2012

• Record 325 of
  
  Title:Multiple operating modes in Ti:sapphire laser
  
  Author(s):Zhu, Changjun(1); He, Junfang(2); Zhai, Xuejun(1); Xue, Bing(1)
  Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering  Volume: 41  Issue: 10  DOI:   Published: October 2012  
  Abstract:Tunable continuous output mode, independent self mode-locking mode, cross mode-locking mode and multi-pulse operating mode were achieved in a two-beam pumped Ti:sapphire laser. Gain competition between the two laser cavities for the tunable continuous output was analyzed. Group velocity dispersion, self-phase modulation, cross-phase modulation and self-amplitude modulation in the two laser cavities were studied. The results show that, in the tunable continuous output mode, the outputs from the two laser cavities are mainly determined by the pump laser power; in the independent self mode-locking mode, the stability of self mode-locking is governed largely by the group velocity dispersion and self-phase modulation; in the cross mode-locking mode, cross-phase modulation is the key factor influencing the synchronization between fs and ps pulses; in the multi-pulse operating mode, the fs pulse remains a single pulse, while the ps pulse splits into three sub-pulses.
  Accession Number: 20125015795962
• Record 326 of
  
  Title:Investigation of quantum beatings at 608 cm-1 and 70 cm -1 in Rb vapor
  
  Author(s):Zhu, Changjun(1); He, Junfang(2); Zhai, Xuejun(1); Xue, Bing(1); Zhang, Chonghui(1)
  Source: Solid State Phenomena  Volume: 181-182  Issue:   DOI: 10.4028/www.scientific.net/SSP.181-182.413  Published: 2012  
  Abstract:Two coupled axially phase-matched parametric four-wave mixings have been achieved in Rb vapor by using broad bandwidth laser pulses. Coherent radiations at 420 nm produced by difference-frequency optical wave mixing processes were detected and a pump-probe scheme was employed to record time varying characteristics of the parametric four-wave mixing signals. Quantum beatings at 608 cm-1 and 70 cm-1 were retrieved from the time varying signals by Fourier transform. Moreover, time dependent Fourier transform was utilized to analyze the dynamics of quantum beatings. The results indicate that two wave packets associated with the two quantum beating frequency components interact strongly and the quantum beating dynamics can be controlled by adjusting Rb number density. © (2012) Trans Tech Publications, Switzerland.
  Accession Number: 20114814572142
• Record 327 of
  
  Title:Application of terahertz spectroscopy and molecular modeling in isomers investigation: Glucose and fructose
  
  Author(s):Zheng, Zhuan-Ping(1); Fan, Wen-Hui(1); Liang, Yu-Qing(1); Yan, Hui(1)
  Source: Optics Communications  Volume: 285  Issue: 7  DOI: 10.1016/j.optcom.2011.12.016  Published: April 1, 2012  
  Abstract:Terahertz spectra of glucose and fructose have been measured by terahertz time-domain spectroscopy (THz-TDS) at room temperature. Because they have the same molecular formula, the differences of the THz spectra can be attributed to their molecular structures and the arrangement of molecules in unit cell. In this paper, gaseous-state theory has been employed to simulate the isolated molecule of these two isomers. The results indicate that experimental THz spectral features (0.5 - 4.0 THz) of glucose and fructose arise from the mixture of intramolecular and intermolecular modes, involving hydrogen bonds and covalent bonds, and with the intermolecular modes dominating. © 2011 Elsevier B.V. All rights reserved.
  Accession Number: 20120514725869
• Record 328 of
  
  Title:Switchable mode-locking fiber laser with fiber Bragg gratings
  
  Author(s):Han, Dongdong(1)
  Source: Optical Engineering  Volume: 51  Issue: 11  DOI: 10.1117/1.OE.51.11.114202  Published: November 2012  
  Abstract:A switchable mode-locking fiber laser is proposed by means of fiber Bragg grating (FBG). The FBG plays two key roles, the switchable wavelength operation and the spectral filtering effect, on the proposed laser. The switchable single-wavelength mode-locking operation, lasing at either 1545.25 or 1548.34 nm, corresponding to the central wavelengths of the FBGs, is obtained by appropriately rotating the polarization controllers (PC). In addition, the dual-wavelength mode-locking operation is observed with proper PC state. The switchable mode-locking operation attributes to the wavelength-dependent loss mechanism and the spectral filter formed by PCs and FBGs. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE).
  Accession Number: 20135217143022
• Record 329 of
  
  Title:Dispersionless slow light in MIM waveguide based on a plasmonic analogue of electromagnetically induced transparency
  
