Overwrite fabrication and tuning of long period gratings

Date published

2016-09-19

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Optical Society of America: Open Access Journals / Optical Society of America (OSA)

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Article

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1094-4087

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Citation

Partridge M, James SW, Barrington J, Tatam RP. (2016) Overwrite fabrication and tuning of long period gratings, Optics Express, Volume 24, Issue 20, October 2016, pp. 22345-22356

Abstract

The central wavelengths of the resonance bands are critical aspect of the performance of long period gratings (LPGs) as sensors, particularly for devices designed to operate near the phase matching turning point (PMTP), where the sensitivity to measurements can vary rapidly. Generally, LPGs are characterized by their period, but the amplitude of the amplitude of the index modulation is also an important factor in determining the wavelengths of the resonance bands. Variations in fabrication between LPG sensors can increase or decrease the sensitivity of the LPG to strain, temperature or surrounding refractive index. Here, the technique of overwritten UV laser fabrication is demonstrated. It is shown that, on repeated overwriting, the resonance bands of an LPG exhibit significant wavelength shift, which can be monitored and which can be used to tune the resonance bands to the desired wavelengths. This technique is applied to periods in the range 100 to 200 µm, showing the cycle-to-cycle evolution of the resonance bands near the PMTPs of a number of cladding modes. The use of online monitoring is shown to reduce the resonance band sensor-to-sensor central wavelength variation from 10 nm to 3 nm.

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Github

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Attribution 4.0 International

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