Presentation Title

Improving the Limit of Detection for Biconically Tapered Fiber-Optic Sensors

Start Date

November 2016

End Date

November 2016

Location

HUB 265

Type of Presentation

Oral Talk

Abstract

Biconically tapered fiber-optic sensors (BTFS) have great potential to be powerful and cost efficient tools for detecting analytes, such as antigens, proteins, and DNA. Fabricated to assume a biconical shape, fiber-optic sensors act as interferometers in which mode coupling in the thin waist region of the sensor produces an interference spectrum. Each BTFS has an inherent limit of detection (LOD), upon which wavelength shifts due to changes in refractive index (RI) are indistinguishable from noise in the system. We hypothesize that using a single, much narrower laser peak to measure peak wavelength shift over time will result in a better LOD than using a wide peak associated with broadband light. This is because it is far easier to determine the center of a thin peak and, therefore, changes in wavelength can be more accurately determined. Including the taper as part of a laser loop, we find that lasing happens at one of the peak wavelengths present in the corresponding broadband spectrum and the rest of the peaks are suppressed, resulting in a spectrum that is dominated by a single peak. We experimentally confirmed that our lasing mechanism is stable to 0.2 pm. This means that we should be able to use our laser loop, with a BTFS included, to detect shifts in wavelength due to RI change to at least this much. We demonstrate more than an order of magnitude potential improvement in comparison with traditional broadband source based detection.

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Nov 12th, 3:45 PM Nov 12th, 4:00 PM

Improving the Limit of Detection for Biconically Tapered Fiber-Optic Sensors

HUB 265

Biconically tapered fiber-optic sensors (BTFS) have great potential to be powerful and cost efficient tools for detecting analytes, such as antigens, proteins, and DNA. Fabricated to assume a biconical shape, fiber-optic sensors act as interferometers in which mode coupling in the thin waist region of the sensor produces an interference spectrum. Each BTFS has an inherent limit of detection (LOD), upon which wavelength shifts due to changes in refractive index (RI) are indistinguishable from noise in the system. We hypothesize that using a single, much narrower laser peak to measure peak wavelength shift over time will result in a better LOD than using a wide peak associated with broadband light. This is because it is far easier to determine the center of a thin peak and, therefore, changes in wavelength can be more accurately determined. Including the taper as part of a laser loop, we find that lasing happens at one of the peak wavelengths present in the corresponding broadband spectrum and the rest of the peaks are suppressed, resulting in a spectrum that is dominated by a single peak. We experimentally confirmed that our lasing mechanism is stable to 0.2 pm. This means that we should be able to use our laser loop, with a BTFS included, to detect shifts in wavelength due to RI change to at least this much. We demonstrate more than an order of magnitude potential improvement in comparison with traditional broadband source based detection.