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A configurable optical waveguide polarizer using graphene oxide (GO) as a polarizing element has been demonstrated. The propagation characteristics of the GO-coated optical waveguide are changed from TM-pass to TE-pass by controlling the GO coating thickness in the sub-micron range during the deposition process. The highest extinction ratio measured for a TM-pass waveguide polarizer is 34.9 dB, using a coating length and thickness of 1.0 mm and $0.34~\mu \text{m}$ respectively, while the highest extinction ratio measured for a TE-pass polarizer is 46.0 dB, using a coating length and thickness of 1.0 mm and $0.71~\mu \text{m}$ respectively. The polarization extinction ratio has also been measured across the wavelength range from 1520 nm to 1620 nm - and a variation of less than 3.0 dB was obtained. Control of the coating thickness dependent characteristics of the GO-coated waveguides provides an avenue for tailoring of the polarization selection. [ABSTRACT FROM AUTHOR]

In this paper, the photonic band-gap (PBG) maps of fundamental photonic crystal (PhC) lattices are presented, and discussed. Two fundamental types of lattice: square and hexagonal (triangular, graphite or honeycomb and kagome) with circular, square, and hexagonal hole shapes are considered. Because they show the largest area gap map and because of the relative ease of fabrication of circular holes, it can be asserted that square and triangular lattices of circular holes offer the best choice of two dimensionally periodic photonic crystal (PhC) structure. Graphite and kagome lattices of circular holes in GaAs also show large area gap maps (and the largest gap map is for the second or third higher PBG region). So graphite and kagome lattices are also relevant for exploitation in PhC devices. At the scale required, fabrication process limitations are a significant problem for the realization of hole shapes other than circular. [ABSTRACT FROM AUTHOR]

An array of GaN micropyramids containing a near-surface InxGa1-xN/GaN single quantum well has been fabricated using selective area epitaxial overgrowth above a patterned silica mask. The pyramid array has been studied by means of angle-resolved reflection measurements using s- and p-polarized incident light in the near- and mid-infrared optical ranges. We have found that the periodic array of flat-topped pyramids shows marked resonances in the near-infrared optical range due to resonant Bloch modes within the extraction cone and that the angular dispersion of these modes exhibits strong photonic crystal characteristics. The experimental results are in good agreement with the photonic band structure calculated using a scattering matrix formalism. The mid-infrared optical anisotropy properties of the micropyramids were investigated to probe the infrared active phonons of the pyramid array. The A1(LO) phonon of the InxGa1-xN/GaN single quantum well was identified and the InN mole fraction was estimated from the mode behavior. [ABSTRACT FROM AUTHOR]

Examines planar-optical waveguides fabricated by hydrogen isotopic exchange on lithium niobate with respect to their chemical and optical properties. Measurements of the effective indices of the guided optical modes; Determination of lithium in exchanged benzoic acid melts; Discussion of results.

Focuses on a study of gallium arsenide (GaAs) and aluminum GaAs quantum wells which are intermixed using silicon oxide capped rapid thermal annealing. Application of photoreflectance and photoluminescence in the study; Information on impurity-free vacancy diffusion; Experimental setup; Results.

Presents a study that characterized proton-exchange waveguides fabricated in lithium niobate. Methodology; Analysis of the hydroxide absorption bonds; Determination of the quasi-step-index waveguides.

Presents study which measured simultaneous depth profiles for hydrogen and lithium in proton-exchanged lithium niobate crystals. Experimental details; Results and discussion; Conclusion.

Presents a study which reported measurements of proton-exchanged lithium niobate (LiNnO[sub3]) using acoustic microscopy in the V(z) mode, together with optical waveguide mode observations. Characteristics of the LiNbO[sub3]; Review of work concerned with the acoustic properties of proton-exchanged insertion niobate; Materials and methods used; Variation of SAW velocity with azimuthal angle for all cuts of virgin and proton-exchanged lithium niobate.

Focuses on a study which dealt with the structural analysis of proton-exchanged lithium niobate optical waveguides fabricated in Z-, X-, and Y-cut substrates immersed in pure benzoic acid. Diffraction methodology through the Rutherford backscattering spectrometry; Measurement of mode structure and propagation losses of optical waveguides.

Reports on the strain and surface damage induced by proton exchange in Y-cut LiNbO[sub3]. Advantage of proton-exchanged waveguides; Way to avoid the surface damage in Y-cut substrates; Mechanism of surface damage generation after proton exchange in Y-cut LiNbO[sub3] substrates in pure benzoic acid.

