Prospects of coherent control in turbid media: Bounds on focusing broadband laser pulses

Abstract

We study the prospects of controlling transmission of broadband and bichromatic laser pulses through turbid samples. The ability to focus transmitted broadband light is limited via both the scattering properties of the medium and the technical characteristics of the experimental setup. There are two time scales given by pulse stretching in the near-and far-field regions which define the maximum bandwidth of a pulse amenable to focusing. In the geometric-optics regime of wave propagation in the medium, a single setup can be optimal for focusing light at frequencies ω and nω simultaneously, providing the basis for the 1 + n coherent quantum control. Beyond the regime of geometric optics, we discuss a simple solution for the shaping, which provides the figure of merit for one's ability to simultaneously focus several transmission modes.

Focusing large spectral bandwidths through scattering media

“…The most frequent examples are multicolour multiphoton fluorescence imaging [10] [11], four wave mixing, coherent anti stokes Raman scattering (CARS) [12], and sum frequency generation (SFG) [13]. These situations are very challenging for wavefront shaping since coherent manipulation of waves through a scattering medium is only applicable within a wavelength range below the spectral bandwidth of the medium [14][ [15] [16] [17]. This bandwidth, which represents the number of independent spectral modes of the medium, is generally assessed by its speckle spectral correlation bandwidth [16] [18] and does not surpass a few tens of nanometers in millimetre-thick biological media [19].…”

Mutual extinction and transparency of multiple incident light waves

“…Theoretical efforts have been made to understand WFS in terms of the correlations in the transmitted light, see, for example, refs. [16][17][18]. In addition studies were made of advanced algorithms used to find the optimal wavefront, e.g., in refs.…”

Non-adiabatic control of quantum energy transfer in ordered and disordered arrays

“…Although the focusing method demonstrated in sections 3 and 6 appears to be robust in the presence of a disorder potential induced by a small concentration of vacancies, it is important for practical applications to also consider controlled energy transfer in quantum arrays under a strong disorder potential. To consider focusing in a strongly disordered system, we employ an analogy with the 'transfer matrix' methods for focusing of a collimated light beam in opaque medium [50][51][52][53][54][55][56][57][58][59].…”

“…via resonance fluorescence from the target molecule at the end of the experiment. More sophisticated optimization techniques, aimed at fast focusing multi-frequency light in optical systems, are currently under rapid development [51][52][53][54][55][56][57][58][59].…”