Loss-Compensating Si Photonics Signal Routers

📝 Abstract

We propose and demonstrate a low-cost integrated photonic chip fabricated in a SOI foundry capable of simultaneously routing and amplifying light in a chip. This device is able to compensate insertion losses in photonic routers. It consists of standard Si/SiO2 ring resonators with Er:Al2O3 as the upper cladding layer, employed using only one simple post-processing step. This resulted in a measured on/off gain of 0.9 dB, with a footprint smaller than 0.002 mm2, and expected bit rates as high as 40Gb/s based on the resonance quality-factor. We show that the on/off gain value can be further increased using coupled rings to reach net gain values of 4 dB.

💡 Analysis

We propose and demonstrate a low-cost integrated photonic chip fabricated in a SOI foundry capable of simultaneously routing and amplifying light in a chip. This device is able to compensate insertion losses in photonic routers. It consists of standard Si/SiO2 ring resonators with Er:Al2O3 as the upper cladding layer, employed using only one simple post-processing step. This resulted in a measured on/off gain of 0.9 dB, with a footprint smaller than 0.002 mm2, and expected bit rates as high as 40Gb/s based on the resonance quality-factor. We show that the on/off gain value can be further increased using coupled rings to reach net gain values of 4 dB.

📄 Content

Loss-Compensating Si Photonics Signal Routers P. F. JARSCHEL*, M. C. M. M. SOUZA, R. B. MERLO AND N. C. FRATESCHI Device Research Laboratory, Applied Physics Department, “Gleb Wataghin” Physics Institute, University of Campinas - UNICAMP, 13083-859 Campinas-SP, Brazil *jarschel@ifi.unicamp.br Abstract: We propose and demonstrate a low-cost integrated photonic chip fabricated in a SOI foundry capable of simultaneously routing and amplifying light in a chip. This device is able to compensate insertion losses in photonic routers. It consists of standard Si/SiO2 ring resonators with Er:Al2O3 as the upper cladding layer, employed using only one simple post- processing step. This resulted in a measured on/off gain of 0.9 dB, with a footprint smaller than 0.002 mm2, and expected bit rates as high as 40Gb/s based on the resonance quality-factor. We show that the on/off gain value can be further increased using coupled rings to reach net gain values of 4 dB. References 1. S. A. Vázquez-Córdova, M. Dijkstra, E. H. Bernhardi, F. Ay, K. Wörhoff, J. L. Herek, S. M. García-Blanco and M. Pollnau, “Erbium-doped spiral amplifiers with 20 dB of net gain on silicon,” Optics Express, vol. 22, no. 21, 25993-26004 (2014). 2. G. N. v. d. Hoven, E. Snoeks, A. Polman, C. v. Dam, J. W. M. v. Uffelen and M. K. Smit, “Upconversion in Er‐ implanted Al2O3 waveguides,” Journal of Applied Physics, vol. 79, no. 3, 1258-1266 (1996) 3. D. Korn, M. Lauermann, S. Koeber, P. Appel, L. Alloatti, R. Palmer, P. Dumon, W. Freude, J. Leuthold and C. Koos, “Lasing in silicon–organic hybrid waveguides,” Nature Communications 7, 10864 (2016). 4. S. Feng, T. Lei, H. Chen, H. Cai, X. Luo and A. W. Poon, “Silicon photonics: from a microresonator perspective,” Laser Photonics Rev., vol. 6, no. 2, 145–177 (2012) 5. M. Dasic and M. A. Popovic, “Minimum Drop-Loss Design of Microphotonic Microring-Resonator Channel Add-Drop Filters,” in 20th Telecommunications Forum (TELFOR), Belgrade, (IEEE, 2012), pp. 927-930. 6. A. Yariv, “Universal relations for coupling of optical power between microresonators and dielectric waveguides,” Electronics Letters, vol. 36, no. 4, pp. 321-322 (2000). 7. R. Hui and M O’Sullivan, Fiber Optic Measurement Techniques (Academic Press, 2009) 8. E G.N. van den Hoven, J.A. van der Elsken, A. Polman, C. van Dam, K.W.M. van Uffelen and M.K. Smit, “Absorption and emission cross sections of Er3+ in Al2O3 waveguides,” Applied Optics, vol. 36, no. 15, 3338- 3341 (1997). 9. P. F. Jarschel, M. C. M. M. Souza, A. A. G. Von Zuben, A. C. Ramos, R. B. Merlo and N. C. Frateschi, “Enabling III–V integrated photonics with Er-doped Al2O3 films”, in 29th Symposium on Microelectronics Technology and Devices (SBMicro) (IEEE, 2014) 10. A. Arbabi and L. L. Goddard, “Dynamics of Self-Heating in Microring Resonators,” IEEE Photonics Journal, Vol. 4, No. 5, 1702-1711 (2012) 11. L. A. M. Barea, F. Vallini, G. F. M. de Rezende, N. C. Frateschi, “Spectral Engineering with CMOS Compatible SOI Photonic Molecules,” IEEE Photonics Journal, vol. 5, no. 6, 2202717-2202717 (2013)

1. Introduction One of the challenges faced by Silicon Photonics is maintaining the optical power along a complex integrated circuit that has a dense sequence of devices. Mimicking Erbium-Doped Fiber Amplifiers (EDFAs) functionality in the chip level is an attractive approach to help overcoming this problem. To this end, Erbium-Doped Waveguide Amplifiers (EDWAs) using Aluminum Oxide (Al2O3) as the waveguide core material have been demonstrated [1]. Such amplifiers benefit from high concentration of Er+ ions in the Al2O3 matrix, up to 100 times higher than possible in SiO2 [2]. However, the process of integrating such alumina waveguides to Silicon Photonic chips departs from CMOS technology and demands complex techniques to achieve reasonable coupling between the Si and Al2O3 waveguides. Also, this increases chip design time, demands a great deal of additional post processing steps, and reduces yield. A simpler approach consists of using a doped film as the Si waveguide top cladding instead. Since a considerable fraction of the propagating mode in silicon waveguides is outside the core, this method can allow efficient light amplification and even lasing [3]. A Silicon Photonics building block of particular interest is the ring resonator, often used to filter, route, and generally control the flow of signals [4]. However, when using add/drop ports for signal routing, insertion losses are always present [5]. It is possible to minimize this effect by changing the coupling strength between the rings and the feeding/extracting waveguides, though this leads to a decreased Quality Factor (Q) and the consequent loss of filtering resolution. In a complex photonic circuit, several of these components may be cascaded, and the added losses may give rise to information deterioration.
   In order to mitigate this insertion loss problem, one ma

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