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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 22, Iss. 15 — Jul. 28, 2014
  • pp: 18224–18231
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Focusing-curved subwavelength grating couplers for ultra-broadband silicon photonics optical interfaces

Qiuhang Zhong, Venkat Veerasubramanian, Yun Wang, Wei Shi, David Patel, Samir Ghosh, Alireza Samani, Lukas Chrostowski, Richard Bojko, and David V. Plant  »View Author Affiliations


Optics Express, Vol. 22, Issue 15, pp. 18224-18231 (2014)
http://dx.doi.org/10.1364/OE.22.018224


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Abstract

We report on the design and characterization of focusing-curved subwavelength grating couplers for ultra-broadband silicon photonics optical interfaces. With implementation of waveguide dispersion engineered subwavelength structures, an ultra-wide 1-dB bandwidth of over 100 nm (largest reported to date) near 1550 nm is experimentally achieved for transverse-electric polarized light. By tapering the subwavelength structures, back reflection is effectively suppressed and grating coupling efficiency is increased to −4.7 dB. A compact device footprint of 40 µm × 20 µm is realized by curving the gratings in a focusing scheme.

© 2014 Optical Society of America

1. Introduction

In this paper, we present the design of broadband subwavelength grating couplers (SWGCs) in a focusing-curved scheme. The SWGCs are fabricated by electron-beam lithography (EBL) on a standard silicon-on-insulator (SOI) platform with a single-step full-etching. A 1-dB bandwidth of over 100 nm around 1550 nm is measured for transverse-electric (TE) polarized light. To the best of our knowledge, this is the largest bandwidth reported in silicon grating couplers to date. The improvement of bandwidth is achieved by applying subwavelength grating structures to suppress the waveguide dispersion. By designing small anti-reflection tapers, the back reflection of gratings is effectively suppressed and the coupling efficiency is improved to −4.7 dB. In addition, the SWGCs are designed in a focusing-curved geometry, which significantly shrinks the length of the adiabatic taper from several hundred microns required by straight-line grating designs [7

7. X. Chen, K. Xu, Z. Cheng, C. K. Y. Fung, and H. K. Tsang, “Wideband subwavelength gratings for coupling between silicon-on-insulator waveguides and optical fibers,” Opt. Lett. 37(17), 3483–3485 (2012). [CrossRef] [PubMed]

,9

9. X. Xu, H. Subbaraman, J. Covey, D. Kwong, A. Hosseini, and R. T. Chen, “Colorless grating couplers realized by interleaving dispersion engineered subwavelength structures,” Opt. Lett. 38(18), 3588–3591 (2013). [CrossRef] [PubMed]

] to only 20 µm, and yields a compact device footprint of 40 µm × 20 µm without introducing performance penalties.

2. Principle, simulation and layout design

The conventional straight-line grating design shown in Fig. 1(a) requires a 500-µm-long adiabatic taper to convert the optical mode from the gratings to the waveguide with low loss [7

7. X. Chen, K. Xu, Z. Cheng, C. K. Y. Fung, and H. K. Tsang, “Wideband subwavelength gratings for coupling between silicon-on-insulator waveguides and optical fibers,” Opt. Lett. 37(17), 3483–3485 (2012). [CrossRef] [PubMed]

,9

9. X. Xu, H. Subbaraman, J. Covey, D. Kwong, A. Hosseini, and R. T. Chen, “Colorless grating couplers realized by interleaving dispersion engineered subwavelength structures,” Opt. Lett. 38(18), 3588–3591 (2013). [CrossRef] [PubMed]

]. In order to reduce the length of the adiabatic taper, the gratings can be designed in a curved geometry to produce a circular wavefront and focus the optical mode into the waveguide. According to [16

16. R. Waldhäusl, B. Schnabel, P. Dannberg, E.-B. Kley, A. Bräuer, and W. Karthe, “Efficient coupling into polymer waveguides by gratings,” Appl. Opt. 36(36), 9383–9390 (1997). [CrossRef] [PubMed]

