CMOS-Compatible Integrated Multiple
D. Duchesne, L. Razzari, M. Ferrera, R. Morandotti,
S. T. Chu, B.E. Little and D.J. Moss
Optical interconnects operating at 50 Gb/s were recently reported by
Intel, 1 demonstrating the enormous potential of photonics for computing, with
future chips expected to reach speeds of
1 Tb/s and beyond. However, a major
roadblock to implementing this technology is the higher cost of optics over
electronics. 2 In particular, on-chip wave-length-division-multiplexing–based interconnects require a separate laser, modulator and detector for each wavelength.
Clearly, for scalable optical telecommunications involving 64 or more wavelength-division-multiplexing (WDM) channels,
alternative approaches will be required to
reduce the number of components and
hence chip cost and complexity. Such a
solution may be provided by integrated
multiple wavelength sources. 3, 4
Recently, we exploited a high-index
glass platform to demonstrate wavelength conversion via four-wave mixing
(FWM) using CW powers as low as
5mW—the first demonstration of CW
nonlinear optics in an integrated glass
platform. 5 ;e success of this platform
was a result of a combination of very
low linear loss, negligible nonlinear
loss, a very high waveguide nonlinearity parameter (;) of 220 W- 1 km- 1 (more
than 200 times that of standard single
mode fiber) together with the use of a
microring resonator with a Q-factor of
60,000. Combined with its CMOS-compatible fabrication process, this
platform showed significant potential
to play a key role in enabling practical
integrated nonlinear optical devices for
a wide range of applications.
;e first such application was reported earlier this year, 3 where spontaneous
FWM in a very high Q-factor ring resonator was exploited to demonstrate an
integrated multiple wavelength source,
pumped by a single CW laser tuned to
a cavity resonance. ;e extremely high
= High- index glass Add = SiO2
High- index glass Ring Bus SiO2 1. 5 mm
Q-factor of the resonator (> 1 million),
combined with low linear and nonlinear loss and high nonlinearity of this
platform, enhanced the wavelength
conversion process by more than a factor
Above a threshold pump power of
about 54 m W, parametric oscillation
occurred at two resonances, the spacing
being determined by the peak in the
spontaneous FWM, or “modulational
instability,” gain profile. For the experimental conditions we used, this spacing was 52. 8 nm—more than 6 THz.
Further increasing the power resulted in
cascaded four-wave mixing, generating a
comb of wavelengths. ;e spacing of this
comb could be varied down to the cavity
free-spectral range (FSR = 200 GHz)
by changes in device design, di;erent
pumping conditions and other methods.
In addition to significant implications
for on-chip optical interconnects, this
device also has potential for applications
to metrology, sensing, computing and
D. Duchesne ( firstname.lastname@example.org), L. Razzari, M. Ferrera, and R. Morandotti are with INRS-EMT, Québec, Canada. L. Razzari is also with the
dipartimento di elettronica, Università di Pavia, via
Ferrata 1, 27100 Pavia, Italy. S. T. Chu and B.E. Little
are with Infinera Corp. in Annapolis, Md., U.S.A. D.
J. Moss is with CUDOS, School of Physics, University of Sydney, New South Wales, Australia.
1. A. Alduino et al. Integrated photonics research, silicon
and nano photonics (OSA topical meetings), PDIWI5,
2. D. A. B. Miller. “Device requirements for optical interconnects to silicon chips,” Proc. IEEE 97, 1166-85 (2009).
3. L. Razzari et al. Nature Photon. 4, 41-5 (2010).
4. J.S. Levy et al. Nature Photon. 4, 37-40 (2010).
5. M. Ferrera et al. Nature Photon. 2, 737-40 (2008).
36 | OPN Optics & Photonics News