Characterizing germania concentration and structure in fiber soot using multiphoton microscopy and spectroscopy technology

Minghan Chen; Ming-Jun Li; Anping Liu

doi:10.1117/12.2077731

27 February 2015 Characterizing germania concentration and structure in fiber soot using multiphoton microscopy and spectroscopy technology

Minghan Chen, Ming-Jun Li, Anping Liu

Author Affiliations +

Proceedings Volume 9347, Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications XIV; 93471Q (2015) https://doi.org/10.1117/12.2077731
Event: SPIE LASE, 2015, San Francisco, California, United States

Abstract

Germania doping is commonly used in the core of optical fiber due to its advantages compared to other materials such as superior transparency in near-infrared telecommunication wavelength region. During fiber preform manufacturing using the outside vapor deposition (OVD) process, Ge is doped into a silica soot preform by chemical vapor deposition. Since the Ge doping concentration profile is directly correlated with the fiber refractive index profile, its characterization is critical for the fiber industry. Electron probe micro-analyzer (EPMA) is a conventional analysis method for characterizing the Ge concentration profile. However, it requires extensive sample preparation and lengthy measurement. In this paper, a multiphoton microscopy technique is utilized to measure the Ge doping profile based on the multiphoton fluorescence intensity of the soot layers. Two samples, one with ramped and another with stepped Ge doping profiles were prepared for measurements. Measured results show that the technique is capable of distinguishing ramped and stepped Ge doping profiles with good accuracy. In the ramped soot sample, a sharp increment of doping level was observed in about 2 mm range from soot edge followed by a relative slow gradient doping accretion. As for the stepped doping sample, step sizes ranging from around 1 mm (at soot edge) to 3 mm (at soot center) were observed. All the measured profiles are in close agreement with that of the EPMA measurements. In addition, both multiphoton fluorescence (around 420 nm) and sharp second harmonic generations (at 532 nm) were observed, which indicates the co-existence of crystal and amorphous GeO₂.

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Minghan Chen, Ming-Jun Li, and Anping Liu "Characterizing germania concentration and structure in fiber soot using multiphoton microscopy and spectroscopy technology", Proc. SPIE 9347, Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications XIV, 93471Q (27 February 2015); https://doi.org/10.1117/12.2077731

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KEYWORDS

Germanium

Doping

Crystals

Multiphoton fluorescence microscopy

Multiphoton microscopy

Manufacturing

Multiphoton spectroscopy

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