,17

17. F. Van Laere, T. Claes, J. Schrauwen, S. Scheerlinck, W. Bogaerts, D. Taillaert, L. O’Faolain, D. Van Thourhout, and R. Baets, “Compact focusing grating couplers for silicon-on-insulator integrated circuits,” IEEE Photon. Technol. Lett. 19(23), 1919–1921 (2007). [CrossRef]

], the phase matching condition given in Eq. (1) can be expressed as
x2+y2koneffykoncsinθ=2πN,
(3)
where x and y are Cartesian coordinates with the grating-waveguide connection point defined as the origin and x-y axes defined in Fig. 1(a), and N is an integer indicating the order of curved grating lines. The following equation can be derived From Eq. (3):
(yNλoncsinθneff2nc2sin2θ)2(Nλoneffneff2nc2sin2θ)2+x2(Nλo(neff2nc2sin2θ))2=1.
(4)
Equation (4) indicates that the curved grating lines are a series of confocal ellipses with the focus located at the grating-waveguide connection point (origin). Thus, the optical mode can be directly focused from the grating to the waveguide, obviating the long adiabatic taper for mode conversion. Thereby the focusing-curved grating coupler has a much smaller footprint and yields a higher degree of integration than the straight-line grating coupler. By applying the simulation-optimized grating parameters into Eq. (4), the layout of the focusing-curved SWGCs can be captured. In theory, rigorous 3-D FDTD simulation should be conducted to verify the performance of the focusing-curved SWGCs. However, 3-D simulation with accurate mesh level is very time consuming in practice. Therefore, we rely on the results obtained from the 2-D simulation, which proves to have sufficient accuracy with acceptable calculation time [17

17. F. Van Laere, T. Claes, J. Schrauwen, S. Scheerlinck, W. Bogaerts, D. Taillaert, L. O’Faolain, D. Van Thourhout, and R. Baets, “Compact focusing grating couplers for silicon-on-insulator integrated circuits,” IEEE Photon. Technol. Lett. 19(23), 1919–1921 (2007). [CrossRef]

,18

18. Z. Cheng, X. Chen, C. Y. Wong, K. Xu, C. K. Fung, Y. M. Chen, and H. K. Tsang, “Focusing subwavelength grating coupler for mid-infrared suspended membrane waveguide,” Opt. Lett. 37(7), 1217–1219 (2012). [CrossRef] [PubMed]

].

3. Experiment and discussion

The focusing-curved SWGCs were fabricated on a standard silicon-on-insulator (SOI) platform (220-nm silicon on 3-µm buried oxide) with oxide cladding using EBL. In order to achieve the optimized effective RI (~1.71) in the low RI region, only one step of full-etch is conducted in the fabrication process. The material system detail is shown in Fig. 1(c). Multiple SWGCs with parameter variations around the optimal values were fabricated. The scanning electron microscopy (SEM) image of a focusing-curved SWGC is shown in Fig. 3(a), and Fig. 3(b) gives a magnified view of the interleaved subwavelength structures.
Fig. 3 SEM images of a fabricated focusing-curved SWGC. The lower-right grating region of (a) is zoomed and shown in (b).
Thanks to the focusing-curved design, the total size of this device is only 40 µm × 20 µm, which is only ~10% of the footprint of the straight-line SWGCs reported in [7

7. X. Chen, K. Xu, Z. Cheng, C. K. Y. Fung, and H. K. Tsang, “Wideband subwavelength gratings for coupling between silicon-on-insulator waveguides and optical fibers,” Opt. Lett. 37(17), 3483–3485 (2012). [CrossRef] [PubMed]

,9

9. X. Xu, H. Subbaraman, J. Covey, D. Kwong, A. Hosseini, and R. T. Chen, “Colorless grating couplers realized by interleaving dispersion engineered subwavelength structures,” Opt. Lett. 38(18), 3588–3591 (2013). [CrossRef] [PubMed]

].

