Yanfeng Bai

Dressed dynamics of two time-reversed shapes of Airy pulses in a relaxing nonlinear medium

We investigate the dressed dynamics of two kinds of asymmetric Airy pulses with time-reversed shapes in a relaxing nonlinear medium. Airy tails act as low intensity “dressing” pulses, refuel the Airy main lobe, and modify propagation dynamics of Airy pulses. It is demonstrated that a soliton sheds from the main lobe of Airy pulses and the spectrum maximum intensity is periodically manifested due to the effect of self-phase modulation. The intrinsically asymmetric nature of Airy pulses is revealed through the nonlinear generation of a Raman soliton self-frequency shift and the generation of static solitons driven by the soliton fission processes and the interactions with dressing Airy tails. The resulting Raman-induced frequency shift can be controlled by using time-reversed Airy pulses and varying truncation coefficients. Numerical results show that the frequency shift can be enhanced with a larger input peak power as well.

Multi-Solitons Shedding From Truncated Airy Beam in Nonlocal Nonlinear Media

Based on the nonlinear Schrödinger model, the dynamics of truncated Airy beam in nonlocal nonlinear media is investigated. The results show that more spatial solitons are shed from Airy beam in the nonlocal media than the case in the local media. The more shedding solitons can be obtained by increasing the initial intensity or decreasing the truncated coefficient, and these solitons have larger interval because of the nonlocal effect. The shedding multiple spatial solitons of Airy beam can be used as a kind of spatial beam splitter.

Reduction of the defocusing effect in lensless ghost imaging and ghost diffraction with cosh-Gaussian modulated incoherent sources

The inhibition effect from the cosh-Gaussian modulated incoherent source on the defocusing effect is investigated theoretically in lensless ghost imaging (LGI) and ghost diffraction (LGD) systems. The corresponding numerical simulations are presented to show the influence of the cosh-Gaussian incoherent source on the defocusing effect in LGI and LGD. Compared with the widely used Gaussian incoherent source, it is shown that the defocusing effect in LGI and LGD can be greatly weakened by properly adjusting the modulation parameter ω of the cosh-Gaussian source. To explain this phenomenon, the analytical expression for point spread function of the LGI system with the cosh-Gaussian source is derived.

Experimental investigation of ghost imaging of reflective objects with different surface roughness

We present an experimental demonstration of ghost imaging of reflective objects with different surface roughness. The influence of the surface roughness, the transverse size of the test detector, and the reflective angle on the signal-to-noise ratio (SNR) is analyzed by measuring the second-order correlation of the light field based on classical statistical optics. It is shown that the SNR decreases with an increment of the surface roughness and the detector’s transverse size or a decrease of the reflective angle. Additionally, the comparative studies between the rough object and the smooth one under the same conditions are also discussed.

Ghost Imaging for a Reflected Object with Large Incident Angles

Incident angle of light source is a key factor that affects imaging resolution of direct optical imaging for a reflected target. For a large incident angle, it is easy to form the “blind area” in which the image of the object cannot be distinguished clearly. Using classical statistical optics, we study ghost imaging (GI) for a reflected object numerically and experimentally and show that by measuring the second-order correlation of light fields, a ghost-image with good quality can be retrieved in the “blind area.” Unlike transmitted ghost imaging, which is affected greatly by the transverse size of the test detector, the size has almost no effect on the resolution of reflective ghost imaging when the blind area appears.

Potential barrier-induced dynamics of finite energy Airy beams in fractional Schrödinger equation

The dynamics of Airy beams modeled by the fractional Schrodinger equation (FSE) with the potential barrier are numerically investigated. Adjusting the Levy index provides a convenient way to control the diffraction of Airy beams which presents the non-diffraction and splitting property. It has been found that the total reflection of beams occurs when the depth of the single potential barrier exceeds the threshold, and that the number of reflected waves is influenced by the Levy index and the location of potential barrier. However, the periodic self-imaging phenomenon of Airy beams is shown under a symmetric potential barrier when the Levy index is equal to one, and the self-imaging period of the asymmetric Airy beams is analytically demonstrated and is as twice as that of symmetric Gaussian beams, moreover, the chaoticon of light field is formed during propagation as the Levy index increases. All the properties of Airy beams modeled by FSE confirm the potential application in optical manipulation.

Effects of a modulated vortex structure on the diffraction dynamics of ring Airy Gaussian beams

The evolution of the ring Airy Gaussian beams with a modulated vortex in free space is numerically investigated. Compared with the unmodulated vortex, the unique property is that the beam spots first break up, and then gather. The evolution of the beams is influenced by the parameters of the vortex modulation, and the splitting phenomenon gets enhanced with multiple rings becoming light spots if the modulation depth increases. The symmetric branch pattern of the beam spots gets changed when the number of phase folds increases, and the initial modulation phase only impacts the angle of the beam spots. Moreover, a large distribution factor correlates to a hollow Gaussian vortex shape and weakens the splitting and gathering trend. By changing the initial parameters of the vortex modulation and the distribution factor, the peak intensity is greatly affected. In addition, the energy flow and the angular momentum are elucidated with the beam evolution features being confirmed.

Reflective ghost imaging free from vibrating detectors

The vibration is one of the important factors affecting imaging quality of conventional remote sensing imaging because the relative motion between the imaging system and the target can result in the degradation of imaging quality. The influence of the vibration of the detector in the test path on reflective ghost imaging (RGI) is investigated theoretically and experimentally. We analyze the effects of the vibrating amplitude and velocity. The results demonstrate that the microvibrations of the bucket detector have almost no impact on the imaging resolution and signal-to-noise ratio (SNR) of RGI, i.e., the degradation of imaging quality caused by the vibration of the detector can be overcome to some extent. Our results can be helpful for remote sensing imaging.

Negative influence of detector noise on ghost imaging based on the photon counting technique at low light levels

The influence of detector noise on ghost imaging (GI) is investigated at low light levels. Based on the characteristics of the additive detector noise, we establish the analytical model and display the ghost images through numerical and experimental demonstrations. It is shown that the contrast-to-noise ratio and visibility of reconstructed images are sharply affected by the detector noise. Following the increase of the ratio of average signal intensity to the average noise, the quality of reconstructions is enhanced. To reduce the measurement numbers and, thus, shorten the consuming time without sacrificing the imaging quality, we propose a sorting technique in the traditional GI algorithm for a high quality image reconstruction. The results demonstrated here will be favorable to the applications of low-light-level imaging.