RESUMO
We investigate the reduction of transition loss across the star coupler boundary in a silicon arrayed waveguide grating (AWG) by suppressing multimode generation and scattering near the boundary of a star coupler. Eight-channel silicon AWGs were designed with optimal conditions based on enhanced field matching in combination with ultrashallow etched structures. The fabricated AWG demonstrates an insertion loss down to 0.63 dB with a cross talk of -23 to -25.3 dB, exhibiting ~0.8 dB improvement of insertion loss and ~4 dB improvement of cross talk compared to the Si AWG fabricated with a conventional double-etch technique.
RESUMO
When silicon photonic integrated circuits (PICs), defined for transmitting and receiving optical data, are successfully monolithic-integrated into major silicon electronic chips as chip-level optical I/Os (inputs/outputs), it will bring innovative changes in data computing and communications. Here, we propose new photonic integration scheme, a single-chip optical transceiver based on a monolithic-integrated vertical photonic I/O device set including light source on bulk-silicon. This scheme can solve the major issues which impede practical implementation of silicon-based chip-level optical interconnects. We demonstrated a prototype of a single-chip photonic transceiver with monolithic-integrated vertical-illumination type Ge-on-Si photodetectors and VCSELs-on-Si on the same bulk-silicon substrate operating up to 50 Gb/s and 20 Gb/s, respectively. The prototype realized 20 Gb/s low-power chip-level optical interconnects for λ ~ 850 nm between fabricated chips. This approach can have a significant impact on practical electronic-photonic integration in high performance computers (HPC), cpu-memory interface, hybrid memory cube, and LAN, SAN, data center and network applications.
RESUMO
We present small-sized depletion-type silicon Mach-Zehnder (MZ) modulator with a vertically dipped PN depletion junction (VDJ) phase shifter based on a CMOS compatible process. The fabricated device with a 100 µm long VDJ phase shifter shows a VπLπ of â¼0.6 V·cm with a 3 dB bandwidth of â¼50 GHz at -2 V bias. The measured extinction ratios are 6 and 5.3 dB for 40 and 50 Gb/s operation under 2.5 Vpp differential drive, respectively. On-chip insertion loss is 3 dB for the maximum optical transmission. This includes the phase-shifter loss of 1.88 dB/100 µm, resulting mostly from the extra optical propagation loss through the polysilicon-plug structure for electrical contact, which can be readily minimized by utilizing finer-scaled lithography nodes. The experimental result indicates that a compact depletion-type MZ modulator based on the VDJ scheme can be a potential candidate for future chip-level integration.
RESUMO
This paper reports a fiber-to-chip coupler consisting of a silicon inverted taper and a silicon oxynitride (SiON) double stage taper, where the cascaded taper structure enables adiabatic mode transfer between a submicron silicon waveguide and a single mode fiber. The coupler, fabricated by a simplified process, demonstrates an average coupling loss of 3.6 and 4.2 dB for TM and TE polarizations, respectively, with a misalignment tolerance of ± 2.2 µm for 1 dB loss penalty.
RESUMO
We present high-sensitivity photoreceivers based on a vertical- illumination-type 100% Ge-on-Si p-i-n photodetectors (PDs), which operate up to 50 Gb/s with high responsivity. A butterfly-packaged photoreceiver using a Ge PD with 3-dB bandwidth (f(-3dB)) of 29 GHz demonstrates the sensitivities of -10.15 dBm for 40 Gb/s data rate and -9.47 dBm for 43 Gb/s data rate, at BER of 10(-12) and λ ~1550 nm. Also a photoreceiver based on a Ge PD with f(-3dB)~19 GHz shows -14.14 dBm sensitivity at 25 Gb/s operation. These results prove the high performance levels of vertical-illumination type Ge PDs ready for practical high-speed network applications.
RESUMO
We present a silicon-on-insulator Echelle grating 8-channel demutiplexer showing characteristic features, average insertion loss 2.4 dB measured at 1520~1570 nm, adjacent channel crosstalk 15-18 dB, and channel spacing 11.9 nm. Our Echelle grating is remarked by a total internal reflector (TIR) which reflects incident light by a single reflection in contrast to the double reflections of retro-reflector TIR Echelle gratings.
Assuntos
Lentes , Refratometria/instrumentação , Semicondutores , Processamento de Sinais Assistido por Computador/instrumentação , Desenho de Equipamento , Análise de Falha de Equipamento , SilícioRESUMO
To investigate the functions of recombinant human dentin phosphoprotein (rhDPP), we examined cell adhesion, viability and the odontoblastic differentiation activity of human dental pulp cells (hDPCs). Firstly, rhDPP was constructed using pBAD-HisA plasmid in Escherichia coli. Cell adhesion and viability of hDPCs by rhDPP was examined using a crystal violet assay and a MTT assay, ALP, mineralization activity and odontoblastic differentiation-related mRNA levels of hDPCs were measured to elucidate the odontoblastic differentiation effect of rhDPP on hDPCs. Initially, rhDPP significantly and dose-dependently increased hDPCs adhesion versus the untreated control (p < 0.05). Cell viability was also significantly increased by rhDPP at 5 days (p < 0.001). Furthermore, the odontoblastic differentiation effect of rhDPP was verified by measuring ALP activity, mineralization activity and the mRNA levels of odontoblastic differentiation markers. Taken together, rhDPP is expected to play an important role on hDPCs, thereby suggesting its potential use for tooth repair and regeneration.
