Dielectric metasurface-assisted cavity ring-down spectroscopy for thin-film circular dichroism analysis.

Chiral molecules show differences in their chemical and optical properties due to the different spatial arrangements of the atoms in the two enantiomers. A common way to optically differentiate them is to detect the disparity in the absorption of light by the two enantiomers, i.e. absorption circular dichroism (CD). However, the CD of typical molecules is very small, limiting the sensitivity of chiroptical analysis based on CD. Cavity ring-down spectroscopy (CRDS) is a well-known ultrasensitive absorption spectroscopic method for low-absorbing gas-phase samples because the multiple reflections of light in the cavity greatly increase the absorption path. By inserting a prism into the cavity, the optical mode undergoes total internal reflection (TIR) at the prism surface and the evanescent wave (EW) enables the absorption detection of condensed-phase samples within a very thin layer near the prism surface, called EW-CRDS. Here, we propose an ultrasensitive chiral absorption spectroscopy platform using dielectric metasurface-assisted EW-CRDS. We theoretically show that, upon linearly polarized and oblique incidence, the metasurface exhibits minimum scattering and absorption loss, introduces negligible polarization change, and locally converts the linearly polarized light into near fields with finite optical chirality, enabling CD detection with EW-CRDS that typically works with linearly polarized light. We evaluate the ring-down time in the presence of chiral molecules and determine the sensitivity of the cavity as a function of total absorption from the molecules. The findings open the avenue for the ultrasensitive thin film detection of chiral molecules using CRDS techniques.

Impact of Plasmonic and Dielectric Substrates on the Whispering-Gallery Modes in Self-Assembled Fluorescent Semiconductor Polymer Microspheres.

In this work, the impact of metallic and dielectric conducting substrates, gold and indium tin oxide (ITO)-coated glass, on the whispering gallery modes (WGMs) of semiconductor π-conjugated polymer microspheres is investigated. Hyperspectral mapping was performed to obtain the excitation-position-dependent emission spectra of the microspheres. Substrate-dependent quenching of WGMs sensitive to mode polarization was observed and explained. On a glass substrate, both transverse-electric (TE) and transverse-magnetic (TM) WGMs are quenched due to frustrated total internal reflection. On a gold substrate, however, only the TM WGMs are allowed in symmetry to leak into surface plasmons. An atomically flat gold substrate with subwavelength slits was used to experimentally verify the leakage of WGMs into the surface plasmon polaritons (SPPs). This work provides insight into the damping mechanisms of WGMs in microspheres on metallic and dielectric substrates.

Enhancing on/off ratio of a dielectric-loaded plasmonic logic gate with an amplitude modulator.

Plasmonic waveguides allow focusing, guiding, and manipulating light at the nanoscale and promise the miniaturization of functional optical nanocircuits. Dielectric-loaded plasmonic (DLP) waveguides and logic gates have drawn attention because of their relatively low loss, easy fabrication, and good compatibility with gain and active tunable materials. However, the rather low on/off ratio of DLP logic gates remains the main challenge. Here, we introduce an amplitude modulator and theoretically demonstrate an enhanced on/off ratio of a DLP logic gate for XNOR operation. Multimode interference (MMI) in DLP waveguide is precisely calculated for the design of the logic gate. Multiplexing and power splitting at arbitrary multimode numbers have been theoretically analyzed with respect to the size of the amplitude modulator. An enhanced on/off ratio of 11.26 dB has been achieved. The proposed amplitude modulator can also be used to optimize the performance of other logic gates or MMI-based plasmonic functional devices.

Transoral Endoscopic Thyroidectomy by Vestibular Approach for Papillary Thyroid Carcinoma with Tumor Size ≥2 cm.

Background: The transoral endoscopic thyroidectomy by vestibular approach (TOETVA) has been developed for papillary thyroid carcinoma (PTC) treatment with satisfactory results. However, there were few malignant thyroid nodules ≥2 cm in previous studies of TOETVA. Therefore, we conducted this study to evaluate the results of treatment by TOETVA for PTC with tumor size ≥2 cm. Materials and Methods: The clinical characteristics and surgical outcomes of 10 PTC patients with tumor size ≥2 cm who underwent TOETVA in our center from June 2018 to August 2021 were, respectively, reviewed. Results: All 10 included PTC patients successfully underwent TOETVA and the mean tumor size was 2.5 ± 0.5 cm. The mean number lymph nodes dissected was 9.6 ± 2.9, and 3.1 ± 3.3 positive lymph nodes were discovered. Postoperatively, transient hypoparathyroidism was recorded in 2 patients (20%), transient recurrent laryngeal nerve injury was noted in 1 patient (10%), transient superior laryngeal nerve injury was noted in 1 patient (10%), and numb chin was identified in 1 patient (10%). The postoperative complications aforementioned recovered within 6 months. During a median follow-up of 23.8 ± 13.1 months, no other complications or tumor recurrence were found. Conclusions: TOETVA is feasible for PTC patients with tumor size ≥2 cm and satisfactory short-term surgical outcomes have achieved in this study. We suggested that experienced surgeons can gradually expand the indications for TOETVA.

