Measured Propagation Loss Research Articles

Low loss optical channel waveguides for the infrared range using niobium based hybrid sol–gel material

In this work, we report the fabrication of single-mode Nb2O5 based hybrid sol–gel channel waveguides. Nb2O5 based hybrid sol–gel material has been deposited by spin-coating on silicon substrate and channel waveguides have been fabricated by a UV direct laser writing process. Optical guided modes have been observed to confirm single-mode conditions and optical propagation loss measurements have been performed using the cut-back technique. Optical propagation losses were measured to be 0.8dB/cm and 2.4dB/cm at 1.31μm and 1.55μm respectively. These experimental results demonstrate low loss optical waveguiding within the infrared range and are very promising in view of material choice for the development of integrated optical devices for telecommunication.

전자기파 부분방전 신호의 권선 투과 특성

Frequency domain measurement of propagation loss for ultra high frequency (UHF) partial discharge in the winding of power transformer using a spectrum analyzer and pulse generator is presented. We compared the performance of the method using a network analyzer with and without a winding. Using a network analyzer simplifies the measurement and offers better dynamic range and frequency range. It also provides precise propagation loss within the winding in frequency domain at UHF range. We applied this method to measure UHF propagation loss of transformer mock-up, modeled 154 kV 20 MVA power in KEPCO substation.

A parametric study of Er 3+-ions doped Phospho-tellurite glass thin films by pulsed laser deposition

Phospho-tellurite glass thin films have been deposited on silica substrates using an ArF laser ( λ = 193 nm, τ = 20 ns) at a laser fluence of 3.2 J/cm 2 and for various oxygen pressures, substrate temperatures and target-to-substrate distances. The measured propagation losses of the phospho-tellurite glass thin films are in the range of 0.13–0.75 dB/cm, whilst the refractive indices of the glass thin films were in the range of 1.623–1.649 which is very close to that of the target glass, showing nearly stoichiometric transfer of the material from target to substrate. The results show significant promise for integrated active optical device applications using pulsed laser deposition (PLD) of this erbium doped phospho-tellurite glass material.

Optical characterization of coupled resonator slow-light rib waveguides

We report on the design, fabrication and optical characterization of a slow light waveguide created using a linear array of coupled resonators in a large cross-section rib waveguide. Structures with as many as 25 high aspect ratio resonators are experimentally investigated. The measured propagation loss, group velocity, and delay-bandwidth product (DBP) are presented. The metric DBP/unit loss is also introduced, with a value 38/dB. Finally we discuss a method for further reducing loss in the slow-light rib waveguide.

Spectral characterization of porous dielectric subwavelength THz fibers fabricated using a microstructured molding technique

We report two novel fabrication techniques, as well as THz spectral transmission and propagation loss measurements of subwavelength plastic wires with highly porous (up to 86%) and non-porous transverse geometries. The two fabrication techniques we describe are based on the microstructured molding approach. In one technique the mold is made completely from silica by stacking and fusing silica capillaries to the bottom of a silica ampoule. The melted material is then poured into the silica mold to cast the microstructured preform. Another approach uses a microstructured mold made of a sacrificial plastic which is co-drawn with a cast preform. Material from the sacrificial mold is then dissolved after fi ber drawing. We also describe a novel THz-TDS setup with an easily adjustable optical path length, designed to perform cutback measurements using THz fibers of up to 50 cm in length. We fi nd that while both porous and non-porous subwavelength fibers of the same outside diameter have low propagation losses (alpha <or= 0.02 cm(-1)), the porous fi bers exhibit a much wider spectral transmission window and enable transmission at higher frequencies compared to the non-porous fibers. We then show that the typical bell-shaped transmission spectra of the subwavelengths fibers can be very well explained by the onset of material absorption loss at higher frequencies, due to strong confinement of the modal fields in the material region of the fi ber, as well as strong coupling loss at lower frequencies, due to mismatch between the modal field diameter and the size of the gaussian-like beam of a THz source.

Direct measurement of propagation losses in silver nanowires

We demonstrate a simple, direct measurement of propagation losses in single silver nanowires. Using a waveguiding nanoscale fiber taper for highly efficient launching, propagation surface plasmon polaritons are excited in the silver nanowire with high efficiency. The output intensity as light radiation at the end of the nanowire is quantified with high accuracy and repeatability. A typical propagation loss of 0.41 dB radicalmum (for 633 nm light) in a 260 nm diameter silver nanowire is obtained, which suggests that the propagation loss of a single silver nanowire could be lower than previously reported experimental results and should be much lower than those obtained by theoretical calculations.

