Journals >Chinese Optics Letters
Contents
2008
Volume: 6 Issue 1
23 Article(s)
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Research Article
Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar
Xueke Ding, Jian Rong, Hong Bai, Xiu Wang, Jin'e Shen, and Fang Li
A multi-conjugate adaptive optics (MCAO) can offer a possibility of widening field of view (FOV) characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle’s exprA multi-conjugate adaptive optics (MCAO) can offer a possibility of widening field of view (FOV) characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle’s expressions of two deformable mirrors (DMs) MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0101 (2008)
Controlled calibration method for laser induced breakdown spectroscopy
Li Wang, Chijian Zhang, and Yuan Feng
Laser induced breakdown spectroscopy (LIBS) is a potential technique for rapid analysis of samples present in solids, gases and liquids. In the last two decades it was an object of extensive studies. Controlled calibration method used to analysis the LIBS spectra is investigated. Compared with the inner calibration andLaser induced breakdown spectroscopy (LIBS) is a potential technique for rapid analysis of samples present in solids, gases and liquids. In the last two decades it was an object of extensive studies. Controlled calibration method used to analysis the LIBS spectra is investigated. Compared with the inner calibration and calibration-free (CF) methods, this new method overcomes “matrix effect”, and demonstrates a better ability to cope with the spectra. It is used to analyze natural soil, and errors of the concentration are decreased about 5%. The result shows that the new method is feasible and accurate..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0105 (2008)
Improvement on peak-to-trough ratio of sampled fiber Bragg gratings with multiple phase shifts
Bin Xie, Wei Pan, Bin Luo, and Xihua Zou
Via a cascaded structure, the peak-to-trough ratio is considerably improved for sampled fiber Bragg gratings (SFBGs) based on multiple-phase-shift (MPS) technique. This cascaded filter is composed of two identical SFBGs which are inserted with the increasing or decreasing arrangement of phase shifts. With this inverse Via a cascaded structure, the peak-to-trough ratio is considerably improved for sampled fiber Bragg gratings (SFBGs) based on multiple-phase-shift (MPS) technique. This cascaded filter is composed of two identical SFBGs which are inserted with the increasing or decreasing arrangement of phase shifts. With this inverse arrangement of MPS in grating design, the phase fluctuation of individual SFBG can be compensated, and as a result an excellent phase matching condition is realized. In this way, the peak-to-trough ratio in reflection spectra is improved from 6 to 12 dB when multiplication factor m=4, and from 5 dB to 10 dB when m=8..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0109 (2008)
A new demodulation technique for optical fiber interferometric sensors with [3×3] directional couplers
Tingting Liu, Jie Cui, Desheng Chen, Ling Xiao, and Dexing Sun
Optical fiber interferometric sensors based on [3×3] couplers have been used in many fields. A new technique is proposed to demodulate output signals of this kind of sensors. The technique recovers the signal of interest by fitting coefficients of elliptic (Lissajous) curves between each fiber pair. Different fromOptical fiber interferometric sensors based on [3×3] couplers have been used in many fields. A new technique is proposed to demodulate output signals of this kind of sensors. The technique recovers the signal of interest by fitting coefficients of elliptic (Lissajous) curves between each fiber pair. Different from other approaches, this technique eliminates the dependence on the idealization of [3×3] coupler, provides enhanced tolerance to the variance of photoelectric converters, and is anti-polarization in a certain extent. The main algorithm has been successfully demonstrated both by numerical simulation and experimental result..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0112 (2008)
Simulation and experimental research on polymer fiber mode selection polished coupler
Fan Ji, Lixin Xu, Feng Li, Chun Gu, Kun Gao, and Hai Ming
Multimode dispersion is the main obstacle for high bandwidth in multimode optical fiber (MMF) communication system. Mode selection is an effective method to oppress multimode dispersion. We propose and investigate a kind of polymer optical fiber polished coupler. Beam propagation method (BPM) is employed to calculate tMultimode dispersion is the main obstacle for high bandwidth in multimode optical fiber (MMF) communication system. Mode selection is an effective method to oppress multimode dispersion. We propose and investigate a kind of polymer optical fiber polished coupler. Beam propagation method (BPM) is employed to calculate the coupling coefficient of transmission modes in MMF coupler, and an output pattern from coupling branch is obtained. Analysis and experiment show that this coupler can select certain modes by changing polished depth, contact area, and intersection angle of two branches, which means that the device can be employed both as a mode selector and a sensor. In addition, simulation shows that five times bandwidth enhancement may be realized by selecting modes with the polymer fiber polished coupler..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 16 (2008)
