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Fundamentals of Silicon Photonic Devices

B. Thomas Smith, Dazeng Feng, Hongbing Lei,
Dawei Zheng, Joan Fong, and Mehdi Asghari.
Main: 626-236-4500, email: tsmith[at]kotura.com
Kotura, Inc., 2630 Corporate Place, Monterey Park, CA. 91754, USA

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This paper offers a brief introduction to silicon photonics including the basic optical waveguide, passive
optical circuit performance, the addition of doped p- and n- junctions adjacent to the intrinsic silicon
waveguide to inject a current across the waveguide, free-carrier dispersion, performance of the variable
optical attenuator (VOA), and a monolithic, dual-function splitter-VOA array circuit.
Key words: silicon, photonic, electronic, optical, attenuator, PLC, VOA
1. INTRODUCTION
The use of silicon has long been established for infrared optics, such as simple lenses and windows and
long-wave detection. Today (in 2006) silicon is the material of choice for visible detection, particularly as
the imaging element in digital cameras. In some commercial cameras, the wavelength response of silicon has
even been extended to the near infrared (to 1,100nm). In addition, the vast expert base in silicon materials,
device physics, and processing equipment that has been developed for electronic microcircuits, lay in waiting
to address the rapid growth of the fiber optic infrastructure for the transport of information, video, and voice.
There is no doubt about the economic and technical advantages of silicon and it was inevitable that
silicon would be employed wherever optic fiber is deployed. Predictably, with the rise in Internet and data
transmission, the need for higher speed, broader bands, and lower cost matches all four of the material
benefits provided by silicon:
o Photonic: wide band infrared transparency,
o Electronic: low noise, high speed integrated circuits,
o Thermal: high heat conductance, and
o Structural: rugged 3-dimensional platforms and packages.