Monolithic CMOS-compatible zero-index metamaterials.

Zero-index materials exhibit exotic optical properties that can be utilized for integrated-optics applications. However, practical implementation requires compatibility with complementary metallic-oxide-semiconductor (CMOS) technologies. We demonstrate a CMOS-compatible zero-index metamaterial consisting of a square array of air holes in a 220-nm-thick silicon-on-insulator (SOI) wafer. This design supports zero-index modes with Dirac-cone dispersion. The metamaterial is entirely composed of silicon and offers compatibility through low-aspect-ratio structures that can be simply fabricated in a standard device layer. This platform enables mass adoption and exploration of zero-index-based photonic devices at low cost and high fidelity.

On-chip all-dielectric fabrication-tolerant zero-index metamaterials.

Zero-index metamaterials (ZIMs) offer unprecedented ways to manipulate the flow of light, and are of interest for wide range of applications including optical cloaking, super-coupling, and unconventional phase-matching properties in nonlinear optics. Impedance-matched ZIMs can be obtained through a photonic Dirac-cone (PDC) dispersion induced by an accidental degeneracy of an electric monopole and a transverse magnetic dipole mode at the center of the Brillouin zone. Therefore, PDC is very sensitive to fabrication imperfections. In this work, we propose and demonstrate fabrication-tolerant all-dielectric ZIM in telecom regime that supports near PDC dispersion over much wider parameter space than conventional designs. The prism device integrated with Si photonics is fabricated and measured for the verification.

Living-cell imaging using a photonic crystal nanolaser array.

We proposed and demonstrated a label-free imaging method for living cells using a GaInAsP H0-type photonic crystal nanolaser array. We integrated 441 nanolasers in an arrayed configuration and achieved photopumped lasing with a 100% yield. Then, we attached HeLa cells on it, measured the wavelengths of all nanolasers and used them as pixel information. We acquired cell images, which partially corresponds to optical micrographs and probably reflects the attachment condition of the cells. We improved the refractive index resolution from ~10(-2) to 2 × 10(-3) by incorporating a nanoslot into each nanolaser and compensating the nonuniformity of each index sensitivity.

Selective detection of sub-atto-molar Streptavidin in 10(13)-fold impure sample using photonic crystal nanolaser sensors.

Biosensors selectively detecting a very small amount of biomarker protein in human blood are desired for early and reliable diagnoses of severe diseases. This paper reports the detection of protein (streptavidin: SA) in ultra-low concentration, with an ultra-high selectivity against contaminants, using photonic crystal nanolasers. For biotin-modified nanolasers in pure water with SA, an extremely-low detection limit of 16 zM is evaluated. Even in a mixture with 1 µM bovine serum albumin as the contaminant, 100 zM SA is detected, meaning a selectivity of 10(13). These are remarkable capabilities that are promising for practical biosensing in the medical applications mentioned above.

Two Cases of Surgical Correction of Recurrent Mitral Regurgitation due to Failed Catheter- Delivered Mitral Clip (MitraClip).

From April 2018 to February 2021, 150 patients underwent MitraClip implantation for severe functional mitral regurgitation (MR) at our hospital. Two of our patients, an 85-year-old man and an 84-year-old woman, developed a single leaflet device attachment in the acute phase after the implantation and had severe residual MR requiring surgical correction. The recurrent MR was first pointed out on day 5 and day 4, and the duration between MitraClip implantation and surgery was 13 and 55 days, respectively. Due to strong adhesions with the clips and severe valve damage after MitraClip implantation, both cases underwent mitral valve replacement with a good postoperative course. In patients with a high-risk baseline profile, surgical mitral valve replacement after failed MitraClip implantation should be considered at an optimal timing, and a detailed echocardiographic follow-up is required.

A Case of Acute Type A Aortic Dissection after Coronary Artery Bypass Grafting.

The patient was a 69-year-old man who underwent emergency surgery for acute aortic dissection that developed 5 months after coronary artery bypass grafting. The left internal thoracic artery (LITA) graft anastomosed to the left descending artery was not affected by the aortic dissection, and during the ascending aortic replacement, the artery was not identified for clamping. Although fully sufficient cardioplegia was not achieved due to the patent LITA graft, the patient's postoperative cardiac function was good. The two anastomotic sites of the vein grafts to the ascending aorta were excised along with a remnant of the aortic wall in an island fashion and were reimplanted onto the artificial graft. Based on the site of intimal tear, we speculated that partial clamping during the previous surgery had caused the dissection.

On-chip bacterial foraging training in silicon photonic circuits for projection-enabled nonlinear classification.

On-chip training remains a challenging issue for photonic devices to implement machine learning algorithms. Most demonstrations only implement inference in photonics for offline-trained neural network models. On the other hand, artificial neural networks are one of the most deployed algorithms, while other machine learning algorithms such as supporting vector machine (SVM) remain unexplored in photonics. Here, inspired by SVM, we propose to implement projection-based classification principle by constructing nonlinear mapping functions in silicon photonic circuits and experimentally demonstrate on-chip bacterial foraging training for this principle to realize single Boolean logics, combinational Boolean logics, and Iris classification with ~96.7 - 98.3 per cent accuracy. This approach can offer comparable performances to artificial neural networks for various benchmarks even with smaller scales and without leveraging traditional activation functions, showing scalability advantage. Natural-intelligence-inspired bacterial foraging offers efficient and robust on-chip training, and this work paves a way for photonic circuits to perform nonlinear classification.

Midterm Results of Thoracic Endovascular Aortic Repair with Reentry Closure for Chronic Type B Aortic Dissection with Aneurysmal Dilatation.