A novel hybrid approach for "Scarless" (at the neck) lateral neck dissection for papillary thyroid carcinoma: A case series and literature review.

Lateral neck dissection (LND) is a necessary treatment for thyroid cancer with lateral lymph node metastasis. However, the defect created during open surgery leaves a visible scar on the neck. With advancements in surgical technology, many robotic and endoscopic surgical techniques have been reported as alternatives to open surgery. In this study, we present a case series demonstrating the successful application of a novel hybrid approach for endoscopic LND and a review of different surgical approaches for "scarless" (at the neck) LND. We performed endoscopic LND via a combined chest and transoral approach in 24 patients between January 2021 and March 2022. The surgery was completed successfully in all patients with an average operation time of 298.1 ± 72.9 min. The numbers of positive/retrieved lymph nodes at levels II, III-IV, and VI were 0.7 ± 0.9/8.4 ± 4.1, 3.6 ± 2.7/19.5 ± 6.8, and 4.9 ± 3.9/10.3 ± 4.5, respectively. Complications included transient hypoparathyroidism in 10 patients, transient recurrent laryngeal nerve injury in 1 patient, internal jugular vein (IJN) injury in 1 patient, IJN sacrifice due to cancer invasion in 1 patient, and chyle leak in 1 patient, and no cases of tumor recurrence were observed during follow-up. The present case series indicates that the combined chest and transoral approach is feasible and effective for performing LND. Our review of different approaches for "scarless" (at the neck) LND identified advantages and disadvantages for all techniques. Our novel approach has unique advantages, and thus, it can provide an ideal surgical procedure for specific papillary thyroid carcinoma patients.

Safety and feasibility of the transoral endoscopic thyroidectomy vestibular approach with neuroprotection techniques for papillary thyroid carcinoma.

BACKGROUND: This study aimed to evaluate the feasibility and safety of the trans-oral endoscopic thyroidectomy vestibular approach (TOETVA) with neuroprotection techniques for the surgical management of papillary thyroid carcinoma (PTC). METHODS: Patients with PTC who underwent TOETVA between December 2016 and July 2020 were included in this study, and their relevant clinical characteristics, operational details, and surgical outcomes were reviewed and extracted from their medical records for further analysis. RESULTS: A total of 75 patients successfully underwent TOETVA with zero conversions. Unilateral lobectomy with isthmectomy and total thyroidectomy were completed for 58 and 17 patients, respectively, all using our unique neuroprotective procedure and ipsilateral central neck dissection (CND). The mean number of retrieved lymph nodes versus positive lymph nodes was 6.8 ± 3.7 vs. 1.5 ± 2.3. Postoperative complications included three cases of transient superior laryngeal nerve (SLN) palsy (4.0%), five cases of transient recurrent laryngeal nerve (RLN) palsy (6.7%), 14 cases of transient hypoparathyroidism (18.7%), two cases of numb chin (2.7%) and two cases of flap perforation (2.7%). The follow-up period for patients with PTC lasted for 15.6 ± 10.9 months, during which no other complications or tumor recurrence were observed. CONCLUSION: TOETVA can be safely performed for patients with PTC with satisfactory results during the short-term follow-up period. Our neuroprotection techniques can be integrated into TOETVA, which is worth recommending for PTC patients who desire better cosmetic surgical outcomes.

Extremely confined gap plasmon modes: when nonlocality matters.

Historically, the field of plasmonics has been relying on the framework of classical electrodynamics, with the local-response approximation of material response being applied even when dealing with nanoscale metallic structures. However, when the confinement of electromagnetic radiation approaches atomic scales, mesoscopic effects are anticipated to become observable, e.g., those associated with the nonlocal electrodynamic surface response of the electron gas. Here, we investigate nonlocal effects in propagating gap surface plasmon modes in ultrathin metal-dielectric-metal planar waveguides, exploiting monocrystalline gold flakes separated by atomic-layer-deposited aluminum oxide. We use scanning near-field optical microscopy to directly access the near-field of such confined gap plasmon modes and measure their dispersion relation via their complex-valued propagation constants. We compare our experimental findings with the predictions of the generalized nonlocal optical response theory to unveil signatures of nonlocal damping, which becomes appreciable for few-nanometer-sized dielectric gaps.

Endoscopic thyroidectomy via the combined trans-oral and chest approach for cT1-2N1bM0 papillary thyroid carcinoma.

