integreated optics; frequency combs; optical metrology; optical telecommunication; material loss; optical sensing; silicon nitride; photonic chip; micro-fabrication
Liu Junqiu, Raja Arslan S., Karpov Maxim, Ghadiani Bahareh, Pfeiffer Martin H. P., Du Botao, Engelsen Nils J., Guo Hairun, Zervas Michael, Kippenberg Tobias J. (2018), Ultralow-power chip-based soliton microcombs for photonic integration, in Optica
, 5(10), 1347-1347.
Pfeiffer Martin H. P., Liu Junqiu, Raja Arslan S., Morais Tiago, Ghadiani Bahareh, Kippenberg Tobias J. (2018), Ultra-smooth silicon nitride waveguides based on the Damascene reflow process: fabrication and loss origins, in Optica
, 5(7), 884-884.
Pfeiffer Martin Hubert Peter, Herkommer Clemens, Liu Junqiu, Morais Tiago, Zervas Michael, Geiselmann Michael, Kippenberg Tobias J. (2018), Photonic Damascene Process for Low-Loss, High-Confinement Silicon Nitride Waveguides, in IEEE Journal of Selected Topics in Quantum Electronics
, 24(4), 1-11.
Guo Hairun, Herkommer Clemens, Billat Adrien, Grassani Davide, Zhang Chuankun, Pfeiffer Martin H. P., Weng Wenle, Brès Camille-Sophie, Kippenberg Tobias J. (2018), Mid-infrared frequency comb via coherent dispersive wave generation in silicon nitride nanophotonic waveguides, in Nature Photonics
, 12(6), 330-335.
Pfeiffer Martin H. P., Herkommer Clemens, Liu Junqiu, Guo Hairun, Karpov Maxim, Lucas Erwan, Zervas Michael, Kippenberg Tobias J. (2017), Octave-spanning dissipative Kerr soliton frequency combs in Si_3N_4 microresonators, in Optica
, 4(7), 684-684.
Marin-Palomo Pablo, Kemal Juned N., Karpov Maxim, Kordts Arne, Pfeifle Joerg, Pfeiffer Martin H. P., Trocha Philipp, Wolf Stefan, Brasch Victor, Anderson Miles H., Rosenberger Ralf, Vijayan Kovendhan, Freude Wolfgang, Kippenberg Tobias J., Koos Christian (2017), Microresonator-based solitons for massively parallel coherent optical communications, in Nature
, 546(7657), 274-279.
Pfeiffer Martin H. P., Liu Junqiu, Geiselmann Michael, Kippenberg Tobias J. (2017), Coupling Ideality of Integrated Planar High- Q Microresonators, in Physical Review Applied
, 7(2), 024026-024026.
Integrated photonic circuits, enable to confine light on a chip and have been developed over the past two decades into a mature technology. Today three waveguide technologies based on indium phosphide (InP), silicon on insulator (SOI) and Silicon nitride (SiN) are already commercially available. For example, Infinera Inc. uses its (active) InP based photonic circuits for optical telecommunications. Intel and IBM have developed Silicon Photonics (SiP) SOI based photonic circuits for 100 Gb/s optical transceivers. Likewise, foundries such as Lionix BV (Netherlands) have commercialized SiN waveguide technology for passive applications such as phased array radar for sattelite communication or biophotonic chips. In the last years, SiN has gained significant attention due to the fact that in contrast to SOI and InP the material is suitable for nonlinear photonics. Several major US funding initiatives by DARPA have funded work related to the ability to generate on chip-optical frequency comb sources based on SiN. Such compact, chipscale combs can have a variety of applications in metrology, timekeeping and sensing as well as telecommunication and are a disruptive technology. The applicants group at EPFL has been integral part of this development and demonstrated the first low noise SiN comb sources (T. Herr et al. Nature Photonics, 2012). The regularly spaced optical lasers lines that constitute an optical frequency comb (OFC) have profoundly impacted spectroscopy, gas sensing8, and even astronomy9,10. Jointly with KIT in Germany, we demonstrated coherent communication using a SiN photonic chip based frequency combs with data rates exceeding 1Tb/s (Nature Photonics, 2014), for which our collaborator was awarded the Baden Wuerttemberg State Prize for Applied Research (100.000 Euro). Over the past year, funded by the DARPA QuASAR and PULSE program, we have shown that on chip integrated microresonator OFCs can generate ultrashort pulses using soliton formation. This discovery has been subject of an EPFL patent in the US and Europe. Using our SiN chip technology, the applicants research group is now able to fabricate SiN photonic chips that generate from a single input laser, broadband combs with 10-100 GHz mode spacing, covering > 1000 comb lines, thereby spectrally covering all the (CWDM) telecommunication bands from 1270 nm - 1640 nm at once. This technology is useful for high-speed telecommunication testing applications, in contrast to existing products that only cover a single band. Our fabrication is based on established CMOS semiconductor technology, expanded through innovative processes, allowing us to obtain >100 photonic chips, easily scalable in cost and volume. Yet, despite a favorable patent situation and a very mature fabrication process carried out at the EPFL Micro-Nanofabrication facility (CMi), a major scientific frontier that precludes commercialization is left: optical propagation losses (due to imperfections in the material and the fabrication). While in fiber optical industry the fabrication and materials of fibre drawing have been investigated and perfected, leading to losses of only of 0.5 dB/km, the loss in SiN integrated waveguides suitable for nonlinear frequency conversion has so far remainder orders of magnitude lower. Today, the best waveguides have Q-factor typically below 10 million, which implies losses of ca. 5 dB/m (10,000-fold larger than in fibers). These losses presently are the limiting factor for a commercialization of chipscale combs and impeded the foundation of an EPFL start-up company, as the current pump laser source still needs more than 1 Watt of power. A reduction of optical losses by x10 would enable a reduction of x100 in the required power-levels. In the present precoR proposal we seek to address the major outstanding fabrication and material loss challenges of SiN photonic chips: Using a recently developed and novel fabrication process (photonic Damascene process, patent application pending by EPFL) that mitigates etching SiN, in combination with material improvements adapted from optical fiber industry standard, we aim at substantially improving the quality factor to values more than 50 million. This would not only represent the first ultra high Q on chip - a major scientific advance - but moreover reduce energy consumption to a level where our devices can be immediately packaged and integrated into a system. With such sources we will demonstrate a new chipscale comb data-record, aiming at 100 Tb/s with our collaborators at KIT/ETHZ. The aim of the precoR project is to enable after the completion of the project, a startup company. The project will take place in the CMi at EPFL.