Publications by authors named "Christopher Smelser"

Localized hyperthermia therapy involves heating a small volume of tissue in order to kill cancerous cells selectively and with limited damage to healthy cells and surrounding tissue. However, these features are only achievable through real-time control of the tissue temperature and heated volume, both of which are difficult to obtain with current heating systems and techniques. This work introduces an optical fiber-based active heater that acts both as a miniature heat source and as a thermometer.

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The impact of sample orientation on the poling of single-sided multilayer silica structures is studied. The results show that the presence of a multilayer stack near the cathode creates a nonlinear region where it otherwise would not have formed. It is shown that field orientation impacts the location and magnitude of the induced nonlinearity.

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We present, for the first time to our knowledge, a dual strain/temperature sapphire fiber Bragg grating sensor. Temperature and strain coefficients of the grating are evaluated. By recording the blackbody radiation level above 650 degrees C, wavelength shifts due to temperature can be decoupled from those due to strain.

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Type I infrared ultrafast laser induced fiber Bragg gratings have been shown to exhibit higher-order resonances related to the Fourier components possessed by their nonsinusoidal index change profile. Using successive higher-order phase masks, we determine the Fourier components of type I-IR gratings in both hydrogen-loaded and unloaded fiber. Knowledge of the relative dc and ac components of a fiber Bragg grating is required for tailoring its spectral response.

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The formation of two grating types in SMF-28 fiber by focusing 125 fs, 0.5-2 mJ pulses through a phase mask onto a fiber sample is studied. The first type, specified as type I-IR, occurs below the damage threshold of the medium.

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The threshold for the fabrication of fiber Bragg gratings with ultrafast 800-nm radiation and a phase mask was studied in SMF-28 and all-silica core fiber by use of 125-fs pulses. High-pressure molecular hydrogen loading (H2 loading) was observed to significantly lower the grating writing threshold in standard Ge-doped telecommunication fiber. No reduction was observed with all-silica core fiber.

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Article Synopsis
  • The study compares cladding patterns in grating structures created using an ultrafast laser and a phase mask against a continuous wave (cw) beam interference model.
  • For picosecond pulses, the observed patterns align well with model predictions, but femtosecond pulses require consideration of full bandwidth and pulsed characteristics due to group-velocity walk-off effects.
  • An intriguing finding is that group-velocity walk-off allows for pure two-beam interference generation with a phase mask when using femtosecond pulses.
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High-quality retroreflecting fiber Bragg gratings were written in standard Ge-doped telecom fiber (Corning SMF-28) after a few minutes exposure with pulsed 800-nm, 120-fs laser radiation by use of a deep-etch silica zero-order nulled phase mask optimized for 800 nm. Induced index modulations of 1.9 x 10(-3) were achieved with peak power intensities of 1.

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