Fabrication of Bragg Gratings on the End Facet of Standard Optical Fibers by Sputtering the Same Material

Abstract

A sputtering process has been applied to deposit quarter-wavelength stacks on the end facet of cleaved optical fibers by using only one material. Standard multimode optical fibers were used as substrates to fabricate broadband filters, and the experimentally measured spectral responses of these devices are shown. Periodical changes in the refractive index of the coating have been achieved by changing the sputtering pressure. A reflected peak with a full width at half maximum of 20 nm centered at 440 nm has been obtained, which provides a good structure for the development of optical fiber sensors working with the wavelength detection technique. This optical structure can be used for several purposes: as tunable wavelength filters or optical fiber sensors or to improve the performance of fluorescence sensors. A theoretical analysis of these structures corroborates the experimental results and allows some rules to be obtained.

Humidity Sensor Based on Bragg Gratings Developed on the End Facet of an Optical Fiber by Sputtering of One Single Material

“…Optical constants of HRIL have been kept as 4% greater than LRIL. These initial values of RIs have been chosen to agree with previous research [ 16 , 22 , 23 , 28 ]. Finally, a thin-film layer of water (50 nm of a layer with n = 1.33) has been added when simulating high RH values to simulate the layer of water physisorbed onto the coating surface.…”

[INVITED] Nanofabrication of phase-shifted Bragg gratings on the end facet of multimode fiber towards development of optical filters and sensors

“…The simulations in Fig. 4 and in the rest of the article have been performed with Matlab®, following a numerical method based on plane wave propagation in a one-dimensional stack of layers of different refractive indices [10,11]. Fused silica is the material of the multimode optical fiber.…”

“…The deposition of a stack of high and low refractive index materials on different substrates, such as silicon wafers, quartz, BK7 glass, or optical fiber, has been explored in several publications with the aim of developing optical filters and sensors [1][2][3][4][5][6][7][8][9][10].…”

“…On the one hand, optical fiber is immune against electromagnetic interferences, presents small diameter and high bandwidth, and is capable of multiplexing several signals. On the other hand, though some authors consider the deposition of high and low refractive index layers as a multilayer stack [1,[3][4][6][7][8] or a micrograting [2], others use more subtle terms such as Bragg stacks [5], or simply Bragg gratings [10]. This last term is more adequate in the work presented here because focus is centered on the monitorization of bands generated in the reflected spectrum according to the Bragg-Snell equation for normal incidence [5]:…”

“…In a recent work it has been proved that it is possible to develop a Bragg grating on the end facet of an optical fiber by DC sputtering technique with a single target, which increases the simplicity of the nanodeposition process [10]. In this work, the possibility of including a variation of the thickness in one of the layers of the grating is explored.…”