Higher order mode entanglement in a type II optical parametric oscillator

Abstract

Nonclassical beams in high order spatial modes have attracted much interest but they exhibit much less squeezing and entanglement than the fundamental spatial modes, limiting their applications. We experimentally demonstrate the relation between pump modes and entanglement of first-order HG modes (HG10 entangled states) in a type II OPO and show that the maximum entanglement of high order spatial modes can be obtained by optimizing the pump spatial mode. To our knowledge, this is the first time to report this. Utilizing the optimal pump mode, the HG10 mode threshold can be reached easily without HG00 oscillation and HG10 entanglement is enhanced by 53.5% over HG00 pumping. The technique is broadly applicable to entanglement generation in high order modes.

Higher‐Order Spatially Squeezed Beam for Enhanced Spatial Measurements

“…It was difficult to obtain a well‐squeezed state because the OPA operated above the threshold, [ 33–36 ] as previously demonstrated for the generation of $$\text{H}{\text{G}_{1,0}}$$ mode. [ 37 ]…”

“…Theoretical analysis indicated that the $$\text{H}{\text{G}_{m,0}}$$ squeezed states corresponding to the optimal spatially matched superposition modes are $$\text{H}{\text{G}_{0,0}}$$, $$\ldots .\text{H}{\text{G}_{2m-2,0}}$$, $$\text{H}{\text{G}_{2m,0}}$$. [ 33,37 ] The optimal superposition and signal modes cannot resonate simultaneously in the degenerate DOPA cavity. Therefore, the optimal single spatially matched pump mode $$\text{H}{\text{G}_{2m,0}}$$ is experimentally demonstrated to generate the $$\text{H}{\text{G}_{m,0}}$$ squeezed state.…”

“…It was difficult to obtain a well-squeezed state because the OPA operated above the threshold, [33][34][35][36] as previously demonstrated for the generation of HG 1,0 mode. [37] To generate a high-quality first to fifth order squeezed state, obtaining a spatially matched pump mode was crucial to improve the nonlinear conversion efficiency. Theoretical analysis indicated that the HG m,0 squeezed states corresponding to the optimal spatially matched superposition modes are HG 0,0 , … .HG 2m−2,0 , HG 2m,0 .…”

“…Theoretical analysis indicated that the HG m,0 squeezed states corresponding to the optimal spatially matched superposition modes are HG 0,0 , … .HG 2m−2,0 , HG 2m,0 . [33,37] The optimal superposition and signal modes cannot resonate simultaneously in the degenerate DOPA cavity. Therefore, the optimal single spatially matched pump mode HG 2m,0 is experimentally demonstrated to generate the HG m,0 squeezed state.…”