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Imaging and characterization of surface plasmon polaritons (SPPs) are crucial for the research and development of the plasmonic devices and circuits. Here, we report on direct imaging of SPPs propagation on SiO 2 /metal interface with subwavelength spatial resolution using up-conversion fluorescence microscopy, that exploits rare-earth ions, such as Er 3+ , Yb 3+ , and Nd 3+ , doped nanoparticles as the fluorophores. We demonstrated that by further taking the intensity ratio of the image obtained with fluorescent emission at different wavelengths, we are able to substantially enhance the features associated to the SPP wavefronts in the image for quantitative analysis, such as the wavevector and propagation direction of the SPPs. Our results agree with the theoretic prediction of the SPP wavelengths quantitatively. We further demonstrate the evolution of the SPP wavefronts due to refraction SPPs, and reproduced the experiment with finite difference time domain (FDTD) method simulations. The relative refractive index of SPP estimated from the experiment also agrees quantitatively with those extracted from the theory and the simulation.

The antiphase dynamics of Q-switched orthogonally polarized emissions have been thoroughly investigated. A Nd:YLF crystal with the anisotropic thermal lensing effect is used as the gain medium for achieving dual polarized laser. By using the Cr 4+ :YAG saturable absorber, the passively Q-switched output shows intriguing switching dynamics, where the number of pulses for both polarized components within one switching period is directly determined by the power ratio between the orthogonally polarized emissions. Experimental results reveal that the pulse energies of every single pulse for both orthogonally polarized states are equal with the maximum value of 223 μJ. The pulse durations for π- and σ-polarization are measured to be 15 ns and 11 ns and the corresponding peak power levels are up to 15.0 kW and 20.3 kW, respectively.

A novel encoder with dual displacement resolution is developed by integrating a multiple-grating-scale holographic displacement sensor and a heterodyne interferometer. With suitable arrangement of the measurement system, two effective grating pitches (0.41 μm and 10.62 μm) can be obtained and the theoretical sensitivities of them are 0.9 °/nm and 0.036 °/nm. Meanwhile, the best resolution of the proposed method can be estimated of 0.3 pm and 7.4 pm, respectively. Furthermore, displacement errors of the proposed method can be better than 0.2% for 1 mm displacement measurement. The experimental results showed that the proposed encoder provided high sensitivity, high resolution, and well against environmental disturbance.

This paper investigates the effects of ZnO nanoparticles (NPs) on the switching voltages of polymer dispersed liquid crystal (PDLC) films. The threshold and driving electric fields of PDLC film doped with 2.44 wt% ZnO NPs were 0.13 and 0.31 V/μm, respectively, with a contrast ratio of 26. The results of field emission scanning electron microscopy show that the size of the droplets in doped PDLC films increases with the doping concentration. The development of ZnO-doped PDLC films with low driving voltages greatly broadens the applicability of these devices.

An octave-spanning coherent supercontinuum is generated by non-collinear Raman-assisted four-wave mixing in single-crystal diamond using 7.7 fs laser pulses that have been chirped to about 420 fs in duration. The use of ultrabroad bandwidth pulses as input results in substantial overlap of the generated spectrum of the anti-Stokes sidebands, creating a phase-locked supercontinuum when all the sidebands are combined to overlap in time and space. The overall bandwidth of the generated supercontinuum is sufficient to support its compression to isolated few-to-single cycle attosecond transients. The significant spectral overlap of adjacent anti-Stokes sidebands allows the utilization of straight-forward spectral interferometry to test the relative phase coherence of the anti-Stokes outputs and is demonstrated here for two adjacent pairs of sidebands. The method can subsequently be employed to set the relative phase of the sidebands for pulse compression and for the synthesis of arbitrary field transients.

Guided mode resonance (GMR) enhanced second- and third-harmonic generation (SHG and THG) is demonstrated in an azo-polymer resonant waveguide grating (RWG), comprised of a poled azo-polymer layer on top of a textured SU8 substrate with a thin intervening layer of TiO2. Strong SHG and THG outputs are observed by matching either in-coming fundamental- or out-going harmonic-wavelength to the GMR wavelengths of the azo-polymer RWG. Without the azo-polymer coating, pure TiO2 RWGs, do not generate any detectable SHG using a fundamental beam peak intensity of 2 MW/cm(2). Without the textured TiO2 layer, a planar poled azo-polymer layer results in 3650 times less SHG than the full nonlinear RWG structure under identical excitation conditions. Rigorous coupled-wave analysis calculations confirm that this enhancement of the nonlinear conversion is due to strong local electric fields that are generated at the interfaces of the TiO2 and azo-polymer layers when the RWG is excited at resonant wavelengths associated with both SHG and THG conversion processes.