ZnO Channel Waveguides for Nonlinear Optical Applications

ZnO channel waveguides were fabricated for the first time, for the purpose of being used in nonlinear optical applications. Wide-bandgap ZnO was chosen for the core material to avoid two-photon absorption at wavelengths above 800 nm which are used for biomedical applications. We calculated the single-mode conditions and group-velocity dispersion of the propagating modes for the waveguides. We also fabricated channel waveguides using single-crystal ZnO thin film grown on sapphire substrate. Measured propagation losses with a cut-back method were approximately 3 to 6 dB/mm for single-mode waveguides.

Low-loss optical waveguides for the near ultra-violet and visible spectral regions with Al 2O 3 thin films from atomic layer deposition

In this work, we report low-loss single-mode integrated optical waveguides in the near ultra-violet and visible spectral regions with aluminum oxide (Al 2O 3) films using an atomic layer deposition (ALD) process. Alumina films were deposited on glass and fused silica substrates by the ALD process at substrate/chamber temperatures of 200 °C and 300 °C. Transmission spectra and waveguide measurements were performed in our alumina films with thicknesses in the range of 210–380 nm for the optical characterization. Those measurements allowed us to determine the optical constants ( n w and k w), propagation loss, and thickness of the alumina films. The experimental results from the applied techniques show good agreement and demonstrate a low-loss optical waveguide. Our alumina thin-film waveguides are well transparent in the whole visible spectral region and also in an important region of the UV; the measured propagation loss is below 4 dB/cm down to a wavelength as short as 250 nm. The low propagation loss of these alumina guiding films, in particular in the near ultra-violet region which lacks materials with high optical performance, is extremely useful for several integrated optic applications.

Enhanced electro-optic phase shifts in suspended waveguides

We demonstrate enhanced electro-optic phase shifts in suspended InGaAs/InGaAsP quantum well waveguides compared to attached waveguides. The enhancement stems from an improved overlap between the optical mode and the multiple quantum well layers in thin waveguides when the semiconductor material beneath the waveguide is selectively etched. The measured voltage length product is 0.41 V-cm and the measured propagation loss is 2.3 +/- 0.7 dB/cm for the TE mode in the optical L-band.

Experimental Demonstration of Deeply-Etched SiO$_{2}$ Ridge Optical Waveguides and Devices

Deeply-etched SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> optical ridge waveguides are fabricated and characterized. A detailed discussion of the fabrication process (especially for the deep etching process) is presented. The measured propagation losses for the fabricated waveguides with different core widths range from 0.33 ~ 0.81 dB/mm. The loss is mainly caused by the scattering due to the sidewall roughness. The losses in bending sections are also characterized, which show the possibility of realizing a small bending radius (several tens of microns). 1 × N (N = 2, 4, 8) multimode interference couplers based on the deeply-etched SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ridge waveguide are also fabricated and show fairly good performances.

A new simple method of fabricating micro/nano-scale polymer optical wires on a copper plate

We developed a novel and simple method of fabricating micro/nano-scale polymer optical wires on a copper plate. We first wet-etch the copper surface to form micro-channels, which are then coated with polymer cladding material and filled with polymer core material to form optical wires. The cladding layer not only helps improve the smoothness of the inner surfaces of the etched micro-channels, but also prevent light absorption and scattering loss caused by surface roughness of the etched channels. The measured propagation loss of the fabricated polymer wire was −0.3 dB/cm by cut-back method. This opens up new possibilities for integration of optical wires and electrical circuits on planar platforms such as electrical printed circuit boards (PCBs).

Measurement of Absorption Coefficient of Carbon-Doped GaAs

The optical absorption coefficients of carbon-doped GaAs in a wide range of doping concentrations (1018 to 1020 cm-3) were measured by waveguide propagation loss and wafer measurements. Experimental data indicate twofold higher absorption coefficients for C-doped GaAs than for Zn-doped GaAs at a wavelength of 1300 nm.

Role of nanostructure on the optical waveguiding properties of epitaxial LiNbO3 films

High-quality LiNbO3 (LN) epitaxial films have been grown on (0 0 1)Al2O3 substrates by pulsed laser deposition. The deposition conditions have been optimized using experimental designs to promote the growth of highly (0 0 1)-oriented, phase pure and light-guiding LN films. The structural and nanostructural properties have been investigated by x-ray diffraction reciprocal space mapping and the guiding properties have been investigated by m-line spectroscopy and measurements of the light propagation losses. In particular it is shown that the film composition, the state of strain, the film thickness, the film roughness, the lateral extension of the crystallites building up the film as well as the mosaicity can be determined by a careful examination of the x-ray reciprocal space maps associated with simulation of the diffracted intensity distribution in reciprocal space. The guiding properties have been correlated with the nanostructural properties of the films: whereas light guiding has been clearly observed in single-crystal-like films, the existence of a mosaic structure, made of nanocrystalline domains, is shown to be detrimental to the guiding properties.

