InP photonic circuits using generic integration [Invited]
K. A. Williams,* E. A. J. M. Bente, D. Heiss, Y. Jiao, K. Ławniczuk, X. J. M. Leijtens,
J. J. G. M. van der Tol, and M. K. Smit
COBRA Research Institute, Eindhoven University of Technology, P.O. Box 513, Eindhoven 5600MB, The Netherlands
*Corresponding author: k.a.williams@tue.nl
Received May 18, 2015; revised July 7, 2015; accepted July 16, 2015;
posted July 23, 2015 (Doc. ID 241319); published August 28, 2015
InP integrated photonics has become a critical enabler for modern telecommunications, and is poised to revolu-
tionize data communications, precision metrology, spectrometry, and imaging. The possibility to integrate
high-performance amplifiers, lasers, modulators, and detectors in combination with interferometers within
one chip is enabling game-changing performance advances, energy savings, and cost reductions. Generic integra-
tion accelerates progress through the separation of applications from a common technology development. In this
paper, we review the current status in InP integrated photonics and the efforts to integrate the next generation of
high-performance functionality on a common substrate using the generic methodology. © 2015 Chinese Laser
Press
OCIS codes: (250.0250) Optoelectronics; (250.5300) Photonic integrated circuits.
http://dx.doi.org/10.1364/PRJ.3.000B60
1. INTRODUCTION
InP-based quaternary alloys have played an enabling role in
the critically important 1.1–1.6 μm spectral window for
fiber-optic systems. InGaAsP and InGaAlAs quaternary alloys
specifically have allowed considerable flexibility in terms of
the range of engineered bandgaps and refractive indices that
can be achieved on high-quality, low-defect-density InP sub-
strates. The ability to include a wide range of optical wave-
guide devices with different direct bandgaps on the same
substrate has led to a powerful class of InP integrated pho-
tonic circuits with both passive components such as optical
splitters, filters, multiplexers, and combiners and active
components such as optical amplifiers, lasers, modulators,
and detectors.
Integrated circuit technology improves circuit-level perfor-
mance by removing assembly complexity and variability.
As the technology matures, increasing numbers of compo-
nent-level interconnections are made at the wafer scale.
This enables sustained increases in the functionality, perfor-
mance, and reliability of circuits, while reducing their size,
power, and cost [1]. As technology matures, integrated circuit
products outperform equivalent combinations of discrete
components at the functional level. Digital coherent transceiv-
ers are a striking example [2]. Such complexity was imprac-
tical until integration technologies enabled a new class of
100 Gb∕s communications products and technologies.
New concepts for cost-effective, high-connectivity optical
packet switching circuits are similarly inconceivable without
extensive integration [3].
Performance advances have been enabled through sus-
tained technology developments for InP-based epitaxial and
fabrication processes as well as device design innovations.
Killer defect densities have been driven down to levels com-
parable with silicon CMOS in the early 1990s [4] with Infinera
reporting random killer defect densities in the range of 0.5 to
1.25 cm
−2
and functional yields as high as 70% for 440-element
circuits [5]. Improvements in reliability are becoming a key
advantage for InP integrated photonics technology as perfor-
mance yield is determined increasingly by packaging and
assembly. Strict design methodologies and tightly controlled
processes have been essential. Vertically integrated corpora-
tions such as Infinera [4] and open-access platforms such as
JePPIX [6] have adopted a methodology for InP-based pho-
tonic integrated circuits (PICs) that is similar to the CMOS
electronic integrated circuits approach: designers are given
a fixed tool set so that fabs can deliver manufacturable,
cost-effective devices. For an open-access platform, this takes
the form of a fab-specific process design kit (PDK) [7,8].
In this paper, we review the recent progress in InP inte-
grated photonic circuits exploiting generic methodologies.
In Section 2 we highlight the current status of the powerful
generic InP integration platform, which already enables laser-
and amplifier-based integrated circuits in the same chip. In
Section 3 we address the new component innovations that
are expected to feed into future platform releases. In
Section 4, we highlight longer-term research that enables fur-
ther miniaturization using our InP membrane on silicon
(IMOS) platform. In Section 5 we address opportunities for
future platform convergence with silicon electronics and
low-loss dielectric-waveguide technologies.
2. GENERIC INTEGRATION PLATFORM
The power of the InP generic integration platform derives
from the innate single-chip integration of lasers, modulators,
amplifiers, and detectors [6]. Originally the generic integration
methodology was conceived as an academic concept in the
ePIXnet network of excellence to enable many photonics ap-
plications to leverage the same efforts in technology develop-
ment. This methodology has been transferred to the industry
through the EuroPIC and Paradigm projects [9]. More than 250
custom chips have now been produced at Oclaro, Fraunhofer
B60 Photon. Res. / Vol. 3, No. 5 / October 2015 Williams et al.
2327-9125/15/050B60-09 © 2015 Chinese Laser Press