Optical interleaver based on nested multiple knot microfiber resonators

A novel design of nested optical fiber based multiple knot resonators is presented. The design consists of three knot resonators, two of which share a significant fraction of their optical path. The relationship between the knots’ diameter ratio and the transmission spectrum is investigated. The output spectrum is theoretically analyzed using transfer matrix analysis and the calculated results exhibit good agreement with experimental results. The free spectral range (FSR) is varied by simply fine-tuning the diameter of the small knot. The periodic spectrum of this optical microfiber based photonic device has a number of applications in the sensing and communications field, e.g., optical interleavers, frequency combs, filters, and fiber lasers. This Letter demonstrates that the variation of the output spectrum can be implemented simply by changing the knot sizes and coupling coefficients

Highly sensitive temperature sensor using packaged optical microfiber coupler filled with liquids

A novel temperature sensor based on a Teflon capillary encapsulated 2 × 2 optical microfiber coupler (OMC) filled with refractive index matching liquids is described. The sealed capillary and the filling liquid are demonstrated to enhance the temperature sensing performance, achieving a high temperature sensitivity of 5.3 nm/°C. To the best of our knowledge, the temperature sensor described in this article exhibits the highest sensitivity among the OMC structure based fiber optic temperature sensors. Experimental results also show that it has good repeatability along with a fast response time of 243 ms

Investigation of temperature dependence of microfibre coil resonators

The temperature-sensitive performance of a microfibre coil resonator (MCR) is thoroughly investigated. The MCR is fabricated by wrapping a microfibre on a PMMA rod coated with a UV-curable low refractive index epoxy. The temperature sensitivity is measured by investigating the correlation between the shift of the resonant wavelength and the surrounding temperature. It is determined that a range of parameters of the MCRs, including the gap between two adjacent rings, the diameter of the supporting rod, the number of rings, and the diameter of the microfibre have a great influence on the temperature sensitivity of the MCRs. By optimizing the fabrication parameters of MCRs, such as the gap of the adjacent microrings and the diameter of supporting rod etc, the maximum temperature sensitivity obtained is 237.31 pm/oC, which is about 2.3 times higher than that of MCR embedded in EFIRON UV-373 polymer and 23 times higher than that of MCR embedded in Teflon because of the strong thermo-optic and thermal expansion effects of the low refractive index epoxy and the supporting rod used in the experiments. Theoretical (numerical) simulation and experiment results are considered in the assessment of the optical performance improvement of MCR-based optical fibre temperature sensors

Tellurite glass and its application in lasers

This chapter provides expert coverage of the physical properties of new noncrystalline solids—tellurite glass and the latest laser applications of the material —offering insights into innovative applications for laser and sensing devices, among others. In particular, there is a focus on specialty optical fibers, supercontinuum generationandlaserdevices,andluminescencepropertiesforlaser applications. This chapter also addresses the fabrication and optical properties and uses oftellurite glasses inopticalfibersand opticalmicrocavities, thesignificance of from near infrared (NIR) to mid-infrared (MIR) emissions and the development of tellurite glass-based microcavity lasers. The important attributes of these tellurite glasses and their applications in lasers were discussed in this chapter

Investigation on the polarization dependence of an angled polished multimode fibre structure

An angled polished multimode (APM) fibre structure is described for the first time, to the best our knowledge, and its polarization dependence investigated theoretically and experimentally. Two angled planes are established in the multimode fibre (MMF) section of a single-mode-multimode-single-mode (SMS) fibre structure using the fibre side-polishing technique, forming the APM fibre structure. This designed circular asymmetric geometry induces different propagation characteristics for the TE and TM modes within the MMF. Simulated and experimental results both show that this difference is enhanced as the polishing angle increases, and a maximum extinction ratio (ER) of the spectrum of 13 dB is achieved at a polishing angle of 85°. This polarization-dependent device has a simple fabrication process and is free from the limitation of coating functional materials, which is expected to be applied in non-linear optics, fibre laser and optical fibre sensing fields

