RESUMO
Due to their low phase noise at high carrier frequencies, photonic microwave oscillators are continuously expanding their application areas including digital signal processing, telecommunications, radio astronomy, and RADAR and LIDAR systems. Currently, the lowest noise photonic oscillators rely on traditional optical frequency combs with multiple stabilization loops that incorporate large vacuum components and complex optoelectronic configurations. Hence, the resulting systems are not only challenging to operate but also expensive to maintain. Here, we introduce a significantly simpler solution: a Photonically Referenced Extremely STable Oscillator (PRESTO). PRESTO requires only three key components: a femtosecond laser, a fiber delay element, and a pulse timing detector. The generated microwave at 10â GHz has phase noise levels of -125, -145, and <-160â dBc/Hz at 1, 10, and >100â kHz, respectively, with an integrated timing jitter of only 2â fs root mean square (RMS) over [100â Hz-1â MHz]. This approach offers a reliable solution for simplifying and downsizing photonic oscillators while delivering high performance.
RESUMO
Tetraiodotetraazapentacene I4 TAP, the last missing derivative in the series of halogenated silylated tetraazapentacenes, was synthesized via condensation chemistry from a TIPS-ethynylated diaminobenzothiadiazol in three steps. Single and double reduction furnished its air-stable monoanion and relatively air-stable dianion, both of which were characterized by crystallography. All three species are structurally and spectroscopically compared to non-halogenated TAP and Br4 TAP. I4 TAP is an n-channel material in thin-film transistors with average electron mobilities exceeding 1â cm2 (Vs)-1 .
Assuntos
Elétrons , Semicondutores , Transporte de Elétrons , ÂnionsRESUMO
A revised synthesis of Martin's phosphino-triols (two derivatives) is reported. Once isolated, these thermally sensitive triols were shown to disassemble selectively via an unexpected P-C bond cleavage reaction. This degradation pathway was effectively suppressed via complexation of Al3+ and Sc3+. In the resulting half-cage complexes, the ligand scaffold is bound to each metal (Al3+ and Sc3+, respectively) via all four donor atoms. So far, this κ4-P,O,O',Oâ³-coordination mode has not been observed for any other phosphino-triol.