A pair of input and output focusing-curved SWGCs with 127 µm pitch was connected by a short strip waveguide with negligible loss for testing. A fiber array is used to test these SWGCs on a setup similar to the setup describe in [19

19. Y. Wang, W. Shi, X. Wang, J. Flueckiger, H. Yun, N. A. F. Jaeger, and L. Chrostowski, “Fully-etched grating coupler with low back reflection,” in Proc. SPIE Photonics North (2013). [CrossRef]

]. Light is launched from a tunable laser with a spectral range of 1480-1620 nm and a resolution of 0.02 nm. A polarization controller is located after the tunable laser to adjust the polarization of the input light. The measured transmission spectrum of a focusing-curved SWGC is shown in Fig. 4.
Fig. 4 Measured transmission spectrum of the focusing-curved SWGC. Inset shows the Fabry-Perot ripples near the spectrum peak.
The 1-dB bandwidth of this SWGC is over 100 nm with a peak coupling efficiency of −6.4 dB near 1550 nm. Straight-line SWGCs with similar grating parameters were also fabricated and the measurement results have shown that the focusing-curved design introduces no performance penalties [20

20. Q. Zhong, W. Shi, Y. Wang, L. Chrostowski, and D. V. Plant, “An ultra-broadband fiber grating coupler with focusing curved subwavelength structures,” in Proc. Optical Fiber Communications (OFC) Conference (2014), paper Th2A.15. [CrossRef]

]. Compared to the simulation result shown in Fig. 2, the bandwidth meets the expectation, while the efficiency is much lower. This can be explained as follows. The fiber array used in this work has a cleaved angle of ~20°. According to Snell’s Law, when the fiber end is parallel to the grating surface, the light incident angle becomes ~30° in the air. Hence, to reach the designed incident angle (20°) as well as high coupling efficiency for operating wavelength centered near 1550 nm, the fiber array needs to be rotated, inducing an air gap between the fiber end and the chip. Extra distance is also kept to ensure the fiber array would not scratch the chip. When light propagates in this air gap, the optical mode profile becomes larger, which adds extra loss. The result shown in Fig. 2 was obtained assuming no such an air gap. If an air gap is introduced in the FDTD model, the simulated coupling efficiency would decrease and match better with the experimental result [19

19. Y. Wang, W. Shi, X. Wang, J. Flueckiger, H. Yun, N. A. F. Jaeger, and L. Chrostowski, “Fully-etched grating coupler with low back reflection,” in Proc. SPIE Photonics North (2013). [CrossRef]

]. As shown in Fig. 5, the simulated peak coupling efficiency matches with the measured value (~-6.4 dB) when the air gap is ~70 μm.
Fig. 5 Simulated peak coupling efficiency versus the air gap between the fiber and the grating surface.
According to [9

9. X. Xu, H. Subbaraman, J. Covey, D. Kwong, A. Hosseini, and R. T. Chen, “Colorless grating couplers realized by interleaving dispersion engineered subwavelength structures,” Opt. Lett. 38(18), 3588–3591 (2013). [CrossRef] [PubMed]

,21

21. V. I. Kopp, J. Park, M. Wlodawski, E. Hubner, J. Singer, D. Neugroschl, A. Z. Genack, P. Dumon, J. Van Campenhout, and P. Absil, “Two-dimensional, 37-channel, high-bandwidth, ultra -dense silicon photonics optical interface,” in Proc. Optical Fiber Communications (OFC) Conference (2014), paper Th5C.4. [CrossRef]

], this kind of extra loss can be reduced by applying index matching fluid to fill in the air gap.

It should also be noted that compared to partial-etched gratings, the full-etched gratings suffer higher loss due to larger back reflection, which is evidenced by the small ripples observed in Fig. 4. These ripples originate from the Fabry-Perot (F-P) interferometric cavity formed by a pair of input and output SWGCs, where Fresnel reflection occurs at the grating-waveguide boundaries due to the RI contrast. It can be measured from the inset of Fig. 4 that the small ripples have a free spectral range (FSR) of ~1.1 nm. This FSR value corresponds to an F-P cavity length of ~295 µm, which matches well with the total length of the waveguide connecting the pair of input and output SWGCs. Another interesting observation from Fig. 4 is that there exists a second set of F-P ripples with larger FSR, which is similar to the phenomenon reported in [8

8. Z. Cheng, X. Chen, C. Y. Wong, K. Xu, and H. K. Tsang, “Broadband focusing grating couplers for suspended-membrane waveguides,” Opt. Lett. 37(24), 5181–5183 (2012). [CrossRef] [PubMed]

]. The FSR of the second set of ripples is measured to be ~18 nm, which corresponds to an F-P cavity length of ~18 µm. This value is very close to the distance between the front and rear curves of the SWGCs, hence it can be concluded that the second set of ripples is caused by the F-P interference between the front and rear curves of the SWGCs.

