In order to study the sensing performance of tellurite fiber based on FWM, a new tellurite photonic crystal fiber was designed a refractive index (RI) sensor. The simulation results show that the RI sensitivity of the sensor can be as high as 1826.8nm /RIU at a pumping wavelength of 1500 nm, and the linearity is as high as 99.9%.
A photonic crystal fiber is designed with chalcogenide glass As2Se3 as the base material. As2Se3 has a high refractive index and a high nonlinear refractive index; as a result, it has a desired application for strengthening birefringence and nonlinearity. The outer layer of the fiber is a regular decagonal structure composed of four layers of circular air holes, and the inner cladding area is composed of four elliptical air holes arranged in a diamond pattern. The influence of the size of the circular air holes in the fiber cladding, the thickness between each layer, and the size and position of the elliptical air holes in the inner cladding area on the birefringence is analyzed and studied using the full vector finite element method. The results show that the birefringence value of the fundamental mode of the fibers is 0.108 at a wavelength of 1.55 μm, and at the same time, the nonlinear coefficients of the X and Y polarization states are 240 and 197 m − 1 · W − 1, respectively.
We propose a gold-coated photonic crystal fiber (PCF) polarization filter and study the influencing parameters from a structural viewpoint. In this structure, small air holes and elliptical air holes near the core are used to increase the birefringence, and we have chosen two air holes with large diameter to coat with the metal Au. The designed filter showed a loss of 403.76 dB / cm in the y-polarization direction at the wavelength of 1.38 μm. However, the loss in the x-polarization direction was negligible, and can be selectively filtered out. Hence, light in a certain polarization direction achieves the effect of communication band filtering. We have used the finite-element method to simulate and analyze the influence of the structural parameter on fiber filter performance. The results reveal that the thickness of the metal layer, the diameter of the coated metal hole, and the asymmetry around the gold-coated hole significantly influence the position and coupling strength of the resonant response point between the surface plasmon and the core mode. In summary, the design parameters need to be optimized for maximum filtering performance of PCF. The present study opens up avenues for further research in communication band fiber filters.
Mid-infrared cascaded Stimulated Raman scattering (SRS) is experimentally investigated in an AsS optical fiber which fabricated based on As38S62 and As36S64 glasses and whose fiber loss was ∼0.09 dB/m at ∼2000 nm. Using a nanosecond laser operated at ∼1545 nm as the pump source, mid-infrared cascaded SRS up to eight orders is obtained in a 16 m AsS fiber. To the best of our knowledge, this is the first demonstration of eighth-order cascaded SRS in non-silica optical fibers, and it may contribute to developing tunable Raman fiber lasers in the mid-infrared region based on the C-band pump sources. When the pump wavelength switches to ∼2000 nm, only mid-infrared cascaded SRS up to five orders is obtained.
A high-birefringence photonic crystal fiber polarization filter is proposed. The coupling theory is used to explain full and incomplete couplings. The resonance point can be adjusted to the communication band by optimizing the fiber structure parameters. Numerical simulation results indicate that the resonance strength can reach 924.96 and 710.28 dB.cm−1 at the communication wavelength of 1.31 and 1.55 μm in x- and y-polarized directions, respectively. By filling liquid analyte, the confinement loss can reach 804.52 dB.cm−1 at the wavelength of 1.55 μm. Furthermore, when the fiber length of L equals 500 μm, the peak value of the cross talk (CT) can reach 389.15 and −280.52 dB, respectively. When the length of the fiber L equals 200 μm, the bandwidth of the CT better than 20 dB is up to 120 nm at the wavelength of 1.31 μm, and the bandwidth of the CT<−20 dB is up to 140 nm at the wavelength of 1.55 μm. These properties make it a good candidate for designing types of polarization filter devices.
Supercontinuum generation (SCG) was investigated in tapered tellurite microstructured optical fibers (MOFs) for various taper profiles. We emphasize on the procedure for finding the dispersion profile that achieve the best width of the SC spectra. An enhancement of the SCG is achieved by varying the taper waist diameter along its length in a carefully designed, and an optimal degree of tapering is found to exist for tapers with an axially uniform waist. We also show the XFROG spectrograms of the pulses propagating through different tapered fibers, confirming the optimized taper conditions.
