| 1. |
- Cui, Y., et al.
(författare)
-
Transmission enhancement of a metallic slit by a nearby metallic nano-particle
- 2008
-
Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE.
-
Konferensbidrag (refereegranskat)abstract
- We propose to use a nearby metallic nano-particle to greatly enhance the transmission efficiency of a nano-slit aperture in a metallic film. The metallic nano-particle helps to form a T shape cavity which could effectively transform the propagating incident light into localized near-filed light. Harvest efficiency is enhanced by 20 times for a non-resonant 25 nm-width nano-slit.
|
|
| 2. |
- Dai, Daoxin, et al.
(författare)
-
Compact silicon-on-insulator-based multimode interference coupler with bilevel taper structures
- 2005
-
Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 44:24, s. 5036-5041
-
Tidskriftsartikel (refereegranskat)abstract
- A novel compact silicon-on-insulator- (SOI-)based multimode interference (MMI) coupler with bilevel taper structures was designed. The MMI section and the S-bend sections of the input-output waveguides are deeply etched. The input-output waveguides connecting to single-mode fibers or other photonic light circuits are etched shallowly to yield single-mode operation. A bilevel taper is introduced in the transition region between the shallowly and deeply etched regions. It is predicted theoretically that this design will not only improve the quality of the self-imaging in the MMI section but will also make the structure compact. Both the excess loss and the nonuniformity of the MMI coupler are reduced. By use of a three-dimensional beam propagation method, the performance of a 1 × 4 MMI coupler based on a SOI is simulated as a numerical example of the novel design. The simulated nonuniformity and the excess loss are approximately 0.0285 and 0.2 dB, respectively.
|
|
| 3. |
- Dai, Daoxin, et al.
(författare)
-
Elimination of multimode effects in a silicon-on-insulator etched diffraction grating demultiplexer with bi-level taper structure
- 2005
-
Ingår i: IEEE Journal of Selected Topics in Quantum Electronics. - 1077-260X .- 1558-4542. ; 11:2, s. 439-443
-
Tidskriftsartikel (refereegranskat)abstract
- Multimode effects in the free propagation region (FPR) of an etched diffraction grating (EDG) demultiplexer based on silicon-on-insulator are analyzed. The insertion loss and the crosstalk increase due to these undesired multimode effects. A bi-level taper structure between the FPR and the input/output waveguides is proposed. It is shown that such a taper structure can reduce the multimode effects to an almost negligible level. At the same time, the 3-dB passband width is enlarged by increasing the rib width. No additional fabrication process is needed for an EDG with such a design.
|
|
| 4. |
- He, Guang S., et al.
(författare)
-
Dynamic properties and optical phase conjugation of two-photon pumped ultrashort blue stimulated emission in a chromophore solution
- 2008
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 77:1
-
Tidskriftsartikel (refereegranskat)abstract
- The dynamic properties of two-photon pumped blue lasing (similar to 470 nm) in the solution of an organic chromophore [2-acetyl-6-(dimethylamino)naphthalene], excited by similar to 160-fs laser pulses at similar to 775 nm, have been studied. Both the forward and backward stimulated emission are enhanced by feedback from the reflection at the two optical windows of the solution filled cuvette. Under current experimental conditions, the lasing wavelengths in the forward and backward directions were almost the same, but both blueshifted compared to the fluorescence peak wavelength of the sample solution. The temporal behavior of the lasing output was recorded by a high-speed streak camera system. The multipulse structure and spectral properties of the output lasing are semiquantitatively explained. In addition, excellent optical phase-conjugation properties of the backward stimulated emission were observed; the aberration influences from an aberrator on the backward lasing beam were automatically removed.
|
|
| 5. |
- He, G. S., et al.
