Safety of goods and civilians towards the terrorist risk constitutes a research orientation of public interest, confirmed by the 2013 edition of the “Livre blanc de la Défense et de la Sécurité Nationale”. In particular, the risk of Nuclear or Radiological attack remains one probable and serious risk, following the emergence of nations sufficiently developed and favorable to develop this kind of armament. In this context, it is important to have passive detection of ionizing rays. In our case, we take interest in the detection of neutrons, immutable signature of the presence of materials allowing the preparation of nuclear weapons. In addition to the societal aspect, the economic aspect is crucial because such detectors, containing 3He gas, currently exist, but their lack prevents their deployment on large surfaces. We thus wish to develop polymeric materials allowing the detection of these neutrons at lower costs, as well as a prototype containing these sensors.

Green laser light sources are key devices to enable development of bright full-colour projection displays, biomedical instrumentation, medical imaging, high-speed short distance data communications using plastic fibres, and efficient solid-state lighting. Up to now, however, frequency doubling of infrared lasers is the most common approach, whereas compact true green laser diodes are still to be demonstrated.Present Gallium Nitride (GaN) based blue laser diodes are making their way into applications but are still limited to wavelengths below 470 nm. As the main reason, the large strain between active, waveguiding, and cladding layers of such laser diodes has been identified.In the present project, we aim to take advantage of strain-control technology which becomes possible through the use of quaternary AlGaInN and ternary AlInN in the cladding and waveguiding layers. Through improved refractive index contrast, superior waveguiding properties for the green spectral region can be realized. Ultra-narrow GaInN quantum wells with high Indium content (>35%) will be at the core of the active region to minimize the influence of piezoelectric polarization fields. Finally, low-defect-density GaN substrates will enable low threshold and high slope efficiency laser diodes with long prospective device lifetimes.The transnational consortium (ERASPOT submission) assembled in this proposal provides the critical mass of researchers and facilities to allow this material and device development. This work requires such a broad range of expertise that no one partner could efficiently address this project in the time required for modern technology developments. The success of previous collaborations demonstrates the ability to combine the individual expertise into joint progress.

We propose to study, develop, fabricate and characterize a novel device able to amplify and generate electromagnetic radiation at THz frequencies made of a field-effect heterostructure transistor (gated or ungated) placed inside a resonator constituted by two mirrors parallel to the channel. The emission of radiation is perpendicular to the channel through the transistor surface. The mechanism at the basis of the amplification of the electromagnetic wave is a quasi-ballistic acceleration of electrons followed by a fast emission of polar optical phonons, the so-called optical phonon transit time resonance (OPTTR). The conditions necessary to achieve the resonance are the absence of interactions at low energies and a very sharp energy threshold for the emission of optical phonons: these two conditions can be satisfied exploiting the special transport properties of nitrides which are much more adapted than standard III-V materials. The active (i.e. amplifying) region is represented by the bidimensional electron gas created by the confining potential inside the quantum well at the AlGaN/GaN heterojunction. The cyclic movement of electrons in the phase space enables the amplification of electromagnetic waves in a restricted frequency range given by the inverse of the transit time in the phase space. For electric fields of reasonable strength (some kV/cm), this frequency lies in the THz range. The main advantages of the proposed device with respect to existing devices are: 1) a wide range of working temperatures which includes also the liquid nitrogen temperature; 2) high values of the maximum amplification coefficient; 3) wide tuning of the generation frequency, which covers most of the THz range and is obtained by sweeping the applied voltage only; 4) absence of a magnetic field, which simplifies considerably the device design; 5) very narrow amplification band, which is useful for realizing the single-mode generation; 6) simple design favourable to integration in circuits.