Donghwan Ahn
Massachusetts Institute of Technology
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Featured researches published by Donghwan Ahn.
Optics Express | 2007
Donghwan Ahn; Ching-yin Hong; Jifeng Liu; Wojciech P. Giziewicz; Mark Beals; Lionel C. Kimerling; Jian Chen; Franz X. Kärtner
Photonic systems based on complementary metal oxide semiconductor (CMOS) technology require the integration of passive and active photonic devices. The integration of waveguides and photodetector is one of the most important technologies. We report a Ge p-i-n photodetector that is monolithically integrated with silicon oxynitride and silicon nitride waveguides. All processes and materials are CMOS compatible and can be implemented in the current integrated circuit process technology. The small size of the devices results in low absolute dark current. The waveguidecoupled Ge devices show high efficiency (~90%) over a wide range of wavelengths well beyond the direct band gap of Ge, resulting in a responsivity of 1.08 A/W for 1550 nm light. The device speed of 7.2 GHz at 1V reverse bias is strongly affected by the capacitance of the probe pads. The high-performance of the devices at low voltage ( </= 1V) facilitates the integration with CMOS circuits.
Proceedings of SPIE, the International Society for Optical Engineering | 2006
Lionel C. Kimerling; Donghwan Ahn; Alyssa B. Apsel; Mark Beals; Daniel N. Carothers; Y.K. Chen; T.J. Conway; Douglas M. Gill; M.J. Grove; Ching-yin Hong; M. Lipson; J. Liu; J. Michel; Dong Pan; Sanjay Patel; Andrew Pomerene; Mahmoud Rasras; Daniel K. Sparacin; K.Y. Tu; A. E. White; Chee Wei Wong
The optical components industry stands at the threshold of a major expansion that will restructure its business processes and sustain its profitability for the next three decades. This growth will establish a cost effective platform for the partitioning of electronic and photonic functionality to extend the processing power of integrated circuits. BAE Systems, Lucent Technologies, Massachusetts Institute of Technology, and Applied Wave Research are participating in a high payoff research and development program for the Microsystems Technology Office (MTO) of DARPA. The goal of the program is the development of technologies and design tools necessary to fabricate an application-specific, electronicphotonic integrated circuit (AS-EPIC). As part of the development of this demonstration platform we are exploring selected functions normally associated with the front end of mixed signal receivers such as modulation, detection, and filtering. The chip will be fabricated in the BAE Systems CMOS foundry and at MITs Microphotonics Center. We will present the latest results on the performance of multi-layer deposited High Index Contrast Waveguides, CMOS compatible modulators and detectors, and optical filter slices. These advances will be discussed in the context of the Communications Technology Roadmap that was recently released by the MIT Microphotonics Center Industry Consortium.
Proceedings of SPIE, the International Society for Optical Engineering | 2008
Mark Beals; J. Michel; Jifeng Liu; Donghwan Ahn; Daniel K. Sparacin; Rong Sun; Ching-yin Hong; Lionel C. Kimerling; Andrew Pomerene; Daniel N. Carothers; James Beattie; Anthony Kopa; Alyssa B. Apsel; Mahmoud Rasras; Douglas M. Gill; Sanjay Patel; K.Y. Tu; Y.K. Chen; A. E. White
Multilevel thin film processing, global planarization and advanced photolithography enables the ability to integrate complimentary materials and process sequences required for high index contrast photonic components all within a single CMOS process flow. Developing high performance photonic components that can be integrated with electronic circuits at a high level of functionality in silicon CMOS is one of the basic objectives of the EPIC program sponsored by the Microsystems Technology Office (MTO) of DARPA. Our research team consisting of members from: BAE Systems, Alcatel-Lucent, Massachusetts Institute of Technology, Cornell University and Applied Wave Research reports on the latest developments of the technology to fabricate an application specific, electronic-photonic integrated circuit (AS_EPIC). Now in its second phase of the EPIC program, the team has designed, developed and integrated fourth order optical tunable filters, both silicon ring resonator and germanium electro-absorption modulators and germanium pin diode photodetectors using silicon waveguides within a full 150nm CMOS process flow for a broadband RF channelizer application. This presentation will review the latest advances of the passive and active photonic devices developed and the processes used for monolithic integration with CMOS processing. Examples include multilevel waveguides for optical interconnect and germanium epitaxy for active photonic devices such as p-i-n photodiodes and modulators.