It has been demonstrated that gradient-index anti-reflective subwavelength structures can effectively reduce the planar waveguide facet reflectivity [22

22. J. H. Schmid, P. Cheben, S. Janz, J. Lapointe, E. Post, and D. X. Xu, “Gradient-index antireflective subwavelength structures for planar waveguide facets,” Opt. Lett. 32(13), 1794–1796 (2007). [CrossRef] [PubMed]

]. In order to reduce the back reflection and increase the coupling efficiency, we applied similar anti-reflective structures in the focusing-curved SWGCs. As shown in Fig. 6, the modified gratings have tapered connection between high and low RI regions, instead of the sharp boundaries present in Fig. 3.
Fig. 6 SEM images of a fabricated focusing-curved SWGC with tapered grating design. The lower-right grating region of (a) is magnified and shown in (b).
The measured transmission spectrum of a focusing-curved SWGC with tapered grating design is shown in Fig. 7.
Fig. 7 Measured transmission spectrum of the focusing-curved SWGC tapered grating design. Inset shows the Fabry-Perot ripples near the spectrum peak.
Compared with the measured spectrum of the non-tapered grating design (Fig. 4), the peak coupling efficiency of the tapered grating design improves from −6.4 dB to −4.7 dB, while the 1-dB bandwidth maintains over 100 nm. From the insets of Fig. 4 and Fig. 7, it can be measured that the extinction ratios of both sets of F-P interference ripples in the tapered grating design are reduced by ~50% compared with the non-tapered grating design. These results validate the implementation of tapered subwavelength grating design can mitigate the RI contrast, thus reducing the back reflection and increasing the coupling efficiency of the focusing-curved SWGCs.

Table 1 gives a summary of the previously realized broadband SWGCs and the tapered focusing-curved SWGCs demonstrated in this work.

Table 1. Comparison of the broadband SWGCs realized to date

table-icon
View This Table
All the SWGCs are operating near 1550 nm. The devices were fabricated with full-etching on different SOI platforms (i.e., the thicknesses of top silicon and buried oxide are different). Devices in [7

7. X. Chen, K. Xu, Z. Cheng, C. K. Y. Fung, and H. K. Tsang, “Wideband subwavelength gratings for coupling between silicon-on-insulator waveguides and optical fibers,” Opt. Lett. 37(17), 3483–3485 (2012). [CrossRef] [PubMed]

] and [9

9. X. Xu, H. Subbaraman, J. Covey, D. Kwong, A. Hosseini, and R. T. Chen, “Colorless grating couplers realized by interleaving dispersion engineered subwavelength structures,” Opt. Lett. 38(18), 3588–3591 (2013). [CrossRef] [PubMed]

] are straight-line grating designs which require a 500-µm adiabatic taper. The device footprint is significantly reduced in [8

8. Z. Cheng, X. Chen, C. Y. Wong, K. Xu, and H. K. Tsang, “Broadband focusing grating couplers for suspended-membrane waveguides,” Opt. Lett. 37(24), 5181–5183 (2012). [CrossRef] [PubMed]

] and this work, where the gratings are designed in a focusing-curved geometry. The focusing-curved SWGCs demonstrated in this work show an ultra-wide 1-dB bandwidth of over 100 nm, which is the highest reported to date. However, the coupling efficiency is still not high enough to compete with the shallow-etched grating couplers [5

5. A. Mekis, S. Gloeckner, G. Masini, A. Narasimha, T. Pinguet, S. Sahni, and P. De Dobbelaere, “A grating-coupler-enabled CMOS photonics platform,” IEEE J. Quantum Electron. 17(3), 597–608 (2011). [CrossRef]

