We report the fabrication of in-line photonic microcells (PMCs) by encapsulating tapered elliptical microfibers (MFs) inside glass tubes. The encapsulation does not change the optical property of the MF but protects the elliptical MF from external disturbance and contamination and makes the micro-laboratory robust. Such micro-laboratory can be easily integrated into standard fiber-optic circuits with low loss, making the elliptical MF-based devices more practical for real-world applications. Evanescent field sensing is realized by fabricating micro-channel on the PMC for ingress/egress of sample liquids/gas. Based on the encapsulated elliptical MF PMCs, we demonstrated RI sensitivity of 2024 nm per refractive index unit (nm/RIU) in gaseous environment and 21231 nm/RIU in water.
We report the fabrication of long-period gratings (LPGs) in highly birefringent (Hi-Bi) microfibers. The LPGs were
fabricated by using a femtosecond infrared laser to modify the surface or a CO2 laser to induce micro-tapers periodically
along the Hi-Bi microfibers. These LPGs have pitches from tens to hundreds of micrometers and very strong polarization
dependent resonances. A LPG fabricated on a Hi-Bi microfiber with a major-diameter of ~2.8 μm and an ellipticity of
~0.7 demonstrated a refractive index sensitivity of ~4623 nm/RIU in water.
We report a novel type of highly birefringent suspended core (SC) photonic microcells made by selectively inflating four air-columns in a solid core photonic crystal fiber. The wavelength-scale SC has two-fold rotational symmetry and exhibits high phase and group birefringence of ~3 x10-3 and ~5 x10-3 respectively at 1550 nm. By incorporating such microcells into Sagnac fiber loop interferometers, we demonstrated refractive index, temperature and gas pressure sensors with good performances.
A novel class of polarization converters (PCs) in highly birefringent (Hi-Bi) microfibers is proposed and investi-
gated numerically by use of the coded full vectorial finite difference beam propagation method. The novel PCs
may be implemented by periodically deforming the surface along “one-side” of a Hi-Bi microfiber. Simulation
shows that complete polarization may be achieved with a device length of less than 300 μm.
We report the fabrication of in-line fiber-optic photonic microcells by post-processing commercial photonic crystal fibers. With such microcells, novel photonic devices such as in-fiber amplifiers, grating filters, and accelerometers are created.
Highly birefringent (Hi-Bi) microfiber-based fiber loop mirrors (FLMs) are studied for gas pressure measurement. A elliptical microfiber is made by tapering a femtosecond laser-processed single mode fiber and demonstrated a very high birefringence of up to 10-2 . The microfiber is housed within a pressure tube with which gas pressure measurement is carried out. The robust microfiber sensor demonstrates a pressure sensitivity of 6 pm/kPa with a temperature cross-sensitivity of less than 0.01 nm/K.
A novel class of polarization converters (PCs) in highly birefringent (Hi-Bi) microfibers is proposed and investigated numerically by use of the coded full vectorial finite difference beam propagation method. The PCs could be implemented by inducing periodic deformations along the surface of a Hi-Bi microfiber. Simulation shows that complete conversion between two linearly polarized eigen modes may be achieved with a device as short as 150 μm.
Heat transfer is very complicate in fusion splicing process of photonic crystal fibers (PCFs) due to different structures
and sizes of air hole, which requires different fusion splicing power and offsets of heat source. Based on the heat transfer
characteristics, this paper focus on the optimal splicing offset splicing the single mode fiber and PCFs with a CO2 laser
irradiation. The theory and experiments both show that the research results can effectively calculate the optimal fusion
splicing offset and guide the practical splicing between PCFs and SMFs.
Highly birefringent (Hi-Bi) microfiber-based fiber loop mirrors (FLMs) were studied for tunable comb filters and refractive index (RI) sensors. RI sensitivity of up to 15,441 nm/RIU was experimentally demonstrated for the RI sensors and, for the tunable filter a thermal tuning coefficient of ~-2.35nm/°C was obtained for temperature from 20 to 90°C when it was immersed into water. The use of two cascaded Hi-Bi micro-tapers within a Sagnac loop allows more flexibility in controlling the transmission/reflection spectraums of the FLM. The length of the tapered Hi-Bi microfibers is on the order of centimeters, two orders of magnitude shorter than the conventional Hi-Bi fiber-based devices.
Long period gratings (LPGs) can be made by rocking a single mode fiber and at the same time periodically scanning
a focused CO2 beam across the fiber. A 15 period LPG with ~ 3 degree rocking angle and 1.3 mm pitch exhibits a narrow
bandwidth of 4.8 nm and a resonant attenuation of 33.5 dB. The novel LPG has a temperature sensitivity of -77 pm/°C
and a strain sensitivity of -0.14 nm/mε , and is insensitive to twist.