BACKGROUND: Recent years there have been witnessed considerable advances in endoscopic selective lateral neck dissection (LND). However, dissection of lymph nodes at level IV and level VI via the chest approach is inherently challenging. In this study, we used combined trans-oral and chest approach for endoscopic thyroidectomy in patients with cT1-2N1bM0 papillary thyroid carcinoma (PTC). METHODS: Clinical characteristics and surgical outcomes of ten patients with cT1-2N1bM0 PTC who underwent endoscopic thyroidectomy via combination of trans-oral and chest approach between September 2020 and September 2021 were retrospectively reviewed. RESULTS: All 10 patients successfully underwent total thyroidectomy and selective LND via chest approach, while central neck dissection (CND) and supplementary dissection of lymph nodes at level IV were performed via the trans-oral approach. The mean number of positive/retrieved level II, III-IV, and VI lymph nodes were 0.6 ± 1.0/9.8 ± 5.0, 4.6 ± 2.8/23.1 ± 4.7, and 4.9 ± 3.4/10.3 ± 4.6, respectively. Four patients developed transient hypoparathyroidism which spontaneously resolved within 1 month. Five patients developed numbness of lateral neck and ear and one patient experienced limb lift restriction. No other complications or tumor recurrence occurred during follow-up. CONCLUSION: It is feasible to perform total thyroidectomy, CND, and selective LND via combined trans-oral and chest approach, and satisfactory short-term outcomes were observed in this cohort. This approach may offer one more option for cT1-2N1bM0 PTC patients, especially those in whom metastatic lymph nodes at level IV or level VI are detected by preoperative examination.

Qin's seven steps for endoscopic selective lateral neck dissection via the chest approach in patients with papillary thyroid cancer: experience of 35 cases.

BACKGROUND: Endoscopic thyroidectomy is widely performed as it does not result in neck scar. However, there is a paucity of reports pertaining to completely endoscopic lateral neck dissection (LND). In this study, we introduce our step-wise approach for performing endoscopic selective LND via the chest-breast approach. We refer to this approach as Qin's seven steps. METHODS: The Qin's seven steps are: (1) establishment of working space range; (2) dissection of lymph nodes between the SCM and the sternohyoid muscle (level IV) and exposure of omohyoid; (3) dissection of lymph nodes at level IV; (4) dissection of lymph nodes at level III; (5) dissection of lymph nodes at carotid triangle (level III); (6) exposure of accessory nerve and dissection of lymph nodes at level II a; (7) dissection of lymph nodes at level II b. We reviewed the clinical data of 35 patients with papillary thyroid cancer (PTC) who were operated using the Qin's seven steps. RESULTS: All 35 patients successfully underwent LND; bilateral LND was performed in 5 patients. The mean tumor size was 1.8 ± 1.0 cm; seven patients had multiple lesions. The mean number of retrieved lymph nodes in level II, III and IV were 8.8 ± 5.6, 6.1 ± 4.0 and 9.3 ± 5.1, respectively. As for complications, there were 3 cases of accessory nerve injury and 1 case of hypoglossal nerve injury. Internal jugular vein injury, cervical plexus injury and lymphatic leakage occurred in 2, 7, and 1 patients, respectively. CONCLUSION: The Qin's seven steps for performing endoscopic selective LND could be safely used in PTC patients with lateral lymph node metastasis. Satisfactory results were achieved in the short-term follow-up period. We recommend the use of Qin's seven steps for PTC patients who are not desirous of neck scar.

Robust Angular Anisotropy of Circularly Polarized Luminescence from a Single Twisted-Bipolar Polymeric Microsphere.

It has long been surmised that the circular polarization of luminescence (CPL) emitted by a chiral molecule or a molecular assembly should vary with the direction in which the photon is emitted. Despite its potential utility, this anisotropic CPL has not yet been demonstrated at the level of single molecules or supramolecular assemblies. Here we show that conjugated polymers bearing chiral side chains self-assemble into solid microspheres with a twisted bipolar interior, which are formed via liquid-liquid phase separation and subsequent condensation into a cholesteric lyotropic liquid crystalline mesophase. The resultant microspheres, when dispersed in methanol, exhibit CPL with a glum value as high as 0.23. The microspheres are mechanically robust enough to be handled with a microneedle under ambient conditions, allowing comprehensive examination of the angular anisotropy of CPL. The single microsphere is found to exhibit distinct angularly anisotropic birefringence and CPL with glum up to ∼0.5 in the equatorial plane, which is 2.5-fold greater than that along the polar axis. Such optically anisotropic solid materials are important for the application to next-generation microlight-emitting and visualizing devices as well as for fundamental optics studies of chiral light-matter interaction.

Plasmonic elliptical nanoholes for chiroptical analysis and enantioselective optical trapping.

