We describe the applicability of photonic crystal fiber (PCF) with an enlarged effective area Aeff to a distributed Raman amplification (DRA) transmission. We investigate the DRA transmission performance numerically over a large Aeff PCF taking account of the signal-to-noise ratio (SNR) improvement RSNR in the S, C, and L bands. We show that an RSNR of 3 dB can be expected by utilizing DRA with a maximum pump power of 500 mW when the Aeff of the PCF is 230 µm2.

One-dimensional photonic crystal (PC) with alternating layers of TiO2 and SiO2 was fabricated with spin coating and low temperature baking, resulting in a successful tuning of the PC stop band so as to block the amplified spontaneous emission (ASE) of a π-conjugate polymer film. Single PC as a substrate, not a cavity with two PC's, of the polymer film was sufficient to shift the tangential ASE to the energy at PC stop band edge, indicating that the tangential ASE propagating along the interface was modulated by its evanescent-field tail in the PC, which opens the new pathway for low-threshold coherent luminescence from an ultrathin π-conjugate polymer film with ultimate mode volume.

Experimental and theoretical studies of light coupling to various magnetic nanostructured media and nanocomposites are briefly reported. Enhancement of the magneto-optical response is shown to occur when the constitutive materials of photonic crystals are magnetic. Transmission and reflection types of 1D magnetophotonic crystals (MPCs) have been studied. New possibility to enhance the magneto-optical response has been found when utilizing localized surface plasmon resonances in bismuth-substituted yttrium iron garnet (Bi:YIG) films impregnated with Au nanoparticles. Examples of integrated optic devices are discussed in which functional elements are 1D and 2D magnetophotonic crystals.

For the construction of photonic crystal fiber (PCF) systems using their unique properties, a PCF coupler (PCFC) is one of the key components of the systems. The characteristics of the PCFC depend on the state of air holes in the tapered region of the PCFC because the state of air holes in the tapered region affects light propagation in the PCFC taper. In this paper, coupling characteristics of PCFCs were theoretically investigated. In PCFCs with air hole remaining tapers, we found that a smaller elongation ratio i.e. a stronger elongation is required to obtain optical coupling as an air hole pitch or a ratio of air hole diameter to pitch is larger. In PCFCs with air hole collapsed tapers, it was clarified that a dependence of extinction ratio on air hole collapsed elongation ratio is higher for smaller elongation ratio. It was also clarified that an air hole remaining PCFC has slow wavelength characteristics in extinction ratio compared to an air hole collapsed PCFC. Air hole remaining PCFCs and air hole collapsed PCFCs were fabricated using a CO2 laser irradiation technique. We could successfully control whether air holes in the PCFC taper were remaining or collapsed by adjusting the irradiated laser power in the elongation process of the PCFC fabrication. It was experimentally clarified that the air hole remaining PCFC has slow wavelength characteristics in extinction ratio compared to the air hole collapsed PCFC. The tendencies of the measured wavelength characteristics of PCFCs agree with those of numerical results.

In this paper, we propose and demonstrate a novel type of PCF that has two cladding layers with Ge rods at the center core. We numerically show that it is possible to design a single mode PCF with large effective area greater than 200 µm2 over the whole wavelength above 1.2 µm. The proposed large mode area PCF (LMA-PCF) exhibits a high negative dispersion coefficient from -186 to -158 [ps/(nm-km)] in all wavelengths ranging from 1.2 µm to 1.8 µm. Effective single mode operation of LMA-PCF is confimed for the entire band of interest.

This paper describes near-zero ultra-flattened chromatic dispersion and low confinement loss that can be achieved from a decagonal photonic crystal fiber (D-PCF). The finite difference method with anisotropic perfectly matched boundary layer (PML) is used for the numerical analysis. It is demonstrated that it is possible to design a four-ring D-PCF with ultra-flattened dispersion of 0 0.69 ps/(nm-km) in a 1.30 to 1.75 µm wavelength range and 0 0.22 ps/(nm-km) in a 1.35 to 1.65 µm wavelength range with very low confinement losses of order 0.0011 dB/km. The proposed D-PCF shows promising dispersion tolerance.

We achieved the first 10 Gb/s WDM transmission at 1064 and 1550 nm over 24 km of photonic crystal fiber (PCF). We confirmed an improvement in the bit error rate (BER) performance after the transmission, namely "negative power penalties" of -0.5 and -0.3 dB at 1064 and 1550 nm, respectively. Our experimental result and theoretical estimation revealed that the signal degradation induced by the chromatic dispersion can be effectively suppressed by employing the pre-chirp technique with a conventional Z-cut lithium niobate (LN) modulator. We also show theoretically that we can expect to realize 10 Gb/s transmission over a 24 km PCF with negligible BER degradation in the 1060 to 1600 nm wavelength range by using the pre-chirp technique.