Fabrication of an optical polymer waveguide by plasma‐enhanced polymerization

AbstractWe have fabricated an optical polymer waveguide using plasm‐enhanced polymerization. C6H6 and C6H10 are used as monomer materials for depositing core and cladding layer, respectively, because the refractive index of polymerized layers is known to dominantly depend on the ratio of sp2 and sp3 bond in those. By decreasing RF power below 0.04W/cm2, dangling bonds formed in a polymer film will be suppressed, so that a relatively low‐loss waveguide has been fabricated. We measured propagation loss of those waveguides using the end‐fire method employing laser light at a wavelength of 787 nm. The losses are 3.2cm−1 for the samples plasma‐polymerized in Ar. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(4): 21–28, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10084

Low-loss amorphous silicon-on-insulator technology for photonic integrated circuitry

We report the fabrication of low-loss amorphous silicon photonic wires deposited by plasma enhanced chemical vapor deposition. Single mode photonic wires were fabricated by 193nm optical lithography and dry etching. Propagation loss measurements show a loss of 3.46dB/cm for photonic wires (480×220nm) and 1.34dB/cm for ridge waveguides.

Optical characteristics of nanocrystallized glass fiber with second-order optical nonlinearity

Second harmonic generation (SHG) and propagation loss have been measured on nanocrystallized optical fibers of tellurite-based glass, 15K2O·15Nb2O5·70TeO2. The result of the angular dependence of the SHG intensity is discussed based on the difference in the transmission factor varying with the polarization direction. Propagation-loss measurements on the fiber samples by a cut-back method showed low loss compared with that of a typical LiNbO3 waveguide.

Silicon optical Fiber

Described herein are initial experimental details and properties of a silicon core, silica glass-clad optical fiber fabricated using conventional optical fiber draw methods. Such semiconductor core fibers have potential to greatly influence the fields of nonlinear fiber optics, infrared and THz power delivery. More specifically, x-ray diffraction and Raman spectroscopy showed the core to be highly crystalline silicon. The measured propagation losses were 4.3 dB/m at 2.936 microm, which likely are caused by either microcracks in the core arising from the large thermal expansion mismatch with the cladding or to SiO(2) precipitates formed from oxygen dissolved in the silicon melt. Suggestions for enhancing the performance of these semiconductor core fibers are provided. Here we show that lengths of an optical fiber containing a highly crystalline semiconducting core can be produced using scalable fiber fabrication techniques.

Low-loss propagation in Cr^4+:YAG double-clad crystal fiber fabricated by sapphire tube assisted CDLHPG technique

Cr4+:YAG double-clad crystal fiber with an uniform 10-microm core was fabricated by using a sapphire tube as a heat capacitor to stabilize the power fluctuation of the CO2 laser in the co-drawing laser-heated pedestal growth system. The uniformity of the fiber core showed a factor of 3 improvement compared to that without the use of sapphire tube. The variation of the core diameter is within the +/-1.35-degree adiabatic criterion and has a autocorrelation length of 1.7 mm. The measured propagation loss is only 0.02 dB/cm. The sapphire tube also reduces the vertical temperature gradient during the crystal fiber growth process so the 10-microm crystal core exhibits a smooth perimeter. The sapphire tube assisted system can be applied to the growth of many other optical crystal materials.

Seafloor studies at NURC/SACLANTCEN: The first 50 years (1959-2008)

Characterization of the seafloor has always been one of the central research themes at NURC/SACLANTCEN. These studies, reviewed in this presentation, generally supported acoustic measurement and modeling programs. Motivation for bottom-interacting acoustic research began with the deep-water ASW programs of the 1960s and 1970s (long-range propagation, reflection, and bottom loss measurements) and slowly evolved into support for high-frequency, shallow-water MCM programs of the 1990s and 2000s (acoustic propagation within sediments, penetration into and scattering from the sediment surface). Seafloor characterization has included scales appropriate for plate tectonics to sub-mm scale sediment microstructure used to statistically characterize sediment heterogeneity for high-frequency acoustic studies. Although collection and analysis of sediment cores has been the dominate methods of seafloor characterization, direct in situ measurements and remote acoustic characterization has often been used. Seafloor studies were first rate, cutting edge research as demonstrated by quality and quantity of peer-reviewed publications by NURC/SACLANTCEN scientists and their post-SACLANTCEN research careers. The excellent engineering department made possible the development of unique acoustic and seafloor sampling equipment. Ship support for seafloor studies has always been a NURC/SACLANTCEN advantage that has attracted many scientists to multi-national, multi-institutional experiments and symposia.

Gamma-ray irradiated polymer optical waveguides

Optical waveguides fabricated by gamma-ray irradiation on polymer through a gold mask are presented. The gamma-ray induced index change is found almost linearly dependent on the dose of the irradiation. And the measured propagation losses are low enough for practical application. Due to the high penetrability of gamma ray, uniform refractive index change in depth can be easily achieved. Moreover, due to large-area printing, the uniformity of waveguide made by gamma-ray irradiation is much better than that by e-beam direct writing.