Diffraction efficiency

About: Diffraction efficiency is a research topic. Over the lifetime, 10320 publications have been published within this topic receiving 158298 citations.

Diffraction of digital micromirror device gratings and its effect on properties of tunable fiber lasers

Abstract: A digital micromirror device (DMD) is a kind of widely used spatial light modulator. We apply DMD as wavelength selector in tunable fiber lasers. Based on the two-dimensional diffraction theory, the diffraction of DMD and its effect on properties of fiber laser parameters are analyzed in detail. The theoretical results show that the diffraction efficiency is strongly dependent upon the angle of incident light and the pixel spacing of DMD. Compared with the other models of DMDs, the 0.55 in. DMD grating is an approximate blazed state in our configuration, which makes most of the diffracted radiation concentrated into one order. It is therefore a better choice to improve the stability and reliability of tunable fiber laser systems.

Gas phase dynamics and spectroscopy probed with picosecond transient grating experiments

Abstract: Picosecond transient grating experiments in sodium and iodine vapors, involving the 3S→3P and X→B transitions, respectively, are discussed in detail. Population gratings in sodium demonstrate that the technique can be used to measurevelocity distributions in the gas phase. It is shown that the time dependent transient grating signal is related to the Fourier transform of the velocity distribution. Similar experiments on iodine illustrate the effect of state changing collisions on the grating signal. Theoretical calculations for a model in which the change of state is caused by a single collision are given. Close agreement with the data is observed for the situation in which the collision takes the initial velocity into a random velocity distribution. From this model a collision cross section is determined. The results demonstrate that information on collision dynamics can be obtained from grating experiments. In addition, the sodium experiments are used to illustrate a new type of time domain high resolution spectroscopy. When the grating excitation pulses have perpendicular polarizations, a polarizationgrating, rather than the usual population grating, is formed. Diffraction from the sodiumpolarizationgrating shows larger time dependent oscillations in the diffraction efficiency. These oscillations yield the ground state and excited state hyperfine frequencies (1.77 GHz and 189 MHz, respectively). A detailed theoretical description of the origin of the oscillations is presented. The results suggest that polarizationgratingspectroscopy can have applications in other areas, such as molecular rotational dynamics.

Surface-relief and polarization gratings for solar concentrators.

Abstract: Transmission gratings that combine a large diffraction angle with a high diffraction efficiency and a low angular and wavelength dispersion could be used to collect sunlight in a light guide. In this paper we compare the diffractive properties of polarization gratings and classical surface-relief gratings and explore their possible use in solar concentrators. It is found that polarization gratings and surface-relief gratings have qualitatively comparable diffraction characteristics when their thickness parameters are within the same regime. Relatively large grating periods result in high diffraction efficiencies over a wide range of incident angles. For small grating periods the efficiency and the angular acceptance are decreased. Surface-relief gratings are preferred over polarization gratings as in-couplers for solar concentrators.

Coupled mode analysis of polarization volume hologram

Abstract: We theoretically analyze polarization holographic recording based on photoinduced dichroism and birefringence. Such vectorial recording is achieved by preferentially transforming dye molecules aligned with the incident polarization in dynamic photoanisotropic organic materials. Orthogonal linear and orthogonal circular recording geometries, which produce only pure polarization modulations, are considered. The analytic solutions of the intensity and phase of the recording beams at steady state are derived. The theoretical results indicate the dependence of diffraction efficiency on the photoinduced dichroism and birefringence and on the polarization state of the probe beam. Results of numerical simulation are provided and compared with the analytic solutions. >

Analysis of propagation at the second-order Bragg angle of a thick holographic grating*

Abstract: Algebraic expressions are derived for the diffraction efficiency of the first and second orders of a holographic grating recorded in a thick, pure-phase material with a nonlinear exposure response for readout at the second-order Bragg angle. The results demonstrate the importance of double diffraction by the fundamental grating as well as diffraction by the harmonic grating in producing the second order. It is shown that the strong cross coupling between two gratings constructed in the same emulsion with a common construction angle is a limiting case of the double diffraction that occurs in single gratings. Experimental results from gratings constructed in dichromated gelatin are presented to verify the theory.