Graphene is a promising candidate in analog electronics with projected operation frequency well into the terahertz range. In contrast to the intrinsic cutoff frequency (f) of 427 GHz, the maximum oscillation frequency (f) of graphene device still remains at low level, which severely limits its application in radio frequency amplifiers. Here, we develop a novel transfer method for chemical vapor deposition graphene, which can prevent graphene from organic contamination during the fabrication process of the devices. Using a self-aligned gate deposition process, the graphene transistor with 60 nm gate length exhibits a record high f of 106 and 200 GHz before and after de-embedding, respectively. This work defines a unique pathway to large-scale fabrication of high-performance graphene transistors, and holds significant potential for future application of graphene-based devices in ultra high frequency circuits.
We experimentally demonstrate a high-spectral-purity photon source by designing a dual-Mach–Zehnder-interferometer-coupled silicon ring resonator, wherein the linewidths of pump and signal (idler) resonances can be engineered independently. A high spectral purity of
95
%
±
1.5
%
is obtained via a time-integrated
g
(
2
)
correlation measurement, which exceeds the theoretical 93% bound of a traditional ring’s spontaneous four-wave-mixing photon source. This source also possesses high performance in other metrics including a measured coincidence of 9599 pairs/s and a preparation heralding efficiency of 52.4% at a relatively low pump power of 61 µW as well as high drop-to-through suppression of 20.2 dB. By overcoming the trade-off between spectral purity and brightness in the post-filtering way, such a method guarantees bright pure photons and will pave the way for development of on-chip quantum information processing with improved operation fidelity and efficiency.
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