The defocusing correction depends on the

Bragg angle th, correction curves of other materials, Copper powder for correction Cu sample can be generally corrected with the correction curves derived from a Cu powder [7,8].

As can be seen near the

Bragg angle, the three theories reproduce the same results.

After recording, when the green laser was shut off, we rotated the sample to record the angular response around the

Bragg angle and obtained the data necessary to calculate the physical and optical thickness of the holographic diffraction gratings.

The reflectance as a function of the angle is also represented, where as expected strong reflection occurs at the band edges (

Bragg angles).

Scherrer's equation, t = (K X [lambda])/([PHI] X cos([theta])), was used to determine the thickness of the crystallite in the (110) and (200) planes, where t is the thickness of crystallite, K (=0.89) is a constant that depends on crystallite shape, [lambda] = wavelength (1.54 [Angstrom]), [PHI] is the full width at half-maximum of the diffraction peak, and [theta] is the

Bragg angle (24).

This acoustically induced refractivity modulation forms a diffraction grating which, when illuminated at the

Bragg angle, deflects the optical beam through an angle proportional to the acoustic frequency.

Each grating element within the DOE should be illuminated at the

Bragg angle for that grating.

Therefore, if the interplanar distance and the

Bragg angle of the material without residual stresses are [d.sub.0] and [[theta].sub.0], respectively, and the diffraction angle of the X-rays is [phi], the strain measured on a direction (y) parallel to the specimen surface is:

X-ray diffraction (XRD) analysis was performed on a Bruker D8 diffractometer, using Cu K[alpha] radiation to determine the formation of nanocomposite structures and to determine interlayer spacing of the clay layers in the PP matrix, from the measured

Bragg angles. XRD patterns of thin compression molded sheets of PPCN were obtained by scanning over a

Bragg angle (2[theta]), ranging froml-10[degrees] at a rate of 0.01[degrees]/s.

Neutrons of each wavelength from the beamsplitter are then incident at the corresponding

Bragg angle [[theta].sub.B] to the sample and the phase

This modulation forms a quasi diffraction grating which, when illuminated at the

Bragg angle, deflects the beam through an angle proportional to the acoustic frequency.