Guided-mode resonances enhanced excitation and extraction of two-photon photoluminescence (TPP) is demonstrated with a one-dimensional resonant waveguide grating (RWG) with a layer of fluorescent polymer (polyfluorene, PFO) on top. In this work, we design and fabricate a PFO RWG, in which two dispersive resonant modes in TE-polarization were measured. By aligning the red-shifting resonant mode with excitation wavelength in the infrared range, and the blue-shifting resonant mode with TPP spectrum in the visible range, the intensity of TPP can be enhanced up to 300-fold compared with that from a flat film with the same thickness coated on a glass slide. Such high enhancement results from firstly the strong evanescent local field in the waveguide layer due to the resonance between the incident light and the waveguide structure according to the results of rigorous coupled-wave analysis calculation, and secondly the enhanced extraction of the emission light which also resonates with the waveguide structure.

This work demonstrates the enhancement of light extraction of polymer light-emitting diodes (PLEDs) by incorporating a 12-fold photonic quasi crystal (PQC) in the device structure. Multi-exposure two-beam interference technique combined with inductively coupled plasma etching was employed to pattern a 12-fold PQC structure on the ITO film on a glass substrate of the diode. The air-hole coverage (AHC) and etching depth dependences of the light emitting performance of the 12-fold PQC patterned PLEDs were investigated. For AHC within the range between 6.4% and 32.3%, a nearly constant enhancement of the luminance efficiency of the PQC PLEDs was observed. On the other hand, the light emitting performance of the PQC PLEDs is very sensitive to the etching depth. The photoluminescence intensity of the PQC PLEDs increases monotonically with the etching depth. In contrast, the electro luminance efficiency shows a non-monotonic dependence on etching depth with a maximum occurring at 55 nm etching depth. The maximum improvement of luminance efficiency of the 12-fold PQC PLEDs reaches nearly 95% compared with an un-patterned PLED at an injection current of 110 mA.

This paper presents a heterodyne common-path grating interferometer with Littrow configuration (HCGIL). The HCGIL can effectively overcome environmental disturbance effect and the DC offset and the amplitude variation of the measurement signals. Experimental results match well with the HP5529A results for long-range measurements. Results also show that the estimated measurement resolution is 0.15 ± 0.027 nm. The stability of the HCGIL is -0.41 ± 0.23 nm. Therefore, the HCGIL has potential for subnanometer resolution and long-range applications.

This paper presents a convenient and reliable method to prepare gold nanoparticles (AuNPs) on graphene. Photo-assisted synthesis (PAS) was employed to grow AuNPs in AuCl(4)(-) electrolyte on graphene. The size of AuNPs could be as large as 130 nm. This optical method had a steady growth rate of AuNPs. The distribution of AuNPs was well controlled by focusing the laser for PAS. The minimum diameter of the distribution was approximately 1 μm. Surface-enhanced Raman scattering of graphene due to AuNPs was observed. Electrical fields near AuNPs calculated by the finite-difference time-domain algorithm ensured that the Raman enhancement was attributed to the localized surface plasmons of AuNPs.

We present a novel type of surface-enhanced Raman scattering (SERS) substrate constituted of a 3-dimensinal polymeric inverse opal (IO) photonic crystal frame with gold nanorods (Au-NRs) decorating on the top layer. This substrate employs resonant excitation as well as constructive backward scattering of Raman signals to produce large enhancement of SERS output. For the incoming excitation, Au-NRs with appropriate aspect ratio were adopted to align their longitudinal localized surface plasmon band with the excitation laser wavelength. For the outgoing SERS signal, the spectral position of the photonic band gap was tuned to reflect Raman-scattered light constructively. This SERS substrate produces not only strong but also uniform SERS output due to the well control of Au-NRs distribution by the periodic IO structure, readily suitable for sensing applications.

We analyze the non-uniform electric field distribution in an in-plane-switching blue phase liquid crystal (IPS-BPLC) cell and use the director model to simulate the electro-optical properties of an IPS-BPLC cell using a commercial simulator. The calculated results are in good agreement with the experimental data.