A simple yet effective achiral platform using elliptical nanoholes for chiroptical analysis is demonstrated. Under linearly polarized excitation, an elliptical nanohole in a thin gold film can generate a localized chiral optical field for chiroptical analysis and simultaneously serve as a near-field optical trap to capture dielectric and plasmonic nanospheres. In particular, the trapping potential is enantioselective for dielectric nanospheres, i.e., the hole traps or repels the dielectric nanoparticles depending on the sample chirality. For plasmonic nanospheres, the trapping potential well is much deeper than that for dielectric particles, rendering the enantioselectivity less pronounced. This platform is suitable for chiral analysis with nanoparticle-based solid-state extraction and pre-concentration. Compared to plasmonic chiroptical sensing using chiral structures or circularly polarized light, elliptical nanoholes are a simple and effective platform, which is expected to have a relatively low background because chiroptical noise from the structure or chiral species outside the nanohole is minimized. The use of linearly polarized excitation also makes the platform easily compatible with a commercial optical microscope.

Generation of optical chirality patterns with plane waves, evanescent waves and surface plasmon waves.

We systematically investigate the generation of optical chirality patterns by applying the superposition of two waves in three scenarios, namely free-space plane waves, evanescent waves of totally reflected light at dielectric interface and propagating surface plasmon waves on a metallic surface. In each scenario, the general analytical solution of the optical chirality pattern is derived for different polarization states and propagating directions of the two waves. The analytical solutions are verified by numerical simulations. Spatially structured optical chirality patterns can be generated in all scenarios if the incident polarization states and propagation directions are correctly chosen. Optical chirality enhancement can be obtained from the constructive interference of free-space circularly polarized light or enhanced evanescent waves of totally reflected light. Surface plasmon waves do not provide enhanced optical chirality unless the near-field intensity enhancement is sufficiently high. The structured optical chirality patterns may find applications in chirality sorting, chiral imaging and circular dichroism spectroscopy.

Application of Nano-Carbon in lymph node dissection and protection of parathyroid glands in 3D laparoscopic thyroidectomy / 中国内镜杂志

Objective To explore the clinical significance of Nano-Carbon particles and 3D laparoscopy in central compartment lymph node dissection and parathyroid glands protection in treatment of cN0 thyroid cancer. Methods We conduct a retrospective analysis of sixty-five patients with cN0 thyroid cancer who were received 3D laparoscopic thyroidectomy in the last 3 years. All patients were received total resection of thyroid plus the affected side and (or) contralateral side central compartment lymph node dissection. All patients were allocated to control group (n = 32) and carbon nano-particles trace group (tracer group, n = 33). The lymph node-related indexes (including number of dissected lymph node at Ⅵ area, number of Metastatic lymph node and Frozen lymph node-positive rate at Ⅵ area), serum calcium (24 h after surgery) and PTH (48 h after surgery) were collected and compared between the 2 groups. Results Number of dissected lymph node at Ⅵ area, positive rates of intraoperative frozen-section examination of parathyroid glands and PTH (48 h after surgery) were found statistical higher in nanoparticles group than control (P < 0.05). No statistical difference were found in Number of Metastatic lymph node and serum calcium (24 h after surgery) (P < 0.05). Conclusion The clinical significance of carbon nanoparticles and 3D laparoscopy is effective and feasible for central compartment lymph node dissection and parathyroid glands protection in treatment of cN0 thyroid cancer.

Application of Nano-Carbon in lymph node dissection and protection of parathyroid glands in 3D laparoscopic thyroidectomy / 中国内镜杂志

Objective To explore the clinical significance of Nano-Carbon particles and 3D laparoscopy in central compartment lymph node dissection and parathyroid glands protection in treatment of cN0 thyroid cancer. Methods We conduct a retrospective analysis of sixty-five patients with cN0 thyroid cancer who were received 3D laparoscopic thyroidectomy in the last 3 years. All patients were received total resection of thyroid plus the affected side and (or) contralateral side central compartment lymph node dissection. All patients were allocated to control group (n = 32) and carbon nano-particles trace group (tracer group, n = 33). The lymph node-related indexes (including number of dissected lymph node at Ⅵ area, number of Metastatic lymph node and Frozen lymph node-positive rate at Ⅵ area), serum calcium (24 h after surgery) and PTH (48 h after surgery) were collected and compared between the 2 groups. Results Number of dissected lymph node at Ⅵ area, positive rates of intraoperative frozen-section examination of parathyroid glands and PTH (48 h after surgery) were found statistical higher in nanoparticles group than control (P < 0.05). No statistical difference were found in Number of Metastatic lymph node and serum calcium (24 h after surgery) (P < 0.05). Conclusion The clinical significance of carbon nanoparticles and 3D laparoscopy is effective and feasible for central compartment lymph node dissection and parathyroid glands protection in treatment of cN0 thyroid cancer.