High sensitivity, low temperature-crosstalk strain sensor based on a microsphere embedded Fabry- Perot interferometer

In this article, a high sensitivity, low temperature-crosstalk strain sensor based on a microsphere embedded Fabry–Perot interferometer (FPI) is reported and experimentally demonstrated. The sensor is fabricated by embedding a microsphere inside a tapered hollow-core fiber (HCF) whose ends are enclosed by two standard single-mode fibers (SMFs). The reflections occurring at the SMF/HCF interface and the surfaces of the microsphere, result in a three-beam interference. The cavity length of the formed FPI can be flexibly changed by controlling the diameter of the tapered HCF and the size of the embedded microsphere, and the maximum extinction ratio (ER) of the reflection spectrum is greater than 11 dB. This novel microsphere embedded FPI structure significantly enhances the sensing performance of traditional FPIs for strain measurement, providing a high strain sensitivity of 16.2 pm/με with a resolution of 1.3 με. Moreover, it is demonstrated that this strain sensor has a very low temperature-strain cross-sensitivity of 0.086 με/oC, which greatly enhances the potential for applications in the field of precision strain measuremen

A microfiber knot incorporating a tungsten disulfide saturable absorber based multi-wavelength mode-locked erbium-doped fiber laser

A novel multi-wavelength mode-locked Erbium-doped fiber laser with tungsten disulfide (WS2) combined with a microfiber knot is described. This hybrid fiber structure facilitates strong light matter interaction between the saturated absorption of the WS2 material and high optical non-linearity of the microfiber knot. It is demonstrated experimentally that the novel fiber laser works stably in the absence of an external comb filter, with the generation of stable multi-wavelength picosecond pulses. In the multi-wavelength lasing regime, up to 7-wavelength stable mode-locked pulses are obtained using a polarization controller with the pump power at ~250 mW. The pulse period and the pulse width are 188.7 ns and 16.3 ps respectively. In addition, the number of multi-wavelength lasing channels can be changed by simply adjusting the microfiber knot size. Experimental results show the laser to have a stable output over 12 hours recording period. The results of this investigation demonstrate that the optical microfiber knot with a WS2 overlay based fiber laser device can operate as a highly nonlinear optical component and a saturable absorber. The proposed multi-wavelength lasing device can therefore be widely used for non-linear and ultrafast photonics and has a number of advantages compared to similar devices using more conventional technologies, including low cost and good stabilit

Engineering Dirac Materials: Metamorphic InAs_1–<i>x</i>Sb_<i>x</i>/InAs_1–<i>y</i>Sb_<i>y</i> Superlattices with Ultralow Bandgap

Quasiparticles with Dirac-type dispersion can be observed in nearly gapless bulk semiconductors alloys in which the bandgap is controlled through the material composition. We demonstrate that the Dirac dispersion can be realized in short-period InAs_1–<i>x</i>Sb_<i>x</i>/InAs_1–<i>y</i>Sb_<i>y</i> metamorphic superlattices with the bandgap tuned to zero by adjusting the superlattice period and layer strain. The new material has anisotropic carrier dispersion: the carrier energy associated with the in-plane motion is proportional to the wave vector and characterized by the Fermi velocity <i>v</i>_F, and the dispersion corresponding to the motion in the growth direction is quadratic. Experimental estimate of the Fermi velocity gives <i>v</i>_F = 6.7 × 10⁵ m/s. Remarkably, the Fermi velocity in this system can be controlled by varying the overlap between electron and hole states in the superlattice. Extreme design flexibility makes the short-period metamorphic InAs_1–<i>x</i>Sb_<i>x</i>/InAs_1–<i>y</i>Sb_<i>y</i> superlattice a new prospective platform for studying the effects of charge-carrier chirality and topologically nontrivial states in structures with the inverted bandgaps