196 research outputs found
Methods of accounting for waste in a cotton spinning mill
The problem of waste or scrap material is of great importance and is difficult to account for in any manufacturing concern. The purpose of this article is not to discuss the problem as applied to all industries but to treat the various aspects of it that arise in a cotton yarn spinning mill. However, some of the general principles mentioned may also apply to other industries
Ultrafast Opto-Electronic and Thermal Tuning of Third-Harmonic Generation in a Graphene Field Effect Transistor
Graphene is a unique platform for tunable opto-electronic applications thanks
to its linear band dispersion, which allows electrical control of resonant
light-matter interactions. Tuning the nonlinear optical response of graphene is
possible both electrically and in an all-optical fashion, but each approach
involves a trade-off between speed and modulation depth. Here, we combine
lattice temperature, electron doping, and all-optical tuning of third-harmonic
generation in a hBN-encapsulated graphene opto-electronic device and
demonstrate up to 85% modulation depth along with gate-tunable ultrafast
dynamics. These results arise from the dynamic changes in the transient
electronic temperature combined with Pauli blocking induced by the
out-of-equilibrium chemical potential. Our work provides a detailed description
of the transient nonlinear optical and electronic response of graphene, which
is crucial for the design of nanoscale and ultrafast optical modulators,
detectors and frequency converters.Comment: 28 pages, 6 figure
Valley Polarization-Electric Dipole Interference and Nonlinear Chiral Selection Rules in Monolayer WSe
In monolayer transition metal dichalcogenides time-reversal symmetry,
combined with space-inversion symmetry, defines the spin-valley degree of
freedom. As such, engineering and control of time-reversal symmetry by optical
or magnetic fields constitutes the foundation of valleytronics. Here, we
propose a new approach for the detection of broken time-reversal symmetry and
valley polarization in monolayer WSe based on second harmonic generation.
Our method can selectively and simultaneously generate and detect a valley
polarization at the valleys of transition metal dichalcogenides at room
temperature. Furthermore, it allows to measure the interference between the
real and imaginary parts of the intrinsic (electric dipole) and valley terms of
the second order nonlinear susceptibility. This work demonstrates the potential
and unique capabilities of nonlinear optics as a probe of broken time-reversal
symmetry and as a tool for ultrafast and non-destructive valleytronic
operations.Comment: 27 pages 6 figure
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