High-Flexibility Control of Structured Light with Combined Adaptive Optical Systems

Abstract

Combining the specific advantages of high-resolution liquid-crystal-on-silicon spatial light modulators (LCoS-SLMs) and reflective or refractive micro-electro-mechanical systems (MEMS) presents new prospects for the generation of structured light fields. In particular, adaptive self-apodization schemes can significantly reduce diffraction by low-loss spatial filtering. The concept enables one to realize low-dispersion shaping of nondiffracting femtosecond wavepackets and to temporally switch, modulate or deflect spatially structured beams. Adaptive diffraction management by structured illumination is demonstrated for piezo-based and thermally actuated axicons, spiral phase plates (SPPs) and Fresnel bi-mirrors. Improved non-collinear autocorrelation with angular-tunable Fresnel-bi-mirrors via self-apodized illumination and phase contrast of an SLM is proposed. An extension of the recently introduced nondiffractive Talbot effect to a tunable configuration by combining an SLM and a fluid lens is reported. Experimental results for hexagonal as well as orthogonal array beams are presented.

Structuring light by combining spatial modulation and fast angular shaping

“…Experiments were performed with a phase-only, reflective, LCoS-SLM display (type GAEA 2, HOLOEYE Photonics AG) with parallel aligned nematic (PAN) liquid crystals in combination with different types of MEMS (IMTEK) [6]. The SLM was operated at 58 Hz frame rate and works with active cooling.…”

“…High-resolution beam structuring with the SLM together with real-time imaging the MEMS surfaces enabled to adjust the illumination of the MEMS surfaces in a self-apodized mode with reduced diffraction at the edges [6]. Self-apodized light shaping in configuration Con1 is shown in Fig.…”

“…by arrays of axicons, broadband operation is enabled and temporal properties are also reconstructed (geometrical or nondiffracting Talbot effect [16]). By programming arrays of phase microaxicons on an LCoS-SLM and combining it with a piezo-actuated liquid lens of tunable focal length (configuration Con5), the nondiffracting Talbot effect was for the first time demonstrated in adaptive mode [6]. The arrays of nondiffracting subbeams were shaped from 7-fs pulses of a Ti:sapphire laser oscillator.…”

Light correcting light with nonlinear optics

“…Although phase conjugation of structured light is possible by nonlinear optics, 43 it does not correct the distortion but rather produces the negative of it, requiring a time reversal step 44 . To mitigate these drawbacks, a measurement-based approach to structured light correction is now ubiquitous, for example, using adaptive optics 45 – 49 and wavefront shaping, 50 inversion of the transmission matrix of complex channels, 51 – 53 and finding invariances that remain distortion-free 54 – 56 …”

Experimentally simulating the beam shaping capabilities of piston-type deformable mirrors using a liquid crystal spatial light modulator

“…Spatial Light Modulators (SLMs), on the other hand, have been used extensively to produce spatial modes [24][25][26][27][28] of very high-fidelity for a variety of applications. These applications range from mode-division multiplexing [29], quantum information protocols [30][31][32], advanced adaptive optics systems [33], laser material processing [34][35][36], and brightness enhancement [37]. The advantage of SLMs is that they span a wide range of wavelengths (from visible through to near-infrared and in some cases mid-infrared), while offering instantaneous and rewritable amplitude, phase and polarization control, allowing for the creation of highpurity modes [38][39][40][41][42], independent wavelength control [43], as well as hundreds of structured modes from a single device [44], ranging from LG [45,46] HG [17], IG [47], BG [48,49], azimuthal OAM modes [50,51] and non-diffracting beams [52,53].…”