Impacts of seed power on amplification performance in pulsed double-clad fiber amplifier
Fangpei Zhang, Qihong Lou, Jun Zhou, Hongming Zhao, Songtao Du, Jingxing Dong, Yunrong Wei, Bing He, Jinyan Li, Jianqiang Zhu, and Zhijiang Wang
A pulsed master-oscillator fiber power amplifier system with near diffraction-limited output by use of China-made large-mode-area fiber and a (2+1)×1 multimode combiner is reported. The effect of the seed power on the amplification performance is found. For the seed power, there exists a range within which the pulA pulsed master-oscillator fiber power amplifier system with near diffraction-limited output by use of China-made large-mode-area fiber and a (2+1)×1 multimode combiner is reported. The effect of the seed power on the amplification performance is found. For the seed power, there exists a range within which the pulsed fiber amplifier can operate safely and reliably at a certain pump power. With the seed average power of 70 mW, the amplification performances of the fiber amplifier are investigated..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0119 (2008)
Broadband dispersion compensating fiber using index-guiding photonic crystal fiber with defected core
Ming Wu, Dexiu Huang, Hairong Liu, and Weijun Tong
We present a novel broadband dispersion compensating photonic crystal fiber with defected core in this paper. The small central defect of air hole can flexibly control the chromatic dispersion properties of this kind of photonic crystal fiber. This kind of fiber has broadband large negative chromatic dispersion, and thWe present a novel broadband dispersion compensating photonic crystal fiber with defected core in this paper. The small central defect of air hole can flexibly control the chromatic dispersion properties of this kind of photonic crystal fiber. This kind of fiber has broadband large negative chromatic dispersion, and the chromatic dispersion coefficient varies from -440 to -480 ps/(nm·km) in the measured wavelength range of 1500-1625 nm. The calculated chromatic dispersion curve is well matched to the measured chromatic dispersion coefficient in the range of 1500-1625 nm. The proposed photonic crystal fiber can be used to design the dispersion compensating fiber in the desired wavelength range by adjusting its structural parameters..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0122 (2008)
In-situ measurement of the surface temperature during holographic recording
A. Draude, R. Meinhardt, H. Franke, Y. Zhao, and R. A.
Photo-induced processes in organic materials mostly occur on molecular levels. Excited molecules may split to form radicals, starting a polymerization process with diffusing monomers. The azo-dyes perform an optically induced cis-trans isomerization. During pattern formation like a holographic grating, the local temperPhoto-induced processes in organic materials mostly occur on molecular levels. Excited molecules may split to form radicals, starting a polymerization process with diffusing monomers. The azo-dyes perform an optically induced cis-trans isomerization. During pattern formation like a holographic grating, the local temperature increase, especially in thin films, is up to date a subject of estimation from absorption and dissipation data. However, the exact knowledge of the surface temperature would help a lot in understanding the resulting refractive index and thickness patterns during holographic exposure. In this paper, in-situ pyrometer measurements are presented. As examples, different photosensitive materials, varying from a photopolymer to polycrystalline azo dyes, are used in order to outline the magnitude of this effect and demonstrate the feasibility of this technique..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0125 (2008)
Real-time, continuous-wave terahertz imaging by a pyroelectric camera
Jun Yang, Shuangchen Ruan, and Min Zhang
Real-time, continuous-wave terahertz (THz) imaging is demonstrated. A 1.89-THz optically-pumped far-infrared laser is used as the illumination source, and a 124×124 element room-temperature pyroelectric camera is adopted as the detector. With this setup, THz images through various wrapping materials are shown. TheReal-time, continuous-wave terahertz (THz) imaging is demonstrated. A 1.89-THz optically-pumped far-infrared laser is used as the illumination source, and a 124×124 element room-temperature pyroelectric camera is adopted as the detector. With this setup, THz images through various wrapping materials are shown. The results show that this imaging system has the potential applications in real-time mail and security inspection..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0129 (2008)
Relationship between normalized light intensity and attenuated total reflection ratio
Yingcai Wu, and Zhengtian Gu
