CMOS Compatible Optical Leaky Wave Antennas (OLWAs) and Devices

Sponsored by NSF – ECCS

Proposed Scientific and Technological Advance

The proposed research will lead to various advances from both the theoretical and application aspects. The advances, all inter-related, are itemized and discussed in the following.

a) Optical leaky wave antennas: Optical antennas are a very recent subject of growing interest. During this research, we develop theory and applications of LW optical antennas, yet to be explored in the optical domain. The groundbreaking nature of the proposed research indeed comes from the fact that it utilizes dielectric waveguides with semiconductor perturbations to develop optical antennas. In particular we are interested in (a) developing theory and design of OLWAs based on silicon nitride waveguides with silicon perturbations and the processing techniques suitable for optics; and in (b) making the first experiment that will be comparatively checked against the theory of OLWAs.

b) Electronic radiation control of OLWAs: The second transformative nature of the research comes from the introduction of novel electronic radiation control. The pointing direction of the beam can be designed by choosing a suitable perturbation period (made of silicon) and waveguide propagation constant (effective refractive index). Using an electronic control of the permittivity and losses in the Si perturbations, one may control the LW propagation constants (phase and attenuation) and thus properly modify the beam width and pointing angle . These parameters may be changed for the whole length of the perturbations in the x direction (periodic perturbations) by using a single electronic control. An OLWA integrated in an optical resonator will provide the necessary radiated power control. The proposed research will be implemented by using Silicon Nitride waveguides with Si perturbations. It is important to note that our design is on a Si device layer which can accommodate on chip CMOS electronic control units. Though general integration of this Si device with other electronics is not the direct goal of the proposed research, full opto-electronic integration is possible.

c) Controlled radiation of light extracted from (or coupled into) an integrated waveguide: Since this is an optical antenna, by definition the radiation extraction from a feed (in this case a waveguide) has to be efficient. Therefore, the waveguide mode is matched to the radiation in space by using an OLWA. This results in a very narrow beam of light coming out of the integrated device, in a controlled fashion so as to have a specific intensity, beamwidth and directivity. By reciprocity, the same design can be used to couple very efficiently light coming from specific direction (an accurate alignment is necessary) to the integrated waveguide. Though not directly investigated here, optical fibers-integrated waveguide couplers can be designed by using the OLWA or alternative similar designs.

d) Modulators and switches with high extinction ratio: Our research leads to the possibility to control the amount of power density radiated in a narrow beam. Modulators and switches envisaged with the proposed technique will offer extinction ratios higher than the general ones available, at a low cost because of the silicon implementation.

Impact on society and technology

The successful outcome of this project will improve the performance of devices, such as switches, electro-optic modulators, used in the telecommunications and, in a longer term, will also result in better optical fiber-integrated optics couplers. The vast Si manufacturing infrastructure throughout the world can enable high volume production of these devices and provide low cost solution to consumers nationwide. Furthermore, the possibility to establish multi control of the semiconductor sections in our OLWA will also pave the path for electronically controlled near field sensors to detect subwavelength particles, all in a CMOS integrated technology. This project will imply a tremendous advance in the field of very directive optical antennas and all their possible applications ranging from optical communications to portable submicron imaging and optical sensing.