Abstract
In recent years, mode-division multiplexing (MDM) has been proposed as a promising solution in order to increase the information capacity of optical networks both in free-space and in optical fiber transmission. Here we present the design, fabrication and test of diffractive optical elements for mode-division multiplexing based on optical transformations in the visible range. Diffractive optics have been fabricated by means of 3D high-resolution electron beam lithography on polymethylmethacrylate resist layer spun over a glass substrate. The same optical sequence was exploited both for input-mode multiplexing and for output-mode sorting after free-space propagation. Their high miniaturization level and efficiency make these optical devices ideal for integration into next-generation platforms for mode-division (de)multiplexing in telecom applications.
Highlights
In the last decades, several methods have been presented in order to deal with the growing worldwide demand of bandwidth and to boost the information capacity of optical networks [1]
Diffractive optics have been fabricated by means of 3D high-resolution electron beam lithography on polymethylmethacrylate resist layer spun over a glass substrate
As highlighted elsewhere [11,12,13], a limitation of orbital angular momentum (OAM)-beam sorting with log-pol transformation is represented by the slightly overlap between adjacent channels, which results into detrimental inter-channel cross-talk
Summary
Several methods have been presented in order to deal with the growing worldwide demand of bandwidth and to boost the information capacity of optical networks [1]. Different solutions have been presented and described in order to sort a set of multiplexed beams differing in their OAM content: interferometric methods [10], optical transformations [11,12,13,14,15,16,17,18], time-division technique [19], integrated silicon photonics [20], coherent detection [21], OAM-mode analyzers [22,23,24], astigmatic-mode conversion [25], rotational Doppler effect [26,27]. The possibility to replicate the fabricated optics with fast mass-production techniques, such as nano-imprint lithography [35], which allows high throughput and much lower production costs, makes these optical elements promising for integration into optical platforms for MDM
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