Planar Lightwave Circuits: Optical Switching and Attenuation

Date: 
Monday, October 23, 2006 (All day)
Speaker: 
Dr. Romanas Narevich
Speaker's Institution: 
NeoPhotonics

Dense wavelength division multiplexing based optical networks require ever cheaper and more complex optical components. Cheap and reliable optical components are also needed in fiber to the home field. Increasingly these optical devices are produced as a Planar Lightwave Circuits (Optical IC) using semiconductor processing techniques to grow silica waveguides on silicon wafers. Light propagates in waveguides where it is confined in the form of waveguide modes. Mach-Zehnder Inteferometer (MZI) is a basic optical circuit that serves as a building block in many optical devices: optical filters, switches and even broad-band splitters. I will discuss how the details of the MZI implementation affect the manufacturability and optical performance of the actual device. A conventional directional coupler based approach will be compared to the adiabatic mode multiplexer approach adopted in NeoPhotonics. The advantages of the adiabatic device are its process tolerance as well as insensitivity to the state of polarization of light. However even so the polarization dependence of the full MZI is non-trivial but may be explained through a simple phenomenological model. Adiabatic mode multiplexer also opens up the possibility of building a general optical filter based on mode interference in double-mode waveguide rather than light interference in two single-mode waveguides. I will present the Gain Tilt Compensator as the simplest example of such mode intereference based optical filter.