Iterative creation and sensing of twisted light

Abstract

The iterative interaction of a photon with a sample can lead to increased sensitivity in measuring the properties of the samples, such as its refractive index or birefringence. Here we show that this principle can also be used to generate and sense states of light. In particular, we demonstrate a technique to generate states with high orbital angular momentum using a single-vortex phase plate (VPP). This is accomplished by placing the phase plate in a self-imaging cavity such that light interacts with it multiple times; for an ideal phase plate, this is equivalent to iterative applications of the angular momentum operator. Using a discrete VPP, we show that our setup realizes a high-dimensional generalization of the Pauli matrix σ_x, and that the created states show sub-diffraction limited features that might find applications in structured illumination microscopy.

Local Optimization of Wave-fronts for optimal sensitivity PHase Imaging (LowPhi)

“…We stress however, that the principle can also be applied to techniques using an external reference wave, in which either the reference or the signal wave can be reshaped to guarantee optimal sensitivity. Besides high speed quantitative studies of cell dynamics and morphology, LowPhi may also find use in multi-pass microscopy [19,20] to avoid phase wrapping problems. To achieve this, an SLM would have to be incorporated within the self-imaging cavity of a multi-pass microscope, again in a plane that is conjugate to the sample.…”

Full-field cavity enhanced microscopy techniques

“…MP microscopy [4,5] has recently been demonstrated to allow for increased signal-to-noise per photon-sample interaction as compared to traditional single-pass microscopy. Here we showed analytically and numerically that this is also true in RD and CW approaches, in which the enhanced interaction strength is set by the finesse of the cavity.…”

“…At this wavelength BN has a refractive index of 1.8 [29], where the imaginary part is negligible due to the large bandgap of 5 eV [30]. The susceptibility of the two materials can be obtained from (5). The thickness of a monolayer of graphene and BN is 3.35 Å and 3.33 Å [29], respectively.…”

“…SNR at constant damage as in figure 3, but with a sample holder of thickness n g kd g =π at n g =1. 5. Once again, we chose the optimal cavity length for BF (green), DF (black), Znk+ (red), and Znk− (blue).…”

“…Cavity enhanced measurements are ubiquitous in science and technology. In microscopy, the offered sensitivity enhancement has for example been exploited in cavity scanning microscopy [1,2], in Tolansky interferometry [3] and in multi-pass (MP) microscopy [4,5]. While the former represents a point scanning technique, in which a fiber based microcavity is scanned across a sample, the latter two offer a full field of view.…”