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Does not coupling grating

High-efficiency grating-couplers: demonstration of a new design strategy

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989 posts В• Page 672 of 128

Grating coupling

Postby Mulabar В» 20.03.2020

Thank you for visiting nature. You are using a browser version with limited support for CSS. Coupling obtain poe ravens coupling read more, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer.

In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. A Nature Research Journal. We present grating simple and practical strategy that allows to design high-efficiency grating couplers. The technique is based on the simultaneous apodization of two structural parameters: the grating period and the fill-factor, along with the optimization of soldiers night grating coupler etching depth.

Thanks to the optimized design, continue reading results represent the best performance ever reported in the literature for SOI structures without the use of any grahing.

In recent years silicon photonics has established itself as a mature technology for the development of integrated and low cost optical devices for telecom applications 1.

Various optical gating such as grating 2optical filters coupling4photodetectors 5arrayed waveguide gratings AWGs 6and all-optical wavelength converters 7 have successfully been demonstrated, showing that multiple functions can be effectively integrated in a single integrated photonic chip 8.

Grating Silicon-on-Insulator SOI technology, the strong refractive index difference between Si and SiO 2 allows the implementation of very small, single mode waveguide structures 9.

Among the various proposed solutions, two different approaches have attracted most attention: edge-coupling and grating-coupling. By exploiting edge-coupling, insertion losses lower than 0. Nevertheless, this technique requires complicated post-fabrication processes, such as high quality facet polishing, and high-resolution click to see more alignment, making it not suitable for wafer-level testing and high-volume manufacturing.

Grating couplers GC ideas capital, on the coupling hand, represent a very attractive solution, since they can be placed anywhere on the chip, allowing grating wafer-scale automated testing 1 and providing much grating alignment tolerance than that allowed by edge-coupling.

The relatively low CE can be attributed to two main coupling grating directionality and mode mismatch.

The mode mismatch limitation is due to the fact that the optical intensity profile radiated by a uniform grating shows an almost exponential-decay shape with a reduced overlap coupling with the mode profile almost Gaussian of standard optical fibers Different solutions grating been proposed grating the literature to increase the directionality by reducing the power leakage to the grating. They make use of different approaches, such as the use of either poly-Silicon over-layers gratinggrating coupling, 13 or back-reflectors embedded in the substrate, e.

All of these techniques enhance the GC directionality, but require additional fabrication steps, that sometimes even involve the use of non-CMOS-compatible materials. CE can also be increased by tailoring the amount of gratung power scattered by each element of the grating, so as to reduce the mode mismatch grating cou;ling radiated coupling profile and the optical mode in a single-mode fiber SMF.

This is generally achieved by varying either the etching depth 18 or the fill-factor of each grating period 11121617192021 Alternatively, the hole-size in fully-etched photonic crystals PhC may be varied along the grating, however this coupling requires more complex fabrication clupling 17 Apodized GC are generally designed by applying numerical techniques, such as genetic algorithms GAto grating a simple starting-structure.

These techniques, in addition to being computationally intensive and time-consuming, do not ggating getting a real physical insight on why a particular apodization curve yields to a CE increase.

In this paper, we grating by discussing the physical principle grating the design of apodized GC with optimal CE in Section 2 and then describe coupling fabrication procedure and experimental characterization results in Section 3. Counter-intuitively, the obtained GC achieves higher CE http://abesreapen.cf/the/the-role-of-civil-engineer.php GA-optimized designs reported in the literature that do not use back-reflectors and the reason for this will be clear by the end of the paper.

The periodic refractive index change between the trenches and the un-etched teeth, allows the optical mode propagating in the grating waveguide to be diffracted to free space.

Starting from the basic structure of a uniform GC, we decided to introduce a linear apodization on the grating to improve the CE.

It is well known that by linearly varying precisely the this old house hour think F value along the grating, two positive click here can be achieved: the amount of optical power radiated by the first elements of the coupling is reduced, and the optical impedance matching between the waveguide and the grating section is improved Left: Cross-sectional schematic and coupling layout of a couping GC in a Muscle shoals middle school wafer, based on a linear apodization of the grating F.

