Voltage controlled sub-THz detection with gated planar asymmetric nanochannels

[EN]This letter reports on room temperature sub-THz detection using self-switching diodes based on an AlGaN/GaN heterostructure on a Si substrate. By means of free-space measurements at 300 GHz, we demonstrate that the responsivity and noise equivalent power (NEP) of sub-THz detectors based on planar asymmetric nanochannels can be improved and voltage controlled by means of a top gate electrode. A simple quasi-static model based on the DC measurements of the current-voltage curves is able to predict the role of the gate bias in its performance. The best values of voltage responsivity and NEP are achieved when the gate bias approaches the threshold voltage, around 600 V/W and 50 pW/Hz1/2, respectively. A good agreement is found between modeled results and those obtained from RF measurements under probes at low frequency (900MHz) and in free-space at 300 GHz

Early Reactional Hyperplasia and Neuronal Differentiation of the Ciliary Epithelium (CE) in Experimental Retinal Detachment (RD) with Proliferative VitreoRetinopathy (PVR) in the Porcine Eye

Background: Rare quiescent retinal progenitor cells have been isolated in the adult amphibian ciliary marginal zone (Hollyfield, 1968), then in the mammalian (Tropepe et al, 2000) (Ahmad et al, 2000) (Fischer and Rey, 2000) and human CE (Coles et al, 2004) (Ballios et al, 2011). This contingent might be inhibited in the adult eye by the signaling pathway ephrin (Chen, personal communication, ARVO 2012, submitted, Stem Cells). Retinal injury might be a triggering factor to quit the dormant state in the adult mammalian CE (Ooto, 2004) (Nickerson, 2007) (Nishiguchi 2008) (Kiyama et Wang, 2010), as it has been demonstrated also in the human brain (Moe et al, 2005) (Logan et al, 2006) . We have reported a CE proliferation with retinal neuronal and photoreceptor differentiation in three human eyes eviscerated for longstanding RD and PVR (Ducournau et al 2012). The CE strongly expressed EGFR. The concept of niche (Fischer and Rey, 2003) is now well established in stem cells recruitment processes. We have hypothezised that the disease RD and PVR might stimulate a dormant population of Retinal Progenitor Cells (RPCs) in the CE in the human eye in vivo in presence of a niche constituted by EGF. Proliferation in the ciliary body, together with nestin expression in ciliary MCM2+ (macrophage/microglia marker F4/80) cells were found in mice eyes with experimental RD, suggesting that RD might activate putative RPCs (Suburo et al, 2010). The aim of the present work was to study the CE in the porcine eye with experimental DR and PVR

Coherent THz communication at 200 GHz using a frequency comb, UTC-PD and electronic detection

A coherent terahertz (THz) link at 200 GHz , with a variable data rate up to 11 Gbit/s, featuring a very high sensitivity at the receiver, is investigated. The system uses a quasi-optic unitravelling carrier photodiode (UTC-PD) emitter and an electronic receiver. The coherent link relies on an optical frequency comb generator at the emission to produce an optical beat note with 200 GHz separation, phase-locked with the receiver. Bit error ratio testing has been carried out using an indoor link configuration, and error-free operation is obtained up to 10 Gbit/s with a received power <2 μW

GaN Schottky Diode for High Power THz Generation using Multiplier Principle

International audienceGaN-based planar Schottky barrier diodes with potential applications in THz frequency multipliers were fabricated and characterized. GaN is a promising candidate to overcome all the physical limitations of GaAs which have been reached in the frame of high frequency power multiplier applications. Fabrication process of GaN Schottky diodes performed by e-beam is presented and DC characterizations are reported. The preliminary results showed that the behaviour in reverse bias is dominated by a leakage coming from the Schottky surface more than the periphery of the diode despite the supposed damage caused by the dry etching

Sources térahertz pour l'astronomie et l'astrophysique et perspectives des multiplicateurs GaN Schottky

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