A hybrid single-mode laser based on slotted silicon waveguides

An InGaAsP-Si hybrid single-mode laser based on etched slots in silicon waveguides was demonstrated operating at 1543 nm. The InGaAsP gain structure was bonded onto a patterned silicon-on-insulator wafer by selective area metal bonding method. The mode-selection mechanism based on a slotted silicon waveguide was applied, in which the parameters were designed using the simulation tool cavity modeling framework. The III-V lasers employed buried ridge stripe structure. The whole fabrication process only needs standard photolithography and inductively coupled plasma etching technology, which reduces cost for ease in technology transfer. At room temperature, a single mode of 1543-nm wavelength at a threshold current of 21 mA with a maximum output power of 1.9 mW in continuous-wave regime was obtained. The side mode suppression ratio was larger than 35 dB. The simplicity and flexibility of the fabrication process and a low cost make the slotted hybrid laser a promising light source

Hybrid InGaAsP-Si Evanescent Laser by Selective-Area Metal-Bonding Method

A 1.55-mu m InGaAsP-Si hybrid laser operating at 10 degrees C under continuous-wave operation is fabricated using a selective-area metal-bonding method with AuGeNi/Au on InGaAsP gain structure as both cathode and bonding metal and AuSn on silicon-on-insulator (SOI) as bonding metal. The maximum single-facet output power is 9 mW. The slope efficiency of the hybrid laser is 0.04 W/A, four times that of the laser before bonding. A semi-insulating InP:Fe buried heterostructure laser is flip-chip bonded onto an SOI waveguide. The light generated in the active area is evanescently coupled into the silicon waveguide. The simplicity and flexibility of the fabrication process and high yield make the hybrid laser a promising light source.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000319995900024&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Engineering, Electrical & ElectronicOpticsPhysics, AppliedSCI(E)EI11ARTICLE121180-11832

1550-nm evanescent hybrid InGaAsP–Si laser with buried ridge stripe structure

An evanescently coupled InGaAsP-Si hybrid laser with a buried ridge stripe (BRS) structure based on a selective area metal bonding method is demonstrated. There are the advantages of good optical field, high thermal performance, and improved carrier and photon confinement by adopting this BRS laser structure. The III-V waveguide with the first-order grating corrugations is fabricated by conventional holographic lithography and standard photolithography. A threshold current as low as 5 mA at room temperature in continuous-wave operation and a side-mode suppression ratio as high as 40 dB with mode-hop free higher than 45 °C were achieved

Anion Specificity of Polyzwitterionic Brushes with Different Carbon Spacer Lengths and Its Application for Controlling Protein Adsorption

Both ion-specific interaction and carbon spacer length have strong effects on the properties of polyzwitterions. In this work, we have investigated the anion specificity of poly­(sulfobetaine methacrylamide) (PSBMAm) brushes with different carbon spacer lengths. The effectiveness of anions to enhance the hydration of the PSBMAm brushes increases from kosmotropic to chaotropic anions. The interactions between the anions and the PSBMAm brushes are strongly influenced by carbon spacer length because the strength of inter/intrachain association of the PSBMAm brushes decreases with increasing carbon spacer length. The inter/intrachain association of the PSBMAm brushes with a longer carbon spacer is easier to break by the external anions in the high salt concentration regime. On the other hand, a longer carbon spacer is more favorable for the zwitterionic groups to form cyclic intramolecular structures. As a result, the addition of anions can more effectively enhance the hydration of the PSBMAm brushes with a medium-length carbon spacer compared with that of the PSBMAm brushes with a either shorter or longer carbon spacer in the low salt concentration regime, determined by the balance between the inter/intrachain association and the formation of cyclic intramolecular structures. Our study also demonstrates that both anion identity and carbon spacer length can be used to control protein adsorption on the surface of the PSBMAm brushes

Wide range tuning of the size and emission color of CH3NH3PbBr3 quantum dots by surface ligands

Organic-inorganic halide perovskite CH3NH3PbX3 (X= I, Br, Cl) quantum dots (QDs) possess the characters of easy solution-process, high luminescence yield, and unique size-dependent optical properties. In this work, we have improved the nonaqueous emulsion method to synthesize halide perovskite CH3NH3PbBr3 QDs with tunable sizes. Their sizes have been tailored from 5.29 to 2.81 nm in diameter simply by varying the additive amount of surfactant, n-octylamine from 5 to 120 μL. Correspondingly, the photoluminescence (PL) peaks shift markedly from 520 nm to very deep blue, 436 nm due to quantum confinement effect. The PL quantum yields exceed 90% except for the smallest QDs. These high-quality QDs have potential to build high-performance optoelectronic devices

Reorganization of hydrogen bond network makes strong polyelectrolyte brushes pH-responsive

Weak polyelectrolytes have found extensive practical applications owing to their rich pH-responsive properties. In contrast, strong polyelectrolytes have long been regarded as pH-insensitive based on the well-established fact that the average degree of charging of strong polyelectrolyte chains is independent of pH. The possible applications of strong polyelectrolytes in smart materials have, thus, been severely limited. However, we demonstrate that almost all important properties of strong polyelectrolyte brushes (SPBs), such as chain conformation, hydration, stiffness, surface wettability, lubricity, adhesion, and protein adsorption are sensitive to pH. The pH response originates from the reorganization of the interchain hydrogen bond network between the grafted chains, triggered by the pH-mediated adsorption-desorption equilibrium of hydronium or hydroxide with the brushes. The reorganization process is firmly identified by advanced sum-frequency generation vibrational spectroscopy. Our findings not only provide a new understanding of the fundamental properties of SPBs but also uncover an extensive family of building blocks for constructing pH-responsive materials

Fully Transparent Quantum Dot Light-Emitting Diode with a Laminated Top Graphene Anode

A new method to employ graphene as top electrode was introduced, and based on that, fully transparent quantum dot light-emitting diodes (T-QLEDs) were successfully fabricated through a lamination process. We adopted the widely used wet transfer method to transfer bilayer graphene (BG) on polydimethylsiloxane/polyethylene terephthalate (PDMS/PET) substrate. The sheet resistance of graphene reduced to ∼540 Ω/□ through transferring BG for 3 times on the PDMS/PET. The T-QLED has an inverted device structure of glass/indium tin oxide (ITO)/ZnO nanoparticles/(CdSSe/ZnS quantum dots (QDs))/1,1-bis­[(di-4-tolylamino)­phenyl] cyclohexane (TAPC)/MoO₃/graphene/PDMS/PET. The graphene anode on PDMS/PET substrate can be directly laminated on the MoO₃/TAPC/(CdSSe/ZnS QDs)/ZnO nanoparticles/ITO/glass, which relied on the van der Waals interaction between the graphene/PDMS and the MoO₃. The transmittance of the T-QLED is 79.4% at its main electroluminescence peak wavelength of 622 nm