TriPleX Planar Lightwave Circuits
TriPleXTM Planar Lightwave Circuits
TriPleXTM waveguides form a new class of integrated-optic planar lightwave circuits using low-cost, CMOS-compatible
technology. The waveguides are based on LPCVD processing of alternating Si3N4 and SiO2 layers. This technology allows
for medium and high index-contrast waveguides that exhibit low channel attenuation. In addition, TriPleXTM waveguides
are suitable for operation at wavelengths from < 500 nm through 2 µm and beyond.
Design by geometry
Channel attenuation in TriPleXTM waveguides is very low. Important waveguide characteristics, such as modal
birefringence, minimum bending radius, and insertion loss are completely dependent upon the geometry of the
waveguide layer structure. As a result, desired performance is not determined by material characteristics, but simply by
design of the waveguide geometry. This leads to a vast design freedom and extremely stable performance.
”covered I”-shape
box shape
A-shape
SiO2
2 μm
1-2 μm
1μm
Si3N4
~1μm
~100 nm
1μm
SiO2
The channel geometry of a TriPleXTM waveguide comprises a composite core having a low index inner-core of SiO2 and a
high index outer-core of Si3N4. The structure is fabricated on a conventional substrate, such as thermally oxidized silicon
or glass. A typical composite core has a cross-sectional area of approximately 1 µm2; however, each specific design
depends strongly upon its intended application. Modal characteristics are determined solely by the geometry of the
structure. And, the constituent material layers have very reproducible characteristics, as the core materials are
stoichiometric films that are deposited using Low-Pressure Chemical Vapor Deposition (LPCVD). The fabrication process
is completely CMOS-compatible. Finally, TriPleXTM waveguides can be highly cost-effective as only one photo
lithographical step is required in most cases [1-3].
Results
The table below provides characteristic operating performance for a single-mode boxed-shaped TriPleXTM waveguide,
which was designed for low propagation loss and low modal birefringence. As this data demonstrates, for such
waveguides, both attenuation and modal birefringence can be quite low. Overall loss, as well as polarization-dependent
loss, therefore, can be kept to levels normally associated with low-contrast conventional waveguides. In addition, the
coupling efficiency associated with the coupling of a TriPleXTM waveguide and an optical fiber can also be high. Such
coupling efficiency results from a close match of mode profiles in both the waveguide and the fiber.
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TriPleXTM Planar Lightwave Circuits
It should be noted that modal birefringence can be tailored over a wide range: from very small, for communications
applications, to very large, for sensor applications wherein it is desirable to strip one polarization mode completely.
Group Birefringence
Channel Attenuation Polarization Dependent Loss (PDL)
Insertion Loss (IL)
(Bg)
(dB/cm)
(dB/cm)
(no spot size converter (dB))
0.15
< 1×10-4 <
0.10
<0.10 (small core fiber - 3.6 μm MFD)
Table 1: Performance characteristics for a boxed-shaped TriPleXTM waveguide.
Applications
XiO Photonics has targeted several applications for which it believes TriPleXTM waveguide technology affords particular
advantage. These include:
Optical Beam-Forming Networks
Smart Antenna systems are being developed to enable efficient and cost-effective wireless
communication in spacecraft and airliners. In such systems, optical Beam-Forming Networks based
on an all-optical True-Time Delay offer improved performance over electronic phase-shifters [4].
The frequency independence of an all-optical True-Time Delay enables a simpler, less expensive
control system and improved overall system performance.
Reconfigurable Optical Network Components
The Reconfigurable Optical Add-Drop Multiplexer (ROADM) is considered a key network element
for achieving high system functionality at low cost [3]. ROADMs offer advantages such as: an
electro-optical (EO) conversion-free data path, monolithic integration of multiple functions, cost
savings in packaging, small device-area, low power consumption, and reconfigurability that
enables increased system flexibility.
Sensing Networks
A biochemical or chemical sensor can be readily formed by etching a sensing window in the top-
cladding of an integrated waveguide [5]. High-contrast waveguides are well-suited for IO-sensing
applications because they exhibit a very large evanescent-field component. In addition, the
integration of mode filters, interferometric principles and other optical functions needed for highly
sensitive and selective sensing is readily accomplished in high-contrast waveguides, such as
TriPleXTM waveguides.
References
[1]
U.S. Patent application nr. 10/756627-001, “Low modal birefringent waveguides and methods of fabrication”, January 2004.
[2]
R.G. Heideman, A. Mel oni, M. Hoekman, A. Borreman, A. Leinse and F. Morichetti, “Low loss, high contrast optical
waveguides based on CMOS compatible LPCVD processing: technology and experimental results”, Proceedings IEEE/LEOS
Symposium Benelux Chapter, p.71-74, Dec. 2005. Sensing”, IEEE Proceedings Photonics West, San Jose, 2006.
[3]
F. Morichetti, A. Melloni, M. Martinelli, R.G. Heideman, A. Leinse, D.H. Geuzebroek and A. Borreman. “Box shaped Dielectric
Waveguides: A new Concept in Integrated Optics”, Journal of Lightwave Technology, Vol. 25, No 9, September 2007.
[4]
C.G.H. Roeloffzen, L. Zhuang, R.G. Heideman, A. Borreman, and W. van Etten, “Ring resonator-based tunable optical delay
line in LPCVD waveguide technology”, proc. Leos Benelux Ch., 2005.
[5]
R.G. Heideman, J.A. Walker, “Surface Waveguide Technology for Telecom and Biochemical Sensing”, IEEE Proceedings
Photonics West, San Jose, 2006.
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P.O. Box 456, 7500 AH
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tel: +31 53 489 3827
fax: +31 53 489 3601