Attenuated total reflection (ATR) ratio is usually utilized to study the properties of surface plasmon resonance (SPR) sensors. The relationship between normalized light intensity and ATR ratio is investigated, and a modification coefficient is put forward to describe the relationship. A mathematical expression is builAttenuated total reflection (ATR) ratio is usually utilized to study the properties of surface plasmon resonance (SPR) sensors. The relationship between normalized light intensity and ATR ratio is investigated, and a modification coefficient is put forward to describe the relationship. A mathematical expression is built up for the coefficient based on Fresnel principle. The result shows that the ATR ratio, which cannot be measured directly in experiments, can be determined with the coefficient and the normalized intensity of light. The characteristic of the coefficient is also discussed..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0132 (2008)
Predictive visual tracking based on least absolute deviation estimation
Rongtai Cai, and Yanjie Wang
To cope with the occlusion and intersection between targets and the environment, location prediction is employed in the visual tracking system. Target trace is fitted by sliding subsection polynomials based on least absolute deviation (LAD) estimation, and the future location of target is predicted with the fitted tracTo cope with the occlusion and intersection between targets and the environment, location prediction is employed in the visual tracking system. Target trace is fitted by sliding subsection polynomials based on least absolute deviation (LAD) estimation, and the future location of target is predicted with the fitted trace. Experiment results show that the proposed location prediction algorithm based on LAD estimation has significant robustness advantages over least square (LS) estimation, and it is more effective than LS-based methods in visual tracking..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0135 (2008)
Variational denoising method for electronic speckle pattern interferometry
Fang Zhang, Wenyao Liu, Chen Tang, Jinjiang Wang, and Li Ren
Traditional speckle fringe patterns by electronic speckle pattern interferometry (ESPI) are inherently noisy and of limited visibility, so denoising is the key problem in ESPI. We present the variational denoising method for ESPI. This method transforms the image denosing to minimizing an appropriate penalized energy fTraditional speckle fringe patterns by electronic speckle pattern interferometry (ESPI) are inherently noisy and of limited visibility, so denoising is the key problem in ESPI. We present the variational denoising method for ESPI. This method transforms the image denosing to minimizing an appropriate penalized energy function and solving a partial differential equation. We test the proposed method on computer-simulated and experimental speckle correlation fringes, respectively. The results show that this technique is capable of significantly improving the quality of fringe patterns. It works well as a pre-processing for the fringe patterns by ESPI..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0138 (2008)
Highly efficient cascaded P-doped Raman fiber laser pumped by Nd:YVO3 solid-state laser
Chaohong Huang, Zhiping Cai, Zhengqian Luo, Wencai Huang, Huiying Xu, and Chenchun Ye
A highly efficient cascaded P-doped Raman fiber laser (RFL) pumped by a 1064-nm continuous wave (CW) Nd:YVO3 solid-state laser is reported. 1.15-W CW output power at 1484 nm is obtained while the input pump power is 4 W, corresponding to the power conversion efficiency of 28.8%. The threshold pump power for the second-A highly efficient cascaded P-doped Raman fiber laser (RFL) pumped by a 1064-nm continuous wave (CW) Nd:YVO3 solid-state laser is reported. 1.15-W CW output power at 1484 nm is obtained while the input pump power is 4 W, corresponding to the power conversion efficiency of 28.8%. The threshold pump power for the second-order Stokes radiation is 1.13 W. The slope efficiency is as high as 42.6%. The experimental results are in good agreement with theoretical ones. Furthermore, the power instability of the P-doped RFL at 1484 nm in an hour is observed to be less than 5%..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0141 (2008)
Short Tm3+-doped fiber lasers with watt-level output near 2 μm
Yulong Tang, Yong Yang, Xiaojin Cheng, and Jianqiu Xu
High-power operation of diode-pumped fiber lasers at wavelength near 2 μm are demonstrated with short length of heavily Tm3+-doped silica glass fibers. With 7-cm long fiber, a laser at near 2 μm is obtained with the threshold of 135 mW, maximum output power of 1.09 W, and slope efficiency of 9.6% with respect to the laHigh-power operation of diode-pumped fiber lasers at wavelength near 2 μm are demonstrated with short length of heavily Tm3+-doped silica glass fibers. With 7-cm long fiber, a laser at near 2 μm is obtained with the threshold of 135 mW, maximum output power of 1.09 W, and slope efficiency of 9.6% with respect to the launched power from a laser diode at 790 nm. The output stability of this fiber laser is within 5%. The dependence of the performance of fiber lasers on the operation temperature and cavity configuration parameters is also investigated..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0144 (2008)
