White light conical diffraction

Abstract

We use the Bloch-Redfield-Wangsness theory to calculate the effects of acoustic phonons in coherent control experiments where quantum-dot excitons are driven by shaped laser pulses. This theory yields a generalized Lindblad equation for the density operator of the dot, with time-dependent damping and decoherence due to phonon transitions between the instantaneous dressed states. It captures similar physics to the form recently applied to Rabi oscillation experiments [Ramsay et al., Phys. Rev. Lett. 104, 017402 (2010)] but guarantees positivity of the density operator. At sufficiently low temperatures, it gives results equivalent to those of fully non-Markovian approaches [Lüker et al., Phys. Rev. B 85, 121302 (2012)] but is significantly simpler to simulate. Several applications of this theory are discussed. We apply it to adiabatic rapid passage experiments and show how the pulses can be shaped to maximize the probability of creating a single exciton using a frequency-swept laser pulse. We also use this theory to propose and analyze methods to determine the phonon density of states experimentally, i.e., phonon spectroscopy, by exploring the dependence of the effective damping rates on the driving field.

Conical refraction: fundamentals and applications

“…One of the advantages of our technique is that CR provides the full conversion of the input power into the 3D dark focus and avoid diffraction losses, in contrast to other methods based on spatial light modulators (SLMs), for instance, which introduce losses due to diffraction in the generation of LG beams. Moreover, biaxial crystals can be transparent to an extremely wide spectral range [214] (0.35 µm-5.5 µm in KGd(WO 4 ) 2 , for instance), at variance with SLMs which only work in a short spectral range usually of few hundreds of nm. These features make the 3D dark focus beam very attractive for particle manipulation [142,143] and atom [185,200] trapping.…”

Conical refraction with low-coherence light sources

“…A similar technique was used in the first CR experiments performed long before the introduction of lasers. Also, a collimating lens can be replaced with an iris aperture as demonstrated in a recent publication on white-LED-light CR [21].…”

Extreme Ultraviolet Fractional Orbital Angular Momentum Beams from High Harmonic Generation

“…Therefore, our method can be feasibly experimentally implemented with the current technology. On the other hand, the spectral bandwidth in the visible domain tolerated by the crystal is of Δ λ  = 100 nm due to dispersion46, which causes a dependence between the direction of the optic axis and the wavelength of the input beam. This restricts the use of short pulses down to Fourier limited ≈8.8 fs at full-width-half-maximum (FWHM) for a central wavelength λ 0  = 800 nm.…”