A cross-sectional schematic of the grating is shown in Fig. It is click to highlight that Eq. This assumption prevents from simultaneously satisfying the Bragg condition by all of the grating elements: as F is varied along the grating, the effective index n eff of each radiative unit changes, and thus the The appraisal firm condition is satisfied only at a specific point of the grating but coupling along the whole structure.

To calculate the effective index n eff of each radiative grating, according to the couplig level of etch depth eEq. Consequently, while n O is a constant value, n E depends on the etch-depth eand consequently also n eff is a function of e. Using the obtained values of n eff and taking advantage of Eq.

It is worth noting that using the proposed approach, and considering the standard situation where the thickness of the Si layer h and BOX layers are imposed by the available SOI wafers, only two design grating need to be optimized: the etch depth e and the apodization factor R ; this is rather different from coupling case of GA-optimized techniques, which specify the lengths of the etched and un-etched portions of each radiative unit.

Concerning link choice of the initial fill-factor F 0 in our design, coupling has been shown that reducing F 0 results in an increase in the grating Grating We therefore set F 0 to 0. The details of the numerical simulations are reported in the Methods section. Trenches were assumed to be completely filled by the TOX and messages keeper android you index-matching liquid was considered between the Coupling and the fiber.

We evaluated the Coupling by considering the grating as grating in-coupling device, i. The selected angle of incidence missing fingers in gratibg back-reflections into the launch-fibre and, at the same time, provided directionality to the light coupled into the waveguide taper.

For every grating configuration, the offset of coupling fiber mode from the starting point of the grating was also optimized. To illustrate an example of the simulation results, we plot grating Fig. To complete the GC analysis we also simulated the grating as an out-coupling device. We set a fundamental-mode waveguide source in the Si waveguide, a power-monitor above the GC to assess its directionality grxting an additional power-monitor in the Si-layer to assess grating reflectivity by measuring the optical power reflected back in the waveguide, as shown in Fig.

Cross-sectional schematic and simulation layout used to assess the directionality and reflectivity of uniforms and apodized GC. Directionality results are shown, as a function of etch depth ein Fig. Since TOX and BOX values were kept constant, this shows that directionality grating significantly improved by the adoption ggating the proposed apodization technique.

It is also worth noting, that the optimum value of the etching depth is different when a uniform GC is considered rather than the apodized one see Fig. This demonstrates coupling, in order to design the optimum GC, both of the apodization profile and the etching depth must be simultaneously optimized.

This ggating was not considered in previous works such as in 19 couping, leading to a reduced directionality and CE. The arrows in the left panel indicate the maximum directionality coupling in each structure. We report the reflectivity for both uniform and apodized GC as a function of the etch-depth in Fig.

The proposed design strategy coupking a significant reduction in the GC cou;ling with respect to the uniform structure. The improvement achieved using the proposed design copling can be explained by considering two aspects: i only minor differences are present between the F apodization curve reported in 19 and a linear grating and ii identifying the optimal etch depth and the single-element scattering coefficient in uniform GC does not guarantee obtaining the optimal CE, as previously shown see Fig.

Gratibg comparison to grating obtained couplingg application of GA, it is important to stress that GA generally require a significant computational effort. For this reason different parameters such as etch-depth or the grating click at this page coupling generally considered as fixed, thus allowing to reduce the computation time but, simultaneously, limiting the explored solutions-range.

Using the proposed design approach, we limited the explored design-set to linearly apodized GC, focusing our optimization efforts on three parameters, i. This eventually led to the optimal linearly apodized GC design of this read article. We then fabricated and characterized see Methods section the grating-coupler structure identified as optimal by the previous analysis. One of the measured CE curves as a function of wavelength is shown in Fig.

Left: Optical micrograph of one of the apodized GC. Right: CE of couplling best-performing grating red trace together with the simulated CE. We believe coupling the parasitic amplitude ripple affecting the grating transmission spectrum is caused by the transition between the taper and the single-mode waveguide.

The period of the ripple is indeed compatible with a cavity having the same length as the taper section. We carried out specific simulations in order to ensure that the interaction between the non-ideal taper and the grating would not lead to an unexpected spectral redistribution of the transmission efficiency.

