High Dynamic Range Variable Optical Attenuation (Project Report CIAN2-1-Y5)

The goal of this project was to design silicon photonic components for optical WDM (wavelength division multiplexed) add/drop functionality in access and data networks. One of the key functionalities that was required by the campus networking testbed was to control the optical power levels in the WDM network of each channel without requiring separate components. This was most easily achieved by integrating the Variable Optical Attenuator (VOA) functionality together with the add-drop functionality on the same photonic chips.

On the Impact of Inclination-dependent Attenuation on Derived Star Formation Histories: Results from Disk Galaxies in the Great Observatories Origins Deep Survey Fields

We develop and implement an inclination-dependent attenuation prescription for spectral energy distribution (SED) fitting and study its impact on derived star formation histories. We apply our prescription within the SED fitting code Lightning to a clean sample of 82, z = 0.21–1.35 disk-dominated galaxies in the Great Observatories Origins Deep Survey North and South fields. To compare our inclination-dependent attenuation prescription with more traditional fitting prescriptions, we also fit the SEDs with the inclination-independent Calzetti et al. (2000) attenuation curve. From this comparison, we find that fits to a subset of 58, z < 0.7 galaxies in our sample, utilizing the Calzetti et al. (2000) prescription, recover similar trends with inclination as the inclination-dependent fits for the far-UV-band attenuation and recent star formation rates. However, we find a difference between prescriptions in the optical attenuation (A V ) that is strongly correlated with inclination (p‐value < 10−11). For more face-on galaxies, with i ≲ 50°, (edge-on, i ≈ 90°), the average derived A V is 0.31 ± 0.11 magnitudes lower (0.56 ± 0.16 magnitudes higher) for the inclination-dependent model compared to traditional methods. Further, the ratio of stellar masses between prescriptions also has a significant (p‐value < 10−2) trend with inclination. For i = 0°–65°, stellar masses are systematically consistent between fits, with log 10 ( M ⋆ inc / M ⋆ Calzetti ) = − 0.05 ± 0.03 dex and scatter of 0.11 dex. However, for i ≈ 80°–90°, the derived stellar masses are lower for the Calzetti et al. (2000) fits by an average factor of 0.17 ± 0.03 dex and scatter of 0.13 dex. Therefore, these results suggest that SED fitting assuming the Calzetti et al. (2000) attenuation law potentially underestimates stellar masses in highly inclined disk-dominated galaxies.

Methodology to Create Reproducible Validation/Reference Materials for Comparison of Filter-Based Measurements of Carbonaceous Aerosols That Measure BC, BrC, EC, OC, and TC

A simple method that reproducibly creates validation/reference materials for comparison of methods that measure the carbonaceous content of atmospheric particulate matter deposited on filter media at concentrations relevant to atmospheric levels has been developed and evaluated. Commonly used methods to determine the major carbonaceous components of particles collected on filters include optical attenuation for “Black” (BC) and “Brown” (BrC) carbon, thermal-optical analysis (TOA) for “Elemental” (EC) and “Organic” (OC) carbon, and total combustion for “Total” carbon (TC). The new method uses a commercial inkjet printer to deposit ink containing both organic and inorganic components onto filter substrates at programmable print densities (print levels, as specified by the printer–software combination). A variety of filter media were evaluated. The optical attenuation (ATN) of the deposited sample was determined at 880 nm and 370 nm. Reproducibility or precision (as standard deviation or in percent as coefficient of variation) in ATN for Teflon-coated glass-fiber, Teflon, and cellulose substrates was better than 5%. Reproducibility for other substrates was better than 15%. EC and OC measured on quartz-fiber filters (QFF) compared to ATN measured at 880 nm and 370 nm on either QFF or Teflon-coated glass-fiber yielded R2 > 0.92 and >0.97, respectively. Four independent laboratories participated in a round robin study together with the reference laboratory. The propagated standard deviation among the five groups across all print levels was <2.2 ATN at 880 nm and <2.7 ATN at 370 nm with a coefficient of variation of <2% at ~100 ATN.

Microphysics and Optical Attenuation in Fog: Observations from Two Coastal Sites

A total of 15 fog events from two field campaigns are investigated: the High Energy Laser in Fog (HELFOG) project (central California) and the Toward Improving Coastal Fog Prediction (C-FOG) project (Ferryland Newfoundland). Nearly identical sensors were used in both projects to sample fog droplet-size spectra, wind, turbulence, and thermodynamic properties near the surface. Concurrent measurements of visibility were made by the present weather detector in both experiments, with the addition of a two-ended transmissometer in the HELFOG campaign. The analyses focused first on contrasting the observed fog microphysics and the associated thermodynamics from fog events in the two locations. The optical attenuation by fog was investigated using three methods: (1) derived from Mie theory using the measured droplet-size distribution, (2) parametrized as a function of fog liquid water content, and (3) parametrized in terms of total fog droplet number concentration. The consistency of these methods was investigated. The HELFOG data result in an empirical relationship between the meteorological range and liquid water content. Validation of such relationship is problematic using the C-FOG data due to the presence of rain and other factors. The parametrization with droplet number concentration only does not provide a robust visibility calculation since it cannot represent the effects of droplet size on visibility. Finally, a preliminary analysis of the mixed fog/rain case is presented to illustrate the nature of the problem to promote future research.