Basic microwave properties of magnetic photonic (MPC) and degenerate band edge (DBE) crystals are investigated mathematically and experimentally. Two dimensional and three dimensional models are considered demonstrating the very high sensitivity and field growth associated with these crystals. A major part of the paper deals with the development of realistic anisotropic periodic structures using a combination of layers constructed from thin film frequency selective surfaces, alumina, titanate and calcium vanadium garnet (CVG) materials. Measurements for antenna applications demonstrate and validate the theoretical performance of the MPC and DBE crystals. The latter part of the paper will present an exciting and promising development relating to microwave circuit applications. Specifically, a novel dual-line printed circuit is presented to emulate propagation in anisotropic media. As such, the MPC and DBE phenomena can be realized using very simple printed circuits (coupled lines). Lastly, physically small printed antennas and arrays based on the coupled transmission lines are presented.

This paper reports a novel design in Photonic Crystal Fibers (PCFs) with nearly zero ultra-flattened dispersion characteristics. We describe the chromatic dispersion controllability taking non-uniform air hole structures into consideration. Through optimizing non-uniform air hole structures, the ultra-flattened zero dispersion PCFs can be efficiently designed. We show numerically that the proposed non-uniform air cladding structures successfully archive flat dispersion characteristics as well as extremely low confinement losses. As an example, the proposed PCF with flattened dispersion of 0.27 ps/(nmkm) from 1.5 µm to 1.8 µm wavelength with confinement losses of less than 10-11 dB/m. Finally, we point out that full controllability of the chromatic dispersion and confinement losses, along with the fabrication technique, are the main advantages of the proposed PCF structure.

Autocloned photonic crystals have corrugated multilayer structure. By related process technology, we can easily fabricate an array of polarizers or waveplates. Patterned photonic crystals are versatile component of many optical systems. This paper focuses on their use in optical microscopy. The main topics are: 1. Use of polarization imaging in microscopy, 2. generation of radial/circular polarization by a polarizer having concentric corrugations, 3. a "longitudinal polarization slit" (a new component) and its function in confocal microscopy, and 4. a polarization converter for generating "z-polarized" light at the focal point. In every application above, autocloned photonic crystals play a central role.

The propagation characteristics of the leaky TE mode in a two-dimensional photonic crystal waveguide is analyzed using the Fourier series expansion method combined with the Chew's perfectly matched layer (PML). The complex propagation constant and mode field profiles are numerically tested in detail. It is shown that the leakage phenomena can be well modeled by choosing the PML parameters in proper range.

This study proposes a novel structure of index-guiding square photonic crystal fibers (SPCF) having simultaneously ultra-flattened chromatic dispersion characteristics and low confinement losses in a wide wavelength range. The finite difference method (FDM) with anisotropic perfectly matched layers (PMLs) is used to analyze the various properties of square PCF. The findings reveal that it is possible to design five-ring PCFs with a flattened negative chromatic dispersion of 0-1.5 ps/(nm.km) in a wavelength range of 1.27 µm to 1.7 µm and a flattened chromatic dispersion of 01.15 ps/(nm.km) in a wavelength range of 1.25 µm to 1.61 µm. Simultaneously it also exhibited that the confinement losses are less than 10-9 dB/m and 10-10 dB/m in the wavelength range of 1.25 µm to 1.7 µm.

We report on a channel drop filter with a mode gap in the propagating mode of a photonic crystal slab that was fabricated on silicon on an insulator wafer. The results, simulated with the 3-dimensional finite-difference time-domain and plane-wave methods, demonstrated that an index-guiding mode for the line defect waveguide of a photonic crystal slab has a band gap at wave vector k = 0.5 for a mainly TM-like light-wave. The mode gap works as a distributed Bragg grating reflector that propagates the light-wave through the line defect waveguide, and can be used as an optical filter. The filter bandwidth was varied from 1-8 nm with an r/a (r: hole radius, a: lattice constant) variation around the wavelength range of 1550-1600 nm. We fabricated a Bragg reflector with a photonic crystal line-defect waveguide and Si-channel waveguides and by measuring the transmittance spectrum found that the Bragg reflector caused abrupt dips in transmittance. These experimental results are consistent with the results of the theoretical analysis described above. Utilizing the Bragg reflector, we fabricated channel dropping filters with photonic crystal slabs connected between channel waveguides and demonstrated their transmittance characteristics. They were highly drop efficient, with a flat-top drop-out spectrum at a wavelength of 1.56 µm and a drop bandwidth of 5.8 nm. Results showed that an optical add-drop multiplexer with a 2-D photonic crystal will be available for application in WDM devices for photonic networks and for LSIs in the near future.

