Extraordinary optical transmission through metal gratings with single and double grooved surfaces

We investigate the transmission properties of a normally incident TM plane wave through metal films with periodic parabolic-shaped grooves on single and double surfaces using the finite-difference-time-domain method. Nearly zero transmission efficiency is found at wavelengths corresponding to surface plasmon excitation on a flat surface in the case where the single surface is grooved. Meanwhile, resonant excitation of surface plasmon polariton (SPP) Bloch modes leads to a strong transmission peak at slightly larger wavelengths. When the grating is grooved on double surfaces, the transmission enhancement can be dramatically improved due to the resonant tunnelling between SPP Bloch modes.     

Phase control in an open Λ-type system with spontaneously generated coherence

This paper investigates the control role of the relative phase between the probe and driving fields on the gain, dispersion and populations in an open A system with spontaneously generated coherence （SGC）. It shows that by adjusting the value of the relative phase, a change from lasing with inversion to lasing without inversion can be realized; the values and frequency spectrum regions of the inversionless gain and dispersion can be obviously varied; high refractive index with zero absorption and electromagnetically induced transparency can be achieved. It is also found that when the driving field is resonant, the shapes of the dispersion and the gain curves versus the probe detuning are very similar if the relative phase of the dispersion lags π/2 than that of the gain, however for the off-resonant driving field the similarity will disappear; the gain, dispersion and populations are periodical functions of the relative phase, the modulation period is always 2π; the contribution of SGC to the inversionless gain and dispersion is much larger than that of the dynamically induced coherence.     

Manipulation role of the relative phase and incoherent pumping on a light pulse propagation

In an open A type system with the spontaneously generated coherence (SGC), when the probe and driving fields have different frequencies, the switching of the group velocity of the probe pulse from subluminal to superluminal is realized not only by adjusting values of the relative phase between the probe and driving fields but also by varying values of the incoherent pumping rate. For the subluminal propagation, the system always exhibits the probe absorption, however, the superluminal propagation is always companied with gain of the probe field.     

Lasing with and without inversion due to spontaneously generated coherence in an open V-type system

It is shown that in an open V-type atomic system without incoherent pumping, the spontaneously generated coherence (SGC) can not only lead to lasing with inversion but also lead to lasing without inversion (LWI)including at resonance of the driving and probe fields. This conclusion is much different from that obtained in the corresponding closed V-type system.     

Lasing with and without inversion due to spontaneously generated coherence in an open V-type system

It is shown that in an open V-type atomic system without incoherent pumping, the spontaneously generated coherence (SGC) can not only lead to lasing with inversion but also lead to lasing without inversion (LWI) including at resonance of the driving and probe fields. This conclusion is much different from that obtained in the corresponding closed V-type system.     

Nonlinear dynamics study of an open resonant Λ-type system

Quantum coherence and interference in atomic systemshave a number of important consequences, includinglasing without inversion (LWI), the electromagneticallyinduced transparency, coherent population trapping, thesubrecoil cooling of atoms, potentiality for sensitive mea-surements of magnetic fields, and so on. In particular,LWI has attracted much more attention[1-12] and havebeen studied in the past few decades. The open Λ-typethree-level system for LWI is proposed[13-14]. From thenonline…