Extinction ratio

About: Extinction ratio is a research topic. Over the lifetime, 8541 publications have been published within this topic receiving 111908 citations.

Compact and broadband polarization beam splitter based on a silicon nitride augmented low-index guiding structure.

Abstract: We propose a compact polarization beam splitter (PBS) based on a silicon nitride enhanced silicon-on-insulator platform using an augmented low-index guiding (ALIG) waveguide structure. In the ALIG structure, the TM mode is mostly confined in the low-index silicon nitride, while the TE mode is confined in the high-index silicon. Since the two modes are confined in two separate layers, their properties can be controlled independently. The PBS is formed using an asymmetric multimode interference (MMI) section. The TM mode is directed to an output port by the ALIG waveguide, while the TE mode is coupled to the other output port via the multimode interferometer. Such a PBS has a very small footprint, low insertion loss, high polarization extinction ratio, and broadband response.

Fano-resonance-based Mach-Zehnder optical switch employing dual-bus coupled ring resonator as two-beam interferometer

Abstract: A kind of Mach-Zehnder optical switch with a dual-bus coupled ring resonator as a two-beam interferometer is proposed and investigated. The analysis based on the transfer matrix method shows that a sharp asymmetric Fano line shape can be generated in the transmission spectra of such a configuration, which can be used to significantly reduce the phase change required for switching. Meanwhile, it can also be found that complete extinctions can be achieved in both switching states if the structural parameters are carefully chosen and the phase bias is properly set. Through tuning the phase difference between the arms of the Mach-Zehnder interferometer, complete extinction can be easily kept within a large range of the ring-bus coupling ratios in the OFF state. By properly modulating the phase change in the ring waveguide, the shift of the resonant frequency and the asymmetry of the transmission spectra can be controlled to finally enable optical switching with a high extinction ratio, even complete extinction, in the ON state. The switching functionality is verified by the finite-difference time-domain simulation.

Fabrication of single-polarisation single-mode-fibre couplers

Abstract: Fused biconical taper fibre couplers have been fabricated from single-polarisation single-mode fibres. A CVD technique is applied to permit maintenance of parallel alignment of the fibres in the coupler fabrication process. The couplers can hold linear polarisation along the principal axis of the fibre branches, showing an extinction ratio of about −15dB.

High-efficiency lithium niobate modulator for K band operation

Abstract: This paper reports a hybrid silicon nitride–lithium niobate electro-optic Mach–Zehnder-interferometer modulator that demonstrates overall improvements in terms of half-wave voltage, optical insertion loss, extinction ratio, and operational bandwidth. The fabricated device exhibits a DC half-wave voltage of ∼1.3 V, a static extinction ratio of ∼27 dB, an on-chip optical loss of ∼1.53 dB, and a 3 dB electro-optic bandwidth of 29 GHz. In addition, this device operates beyond the 3 dB bandwidth, where a half-wave voltage of 3 V is extracted at 40 GHz when the device is biased at quadrature. The modulator is realized by strip-loading thin-film lithium niobate with low-pressure chemical vapor deposited silicon nitride; this enables reduced on-chip losses and allows for a lengthened 2.4 cm long interaction region that is specifically engineered for broadband performance.

10 Gbit/s all-optical non-return to zero-return-to-zero data format conversion based on a backward dark-optical-comb injected semiconductor optical amplifier.

Abstract: By using a semiconductor optical amplifier backward injected by a dark-optical-comb pulse train at 10GHz, we demonstrate a 10Gbit/s all-optical nonreturn-to-zero (NRZ) to return-to-zero (RZ) format conversion of an incoming optical pseudorandom binary sequence (PRBS) data strieam. Both the polarity and the wavelength of data are conserved during format conversion. Without any preamplification, the extinction ratio of degraded optical NRZ PRBS data is greatly improved from 7.13 to 13.6dB after NRZ-to-RZ conversion. An ultralow bit-error rate of 10−12 at a data rate as high as 10Gbits/s is obtained with a received optical power of −18.3dBm. The converted RZ PRBS data exhibit a negative power penalty of >3.7dB compared with the NRZ PRBS data at a bit-error rate of 10−12.