Graphene due to its properties, such as high sensitivity and biocompatibility finds application in instruments that are used to cooperation with organic substances. At the same time, from the point of view of sensory devices, it is a material with high absorption potential that is able to improve sensitivity and selectivity of these devices. Another benefit of graphene application may be to use its properties in connection with ISFET – Ion Sensitive Field Effect Transistor, which operation principle is based mostly on detection of changes in hydrogen ions concentration. ISFET transistors ale produced in MOS technology, the difference between them and classic MOSFET (Metal-OxideSemiconductor Field Effect Transistor) structures is gate area, where gate metallization was replaced with reference electrode submerged in solution applied in this area. Properties of the solution determine transistor’s action. It is possible to make modifications in gate area of the structure which effects in changes of transistor’s properties. Example of such a modification may be application of graphene layer, which properties may significantly improve detecting capabilities of ISFET devices. For the needs of the research described in this work, graphene was deposited in gate area of transistors through transfer from cooper and germanium surfaces. To check correctness of ISFETs with graphene layer work, current – voltage characteristics of them were determined. Standard I-V characteristics with SiO2 as gate dielectric were compared with these where gate area was enriched with a graphene layer. Structures with graphene mostly worked properly. Thanks to the results presented in this work, it is possible to carry out further experiments using this structures and organic substances.
We present a graphene-based holmium-doped fiber laser incorporating a Martinez-style compressor which enables precise and continuous dispersion control of the cavity. Solitonic operation of the laser for a wide range of net cavity dispersion values is achieved without significantly altering the repetition frequency. The compressor also provides the possibility to introduce additional spectral filtering - stable mode-locking operation in the 2049- 2093 nm wavelength span is presented.
In this work we propose a simple, all-fiber dispersion managed Ho-doped laser mode-locked with graphene saturable absorber (SA). Dispersion compensating fiber was used to balance the anomalous dispersion of the active and standard single mode fibers, which allows to overcome the limitations set by soliton area theorem. The laser was pumped by a custom-made 1940 nm thulium-doped fiber laser delivering up to 3 W of power. Graphene/PMMA composite sandwiched between fiber connectors serves as a fully fiberized SA. The generated Gaussian pulses centered at 2059 nm reached 53.6 nm of bandwidth. Compressing the pulses by guiding it through SMF-28 fiber yields pulse durations of 190 fs. We also compare the graphene-based laser with a setup mode-locked with nonlinear polarization rotation - an artificial SA.
To the best of our knowledge, this is a first demonstration of a nanomaterial-based stretched pulse fiber laser operating beyond 2 μm. The all-fiber cavity is a more robust alternative to setups that include bulk optics, and requires significantly less alignment compared to lasers mode-locked with real SAs
Epitaxial lift-off (ELO) is a process which enables the removal of solar cell structures (one junction GaAs, two junction GaAs/InGaP or three junction GaAs/InGaAs/InGaP) from the substrate on which they are grown and their transfer onto lightweight carriers such as metal or polymeric insulator films. The said solar cells exhibit superior power conversion efficiency compared with alternative single-junction photovoltaic cell designs such as those based on crystalline Si, copper indium gallium sulfide (CIGS) or CdTe. The major advantage of ELO solar cells is the potential for wafer reuse, which can enable significant manufacturing cost reduction by minimizing the consumption of expensive wafers. Here in this work we have grown one junction GaAs solar cells on GaAs (100) substrates. A 10 nm thick AlAs layer has been used as a release layer, which has been selectively etched in HF solution. We have investigated different methods of transferring thin films onto polymer and copper foils, including the usage of temporary mounting adhesives and electro-conductive pastes. Lift-off has been demonstrated to be a very promising technique for producing affordable solar cells with a very high efficiency of up to 30%.
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