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.
The combination of photonic integrated circuits and free-space metaoptics has the ability to untie technological knots that require advanced light manipulation due to their conjoined ability to achieve strong light–matter interaction via wave-guiding light over a long distance and shape them via large space-bandwidth product. Rapid prototyping of such a compound system requires component interchangeability. This represents a functional challenge in terms of fabrication and alignment of high-performance optical systems. Here, we report a flexible and interchangeable interface between a photonic integrated circuit and the free space using an array of low-loss metaoptics and demonstrate multifunctional beam shaping at a wavelength of 780 nm. We show that robust and high-fidelity operation of the designed optical functions can be achieved without prior precise characterization of the free-space input nor stringent alignment between the photonic integrated chip and the metaoptics chip. A diffraction limited spot of ∼3 μm for a hyperboloid metalens of numerical aperture 0.15 is achieved despite an input Gaussian elliptical deformation of up to 35% and misalignments of the components of up to 20 μm. A holographic image with a peak signal-to-noise ratio of >10 dB is also reported.
The early diagnosis of cancer is essential since it can be treated more effectively when detected earlier. Visual inspection followed by histological examination is, still today, the gold standard for clinicians. However, a large number of unnecessary surgical procedures are still performed. New diagnostics aids are emerging including the recent techniques of optical coherence tomography (OCT) which permits non-invasive 3D optical biopsies of biological tissues, improving patient’s quality of life. Nevertheless, the existing bulk or fiber optics systems are expensive, only affordable at the hospital and thus, not sufficiently used by physicians or cancer’s specialists as an early diagnosis tool. We developed an endoscopic microsystems based on Mirau interferometry and applied for swept source OCT imaging applied for gastroenterology. The architecture is based on a miniature spectrally tuned a single-channel Mirau interferometer integrated with an electro-thermal MEMS microscanner scanning the sample area.
In this paper, we present the construction and preliminary experimental results of a MOEMS fiber-based integrated probe for endoscopic optical imaging of stomach tissue using a Swept-Source Optical Coherence Tomography (SSOCT). The probe consists of a Mirau micro-interferometer, combined with a GRIN lens collimator and a micromirror scanner. We describe the building blocks of the probe, especially the monolithically integrated Mirau mirointerferometer, fabricated by wafer-level vertical stacking and anodic bonding of Si/glass components, and the electrothermal 2-axis MEMS microscanner allowing large swept angles (up to ±22°) at high frequencies (> kHz) for low driving voltages (<20 V). The results of probe characterization, performed in a designed SS-OCT system, have confirmed proper operation of the probe. The B-scan images were obtained for central wavelength of λc = 840 nm, swept range of Dλ = 60 nm and A-scan frequency of fA= 110 kHz. The axial resolution of the probe is equal to 5.2 μm (determined by applied swept source), whereas the lateral resolution, measured by use of USAF test pattern, is 9.8 μm.
Optical coherence tomography (OCT) can obtain light scattering properties with a high resolution, while photoacoustic
imaging (PAI) is ideal for mapping optical absorbers in biological tissues, and ultrasound (US) could penetrate deeply
into tissues and provide elastically structural information. It is attractive and challenging to integrate these three imaging
modalities into a miniature probe, through which, both optical absorption and scattering information of tissues as well as
deep-tissue structure can be obtained. Here, we present a novel side-view probe integrating PAI, OCT and US imaging
based on double-clad fiber which is used as a common optical path for PAI (light delivery) and OCT (light
delivery/detection), and a 40 MHz unfocused ultrasound transducer for PAI (photoacoustic detection) and US
(ultrasound transmission/receiving) with an overall diameter of 1.0 mm. Experiments were conducted to demonstrate the
capabilities of the integrated multimodal imaging probe, which is suitable for endoscopic imaging and intravascular
imaging.
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