Hexagonal Boron Nitride for Photonic Device Applications: A Review.

Hexagonal boron nitride (hBN) has emerged as a key two-dimensional material. Its importance is linked to that of graphene because it provides an ideal substrate for graphene with minimal lattice mismatch and maintains its high carrier mobility. Moreover, hBN has unique properties in the deep ultraviolet (DUV) and infrared (IR) wavelength bands owing to its indirect bandgap structure and hyperbolic phonon polaritons (HPPs). This review examines the physical properties and applications of hBN-based photonic devices that operate in these bands. A brief background on BN is provided, and the theoretical background of the intrinsic nature of the indirect bandgap structure and HPPs is discussed. Subsequently, the development of DUV-based light-emitting diodes and photodetectors based on hBN's bandgap in the DUV wavelength band is reviewed. Thereafter, IR absorbers/emitters, hyperlenses, and surface-enhanced IR absorption microscopy applications using HPPs in the IR wavelength band are examined. Finally, future challenges related to hBN fabrication using chemical vapor deposition and techniques for transferring hBN to a substrate are discussed. Emerging techniques to control HPPs are also examined. This review is intended to assist researchers in both industry and academia in the design and development of unique hBN-based photonic devices operating in the DUV and IR wavelength regions.

Extraordinary Optical Transmission by Hybrid Phonon-Plasmon Polaritons Using hBN Embedded in Plasmonic Nanoslits.

Hexagonal boron nitride (hBN) exhibits natural hyperbolic dispersion in the infrared (IR) wavelength spectrum. In particular, the hybridization of its hyperbolic phonon polaritons (HPPs) and surface plasmon resonances (SPRs) induced by metallic nanostructures is expected to serve as a new platform for novel light manipulation. In this study, the transmission properties of embedded hBN in metallic one-dimensional (1D) nanoslits were theoretically investigated using a rigorous coupled wave analysis method. Extraordinary optical transmission (EOT) was observed in the type-II Reststrahlen band, which was attributed to the hybridization of HPPs in hBN and SPRs in 1D nanoslits. The calculated electric field distributions indicated that the unique Fabry-Pérot-like resonance was induced by the hybridization of HPPs and SPRs in an embedded hBN cavity. The trajectory of the confined light was a zigzag owing to the hyperbolicity of hBN, and its resonance number depended primarily on the aspect ratio of the 1D nanoslit. Such an EOT is also independent of the slit width and incident angle of light. These findings can not only assist in the development of improved strategies for the extreme confinement of IR light but may also be applied to ultrathin optical filters, advanced photodetectors, and optical devices.

Successful treatment of recurrent volvulus in the afferent limb of the pouch following proctocolectomy for ulcerative colitis: a case report.

BACKGROUND: Pouch volvulus after proctocolectomy for ulcerative colitis is a very rare postoperative complication. The common site of pouch volvulus has been reported to be the ileal pouch-anal anastomosis and the middle part of the pouch, but no reports on pouch volvulus in the afferent limb of the pouch have been observed. Here, we report the case of a patient with afferent limb volvulus who underwent afferent limbpexy, but required reoperation 7 months later. CASE PRESENTATION: A 38-year-old man with refractory ulcerative colitis had undergone open proctocolectomy 10 years ago at another hospital. He had been aware of lower abdominal pain and bowel movement difficulty for 2 years. After repeated bowel obstruction, he was referred to our hospital for surgery. Based on the radiographic findings, we diagnosed a pouch volvulus and performed an operation. Laparoscopically, counterclockwise rotation of the afferent limb of the pouch was recognized. Moreover, the ileal mesentery was adhered and fixed to the presacral space 20 cm from the oral side of the pouch. The antimesenteric side of the afferent limb was fixed using interrupted stiches on the left peritoneal wall of the pelvis. He was discharged uneventfully 18 days after surgery, and defecation improved immediately. However, he was readmitted 7 months after surgery with the same abdominal pain and defecation difficulty. A similar finding was found and diagnosed as recurrent volvulus. Therefore, we performed a laparoscopic surgery. The same volvulus as in the previous surgery was confirmed. The site fixed during the previous surgery showed scars, but the afferent limb was free. The dilated ileum that contained the volvulus was excised only on the oral side of the pouch and an intraluminal anastomosis was performed on the anterior wall of the pouch. He had a good postoperative course and was discharged. CONCLUSION: Proper diagnosis of volvulus based on the characteristic imaging findings is important. In principle, bilateral row fixation of the rotated ileum is the basic procedure for volvulus. However, fixation with this technique is sometimes difficult. Therefore, this procedure is one of the useful options for the fixation of difficult or recurrent cases.

