Extinction ratio

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

High extinction-ratio compact polarisation beam splitter on silicon

Abstract: A novel polarisation beam splitter (PBS) with a high extinction ratio in a broad band has been proposed and realised by cascading a bent directional coupler and a low-loss transverse-magnetic (TM)-pass polariser based on a subwavelength grating. The realised PBS has a footprint as small as 3 × 22.5 μm, a high extinction ratio (>20 dB) and a low excess loss (~1 dB) are obtained over a broad band of ~60 nm for both transverse-electric and TM polarisations.

Sub-15 nm linewidth gratings using roll-to-roll nanoimprinting and plasma trimming to fabricate flexible wire-grid polarizers with low colour shift.

Abstract: Sub-15 nm-wide gratings with a high aspect ratio of up to 16:1 were fabricated using roll-to-roll nanoimprinting and plasma trimming to achieve high optical performance (up to 12 000:1 extinction ratio with an average transmittance of 82%) and low colour shift (transmittance variation less than 3%) flexible wire-grid polarizers for display applications. We applied two imprint platforms onto glass and plastic substrates to identify the optical properties and characteristics of each fabrication process. To enhance the tolerance, reproducibility, and optical performance of the process, the grating profile symmetry and varying residual layer thicknesses were precisely simulated and controlled to achieve the design targets.

Full Evaluation of Polarization Characteristics of Multifunctional Integrated Optic Chip With High Accuracy

Abstract: The polarization characteristics of the multifunctional integrated optic chip (MFIOC) are fully evaluated with high accuracy by using optical coherence domain polarimetry based on white light interferometer. Two polarization maintaining (PM) fibers, serving as extended fibers, are spliced to the PM pigtails of the MFIOC with polarization axes aligned. By launching light at 45° to the birefringence axes of the lead-in extended PM fiber, the beams along the fast and slow axes of the birefringent waveguides interfere after a 45° polarization analyzer and an optical path correlator. The polarization extinction ratio (PER) and birefringence of the LiNbO3 Y-waveguide, the birefringence of the PM pigtails, and the crosstalks at the connection points between the Y-waveguide and the PM pigtails can be simultaneously obtained from the amplitudes and positions of the corresponding interference peaks. The characteristic peak of the Y-waveguide's PER is shifted out of the interference peak of the light source ripple by selecting proper length of the extended fibers. The extended fibers also brings in two additional cross-coupling points at the ends of the PM pigtails, which are used for calculating the birefringence of the PM pigtails. In addition, the alignment type between the PM pigtails and the birefringent Y-waveguide is identified according to the position of the characteristic peak of the Y-waveguide's PER. Theoretical model based on Jones matrix is built to describe the characteristic peaks of the MFIOC. Two MFIOCs with different alignment angle between the PM pigtails and the Y-waveguide are experimentally tested. Results show that the PER resolution of the proposed method can achieve nearly −90 dB and the dynamic range of the test system is about 90 dB.

Advances Toward Ge/SiGe Quantum-Well Waveguide Modulators at 1.3μm

Abstract: The paper reports on the developments of Ge/SiGe quantum well (QW) waveguide modulators operating at 1.3 μm. Two modulator configurations have been studied: The first one is based on QW structures grown on a 13-μm SiGe buffer on bulk silicon. Light was directly coupled and propagated in Ge/Si0.35Ge0.65 QWs. Using a 3-μm-wide and 50-μm-long modulator, an extinction ratio (ER) up to 6 dB was obtained at 1.3 μm. In the second configuration, the aim is to integrate Ge/SiGe QW on standard silicon-on-insulator (SOI) waveguides. A reduction of buffer thickness is then required to allow the light coupling from Si waveguide to Ge/SiGe QW. To this purpose, first we demonstrated QCSE with a thin (360-nm-thick) Si0.08Ge0.92 buffer on silicon using the well-known Ge/Si0.15Ge0.85 QWs (operated at a wavelength of 1.4 μm). Based on these promising experimental results, we theoretically investigated properties of a Ge/Si0.65Ge0.35 QW modulator integrated on SOI waveguides. 7.7 dB ER were predicted with 4 dB optical insertion loss and an estimated energy consumption of 59 fJ/bit for a modulator length as short as 69 μm.

Optical switch including bypass waveguide

Abstract: Herein disclosed is a branch type optical switch having three or more optical waveguides capable of being coupled to one another in a coupling region, in which is formed a refractive index changing portion for effecting the function of the branch type optical switch by changing the refractive index thereof. This optical switch has a small coupling loss and an excellent extinction ratio. Also disclosed is an intersection type optical switch having two or more optical waveguides intersecting each other. The input optical waveguide and the output waveguide are connected at their intersection by means of a bypass optical waveguide to construct the above-specified branch type optical switch in the coupling regions of the bypass optical waveguides and the input and output optical waveguides, and the bypass optical waveguide has a curved or polygonal shape. Thus, it is possible to provide a small-sized optical switch which has an excellent extinction ratio and little variability in characteristics.