In this paper, we describe detailed experimental demonstrations of blue/violet light generation by the injection of ultrashort optical pulses into photonic crystal fibers (PCFs). Two lightwaves appear one on each side of the injected pulses in the spectral domain. They simultaneously evolve in the PCFs, changing their center wavelengths so as to spectrally stand apart from each other. Such behaviors are explained on the basis of the theory of nonlinear optics. The final center-wavelength difference between the two lightwaves at the end of the PCFs, depending on the power density of the injected pulse, is increased up to a limit imposed by the PCFs. Owing to this increase, the shorter wavelength limit reaches approximately 400 nm, which shows that short-pulse injection in PCFs is a promising method of realizing simple blue/violet light sources.

We have fabricated a polymer solid-state microstructure for optical application by two-photon-induced polymerization technique. The photopolymerization resin contains conventional laser-dye and dendrimer. A dendrimer can encapsulate the laser-dyes, limiting cluster formation and intermolecular energy transfer, and promising a high level of optical gain. The effect can be extended to prepare an optically active microstructure using the two-photon-induced polymerization technique. We fabricated a polymeric microcavity, which consisted of < 400 nm-linewidth strips arranged in layer-by-layer structure. The periodic variation in the refractive index gave rise to Bragg reflection. A laser emission was measured in the microcavity under optical excitation. The spectral linewidth was about 0.1 nm above the lasing threshold. We investigate both the material functions in the molecular scale and controlling the device structure for desired applications such as a polymer distributed feedback structure.

Photonic crystal waveguide switches with movable micro-electro-mechanical actuators are proposed and fabricated by silicon micromachining. The switch structure consists of in-line input and output photonic crystal waveguide slabs, and a switching slab to bridge the gap between the waveguides. By driving the switching slab with a micro electro-mechanical actuator, the transmission between the waveguides is modulated. For driving the slabs, two kinds of actuator, i.e., vertical and parallel motion actuators are proposed for the respective switches. The switching characteristics are also investigated by calculations using the finite-difference time-domain method.

In this paper, the confinement loss of octagonal photonic crystal fibers (PCFs) with an isosceles triangle lattice of air-holes are numerically investigated. Taking into account the confinement loss, the mode field diameter (MFD), the effective area (Aeff) and the chromatic dispersion of octagonal PCFs are calculated, compared to conventional hexagonal PCFs. It is found from confinement loss and MFD results that the octagonal PCFs can confine the field strongly than the hexagonal PCFs due to the different air filling fraction. Moreover, it is shown that the octagonal PCFs are obtained not only positive but also negative larger dispersion values and smaller Aeff values compared to the hexagonal PCFs.

Propagation characteristics of acoustic waves in photonic crystal fibers (PCFs) have been theoretically investigated in details. In order to evaluate acoustic band structures and guided modes for out-of-plane propagation in PCFs, analysis methods based on the finite element method are newly formulated. It is shown through numerical results that complete acoustic band-gaps (ABGs) exist in the cladding region of PCFs and that acoustic guided modes could be localized in the defect region of PCFs by the ABG effect. Furthermore, it is shown that acoustic guided modes could also be localized in the defect region of PCFs by the total internal reflection. These confinement mechanisms of acoustic waves propagating along the fiber length are completely different to those of lightwaves.

Press-induced long-period fiber gratings exhibiting strong core-to-cladding mode coupling were formed in photonic crystal fiber. Only one resonance peak was observed over a 600 nm spectral range and the resonant wavelength was tuned over the whole range by tilting a groove plate before pressing the fiber. The resonant wavelength decreased with increasing periodicity of the grating, which was opposite to the trend of the step-index conventional optical fiber. Meanwhile, the resonant wavelength increased with increasing the ambient refractive index, which was also opposite to that of the conventional optical fiber.

We report the empirically obtained conditions for the fusion splicing with photonic crystal fibers (PCF) having large mode areas. By controlling the arc-power and the arc-time of a conventional electric-arc fusion splicer, the splicing loss between two PCFs could be lowered down to 0.2 dB in average. For the splicing PCF with a conventional single mode fiber (SMF), the loss was increased due to the modal field mismatch, but still below 0.45 dB in average. The tensile strength was weakened by the splicing from 2.83 GPa down to 1.04 GPa for the PCF-PCF case and 0.89 GPa for the PCF-SMF one.