Graphene Plasmonics in Sensor Applications: A Review.

Surface plasmon polaritons (SPPs) can be generated in graphene at frequencies in the mid-infrared to terahertz range, which is not possible using conventional plasmonic materials such as noble metals. Moreover, the lifetime and confinement volume of such SPPs are much longer and smaller, respectively, than those in metals. For these reasons, graphene plasmonics has potential applications in novel plasmonic sensors and various concepts have been proposed. This review paper examines the potential of such graphene plasmonics with regard to the development of novel high-performance sensors. The theoretical background is summarized and the intrinsic nature of graphene plasmons, interactions between graphene and SPPs induced by metallic nanostructures and the electrical control of SPPs by adjusting the Fermi level of graphene are discussed. Subsequently, the development of optical sensors, biological sensors and important components such as absorbers/emitters and reconfigurable optical mirrors for use in new sensor systems are reviewed. Finally, future challenges related to the fabrication of graphene-based devices as well as various advanced optical devices incorporating other two-dimensional materials are examined. This review is intended to assist researchers in both industry and academia in the design and development of novel sensors based on graphene plasmonics.

Special Issue: New Horizon of Plasmonics and Metamaterials.

Plasmonics and metamaterials are growing fields that consistently produce new technologies for controlling electromagnetic waves. Many important advances in both fundamental knowledge and practical applications have been achieved in conjunction with a wide range of materials, structures and wavelengths, from the ultraviolet to the microwave regions of the spectrum. In addition to this remarkable progress across many different fields, much of this research shares many of the same underlying principles, and so significant synergy is expected. This Special Issue introduces the recent advances in plasmonics and metamaterials and discusses various applications, while addressing a wide range of topics in order to explore the new horizons emerging for such research.

Elimination of Unwanted Modes in Wavelength-Selective Uncooled Infrared Sensors with Plasmonic Metamaterial Absorbers using a Subtraction Operation.

Wavelength- or polarization-selective uncooled infrared (IR) sensors have various applications, such as in fire detection, gas analysis, hazardous material recognition, biological analysis, and polarimetric imaging. The unwanted modes originating due to the absorption by the materials used in these sensors, other than plasmonic metamaterial absorbers (PMAs), cause serious issues by degenerating the wavelength or polarization selectivity. In this study, we demonstrate a method for eliminating these unwanted modes in wavelength- or polarization-selective uncooled IR sensors with various PMAs, using a subtraction operation and a reference pixel. The aforementioned sensors and the reference pixels were fabricated using a complementary metal oxide semiconductor and micromachining techniques. We fabricated the reference pixel with the same structure as the PMA sensors, except a flat mirror was formed on the absorber surface instead of PMAs. The spectral responsivity measurements demonstrated that single-mode detection can be achieved through the subtraction operation with the reference pixel. The method demonstrated in this study can be applied to any type of uncooled IR sensors to create high-performance wavelength- or polarization-selective absorbers capable of multispectral or polarimetric detection.

Low dark current and high-responsivity graphene mid-infrared photodetectors using amplification of injected photo-carriers by photo-gating.

