Browsing by Author "Lu, T. H."

Now showing 1 - 19 of 19

Exploring vortex structures in orbital-angular-momentum beams generated from planar geometric modes with a mode converter
(2016-10-03)
Tung, J. C.
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Liang, H. C.
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Lu, T. H.
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Huang, K. F.
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Chen, Y. F.
It is theoretically demonstrated that the planar geometric mode with a pi/2 mode converter, so called the circularly geometric mode, can be solved from the inhomogeneous Helmholtz equation by considering the pump distribution on the lasing mode. Theoretical analysis clearly reveal that the vortex structures of circularly geometric modes are determined by the minimum order of transverse lasing modes, the total number of transverse lasing modes and the degenerate condition in the cavity. Moreover, we experimentally manifest that the circularly geometric mode can be generated from the selective pumped solid-state laser with an external pi/2 mode converter. To explore the vortex structures of the generated geometric modes, the interference patterns are performed by an experimental apparatus consisting of a Mach-Zehnder interferometer. The good agreement between experimental observations and numerical calculations confirms the analysis of vortex structures is reliable. (C) 2016 Optical Society of America
Generalized hyperboloid structures of polarization singularities in Laguerre-Gaussian vector fields
(2007-12-01)
Lu, T. H.
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Chen, Y. F.
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Huang, K. F.
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電子物理學系
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Department of Electrophysics
We present the propagation-dependent polarization vector fields by use of an isotropic microchip laser with the longitudinal-transverse coupling and the entanglement of the polarization states. With the coherent superposition of orthogonal circularly polarized vortex modes which are made up of two Laguerre-Gaussian modes with different order, the experimental three-dimensional vector fields can be reconstructed analytically. From the theoretical analyses, the generalized structures of singularities such as V points, C lines, and L surfaces can be clearly demonstrated. Importantly, the projections of C lines on the transverse plane are found to form the intriguing petal structures.
Generation of multi-axis Laguerre-Gaussian beams from geometric modes of a hemiconfocal cavity
(2011-06-01)
Lu, T. H.
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Lin, Y. C.
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Chen, Y. F.
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Huang, K. F.
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電子物理學系
We study the transformation of multi-axis Laguerre-Gaussian beams from optical beams comprising Hermite-Gaussian modes with ray-wave duality. By use of cylindrical lenses, Hermite-Gaussian modes can be transformed into Laguerre-Gaussian modes possessing optical orbital angular momentum. The superposed Hermite-Gaussian modes localized on geometric trajectories are generated from a degenerate hemiconfocal cavity and transformed into multi-axis Laguerre-Gaussian beams. Experimental results of the structured beams are systematically manipulated and in good agreement with theoretical analyses.
Generation of optical vortex array with transformation of standing-wave Laguerre-Gaussian mode
(2011-05-23)
Lin, Y. C.
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Lu, T. H.
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Huang, K. F.
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Chen, Y. F.
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電子物理學系
We develop a novel method of creating optical vortex array by the conversion of a standing-wave Laguerre-Gaussian (LG) mode. Theoretically, by employing the transformational relation, the standing-wave LG mode is verified to be transformed from a pair of crisscrossed Hermite-Gaussian (HG) modes, embedded with optical vortex array, consists of a TEM(n,m) mode and a TEM(m,n) mode. Due to close correspondence between the transformational relation and the mode conversion of astigmatic lenses, we successfully generate the optical vortex array by transforming a standing-wave LG mode into the crisscrossed HG modes via a pi/2 cylindrical lens mode converter. The investigation may provide useful insight in the study of the vortex light beam and its further applications. (C) 2011 Optical Society of America
Generation of polarization-entangled optical coherent waves and manifestation of vector singularity patterns
(2007-02-01)
Lu, T. H.
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Chen, Y. F.
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Huang, K. F.
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電子物理學系
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Department of Electrophysics
We use a high-level isotropic laser with off-axis focused and on-axis circular pumping to generate the high order polarization-entangled transverse modes. The main finding is that the complex transverse modes can be categorized into four types: square pattern, hyperbolic pattern, elliptic pattern, and circular pattern. Importantly, all types of the polarization-entangled modes can be well analyzed with the generalized coherent states. With the connection between theoretical analysis and experimental results, the formation of complex singularities can be clearly represented.
Generation of structured beams in large-Fresnel number degenerate cavities and beam transformation with orbital angular momentum
(2010-01-01)
Lu, T. H.
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Lin, Y. C.
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Chen, Y. F.
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Huang, K. F.
