Micro Fabry-Perot interferometers in silica fibers machined by femtosecond laser

Abstract

Micro Fabry-Perot (F-P) interferometers (MFPIs) are machined in a single-mode fiber (SMF) and a photonic crystal fiber (PCF) by using a near-infrared femtosecond laser, respectively. The strain and temperature characteristics of the two MFPIs with an identical cavity length are investigated and the experimental results show that the strain sensitivity of the PCF-based MFPI is smaller than that of the SMF-based MFPI due to their different waveguide structures, while the two MFPIs have close temperature sensitivities due to their similar host materials. These MFPIs in silica fibers are compact, stable, inexpensive, capable for mass-production and easy fabrication, offering great potentials for wide sensing applications.

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.…”

Femtosecond pulse written fiber gratings: a new avenue to integrated fiber technology

“…Two fiber sensor examples are a micro-fabry-perot interferometer within the cladding of a fiber [158] and air hole welding in photonic crystal fiber [159].…”

Miniature Engineered Tapered Fiber Tip Devices by Focused Ion Beam Micromachining

“…MCFPIs with tens-ofmicrometer-length cavity are attractive because of the small size, large free spectrum range (FSR) and high sensitivity. The cavity can be assembled by splicing two single mode fibers (SMFs) to a hollow-core fiber (Sirkis et al, 1993), inserting a silica SMF and a multi-mode fiber into a glass capillary (Bhatia et al, 1996), or splicing a SMF and an index-guiding photonic crystal fiber together (Villatoro et al, 2009 (Rao et al, 2007). However, even the fs-laser machined MCFPIs still show low fringe visibility of several dBs in liquids due to the rugged surfaces inside the cavity; what's more, it is difficult to focus the laser spot to a sub-wavelength scale due to the diffraction limit.…”