Focuses on a study which described the observation of thermo-optic and photorefractive effects in an integrated optics spectrum analyzer. Occurrence of thermo-optic effect; Methodology of the study; Results and discussion.

Presents a study that determined the concentration of lithium ions in benzoic acid after proton exchange with lithium niobate. Methodology; Correlation between lithium ion molality and waveguide fabrication time; Determination of the effective diffusion coefficients.

Focuses on a study on time-resolved photoluminescence microscopy of GaInAs/GaInAsP quantum wells intermixed using a pulsed laser technique. Introduction to quantum wells and time-resolved photoluminescence; Use of photon-counting detector; Discussion on carrie recombination in quantum wells.

In-line single-mode tapered-fiber Mach–Zehnder interferometer (MZI-SMTF) with average waist diameters ( d\textrm {avg} ) of 4.05 and 2.89 \mu \textm have been fabricated, and both the temperature and the humidity sensitivity of the surrounding media have been measured and compared. The humidity and the temperature were measured over the ranges from 0% to 90% and 28 °C to 40 °C, respectively. The stability of the system at 50%RH and 90%RH was investigated, while the temperature of the chamber was maintained at about 28 °C. The humidity and temperature sensitivity resolution values were 0.02 nm/%RH and 0.05 nm/0.1 °C for the MZI-SMTF-1 with an average waist diameter of 4.05 \mu \textm , while they were 0.01 nm/%RH and 0.025 nm/0.1 °C for the MZI-SMTF-2 with an average waist diameter of 2.89 \mu \textm . [ABSTRACT FROM PUBLISHER]

The ability of thin polythiophene layers to dissipate accumulated charge in the electron beam lithography (EBL) of wide bandgap semiconductors, such as zinc oxide and gallium nitride, is demonstrated. A quick and inexpensive processing method is demonstrated for EBL exposure of dense and high-resolution patterns in a hydrogen silsesquioxane (HSQ) negative-tone resist deposited on bulk ZnO samples and with GaN/AlN on sapphire substrates. For the former, experimental results are given for three different cases: where no charge dissipation layer was used as well as cases where 40-nm-thick Al and 100-nm-thick conductive polymer layers were used on the top of the HSQ resist. For the latter material, EBL exposure was investigated for pure HSQ and for HSQ with a thin conductive polymer layer on top. Based on the scanning electron microscope observations of the resulting photonic crystal (PhC) pattern, conventional Al and the proposed polymer approach were compared. Good agreement between these results is reported, while the new method considerably simplifies sample processing. Spin-coatable conducting polymer may be easily removed due to its solubility in water, which makes it a perfect solution for the processing of amphoteric oxide samples, i.e., zinc oxide. Gallium nitride processing also benefits from polymer dissipation layer usage due to extended exposure range and the avoidance of dense pattern overexposure in HSQ. [ABSTRACT FROM AUTHOR]

Inductively coupled plasma dry etching for the fabrication of fine-pitch patterns in a wide range of InP-based materials has been developed. The effect of plasma chemistry (the N2 content in the total Cl2/Ar/N2 gas mixture) on the degree of undercut in the sidewall profile and surface morphology has been studied. Optimization of the etch process conditions produces strong passivation effects on the sidewalls, together with a highly anisotropic process, while still maintaining a good etch rate (560–730 nm/min). Single-step etching using hydrogen silsesquioxane as a resist/hard-mask resulted in high aspect ratio features being obtained (up to 30:1). Low plasma excitation power (inductively coupled plasma machine operating power of 400 W) and moderate ion energy (rf power of 120 W) were utilized to minimize etch-induced damage and provide low scattering losses. Low-loss (<0.3 dB/mm) optical ridge waveguides and high reflectivity and high-wavelength selectivity (Δλ=2 nm) results with 236 nm period sidewall gratings were demonstrated experimentally. [ABSTRACT FROM AUTHOR]

In this article the authors report on a new optical linewidth metrology method which uses measured changes in the resonant wavelength of fabricated ring resonator structures to establish the linewidth of waveguides. The technique has a precision of better than 0.5 nm for 500 nm linewidths and can be used for process control although it cannot be used with arbitrary optical structures. To demonstrate the technique they fabricated ring resonator structures on silicon on insulator substrates several times over a period of 70 days, using electron beam lithography with hydrogen silsesquioxane (HSQ) negative tone resist followed by dry etching. They show that waveguide width variations of less than 0.5 nm can consistently be achieved when the HSQ is diluted immediately prior to use but highly irreproducible results are soon obtained if a single dilution is prepared and used for an extended period. [ABSTRACT FROM AUTHOR]