Femto-solid Lab, Univ of Arizona develop attosecond optical switch option for electronic communications

Modern electronics are founded on switching the electrical signal by radio frequency electromagnetic fields on the nanosecond time (a billionth of a second) scale, limiting the information processing to the gigahertz speed.

Professor Enam Chowdhury and MSE graduate student and Presidential Fellow Simin Zhang, in collaboration with Hassan Research Group at the University of Arizona, have developed an alternative that uses ultrafast optical switches several orders of magnitude faster than semiconductor-based electronics to transfer and encode data. 

The team found that using ultrafast laser pulses to control the electrical signal enhanced the switching speed to sub-femtoseconds (1 femtosecond is a millionth of a nanosecond) time scale. This process offers a path to ultrafast switches and optical communication at petahertz speeds and encoding information at peta-bit /second (ten thousand times faster than current standard of 100 Gb/per second). 

Professor Chowdhury explained that using ultrafast synthesized light waveforms from an ultrafast laser synthesizer, like a synthesizer in a concert for sound, enhanced and decreased the reflectivity of the silica glass within the half-optical cycle duration of the driver laser pulse. This allowed the reflectivity modulation of the fused silica dielectric system in a strong light field to demonstrate optical switching (ON/OFF) with attosecond time resolution.

Their theoretical model suggests that the physical mechanism of this attosecond optical switching is associated with the strong laser field (pump pulse) creating transient multiphoton resonance channels, thereby fundamentally modifying the dielectric function of the normal silica glass material for few femtoseconds.

This unprecedented ultrafast reflectivity modulation was picked up by a weak probe pulse via polarization field coupling induced by the pump. Their calculation suggests that the phase shift in the reflectivity modulation is consistent with the phase-decoupling of the driver laser pulse. Complex synthesized fields of ultrashort laser pulses were used to control the optical switching signal. 

Chowdhury, Zhang and the extended collaborative team demonstrated that ultrafast laser pulses pave the way for advanced optical switches and light-based electronics, which presents a new realm for information technology, optical communications, and photonic processor technologies.

I am proud to contribute the physics theory and mathematical derivation to this fascinating research under Professor Enam Chowdhury’s supervision. The interactions between ultrafast lasers and different materials never fail to challenge me and bring my understanding to the next level. The attosecond optical switching discovery is absolutely one of the best examples, especially when I discovered that the fundamental Maxwell's equations could elegantly explain the mechanism behind it! It was a moment of great joy that reminded me of how amazingly physics and optics are tied to material science at extremes! - Simin Zhang, MSE PhD student and 2022 Presidential Fellow

Their research was detailed in a Science Advances cover story (February 24, 2023).

Alqattan, Chowdhury, Hassan, Hui, Pervak, Zhang (2023). "Ultrafast optical switching and data encoding on synthesized light fields". Science Advances, 9 (8). https://www.science.org/doi/10.1126/sciadv.adf1015