Investigation of the Optical Nonlinearity for Au Plasmonic Nanoparticles Based on Ion Implantation.

The Au ion implantation process has emerged as an effective and simple method to be utilized for the fabrication of opto-electronic materials and devices due to numerous fascinating features of Au nanoparticles such as surface plasmon resonance (SPR), large third-order nonlinearity and a fast response time. In this paper, we describe the fabrication of a novel Au nanoparticle saturable absorber (Au NP-SA) by embedding the Au NPs into a SiO2 thin film using the ion implantation process, which shows excellent saturable absorption features due to the localized surface plasmon resonance (LSPR) effect of Au NPs. A stable and high-quality pulsed laser with a repetition rate of 33.3 kHz and a single pulse energy of 11.7 nJ was successfully constructed with the Au NP-SA. Both the stable operation characteristic of the obtained Q-switched pulsed laser and the high repeatability of the fabrication process of the Au NP-SA were demonstrated. In addition, the simple feasibility and maturity of the ion implantation process allow for the plasmonic nanoparticles to be easily integrated into other types of opto-electronic materials and devices to further improve their performance, and shows immense potential for the production of wafer-level products.

Broadband Quantum Dot Superluminescent Diode with Simultaneous Three-State Emission.

Semiconductor superluminescent light-emitting diodes (SLEDs) have emerged as ideal and vital broadband light sources with extensive applications, such as optical fiber-based sensors, biomedical sensing/imaging, wavelength-division multiplexing system testing and optoelectronic systems, etc. Self-assembled quantum dots (SAQDs) are very promising candidates for the realization of broadband SLED due to their intrinsic large inhomogeneous spectral broadening. Introducing excited states (ESs) emission could further increase the spectral bandwidth. However, almost all QD-based SLEDs are limited to the ground state (GS) or GS and first excited state (ES1) emission. In this work, multiple five-QD-layer structures with large dot size inhomogeneous distribution were grown by optimizing the molecular beam epitaxy (MBE) growth conditions. Based on that, with the assistance of a carefully designed mirror-coating process to accurately control the cavity mirror loss of GS and ESs, respectively, a broadband QD-SLED with three simultaneous states of GS, ES1 and second excited-state (ES2) emission has been realized, exhibiting a large spectral width of 91 nm with a small spectral dip of 1.3 dB and a high continuous wave (CW) output power of 40 mW. These results pave the way for a new fabrication technique for high-performance QD-based low-coherent light sources.

Recent Developments of Quantum Dot Materials for High Speed and Ultrafast Lasers.

Owing to their high integration and functionality, nanometer-scale optoelectronic devices based on III-V semiconductor materials are emerging as an enabling technology for fiber-optic communication applications. Semiconductor quantum dots (QDs) with the three-dimensional carrier confinement offer potential advantages to such optoelectronic devices in terms of high modulation bandwidth, low threshold current density, temperature insensitivity, reduced saturation fluence, and wavelength flexibility. In this paper, we review the development of the molecular beam epitaxial (MBE) growth methods, material properties, and device characteristics of semiconductor QDs. Two kinds of III-V QD-based lasers for optical communication are summarized: one is the active electrical pumped lasers, such as the Fabry-Perot lasers, the distributed feedback lasers, and the vertical cavity surface emitting lasers, and the other is the passive lasers and the instance of the semiconductor saturable absorber mirrors mode-locked lasers. By analyzing the pros and cons of the different QD lasers by their structures, mechanisms, and performance, the challenges that arise when using these devices for the applications of fiber-optic communication have been presented.

Changing Pain Management Strategy from Opioid-centric Towards Improve Postoperative Cognitive Dysfunction with Dexmedetomidine.

OBJECTIVE: This study was aimed to investigate the effectiveness of dexmedetomidine (DEX) on improving the level of pain and disability to find out the possible correlation between psychological factors with pain management satisfaction and physical function in patients with femoral neck fractures. METHODS: One hundred twenty-four adult patients with stable femoral neck fractures (type I and II, Garden classification) who underwent internal fixation, were prospectively enrolled including 62 patients in the DEX group and 62 patients in the control group. The magnitude of disability using Harris Hip Score, Postoperative Cognitive Dysfunction (POCD) using Mini-Mental State Examination (MMSE score), Quality of Recovery (QoR-40), pain-related anxiety (PASS-20), pain management and pain catastrophizing scale (PCS) were recorded on the first and second day after surgery. RESULTS: The DEX group on the first and second days after surgery exhibited higher quality of recovery scores, greater satisfaction with pain management, low disability scores, less catastrophic thinking, lower pain anxiety, greater mini mental state examination scores and less opioid intake and the differences were statistically significant compared with the control group (P<0.001). Emergence agitation and incidence of POCD were significantly less in the DEX group (P<0.001). Decreased disability was associated with less catastrophic thinking and lower pain anxiety, but not associated with more opioid intake (P<0.001). Higher QoR-40 scores had a negative correlation with more catastrophic thinking and more opioid intake (P<0.001). Greater satisfaction with pain management was correlated with less catastrophic thinking and less opioid intake (P<0.001). CONCLUSION: Using DEX as an adjunct to anesthesia could significantly improve postoperative cognitive dysfunction and the quality of recovery and these improvements were accompanied by decrease in pain, emergence agitation, and opioid consumption by DEX administration. Since pain relief and decreased disability were not associated with prescribing greater amounts of opioid intake in the patients, improving psychological factors, including reducing catastrophic thinking or self-efficacy about pain, could be a more effective strategy to reduce pain and disability, meanwhile reducing opioid prescription in the patients. Our findings showed that DEX administration is safe sedation with anti-inflammatory, analgesic and antiemetic effects and it could help change pain management strategy from opioidcentric towards improved postoperative cognitive dysfunction.

SiO2 Passivated Graphene Saturable Absorber Mirrors for Ultrashort Pulse Generation.

Owing to its broadband absorption, ultrafast recovery time, and excellent saturable absorption feature, graphene has been recognized as one of the best candidates as a high-performance saturable absorber (SA). However, the low absorption efficiency and reduced modulation depth severely limit the application of graphene-based SA in ultrafast fiber lasers. In this paper, a single-layer graphene saturable absorber mirror (SG-SAM) was coated by a quarter-wave SiO2 passivated layer, and a significantly enhanced modulation depth and reduced saturation intensity were obtained simultaneously compared to the SG-SAM without the SiO2 coating layer. In addition, long-term operational stability was found in the device due to the excellent isolation and protection of the graphene absorption layer from the external environment by the SiO2 layer. The high performance of the SAM was further confirmed by the construction of a ring-cavity EDF laser generating mode-locked pulses with a central wavelength of 1563.7 nm, a repetition rate of 34.17 MHz, and a pulse width of 830 fs.