Optical Tamm plasmon (TP) can be excited at the boundary of photonic crystal and metal film. In this work, we propose a composite structure consisting of binary Au nanodisk arrays on the top of a distributed Bragg reflector (DBR) with 19.5 pair TiO2/SiO2 1D photonic crystal. The designed structure has strong confined mode at the boundary of DBR near to the binary Au nanodisk arrays, and the bandwidth of reflection spectrum is broadened obviously compared with that of the structure of Au film on the top of DBR. The conventional TP state at the boundary of nanodisks and DBR structure are modified while decreasing the size and period of binary Au nanodisk resulting from the collective lattice resonances supported by Au nanodisk. Two TP modes at 1100 nm and 1164 nm wavelength are found in reflection spectrum corresponding to different particle radii with 120 nm and 100 nm, and as the magnitude of particle radii in the two arrays approaches gradually, only one TP mode is found, which demonstrate the in-phase and anti-phase lattice resonances in different particle radii modified the confined field distribution of Tamm state at the boundary between Au nanodisk and DBR structure, generating a hybrid mode of TP and lattice resonance based on surface plasmon resonance. Coupling of TP mode and localized lattice resonance mode leads to the appearance of dual Tamm states with only one kind period DBR structure controlled by the radii of binary Au nanodisk array.
In this paper, we theoretically derive the local density of state (LDOS) in vacuum above a semi-infinite metamaterial. By using S-parameter retrieval methods, the obtained results of effective permittivity and permeability are employed to analyze the LDOS of metamaterial. It shows that p-polarization surface wave is the major contribution to near field radiation for electrical response, while s-polarization surface wave contributes most to near-field radiation for magnetic response. The study suggests a convenient way to control the enhanced near-field radiation.
Experimental studies of holographic thermal stability in phenanthrenequinone (PQ)-doped poly(methyl methacrylate-co-methacrylic acid) [P(MMA-co-MAA)] photopolymers are presented. A possibility to improve the thermal stability of holograms is demonstrated by doping methacrylic acid (MAA) into the poly(methyl methacrylate) (PMMA) polymer matrix. MAA as a copolymerization monomer can form a more stable polymer matrix with methyl methacrylate (MMA) monomer and increase average molecular weight of photoproducts, which finally depress the diffusion of photoproduct. The optimized MAA concentration copolymerized into P(MMA-co-MAA) polymer matrix can bring nearly a month's lifetime of gratings, which is obviously an improvement over the usual PQ-PMMA material under thermal treatment.
The angular selectivity was analyzed theoretically and numerically in the holographic storage system with the spherical
wave as reference beam. The results show that angular selectivity relates with the crystal thickness and independent on z0.
Experiments performed with Zn:Fe:LiNbO3 crystals also proved the prediction.
In this paper, the Goos-Hänchen shift on the interface between one regular isotropic medium and another anistotropic
LHM is analyzed extensively. The analytical expression of Goos-Hänchen shift on the uniaxially anisotropic LHM is
derived for the configuration where the optical axis of the LHM is perpendicular and parallel to the interface of two
media, respectively. Meanwhile, the expression of Goos-Hänchen shift on the surface of biaxially anisotropic LHM is
also presented. The result shows that the Goos-Hänchen shift on the surface of the anisotropic LHM is significantly
different from that of isotropic LHM. And under certain conditions, anomalous Goos-Hänchen shift shall occur, i.e., the
Goos-Hänchen shift is negative on the surface of the anisotropic LHM. The constraints for the existence of anomalous
Goos-Hänchen shift in anisotropic LHMs are identified, respectively.
An iterative method designed by angle multiplexing holographic storage is introduced to determine exposure schedule for multiplexing storage in Zn(2mol.%):Fe(0.03wt.%):LiNbO3 crystal. In this experiment, 60 holograms were recorded in the same location of the crystal with 2mJ/cm2 incident exposure energy per hologram (0.7s exposure time at 2.8mW/cm2 total incident intensity). And the self-correlation peaks of holograms were collected by CCD. We found that the cumulative grating strength of correlation peak versus exposure energy could be fitted to be a sixth-order polynomial, and made use of an iterative expression to calculate the exposure schedule for 60 holograms. The correlation recognition of 99 pictures with 16 levels gray is completed and the accuracy is 100%, while an appropriate exposure schedule is used to store the two-dimensional holograms.
Phenanthrenequinone-doped poly(methyl methacrylate) (PQ/PMMA) material is considered as one of the ideal optical memory polymer for its negligible volume shrinkage and optional shape. Samples were prepared by modifying the polymerization methods of PQ/PMMA materials in different temperatures and the diffraction efficiency of two-wave mixing was improved. During grating recording process, the maximal diffraction efficiency decreases with temperature increasing in the high-temperature-polymerized sample. For the low-temperature-polymerized sample, the maximal diffraction efficiency increases with temperature increasing at some ranges, and then decreases. Moreover, after the grating set-up, a thermal treatment process caused the diffraction efficiency of the low-temperature-polymerized sample to increase but to decrease for the high-temperature-polymerized sample. The diffusion equation was used to explain the interaction dynamics during the thermal treatment process.
