Abstract
We experimentally demonstrate multiple generations of high-order orbital angular momentum (OAM) modes through third-harmonic generation in a 2D nonlinear photonic crystal. Such third-harmonic generation process is achieved by cascading second-harmonic generation and sum-frequency generation using the non-collinear quasi-phase-matching technique. This technique allows multiple OAM modes with different colors to be simultaneously generated. Moreover, the OAM conservation law guarantees that the topological charge is tripled in the cascaded third-harmonic generation process. Our method is effective for obtaining multiple high-order OAM modes for optical imaging, manipulation, and communications.
Highlights
Angular momentum is one of the most important fundamental physical quantities in both classical and quantum mechanics [1], and can be divided into spin angular momentum (SAM) and orbital angular momentum (OAM) in paraxial beams [2]
High-order OAM modes are required in various applications, such as optical manipulation and trapping [4,5,6], high-precision optical measurements [7,8], high-capacity free space, fiber-optical communications [9,10,11], and in studies of fundamental quantum physics [12,13,14]
third-harmonic generation (THG) was achieved by cascading the second-harmonic generation (SHG) and sum-frequency generation (SFG) processes through a quasi-phase matching (QPM) technique
Summary
Angular momentum is one of the most important fundamental physical quantities in both classical and quantum mechanics [1], and can be divided into spin angular momentum (SAM) and orbital angular momentum (OAM) in paraxial beams [2]. Researchers introduced nonlinear optics to achieve high-order OAM-carrying light in nonlinear optical crystals [22,23,24,25,26,27,28], metasurfaces [29] and atomic vapor [30]. In these nonlinear processes, the total OAM conservation of all interactive lights plays a very important role in the generation of high-order OAM states. We report multiple generations of high-order OAM states through cascaded THG in a 2D NPC. Our results may be useful for obtaining multiple high-order OAM modes for optical imaging, manipulation, and communications
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