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91.
R. Paschotta J. Aus der Au G.J. Spühler S. Erhard A. Giesen U. Keller 《Applied physics. B, Lasers and optics》2001,72(3):267-278
We recently demonstrated that passive mode locking of a thin-disk Yb:YAG laser is possible and that this concept leads to
sources of femtosecond pulses with very high average power. Here we discuss in detail the effect of spatial hole burning on
the mode-locking behavior of such lasers. We have developed an efficient numerical model and arrive at quantitative stability
criteria which agree well with experimental data. The main result is that stable soliton mode locking can in general be obtained
only in a certain range of pulse durations. We use our model to investigate the influence of various cavity parameters and
the situation for different gain media. We also consider several methods to reduce the effect of spatial hole burning in order
to expand the range of possible pulse durations.
Received: 4 September 2000 / Published online: 10 January 2001 相似文献
92.
Dielectric studies on copper doped derivatives of polycrystalline layered mixed alkali trititanate Na1.8K0.2Ti3O7 ceramics indicate that the losses are of mixed type and decrease on copper doping. However, the temperature dependent permittivity plots are characteristic of the diffuse nature of a possible ferroelectric phase transition and hence give indication of relaxor ferroelectric behaviour. From the EPR spectra, recorded at room temperature, it can be seen that the substitution of copper occurs at Ti4+ as preferred site with a divalent oxidation state (Cu2+) for all compositions. Also, copper doping enhances the transition temperature, which is indicative of the stabilization of the existing ferroelectric phase up higher temperatures. Besides bolstering electron hopping conduction, acceptor doping restrains the interlayer ionic conduction. Moreover, electron hopping (polaron) conduction is dominant over the lower temperature region, while interlayer ionic conduction prevails in the higher temperature region. 相似文献
93.
F.H. Loesel C. Horvath F. Grasbon M. Jost M.H. Niemz 《Applied physics. B, Lasers and optics》1997,65(6):783-787
Received: 16 July 1997/Revised version: 24 September 1997 相似文献
94.
The optical response of a single-mode uncoated fiber tip to a 3D polarized field, including longitudinal components, is investigated. The 3D field is produced by an opportune superposition of TE and TM plane waves. The contribution of the different field components to the detected signals was discriminated by integrating the scanning probe microscope with a multi-heterodyne detection technique. A simple coupling model for the tip is introduced. The longitudinal field component was assumed to couple to the transverse fiber modes through complex coupling coefficients. Coupling coefficients were obtained by fitting the parameters of the model to the experimental data. These results demonstrate that the longitudinal components of the field are coupled by this probe with an efficiency approximately equal to that of the transverse polarization components. 相似文献
95.
We report on the development of a pulsed diode end-pumped Nd:YAG laser mode-locked by a nonlinear mirror and stabilized by an acousto-optical modulator. With the introduction of appropriate intracavity loss, the laser is able to generate 22.8 ps pulses with the energy of 4.5 μJ. After amplification and frequency doubling stages, the second harmonic radiation is used to non-collinearly synchronously pump a β-barium borate optical parametric oscillator in a walk-off compensated scheme. The system demonstrates a wide-tuning range from 635 nm to 2.55 μm for the signal output, with maximum average conversion efficiency as high as 42%. 相似文献
96.
T. Yamaguchi 《Solid State Communications》2004,131(6):377-381
A new spin-density-wave (SDW) system with magnetic impurities (TMTSF)2(AsF6)1−x(FeCl4)x was prepared and its magnetic properties were studied by means of magnetization and electron-spin-resonance measurements. The anisotropic g-value and comparison of the Fe concentration with the Curie constant indicate that the Fe3+ ions are in a low-spin state. We also found that the magnetization curve of the impurity spins in this compound shows an anomalous behavior. This behavior can be explained if one assumes a field-dependent magnetic interaction between the Fe3+ spins and the SDW moment. We suppose that the field dependence of the SDW pinning potential is responsible for this phenomenon. 相似文献
97.
The metastable state appearing at neutral pH in the Fc fragment after its brief incubation at pH 2.5 was studied using scanning
microcalorimetry, high-flow sedimentation and fluorescence polarization. It was shown that the metastable state of the Fc
fragment is characterised by smaller melting enthalpy of CH2 domains as compared with that of the stable state which is explained by reduced interaction of CH2 and CH3domains. As seen from the decrease in the sedimentation coefficient, this leads to diminution of compactness of the Fc fragment
molecule. The intramolecular motility of CH2 domains increases judging by the fluorescence polarization data.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
98.
J. L. Yang S. C. Tjin N. Q. Ngo R. T. Zheng 《Applied physics. B, Lasers and optics》2005,80(4-5):445-448
A novel actively mode-locked multi-wavelength tunable fiber laser with equally increased or decreased wavelength spacing is presented. It is constructed using a double-ring cavity combined with an amplitude modulator and cascaded fiber Bragg gratings (FBGs). The cavity lengths for all FBGs are intrinsically identical due to the double-ring configuration, and simultaneous mode locking of multiple wavelengths is therefore achieved by applying only one mode-locking signal to the modulator. The FBGs are mounted on a organic plate with angles between adjacent gratings such that the forces applied to the FBGs have an equal force increment; thus, stretching or compressing the cascaded FBGs can achieve a wavelength tuning with equally increased or decreased wavelength spacing.This revised version was published online in March 2005. In the previous version, the published online date was missing 相似文献
99.
Véronique Zambon 《Optics Communications》2006,264(1):180-186
Tunable dual-wavelength operation of a laser diode has been achieved using a dual-period holographic element. The holographic element was positioned in Littrow configuration in an external cavity. The design of this holographic element was based on the superposition of a constant-period grating and a variable-period grating on the same location in a photoresist. We observed simultaneous emission at two wavelengths from a visible semiconductor laser operated with this holographic element. The spectral separation of the dual-wavelength output was varied from 0.76 to 6.27 nm by a simple translation of the holographic element. 相似文献
100.
A technique is presented for determining the frequency modulation transfer function of a laser. The method is based on a Mach–Zehnder interferometer, with a significant difference in the optical path lengths of the two arms. A frequency-modulated laser beam incident on the interferometer produces a phase-modulated photocurrent signal with an effective modulation index that is related to the amplitude of the optical frequency modulation. Techniques for determining both the amplitude and the phase of the optical frequency modulation from the photocurrent signal are described. 相似文献