Fig. 3. Variation in diffraction efficiency with wavelength for different values of
depth of refractive index modulation (n1) at fixed value of = 0.51 m, n = 1.61 and
d = 7 m.
particular depth of refractive index modulations as specified in the
simulation at the time of recording of holocons.
5.2. Chromatic characteristics
When typically recorded three holocons were played back
by white light source (10 mW), three different spectrum were
obtained as shown in Fig. 5(a)–(c). Intensity distribution of different
regions of the spectrum is measured by an optical power meter
(Newport 1916-R) and shown in Fig. 6. Fig. 6 reveal that properly
recorded holocons may efficiently split up sun rays with reasonably
good diffraction efficiency over the entire useful solar spectrum.
These dispersing and focusing properties of holocons can advantageously
be utilized for concentrating different portion of visible
spectrum on solar cells of matched band gap. This scheme may
enhance the electrical efficiency of the system [32].
5.2.1. Performance analysis
On the off axial focal planes of holocons (where dispersed as
well as concentrated solar spectrum is formed) a circular aperture
of diameter 1 cm fitted with a translational stage is moved step by