News

Electro-optical modulator

Metasurface modulators reach gigahertz speeds

June 8, 2022

Electro-optic modulators change the intensity of light in response to electric signals and have attracted much attention recently as they enable active photonics. Reaching gigahertz speeds is an important milestone that makes applications in remote sensing and communications accessible. Most demonstrations target either on-chip or fiber applications. Instead, modulators that operate on free-space light have long been very challenging to realize. Here, we show that a thin film metasurface from sub-wavelength Mie resonators enables highly efficient and ultra-compact modulation of light up...

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Achromatic inverse-designed large-area metalens

Inverse-designed cm-scale achromatic polarization-insensitive metalens

June 6, 2022

Current achromatic metalenses are typically small and bounded to tens to hundreds of micrometers in diameter – the size of a few pollen grains in a row. In this study, we demonstrate a high throughput inverse design framework that is able to design large-scale complex metasurfaces to the cm scale for the visible, which corresponds to 20 000 times the wavelengths. The inverse design framework takes advantage of machine intelligence instead of our physical intuition, and the whole process takes less than a day using a single-CPU laptop, making it accessible to the general public. The...

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Adapted polarization camera

Turning any camera into a polarization camera

March 8, 2022

In recent work, we have shown that a suitably-designed polarization-sensitive metasurface grating when paired with a conventional imaging system can serve as an "attachment" rendering it capable of polarization imaging. We describe the design rules that govern this process, and show as an example the adaptation of a simple machine vision camera with a metasurface grating.

More broadly, the work serves as a guide to using metasurface polarization gratings in optical systems more generally. These may be used as a polarization-sensitive component in a wide variety of contexts,...

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Laser frequency comb

Fast gain recovery lasers on the cover of Laser and Photonics Reviews

February 9, 2022

The peculiar physics of quantum cascade lasers has led to the discovery of new frequency comb phenomena beyond traditional ones such as harmonic states, characterized by mode skipping, time-dependent spatial hole burning, turbulent states, recently observed in ring cavities, just to mention a few. These new types of frequency combs open technological and fundamental perspectives, such as laser radio applications and deep connections with passive Kerr microresonators, which are the object of our review.

See the publication on Laser and Photonics Reviews...

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Ahmed_TAM_plates

Structuring optical vortices in 3D

November 18, 2021

Optical vortices —light structures which look like donuts and can rotate around their axis of propagation— have attracted wide interest as new means for free space communications, optical trapping, and structured illumination in microscopes. Current wavefront shaping methods, however, can only provide limited control over the vorticity and the polarization (photon’s spin) of those beams in 3D space, thus limiting their application. In this study, we introduce a new type of metasurfaces which can generate complex optical vortices in which both the vortex strength and polarization state...

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Metasurface pulse compressor

Silicon nanocoatings make ultrafast pulses ultrafaster

November 12, 2021

Transparent bulk optical components have an unfortunate tendency to stretch out ultrashort laser pulses upon transmission. This effect – also known as group delay dispersion – destroys the carefully designed time-structure of the affected pulses. In this study, we show that precisely shaped silicon nanopillars can achieve the opposite effect, compressing the laser pulses and compensating for the dispersion of other optical elements. The technology is ready to be coated onto abundantly available standard optics to allow their application in the future of ultrafaster femtosecond optics....

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EOSLM

Electro-optic spatial light modulator from a single organic layer

October 14, 2021

Spatial light modulators (SLM) provide tailored light fields for many applications. Here, we show that an SLM device can be realized from a structure as simple as a single organic electro-optic material deposited on top of interlaced gold electrodes. When we apply an electric signal across these electrodes, the refractive index of the electro-optical film changes. By nanoscale engineering of the nonlinear properties of the material and electrodes, we demonstrate modulation of the intensity of light at speeds up to 50 MHz, with tiny microwatt-level switching electrical...

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A high aspect ratio holey metalens

A high aspect ratio holey metalens

October 13, 2021

Multiple beneficial optical device properties scale with the thickness of nanostructures. For example, taller nanostructures afford a greater degree of control over multiple colors of light, expanding the range of chromatic behaviors and possibly leading to large-area achromatic metalenses. However, in conventional meta-optics, which employ free-standing nanopillars or nanofins, increasing the nanostructure height while maintaining subwavelength nanostructure spacing requires high aspect ratio structures (aspect ratio = height to width ratio), which are difficult to fabricate and work...

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