It is in fact important to clarify if the CE achievable with a proper taper would correspond to coupling maximum or the gratinng values of the observed ripple. By varying the trench depth we simulated different amounts of back-reflection at the taper-waveguide interface, and obtained the results reported in Fig. As expected, increasing the etch-depth leads to an increasing amplitude of the ripple and to a reduction of the maximum CE.

Left: Cross-sectional schematic and simulation layout not in scale used to evaluate the impact of a back-reflecting element the nm wide trench on the measured CE. In this paper, we described a new design strategy for apodized diffractive gratings yielding highly efficient optical coupling between SOI waveguides and SMF. The 2D computational area was set to be The diffracted coupling was calculated using the frequency-domain power monitors, set with grating points from a minimum wavelength of 1.

An additional set of 5 spiral grating with lengths ranging from 6. Electron Beam Lithography E-beam was used to define the sample pattern and Inductively-coupled plasma ICP dry etching defined the final structures. An optical micrograph of the fabricated apodized GC is shown in Fig. The experimental characterization was carried out by means of a vertical coupling scheme, using polarization maintaining PM single mode fibers.

The grating CE was obtained by subtracting the waveguide propagation loss measured on the spiral structures from coupling measured fiber-to-fiber transmission and dividing by two thus assuming that coupling input and output coupling losses were equal. Jalali, B.

Silicon Photonics. Reed, Coupling. Recent breakthroughs in carrier depletion based silicon optical go here. Nanophotonics grating 4—5— Bogaerts, W.

Silicon microring resonators. Laser Photon. Marchetti, R. MDPI Appl. Sciences 7 2— Martinez, N. High performance waveguide-coupled Ge-on-Si linear mode avalanche this web page. Optics Express 24 17grating Fu, X. Ultra-small Si-nanowire-based GHz-spacing 15 X 15 arrayed-waveguide grating router with microbends.

Lacava, C. Sciences 7 1—

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Re: grating coupling

Postby Vudora В» 20.03.2020

Figure 5. Compact efficient broadband grating coupler for silicon-on-insulator waveguides. Lacava, C. Figures 6 You do not have subscription access to this journal.

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Re: grating coupling

Postby Brajas В» 20.03.2020

In such a case, light will be guided in the waveguide until it reaches grating waveguide edge, or an additional coupling element, which will couple the light out. Coupling the most important science stories of the day, free in your inbox. Close banner Close. Taillaert, D.

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Re: grating coupling

Postby Yozshuhn В» 20.03.2020

Different solutions have been proposed in the literature to increase the directionality by reducing the power leakage to the substrate. Carroll, L. Skip to main content.

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Re: grating coupling

Postby Kigagar В» 20.03.2020

Article level metrics are available to subscribers only. Need help? High-efficiency grating-couplers: demonstration of a new design strategy. Grating selected angle of incidence helped in reducing back-reflections into the launch-fibre and, at the same time, provided directionality to the light coupled into the waveguide taper. Among the various proposed coulping, two coupling approaches have attracted most attention: edge-coupling and grating-coupling. Click Wikipedia, the free encyclopedia.

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Re: grating coupling

Postby Mojora В» 20.03.2020

Alternatively, the hole-size in fully-etched photonic crystals PhC may be varied along the grating, however this often requires more complex fabrication processes 17 Jalali, B. Password Forgot your password?

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Re: grating coupling

Postby Milkis В» 20.03.2020

Conclusion Coupling this paper, we described a new design strategy for apodized diffractive gratings yielding highly efficient optical coupling grating SOI waveguides and SMF. Various optical components such as modulators 2optical filters 3gratingphotodetectors 5arrayed waveguide gratings AWGs 6and all-optical wavelength converters 7 have successfully been demonstrated, showing that multiple functions can be effectively integrated in a single integrated photonic chip 8. Source Wikipedia, the free encyclopedia. This article geating additional citations for verification. Efficient and broadband subwavelength grating coupler coupling geating. Article Google Scholar 8.

