Mode conversion using optical analogy of shortcut to adiabatic passage in engineered multimode waveguides

Abstract

A shortcut to adiabatic mode conversion in multimode waveguides using optical analogy of stimulated Raman adiabatic passage is investigated. The design of mode converters using the shortcut scheme is discussed. Computer-generated planar holograms are used to mimic the shaped pulses used to speed up adiabatic passage in quantum systems based on the transitionless quantum driving algorithm. The mode coupling properties are analyzed using the coupled mode theory and beam propagation simulations. We show reduced device length using the shortcut scheme as compared to the common adiabatic scheme. Modal evolution in the shortened device indeed follows the adiabatic eigenmode exactly amid the violation of adiabatic criterion.

Engineering of fast mode conversion in multimode waveguides

“…So, we cap the maxima of κ 12 and κ 23 at 2.022 mm −1 and 1.755 mm −1 , respectively, in our simulation to account for physical realizability in fabrication and to avoid additional scattering loss resulting from large effective index modulation. To obtain a conversion efficiency ≥99%, the device length can be reduced to 3.2 mm in this numerical example, compared to 11.4 mm in the conventional STIRAP converter [15]. The invariant-based scheme fails at lengths below 3.2 mm because of the limitation we put on the maximum value of κ 12 and κ 23 .…”

“…Figure 1 shows a three-level system and the schematic of a corresponding CGPH loaded multimode waveguide, where multiplexed longperiod gratings with coupling coefficient variations along the propagation direction are used to mimic the delayed laser pulses in STIRAP. Recently, we demonstrated a shortcut to STIRAP mode conversion [15] based on transitionless quantum driving [7,8]. In this Letter, we use invariant-based inverse engineering [16] to realize a fast and robust shortcut to mode conversion without the need of direct coupling of modes jΨ 1 i and jΨ 3 i.…”

“…(7) and (8) to demonstrate mode conversion using the multimode driving scheme. We consider a 3 μm wide, five-moded polymer waveguide similar to the one in [15] for mode conversion from jΨ 1 i to jΨ 3 i. The CGPH is designed at the zero-detuning wavelength λ 0 1.55 μm and the TE polarization.…”

Short and robust directional couplers designed by shortcuts to adiabaticity

“…At the same time, the development in new ways to manipulate quantum systems with high-fidelity and in a short interaction time using the so called "shortcuts to adiabaticity" approaches [8] also sheds light on the design of novel coupled-wave devices [6,[9][10][11]. In particular, the invariant-based inverse-engineering approach [12] provides a versatile toolbox for designing short waveguide couplers [13], in terms of dynamical modes of the invariant.…”

Compact and high conversion efficiency mode-sorting asymmetric Y junction using shortcuts to adiabaticity

“…At the same time, the development in new ways to manipulate quantum systems with high-fidelity and in a short interaction time using "shortcuts to adiabaticity" [15] has inspired the design of a family of novel coupled-wave devices [16][17][18][19][20][21]. In particular, the invariant-based inverse-engineering approach [22][23][24] provides a versatile tool for the design of fast and robust waveguide couplers [19], in which the system dynamics are described using the eigenstates of the invariant I corresponding to the system Hamiltonian H. While previous works [16,17,20,21] have focused on grating-assisted mode conversion in multimode waveguides, in this Letter, we apply the shortcut to adiabaticity to design short asymmetric Y junction mode multiplexer/demultiplexer beyond the adiabatic limit.…”