Low dark current, high-responsivity middle-wavelength infrared (IR) graphene photodetectors using photo-gating amplification of injected photo-carriers are demonstrated. A graphene/p-indium antimonide (InSb) heterojunction and graphene/insulator region were formed. The injected photo-carriers from InSb to graphene were amplified by photo-gating induced in the graphene/tetraethyl orthosilicate (TEOS) region, resulting in the high responsivity and low dark current performance. A responsivity of 14.9 A/W and an ON/OFF ratio of 2.66×104 were achieved. The photoresponse is shown to be determined by the cross-sectional area between the graphene and the TEOS-SiO2, in which the injected photo-carriers into graphene were modulated and amplified by the photo-gating effect. Our results indicate that high-performance IR photodetectors based on the developed graphene photodetectors can be realized.

Fatal Fournier's gangrene caused by Clostridium ramosum in a patient with central diabetes insipidus and insulin-dependent diabetes mellitus: a case report.

BACKGROUND: Clostridium ramosum is a generally non-pathogenic enteric anaerobe, and Fournier's gangrene is a rare necrotizing soft tissue infection with male predisposition affecting the perineum and the genital area. We report, to our knowledge, the first case of Fournier's gangrene caused by C. ramosum in a female patient with multiple underlying conditions. CASE PRESENTATION: A 44-year-old woman with a 6-year history of insulin-dependent diabetes mellitus after total pancreatectomy and an 11-year history of central diabetes insipidus developed a pain in the genital area after a month of urinary catheter use. The lower abdominal pain worsened gradually over 2 weeks, and the pain, general fatigue, and loss of appetite prompted the patient's hospital admission. As she had severe edema in her pelvic and bilateral femoral areas, ceftriaxone was started empirically after collecting two sets of blood cultures. On hospital day 2, CT examination revealed the presence of necrotizing faciitis in the genital and pelvic areas, and the antibiotics were changed to a combination of meropenem, vancomycin, and clindamycin. Gram-positive cocci and gram-positive rods were isolated from blood cultures, which were finally identified as Streptococcus constellatus and C. ramosum using superoxide dismutase and 16S rDNA sequencing. An emergent surgery was performed on hospital day 2 to remove the affected tissue. Despite undergoing debridement and receiving combined antimicrobial chemotherapies, the patient's clinical improvement remained limited. The patient's condition continued to deteriorate, and she eventually died on hospital day 8. In the present case, the underlying diabetes mellitus, urinary incontinence due to central diabetes insipidus, undernutrition, and edema served as the predisposing conditions. CONCLUSIONS: C. ramosum is a potentially opportunistic pathogen among immunosuppressed persons and a rare cause of necrotizing fasciitis.

Metal-Insulator-Metal-Based Plasmonic Metamaterial Absorbers at Visible and Infrared Wavelengths: A Review.

Electromagnetic wave absorbers have been investigated for many years with the aim of achieving high absorbance and tunability of both the absorption wavelength and the operation mode by geometrical control, small and thin absorber volume, and simple fabrication. There is particular interest in metal-insulator-metal-based plasmonic metamaterial absorbers (MIM-PMAs) due to their complete fulfillment of these demands. MIM-PMAs consist of top periodic micropatches, a middle dielectric layer, and a bottom reflector layer to generate strong localized surface plasmon resonance at absorption wavelengths. In particular, in the visible and infrared (IR) wavelength regions, a wide range of applications is expected, such as solar cells, refractive index sensors, optical camouflage, cloaking, optical switches, color pixels, thermal IR sensors, IR microscopy and gas sensing. The promising properties of MIM-PMAs are attributed to the simple plasmonic resonance localized at the top micropatch resonators formed by the MIMs. Here, various types of MIM-PMAs are reviewed in terms of their historical background, basic physics, operation mode design, and future challenges to clarify their underlying basic design principles and introduce various applications. The principles presented in this review paper can be applied to other wavelength regions such as the ultraviolet, terahertz, and microwave regions.

Graphene on metal-insulator-metal-based plasmonic metamaterials at infrared wavelengths.