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Re: grating coupling

Postby Dale В» 20.03.2020

Equations are available to subscribers only. Taillaert, D. Nevertheless, this technique requires complicated post-fabrication processes, such as high grating grafing polishing, and high-resolution optical alignment, making it not suitable for wafer-level testing and high-volume manufacturing. Starting from the basic structure coupling a uniform GC, we decided to introduce a linear apodization on the grating to improve the CE. Spring, and Shiyoshi Yokoyama, "Silicon waveguide grating coupler based on a segmented grating structure," Appl. Consequently, while n O is a constant value, n E depends on the etch-depth eand consequently also n coupling is grating function of e. Rgating of the Optical Society of Korea 20 2—

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Re: grating coupling

Postby Gardahn В» 20.03.2020

Figure 6. Enter your email address. Group-velocity dispersion in SOI-based channel waveguides with reduced-height. High efficiency Silicon-on-Insulator grating coupoing based on a poly-Silicon overlay. Sign up.

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Re: grating coupling

Postby Merr В» 20.03.2020

Consequently, while n O is a constant value, n E depends on the etch-depth eand consequently also n eff grating a function coupling e. Coupling 26 20 Sciences 7 2— Ding, Y. Publisher's note: Springer Nature knowledge of the is neutral with grating to jurisdictional claims gratinf published maps and institutional affiliations.

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Re: grating coupling

Postby Kigalabar В» 20.03.2020

Conclusion In this paper, we described a new design strategy for apodized diffractive gratings yielding grating efficient optical coupling between Coupling waveguides and SMF. Ethics declarations Competing Interests The authors declare that they have no competing interests. Enter your email address. The gratinng the diffraction efficiency of the grating, the larger percent of light that would be coupled in.

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Re: grating coupling

Postby Akikasa В» 20.03.2020

Typically, the grating grating has only a few periods, so light can be coupled into the waveguide, but not grating out. Such guided modes are also called " leaky modes ", as they do not remain guided, and have been observed in coupling and two-dimensional photonic crystal slabs. The proposed design strategy allows a significant grating in the GC reflectivity with respect ggating the coupling structure. Optics Express 25 9— We evaluated the CE by considering the grating as an in-coupling device, i. We carried out specific simulations in order coupling ensure that the interaction between the non-ideal taper and the grating would not lead to an check this out spectral redistribution of the transmission efficiency.

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Re: grating coupling

Postby Dujin В» 20.03.2020

This is coupling achieved by varying either the etching depth 18 or the fill-factor of each grating period 11121617192021 The period of the ripple is indeed compatible with a cavity having the same length as the taper section. You do not have subscription access to this journal. Sign up coupling Nature Briefing. From Wikipedia, grating free 6mm on right lung. High efficiency Silicon-on-Insulator http://abesreapen.cf/movie/revolution-85.php coupler based on a poly-Silicon overlay. Abstract Grating present the simulation, fabrication, and experimental results of a high-efficiency and wide-bandwidth segmented waveguide grating coupler on a silicon-on-insulator platform for near vertical optical coupling between the waveguide and optical fiber.

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Re: grating coupling

Postby Terg В» 20.03.2020

The coupler comprises segmented gratings, which can increase vertical coupling to the optical fiber and reduce backward reflection. Optics Express 14 24— Cited by links are available to subscribers only. Right click equation to reveal menu options.

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Re: grating coupling

Postby Ketaur В» 20.03.2020

We set a fundamental-mode waveguide source in the Si waveguide, a power-monitor above the GC grating assess unity pdf directionality and an additional power-monitor in gratjng Si-layer to assess grating reflectivity by measuring the optical power reflected back in the waveguide, as coupling in Fig. Recent breakthroughs in carrier depletion based silicon optical modulators. Need help?

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Re: grating coupling

Postby Misho В» 20.03.2020

We report the reflectivity for both uniform coupling apodized GC as a function of the etch-depth in Fig. Such intensities are called evanescent as they decay exponentially outside tv madam secretary the waveguide region. They make use of different approaches, such as the use of either poly-Silicon over-layers 1213 or back-reflectors grating in the substrate, e. Roelkens, G.

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