 ×254 μm3, the synthesis temperature is 180 °C, and the crystallization period is 60 hours.

Facile active control of a pulsed erbium-doped fiber laser using modulation depth tunable carbon nanotubes

Short pulsed fiber lasers have been widely made using single-walled carbon nanotubes as a saturable absorber (SA). However, most of the currently used devices can only operate in one determined operation state with an unchangeable modulation SA depth in the cavity, which significantly limits their application in photonic devices. In this paper, well-aligned carbon nanotube arrays are synthesized using zeolite AlPO4-5 as a template, which features anisotropic optical absorption. The linear optical absorption of the as-synthesized carbon nanotube arrays can easily be tuned by adjusting a polarization controller, thus providing a tunable modulation depth for the carbon nanotube SA. By exploiting this SA in an erbium-doped fiber laser cavity, both Q-switched and mode-locked pulsed lasers are achieved by simply adjusting a polarization controller under a fixed pump power of 330xa0mW. In addition, the repetition rate of the Q-switching and pulse duration of the mode-locking can be tuned according to the variation of modulation depth. Moreover, soliton molecules can be obtained when the modulation depth of the SA is 4.5%.

Facile synthesis of graphene nanoribbons from zeolite-templated ultra-small carbon nanotubes for lithium ion storage

One-dimensional graphene nanoribbons are attracting considerable attention due to their extraordinary electronic, magnetic, and optical properties, and have a wide range of applications, but have not attained full success owing to the lack of simple and efficient synthetic strategies. Here, we present a facile strategy for the synthesis of graphene nanoribbons by unraveling ultra-small carbon nanotubes. The armchair (2,2) carbon nanotubes with a theoretical diameter of 0.28 nm fabricated in the nanochannels of zeolite ZnAPO4-11 (AEL) can be transformed into graphene nanoribbons by removing the AEL template through chemical treatment. The as-synthesized graphene nanoribbons are N-doped with a thickness of two- to seven-layers, have a width of 10–30 nm and length of >1 μm, and show high performance as an anode material for lithium ion batteries. Moreover, this strategy can be readily scaled up for practical applications requiring bulk quantities of graphene nanoribbons.

Host-guest interaction between Acridine orange molecules and AFI or CHA zeolite crystals

Acridine orange (AO) molecules were incorporated in AlPO4-5, SAPO-5 and SAPO-47 single crystals by vapor-phase diffusion method. Polarized absorption spectra show that AO molecules are well aligned by the one-dimensional channel systems of AlPO4-5 and SAPO-5 matrices. While the orientation of AO molecules in SAPO-47 crystals is diverse owing to the three-dimensional cage structure of chabazite (structure code CHA). The absorption peak and emission peak of AO/SAPO-5 blue shift compared with that of AO/AlPO4-5 because the channel environment changes from non-polar medium to polar medium when Si substituted in the framework of AlPO4-5. The greater blue shift in absorption band and emission band of AO/SAPO-47 are expected to originate from the polar channel medium and smaller channel size of SAPO-47.