]. Further design optimization, such as apodizing the grating [23

23. X. Chen, C. Li, C. K. Y. Fung, S. M. G. Lo, and H. K. Tsang, “Apodized waveguide grating couplers for efficient coupling to optical fibers,” IEEE Photon. Technol. Lett. 22(15), 1156–1158 (2010). [CrossRef]

,24

24. R. Halir, P. Cheben, J. H. Schmid, R. Ma, D. Bedard, S. Janz, D. X. Xu, A. Densmore, J. Lapointe, and Í. Molina-Fernández, “Continuously apodized fiber-to-chip surface grating coupler with refractive index engineered subwavelength structure,” Opt. Lett. 35(19), 3243–3245 (2010). [CrossRef] [PubMed]

] and adopting a correction term of the effective RI in Eq. (3) [16

16. R. Waldhäusl, B. Schnabel, P. Dannberg, E.-B. Kley, A. Bräuer, and W. Karthe, “Efficient coupling into polymer waveguides by gratings,” Appl. Opt. 36(36), 9383–9390 (1997). [CrossRef] [PubMed]

,25

25. Y. Li, D. Vermeulen, Y. De Koninck, G. Yurtsever, G. Roelkens, and R. Baets, “Compact grating couplers on silicon-on-insulator with reduced backreflection,” Opt. Lett. 37(21), 4356–4358 (2012). [CrossRef] [PubMed]

], is required to increase the coupling efficiency of the focusing-curved SWGCs.

4. Conclusion

In summary, we have demonstrated the ultra-broadband grating couplers with focusing-curved subwavelength structures for silicon photonics optical interfaces. By applying waveguide dispersion engineered subwavelength tapered grating structures, we have experimentally achieved a 1-dB bandwidth of over 100 nm (largest reported to date) with −4.7 dB coupling efficiency near 1550 nm. With focusing-curved grating design, we have minimized the device footprint to be only 40 µm × 20 µm.

Acknowledgments

The authors thank Lumerical Solutions and Mentor Graphics for the software and design support. The devices were fabricated at the University of Washington - Washington Nanofabrication Facility (WNF), part of the National Science Foundation’s National Nanotechnology Infrastructure Network (NNIN). This work is financially supported by Natural Sciences and Engineering Research Council of Canada (NSERC) under the Silicon Electronic-Photonic Integrated Circuits (Si-EPIC) CREATE program.

References and links

1.

M. Hochberg and T. Baehr-Jones, “Towards fabless silicon photonics,” Nat. Photon. 4(8), 492–494 (2010). [CrossRef]

2.

M. Asghari and A. V. Krishnamoorthy, “Silicon photonics: Energy-efficient communication,” Nat. Photon. 5(5), 268–270 (2011). [CrossRef]

3.

M. Pu, L. Liu, H. Ou, K. Yvind, and J. M. Hvam, “Ultra-low-loss inverted taper coupler for silicon-on-insulator ridge waveguide,” Opt. Commun. 283(19), 3678–3682 (2010). [CrossRef]

4.

V. R. Almeida, R. R. Panepucci, and M. Lipson, “Nanotaper for compact mode conversion,” Opt. Lett. 28(15), 1302–1304 (2003). [CrossRef] [PubMed]

5.

A. Mekis, S. Gloeckner, G. Masini, A. Narasimha, T. Pinguet, S. Sahni, and P. De Dobbelaere, “A grating-coupler-enabled CMOS photonics platform,” IEEE J. Quantum Electron. 17(3), 597–608 (2011). [CrossRef]

6.

Z. Xiao, F. Luan, T. Y. Liow, J. Zhang, and P. Shum, “Design for broadband high-efficiency grating couplers,” Opt. Lett. 37(4), 530–532 (2012). [CrossRef] [PubMed]

7.

X. Chen, K. Xu, Z. Cheng, C. K. Y. Fung, and H. K. Tsang, “Wideband subwavelength gratings for coupling between silicon-on-insulator waveguides and optical fibers,” Opt. Lett. 37(17), 3483–3485 (2012). [CrossRef] [PubMed]

8.

Z. Cheng, X. Chen, C. Y. Wong, K. Xu, and H. K. Tsang, “Broadband focusing grating couplers for suspended-membrane waveguides,” Opt. Lett. 37(24), 5181–5183 (2012). [CrossRef] [PubMed]

9.

