Abstract:Optical beam steering (BS) has multiple applications in fields like target seeking and tracking, optical tweezers, billboard displays and many others. In this work, a two-dimensional beam deflector based on blaze gratings is presented. Phase-only 1D blaze gratings have been prepared using maskless Direct Laser Writing (DLW) resulting in high-resolution structures in indium-tin oxide (ITO) coated glass wafers. The device is composed of two identical 1D liquid crystal (LC) cells cascaded orthogonally back-to-bac… Show more
“…Topological charges in the range of -36 to 36 can be achieved using 2𝜋 phase wrapping. However, the higher topologies (positive or negative) employ less electrodes to generate each 2π phase profile; hence the diffraction efficiency is reduced like in any conventional discrete linear diffraction grating [38].…”
The manufacturing and characterization of a large-size 72-electrode liquid crystal-based reconfigurable spiral phase plate (SPP) is presented. The SPP is addressed by a custom-made driver with 72 independent channels, which allows for the generation of any arbitrary integer or fractional optical vortex beam with topological charges ranging from –36 to +36. The 25 mm diameter device is fabricated using direct laser writing, leading to a fill factor over 99%. The device performance and flexibility exceed any previous transparent reconfigurable SPP in terms of size, tuning range and fill factor. The device and the light path have been simulated using the angular spectrum propagation method, showing excellent correspondence.
“…Topological charges in the range of -36 to 36 can be achieved using 2𝜋 phase wrapping. However, the higher topologies (positive or negative) employ less electrodes to generate each 2π phase profile; hence the diffraction efficiency is reduced like in any conventional discrete linear diffraction grating [38].…”
The manufacturing and characterization of a large-size 72-electrode liquid crystal-based reconfigurable spiral phase plate (SPP) is presented. The SPP is addressed by a custom-made driver with 72 independent channels, which allows for the generation of any arbitrary integer or fractional optical vortex beam with topological charges ranging from –36 to +36. The 25 mm diameter device is fabricated using direct laser writing, leading to a fill factor over 99%. The device performance and flexibility exceed any previous transparent reconfigurable SPP in terms of size, tuning range and fill factor. The device and the light path have been simulated using the angular spectrum propagation method, showing excellent correspondence.
“…The 72 pixels enable the generation of 36 positive or 36 negative different topological charges. The electrodes shape eases a fan out to the periphery of the cell, where they are connected to an in-house developed electronic driver [31]. Connections between the electronic driver and the LC cell are carried out using a flex connector attached to the periphery of the substrate with an Anisotropic Conductive Adhesive (Hitachi Chemical, Japan).…”
A transmissive adaptable optical setup to generate a range of perfect vortex beams (PVBs) carrying different topological charges (TC) without using moving parts is presented. The setup is composed of an ad hoc transparent reconfigurable liquid crystal (LC) spiral phase plate (SPP), a refractive axicon and a convergent refractive lens. The LC SPP electrodes are manufactured ablating indium-tin oxide (ITO) glass substrates using direct laser writing (DLW) resulting in a very high fill factor device. In-house tailored electronics drive the 72 LC SPP electrodes giving rise to 72 different configurations with orbital angular momentum. In this work, the generation of PVBs with 36 positive or 36 negative TCs using this optical setup is accomplished.
“…To increase the output angle (α) for a given wavelength (λ), the slope of the cone may be increased, corresponding to decreasing the blazed grating pitch (Δ) (Fig. 1 b,d) similar to a linear diffractive blaze grating 38 . Figure 1 On the left, representation of two convergent blazed axicons wrapped over a 2π range.…”
A transparent variable diffractive spiral axicon (DSA) based on a single LC cell is presented. The manufactured DSA can be switched between 24 different configurations, 12 convergent and 12 divergent, where the output angle is varied as a function of the applied topological charge. The active area of the device is created using a direct laser writing technique in indium-tin oxide coated glass substrates. Liquid crystal is used to modulate the phase of the incoming beam generating the different DSA configurations. The DSA consists in 24 individually driven transparent spiral shaped electrodes, each introducing a specific phase retardation. In this article, the manufacture and characterization of the tunable DSA is presented and the performance of the DSA is experimentally demonstrated and compared to the corresponding simulations.
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