We demonstrate an electric-controlled terahertz（THz） modulator which can be used to realize amplitude modulation of terahertz waves with slight photo-doping. The THz pulse transmission was efficiently modulated by e...We demonstrate an electric-controlled terahertz（THz） modulator which can be used to realize amplitude modulation of terahertz waves with slight photo-doping. The THz pulse transmission was efficiently modulated by electrically controlling the monolayer silicon-based device. The modulation depth reached 100% almost when the applied voltage was 7V at an external laser intensity of 0.6W/cm2. The saturation voltage reduced with the increase of the photo-excited intensity. In a THz continuous wave（CW）system, a significant fall in both THz transmission and reflection was also observed with the increase of applied voltage. This reduction in the THz transmission and reflection was induced by the absorption for electron injection. The results show that a high-efficiency and high modulation depth broadband electric-controlled terahertz modulator in a pure Si structure has been realized.展开更多
Remarkable room-temperature ferromagnetism was observed both in undoped and Cu-doped rutile TiO2 single crystals（SCs）.To tune their magnetism,Ar ion irradiation was quantitatively performed on the two crystals in wh...Remarkable room-temperature ferromagnetism was observed both in undoped and Cu-doped rutile TiO2 single crystals（SCs）.To tune their magnetism,Ar ion irradiation was quantitatively performed on the two crystals in which the saturation magnetizations for the samples were enhanced distinctively.The post-irradiation led to a spongelike layer in the near surface of the Cu-doped TiO2.Meanwhile,a new CuO-like species present in the sample was found to be dissolved after the post-irradiation.Analyzing the magnetization data unambiguously reveals that the experimentally observed ferromagnetism is related to the intrinsic defects rather than the exotic Cu ions,while these ions are directly involved in boosting the absorption in the visible region.展开更多
The rare earth-doped active fibers not only have ten thousands of square-micron core-area but also deliver a laser with near-diffraction-limited beam quality. However, they have been studied little. In this paper, we ...The rare earth-doped active fibers not only have ten thousands of square-micron core-area but also deliver a laser with near-diffraction-limited beam quality. However, they have been studied little. In this paper, we design a 200-μm-corediameter Yb^3＋-doped photonic crystal fiber with a large pitch in the air-hole cladding region. Simulations demonstrate that only fundamental mode（FM） with a mode field area（MFA） of ～ 28000 μm^2 can be amplified and propagated at the gain saturation, and the beam quality M^2 is about 1.5. It is predicted that almost 105 m J single-pulse energy is available from such a 1.5-meter-length fiber.展开更多
A Q-switched ytterbium-doped fiber laser （YDFL） is proposed and demonstrated using a newly developed multi-walled carbon nanotubes polyethylene oxide （MWCNTs-PEO） film as a passive saturable absorber （SA）. The s...A Q-switched ytterbium-doped fiber laser （YDFL） is proposed and demonstrated using a newly developed multi-walled carbon nanotubes polyethylene oxide （MWCNTs-PEO） film as a passive saturable absorber （SA）. The saturable absorber is prepared by mixing the MWCNTs homogeneous solution into a dilute PEO polymer solution before it is left to dry at room temperature to produce thin film. Then the film is sandwiched between two FC/PC fiber connectors and integrated into the laser cavity for Q-switching pulse generation. The laser generates a stable pulse operating at wavelength of 1060.2 nm with a threshold pump power of 53.43 mW. The YDFL generates a stable pulse train with repetition rates ranging from 7.92 to 24.27 kHz by varying 980-nm pump power from 53.42 to 65.72 mW. At 59.55-mW pump power, the lowest pulse width and the highest pulse energy are obtained at 12.18 μs and 143.5 n J, respectively.展开更多
基金supported by the Natural Science Foundation of Beijing under Grant No.4144069the Science and Technology Project of Beijing Municipal Education Commission under Grant No.KM201410028004
文摘We demonstrate an electric-controlled terahertz（THz） modulator which can be used to realize amplitude modulation of terahertz waves with slight photo-doping. The THz pulse transmission was efficiently modulated by electrically controlling the monolayer silicon-based device. The modulation depth reached 100% almost when the applied voltage was 7V at an external laser intensity of 0.6W/cm2. The saturation voltage reduced with the increase of the photo-excited intensity. In a THz continuous wave（CW）system, a significant fall in both THz transmission and reflection was also observed with the increase of applied voltage. This reduction in the THz transmission and reflection was induced by the absorption for electron injection. The results show that a high-efficiency and high modulation depth broadband electric-controlled terahertz modulator in a pure Si structure has been realized.
基金Project supported by the National Natural Science Foundation of China(Grant No.11575074)the Open Project of State Key laboratory of Crystal Material,Shandong University,China(Grant No.KF1311)+2 种基金the Open Project of Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education,Lanzhou University,China(Grant No.LZUMMM2012003)the Open Project of Key Laboratory of Beam Technology and Material Modification of Ministry of Education,Beijing Normal University,China(Grant No.201204)the Fundamental Research Funds for the Central Universities,China(Grant No.lzujbky-2015-240)
文摘Remarkable room-temperature ferromagnetism was observed both in undoped and Cu-doped rutile TiO2 single crystals（SCs）.To tune their magnetism,Ar ion irradiation was quantitatively performed on the two crystals in which the saturation magnetizations for the samples were enhanced distinctively.The post-irradiation led to a spongelike layer in the near surface of the Cu-doped TiO2.Meanwhile,a new CuO-like species present in the sample was found to be dissolved after the post-irradiation.Analyzing the magnetization data unambiguously reveals that the experimentally observed ferromagnetism is related to the intrinsic defects rather than the exotic Cu ions,while these ions are directly involved in boosting the absorption in the visible region.
基金Project supported by the Program for Changjiang Scholars and Innovative Research Team in University,China(Grant No.PCSIRT:1212)the Key Grant Science and Technology Planning Project of Beijing,China(Grant Nos.PXM2013 014224 000077 and PXM2012 014224 000019)the Science and Technology Planning Project of Beijing Municipal Commission of Education,China(Grant No.KM201611232008)
文摘The rare earth-doped active fibers not only have ten thousands of square-micron core-area but also deliver a laser with near-diffraction-limited beam quality. However, they have been studied little. In this paper, we design a 200-μm-corediameter Yb^3＋-doped photonic crystal fiber with a large pitch in the air-hole cladding region. Simulations demonstrate that only fundamental mode（FM） with a mode field area（MFA） of ～ 28000 μm^2 can be amplified and propagated at the gain saturation, and the beam quality M^2 is about 1.5. It is predicted that almost 105 m J single-pulse energy is available from such a 1.5-meter-length fiber.
基金supported by Ministry of Higher Education under ERGS Grant scheme No.ER012-2012A
文摘A Q-switched ytterbium-doped fiber laser （YDFL） is proposed and demonstrated using a newly developed multi-walled carbon nanotubes polyethylene oxide （MWCNTs-PEO） film as a passive saturable absorber （SA）. The saturable absorber is prepared by mixing the MWCNTs homogeneous solution into a dilute PEO polymer solution before it is left to dry at room temperature to produce thin film. Then the film is sandwiched between two FC/PC fiber connectors and integrated into the laser cavity for Q-switching pulse generation. The laser generates a stable pulse operating at wavelength of 1060.2 nm with a threshold pump power of 53.43 mW. The YDFL generates a stable pulse train with repetition rates ranging from 7.92 to 24.27 kHz by varying 980-nm pump power from 53.42 to 65.72 mW. At 59.55-mW pump power, the lowest pulse width and the highest pulse energy are obtained at 12.18 μs and 143.5 n J, respectively.
