74 research outputs found
Universal linear optical operations on discrete phase-coherent spatial modes
Linear optical operations are fundamental and significant for both quantum
mechanics and classical technologies. We demonstrate a non-cascaded approach to
perform arbitrary unitary and non-unitary linear operations for N-dimensional
phase-coherent spatial modes with meticulously designed phase gratings. As
implemented on spatial light modulators (SLMs), the unitary transformation
matrix has been realized with dimensionalities ranging from 7 to 24 and the
corresponding fidelities are from 95.1% to 82.1%. For the non-unitary
operators, a matrix is presented for the tomography of a 4-level quantum system
with a fidelity of 94.9%. Thus, the linear operator has been successfully
implemented with much higher dimensionality than that in previous reports. It
should be mentioned that our method is not limited to SLMs and can be easily
applied on other devices. Thus we believe that our proposal provides another
option to perform linear operation with a simple, fixed, error-tolerant and
scalable scheme
Programmable coherent linear quantum operations with high-dimensional optical spatial modes
A simple and flexible scheme for high-dimensional linear quantum operations
on optical transverse spatial modes is demonstrated. The quantum Fourier
transformation (QFT) and quantum state tomography (QST) via symmetric
informationally complete positive operator-valued measures (SIC POVMs) are
implemented with dimensionality of 15. The matrix fidelity of QFT is 0.85,
while the statistical fidelity of SIC POVMs and fidelity of QST are ~0.97 and
up to 0.853, respectively. We believe that our device has the potential for
further exploration of high-dimensional spatial entanglement provided by
spontaneous parametric down conversion in nonlinear crystals
One-shot ultraspectral imaging with reconfigurable metasurfaces
One-shot spectral imaging that can obtain spectral information from thousands
of different points in space at one time has always been difficult to achieve.
Its realization makes it possible to get spatial real-time dynamic spectral
information, which is extremely important for both fundamental scientific
research and various practical applications. In this study, a one-shot
ultraspectral imaging device fitting thousands of micro-spectrometers (6336
pixels) on a chip no larger than 0.5 cm, is proposed and demonstrated.
Exotic light modulation is achieved by using a unique reconfigurable
metasurface supercell with 158400 metasurface units, which enables 6336
micro-spectrometers with dynamic image-adaptive performances to simultaneously
guarantee the density of spectral pixels and the quality of spectral
reconstruction. Additionally, by constructing a new algorithm based on
compressive sensing, the snapshot device can reconstruct ultraspectral imaging
information (/~0.001) covering a broad (300-nm-wide)
visible spectrum with an ultra-high center-wavelength accuracy of 0.04-nm
standard deviation and spectral resolution of 0.8 nm. This scheme of
reconfigurable metasurfaces makes the device can be directly extended to almost
any commercial camera with different spectral bands to seamlessly switch the
information between image and spectral image, and will open up a new space for
the application of spectral analysis combining with image recognition and
intellisense
Metasurface-Based Free-Space Multi-port Beam Splitter with Arbitrary Power Ratio
A beam splitter (BS) is one of the most critical building blocks in optical
systems. Despite various attempts of flat-type BSs to miniaturize the
conventional cube BS reported, it remains a challenge to realize an ultrathin
optical BS with multi-port output, non-uniform splitting ratio and steerable
outgoing directions. Herein, we have demonstrated a free-space optical
multi-port beam splitter (MPBS) based on a polarization-independent
all-dielectric metasurface. By applying an optimized phase-pattern paradigm via
a gradient-descent-based iterative algorithm to amorphous silicon (a-Si)
metasurfaces, we have prepared a variety of MPBS samples with arbitrarily
predetermined output port number (2~7), power ratio and spatial distribution of
output beams. The experimental results reveal that the fabricated MPBSs could
achieve high total splitting efficiency (TSE, above 74.7%) and beam-splitting
fidelity (similarity, above 78.4%) within the bandwidth of 100 nm (1500~1600
nm). We envision that such MPBS could provide fabulous flexibility for optical
integrated system and diverse applications
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