(författare)
-
Multifocus Structures of Ultrashort Self-Focusing Laser Beam Observed in a Three-Photon Fluorescent Medium
- 2009
-
Ingår i: IEEE Journal of Quantum Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9197 .- 1558-1713. ; 45:7, s. 816-824
-
Tidskriftsartikel (refereegranskat)abstract
- Self-focusing effect and multifocus structures of an ultrashort (similar to 160-fs) pulsed laser beam of similar to 1.3-mu m wavelength are investigated in several organic liquids. The intensity-dependent self-focusing formation and multifocus structures of the infrared (IR) laser beam were directly observed in a three-photon active fluorescent dye solution cell, in which a high contrast image of the spatial structure of the self-focusing beam can be obtained due to the cubic dependence of the fluorescence intensity on the local IR laser intensity. By combining this dye solution cell with another cell filled with various transparent organic liquids, the contributions of these tested liquids to the observed self-focusing effect are elucidated. The numerical simulations for this type of self-focusing behavior are presented, based on the assumption that the major contribution to the observed self-focusing is the nonlinear refractive-index change of the solvent due to electronic-cloud distortion. The simulation results are in fairly good agreement with the experimental results.
|
|
| 6. |
- He, G. S., et al.
(författare)
-
Stimulated Rayleigh-Bragg Scattering From a Two-Photon Absorbing CdSe-CdS-ZnS Quantum-Rods System : Optical Power Limiting and Phase-Conjugation
- 2008
-
Ingår i: IEEE Journal of Quantum Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9197 .- 1558-1713. ; 44:9-10, s. 894-901
-
Tidskriftsartikel (refereegranskat)abstract
- This work reports the properties of stimulated Rayleigh-Bragg scattering (SRBS) from a two-photon absorbing CdSe-Cds-ZnS quantum-rods (QRs) solution in chloroform, excited by 1064-nm and similar to 13-ns laser pulses. The two-photon absorbing capability of the scattering medium, as well as the pump threshold, spectral structure, and pulse waveforms of the backward stimulated scattering were measured. Comparing to a pure solvent or an organic dye-solution, the semiconductor QR system has many advantages such as the lower pump threshold, higher energy transfer efficiency, and better photo-physical and photo-chemical stability. The measured output/input characteristic curve shows that the backward SRBS can enhance the optical power limiting performance that is based on two-photon absorption, backward stimulated scattering, and other nonlinear absorption mechanisms. In addition, the backward SRBS beam from our sample medium exhibits a fairly good optical phase-conjugation capability, so that the distortion influence from an inserted aberrator can be automatically removed.
|
|
| 7. |
|
|
| 8. |
- He, J. L., et al.
(författare)
-
Slow light in a dielectric waveguide with negative-refractive-index photonic crystal cladding
- 2008
-
Ingår i: Optics Express. - 1094-4087. ; 16:15, s. 11077-11082
-
Tidskriftsartikel (refereegranskat)abstract
- A slow light waveguide made of a dielectric slab inserted in a two-dimensional photonic crystal with a negative effective refractive index is proposed and numerically studied. The waveguide may possess modes with zero group velocity, and its frequency varies with the thickness of the waveguide. A linearly tapered left-handed photonic crystal waveguide is also proposed and studied. It is shown that the so-called 'trapped rainbow' proposed by Tsakmakidis, Boardman, and Hess [1] is difficult to realize due to a coupling of forward- and backward-propagating modes near zero group velocity. However, different frequency components of a broadband excitation can still be separated through partial accumulation at waveguide sections of different thicknesses.
|
|
| 9. |
|
|
| 10. |
- He, Sailing, et al.
(författare)
-
Abnormal guiding and filtering properties for some composite structures of right/left-handed metamaterials
- 2005
-
Ingår i: Asia-Pacific Microwave Conference Proceedings, APMC. - 078039433X
-
Konferensbidrag (refereegranskat)abstract
- We study some abnormal guiding and filtering properties for some multi-layered structures consisting of right/left-handed metamaterials. The extremely slow propagation of guided waves in a slab waveguide with a left-handed material substrate is studied. Resonating and notch filters based on some composite right/left-handed (CRLH) transmission lines are also proposed.
|
|
