Super Strong Wide TM Mie Bandgaps Tolerating Disorders

This study demonstrates the appearance of super intense and wide Mie bandgaps in metamaterials composed of germanium rods in air that tolerate some disordering of rod position and rod radius under transverse magnetic (TM) polarized light waves. Results for Mie bandgap modes TM01 and TM11 tolerate rod-position disordering of 50%, and rod-radius disordering of 34 and 20%, respectively. Using these characteristics of TM11 under position and radius disordering, ultra-narrow straight, L-shaped and crossing waveguides that contain 14, four, and two rows of Ge rods in air are designed. Also, it is shown that TE01 Mie bandgap appear in metamaterials contain high refractive index, and disappear in metamaterials with lower refractive index such as silicon; in contrast, a new phenomenon of intense and broadband TM01, TM11, and TM21 in metamaterials with lower refractive index such as silicon appear. Also, in Si-based metamaterials, TM01 tolerates high rod-position and rod-radius disordering of 50% and 34%, respectively, and TM11 shows robustness to rod-position and rod-radius of 20%. This strong tolerance of disordering of TM modes in silicon and germanium metamaterials opens a new way to design small, high-efficient, and easy-fabricable optical devices for optical integrated circuits.

Optical Power Splitter Based on Single Mode Directional Coupler Waveguide Using SnO2 Nanomaterial

Optical power splitter based on waveguide had been simulated numerically using Finite Difference Beam Propagation Method (FDBPM). Proposed waveguide was designed in the form of simple directional coupler waveguide. The waveguide was contained SnO2 nanomaterial as film or the guide part and the other supporting material as cladding with lower refractive index such as flint glasses. The waveguide used 2 μm of width to establish single-mode waveguide. The structure of waveguide is divided into three parts such as input, coupling and output part. While the waveguide was modified with angle in input and output parts to avoid coupling between waveguides. Furthermore, the proposed waveguide was analysed by varying the angle and coupling length. The analysed result shows that the waveguide has best performance in angle of 0.5 degrees and coupling length of 300 μm when the propagation loss was around 0.53%. Using the parameter, the output distribution percentage of waveguide approached 55%:44.5%. This performance indicated that the proposed waveguide can be used as optical power splitter. The application is very useful for optical telecommunication networking development.

Образование акцепторных центров в CdHgTe под воздействием воды и термообработок

Influence storage and boiling in deionized water and heat treatments of epitaxial films CdxHg1-xTe on the Hall and ellipsometric parametres is investigated. Water treatment reduces refractive index of native CdxHg1-xTe oxide from 2.1 to 1.2-1.4. It means that matter with a lower refractive index, such as water, is introduced in the oxide. Boiling in water leads to formation of acceptors in CdxHg1-xTe with concentrations up to 1019 cm-3. Change of medium’s pH from alkaline to the acidic decreases the speed of acceptors formation. Heat treatments after storage in water also leads to formation of acceptors. The conclusion is made, that water medium or water absorbed by native oxide layer leads to formation of acceptors in CdxHg1-xTe. Concentration of acceptors grows with temperature of treatments and quantity of accessible water.

The Modification of Optical Properties of the Surfaces by the Glancing Angle Deposition Technique

The paper considers the optical properties and structure of thin films of titanium dioxide formed by the glancing angle deposition method. It was show that this method allows the formation of coatings having a significantly lower refractive index than that of the initial material. Thus, the experimentally obtained value of the refractive index of thin films of titanium dioxide was ~1.2, which is almost two times less than that of a polycrystalline material. This allows you to use this method to produce the coatings with a variable refractive index using only one material, changing the geometry of the deposition process only.

Controlling Thermoplastic Elastomer Optical Properties by Mechanical Processing

ABSTRACTWe demonstrate that the extrusion speed of thermoplastic urethane elastomer can modify its optical transmission by a factor of more than 100. Varying extrusion speed at constant temperature may tune optical properties along the axis of a filament, for example creating absorbent regions that are sensitive to length and diameter changes, surrounded by more transmissive segments that carry the sensor signal over long distances. Such waveguiding in a stretchable optical fiber requires a stretchable cladding with lower refractive index than the core. In experiments toward a rugged, stretchable fiber cladding, we investigated whether solvents could modify the outer structure of the filaments. Soaking the filaments in NMP (n-methyl-2-pyrrolidone), then stretching the filaments while the solvent dried, turned out to modify the filaments in a way that solvents alone did not, creating porosity and reducing the appearance of optical clarity.

SiO2 and TiO2 Sol-Gel Blends with Tunable Optical and Electronic Properties

Sol-gel blends are created using a combination of a high refractive index (n∼2.4) TiO2 based sol-gel and a low refractive index (n∼1.5) SiO2 based sol-gel. The blends are prepared with different ratios of sol-gels and films are created using the spin coating method on silicon and ITO-on-glass substrates. The film thickness, refractive index, and dielectric constants of the resulting films are measured using profilometry, prism coupling, and LCR measurements, respectively. Results show that including more SiO2 based sol-gel in the initial mixture creates thicker films ranging from 1-7 μm, but results in lower refractive index and lower dielectric constants. This is consistent with expectations due to SiO2 having a lower refractive index and dielectric constant than titania over a range of wavelengths andfrequencies. The ability to fine tune the properties is explored.

Enhancement of Afterglow Luminescence of Long-Lasting Phosphor-Glass Composite by Using Refractive Index Matched Glass

Composites of a long-lasting phosphor, SrAl2O4:Eu,Dy, and glass were prepared by sintering the phosphor and glass powder. To enhance the afterglow luminescence, a borosilicate glass composition was chosen so that the refractive index of the glass matched that of the phosphor. Additional components with a high refractive index, such as La2O3 and Nb2O5, were added to the glass to increase the overall refractive index. As they tend to induce crystallization during sintering, small amounts of at least three types of such components were added to the glass to prevent crystallization. The surface of the composite was observed by a digital microscope with dark-field lighting. The phosphor particles became almost transparent because of the refractive-index matching, although bubbles were observed inside the phosphor particles. The afterglow luminance was, however, almost the same and the transmittance of the composite was not high because of many voids when compared to as that of the sample using the glass with a lower refractive index. The sample prepared under vacuum showed coloration and similar afterglow luminance even though the number of voids inside the composite decreased. To suppress the coloration, the amount of tin in the glass was increased, after which higher transparency and afterglow luminance were obtained. A 4-mm-thick sample showed a luminance of 118 mcd∙m-2 60 min after irradiation by a D65 lamp with 200 lx for 20 min.