  Author(s):Wang, Guoxi(1); Lu, Hua(1); Liu, Xueming(1)
  Source: Optics Express  Volume: 20  Issue: 19  DOI: 10.1364/OE.20.020902  Published: September 10, 2012  
  Abstract:We have proposed a metal-insulator-metal (MIM) waveguide system, which exhibits a significant slow-light effect, based on a plasmonic analogue of electromagnetically induced transparency (EIT). By appropriately adjusting the distance between the two stubs of a unit cell, a flat band corresponding to nearly constant group index over a broad bandwidth of 8.6 THz can be achieved. The analytical results show that the group velocity dispersion (GVD) parameter can reach zero and normalized delay-bandwidth product (NDBP) is more than 0.522. Finite-Difference Time-Domain (FDTD) simulations show that the incident pulse can be slowed down without distortion owing to the low dispersion. The proposed compact configuration can avoid the distortion of signal pulse, and thus may find potential applications in plasmonic slow-light systems, especially optical buffers. © 2012 Optical Society of America.
  Accession Number: 20123815452271
• Record 330 of
  
  Title:Formation and evolution of passively mode-locked fiber soliton lasers operating in a dual-wavelength regime
  
  Author(s):Mao, Dong(1); Lu, Hua(1)
  Source: Journal of the Optical Society of America B: Optical Physics  Volume: 29  Issue: 10  DOI: 10.1364/JOSAB.29.002819  Published: October 1, 2012  
  Abstract:The formation and evolution of dual-wavelength solitons in passively mode-locked fiber soliton lasers are investigated both numerically and experimentally. By solving the Ginzburg-Landau equation and taking the gain profile into account, mode-locked soliton emissions at 1532 and 1555 nm are achieved simultaneously. Numerical results show that the two solitons exhibit the same intensity and duration, indicating that the dual-wavelength pulses possess the soliton energy quantization effect. In the process of pulse-pulse collisions, two solitons pass through each other and maintain their properties, qualitatively distinct from single-wavelength solitons that never overlap each other. The dual-wavelength mode-locked operation evolves into single-wavelength mode locking with the decrease of the pumping strength. The dual-peak gain spectrum of erbium-doped fiber and the birefringence-induced cavity filtering effect play crucial roles in the formation of dual-wavelength solitons. Numerical results agree well with analytical solutions and experimental observations. Our study provides an optional method of measuring the fiber dispersion by means of the dual-wavelength solitons. © 2012 Optical Society of America.
  Accession Number: 20124315591219
• Record 331 of
  
  Title:Plasmonic analog of electromagnetically induced transparency in multi-nanoresonator-coupled waveguide systems
  
  Author(s):Lu, Hua(1); Liu, Xueming(1); Mao, Dong(1)
  Source: Physical Review A - Atomic, Molecular, and Optical Physics  Volume: 85  Issue: 5  DOI: 10.1103/PhysRevA.85.053803  Published: May 4, 2012  
  Abstract:We have theoretically and numerically investigated an analog of electromagnetically induced transparency (EIT) in plasmonic systems consisting of multiple cascaded nanodisk resonators, aperture-side-coupled to metal-insulator-metal bus waveguides. A simplified theoretical model is established to study spectral features in the plasmonic waveguide-resonator systems, and the calculated results are in good agreement with finite-difference time-domain simulations. The main dependent factors of EIT-like spectral response, namely, the resonance detuning, intrinsic Drude loss, and especially cavity-cavity separation, are discussed in detail. Similar to multiple EIT in quantum systems, multiple induced-transparency peaks are found in the areas of strong dispersion generated in our plasmonic system. The group indices and quality factors of transparency resonances with high transmission can reach levels of ∼35 and ∼200, respectively. These results pave a way toward dynamic control of light in the nanoscale domain, which can actualize some new devices for fundamental study and applications of plasmonic nanostructures. © 2012 American Physical Society.
  Accession Number: 20121915012796
• Record 332 of
  
  Title:Phase contrast microscopy with fringe contrast adjustable by using grating-based phase-shifter
  
  Author(s):Zheng, Juanjuan(1); Yao, Baoli(1); Gao, Peng(1); Ye, Tong(1)
  Source: Optics Express  Volume: 20  Issue: 14  DOI: 10.1364/OE.20.016077  Published: July 2, 2012  
  Abstract:Abstract: In this paper a new phase contrast method with fringe contrast adjustable is proposed. In the Fourier plane of the object wave, two Ronchi gratings i.e., a central grating and a surrounding grating, are used to modulate the phases of the undiffracted and diffracted components, respectively. By loading the two gratings separately on spatial light modulator, the undiffracted and diffracted components can be measured independently, which simplify greatly the reconstruction process. Besides, the fringe contrast of the phase contrast interferogram can be adjusted by changing the modulation depth of the two gratings. The feasibility of the proposed method is verified by theoretical analysis and experiment. © 2012 Optical Society of America.
  Accession Number: 20122915258827
• Record 333 of
  
