Geometrical representation of coherent tunneling process in two-waveguide and three-waveguide coupler

Abstract

We propose an identical geometrical representation scheme for both Landau-Zener (LZ) tunneling process in twowaveguide coupler with a cubically bent structure and stimulated Raman adiabatic passage (STIRAP) in three-waveguide coupler, similar to the geometrical representation of sum frequency process. The results show that although the twowaveguide coupler with a cubically bent axis has not aperiodic structure, it acts as a chirped quasi-phase-matching (QPM) grating and corrects the relative phase between the two supermodes in the curved coupler system. We present a scheme about how to choose the parameters to design the curved beam splitter.

One-way acoustic beam splitting in spatial four-waveguide couplers designed by adiabatic passage

“…Note that there are numerous achievements in the design of optical or terahertz adiabatic two-WG couplers [11,[37][38][39]. Compared with adiabatic two-WG couplers, the four-WG coupler proposed in our work has an advantage of one-way propagation feature owing to the utilization of dark state.…”

High-fidelity resonant tunneling passage in three-waveguide system

“…It was used first in nuclear magnetic resonance technique. [1] Then, various AP techniques have been presented, such as Stark-chirped rapid adiabatic passage, [2,3] superadiabatic passage, [4] and stimulated Raman adiabatic passage (STIRAP), [5][6][7] to name a few. Generally, the population transfer efficiencies of all AP schemes are close to (but less than) unity.…”

High-performance waveguide-integrated Ge/Si avalanche photodetector with small contact angle between selectively epitaxial growth Ge and Si layers*

“…[3] Therefore, most of these photodetectors have been studied. [4][5][6] In recent years, Ge/Si separate absorption, charge, and multiplication (SACM) APDs have become promising candidates for future digital communication because they combine efficient optical absorption of Ge at communication wavelengths with outstanding electron multiplication properties of Si. [7][8][9] Moreover, waveguide coupling structure overcomes the trade-off between absorption efficiency and bandwidth by a long horizontal optical path to absorb most of the photons and a short vertical carrier collection path to minimize carrier transit-time.…”