At XiO Photonics we design and manufacture optical devices based on Photonic Integrated Circuits (PICs) for visible light and near infrared applications. Photonic Integrated Circuits (PICs) are devices on which several or even many optical components are integrated; often together with electronic components. Equivalent to the introduction of electronic IC’s many years ago, Photonic IC’s (PICs) offer huge advantages. Compared to a system with discrete optical components, a system with a PIC will be simpler, more robust, more reliable, more compact and lower cost. In addition, the small form factor of PICs can enable applications which are not possible to realize with existing discrete components. PICs have been used for several years already in high volumes for optical communication applications, and this use is still increasing significantly. These applications include Fiber-to-the-home and access networks, long-haul and transport networks, and optical datacom. PICs for optical communication typically use wavelengths between 1 and 2 μm.
In applications where light is used in the visible range (400-700nm), the use of PICs is still very rare although the potential benefits can be significant. These applications include several Biophotonics applications such as confocal microscopy, flow cytometry, molecular diagnostics and spectroscopy systems. But also laser based display applications and several (food) sorting applications use visible laser light and could benefit from the use of PICs.
XiO Photonics is offering PIC-based devices for visible light applications and is focusing on OEMs who are using visible light in their products or systems. We believe that in all systems where one or multiple laser sources are used, the light transport and light processing can be optimized by using one or more PICs. To specify this optimization we work with our customers to analyze the entire path from light source to target, and review all parameters and functions to determine where using PICs would create customer benefits.
XiO Photonics uses TriPleX waveguide technology to create Photonic Integrated Circuits for visible light and near infrared applications. This section describes our technology approach in relation to other technologies and the concept of functional building blocks.
Several PIC technologies
Whereas the technology of electronic IC’s has evolved into a standard process (CMOS) using a single standard building block (transistor), the technology for photonic IC’s is more diverse. Several materials and processes are used depending on function and application. The main technologies currently used are typically categorized 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 1µm, 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 fiber coupling losses, given the refractive index match of Silica. Also referred as Planar Lightwave Technology (PLC), it became very popular in the early 2000's, 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 contras
t can be tuned depending on geometrical design. Tapers can be created that allow for efficient coupling to fibers in the low contrast regions and small bending radii allowing compact structures, in the high index contrast regions.
XiO Photonics PIC technology
For our PICs, we use TriPleX™ technology, a low loss on-chip waveguide technology which allows for control of wavelength, intensity, phase, mode size, polarization and input-output geometries. The technology is optimized for wavelengths from 400 up to 2000 nm.
We have developed a library of passive and active optical functions such as wavelength combiners, power splitters, switches, filter components, variable attenuators and modulators. These library functions can be combined in one PIC to realize the desired functionality in one robust and compact component.
Next to these basic coupler and splitter functions we have basic functions to control the intensity and phase. In combination with the couplers and splitters create the possibility to create adjustable combiners/splitters or phase shift modules.
First time right design process
All our basic function blocks are validated for both design and process. Our in-house developed software simulation tool-set has strong correlation with the wafer manufacturing process at our foundry, which enables a good reproducibility. Since most designs will be a combination of known function blocks, our simulation results will strongly correlate to the actual performance and therefore we qualify our design process as a first-time-right process. This allows us to meet customer milestones and rapidly respond to customer requirements.
Fringe Pattern Generator
As an application demonstrating how PICs can be used in corporation with free-space optics, a fringe pattern generator is developed. As the phase of the visible light can be controlled very accurately on the PIC, adjustable fringe patterns can be made and projected on a surface. The example shows the principle of a simple two channel version. But the principle can be extended to more channels, allowing even more flexibility in the number of fringes and the fringe shape and pattern.