  Title:Finger capacitance of a terahertz photomixer in low-temperature-grown GaAs using the finite element method
  
  Author(s):Chen, Long-Chao(1); Fan, Wen-Hui(1)
  Source: Chinese Physics B  Volume: 21  Issue: 10  DOI: 10.1088/1674-1056/21/10/104101  Published: October 2012  
  Abstract:Interdigitated finger capacitance of a continuous-wave terahertz photomixer is calculated using the finite element method. For the frequently used electrode width (0.2 μm) and gap width (1.8 μm), the finger capacitance increases quasi-quadratically with the number of electrodes increasing. The quasi-quadratic dependence can be explained by a sequence of lumped capacitors connected in parallel. For a photomixer composed of 10 electrodes and 9 photoconductive gaps, the finger capacitance increases as the gap width increases at a small electrode width, and follows the reverse trend at a large electrode width. For a constant electrode width, the finger capacitance first decreases and then slightly increases as the gap broadens until the smallest finger capacitance is formed. We also investigate the finger capacitances at different electrode and gap configurations with the 8 μm × 8 μm photomixer commonly used in previous studies. These calculations lead to a better understanding of the finger capacitance affected by the finger parameters, and should lead to terahertz photomixer optimization. © 2012 Chinese Physical Society and IOP Publishing Ltd.
  Accession Number: 20124215571670
• Record 334 of
  
  Title:Terahertz and mid-infrared spectroscopy of benzene-1,2-diol
  
  Author(s):Zheng, Zhuan-Ping(1); Fan, Wen-Hui(1); Yan, Hui(1); Liu, Jia(1); Yang, Wen-Zheng(1); Zhu, Shao-Lan(1)
  Source: Journal of Molecular Spectroscopy  Volume: 281  Issue: 1  DOI: 10.1016/j.jms.2012.09.005  Published: November 2012  
  Abstract:The terahertz (THz) and mid-infrared (MIR) spectra of benzene-1,2-diol in the solid state have been modeled by density functional theory (DFT). Calculations of the vibrational spectra based on the optimized geometries provided a good fit to the observed spectra, and a more reasonable spectral reproduction has been achieved than those in previous work. For THz spectrum, the simulation based on the varied unit cell dimension has clearly shown that THz spectral reproduction is affected by the temperature change of unit cell. For MIR spectrum, band assignments are reported in terms of potential-energy distribution (PED), which differ to those previously reported for benzene-1,2-diol in some respects. © 2012 Elsevier Inc. All rights reserved.
  Accession Number: 20124715698649
• Record 335 of
  
  Title:Experimental observation of dissipative soliton resonance in an anomalous-dispersion fiber laser
  
  Author(s):Duan, Lina(1); Liu, Xueming(1); Mao, Dong(1); Wang, Leiran(1); Wang, Guoxi(1)
  Source: Optics Express  Volume: 20  Issue: 1  DOI: 10.1364/OE.20.000265  Published: January 2, 2012  
  Abstract:We have experimentally observed conventional solitons and rectangular pulses in an erbium-doped fiber laser operating at anomalous dispersion regime. The rectangular pulses exhibit broad quasi-Gaussian spectra (∼40 nm) and triangular autocorrelation traces. With the enhancement of pump power, the duration and energy of the output rectangular pulses almost increase linearly up to 330 ps and 3.2 nJ, respectively. It is demonstrated that high-energy pulses can be realized in anomalous-dispersion regime, and may be explained as dissipative soliton resonance. Our results have confirmed that the formation of dissipative soliton resonance is not sensitive to the sign of cavity dispersion. © 2011 Optical Society of America.
  Accession Number: 20120214671680
• Record 336 of
  
  Title:Investigation on the terahertz absorption spectra of the molecules with similar molecular structure
  
  Author(s):Fan, Wen-Hui(1)
  Source: Laser and Tera-Hertz Science and Technology, LTST 2012  Volume:   Issue:   DOI: 10.1364/ltst.2012.sf3a.1  Published: 2012  
  Abstract:The characteristic terahertz absorption features of several molecules with similar molecular structure have been measured by terahertz time-domain spectroscopy experimentally. Theoretical simulations have also been performed, and all measured terahertz absorption features are assigned. © 2012 OSA.
  Accession Number: 20132616443445