Time reversed optical waves by arbitrary vector spatiotemporal field generation

Abstract

Lossless linear wave propagation is symmetric in time, a principle which can be used to create time reversed waves. Such waves are special “pre-scattered” spatiotemporal fields, which propagate through a complex medium as if observing a scattering process in reverse, entering the medium as a complicated spatiotemporal field and arriving after propagation as a desired target field, such as a spatiotemporal focus. Time reversed waves have previously been demonstrated for relatively low frequency phenomena such as acoustics, water waves and microwaves. Many attempts have been made to extend these techniques into optics. However, the much higher frequencies of optics make for very different requirements. A fully time reversed wave is a volumetric field with arbitrary amplitude, phase and polarisation at every point in space and time. The creation of such fields has not previously been possible in optics. We demonstrate time reversed optical waves with a device capable of independently controlling all of light’s classical degrees of freedom simultaneously. Such a class of ultrafast wavefront shaper is capable of generating a sequence of arbitrary 2D spatial/polarisation wavefronts at a bandwidth limited rate of 4.4 THz. This ability to manipulate the full field of an optical beam could be used to control both linear and nonlinear optical phenomena.

Photonic matrix multiplication lights up photonic accelerator and beyond

“…A more powerful PLC-MVM for unitary spatial mode manipulation was proved with multiplane light conversion (MPLC) 44 , 45 , in which the input/output vectors are distributed in the whole two-dimensional plane, and the scale is proportional to . Afterwards, the MPLC technique was widely used in various fields, such as for all-optical machine learning 46 – 48 , the Laguerre-Gaussian or orbital angular momentum (OAM) mode sorter 49 , 50 , the photonic Ising machine 51 , 52 , time-reversed optical waves 53 , optical logic operations 54 , optical encryption and perceptrons 55 , 56 , optical hybrid 57 and neuromorphic optoelectronic computing 58 . Although MPLC can achieve ultralarge-scale MVMs, the devices are bulky, and the reprogramming speed for weight encoding is still limited.…”

“…As shown in Fig. 3b , this powerful mode sorter was further used to create time-reversed waves, where all classical linear physical dimensions of light were simultaneously controlled independently 53 . This device can independently address the amplitude, phase, spatial mode, polarization and spectral/temporal degrees of freedom simultaneously through the programming of the SLM.…”

“… a Laguerre-Gaussian mode sorter 49 . b Arbitrary vector spatiotemporal field generation 53 . c Optical encryption 55 .…”

“…b Reprinted from ref. 53 with permission from Springer Nature: Nature Communications. c Reprinted from ref.…”

Generation and Detection of Structured Light: A Review

“…Two timedelayed, collinear IR pulses with the same wavelength (800 nm), but different OAM values, are focused on an argon gas target (HHG medium) to produce harmonic beams with selftorque [14]. Shown in Figure 10B is a powerful setup for the generation of arbitrary vector spatiotemporal light fields with arbitrary amplitude, phase, and polarization at every point in space and time [100]. First, the light output from a sweptwavelength laser with two orthogonal polarizations propagates through a pulse shaper so that it is redistributed among the spatial and spectral/temporal domains.…”