scholarly journals Effect of Dispersion-Enhanced Sensitivity in a Two-Mode Optical Waveguide with an Asymmetric Diffraction Grating

Sensors ◽  
2021 ◽  
Vol 21 (16) ◽  
pp. 5492
Author(s):  
Andrei Tsarev
Keyword(s):  
Refractive Index ◽  
Optical Waveguide ◽  
Optical Sensors ◽  
High Efficiency ◽  
Single Mode ◽  
Bragg Diffraction ◽  
Mode Interaction ◽  
Enhanced Sensitivity ◽  
Better Than ◽  
Waveguide Surface

Analysis of trends in the development of silicon photonics shows the high efficiency regarding the creation of optical sensors. The concept of bimodal sensors, which suggests moving away from the usual paradigm based only on single-mode waveguides and using the inter-mode interaction of guided optical waves in a two-mode optical waveguide, is developed in the present paper. In this case, the interaction occurs in the presence of an asymmetric periodic perturbation of the refractive index above the waveguide surface. Such a system has unique dispersion properties that lead to the implementation of collinear Bragg diffraction with the mode number transformation, in which there is an extremely high dependence of the Bragg wavelength on the change in the refractive index of the environment. This is called the “effect of dispersion-enhanced sensitivity”. In this paper, it is shown by numerical calculation methods that the effect can be used to create optical sensors with the homogeneous sensitivity higher than 3000 nm/RIU, which is many times better than that of sensors in single-mode waveguide structures.

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 Ray Tracing Method of Gradient Refractive Index Medium Based on Refractive Index Step

2021 ◽  
Vol 11 (3) ◽  
pp. 912
Author(s):  
Qingpeng Zhang ◽  
Yi Tan ◽  
Ge Ren ◽  
Tao Tang
Keyword(s):  
Refractive Index ◽  
Ray Tracing ◽  
High Efficiency ◽  
Sudden Change ◽  
Ray Tracing Method ◽  
Starting Point ◽  
Index Changes ◽  
Gradient Refractive Index ◽  
Tracing Method ◽  
Better Than

For gradient refractive index media with large refractive index gradients, traditional ray tracing methods based on refined elements or spatial geometric steps have problems such as low tracing accuracy and efficiency. The ray tracing method based on refractive index steps proposed in this paper can effectively solve this problem. This method uses the refractive index step to replace the spatial geometric step. The starting point and the end point of each ray tracing step are on the constant refractive-index surfaces. It avoids the problem that the traditional tracing method cannot adapt to the area of sudden change in the refractive index and the area where the refractive index changes sharply. Therefore, a suitable distance can be performed in the iterative process. It can achieve high-efficiency and precise ray tracing in areas whether the refractive index changes slowly or sharply. According to the comparison of calculation examples, this method can achieve a tracing accuracy of 10−5 mm. The speed and precision of ray tracing are better than traditional methods.

Nickel Determination by Complexation Utilizing a Functionalized Optical Waveguide Sensor

2000 ◽  
Vol 658 ◽  
Author(s):  
Erin S. Carter ◽  
Klaus-H. Dahmen
Keyword(s):  
Refractive Index ◽  
Optical Waveguide ◽  
Light Propagation ◽  
Sol Gel ◽  
Specific Chemical ◽  
Optically Transparent ◽  
Nickel Determination ◽  
Waveguide Surface ◽  
Waveguide Sensor ◽  
Surface Changes

ABSTRACTThis research focuses on the design of chemically functionalized optical waveguide sensors. The waveguide is an optically transparent sol-gel coated onto a glass substrate chip. By having a higher refractive index than the substrate, the waveguide internally reflects a laser beam to photodetectors at both ends of the chip. The adsorption of any species onto the waveguide surface changes the light propagation, and therefore its effective refractive index, N. The change in N is dependent upon the amount of analyte present. By covalently bonding specific chemical receptors onto its surface, it can be designed to target a particular analyte. This research involves functionalizing the surface of the waveguide with ED3A in order to complex out of solution Ni2+. The change in N and the thickness of the adlayer will allow the concentration to be determined.

TWO NOVEL INTEGRATED OPTICAL SENSOR TYPES FOR MEASURING CHEMICAL CONCENTRATIONS, BASED ON CHEMICALLY INDUCED CHANGES OF MODAL FIELD PROFILES

2004 ◽  
Vol 13 (02) ◽  
pp. 209-227 ◽  
Author(s):  
PAUL V. LAMBECK ◽  
HUGO J. W. M. HOEKSTRA ◽  
JORIS VAN LITH ◽  
GIJS VAN ELZAKKER
Keyword(s):  
Refractive Index ◽  
Optical Sensors ◽  
Guided Mode ◽  
Chemically Induced ◽  
Integrated Optical ◽  
Modal Field ◽  
Induced Changes ◽  
Integrated Optical Sensor ◽  
Better Than ◽  
Waveguide Sensor

Two novel principles of sensing chemical concentrations by integrated optical sensors are presented. Both sensors are of the refractive type implying that a change of chemical concentration manifests itself as a change of the refractive index of a material located within the field profile of a guided mode. In contrast to common practice it is not the induced change of the effective refractive index N eff , but the change of the modal field profiles that is utilized for sensing, and here the changes of the refractive index finally show up as changes of the attenuation of a propagating mode. In the segmented waveguide sensor (SWS) the dependence of the modal transfer at the transition between two adjacent channel segments on the refractive index distributions of both segments is exploited while the second one relies on changes of the modal absorption as a result of a change of the penetration of the modal field into an absorptive region. Sensitivity and resolution-potential of both principles have been analyzed theoretically also taking into account the properties of peripheral equipment. Based on structures producible with SiON technology a SWS with a refractive index resolution of 5×10-7 can be easily designed. In an implementation of the second principle suited for immuno-sensing, a resolution in the thickness of the immuno-layer better than 10-4 nm is shown to be theoretically feasible. A SWS sensor has been realized; theoretically and experimentally obtained performance corresponds well to each other.

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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