Optical fiber Fabry-Perot interferometer cavity fabricated by femtosecond laser micromachining and fusion splicing for refractive index sensing

Abstract

Abstract:We demonstrate a fiber in-line Fabry-Perot interferometer cavity sensor for refractive index measurement. The interferometer cavity is formed by drilling a micro-hole at the cleaved fiber end facet, followed by fusion splicing. A micro-channel is inscribed by femtosecond laser micromachining to vertically cross the cavity to allow liquid to flow in. The refractive index sensitivity obtained is ~994 nm/RIU (refractive index unit). Such a device is simple in configuration, easy for fabrication and reliable in operation due to extremely low temperature cross sensitivity of ~4.8 × 10

Simultaneous measurement of temperature and refractive index using focused ion beam milled Fabry-Perot cavities in optical fiber micro-tips

“…Micromachining is a more recent technique that allows for the creation of very small cavities or microcavities. The two prominent techniques for optical fiber micromachining are femtosecond laser micromachining [11][12][13][14][15][16][17] and focused ion beam (FIB) milling [18][19][20][21][22][23]. Femtosecond (fs) laser micromachining has been used to create cavities in several ways.…”

“…Similarly, Ran et al have milled an air-gap and used fringe contrast to develop a temperature-insensitive refractive index sensor [13]. Liao et al have created a bubble-like cavity by drilling a micro-hole on a cleaved fiber facet and then fusion splicing it [14]. They then milled additional side channels to allow the insertion of fluids inside the cavity.…”

Temperature-insensitive refractive index sensing by use of micro Fabry–Pérot cavity based on simplified hollow-core photonic crystal fiber

“…The FP cavity fabricated by focused ion beam milling has been used to measure the RI around 1.30 with a high sensitivity of 1731 nm∕RIU [14] however; the temperature crosssensitivity of the device was not reported. By employing a femtosecond laser, micro FP cavity can be fabricated in single mode fiber (SMF) [15,16] and PCF [17], with a temperature sensitivity of larger than 2 pm∕°C, corresponding to a temperature cross-sensitivity of greater than 2 × 10 −6 RIU∕°C. By splicing a section of hollow-core PCF [18] or Er-doped fiber [19] with SMFs, strain sensors have been demonstrated, with further reduced temperature sensitivity of ∼0.81 and 0.65 pm∕°C, respectively.…”

Low-Cost Fiber-Tip Fabry-Perot Interferometer and Its Application for Transverse Load Sensing

“…As one kind of optical fiber sensors [1][2][3][4][5], fiber optic Fabry-Perot interferometers (FPIs), which offer the advantages of high resolution, compact structure and immunity to electromagnetic interference, play important roles in a large number of sensing applications such as refractive index [6][7][8][9], strain [10][11][12], temperature [13][14][15], pressure [16][17][18] and so on. Among them, the Fabry-Perot cavity which is fabricated at the fiber tip can be effectively used in space limited environment.…”