October 11, 2023

Dr. Dorrah has received a $100,000 grant from the Optica Foundation for his proposed work entitled: “Structured light generation and sensing with metasurfaces for THz communications”. Ahmed is one of 10 recipients of the award, which provides seed money to early-career professionals to investigate impactful ideas in environment, health, and information. The award money will help build a compact wavefront sensor which can construct 2D maps of the incident THz radiation (including its intensity, phase, and polarization profiles) using a metasurface and single pixel detectors. The project takes a key step towards solving one of the open challenges in optics related to affordable, secure, and fast information processing.

This work will be done in collaboration with Dr. Paul Chevalier and Dr. Dipa Ghindani.See the Optica Foundation announcement here:
Optica Foundation awards US$1 Million to advance optics research | Optica

And the Harvard press release here:
https://seas.harvard.edu/news/2023/12/dorrah-wins-2023-optica-foundation-challenge

April 13, 2023

Displaying virtual 3D objects with light using computer-generated holography is at the heart of AR/VR and the metaverse. Current methods display virtual 3D objects by projecting many image slices, parallel to each other, and to the plane of the display — thus discretizing the 3D image in the axial direction. This limits the quality and depth perception of the scene. To tackle this limitation, we projected our desired 3D image onto sheets of light that continuously flow away from display just like arrays of lightsabers. By packing many of these structured light threads, we were able to switch on and off each pixel of the target 3D scene. This provides continuous-depth reconstruction with high axial resolution, thereby enhancing the user’s perception. Our method solves many challenges in AR/VR and volumetric displays but could also find use in other applications from light sheet microscopy and optogenetics to optical trapping and free-space communications across the entire spectrum.

This work was done in collaboration with the University of São Paulo and Brazil’s State University of Campinas. For more details, see the publication in Nature Photonics and the Harvard SEAS press release.

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 can be remotely controlled, on demand, along the optical path of the beam. Our metasurfaces are polarization-tunable and, hence, can produce different vortex profiles by switching the input polarization. This can bring new degree-of-freedom for applications such as light-matter interaction, high resolution microscopy, and sensing.

Check out the press release from Harvard SEAS and the publication in Nature Communications.

January 31, 2021

Metasurface polarization optics—platforms that can structure light’s polarization point-by-point at the nanoscale—have enabled compact polarization imaging and characterization systems. However, so far these schemes (and conventional polarization optics) can only control incoming polarization in one plane, transverse to the propagation direction. In a recent effort, we have introduced a new class of metasurface polarization optics which can perform parallel processing on incoming light over multiple planes along the propagation direction. After a single interaction with our new devices, the output light modifies its polarization state as it propagates as if encountering several virtual polarizing elements located along its path. This can address many challenges in biomedical imaging where remote control over the light's polarization over multiple penetration depths within a sample, without destroying it, is highly desired. Our new devices can also be exploited in light-matter interaction and sensing in 3D and may reveal new physical phenomena at the single photon level.

Check the press release on Harvard SEAS and the published article in Nature Photonics!