Metal-insulator-metal-based plasmonic metamaterial absorbers (MIM-PMAs) generate strong localized surface plasmon resonance (LSPR) on their surfaces. Therefore, MIM-PMAs are expected to enhance the absorption of graphene coated on their surfaces. Graphene-coated MIM-PMAs (GMIM-PMAs) were developed and their optical properties were investigated both experimentally and numerically at infrared wavelengths. Significant modification of the absorption of GMIM-PMAs was achieved only in the main LSPR wavelength region, where the insulator is lossless. The enhancement of the absorption of graphene could be maximized by the optimization of the insulator thickness of the MIM-PMAs. The results obtained here are expected to contribute to the development of high-responsivity graphene-based photodetectors and optoelectronic devices.

Graphene Surface Acoustic Wave Sensor for Simultaneous Detection of Charge and Mass.

We have combined a graphene field-effect transistor (GFET) and a surface acoustic wave (SAW) sensor on a LiTaO3 substrate to create a graphene surface acoustic wave (GSAW) sensor. When a SAW propagates in graphene, an acoustoelectric current (IA) flows between two attached electrodes. This current has unique electrical characteristics, having both positive and negative peak values with respect to the electrolyte-gate voltage (VEg) in solution. We found that IA is controlled by VEg and the amplitude of the SAW. It was also confirmed that the GSAW sensor detects changes of electrical charge in solution like conventional GFET sensors. Furthermore, the detection of amino-group-modified microbeads was performed by employing a GSAW sensor in a phthalate buffer solution at pH 4.1. The hole current peak shifted to the lower left in the IA-VEg characteristics. The left shift was caused by charge detection by the GFET and can be explained by an increase of amino groups that have positive charges at pH 4.1. In contrast, the downward shift is thought to be due to a reduction in the amplitude of the propagating SAW because of an increase in the mass loading of microbeads. This mass loading was detected by the SAW sensor. Thus, we have demonstrated that the GSAW sensor is a transducer capable of the simultaneous detection of charge and mass, which indicates that it is an attractive platform for highly sensitive and multifunctional solution sensing.

Wavelength- or Polarization-Selective Thermal Infrared Detectors for Multi-Color or Polarimetric Imaging Using Plasmonics and Metamaterials.

Wavelength- or polarization-selective thermal infrared (IR) detectors are promising for various novel applications such as fire detection, gas analysis, multi-color imaging, multi-channel detectors, recognition of artificial objects in a natural environment, and facial recognition. However, these functions require additional filters or polarizers, which leads to high cost and technical difficulties related to integration of many different pixels in an array format. Plasmonic metamaterial absorbers (PMAs) can impart wavelength or polarization selectivity to conventional thermal IR detectors simply by controlling the surface geometry of the absorbers to produce surface plasmon resonances at designed wavelengths or polarizations. This enables integration of many different pixels in an array format without any filters or polarizers. We review our recent advances in wavelength- and polarization-selective thermal IR sensors using PMAs for multi-color or polarimetric imaging. The absorption mechanism defined by the surface structures is discussed for three types of PMAs-periodic crystals, metal-insulator-metal and mushroom-type PMAs-to demonstrate appropriate applications. Our wavelength- or polarization-selective uncooled IR sensors using various PMAs and multi-color image sensors are then described. Finally, high-performance mushroom-type PMAs are investigated. These advanced functional thermal IR detectors with wavelength or polarization selectivity will provide great benefits for a wide range of applications.

Detection Wavelength Control of Uncooled Infrared Sensors Using Two-Dimensional Lattice Plasmonic Absorbers.

Wavelength-selective uncooled infrared (IR) sensors are highly promising for a wide range of applications, such as fire detection, gas analysis and biomedical analysis. We have recently developed wavelength-selective uncooled IR sensors using square lattice two-dimensional plasmonic absorbers (2-D PLAs). The PLAs consist of a periodic 2-D lattice of Au-based dimples, which allow photons to be manipulated using surface plasmon modes. In the present study, a detailed investigation into control of the detection wavelength was conducted by varying the PLA lattice structure. A comparison was made between wavelength-selective uncooled IR sensors with triangular and square PLA lattices that were fabricated using complementary metal oxide semiconductor and micromachining techniques. Selective enhancement of the responsivity could be achieved, and the detection wavelength for the triangular lattice was shorter than that for the square lattice. The results indicate that the detection wavelength is determined by the reciprocal-lattice vector for the PLAs. The ability to control the detection wavelength in this manner enables the application of such PLAs to many types of thermal IR sensors. The results obtained here represent an important step towards multi-color imaging in the IR region.