Objectives: This study aims to discuss the midterm results of thoracic endovascular aortic repair (TEVAR) with reentry closure for chronic type B aortic dissection (CTBAD). Materials and Methods: This retrospective study analyzed 13 patients with CTBAD who underwent TEVAR with reentry closure between July 2014 and December 2020. We evaluated the false lumen (FL) cross-sectional area using computed tomography images of the descending aorta at the level of the bronchial bifurcation, Valsalva sinus, celiac artery, and infrarenal abdominal aorta pre- and postoperation. The study endpoints were technical and clinical success rates, freedom from additional aortic reintervention or surgery, and survival. Results: Technical success was obtained in 12 patients (92.3%) with no hospital mortality and neurological complications. The postoperative observation period was 49.2±21.5 months. The clinical success rate was 76.9% (10 cases), and a postoperative reduction of the FL cross-sectional area was obtained in 53.8% of patients. The 5-year overall survival rate was 64.8% with no aortic-related deaths while the 5-year freedom from additional aortic surgery rate was 66.7%. Conclusions: TEVAR with reentry closure suggests preventing FL dilatation or rupture in CTBAD, but the revision of our devices and further research with more patients and longer follow-up periods are required.

Longterm Followup of a Pediatric Patient with Congenital Abdominal Aortic Aneurysm with Coarctation.

Congenital abdominal aortic aneurysm (AAA) with coarctation has been considered an extremely rare condition. In this study, we present a 3-year-old boy, who was diagnosed by chance with congenital AAA at first operation. We replaced the AAA+coarctation with a 6-mm polytetrafluoroethylene (PTFE) graft. Histological examination of the aortic wall revealed no particular abnormalities. Collateral vessels were noted to develop over 14 years of followup. Good blood flow to both lower limbs and no intermittent claudication were observed. After growth, at the age 17, he underwent extra-anatomical bypass using a 12-mm PTFE graft. This is the first report of successful treatment of congenital AAA+coarctation with longterm followup.

Super-sensitivity in label-free protein sensing using a nanoslot nanolaser.

Microphotonic sensors have been actively studied with increasing demands for label-free biosensing in medical diagnoses and life sciences. For high-throughput and low-cost sensing, a high sensitivity is crucial for eliminating the pre-concentration process, while a simple setup of sensors is also desirable. This paper demonstrates a super-sensitivity for protein, which satisfies these requirements. The key device is a photonic crystal nanolaser, in particular with a nanoslot. Even using a simple setup, the nanolaser achieves an extraordinary-low detection limit for BSA protein, i.e. 255 fM on an average, which cannot be explained by its bulk index sensitivity. The specific adsorption of the protein is observed only around the nanoslot with strong laser intensity. This suggests that the super-sensitivity arises from the effective trapping of protein in the nanoslot.

Ultra-low-loss on-chip zero-index materials.

Light travels in a zero-index medium without accumulating a spatial phase, resulting in perfect spatial coherence. Such coherence brings several potential applications, including arbitrarily shaped waveguides, phase-mismatch-free nonlinear propagation, large-area single-mode lasers, and extended superradiance. A promising platform to achieve these applications is an integrated Dirac-cone material that features an impedance-matched zero index. Although an integrated Dirac-cone material eliminates ohmic losses via its purely dielectric structure, it still entails out-of-plane radiation loss, limiting its applications to a small scale. We design an ultra-low-loss integrated Dirac cone material by achieving destructive interference above and below the material. The material consists of a square array of low-aspect-ratio silicon pillars embedded in silicon dioxide, featuring easy fabrication using a standard planar process. This design paves the way for leveraging the perfect spatial coherence of large-area zero-index materials in linear, nonlinear, and quantum optics.

Emergent Transcatheter Arterial Embolization via a Transpopliteal Approach for Internal Iliac Artery Injury during Lumbar Disk Surgery in the Prone Position.

This report describes a successful case of transcatheter arterial embolization for a critical vascular injury during lumbar disk surgery that resulted in a large retroperitoneal hematoma in a 72-year-old woman. A 4-Fr long sheath was inserted via the right popliteal artery in the prone position. Pelvic angiography revealed a pseudoaneurysm in the right internal iliac artery, which was managed with coil embolization. The patient underwent laparotomy because of abdominal compartment syndrome and was discharged in good condition after rehabilitation. The transpopliteal endovascular approach in the prone position may thus provide the best chance to treat this rare but critical condition.

Refractive index sensing utilizing a cw photonic crystal nanolaser and its array configuration.

We demonstrate refractive index sensing using photonic crystal point shift nanolasers. These lasers operate continuously at room temperature by photopumping in a liquid, and exhibit a 50-dB peak intensity over the background level and a spectral linewidth of < 26 pm, the resolution limit of the present experiment. The lasing wavelength shifts by soaking in different liquids; the wavelength to index sensitivity was 350 nm/RIU, the highest value recorded to date for nanocavity- based sensors. An index resolution of 9.0 x 10(-5) was thus confirmed, leading to an expectation of a resolution of < 10(-6). We propose and demonstrate a spectrometer-free sensor based on nanolasers in an array configuration. These will be disposable sensors with very simple optical I/O. They are anticipated to be integrated with biochips and used for label-free single molecule detection.

Room temperature continuous wave operation and controlled spontaneous emission in ultrasmall photonic crystal nanolaser.

Photonic crystal slab enables us to form an ultrasmall laser cavity with a modal volume close to the diffraction limit of light. However, the thermal resistance of such nanolasers, as high as 10(6) K/W, has prevented continuous-wave operation at room temperature. The present paper reports on the first successful continuous-wave operation at room temperature for the smallest nanolaser reported to date, achieved through fabrication of a laser with a low threshold of 1.2 muW. Near-thresholdless lasing and spontaneous emission enhancement due to the Purcell effect are also demonstrated in a moderately low Q nanolaser, both of which are well explained by a detailed rate equation analysis.