Volume holographic optical disc (VHOD) technology is simpler than the angular multiplexing holographic system. However, disc rotation usually causes pixel migration, thus reducing signal quality. This study proposes a special geometrical arrangement to counteract pixel migration. Using paraxial approximation analysis, an optimal geometrical distance ratio, K, is calculated to compensate for pixel migration and improve image quality during disc rotation. The results of approximation analysis are confirmed by both simulation and experimental results.

High quality opal photonic crystals (PhCs) were successfully fabricated by self-assembling of monodisperse Eu(3+)/SiO(2) core/shell nanospheres. Angular resolved photoluminescence (PL) spectra of a PhC sample were measured with different pumping powers, and its PL emission strongly depended on spectroscopic position of the photonic stop band and the optical pumping power. Suppression of the PL occurred in the directions where the emission lines aligned with the center of the photonic stop band. Suppression and enhancement of the PL were observed at low- and high-pumping powers, respectively, in the directions where the emission lines were located at the edges of the photonic stop band. When pumping power exceeded 6 µJ/pulse, a super-linear dependence was found between the pumping power and PL intensity. The dramatic enhancement of PL was attributed to the amplification of spontaneous emission resulted from the creation of large population inversion and the slow group velocity of the emitted light inside the PhC. The opal PhC provided highly angular-selective quasi-monochromatic PL output, which can be useful for a variety of optical applications.

Optical modulation of guided mode resonance (GMR) is demonstrated in a waveguide grating structure (WGS) which contains a disperse-red1 (DR1)-doped poly(methylmethacrylate) (PMMA) cladding layer. The resonance wavelength of a GMR mode can be tuned by pumping the cladding layer with a 442 nm wavelength laser beam, because of photoinduced refractive index change in the layer. The resonance wavelength shifts to shorter wavelength side, and the shift increases with pumping power, up to a maximum shift of 5 nm. A detector was used to monitor the intensity of the light that was reflected from the WGS at the wavelengths of the GMR peak positions, and the WGS was found to exhibit optical modulation with a shortest switching time of less than 0.3s.

The concentration and pH value of the immobilized glucose oxidase (GOD) are critical parameters in a glucose sensor. In this study, we develop a glucose fiber sensor integrated with heterodyne interferometry to measure the phase difference arising from the chemical reaction between glucose and GOD. Our studies show that the response time and resolution of this sensor will be strongly affected by the pH and concentration properties of GOD. In addition, the results show good linearity between the calibration curve for the glucose solution and serum based sample. The response time of this sensor can be shorter than 3 seconds and best resolutions are 0.1 and 0.136 mg/dl for glucose solution and serum based sample, respectively.

This work demonstrates the suppression of chaos in a Nd:YVO(4) laser by biharmonical pump modulation (the first for chaos-inducing and the second for chaos-suppressing). The laser exhibits chaotic behavior when only the first signal is applied for pump modulation and its frequency is adjusted close to the relaxation-oscillation frequency. Adding the second signal with subhamonic and a specific phase difference to the first modulation signal will reshape the modulated waveform of the pump beam to suppress the aforementioned chaotic behavior. The initial phase of the second harmonic perturbation plays an important role in the suppression of chaos. This result is confirmed by numerical simulation.

A single-layer of breath figure pattern was explored via the dynamical optical images and the temperature evolution. The pattern was prepared with the solution of carbon disulfide (CS(2)) dissolved 1% weight concentration of polystyrene. The evaporation of CS(2) was considered to be the most important role to the formation of the breath figure pattern. The understanding of the breath figures pattern will promote the technique to fabricating an imprinted template with demanded hexagonal structures.

A novel hybrid surface-enhanced Raman scattering (SERS) substrate based on Au nanoparticles decorated inverse opal (IO) photonic crystal (PhC) is presented. In addition to the enhancement contributed from Au nanoparticles, a desired Raman signal can be selectively further enhanced by appropriately overlapping the center of photonic bandgap of the IO PhC with the wavelength of the Raman signal. Furthermore, the lattice structure of the IO PhC provides excellent control of the distribution of Au nanoparticles to produce SERS spectra with high uniformity. The new design of SERS substrate provides extra maneuverability for ultra-high sensitivity sensor applications.