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電子物理學系
We employ a large-Fresnel-number laser system to demonstrate the three-dimensional optical coherent waves localized on Lissajous and trochoidal parametric surfaces with Lissajous and trochoidal transverse patterns in degenerate cavities. The coherent structured beams are verified to be composed of degenerate Hermite-Gaussian and Laguerre-Gaussian modes with different longitudinal indices resulted from longitudinal-transverse coupling. As well known, the Hermite-Gaussian modes can be converted into Laguerre-Gaussian modes possessing orbital angular momentum by use of a pair of cylindrical lens. Consequently, we make use of cylindrical lenses to transform the Lissajous structured beams superposed of degenerate Hermite-Gaussian modes into the intriguing trochoidal structured beam possessing optical orbital angular momentum.
Generation of two-dimensional chaotic vector fields from a surface-emitting semiconductor laser: Analysis of vector singularities
(2007-08-01)
Chen, C. C.
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Su, K. W.
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Lu, T. H.
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Liu, C. C.
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Chen, Y. F.
We demonstrate experimental generation of two-dimensional (2D) chaotic vector fields from a surface-emitting microcavity laser with precisely control of the operating temperature and the operating current. The 2D optical vector field is found to be formed by frequency locking of two linearly polarized laser modes with different chaotic spatial structures. The eigenfunction expansion method is used to reconstruct the experimental wave function for analyzing the properties of the vector singularities. It is shown that the distribution of vector singularities obeys the sign rule of nearest-neighbor singularities in the phase space of the vector field.
Hyperboloid structures formed by polarization singularities in coherent vector fields with longitudinal-transverse coupling
(2006-12-08)
Chen, Y. F.
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Lu, T. H.
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Huang, K. F.
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電子物理學系
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Department of Electrophysics
The propagation-dependent polarization vector fields are experimentally created from an isotropic microchip laser with a longitudinal-transverse coupling and entanglement of the polarization states. The experimental three-dimensional coherent vector fields are analytically reconstructed with a coherent superposition of orthogonal circularly polarized vortex modes. Each polarized component is found to comprise two Laguerre-Gaussian modes with different topological charges. With the analytical representation, the polarization singularities, on which the electric polarization ellipse is purely circular (C lines) or purely linear (L surfaces), are explored. The C line singularities are found to form an intriguing hyperboloidal structure.
Model of commensurate harmonic oscillators with SU(2) coupling interactions: Analogous observation in laser transverse modes
(2012-04-24)
Lin, Y. C.
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Lu, T. H.
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Huang, K. F.
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Chen, Y. F.
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電子物理學系
We theoretically explore the eigenstates of a coupled p:q commensurate harmonic oscillator with SU(2) coupling interactions under the canonical transformation. The spatial patterns of the high-order eigenstates are found to be markedly localized on Lissajous figures from single to multiple periodic orbits. Controlling the pumping size in large-Fresnel-number degenerate cavities, we have experimentally observed the laser transverse modes that display the wave patterns to be analogous to the derived eigenstates.
Observation and analysis of coherent optical waves emitted from large-Fresnel number degenerate cavities
(2009-02-16)
Lu, T. H.
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Lin, Y. C.
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Chen, Y. F.
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Huang, K. F.
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電子物理學系
We demonstrate that the coherent optical waves emitted from large-Fresnel-number degenerate cavities persistently display a sort of salient intensity variations. We use the representation of the coherent states to explore the origin of the salient intensity variations and find that these coherent laser waves arise from a quadrature superposition of two degenerate coherent states. With the analytical representation of the superposed coherent states, we verify that these coherent laser waves possess a large angular momentum per photon. (c) 2009 Optical Society of America
Observation of lasing modes with exotic localized wave patterns from astigmatic large-Fresnel-number cavities
(2010-02-01)
Lu, T. H.
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Lin, Y. C.
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Liang, H. C.
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Huang, Y. J.
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Chen, Y. F.
We investigate the lasing modes in large-Fresnel-number laser systems with astigmatism effects. Experimental results reveal that numerous lasing modes are concentrated on exotic patterns corresponding to intriguing geometries. We theoretically use the quantum operator algebra to construct the wave representation for manifesting the origin of the localized wave patterns. (C) 2010 Optical Society of America
Picosecond optical vortex converted from multigigahertz self-mode-locked high-order Hermite-Gaussian Nd:GdVO(4) lasers
(2009-12-15)
Liang, H. C.
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Huang, Y. J.
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Lin, Y. C.
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Lu, T. H.
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Chen, Y. F.
We report on a gigahertz self-mode-locked high-order Hermite-Gaussian (HG) Nd:GdVO(4) laser. With a pump power of 2.2 W, the average output power for the TEM(0,m) modes from m=9 to m=0 are among 350-780 mW at a repetition rate of 3.5 GHz. The mode-locked pulse width is in the range of 20-25 ps for various HG TEM(0,m) modes. With a simple cylindrical-lens converter, the mode-locked HG beams are converted to generate picosecond optical vortex pulses. (C) 2009 Optical Society of America
Picosecond optical vortex converted from multigigahertz self-mode-locked high-order Hermite-Gaussian Nd:GdVO4 lasers
(2009-12-15)
Liang, H. C.
