Different Ways To Achieve Slow Light
There are many mechanisms which can generate slow light, all of which create narrow spectral regions with high dispersion, i.e. peaks in the dispersion relation. Schemes are generally grouped into two categories: material dispersion and waveguide dispersion. Material dispersion mechanisms such as Electromagnetically Induced Transparency (EIT), Coherent Population Oscillation (CPO), and various Four Wave Mixing (FWM) schemes produce a rapid change in refractive index as a function of optical frequency, i.e. they modify the temporal component of a propagating wave. This is done by using a nonlinear effect to modify the dipole response of a medium to a signal or "probe" field. Waveguide dispersion mechanisms such as photonic crystals, Coupled Resonator Optical Waveguides (CROW), and other micro-resonator structures modify the spatial component (k-vector) of a propagating wave. Slowlight can also be achieved exploiting the dispersion properties of planar waveguides realized with single negative metamaterials (SNM) or double negative metamaterials (DNM).
A predominant figure of merit of slow light schemes is the Delay-Bandwidth Product (DBP). Most slow light schemes can actually offer an arbitrarily long delay for a given device length (length/delay = signal velocity) at the expense of bandwidth. The product of the two is roughly constant. A related figure of merit is the fractional delay, the time a pulse is delayed divided by the total time of the pulse. Plasmon induced transparency – an analog of EIT - provides another approach based on the destructive interference between different resonance modes. Recent work has now demonstrated this effect over a broad transparency window across a frequency range greater than 0.40 THz
Read more about this topic: Slow Light
Famous quotes containing the words ways, achieve, slow and/or light:
“Humility is often merely feigned submissiveness assumed in order to subject others, an artifice of pride which stoops to conquer, and although pride has a thousand ways of transforming itself it is never so well disguised and able to take people in as when masquerading as humility.”
—François, Duc De La Rochefoucauld (16131680)
“As long as they desire the same object, they are of one mind, but having to achieve the same thing immediately disrupts their unanimity.”
—Franz Grillparzer (17911872)
“See, they return; ah, see the tentative
Movements, and the slow feet,
The trouble in the pace and the uncertain
Wavering!”
—Ezra Pound (18851972)
“Mysterious Night! when our first parent knew
Thee from report divine, and heard thy name,
Did he not tremble for this lovely frame,
This glorious canopy of light and blue?”
—Joseph Blanco White (17751841)