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CEOT news!

ALT'15 at the University of Algarve

posted Feb 6, 2014, 4:03 PM by Rui Guerra   [ updated Sep 1, 2014, 4:27 PM ]

The Advanced Laser Technologies (ALT) conference will be held at the University of Algarve in 2015 and is being organized locally by CEOT. The key topics are

  • Sensors
  • Optical communication
  • Quantum interaction and manipulation
  • Laser–matter interaction
  • Biophotonics
  • Laser systems and materials
  • Laser diagnostics and spectroscopy
  • Photoacoustics
  • THz sources and applications

See more details in the site of the conference.

RTD's mimic neuronal phenomena

posted Oct 14, 2009, 11:16 PM by Rui Guerra   [ updated Sep 1, 2014, 4:52 PM ]

The ability to produce narrow optical pulses has been extensively investigated in laser systems with promising applications in photonics such as clock recovery, pulse reshaping, and recently in photonics artificial neural networks using spiking signal processing. The Electronics and Optoelectronics group investigated a neuromorphic opto-electronic integrated circuit (NOEIC) comprising a semiconductor laser driven by a resonant tunneling diode (RTD) photo-detector operating at telecommunication (1550 nm) wavelengths capable of excitable spiking signal generation in response to optical and electrical control signals. The RTD-NOEIC mimics biologically inspired neuronal phenomena and possesses high-speed response and potential for monolithic integration for optical signal processing applications. The work has been published in the SPIE Proceedings 
series (link) and on Optical and Quantum Electronics (link).

New approach to conduction in organic (amorphous) electronic materials

posted Oct 14, 2009, 11:11 PM by Rui Guerra   [ updated Sep 1, 2014, 5:00 PM ]

Organic electronic materials, or amorphous electronic materials in general, have relatively low conductivity and this limits their application to the low-frequency electronics market. To describe electronic conduction in these materials it is common to use percolation or (variable range) hopping theory (the two being equivalent). This is an inheritance from the earlier research in organic materials that were invariably insulators, where conduction was a perturbation – movement of charge was a rare event.

We have published recently an investigation whete it is shown that for electronic materials, instead, it is better to revert to classical semiconductor theories, like band theory. Including a large density of traps in the energy system, all observed phenomena are easily explained. This includes 1. strong temperature dependent charge-carrier mobility, 2. field-dependent mobility, 3. anomalous transient behavior. Moreover, it is consistent with observations in many types of devices, ranging from two-terminal devices such as diodes to three-terminal devices such as thin-film transistors.

Reference: Stallinga, P. (2014), Electrical characterization of organic (amorphous) electronic materials. Phys. Status Solidi C. doi: 10.1002/pssc.201300508

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