This work demonstrates a promising method to fabricate periodic nanovein structures, which can be served as templates for fabricating photonic crystals possessing a large complete photonic bandgap. First, the fabrication of a one-dimensional grating structure connected with nanolines is demonstrated by controlling the exposure dosage of the second exposure of the two-exposure two-beam interference technique. Secondly, by using the same interference technique but setting each exposure under the same exposure dosage, two-dimensional periodic structures with nanovein connections were fabricated. These structures were obtained by using either a pure negative photoresist with very low concentration of photoinitiator or a mixing of a negative and a positive photoresists. The fabricated structures are not, as usual, a duplication of the interference pattern but are constituted by square or triangular rods connecting with narrow veins. They can be used as templates for fabricating photonic crystals with very large complete photonic bandgap.

This work demonstrates the fabrication of a simple, low-cost microlens array (MLA) diffuser film with controllable haze distribution (diffusion effect) by a combination of "breath figures" (BFs) and micro-replica molding methods. Polystyrene (PS) molds obtained by BFs method contain concave, hexagonal packed air holes formed by the condensation of water vapor on cooling surfaces in a chamber in which relevant influence factors can be controlled. The sizes of the air holes in the BFs PS molds can be controlled by varying such factors as chamber temperature, chamber relative humidity, substrate temperature and others. The temperature distribution on the substrate affects the distribution of diameters of the air holes formed in a BFs PS mold. Convex PDMS (poly-dimethylsiloxane) MLAs were obtained by molding from the BFs PS molds. The focal lengths of MLAs were measured and compared with theoretical values. The diffusion effect of the diffuser films with MLAs of diameters 6 microm and 3 microm were compared. The results indicate that an MLA with a smaller diameter has a larger diffusion effect.

Nonlinear optical absorption of ZnO thin film grown by the laser molecular beam epitaxy was investigated by the Z-scan method using a frequency-doubled femtosecond Ti:sapphire laser. Due to near-exciton resonance, an enormous enhancement of two photon absorption (TPA) is about 3000 cm/GW at 390 nm which is about 6.5 times larger than the previously reported at two-photon exciton resonance in near-IR regime and 710 times larger than that of ZnO bulk measured at 532 nm. Besides, the free-carrier absorption resulting from linear absorption and TPA becomes essential when the excitation approaches the exciton resonance.

This work demonstrates that arbitrary types of spatially modulated second-order susceptibility (chi((2)) structures such as 1D and 2D, periodic and quasi-periodic structures can be obtained by using the combination of corona poling and direct laser writing (DLW) techniques. The fabrication technique is based on the photodepoling of azo-dye molecules caused by one-photon or two-photon absorption during the DLW process. Polarization and second harmonic generation (SHG) images of the fabricated structures were measured by electrostatic force microscope and SHG mapping techniques, respectively. Furthermore, quasi-phase-matched (QPM) enhanced SHG from a 1D periodically poled azo-copolymer planar waveguide is demonstrated using an optical parametric oscillator laser by scanning wavelength from 1500 to 1600 nm. The resonant wavelength of the QPM enhanced SHG is peaked at 1537 nm with FWHM is congruent to 2.5 nm.

We demonstrate theoretically and experimentally a useful technique for fabrication of two- and three-dimensional (2D or 3D) quasi-periodic structures by a double-exposure of a periodic interference pattern. With three-beam and three-beam-plus-one interference techniques, one can fabricate a periodic 2D and 3D structure having six-fold symmetry, respectively. When this structure is duplicated in another orientation, its combination results in a quasi-periodic twelve-fold symmetry structure. Experimental results obtained by using two-exposure of three-beam and/or three-beam-plus-one interference pattern at 442 nm into a positive photoresist (AZ-4620) proved the theoretical predictions. This study is potentially useful for photonic researches and applications.

A simple and efficient optical interference method for fabricating high quality two- and three-dimensional (2D and 3D) periodic structures is demonstrated. Employing multi-exposure of two-beam interference technique, different types of periodic structures are created depending on the number of exposure and the rotation angle of the sample for each exposure. Square and hexagonal 2D structures are fabricated by a multi-exposure of two-beam interference pattern with a rotation angle of 90 masculine and 60 masculine between two different exposures, respectively. Three-exposure, in particular, results in different kinds of 3D structures, with close lattice constants in transverse and longitudinal directions, which is difficult to be obtained by the commonly used multi-beam interference technique. The experimental results obtained with SU-8 photoresist are well in agreement with the theoretical predictions. Multi-exposure of two-beam interference technique should be very useful for fabrication of photonic crystals.