Chronic thromboembolic pulmonary hypertension complicated with homocystinuria.

A 17-year-old boy with homocystinuria was found to have a systolic murmur during a routine examination. Echocardiography demonstrated pulmonary hypertension (PH), and computer tomography angiography showed pulmonary thrombi. Although 12-month anticoagulation treatment reduced the thrombotic material within the main branch, it failed to clear thrombotic materials in the left and right lobar branches. Two years later, the patient was admitted to our hospital due to a worsening of PH. Treatment with bosentan, sildenafil and beraprost, in addition to anti-coagulant therapy, did not improve his PH. Balloon pulmonary angioplasty (BPA) was performed to remove the pulmonary thrombi. BPA markedly improved the patient's hemodynamics and exercise capacity. Close follow-up is scheduled to prevent any potential future thrombotic complications.

Treatment strategy for preventing pouchitis as a postoperative complication of ulcerative colitis: the significance of the management of cuffitis.

PURPOSE: The aim of this study was to examine the risk factors for and to evaluate strategies for preventing pouchitis as a postoperative complication of ulcerative colitis (UC). METHODS: A total of 119 cases of UC in which restorative proctocolectomy with an ileal pouch-anal anastomosis (IPAA) was performed at our institution between 2000 and 2012 was investigated; nine patients in whom it was impossible to close the ileostomy due to an intractable anal fistula or pelvic abscess were excluded. RESULTS: The cumulative risk of developing pouchitis 5 years after IPAA with stoma closure was 31.0%. Significant relationships with pouchitis were found for the surgical indication (p = 0.0126) and surgical method (p = 0.0214). A significant correlation was found between pouchitis and cuffitis. Pouchitis was significantly more common in the cases with cuffitis than in those without (p = 0.0002). There was also a significantly different cumulative incidence observed between the cases with and without cuffitis (p < 0.0001). In addition, pouchitis had a greater tendency to recur in the cases with cuffitis than in those without (p = 0.2730). CONCLUSION: The cumulative incidence rate of pouchitis was 10.6% at 1 year, 15.1% at 2 years and 31.0% at 5 years. Controlling cuffitis is important to prevent pouchitis.

Importance of the Postoperative Carcinoembryonic Antigen Level during Follow-Up after Curative Resection in Patients with Liver Metastatic Colorectal Carcinoma.

BACKGROUND/AIMS: To validate the conventional Japanese grading of liver metastasis for no residual tumor resection in Stage IV colorectal cancer (CRC) with liver metastasis and to identify risk factors for postoperative recurrence. METHODOLOGY: The subjects of this study were 1792 Stage IV CRC patients with liver metastasis. RESULTS: In 1792 cases, including unresectable cases, there was a significantly different prognosis by grade (P < 0.0001). In 421 R0 cases, there was no significant difference between Grade A and Grade B (P = 0.8527). In 381 cases without extra-hepatic metastasis, the prognosis was not significantly different among three grades. On multivariate analysis, carcinoembryonic antigen within 3 months from R0 operation (3M-CEA) was an independent risk factor regardless of extrahepatic metastasis. There was a significantly different prognosis (P < 0.0001) among Grade A', defined as a normal 3M-CEA level, Grade B', defined as Grade A or B and an abnormal 3M-CEA level, and Grade C', defined as Grade C and an abnormal 3M-CEA level. CONCLUSIONS: The postoperative CEA level is an important risk factor during follow-up after curative resection in patients with liver metastatic colorectal carcinoma. The combination of the 3M-CEA level and conventional grading of liver metastasis is useful for follow-up of R0 resection cases.

Sub-classification of Stage II colorectal cancer based on clinicopathological risk factors for recurrence.

