Plasma enhanced chemical vapor deposition of low loss as-grown germanosilicate layers for optical waveguides

We report on systematic growth and characterization of low-loss germanosilicate layers for use in optical waveguides. Plasma enhanced chemical vapor deposition (PECVD) technique was used to grow the films using silane, germane and nitrous oxide as precursor gases. Chemical composition was monitored by Fourier transform infrared (FTIR) spectroscopy. N-H bond concentration of the films decreased from 0.43 ×1022 cm -3 down to below 0.06x 1022 cm-3, by a factor of seven as the GeH4 flow rate increased from 0 to 70 seem. A simultaneous decrease of O-H related bonds was also observed by a factor of 10 in the same germane flow range. The measured TE loss rates at λ=632.8 nm were found to increase from are 0.20 ± 0.02 to 6.46 ± 0.04 dB/cm as the germane flow rate increased from 5 to 50 seem, respectively. In contrast, the propagation loss values for TE polarization at λ-1550 nm were found to decrease from 0.32 ± 0.03 down to 0.14 ± 0.06 dB/cm for the same samples leading to the lowest values reported so far in the literature, eliminating the need for high temperature annealing as is usually done for these materials to be used in waveguide devices

Low-loss as-grown germanosilicate layers for optical waveguides

We report on systematic growth and characterization of low-loss germanosilicate layers for use in optical waveguide technology. The films were deposited by plasma-enhanced chemical vapor deposition technique using silane, germane, and nitrous oxide as precursor gases. Fourier transform infrared spectroscopy was used to monitor the compositional properties of the samples. It was found that addition of germane leads to decreasing of N-H- and O-H-related bonds. The propagation loss values of the planar waveguides were correlated with the decrease in the hydrogen-related bonds of the as-deposited waveguides and resulted in very low values, eliminating the need for high-temperature annealing as is usually done

Stress effects in prism coupling measurements of thin polymer films

Due to the increasingly important role of some polymers in optical waveguide technologies, precise measurement of their optical properties has become important. Typically, prism coupling to slab waveguides made of materials of interest is used to measure the relevant optical parameters. However, such measurements are often complicated by the softness of the polymer films when stress is applied to the prism to couple light into the waveguides. In this work, we have investigated the optical properties of three different polymers, polystyrene (PS), polymethyl-methacrylate (PMMA), and benzocyclobutane (BCB). For the first time, the dependence of the refractive index, film thickness, and birefringence on applied stress in these thin polymer films was determined by means of the prism coupling technique. Both symmetric trapezoid shaped and right-angle prisms were used to couple the light into the waveguides. It was found that trapezoid shaped prism coupling gives better results in these thin polymer films. The refractive index of PMMA was found to be in the range of 1.4869 up to 1.4876 for both TE and TM polarizations under the applied force, which causes a small decrease in the film thickness of up to 0.06 mum. PMMA waveguide films were found not to be birefringent. In contrast, both BCB and PS films exhibit birefringence albeit of opposing signs

Elasto-Optical Properties of Thin Polymer Films by Prism Coupling Technique

39th International School of Quantum Electronics: Microresonators as Building Blocks for VLSI Photonics -- 18 October 2003 through 25 October 2003 -- -- 122694Reliable measurement of stress dependent refractive index of thin polymer films has been achieved. The effect of the applied stress on the refractive index and birefringence of the films was investigated. The out-of-plane elastic moduli of the thin polymer films were deduced by using the same prism coupling setup. Three dimensional finite element method (FEM) analysis was used to obtain the principal stresses for each polymer film and combining them with the stress dependent refractive index measurements, the elasto-optic coefficients of the polymer films were determined, for the first time. © 2004 American Institute of Physics

Visualising Invisible Networks as Collaborative Arts Practice

The use of thin polymer films in optical planar integrated optical circuits is rapidly increasing. Much interest, therefore, has been devoted to characterizing the optical and mechanical properties of thin polymer films. This study focuses on measuring the elasto-optical properties of three different polymers; polystyrene, polymethyl-methacrylate, and benzocyclobutane. The out-of-plane elastic modulus, refractive index, film thickness, and birefringence of thin polymer films were determined by means of the prism coupling technique. The effect of the applied stress on the refractive index and birefringence of the films was investigated. Three-dimensional finite element method analysis was used so as to obtain the principal stresses for each polymer system, and combining them with the stress dependent refractive index measurements, the elasto-optic coefficients of the polymer films were determined. It was found that the applied stress in the out-of-plane direction of the thin films investigated leads to negative elasto-optic coefficients, as observed for all the three thin polymer films. © 2004 American Institute of Physics

Population-Based Prevalence of Malaria Among Pregnant Women in Enugu State, Nigeria: the Healthy Beginning Initiative.

BACKGROUND: Malaria adversely affects pregnant women and their fetuses or neonates. Estimates of the malaria burden in pregnant women based on health facilities often do not present a true picture of the problem due to the low proportion of women delivering at these facilities in malaria-endemic regions. METHODS: Data for this study were obtained from the Healthy Beginning Initiative using community-based sampling. Self-identified pregnant women between the ages of 17-45 years were recruited from churches in Enugu State, Nigeria. Malaria parasitaemia was classified as high and low based on the malaria plus system. RESULTS: Of the 2069 pregnant women for whom malaria parasitaemia levels were recorded, over 99 % tested positive for malaria parasitaemia, 62 % showed low parasitaemia and 38 % high parasitaemia. After controlling for confounding variables, odds for high parasitaemia were lower among those who had more people in the household (for every one person increase in a household, OR = 0.94, 95 % CI 0.89-0.99). CONCLUSION: Results of this study are consistent with hospital-based estimates of malaria during pregnancy in southeastern Nigeria. Based on the high prevalence of malaria parasitaemia in this sample, education on best practices to prevent malaria during pregnancy, and resources in support of these practices are urgently needed.This item is part of the UA Faculty Publications collection. For more information this item or other items in the UA Campus Repository, contact the University of Arizona Libraries at [email protected]