Riza and his group’s contributions in the field of communications include pioneering works in both RF wireless communications as well as optical communications.
Specifically, optical communications innovations have ranged from both the optical fiber domain to the freespace optical communications wireless arena. In the fiber-optic signal attenuation arena, the group has pioneered the most diverse set of variable optical attenuator (VOA) modules using optical MEMS, Acousto-Optic (AO), liquid and Liquid Crystal (LC) technologies. The group for example proposed and demonstrated the world’s first fault-tolerant variable attenuators, all-digital fiber-optic switches, spectral equalizers, and wavelength sensitive add-drop filters. These novel fiber-optic signal conditioning modules are based on a number of device technologies such as optical MEMS. LCs, AOs, and liquids. Riza invented the Hybrid MEMS/LC design for fiber-optic applications including the hybrid analog-digital design for producing world record performance VOAs. Other inventions include super low noise LC switches and low loss MEMS, LC, and hybrid MEMS-LC 3-D cross-connect switches and digital MEMS/LC tunable laser designs.
In the free-space wireless domain, Riza invented Multiplexed Optical Scanner Technology (MOST), a new method for no-moving parts three dimensional steering and imaging of light. The group also developed the most advanced theoretical models for freespace-to-Single Mode Fiber (SMF) lens coupling that has realized near zero loss SMF-to-freespace-to-SMF optical power transfer for short distances as well as for longer range optical wireless link distances, including the use of smart optical 3-D beamforming and weak lensing via the self-imaging mechanism to form ultra-low loss point-to-point optical datacom links. In addition, the group introduced and demonstrated the first smart indoor optical wireless concepts using agile 3-D optical beamforming-based reconfigurable light to produce both Line of Sight (LOS) and Non Line of Sight (NLOS) robust and high efficiency indoor optical wireless communications (today for example called Li-Fi) including its first application for data centers. Another novel optical communications method introduced by Riza and co-workers is called spatial optical CDMA that deploys spatial coding of light to provide multi-access communications using both fiber and freespace communication channels.
Riza is a pioneer in multiple simultaneous RF beams optical beamforming systems for RF wireless communications phased array antennas. His 1989 Caltech Ph.D proposed such smart beamforming systems and in particular, in 1995, he pioneered the use of optical beamforming systems for RF wireless Base-Station antennas for cellular systems including use of optical beamforming for mm-wave (today called 5G and 6G) high data rate wireless phased array antennas on a variety of fixed and mobile platforms including automobiles.