Assuntos
Diferenciação Celular/efeitos dos fármacos , Polpa Dentária/citologia , Proteínas da Matriz Extracelular/biossíntese , Odontoblastos/fisiologia , Fosfoproteínas/biossíntese , Sialoglicoproteínas/biossíntese , Fosfatase Alcalina/genética , Fosfatase Alcalina/metabolismo , Calcificação Fisiológica , Adesão Celular , Proliferação de Células , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Colágeno Tipo I/genética , Colágeno Tipo I/metabolismo , Escherichia coli , Proteínas da Matriz Extracelular/genética , Proteínas da Matriz Extracelular/isolamento & purificação , Proteínas da Matriz Extracelular/metabolismo , Proteínas da Matriz Extracelular/farmacologia , Expressão Gênica , Humanos , Odontoblastos/enzimologia , Odontoblastos/metabolismo , Fosfoproteínas/genética , Fosfoproteínas/isolamento & purificação , Fosfoproteínas/metabolismo , Fosfoproteínas/farmacologia , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/isolamento & purificação , Proteínas Recombinantes/farmacologia , Sialoglicoproteínas/isolamento & purificação , Sialoglicoproteínas/farmacologiaRESUMO
We present high performance silicon photonic circuits (PICs) defined for off-chip or on-chip photonic interconnects, where PN depletion Mach-Zehnder modulators and evanescent-coupled waveguide Ge-on-Si photodetectors were monolithically integrated on an SOI wafer with CMOS-compatible process. The fabricated silicon PIC(off-chip) for off-chip optical interconnects showed operation up to 30 Gb/s. Under differential drive of low-voltage 1.2 V(pp), the integrated 1 mm-phase-shifter modulator in the PIC(off-chip) demonstrated an extinction ratio (ER) of 10.5dB for 12.5 Gb/s, an ER of 9.1dB for 20 Gb/s, and an ER of 7.2 dB for 30 Gb/s operation, without adoption of travelling-wave electrodes. The device showed the modulation efficiency of V(π)L(π) ~1.59 Vcm, and the phase-shifter loss of 3.2 dB/mm for maximum optical transmission. The Ge photodetector, which allows simpler integration process based on reduced pressure chemical vapor deposition exhibited operation over 30 Gb/s with a low dark current of 700 nA at -1V. The fabricated silicon PIC(intra-chip) for on-chip (intra-chip) photonic interconnects, where the monolithically integrated modulator and Ge photodetector were connected by a silicon waveguide on the same chip, showed on-chip data transmissions up to 20 Gb/s, indicating potential application in future silicon on-chip optical network. We also report the performance of the hybrid silicon electronic-photonic IC (EPIC), where a PIC(intra-chip) chip and 0.13µm CMOS interface IC chips were hybrid-integrated.
Assuntos
Dispositivos Ópticos , Fotometria/instrumentação , Processamento de Sinais Assistido por Computador/instrumentação , Silício/química , Telecomunicações/instrumentação , Desenho de Equipamento , Análise de Falha de Equipamento , Micro-Ondas , Fótons , Semicondutores , Integração de SistemasRESUMO
BACKGROUND: This retrospective study determined whether extracorporeal esophagojejunostomy after laparoscopy-assisted total gastrectomy (LATG) for gastric cancer can be considered minimally invasive surgery, compared to the conventional open total gastrectomy (OTG). PATIENTS AND METHODS: This retrospective study involved 60 patients seen between January 2004 and July 2006. Twenty-seven patients underwent LATG, and 33 patients had OTG. The surgical procedure included the use of five ports with an upper vertical midline incision. In all patients, reconstruction was performed by using a Roux-en-Y esophagojejunostomy through the minilaparotomy site. In all cases, the jejunojejunostomy was performed extracorporeally as the conventional method. In OTG, a Roux-en-Y esophagojejunostomy was performed with an upper midline incision. RESULTS: The mean number of retrieved lymph nodes was smaller and the mean operating time was longer in the LATG group. The postoperative hospital course was similar in both groups. In the LATG group, the mean length of the minilaparotomy incision was 8.0+/-1.2 cm (maximum length, 11 cm), and a direct relationship was observed between the distance from the xiphoid process to the esophageal hiatus (DisXE) and the minilaparotomy incision length (Spearman's correlation of rank coefficient: 0.386; P=0.046). CONCLUSIONS: With the concept of minimal invasiveness, if the patient's DisXE exceeds 9 cm, the length of the minilaparotomy incision in laparoscopic surgery could be disadvantageous. Nevertheless, we consider LATG the treatment of choice for early gastric cancer. If the patient's DisXE exceeds 9 cm, we consider intracorporeal anastomosis with the laparoscopic total gastrectomy. The type of esophagojejunostomy may be determined preoperatively by using three-dimensional abdominal computed tomography.
Assuntos
Esofagostomia/métodos , Gastrectomia/métodos , Jejunostomia/métodos , Laparoscopia , Neoplasias Gástricas/cirurgia , Anastomose em-Y de Roux , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Procedimentos Cirúrgicos Minimamente Invasivos , Estudos RetrospectivosRESUMO
Pseudomembranous colitis (PMC) is known to develop after antibiotic administration, but antituberculosis agents are rarely associated with this disorder. We report 6 cases of PMC after rifampicin administration; the clinical manifestations, laboratory findings, imaging findings, and clinical course are described. The median age of patients was 68 years (range, 54 to 82 y). All patients were diagnosed with active pulmonary tuberculosis by sputum smear and culture, and 2 suffered from type 2 diabetes mellitus. The average interval between initiation of antituberculosis therapy and the onset of diarrhea was 19.8 days. The anatomic distribution of PMC included the rectum and sigmoid colon in 5 cases and up to the hepatic flexure in 1 case. All patients were cured with medical treatment, which include discontinuation of rifampicin and oral metronidazole and vancomycin. PMC recurred in 1 patient after retreatment with rifampicin. Our findings suggest that patients who are treated with antituberculosis agents, who develop acute diarrhea during or after therapy, should be evaluated for PMC.