We report on an experimental demonstration of applying the beat-note interferometer to simultaneously measure the phase and amplitude variations of light pulses after propagating through an electromagnetically induced transparency medium at femtowatt-light levels. Furthermore, we observe that the measured phase noise approaches the shot-noise level arising from the fluctuations of detected photons.
We
develop a temperature-programmed pretreatment strategy for converting
aliphatic-rich petroleum pitch into a mesophase framework, which can
then be activated using KOH to produce high-performance carbons for
electric double-layer capacitors (EDLCs). In the pretreatment of pitch
at an optimal temperature, both the temperature ramp and holding time
influence the mesophase structure, which governs the pore structure
and crystallinity of the resulting activated carbon. High carbon microporosity
is beneficial to capacitance maximization but detrimental to ion transport.
To resolve this problem, we develop a multistep ramp incorporating
aliphatic species into the aromatic framework during mesophase formation.
This incorporation process produces a mesophase framework that can
be activated to form carbons with high crystallinity, thereby enhancing
electronic conductivity and hierarchical porosity, which improves
ionic conductivity. The resulting carbon electrode is used to assemble
a symmetric EDLC, which exhibits a capacitance of 160 F g–1 and excellent high-rate retention in a propylene carbonate solution
of N,N-diethyl-N-methylethanaminium tetrafluoroborate. The EDLC delivers a superior
specific energy of 40 Wh kg–1 (based on the total
carbon mass) within a voltage range of 0–2.7 V and sustained
a high energy of 24 Wh kg–1 at a high power of 50
kW kg–1. The findings of this study demonstrate
that incorporating aliphatic species into aromatic mesophase frameworks
plays a crucial role in regulating the crystallinity and pore structure
of pitch-derived carbons for charge storage.
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