X. Xu, H. Subbaraman, J. Covey, D. Kwong, A. Hosseini, and R. T. Chen, “Colorless grating couplers realized by interleaving dispersion engineered subwavelength structures,” Opt. Lett. 38(18), 3588–3591 (2013). [CrossRef] [PubMed]

10.

Z. Xiao, T. Y. Liow, J. Zhang, P. Shum, and F. Luan, “Bandwidth analysis of waveguide grating coupler,” Opt. Express 21(5), 5688–5700 (2013). [CrossRef] [PubMed]

11.

R. Halir, A. Ortega-Monux, J. H. Schmid, C. Alonso-Ramos, J. Lapointe, D.-X. Xu, J. G. Wanguemert-Perez, I. Molina-Fernandez, and S. Janz, “Recent advances in silicon waveguide devices using sub-wavelength gratings,” IEEE J. Quantum Electron. 20(4), 8201313 (2014).

12.

Y. Zhang, S. Yang, A. E.-J. Lim, G.-Q. Lo, C. Galland, T. Baehr-Jones, and M. Hochberg, “A compact and low loss Y-junction for submicron silicon waveguide,” Opt. Express 21(1), 1310–1316 (2013). [CrossRef] [PubMed]

13.

https://www.lumerical.com/tcad-products/fdtd/.

14.

P. J. Bock, P. Cheben, J. H. Schmid, J. Lapointe, A. Delâge, D. X. Xu, S. Janz, A. Densmore, and T. J. Hall, “Subwavelength grating crossings for silicon wire waveguides,” Opt. Express 18(15), 16146–16155 (2010). [CrossRef] [PubMed]

15.

Y. Wang, “Grating coupler design based on silicon-on-insulator,” Master thesis, University of British Columbia (2013).

16.

R. Waldhäusl, B. Schnabel, P. Dannberg, E.-B. Kley, A. Bräuer, and W. Karthe, “Efficient coupling into polymer waveguides by gratings,” Appl. Opt. 36(36), 9383–9390 (1997). [CrossRef] [PubMed]

17.

F. Van Laere, T. Claes, J. Schrauwen, S. Scheerlinck, W. Bogaerts, D. Taillaert, L. O’Faolain, D. Van Thourhout, and R. Baets, “Compact focusing grating couplers for silicon-on-insulator integrated circuits,” IEEE Photon. Technol. Lett. 19(23), 1919–1921 (2007). [CrossRef]

18.

Z. Cheng, X. Chen, C. Y. Wong, K. Xu, C. K. Fung, Y. M. Chen, and H. K. Tsang, “Focusing subwavelength grating coupler for mid-infrared suspended membrane waveguide,” Opt. Lett. 37(7), 1217–1219 (2012). [CrossRef] [PubMed]

19.

Y. Wang, W. Shi, X. Wang, J. Flueckiger, H. Yun, N. A. F. Jaeger, and L. Chrostowski, “Fully-etched grating coupler with low back reflection,” in Proc. SPIE Photonics North (2013). [CrossRef]

20.

Q. Zhong, W. Shi, Y. Wang, L. Chrostowski, and D. V. Plant, “An ultra-broadband fiber grating coupler with focusing curved subwavelength structures,” in Proc. Optical Fiber Communications (OFC) Conference (2014), paper Th2A.15. [CrossRef]

21.

V. I. Kopp, J. Park, M. Wlodawski, E. Hubner, J. Singer, D. Neugroschl, A. Z. Genack, P. Dumon, J. Van Campenhout, and P. Absil, “Two-dimensional, 37-channel, high-bandwidth, ultra -dense silicon photonics optical interface,” in Proc. Optical Fiber Communications (OFC) Conference (2014), paper Th5C.4. [CrossRef]

22.

J. H. Schmid, P. Cheben, S. Janz, J. Lapointe, E. Post, and D. X. Xu, “Gradient-index antireflective subwavelength structures for planar waveguide facets,” Opt. Lett. 32(13), 1794–1796 (2007). [CrossRef] [PubMed]

23.

