We demonstrated nonvolatile, electrically programmable, phase-only modulation of free-space infrared radiation in transmission based on low-loss phase change materials (PCMs) Sb2Se3. By coupling ultra-thin PCM to a high quality-factor (Q~406) diatomic metasurface, we demonstrated a phase-only modulation of ~0.25π (~0.2π) in simulation (experiment), ten times larger than without using the metasurface. The metasurface is robust against reversible switching over 1,000 times. Finally, we showed independent control of 17 meta-molecules, achieving ten deterministic resonance levels in a tunable notch filter with a maximum spectral shift of ~8nm. The independent control also allowed us to achieve varifocal lensing. This work paves way to a nonvolatile phase-only SLM.
Transition metal dichalcogenide(TMD) monolayers and their heterostructures host promising nanoscale light emitters such as single defects and intra/interlayer-excitons. By resonantly coupling these emitters to optical nanocavities, various light-matter interaction phenomena including Purcell enhancement and strong coupling emerge. However, achieving exact matching between cavity and excitonic resonances is difficult mainly because of the inability to precisely control the resonant wavelength of fabricated optical structures. In this work, we demonstrate the use of a cryogenic strain cell to continuously and reversibly tune the optical resonance of GaP nanobeam cavities over a large range. We discuss the merits and challenges of this tuning technique and report our progress in using it to study cavity coupled phenomenon of emitters in monolayer TMD.
Endoscopic imaging enables label free microscopy on the surface of organs, yet relies on spectral absorption information for contrast. The image in a scanning free system is formed using a tiny metalens, or graded index at the tip of the endoscope fiber bundle. However chromatic aberrations often lead to images being distorted between the color channels. In this paper we propose a phase imaging method that utilizes different color channels to encode different depth planes using the chromatic aberrations inherent in small metaoptics or grin leness. The metalens that make the image on the coherent fiber bundle has size dependent chromatic aberration that shifts the focal plane for different wavelengths. We present a phase imaging method that utilizes the chromatic defocusing in endoscope to compute the shape of transparent surfaces at video rate (for transparent lesion detection where the absorption changes are slight or minimal). The phase is solved in a single shot using RGB data.
SignificanceThe scanning fiber endoscope (SFE), an ultrasmall optical imaging device with a large field-of-view (FOV) for having a clear forward view into the interior of blood vessels, has great potential in the cardiovascular disease diagnosis and surgery assistance, which is one of the key applications for short-wave infrared biomedical imaging. The state-of-the-art SFE system uses a miniaturized refractive spherical lens doublet for beam projection. A metalens is a promising alternative that can be made much thinner and has fewer off-axis aberrations than its refractive counterpart.AimWe demonstrate a transmissive metalens working at 1310 nm for a forward viewing endoscope to achieve a shorter device length and better resolution at large field angles.ApproachWe optimize the metalens of the SFE system using Zemax, fabricate it using e-beam lithography, characterize its optical performances, and compare them with the simulations.ResultsThe SFE system has a resolution of ∼ 140 μm at the center of field (imaging distance 15 mm), an FOV of ∼ 70 deg, and a depth-of-focus of ∼15 mm, which are comparable with a state-of-the-art refractive lens SFE. The use of the metalens reduces the length of the optical track from 1.2 to 0.86 mm. The resolution of our metalens-based SFE drops by less than a factor of 2 at the edge of the FOV, whereas the refractive lens counterpart has a ∼ 3 times resolution degradation.ConclusionsThese results show the promise of integrating a metalens into an endoscope for device minimization and optical performance improvement.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.