Multiple beam splitter using volumetric multiplexed Fresnel zone plates fabricated by ultrafast laser-writing

Abstract

A simple approach to producing a 1×N beam splitter is demonstrated by fabricating a volumetric multiplex phase Fresnel zone plate in bulk transparent material. This comprised four layers of zone plates created in borosilicate glass by femtosecond laser direct-writing, each shifted laterally relative to the illumination axis, creating four separate beamlets. Since the power transmitted in each beamlet is proportional to the diffraction efficiency of the corresponding zone plate, the power ratios can be customized by adjusting the fabrication parameters of each layer. This approach demonstrates the potential of femtosecond laser direct-writing for the fabrication of complex optical elements in transparent media as components of integrated monolithic photonic devices.

Femtosecond Laser Fabrication of Refractive/Diffractive Micro‐Optical Components on Hard Brittle Materials

“…Volume FZPs were prepared by laser‐induced refractive index change or void generation in fused silica, [ 105 ] sapphire, [ 106 ] borosilicate glass, [ 107 ] and fluoroaluminate glass. [ 108 ] Most of the initial studies focused on fused silica materials.…”

Advances in femtosecond laser processing of optical material for device applications

“…Since then, the fabrication and light‐guiding efficiency has been significantly improved to increase the possibility of a practical use of the technique. In this period, more complicated structures including waveguide arrays, couplers, stacked diffractive optics, and integrated optical devices were demonstrated …”

“…Diffractive optical elements including grating and diffractive lenses, another passive photonic structure, are demonstrated . For the fabrication of diffractive elements, the increase in low diffraction efficiency due to the low‐induced refractive index change proved to be a challenge.…”

“…In this period, more complicated structures including waveguide arrays, couplers, stacked diffractive optics, and integrated optical devices were demonstrated. [22][23][24] In recent years, this technique has matured to achieve sufficient reliability for commercialization of directly laser written components which are not available with current fiber-optic technology. A few start-up companies are established based on unique business areas such as fiber 3D interconnect and 3D fan-out multiplexers toward the future markets in the fields including optical networking, quantum communication, and optical sensing.…”

“…Three-dimensional multiplexer was demonstrated by Gross et al 35 , and uniformly created waveguide arrays were also exploited as base components for discrete optics and quantum circuits which was successfully demonstrated by Szameit et al [36][37][38][39][40] Waveguide Bragg grating has intensively investigated by several groups including Zhang, et al and Brown, et al [41][42][43][44] Diffractive optical elements including grating and diffractive lenses, another passive photonic structure, are demonstrated. [11][12][13][14]23 For the fabrication of diffractive elements, the increase in low diffraction efficiency due to the low-induced refractive index change proved to be a challenge. Nishii, et al demonstrated a multilevel diffractive phase lens to overcome the low efficiency of their prior work which was an amplitude binary lens generated by laser ablation.…”