Zn:Fe:LiNbO3 crystal has shorter response time and higher damage resistance ability than Fe:LiNbO3 crystal because of the doping of Zn ions, and the diffraction efficiency in Zn:Fe:LiNbO3 is comparable to that in Fe:LiNbO3 crystal. Transmission holographic recording geometry has been taken for its larger attainable dynamic range and sensitivity than that of the 90-degree geometry. Although there is relatively strong fanning effect in transmission geometry, Zn ions in the co-doped Zn:Fe:LiNbO3 crystal can restrain the fanning effect effectively. In our experiment, 60 holograms were angularly multiplexed and 72 spots were spatially multiplexed without hologram fixing technology, and the holograms can be stored more than ten days. A storage density of 4Gbits/cm3 has been obtained. The whole writing/reading process was accomplished automatically.
High resolution DWDM devices based on the principles of gratings (planar, Bragg, AWG, etc.) and Fabry-Perots (etalon, Lummer-Gehrke plate, etc.) suffer from inherent limitations due to (i) temporal pulse stretching of data, and (ii) broadening of time integrated spectral (demuxed) fringes. While the relation, dνFdt >1, can account for these limitations, our analysis imply that dnF does not represent real, physical frequencies. We explain the broader implications of this interpretation in designing DWDM devices based on gratings and Fabry-Perots and illustrate how to use prisms, photonic crystals and non-linear devices for very high data rate per channel.
In this paper we demonstrate the phase conjugate characteristics of a Tb:Cu:KNSBN crystal, using the self- pumped phase conjugator, the bridge double phase conjugator and the coherently induced double phase conjugator, respectively. The experimental results show that the Tb:Cu:KNSBN crystal has high 'cat' self-pumped phase conjugate reflectivity, which is 57 percent at incident angle of 40 degrees and input intensity of 7.6 W/cm2, and fast response. For the bridge double phase conjugator, two mutually incoherent e-polarized input beams enter the opposite crystal faces symmetrically with an included angle of 112 degrees. We measured the maximum phase conjugate transmissivity of 65 percent and the maximum phase conjugate reflectivity of higher than 250 percent. Moreover, we found that the temporal phase conjugate output varies with which input beam being blocked before the measurement. A peak reflectivity of as high as 300 percent was obtained when the beam ratio is 6.5. The Tb:Cu:KNSBN crystal has also been used to implement the coherently induced double phase conjugation and phase conjugate reflectivity approximately 320 has been obtained in a very large dynamic range of beam ratios.
A slant grating was recorded with two laser beams incident on photorefractive crystal asymmetrically. 2D perturbative analysis for the first two higher-order harmonics of the space-charge field for steady-state photorefractive slant grating recording has been presented. Considering the contribution from the next-order harmonic at arbitrary modulation depths. Numerical results for the first two harmonics show that the next-order correction to the space- charge field is strongly dependent on the modulation depths. The dependence of the harmonics on spatial frequency, modulation depth and grating slant angles is discussed.
In this paper, we took the hopping model to discuss the temporal variation of the fundamental harmonic of the space- charge field with external Sinusoidal field and square wave electric field, respectively. We presented the approximate analytical expression of the fundamental harmonic of the space-charge field versus time and the applied field amplitude. We also study the temporal variation of the real and the imaginary of the fundamental harmonic of the normalized space-charge field with different applied AC electric field, respectively. It is found that the real part of the fundamental space-charge field varies at the same frequency as the applied AC field, the imaginary part oscillates at twice the frequency. These results are in agreement with those derived from the band-transport model.
Ring self-pumped phase conjugator with high-speed modulated incident beam is studied theoretically and experimentally. The analytical solution for the stead-state output of the phase conjugate beam in a photorefractive crystal with an arbitrary complex coupling constant is given. The theory is verified by the experimental results using a Ce:KNSBN.
Analytical solutions for the equations that describe the steady-state photorefractive two-wave mixing with rapidly phase-modulated beams are presented. The results show that the volume index of refraction grating automatically aligns so that it coherently couples the signal and local oscillator fields just like a fixed beamsplitter in a conventional homodyne receiver structure.
With two extraordinary polarized beams incident on doped KNSBN crystals, higher diffraction orders have been observed when an external electric field is applied. At the same time, high-order anisotropic diffraction cones can also be observed on the viewing screen. These cones are originated from photorefractive four wave mixing which involves incident beams, high-order diffracted beams and forward scattered beams satisfying the phase matching condition. We also investigated the dependence of higher diffraction orders on incident angle.
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