scholarly journals Simulating the effects of refractive index difference on the coupling efficiency of periodically segmented waveguide mode converter

2021 ◽  
Vol 51 (4) ◽  
Author(s):  
Yu Zheng ◽  
Hao He ◽  
Lianqiong Jiang ◽  
Ji’an Duan
Keyword(s):  
Refractive Index ◽  
Optical Waveguides ◽  
High Efficiency ◽  
Transmission Loss ◽  
Structural Parameters ◽  
Coupling Efficiency ◽  
Single Mode ◽  
Efficient Operation ◽  
Refractive Index Difference ◽  
Efficient Coupling

Efficient coupling of micro/nano-optical waveguides with single-mode fibers is the premise for the efficient operation of the integrated photonic chip, which directly determines its optical performance. In this paper, the design principles of periodically segmented waveguide (PSW) structure used for high-efficiency fiber-chip coupling are proposed, and the effects of refractive index difference Δ on coupling efficiency and structural parameters are studied by simulation. It is found that as the Δ of the PSW increases, the period of the PSW tends to be smaller, and the coupling efficiency decreases continuously, reduced by around 0.673 dB in the range of Δ = 3% to Δ = 7%. Through the analysis of PSW optical mechanisms, it demonstrates that the main reason for the decrease of coupling efficiency is that the transmission loss of the tapered section increases sharply with the increase of Δ. High-Δ PSW is difficult to apply to highly integrated silica optical chips due to the unignorably insertion loss.

scholarly journals Single-Mode Tapered Vertical SU-8 Waveguide Fabricated by E-Beam Lithography for Analyte Sensing

Sensors ◽  
2019 ◽  
Vol 19 (15) ◽  
pp. 3383 ◽  
Author(s):  
Yu Xin ◽  
Gregory Pandraud ◽  
Yongmeng Zhang ◽  
Paddy French
Keyword(s):  
Transmission Loss ◽  
Coupling Efficiency ◽  
Single Mode ◽  
Optical Measurements ◽  
Direct Writing ◽  
Sidewall Roughness ◽  
Scattering Loss ◽  
Waveguide Loss ◽  
One Step ◽  
Saline Solutions

In this paper, we propose a novel vertical SU-8 waveguide for evanescent analyte sensing. The waveguide is designed to possess a vertical and narrow structure to generate evanescent waves on both sides of the waveguide’s surface, aimed at increasing the sensitivity by enlarging the sensing areas. We performed simulations to monitor the influence of different parameters on the waveguide’s performance, including its height and width. E-beam lithography was used to fabricate the structure, as this one-step direct writing process enables easy, fast, and high-resolution fabrication. Furthermore, it reduces the sidewall roughness and decreases the induced scattering loss, which is a major source of waveguide loss. Couplers were added to improve the coupling efficiency and alignment tolerance, and will contribute to the feasibility of a plug-and-play optical system. Optical measurements show that the transmission loss is 1.03 ± 0.19 dB/cm. The absorption sensitivity was measured to be 4.8 dB per refractive index unit (dB/RIU) for saline solutions with various concentrations.

Fabrication, Characterization and Microsensing of Whispering-Gallery Mode Micro-Coupling Systems

2008 ◽  
Author(s):  
Qiulin Ma ◽  
Tobias Rossmann ◽  
Zhixiong Guo
Keyword(s):  
Transmission Loss ◽  
Coupling Efficiency ◽  
High Sensitivity ◽  
Single Mode ◽  
Whispering Gallery Mode ◽  
Single Mode Fiber ◽  
Whispering Gallery ◽  
Coupling System ◽  
Wide Range ◽  
Micro Sensor

An optical micro-coupling system of whispering-gallery mode usually consists of a resonator (e.g. a sphere) and a coupler (e.g. a taper). In this report, silica microspheres of 50–500 μm in diameter are fabricated by hydrogen flame fusing of an end of a single mode fiber or fiber taper. Fiber tapers are fabricated by the method of heating and pulling that meets an adiabatic condition. Taper’s waist diameter can routinely be made less than 1 μm and almost zero transmission loss in a taper is achieved which allows an effective and phase-matched coupling for a wide range sizes of microspheres. Both resonators and couplers’ surface microstructure and shapes are examined by scanning electronic microscopy. Three regimes of coupling are achieved, enabling a good flexibility to control Q value and coupling efficiency of a micro-coupling system. Whispering gallery mode shift is used to demonstrate a novel temperature micro-sensor. Its sensitivity determined from actual experimental results agrees well with the theoretical value. A concept of using the photon’s cavity ring down (CRD) in the microsphere to make a novel high-sensitivity trace gas micro-sensor is proposed. The CRD time constant when ammonia is chosen as the analyte gas is predicted using the simulated absorption lines.