Influences of laser in low power YAG laser-MAG hybrid welding process
Ruisheng Huang, Liming Liu, and Fan Zhang
The influences of laser defocusing amount Δz, laser power P, space distance DLA between laser and arc on weld penetration, arc modality and stability are investigated in low power YAG laser and metal active gas (laser-MAG) hybrid welding process. The experimental results indicate that the effects of laser-induced attraThe influences of laser defocusing amount Δz, laser power P, space distance DLA between laser and arc on weld penetration, arc modality and stability are investigated in low power YAG laser and metal active gas (laser-MAG) hybrid welding process. The experimental results indicate that the effects of laser-induced attraction and contraction of MAG arc are emerged in hybrid welding process, which result in the augmentation of hybrid welding energy. When DLA=-0.5-2 mm, Δz=-2-2 mm and P≥73 W, the synergic efficiency between laser and MAG arc is obvious, the cross section at the root of hybrid arc is contracted and the hybrid weld penetration is increased. The maximal ratio of hybrid/MAG weld penetration is 1.5 and the lowest YAG laser power that augments MAG arc is 73 W. The input of YAG laser makes the stabilities of arc ignition and combustion prominent in hybrid welding process..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0147 (2008)
Influence of scanning velocity on femtosecond laser direct writing lines on FOTURAN glass
Yinzhong Wu, Ching-Yue Wang, Wei Jia, Xiaochang Ni, Minglie Hu, and Lu Chai
Lines are induced on the surface of a photosensitive (FOTURAN) glass by focused femtosecond laser transverse writing with scanning velocity in a wide range of 40-1800 μm/s. The formed lines are analyzed using scanning electron microscope (SEM) and optical microscope (OM). It is observed that three distinct morphologiesLines are induced on the surface of a photosensitive (FOTURAN) glass by focused femtosecond laser transverse writing with scanning velocity in a wide range of 40-1800 μm/s. The formed lines are analyzed using scanning electron microscope (SEM) and optical microscope (OM). It is observed that three distinct morphologies of lines are produced depending on the scanning velocity. Lines written in low velocity level (40-100 μm/s) and high velocity level (1000-1800 μm/s) are uniform and regular, while those written in moderate velocity level (150-600 μm/s) are rough. The influence of scanning velocity is explained based on different pulses overlapping or cumulative dose of laser exposure in irradiated area. Fabrication of shallow groove on the surface is also demonstrated..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0151 (2008)
Influence of substrate process tolerances on transmission characteristics of frequency-selective surface
He Zhang, Jun Lu, Guancheng Sun, and Hongliang Xiao
Frequency-selective surface (FSS) is a two-dimensional periodic structure consisting of a dielectric substrate and the metal units (or apertures) arranged periodically on it. When manufacturing the substrate, its thickness and dielectric constant suffer process tolerances. This may induce the center frequency of the FSFrequency-selective surface (FSS) is a two-dimensional periodic structure consisting of a dielectric substrate and the metal units (or apertures) arranged periodically on it. When manufacturing the substrate, its thickness and dielectric constant suffer process tolerances. This may induce the center frequency of the FSS to shift, and consequently influence its characteristics. In this paper, a bandpass FSS structure is designed. The units are the Jerusalem crosses arranged squarely. The mode-matching technique is used for simulation. The influence of the tolerances of the substrate’s thickness and dielectric constant on the center frequency is analyzed. Results show that the tolerances of thickness and dielectric constant have different influences on the center frequency of the FSS. It is necessary to ensure the process tolerance of the dielectric constant in the design and manufacturing of the substrate in order to stabilize the center frequency..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0154 (2008)
Realization of absolute negative refraction index by a photonic crystal using anisotropic dielectric material
Yuntuan Fang, and Zhengbiao Ouyang
A method to realize absolute negative refraction index [EQUATION] with a two-dimensional (2D) photonic crystal is presented by introducing dielectric anisotropy in the photonic crystal material. The band structures of E-polarization mode and H-polarization mode can be adjusted by changing the parameters of materials. TA method to realize absolute negative refraction index [EQUATION] with a two-dimensional (2D) photonic crystal is presented by introducing dielectric anisotropy in the photonic crystal material. The band structures of E-polarization mode and H-polarization mode can be adjusted by changing the parameters of materials. Thus the two modes with different polarizations have the same negative refraction index [EQUATION] for the same frequency. The results are demonstrated by numerical simulation based on the finite-difference time-domain (FDTD) method..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0157 (2008)
