Transformation of Laguerre-Gaussian beams into 1D array of Hermite-Gaussian modes under the Talbot effect.

This work explains diffraction of Laguerre-Gaussian (LG) beams having non-zero radial indices from one dimensional (1D) periodic structures and their transformation into Hermite-Gaussian (HG) modes, theoretically, verifies using simulations and demonstrates the phenomenon experimentally. We first report a general theoretical formulation for such diffraction schemes, and then use it to investigate the near-field diffraction patterns from a binary grating having a small opening ratio (OR) by providing numerous examples. Results show that for OR≲ 0.1, at the Talbot planes, mainly at the first Talbot image, the images of individual lines of the grating obtain HG modes' intensity patterns. Therefore, the topological charge (TC) of the incident beam and its radial index can be determined from the observed HG mode. In this study, the effects of the OR of the grating and the number of Talbot plane on the quality of the generated 1D array of HG modes are also investigated. The optimum beam radius for a given grating is also determined. The theoretical predictions, are well confirmed by a number of simulations based on the free space transfer function and fast Fourier transform approach, and by experiments. The observed phenomenon, the transformation of LG beams into 1D array of HG modes under the Talbot effect, in addition of providing a way for characterization of LG beams with non-zero radial indices, itself is interesting and may be used in other fields of wave physics, especially for long-wavelength waves.

Propagation of a multi-vortex beam: far-field diffraction of a Gaussian beam from a multi-fork phase grating.

In this work, the far-field propagation of multi-vortex beams is investigated. We consider diffraction of a Gaussian wave from a spatial light modulator (SLM) in which a multi-fork grating is implemented on it at the waist plane of the Gaussian wave. In the first-order diffraction pattern a multi-vortex beam is produced, and we consider its evolution under propagation when different multi-fork gratings are implemented on the SLM. We consider two different schemes for the phase singularities of the implemented grating. A topological charge (TC) equal to l1 is considered at the center of the grating, and four similar phase singularities all having a TC equal to l2=l14 (or l2=-l14) are located on the corners of a square where the l1 singularity is located on the square center. Some cases with different values of l1, and consequently l2, are investigated. Experimental and simulation results show that if signs of the TCs at the corners and center of the square are the same, the radius of the central singularity on the first-order diffracted beam increases, and it convolves the other singularities. If their signs are opposite, the total TC value equals zero, and at the far-field, the light beam distribution becomes a Gaussian beam. For determining the TCs of the resulting far-field beams, we interfere experimentally and by simulation the resulting far-field beams with a plane wave and count the forked interference fringes. All the results are consistent.

Simple, efficient and reliable characterization of Laguerre-Gaussian beams with non-zero radial indices in diffraction from an amplitude parabolic-line linear grating.

In this work, we report the characterization of a Laguerre-Gaussian (LG) beam with given values of topological charge (TC) and radial index in a simple, efficient, and robust experimental diffraction scheme. The beam diffracts from an amplitude parabolic-line linear grating and the resulting diffraction patterns at zero- and first-order reveals the values of the TC, l, and radial index p of the incident LG beam using a simple analysis. The zero-order diffraction pattern consists of p + 1 concentric intensity rings and the first-order diffraction pattern contains an (l + p + 1) by (p + 1) two-dimensional array of intensity spots. The experimental scheme is robust since it is not sensitive to the relative locations of the impinging beam axis and the grating center, and is efficient since most of the energy of the output beam is in the diffraction order of interest for LG beam characterization. The measurement is also simple since the intensity spots of the array are placed exactly over straight and parallel lines. Both experimental and simulation results are presented and are consistent with each other.

Predictors of Physician's Empathy: The Role of Spiritual Well-being, Dispositional Perspectives, and Psychological Well-being.

OBJECTIVES: Empathy is a core component of an efficient physician-patient relationship. Although students' preexisting medical views may influence responses to physician-patient relationship, there is little knowledge about the psychological predictive factors of empathic perspective for physician-patient relationship. We aimed to examine whether psychological well-being, dispositional perspective, and spiritual well-being could predict the empathic perspective of medical students regarding the physician-patient relationship. METHODS: In a cross-sectional study, 350 medical students of Babol University of Medical Sciences were recruited at four levels of education including basic sciences, preclinical medicine, clerkship, and internship. The students completed four questionnaires including Jefferson Scale of Empathy - student version, Brief Ryff psychological well-being, Individual Disposition, and Spiritual Well-Being. RESULTS: The score of medical student's perspective to clinical empathy was high (106.1±29.8, range: 20-140), but diminished with further years of education. Female students had higher empathy scores than their male counterparts. Pearson's correlation coefficient revealed a strong positive significant relationship between student's perspective to clinical empathy and spiritual well-being (r = 0.56), cognitive empathy (r = 0.51), and psychological well-being (r = 0.43), and tendency to egalitarianism (r = 0.37). The results of stepwise multivariate analysis regression revealed that cognitive empathy (ß = 0.300), self-esteem (ß = 0.133), and spiritual well-being (ß = 0.388) positively predicted student's perspective to clinical empathy regarding the physician-patient relationship. CONCLUSIONS: The results suggested that promoting empathic care in curricula of medical schools may be more effective if students' preexisting perspectives, cognitive empathy, self-esteem, spiritual well-being, and tendency to egalitarianism are taken into account.