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SUMMARY:Photonic-chip-based soliton microcombs - Tobias Kippenberg: École
  Polytechnique Fédérale de Lausanne
DTSTART:20191122T133000Z
DTEND:20191122T150000Z
UID:TALK134929@talks.cam.ac.uk
CONTACT:Microsoft Research Cambridge Talks Admins
DESCRIPTION:Optical frequency combs provide equidistant markers in the IR\
 , visible and UV and have become a pivotal tool for frequency metrology an
 d are the underlying principle of optical atomic clocks\, but are also fin
 ding use in other areas\, such as broadband spectroscopy or low noise micr
 owave generation. In 2007 a new method to generate optical combs was disco
 vered based on high-Q optical microresonators. Such microresonator frequen
 cy combs (microcombs) have since then emerged as a new and widely investig
 ated method in which combs can be generated via parametric frequency conve
 rsion of a continuous wave laser inside a high Q resonator via the Kerr no
 nlinearity. Over the past years a detailed understanding of the comb forma
 tion process has been gained\, and regimes identified in which dissipative
  temporal solitons (DKS) can be generated\, that not only provide low nois
 e optical frequency combs but moreover give access to femtosecond pulses. 
 Such DKS have unlocked the full potential of soliton micro-combs by provid
 ing access to fully coherent and broadband combs and soliton broadening ef
 fects that we will describe.\nDKS have now been generated in a wide variet
 y of resonators\, including those compatible with photonic integration bas
 ed on silicon nitride (Si3N4). However\, in this platform\, DKS have been 
 only generated with repetition rates above 100 GHz\, beyond the spectral b
 ands targeted for easy signal processing by regular optoelectronic compone
 nts. This was mainly due to the high optical loss in waveguides caused by 
 the fabrication process when fabricating large geometries. In addition\, t
 he required pump power to generate the combs have been typically detriment
 al to the applications requiring full integration. We will discuss the rec
 ent progress achieved in the power requirements\, form factor and microwav
 e rate operation of the integrated microcombs. In particular we will repor
 t on the Photonic Damascene nanofabrication process that allows fabricatio
 n of large waveguides without stitching errors\, hereby providing exquisit
 e Q-factor beyond 2x107. This allowed the generation of microcombs operati
 ng in the K- and X- microwave bands that are used e.g. in radars and futur
 e 5G systems\, with power threshold compatible with silicon-based integrat
 ed lasers. Moreover\, the latest advances in the integration of the chip-s
 cale lasers and nonlinear microresonators have led to impressive demonstra
 tion of integrated\, low-power consumption microcombs that make these devi
 ces valid candidates for replacing the state-of-the-art of mode-locked las
 er-based optical frequency combs and truly provide ubiquitous chip-scale c
 omb sources.\n
LOCATION:Auditorium\, Microsoft Research Ltd\, 21 Station Road\, Cambridge
 \, CB1 2FB
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