Accepted papers to appear in an upcoming issue
OSA now posts prepublication articles as soon as they are accepted and cleared for production. See the FAQ for additional information.
Phase-controlled optical Faraday rotation in a closed-loop atomic system
- received 09/02/2014; accepted 11/11/2014; posted 11/14/2014; Doc. ID 222371
- [full text: PDF (537) KB)]
- Abstract: We investigate the nonlinear optical Faraday rotation (OFR) of a probe field passing through a double V–type closed-loop atomic system in the absence of external static magnetic field. Enhancement OFR is obtained by applying the control fields to establish the closed-loop configuration. It is shown that the scattering of both control fields into the probe field mode via wave mixing induce an OFR enhancement. We find that the rotation of polarization plane in the nonlinear OFR depends on the intensity and relative phase of applied fields and can be controlled by these parameters. It is demonstrated that applying a microwave field to the system has a constructive role in enhancement of phase-controlled nonlinear OFR.
- (230.2240) Optical devices : Faraday effect
- (270.1670) Quantum optics : Coherent optical effects
- (270.4180) Quantum optics : Multiphoton processes
- (190.4223) Nonlinear optics : Nonlinear wave mixing
An insight into the eigenmodes of plasmonic nanoclusters based on the Green's tensor method
- received 10/07/2014; accepted 11/11/2014; posted 12/01/2014; Doc. ID 224508
- [full text: PDF (3986) KB)]
- Abstract: Assemblies of plasmonic nanoparticles possess exotic properties that are used in numerous applications. Their efficiency for specific applications strongly depends on the modes supported by the structure. In this paper, we extend the Green's tensor formalism to compute the eigenmodes of an assembly of plasmonic nanoparticles. Using the developed technique, we investigate the specific cases of a nanoparticle monomer, dimer and trimer. The influence of various geometrical parameters and of symmetry breaking on the eigenmodes of the assemblies is studied in detail, as well as the illumination conditions required to excite specific eigenmodes.
- (350.4238) Other areas of optics : Nanophotonics and photonic crystals
- (250.5403) Optoelectronics : Plasmonics
- (310.6628) Thin films : Subwavelength structures, nanostructures
Controlling ablation mechanisms in sapphire by tuning the temporal shape of fs-laser pulses
- received 08/12/2014; accepted 11/10/2014; posted 11/14/2014; Doc. ID 220848
- [full text: PDF (6781) KB)]
- Abstract: We have analyzed the influence of the temporal pulse shape on femtosecond laser-induced surface ablation processes in Sapphire. To this end, single transform-limited (TL), stretched (ST) and third-order-dispersion (TOD) shaped femtosecond pulses have been used, while the dynamics of the interaction was analyzed by fs-resolved microscopy and correlated with the plasma emission intensity and crater morphology. The modification of the pulse shape enables changing the ablation mechanism from a strong, thermally-mediated ablation process to a gentle ablation process mediated by Coulomb explosion (CE), with respective ablation depths of 100-200 nm and 5-10 nm. The analysis of the transient optical response allows a direct comparison of the transient plasma carrier densities involved, observing comparable peak values for both processes. While for strong ablation induced by TL-pulses, a direct relation between plasma density and local ablation depth is found, this does not hold for the CE-mediated process observed for TOD-shaped pulses. For TOD-shaped pulses at very high fluence, a different ablation mechanism involving explosive boiling is identified. This mechanism leads to the formation of deep craters with reduced lateral extension and steep walls. This amount of control over the ablation mechanisms by a simple selection of the pulse shape should be of interest for new surface structuring approaches.
- (140.3390) Lasers and laser optics : Laser materials processing
- (140.3440) Lasers and laser optics : Laser-induced breakdown
- (300.2140) Spectroscopy : Emission
- (320.5540) Ultrafast optics : Pulse shaping
- (320.7120) Ultrafast optics : Ultrafast phenomena
- (240.6648) Optics at surfaces : Surface dynamics
Measuring principal modes in a multimode optical fiber using the mode dependent signal delay method
- received 07/18/2014; accepted 11/03/2014; posted 11/04/2014; Doc. ID 216296
- [full text: PDF (551) KB)]
- Abstract: A method to determine principle modes in a multimode optical fifiber is described. This method is referred to as the mode dependent signal delay method and is an extension of the analogous method to determine principal states of polarization in a single mode optical fifiber. In the mode dependent signal delay, principal modes can be determined by measuring N²-1 mean signal time delays at the output of a multimode optical fifiber for N²-1 linear combinations of modes launched at the input of the optical fifiber. The derivation of principal modes as eigenstates to a mode dispersion operator is reviewed. It is shown the mode dispersion operator is Hermitian and can be expanded by the N²-1 generators of the Lie algebra of the Lie group SU(N) which leads to a corresponding mode dispersion vector in an N²-1 dimensional Stokes space. Finally, using these results, the mean signal time delay of a light pulse at the output of a multimode optical fifiber is derived from which the mode dependent signal delay method is described. The differences between the mode dependent signal delay method and the analogous method in a single mode optical fifiber are discussed.
- (030.4070) Coherence and statistical optics : Modes
- (060.0060) Fiber optics and optical communications : Fiber optics and optical communications
- (060.4230) Fiber optics and optical communications : Multiplexing
- (260.5430) Physical optics : Polarization
- (070.6120) Fourier optics and signal processing : Spatial light modulators
Cooperative plasmon-mediated effects and loss compensation by gain dyes near a metal nanoparticle
- received 08/13/2014; accepted 09/23/2014; posted 11/04/2014; Doc. ID 220628
- [full text: PDF (424) KB)]
- Abstract: We here present the first unified theory of the response of plasmonic nanoshells assisted by optical gain media, in the case of a nanoshell coated with a layer of optically active dipolar dyes. We obtain the optical coherent response of the core-shell aggregate in terms of its equivalent polarizability composed of the direct response from the nanoshell and the contribution raising from the cooperative coupling between dyes and surface plasmon of nanoshell. We identify mechanism of superradiance-like plasmonic aggregate emission similar to conventional Dicke effect with reduced intraband relaxation bandwidth due to the loss compensation in the system. The analysis of the aggregate resonances based on the system eigenvalues provides a physical insight into the total loss compensation mechanism and resonance frequency shifts.
- (160.4760) Materials : Optical properties
- (160.4236) Materials : Nanomaterials
- (250.5403) Optoelectronics : Plasmonics