Browsing by Author "Wei, MD"

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Beam-propagation-dominant instability in an axially pumped solid-state laser near degenerate resonator configurations
(2001-08-01)
Chen, CH
;
Wei, MD
;
Hsieh, WF
;
光電工程學系
;
Department of Photonics
Propagation-dominant instabilities and chaos were found under so-called good-cavity conditions in an axially pumped solid-state laser operated near the 1/3-degenerate cavity configuration that had not previously been studied numerically. By using the generalized Huygens integral together with rate equations, we obtained a V-shaped configuration that depends on a quasi-periodic threshold. We call the propagation dominant because the laser behaves as a conservative system governed by beam propagation. Although it had previously been predicted that chaos would be impossible under nearly degenerate conditions, we have recognized that the laser is transformed into chaos as a result of the interplay of beam propagation and gain dynamics as the cavity is tuned close to degeneracy. (C) 2001 Optical Society of America.
Bifurcation of fundamental Gaussian modes in Kerr-lens mode-locked lasers
(1999-09-01)
Wei, MD
;
Hsieh, WF
;
光電工程學系
;
Department of Photonics
We propose that more than one spatial fundamental Gaussian mode may occur in concentric and confocal resonators under persisting nonlinear effect. Extensively studying the influence of the resonator's parameters in a Kerr-lens mode-locked resonator, pitchfork bifurcation results in more symmetrical configurations, and saddle-node bifurcation appears as the symmetry being broken. From the properties of bifurcation, we suggest that the equal-arm and near-confocal resonator is suitable for the emergence of bistability in Kerr-lens mode-locked lasers. (C) 1999 Elsevier Science B.V. All rights reserved.
Cavity configurations for soft-aperture Kerr-lens mode locking and multiple-period bifurcations in Ti : sapphire lasers
(2001-08-01)
Lin, JH
;
Wei, MD
;
Hsieh, WF
;
光電工程學系
;
Department of Photonics
We find that soft-aperture Kerr-lens mode locking (SAKLM) in a Ti:sapphire laser always takes place around certain discrete cavity configurations accompanied by peculiar beam patterns. By correlating the superposition of proper transverse modes to the observed beam patterns and fitting the beat frequencies to the resonance equation, we discovered that the patterns for SAKLM are formed by phase locking of the fundamental mode with specific degenerate transverse modes that occur near different degenerate cavity configurations. As predicted by the stability analysis, period-3 and period-2 SAKLM does occur around the 1/3- and 1/4-degenerate cavity configurations, which cannot be fully explained in terms of total mode locking of TEM00 and TEM01 modes. (C) 2001 Optical Society of America.
Cavity-configuration-dependent nonlinear dynamics in Kerr-lens mode-locked lasers
(2000-08-01)
Wei, MD
;
Hsieh, WF
;
光電工程學系
;
Department of Photonics
We determined theoretically that the nonlinear dynamics of a Gaussian beam is configuration dependent in a general cavity. This prediction was confirmed by numerical simulation in a Kerr-lens mode-locked cavity for which the self-focusing effect is considered the nonlinear source in both the spatial and the temporal domains. Period doubling, tripling, and quadrupling can occur in these configurations with the products of generalized cavity G parameters equal to 1/2, 1/4 (or 3/4), and (2 +/- root 2)/4, respectively. The dynamic behavior of the cavity beam will become irregular if the nonlinear effect is further increased. (C) 2000 Optical Society of America [S0740-3224(00)00708-6] OCIS codes: 140.3410, 140.4050, 260.5950, 140.1540.
Dynamics of an optical resonator determined by its iterative map of beam parameters
(1998-01-15)
Wei, MD
;
Hsieh, WF
;
Sung, CC
;
光電工程學系
;
Department of Photonics
We use the residue of the map to study the stability and Gaussian beam dynamics of a general optical resonator. The map is constructed from space domain matrix formalism. For a lossless system we find that the residue is a function of resonator g-parameters' product and new critical stable curves exist within the geometrically stable regions. The dynamic behavior of a dissipative resonator with loss optical element is similar to a damping oscillatory motion and can be determined by the corresponding conservative resonator without those loss elements. (C) 1998 Elsevier Science B.V.
Multibeam-waist modes in an end-pumped Nd : YVO4 laser
(2003-06-01)
Chen, CH
;
Tai, PT
;
Hsieh, WF
;
Wei, MD
;
光電工程學系
We studied both numerically and experimentally the transverse modes near degenerate resonator configurations such as g(1)g(2) = 1/4, 1/2, 3/4 in a simple plano-concave Nd:YVO4 laser with a small pump size. We found that there are stationary modes that show an additional beam waist besides the well-known waist on the flat mirror end near 9 19 2 = 1/4, 3/4. When the specific modes of the three degeneracies propagate through a lens, they are capable of exhibiting multiple beam waists. The multibeam-waist mode possesses a small waist size without a ring structure in the near field on the flat mirror end; nevertheless, it has a far-field pattern with many concentric rings. The numerical results show good agreement with the experimental observations. Furthermore, by simultaneously considering the wavelike and the raylike character of the multibeam-waist mode, we found that it can be represented as a superposition of N consecutive round-trip electric fields of period-N solution in the degenerate empty cavity, where N = 2 for g(1)g(2) = 1/2 and N = 3 for g(1)g(2) 1/4, 3/4. (C) 2003 Optical Society of America.
Resonator configuration dependent nonlinear dynamics with application to Kerr-lens mode-locked lasers
(1999)
Hsieh, WF
;
Wei, MD
;
Wu, HH
;
光電工程學系
;
Department of Photonics
The nonlinear dynamics of the Gaussian beam propagation in resonator was studied by constructing the iterative map of q-parameter. From the Greene's residue theorem, there are specific configurations sensitive to nonlinear effect existing in the geometrically stable region. By applying to Kerr-lens mode-locking (KLM) resonators, we found that multiple solution, period doubling, period tripling and period quadrupling can occur at the configurations with product of cavity G-parameters equal. to 0, 1/2, 1/4 (or 3/4) and (2 +/- root 2)/4, respectively. Moreover, the systems will result in classical chaos if further increasing the nonlinear effect. We will report the appearance of unexpected transverse beam profiles and shrinkage of beam waist causes to lower laser threshold in an end-pumped Nd:YVO4 laser and chaotic behavior in the KLM laser around these critical resonator configurations.
The preferable resonators for Kerr-lens mode-locking determined by stability factors of their iterative maps
(1998-10-15)
Wei, MD
;
Hsieh, WF
;
Sung, CC
;
光電工程學系
;
Department of Photonics
The generalized stability factor of a general resonator was obtained from its iterative map based on the linear stability analysis. Since a physical system tends to stay with high stability, the preferred resonator for Kerr-lens mode-locking (KLM) is determined by the relative stability between KLM and CW operations. With this criterion the preferable KLM regions agree with the previous experimental self-starting regions when the Ken medium is located around the center of the resonator. (C) 1998 Elsevier Science B.V. All rights reserved.
The preferable resonators for Kerr-lens mode-locking determined by stability factors of their iterative maps
(1998-10-15)
Wei, MD
;
Hsieh, WF
;
Sung, CC
;
光電工程研究所
;
Institute of EO Enginerring
The generalized stability factor of a general resonator was obtained from its iterative map based on the linear stability analysis. Since a physical system tends to stay with high stability, the preferred resonator for Kerr-lens mode-locking (KLM) is determined by the relative stability between KLM and CW operations. With this criterion the preferable KLM regions agree with the previous experimental self-starting regions when the Ken medium is located around the center of the resonator. (C) 1998 Elsevier Science B.V. All rights reserved.