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Photonic Band Engineered Optical Filters for Downhole Applications

IP.com Disclosure Number: IPCOM000227857D
Publication Date: 2013-May-22
Document File: 2 page(s) / 45K

Publishing Venue

The IP.com Prior Art Database

Abstract

This disclosure discusses a method to filter an optical spectrum. This method enables a narrow spectral bandwidth of a few nanometers or less to be selected and isolated from a broad optical spectrum. Optical interrogation of downhole fluids is an integral part of the oilfield services business, but downhole tools are challenged to measure individual wavelengths due to the lack of optical filters with a narrow band-pass and good out-of-band rejection. Here we describe two filtration systems that utilize engineered photonic band structures to achieve filters exhibiting pass-bandwidths that can range from 10 nm down to 0.01 nm. Use of these filters would greatly facilitate downhole fluid compositional and identification measurements.

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Page 01 of 2

Photonic Band Engineered Optical Filters for Downhole Applications

This disclosure discusses a method to filter an optical spectrum. This method enables a narrow spectral bandwidth of a few nanometers or less to be selected and isolated from a broad optical spectrum. Optical interrogation of downhole fluids is an integral part of the oilfield services business, but downhole tools are challenged to measure individual wavelengths due to the lack of optical filters with a narrow band-pass and good out-of- band rejection. Here we describe two filtration systems that utilize engineered photonic band structures to achieve filters exhibiting pass-bandwidths that can range from 10 nm down to 0.01 nm. Use of these filters would greatly facilitate downhole fluid compositional and identification measurements.

Fig. 1

Fig. 1 shows one embodiment of an optical filter. Light with a wide bandwidth propagates down a waveguide (propagation direction shown by the white arrows above, pointing from left to right). In one section of the waveguide, the light encounters periodic variation of the index of refraction (shown as red dots above). This periodic modulation is designed and fabricated into the waveuide to create a photonic bandgap with a narrow bandwidth: light in this bandgap is forced to exit normal to the beam surface (represented above by the vertical yellow arrow). Upon exiting, the light can be collected and measured using standard optical detectors.


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Fig. 2

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