X. Chen, C. Li, C. K. Y. Fung, S. M. G. Lo, and H. K. Tsang, “Apodized waveguide grating couplers for efficient coupling to optical fibers,” IEEE Photon. Technol. Lett. 22(15), 1156–1158 (2010). [CrossRef]

24.

R. Halir, P. Cheben, J. H. Schmid, R. Ma, D. Bedard, S. Janz, D. X. Xu, A. Densmore, J. Lapointe, and Í. Molina-Fernández, “Continuously apodized fiber-to-chip surface grating coupler with refractive index engineered subwavelength structure,” Opt. Lett. 35(19), 3243–3245 (2010). [CrossRef] [PubMed]

25.

Y. Li, D. Vermeulen, Y. De Koninck, G. Yurtsever, G. Roelkens, and R. Baets, “Compact grating couplers on silicon-on-insulator with reduced backreflection,” Opt. Lett. 37(21), 4356–4358 (2012). [CrossRef] [PubMed]

OCIS Codes
(050.2770) Diffraction and gratings : Gratings
(050.6624) Diffraction and gratings : Subwavelength structures

ToC Category:
Integrated Optics

History
Original Manuscript: May 15, 2014
Revised Manuscript: June 28, 2014
Manuscript Accepted: July 11, 2014
Published: July 21, 2014

Citation
Qiuhang Zhong, Venkat Veerasubramanian, Yun Wang, Wei Shi, David Patel, Samir Ghosh, Alireza Samani, Lukas Chrostowski, Richard Bojko, and David V. Plant, "Focusing-curved subwavelength grating couplers for ultra-broadband silicon photonics optical interfaces," Opt. Express 22, 18224-18231 (2014)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-15-18224


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References

  1. M. Hochberg and T. Baehr-Jones, “Towards fabless silicon photonics,” Nat. Photon.4(8), 492–494 (2010). [CrossRef]
  2. M. Asghari and A. V. Krishnamoorthy, “Silicon photonics: Energy-efficient communication,” Nat. Photon.5(5), 268–270 (2011). [CrossRef]
  3. M. Pu, L. Liu, H. Ou, K. Yvind, and J. M. Hvam, “Ultra-low-loss inverted taper coupler for silicon-on-insulator ridge waveguide,” Opt. Commun.283(19), 3678–3682 (2010). [CrossRef]
  4. V. R. Almeida, R. R. Panepucci, and M. Lipson, “Nanotaper for compact mode conversion,” Opt. Lett.28(15), 1302–1304 (2003). [CrossRef] [PubMed]
  5. A. Mekis, S. Gloeckner, G. Masini, A. Narasimha, T. Pinguet, S. Sahni, and P. De Dobbelaere, “A grating-coupler-enabled CMOS photonics platform,” IEEE J. Quantum Electron.17(3), 597–608 (2011). [CrossRef]
  6. Z. Xiao, F. Luan, T. Y. Liow, J. Zhang, and P. Shum, “Design for broadband high-efficiency grating couplers,” Opt. Lett.37(4), 530–532 (2012). [CrossRef] [PubMed]
  7. X. Chen, K. Xu, Z. Cheng, C. K. Y. Fung, and H. K. Tsang, “Wideband subwavelength gratings for coupling between silicon-on-insulator waveguides and optical fibers,” Opt. Lett.37(17), 3483–3485 (2012). [CrossRef] [PubMed]
  8. Z. Cheng, X. Chen, C. Y. Wong, K. Xu, and H. K. Tsang, “Broadband focusing grating couplers for suspended-membrane waveguides,” Opt. Lett.37(24), 5181–5183 (2012). [CrossRef] [PubMed]
  9. X. Xu, H. Subbaraman, J. Covey, D. Kwong, A. Hosseini, and R. T. Chen, “Colorless grating couplers realized by interleaving dispersion engineered subwavelength structures,” Opt. Lett.38(18), 3588–3591 (2013). [CrossRef] [PubMed]
  10. Z. Xiao, T. Y. Liow, J. Zhang, P. Shum, and F. Luan, “Bandwidth analysis of waveguide grating coupler,” Opt. Express21(5), 5688–5700 (2013). [CrossRef] [PubMed]
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