PHOTONICS | ARTICLE
Silicon Photonics, using Silicon-on- Insulator,
PIC technology for visible light Whereas the technology of electronic ICs has evolved into a standard process (CMOS) using a single standard building block (transistor), the technology for photonic ICs is more diverse. Several materials and processes are used depending on function and application. The main technologies currently used are typically categorised as Silicon Photonics, III-V Materials and Dielectrics.
Silicon Photonics, using Silicon-on-Insulator, offers passive light manipulation at a very small footprint, allowed by the relative high contrast index of silicon. The small chip size and the CMOS fabrication compatibility result in relatively low chip prices. However, no light amplification is possible at the time, meaning that integration with other technologies will be required for active functionalities. Since silicon is not transparent for wavelengths below 1 µm, Silicon Photonics cannot be used for visible light applications.
The III-V Materials technology platform offers light amplification and detection, next to passive light manipulation as filtering, splitting or interfering. In the past 20 years, this technology has been widely used by chip manufacturers to make lasers, modulators and detectors. The main materials for this platform are Indium Phosphide (InP) and Gallium Arsenide (GaAs).
The Dielectrics technology platform offers light manipulation with very low transmission and fibre coupling losses, given the refractive index match of Silica. Also referred as Planar Lightwave Technology (PLC), it became very popular in the early 2000s, allowing for a large cost reduction because of mass production of splitters and AWGs. The main materials for this platform are Silicon Dioxide or Silica
(SiO2), Silicon Nitride (Si3Ni4/SiN) and TripleX. TripleX has the advantage over the other dielectrics technologies that the contrast can be tuned depending on geometrical design. Tapers can be created that allow for efficient coupling to fibres in the low contrast regions and small bending radii allowing compact structures in the high index contrast regions.
To use PICs for visible light applications, a low loss on-chip waveguide technology is used which allows for control of wavelength, intensity, phase, mode size, polarisation and input- output geometries. The technology is optimised for wavelengths from 400 up to 2000 nm.
>> Continued on page 40
offers passive light manipulation at a very small
footprint, allowed by the relative high contrast
index of silicon. The small chip size and the
CMOS fabrication compatibility
result in relatively low chip prices.
39 | commercial micro manufacturing international Vol 7 No.4
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