A novel kind of wavelength-insensitive wide-spectrum polymer electro-optic (EO) switch is proposed by employing two symmetric active Mach-Zehnder interferometers (MZIs), a passive middle directional coupler and a pair of passive phase-generating couplers. Extinction ratio compensation condition under off-state and insertion loss compensation condition under on-state are derived to expand wavelength spectrum. With sufficient consideration of the wavelength dispersion of material and waveguide, optimization, and simulation were performed. The switch exhibits a switching voltage of 4.96 V with each MZI EO region length of 5000 μm. An S-C-L band (1460 to 1625 nm) covering a wide-spectrum more than 165 nm was obtained, and within this range, an extremely high extinction ratio more than 40 dB and an insertion loss within 1.8 to 11.9 dB were reached. This spectrum was more than 8 times of that of the traditional MZI EO switch (only 20 nm).The proposed device can function normally at any wavelength, and is an ideal candidate for a broadband photonic switching element in next-generation nonwavelength selective optical networks-on-chip.
A dual-driving polymer Mach-Zehnder interferometer (MZI) electro-optic switch is designed and optimized, which consists of a phase-generating coupler (PGC) and a 3-dB directional coupler. Structural schematics and principles of the PGC and the switch are described. Novel formulas of the switching time are presented. Under the central operation wavelength of 1550 nm, simulation for the designed device shows that the push-pull switching voltage is 2.445 V, the switching time is 18.1 ps, and the cross talk is less than −30 dB. By optimizing the PGC structure, the phase error resulting from the wavelength shift can be compensated effectively, and a wide spectrum about 110 nm can be achieved. The proposed analytical technique on waveguides and electrodes proves to be accurate and computationally efficient when compared with the beam propagation method (BPM) and the experimental results.
In terms of the coupled mode theory, novel formulas of the transfer functions are presented for a microring resonator array, which consists of multiple series-cascaded filter elements, and each of them contains double parallel-cascaded identical microrings. By using these formulas, we can analyze transmission characteristics for such a polymer device. Simulated results show that when some parameters are selected properly, the box-like spectral response can be formed, which is flat and steep, and the sidelobes and the cross talk can be dropped efficiently. The effects of manufacturing tolerances on the transmittance are discussed, which result in the shift of the transmission spectrum of the device.
Based on formulas presented for the amplitude coupling ratio and the transfer function, transmission characteristics are analyzed and parameters are optimized for a polymer cross-grid array of microring resonant wavelength multiplexers around the central wavelength of 1.550918 µm with wavelength spacing 1.6 nm. In the design of the device, by means of selecting a resonant order m=95 and introducing a resonant order increment of adjacent filter elements m=2, we increase the ring radius difference of adjacent filter elements R from 17 nm (for the case of m=0) to 337 nm. Calculated results show that the 3-dB bandwidth is about 0.2 nm, the ratio between the –1- and –10-dB bandwidths is about 0.22, the insertion loss is less than 0.5 dB, and crosstalk is below –39 dB for each of the eight horizontal output channels.
The MOEMS 2×2 optical switch with slant lower electrode and with torsion beam on silicon is designed and analyzed theoretically. Analytical formulae for the squeeze film damping coefficient and the squeeze film damping moment on the cantilever beam of the optical switch are derived. Based on the torsion dynamics theory, the technique and relative results are presented for analyzing the actuating voltage and the switch time. The optimized result of parameters is as: length, width and thickness of the torsion beam are 700, 12 and 10 um, length and width of the cantilever beam are 1900 and 1000 um, length and width of the balance beam are 100 and 1000 um, shortest spacing between the upper and lower electrodes is 0.05 um, and highness of the lower electrode is 55 um, respectively. The actuating voltage is less than 10 V, and the switching time of Ton and Toff are 1.30ms and 1.25ms, respectively. The computed results show that the air squeeze film damping is an important factor for the study of dynamic response on MOEMS optical switch.
Based on formulas presented, optimization design is performed and the effects of manufacturing tolerances on transmission characteristics are analyzed for a polymer microring resonant wavelength multiplexer around the central wavelength of 1.550918 µm with wavelength spacing 1.6 nm. Modeling results show that the insertion loss is less than 0.55 dB and crosstalk is less than –21 dB for each of eight vertical output channels of the designed device without tolerances. Some manufacturing tolerances result in a shift of the transmission spectrum and lead to increases of the inserted loss and crosstalk over the design case without tolerances
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