international conference on group iv photonics | 2006
J. Liu; Dong Pan; Samerkhae Jongthammanurak; Donghwan Ahn; Ching-yin Hong; Mark Beals; Lionel C. Kimerling; J. Michel; Andrew Pomerene; Craig M. Hill; M. Jaso; Kun-Yii Tu; Y.K. Chen; Sanjay Patel; Mahmoud S. Rasras; Alice E. White; D.M. Gill
We demonstrate a fully CMOS processed Ge p-i-n photodetector integrated with a Si waveguide on a SOI platform with a high responsivity of 1.0 A/W at lambda=1520 nm, and a 3 dB bandwidth of >4.5 GHz measured at lambda=1550 nm
Journal of Applied Physics | 2011
Donghwan Ahn; Lionel C. Kimerling
We studied evanescent wave coupling behavior between low index-contrast upper-level waveguides and thin-film Si and Ge photodetectors on SOI and germanium-on-insulator (GOI) substrates, respectively. We present a simple and intuitive leaky-mode phase-matching model using a ray-optics approach to determine the conditions for efficient coupling, both in 2D and 3D structures. It is shown that the presence of leaky modes that are phase-matched between the waveguide and the Si or Ge photodetector layer is the key condition for efficient coupling. Our approach was compared to other methods, such as finite-difference time domain (FDTD)/beam propagation method (BPM) and mode analysis. We report that, depending on the way a waveguide photodetector device is designed, waveguide-to-photodetector coupling efficiency may or may not be critically sensitive to design parameters, such as the photodetector layer thickness. As an example, the stark contrast of coupling behavior in the two most popular Ge photodetector stru...
2006 Optics Valley of China International Symposium on Optoelectronics | 2006
J. Liu; Donghwan Ahn; Ching-yin Hong; Dong Pan; Samerkhae Jongthammanurak; Mark Beals; Lionel C. Kimerling; J. Michel; Andrew Pomerene; Craig M. Hill; M. Jaso; K.Y. Tu; Y.K. Chen; Sanjay Patel; Mahmoud Rasras; A. E. White; Douglas M. Gill
We present selectively grown Ge p-i-n photodetectors coupled to high index contrast Si(core)/SiO2(cladding) waveguides on a silicon-on-insulator (SOI) platform. Two coupling schemes, namely butt-coupling and vertical coupling, were demonstrated in this study. With the butt-coupling scheme we have achieved a high responsivity of 1.0 A/W at 1520 nm and a 3 dB bandwidth greater than 4.5 GHz at 1550 nm. With the vertical coupling scheme, where the light couples from a Si waveguide evanescently to the Ge detector on top of it, a responsivity of 0.22 A/W and a 3 dB bandwidth of ~1.5 GHz have been demonstrated at 1550 nm. The devices were fabricated on a standard 180 nm industrial complementary metal oxide semiconductor production (CMOS) line, and can be integrated with CMOS circuitry for electronic and photonic integrated circuits
Journal of Lightwave Technology | 2010
Donghwan Ahn; Lionel C. Kimerling
We have fabricated vertical p-i-n silicon photodetectors that are monolithically integrated with compact silicon-oxynitride channel waveguides. By comparing the evanescent coupling from low index-contrast waveguides and compact, high index-contrast waveguides, the dependence of evanescent coupling behavior on the waveguide index and geometry designs was analyzed. The effects of fabrication variations in the coupling structure have been studied and it was found that an offsetting step in the waveguide can help compensate for the mode mismatch at the transition interface from the input bus waveguide to the waveguide on top of the photodetector. Finally, we present a design map, built by drawing the evanescent coupling rate contour lines in the waveguide design space, which well predicts the evanescent coupling trends.
Proceedings of SPIE, the International Society for Optical Engineering | 2007
J. Liu; Donghwan Ahn; Daniel K. Sparacin; Rong Sun; Ching-yin Hong; Wojciech P. Giziewicz; Mark Beals; Lionel C. Kimerling; A. Kopa; Alyssa B. Apsel; Mahmoud Rasras; Douglas M. Gill; Sanjay Patel; K. Y. Tu; Y. K. Chen; A. E. White; Andrew Pomerene; Daniel N. Carothers; M. J. Grove
The complete integration of photonic devices into a CMOS process flow will enable low cost photonic functionality within electronic circuits. BAE Systems, Lucent Technologies, Massachusetts Institute of Technology, Cornell University, and Applied Wave Research are participating in a high payoff research and development program for the Microsystems Technology Office (MTO) of DARPA. The goal of the program is the development of technologies and design tools necessary to fabricate an application specific, electronic-photonic integrated circuit (AS-EPIC). The first phase of the program was dedicated to photonics device designs, CMOS process flow integration, and basic electronic functionality. We will present the latest results on the performance of waveguide integrated detectors, and tunable optical filters.
Applied Physics Letters | 2009
Donghwan Ahn; Ching-yin Hong; Lionel C. Kimerling
A waveguide-integrated photodetector provides a small-footprint, low-capacitance design that overcomes the bandwidth-efficiency trade-off problem of free space optics. High performance silicon devices are critical to the emergence of electronic-photonic integrated circuits on the complementary metal oxide semiconductor platform. We have fabricated vertical p-i-n silicon photodetectors that are monolithically integrated with compact silicon oxynitride channel waveguides. We report over 90% coupling efficiency of 830 nm light from the silicon oxynitride (SiOxNy) channel waveguide to the silicon photodetector. We analyze the dependence of coupling on waveguide index by comparing coupling from low index-contrast waveguides and high index-contrast waveguides.
international conference on group iv photonics | 2007
Jifeng Liu; Donghwan Ahn; Samerkhae Jongthammanurak; Dong Pan; Ching-yin Hong; Mark Beals; Lionel C. Kimerling
We present waveguide-coupled, Ge-based photodetectors and electro-absorption (EA) modulators for active Si integrated photonics. These devices offer high optoelectronic performance and compatibility with Si CMOS process.