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Huang, Y. J.
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Lin, Y. C.
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Lu, T. H.
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Chen, Y. F.
We report on a gigahertz self-mode-locked high-order Hermite-Gaussian (HG) Nd:GdVO4 laser. With a pump power of 2.2 W, the average output power for the TEM0,m modes from m=9 to m=0 are among 350-780 mW at a repetition rate of 3.5 GHz. The mode-locked pulse width is in the range of 20-25 ps for various HG TEM0,m modes. With a simple cylindrical-lens converter, the mode-locked HG beams are converted to generate picosecond optical vortex pulses. (C) 2009 Optical Society of America
Selective pumping and spatial hole burning for generation of photon wave packets with ray-wave duality in solid-state lasers
(2016-02)
Tung, J. C.
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Liang, H. C.
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Tuan, P. H.
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Chang, F. L.
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Huang, K. F.
The selective pumping and the spatial hole burning are thoroughly considered to determine the excited transverse and longitudinal eigenmodes. By using the mode locking of the excited eigenmodes, an analytical wave representation is derived to manifest the ray-wave duality of the optical wave packet dynamics in the laser resonator. The derived wave function is employed to extract the parametric formula for the periodic ray orbits that reveal the subtle origin between the hyperbolic caustics and linear trajectories. Moreover, the temporal dynamics of the output beam for the total mode-locked state is theoretically demonstrated by combining with the parametric formula and the derived wave function. More importantly, an experiment based on the self-mode-locked laser is performed to make a comparison with theoretical analysis.
Spatial morphology of macroscopic superposition of three-dimensional coherent laser waves in degenerate cavities
(2008-01-01)
Lu, T. H.
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Chen, Y. F.
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Huang, K. F.
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電子物理學系
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Department of Electrophysics
We employ high-order degenerate laser cavities to analogously investigate the morphology of macroscopic superposition states of three-dimensional coherent waves. The spatial features of macroscopic superposition states are found to exhibit dashed and dotted wave patterns. We evaluate the mode volume to explore the domination of macroscopic superposition states. A large-aperture laser resonator is experimentally implemented to confirm the theoretical results.
Spatial transformation of coherent optical waves with orbital morphologies
(2010-10-01)
Chen, Y. F.
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Lin, Y. C.
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Huang, K. F.
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Lu, T. H.
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電子物理學系
We theoretically verify that converting the Hermite-Gaussian modes into the Laguerre-Gaussian can lead to the spatial morphologies of the two-dimensional (2D) coherent states to be transformed from Lissajous figures to trochoidal curves. With this transformational relationship, we experimentally generate various structured light beams by exploiting a cylindrical-lens mode converter to transform the optical Lissajous modes. The present investigation manifests a notable method to generate optical coherent waves with various orbital spatial morphologies.
Statistical properties of experimental coherent waves in microcavity lasers: Analogous study of quantum billiard wave functions
(2007-04-01)
Chen, C. C.
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Liu, C. C.
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Su, K. W.
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Lu, T. H.
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Chen, Y. F.
We use a microcavity laser to explore the properties of experimental coherent waves as an analogous study of the chaotic wave functions in quantum billiards. With the eigenstate expansion method, the experimental high-order chaotic coherent waves are well reconstructed. The reconstructed wave functions are employed to calculate the field and intensity correlations. It is found that the spreading of k-space (momentum space) distribution leads to not only wave localization in coordinate space but also enhancement of long-range correlations.
Three-Dimensional Coherent Optical Waves Localized on Trochoidal Parametric Surfaces
(2008-12-05)
Lu, T. H.
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Lin, Y. C.
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Chen, Y. F.
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Huang, K. F.
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電子物理學系
We theoretically demonstrate that the three-dimensional (3D) coherent laser waves formed by the degenerate Laguerre-Gaussian modes with different longitudinal indices are well localized on rotating trochoidal parametric surfaces. We further use a large-Fresnel-number laser system to realize the existence of the laser modes related to trochoidal coherent states. Experimental results reveal that the exotic laser modes generally originate from a superposition of two degenerate standing-wave trochoidal coherent states.
Wave functions with localizations on classical periodic orbits in weakly perturbed quantum billiards
(2006-10-01)
Liu, C. C.
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Lu, T. H.
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Chen, Y. F.
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Huang, K. F.
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電子物理學系
We analytically investigate quantum wave functions with localizations on classical periodic orbits (POs) in the circular billiards. We construct the coherent states which are the coherent superpositions of nearly degenerate eigenstates and found to be localized around single classical POs. With the constructed coherent states, we can analytically express the mesoscopic eigenstates in the weakly perturbed systems, which are found to be localized on the ensemble of classical POs. Furthermore, these coherent states can be utilized to study the quantum vortex structures in quantum billiards.