Characterization of PolyA and PolyC mismatches by Raman spectroscopy
Yubo Liao, Yaoyong Meng, Haodong Lei, and Ying Wang
A·C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na+, pH7.0. Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by oA·C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na+, pH7.0. Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7. The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0161 (2008)
Investigation of KTiOPO4 nanocrystals by means of second-harmonic light emission
Chunyuan Zhou, Loc Le, Abdallah Slablab, Nicolas Sandeau, Sophie Brasselet, Dominique Chauvat, and Jean-Francois Roch
The finding of nonlinear nanometric-sized probes is of key importance for the development of nonlinear microscopy in physical as well as biological sciences. We isolate nonlinear KTiOPO4 nanocrystals and study them by second-harmonic generation microscopy (SHGM) and atomic force microscopy (AFM) independently. With botThe finding of nonlinear nanometric-sized probes is of key importance for the development of nonlinear microscopy in physical as well as biological sciences. We isolate nonlinear KTiOPO4 nanocrystals and study them by second-harmonic generation microscopy (SHGM) and atomic force microscopy (AFM) independently. With both polarization analysis and defocused imaging of the emitted second harmonic field, we extract the Euler angles of the crystalline axes of a single nanocrystal. A balanced coherent optical homodyne detection shows the coherent nature of the nanocrystal nonlinear emission and allows a phase measurement of the emitted second-harmonic field. These features make the KTiOPO4 nanocrystal a good candidate for a vectorial probe of electromagnetic near fields..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0164 (2008)
Performance evaluation of ZnGeP2 optical parametric oscillator pumped by a Q-switched Tm,Ho:GdVO4 laser
Baoquan Yao, Youlun Ju, Yuezhu Wang, and Wanjun He
A doubly resonant ZnGeP2 (ZGP) optical parametric oscillator (OPO) pumped by a novel Tm,Ho:GdVO4 laser was demonstrated. Cryogenic Tm(5 at.-%), Ho(0.5 at.-%):GdVO4 laser with high pulse repetition frequency (PRF) of 10 kHz at 2.05 μm was employed as pumping source of ZGP OPO. The 15-mm-long ZGP crystal, 55° cut foA doubly resonant ZnGeP2 (ZGP) optical parametric oscillator (OPO) pumped by a novel Tm,Ho:GdVO4 laser was demonstrated. Cryogenic Tm(5 at.-%), Ho(0.5 at.-%):GdVO4 laser with high pulse repetition frequency (PRF) of 10 kHz at 2.05 μm was employed as pumping source of ZGP OPO. The 15-mm-long ZGP crystal, 55° cut for I-type phase-matching with low absorption coefficient less than 0.05 cm-1 at 2 μm, was placed in a plano-plano cavity with resonator length of 30 mm. The ZGP OPO generated a total combined output power of 1.2 W at 3.75 and 4.52 μm under pumping power of 5.3 W, corresponding to slope efficiency of 40% from incident 2-μm laser power to mid-infrared (Mid-IR) output. A widely tunable range from 3.0 to 6.5 μm was achieved by changing the crystal angle only 3.5°..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0168 (2008)
Growth and characterization of InAs quantum dots with low-density and long emission wavelength
Lin Li, Guojun Liu, Zhanguo Li, Mei Li, and Xiaohua Wang
The growth parameters affecting the deposition of self-assembled InAs quantum dots (QDs) on GaAs substrate by low-pressure metal-organic chemical vapor deposition (MOCVD) are reported. The low-density InAs QDs (~5×108 cm-2) are achieved using high growth temperature and low InAs coverage. Photoluminescence (PL) meThe growth parameters affecting the deposition of self-assembled InAs quantum dots (QDs) on GaAs substrate by low-pressure metal-organic chemical vapor deposition (MOCVD) are reported. The low-density InAs QDs (~5×108 cm-2) are achieved using high growth temperature and low InAs coverage. Photoluminescence (PL) measurements show the good optical quality of low-density QDs. At room temperature, the ground state peak wavelength of PL spectrum and full-width at half-maximum (FWHM) are 1361 nm and 23 meV (35 nm), respectively, which are obtained as the GaAs capping layer grown using triethylgallium (TEG) and tertiallybutylarsine (TBA). The PL spectra exhibit three emission peaks at 1361, 1280, and 1204 nm, which correspond to the ground state, the first excited state, and the second excited state of the QDs, respectively..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0171 (2008)
Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser
Jian Wu, Hua Cai, Xiaohong Han, and Heping Zeng
Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on tOur experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 6, Issue 1, 0176 (2008)
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