Reversible all-optical control of optical microcavities by a self-assembled azobenzene monolayer

The time-integrated amount of data and stored information, is doubled roughly every eighteen months, and since the majority of the worlds information is stored in magnetic media, the possibility to write and retrieve information in a magnetic material at ever greater speed and with lower energy consumption, has obvious benefits for our society. Hence the seemingly simple switching of a magnetic unit, a bit, is a crucial process which defines how efficiently information can be stored and retrieved from a magnetic memory. Of particular interest here are the concepts of ultrafast magnetism and all-optical control of magnetism which have in recent decades become the basis for an intense research field. The motivation is natural; the mechanisms behind these phenomena are far from trivial and the technological implications are huge.

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Optofluidic Platform Based on Liquid Crystals in X-Cut Lithium Niobate: Thresholdless All-Optical Response

Crystals ◽

10.3390/cryst11080908 ◽

2021 ◽

Vol 11 (8) ◽

pp. 908

Author(s):

Fabrizio Ciciulla ◽

Annamaria Zaltron ◽

Riccardo Zamboni ◽

Cinzia Sada ◽

Francesco Simoni ◽

...

Keyword(s):

Liquid Crystal ◽

Liquid Crystals ◽

Light Intensity ◽

Lithium Niobate ◽

Photovoltaic Effect ◽

Optical Control ◽

Crystal Layer ◽

Liquid Crystal Layer ◽

Threshold Behaviour ◽

All Optical

In this study, we present a new configuration of the recently reported optofluidic platform exploiting liquid crystals reorientation in lithium niobate channels. In order to avoid the threshold behaviour observed in the optical control of the device, we propose microchannels realized in a x-cut crystal closed by a z-cut crystal on the top. In this way, the light-induced photovoltaic field is not uniform inside the liquid crystal layer and therefore the conditions for a thresholdless reorientation are realized. We performed simulations of the photovoltaic effect based on the well assessed model for Lithium Niobate, showing that not uniform orientation and value of the field should be expected inside the microchannel. In agreement with the re-orientational properties of nematic liquid crystals, experimental data confirm the expected thresholdless behaviour. The observed liquid crystal response exhibits two different regimes and the response time shows an unusual dependence on light intensity, both features indicating the presence of additional photo-induced fields appearing above a light intensity of 107 W/m2.

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Functional THz emitters based on Pancharatnam-Berry phase nonlinear metasurfaces

Nature Communications ◽

10.1038/s41467-020-20283-0 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Cormac McDonnell ◽

Junhong Deng ◽

Symeon Sideris ◽

Tal Ellenbogen ◽

Guixin Li

Keyword(s):

Amino Acids ◽

Linear Polarization ◽

Berry Phase ◽

Science And Technology ◽

Optical Control ◽

Biomedical Science ◽

Spin States ◽

Single Cycle ◽

All Optical ◽

Thz Waves

AbstractRecent advances in the science and technology of THz waves show promise for a wide variety of important applications in material inspection, imaging, and biomedical science amongst others. However, this promise is impeded by the lack of sufficiently functional THz emitters. Here, we introduce broadband THz emitters based on Pancharatnam-Berry phase nonlinear metasurfaces, which exhibit unique optical functionalities. Using these new emitters, we experimentally demonstrate tunable linear polarization of broadband single cycle THz pulses, the splitting of spin states and THz frequencies in the spatial domain, and the generation of few-cycle pulses with temporal polarization dispersion. Finally, we apply the ability of spin control of THz waves to demonstrate circular dichroism spectroscopy of amino acids. Altogether, we achieve nanoscale and all-optical control over the phase and polarization states of the emitted THz waves.

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