scholarly journals Single-mode optical waveguides on native high-refractive-index substrates

APL Photonics ◽  
2016 ◽  
Vol 1 (7) ◽  
pp. 071302 ◽  
Author(s):  
Richard R. Grote ◽  
Lee C. Bassett
Keyword(s):  
Refractive Index ◽  
Optical Waveguides ◽  
Single Mode ◽  
High Refractive Index

scholarly journals Design of Fiber-Tip Refractive Index Sensor Based on Resonant Waveguide Grating with Enhanced Peak Intensity

2021 ◽  
Vol 11 (15) ◽  
pp. 6737
Author(s):  
Yicun Yao ◽  
Yanru Xie ◽  
Nan-Kuang Chen ◽  
Ivonne Pfalzgraf ◽  
Sergiy Suntsov ◽  
...  
Keyword(s):  
Refractive Index ◽  
Coupling Efficiency ◽  
High Sensitivity ◽  
Single Mode ◽  
Medical Diagnostics ◽  
Spatial Multiplexing ◽  
Fiber Optic Sensor ◽  
Resonant Peak ◽  
Refractive Index Sensor ◽  
Peak Intensity

Resonant waveguide gratings (RWG) are widely used as on-chip refractometers due to their relatively high sensitivity to ambient refractive index changes, their possibility of parallel high-throughput detection and their easy fabrication. In the last two decades, efforts have been made to integrate RWG sensors onto fiber facets, although practical application is still hindered by the limited resonant peak intensity caused by the low coupling efficiency between the reflected beam and the fiber mode. In this work, we propose a new compact RWG fiber-optic sensor with an additional Fabry-Pérot cavity, which is directly integrated onto the tip of a single-mode fiber. By introducing such a resonant structure, a strongly enhanced peak reflectance and improved figure of merit are achieved, while, at the same time, the grating size can be greatly reduced, thus allowing for spatial multiplexing of many sensors on a tip of a single multi-core fiber. This paves the way for the development of probe-like reflective fiber-tip RWG sensors, which are of great interest for multi-channel biochemical sensing and for real-time medical diagnostics.

scholarly journals Combined Long-Period Fiber Grating and Microcavity In-Line Mach–Zehnder Interferometer for Refractive Index Measurements with Limited Cross-Sensitivity

Sensors ◽  
2020 ◽  
Vol 20 (8) ◽  
pp. 2431 ◽  
Author(s):  
Monika Janik ◽  
Marcin Koba ◽  
Krystian Król ◽  
Predrag Mikulic ◽  
Wojtek J. Bock ◽  
...  
Keyword(s):  
Refractive Index ◽  
High Efficiency ◽  
Single Mode ◽  
Zehnder Interferometer ◽  
Fiber Grating ◽  
Long Period Grating ◽  
Cross Sensitivity ◽  
Long Period ◽  
Period Fiber Grating ◽  
Mach Zehnder Interferometer

This work discusses sensing properties of a long-period grating (LPG) and microcavity in-line Mach–Zehnder interferometer (µIMZI) when both are induced in the same single-mode optical fiber. LPGs were either etched or nanocoated with aluminum oxide (Al2O3) to increase its refractive index (RI) sensitivity up to ≈2000 and 9000 nm/RIU, respectively. The µIMZI was machined using a femtosecond laser as a cylindrical cavity (d = 60 μm) in the center of the LPG. In transmission measurements for various RI in the cavity and around the LPG we observed two effects coming from the two independently working sensors. This dual operation had no significant impact on either of the devices in terms of their functional properties, especially in a lower RI range. Moreover, due to the properties of combined sensors two major effects can be distinguished—sensitivity to the RI of the volume and sensitivity to the RI at the surface. Considering also the negligible temperature sensitivity of the µIMZI, it makes the combination of LPG and µIMZI sensors a promising approach to limit cross-sensitivity or tackle simultaneous measurements of multiple effects with high efficiency and reliability.

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