PURPOSE: To make a Stage II colorectal cancer (CRC) sub-classification based on clinicopathological factors. METHODS: The subjects of this study were 422 patients with Stage II CRC, who underwent curative surgery with dissection of more than 12 lymph nodes. We used the logistic regression analysis or model and Cox's proportional hazard regression model for analysis. RESULTS: Preoperative carcinoembryonic antigen (CEA) level (p = 0.0057), macroscopic type (p = 0.0316), and depth of invasion (p = 0.0401) were extracted as independent risk factors for recurrence, whereas the preoperative CEA level (p = 0.0045) and depth of invasion (p = 0.0395) were extracted as independent predictors of 5-year disease-free survival. We defined depth of invasion (pT4) and the preoperative CEA level (abnormal) as risk factors for recurrence, and classified Grade A as a normal CEA level regardless of depth invasion, Grade B as depth of invasion to pT3 and an elevated CEA level, and Grade C as depth of invasion to pT4 and an elevated CEA level. There were significant differences in cumulative 5-year disease-free survival rates among each grade (Grade A vs. Grade B, p = 0.0474; Grade A vs. Grade C, p < 0.0001; Grade B vs. Grade C, p = 0.0134). CONCLUSION: The sub-classification of Stage II CRC, according not only to depth of invasion but also to preoperative CEA level, is important for predicting the prognosis.

[The feasibility of oral fluoropyrimidines as adjuvant chemotherapy after resection and local coagulation therapy of colorectal liver metastases].

OBJECTIVE: To evaluate the feasibility of oral fluoropyrimidines after resection and microwave coagulation(MCT), or radiofrequency ablation(RFA)of liver metastases from colorectal cancer. PATIENTS AND METHODS: Background factors, fluoropyrimidine administration(S-1 or UFT/LV), and adverse events were analyzed in 20 patients(17 males, 3 females; an average of 62. 4 years)with colorectal liver metastases after resection and RFA or MCT. RESULTS: The synchronous: metachronous metastases ratio was 13:7. Fifteen patients received the recommended dose and 5 received a reduced dose. S-1 was administered for 4 weeks followed by a 2-week rest for 7 patients, and for 2 weeks followed by a 1-week rest for 9 patients. UFT/LV was administered for 4 weeks followed by a 1-week rest for 4 patients. Fourteen patients(70%)had adverse events. One patient showed grade 3 leukocyte toxicity while other patients showed grade 1 or 2. Two patients discontinued chemotherapy because of grade 2 delirium and grade 2 CPK elevation; another 2 discontinued voluntarily. Eight patients with recurrence changed the rugs, while 8 of 12(67%)continued for 1 year. Median disease-free and med ian overall survival lengths were 16. 1 and 4 7. 6 months, respectively. CONCLUSION: S-1 and UFT /LV were used safely as adjuvant chemotherapies after the resection and local coagulation therapy of liver metastases.

Case of peritoneal dissemination of colon cancer in which PET/CT was useful in determining the indicated surgical procedure.

The right half of the colon was resected in a 70-year-old woman in August 2002 for ascending colon cancer. The peritoneum was also resected because of metastasis (Stage IV). Since tumor markers gradually increased, positron emission tomography (PET)/ computed tomography (CT) revealed peritoneal dissemination. Abdominal pain appeared 40 months after surgery. Barium enema findings revealed an ileal constriction approximately 25 cm from the anastomosed site toward the anus. Repeat PET/CT revealed peritoneal dissemination coinciding with ileal constriction. CT did not reveal well-defined tumor shadows. The patient was diagnosed with constriction associated with peritoneal metastasis and underwent surgery. Surgical findings revealed a roughly 2-cm peritoneal metastatic focus and ileal constriction. The site was resected and anastomosed. Postoperative progress was favorable; the patient was discharged and enjoys a favorable quality of life through outpatient adjuvant chemotherapy. PET/CT is suggested to be useful in observing the progress of peritoneal dissemination and may be of assistance in determining the course of treatment.