Tailoring Properties of Microcavity In-Line Mach-Zehnder Interferometer by the Microcavity Enlargement Using Femtosecond Laser

Long-Period Gratings and Microcavity In-Line Mach Zehnder Interferometers as Highly Sensitive Optical Fiber Platforms for Bacteria Sensing

“…The conical microcavity interferometer showed a RI sensitivity of about 9370 nm/RIU for a diameter of 51 µm [36], the trench cavity-about 10,800 nm/RIU around 1.333 (water) and −3243 nm/RIU around 1 (air) for trench lengths from 50 µm to 115 µm [37,44]. The circular micro-cavity interferometer of diameter 60 µm-about 12,000 nm/RIU around 1.333 [38][39][40]. These and similar structures are referred as microcavity in-fiber MZI-µIMZI.…”

“…Compared to the above MZ structure the femtosecond laser drilled microcavity MZIs exhibit a small size of the order of tens of microns and RI sensitivity comparable to that of nanocoated LPGs. The microcavity can be of different shapes as schematically shown in the Figure 5: conical [14,35,36], trench [37,38], circular [39][40][41][42][43]. In all cases, the microcavity cuts partially through the core, so that part of the mode propagates in the core and another part in the cavity.…”

“…For p > 0 the power is coupled from the core to the cavity while for p < 0 it is coupled back to the core. Since n < n 0 the beam is divergent, and losses occur [38]. At the other end of the microcavity a relative power p couples back to the core after having accumulated a phase difference with respect to the part propagating in the core whose relative part of the electric field is q.…”

Combined Long-Period Fiber Grating and Microcavity In-Line Mach–Zehnder Interferometer for Refractive Index Measurements with Limited Cross-Sensitivity

“…The cylindrical cavity (60 µm diameter) was micromachined in the middle of the LPG through the cladding and core reaching half of the fiber (60 µm depth) ( Figure 1B1,B2). The structure has a circular cross-section, flat bottom, while its walls, with good approximation, are perpendicular to the fiber's long axis [25]. The cavity diameter of 60 µm was chosen due to mechanical constraints and for ease of liquid application.…”

“…We used a home-made aluminum flow-cell where the bottom part was T-controlled in the range 10-45 • C. A reference µIMZI structure also underwent the same testing procedure. circular cross-section, flat bottom, while its walls, with good approximation, are perpendicular to the fiber's long axis [25]. The cavity diameter of 60 μm was chosen due to mechanical constraints and for ease of liquid application.…”