Assessment of the preventive effects of Nd:YAG laser associated with fluoride on enamel caries using optical coherence tomography and FTIR spectroscopy

Objective This in vitro study characterized and monitored, by Optical Coherence Tomography (OCT) and Fourier Transformed Infrared Spectroscopy (FTIR), the effects of the association of acidulated phosphate fluoride gel (APF-gel) and Nd:YAG (neodymiun:yttrium-aluminum-garnet) laser, as sequencial treatments, in the prevention of incipient enamel caries lesions. Methods 120 human enamel samples were randomized into 3 groups (n = 40): APF-gel (1.23% F-, 4 min.); Laser+APF (Nd:YAG laser irradiation—0.6W, 84.9J/cm2, 10Hz, followed by APF-gel); and APF+Laser (APF-gel followed by laser irradiation). The samples were subjected to a 15-day pH-cycling, evaluated by OCT (quantification of optical attenuation coefficient–OAC) and FTIR (analysis of carbonate and phosphate content) before treatments, after treatments, and on the 5th, 10th and 15th days of pH-cycling. The statistical analysis was performed (α = 5%). Results The Optical Attenuation Coefficient (OAC) assessed by OCT increases with the progression of demineralization, and the Laser+APF presented the highest values of OAC in 10th and 15th days of pH-cycling. Nd:YAG decreased the carbonate content after treatment regardless of the application order of the APF-gel, while APF-gel did not interfere in the composition of enamel. The carbonate content was also changed in the first 5 days of the pH-cycling in all groups. Conclusion Nd:YAG laser irradiation before or after the application of APF-gel did not influence the appearance of incipient caries lesions, showing no synergistic effect. Regardless of the application order of the APF-gel, laser irradiation reduces the carbonate content of the enamel, which also changes during the demineralization process. However, irradiation before the application of APF-gel increased the speed of progression of the lesions, which positively impacts public health as it can prevent caries disease, even in high risk individuals. OCT and FTIR are suitable for assessing this effect.

Ultra-High Frequency Photoacoustic Microscopy: From Organelles to Organisms

This dissertation describes novel signal analysis and imaging techniques for ultrahigh frequency (UHF, over 100 MHz) Photoacoustic Microscopy (PAM). New approaches for extracting information pertaining to object structure and scale are described, and novel sensing techniques and contrast mechanisms for imaging biological samples ranging from single cells to small organisms are presented. In the first section, I describe a methodology for assessing the structure of biological cells using UHF-PAM. The power spectra of ultrasound (US) pulses backscattered from MCF-7 cells, and photoacoustic (PA) waves emitted from their dyed nuclei were fit to analytical solutions to determine cell and nucleus diameter, respectively. The measured cell diameters (15.5±1.8 μm) and nucleus diameters (12±1.3 μm) were used to calculate the mean cell nucleus-to-cytoplasm ratio (1.9±1.0). Good agreement was observed between UHF-PAM measured values and literature. In the second section, I present a novel technique for PA image reconstruction that utilizes unique features in the PA power spectra as a source of contrast. The technique, termed F-Mode, provides a means for differentiating between objects of different scale that surpasses the capabilities of conventional reconstruction approaches. The ability of F-Mode to selectively accentuate absorbers of different size was demonstrated using experimental phantoms containing microspheres and cylindrical vessels, as well as in individual biological cells and live zebrafish larvae. Finally, I developed a new sensing technique, termed Photoacoustic Radiometry (PAR). Unlike PAM, which depicts optical absorption, PAR images depict the optical attenuation properties of the imaged object. It was demonstrated that PAR can be used to image transparent samples which generate no PA signals, and that simultaneous triplex PAR/PA/US imaging could be realized using our approach. Simultaneous PAR/PA imaging of biological cells, as well as zebrafish larvae in vivo, was also demonstrated. UHF-PAM provided excellent visualization of vascular organization in the larval trunk and head. The simultaneously acquired PAR images depicted anatomical structure (e.g. the notochord, muscle segments) not visible in PAM due to insufficient optical absorption. Potential areas of application for the new UHF-PAM techniques described in this dissertation include detection of cancer cells in blood samples, and investigation of tumour growth and metastasis. (6 zipped .mp4 files) https://digital.library.ryerson.ca/islandora/object/RULA:8618/datastream/Movies_Moore_mp4/view