Page 484 - Introduction to Information Optics

Exercises 469

8.10 (a) A photorefractive crystal modulates the phase of light due to its local
refractive index. Is the local refractive index proportional to the
intensity, amplitude, phase, or polarization of the exposing light?
(b) Does the recording process in a photorefractive crystal involve
developing and fixing steps such as that in a photographic plate?
8.11 A pattern A is recorded into a photochromic material using A,, and then
read out using A 2. Show that the output pattern at / 2 is (1 — A).
8.12 A pattern A is first recorded into an ET material using blue light
(x l = 488 nm). When a pattern B is projected into the ET material using
infrared light (A 2 = 1064 nm), the ET material emits orange-color light
(A 3 — 615 nm) with a pattern C. What is C in terms of A and B?
8.13 (a) An ET material is first exposed to uniform illumination of / n = 488
nm, then to a pattern A of A 2 = 1064 nm, and finally to a pattern B
of/ 2 = 1064 nm, to produce an emission of pattern C at / 3 = 615 nm.
What is C in terms of A and B?
(b) An ET material is first exposed to uniform illumination of /, t = 488
nm, then to patterns A and B successively at the same wavelength
/., = 1064 nm, and finally to uniform illumination of /1 2 = 1064 nm,
to produce an emission of pattern C at / 3 = 615 nm. What is C in
terms of A and B!
8.14 Explain why a two-photon-absorption material can be read without
erasure while the readout of an ET material will erase the stored
information.
8.15 Which of the following statements is correct?
(a) Bacteriorhodopsin emits light at 570 nm upon light stimulation at
412 nm.
(b) Bacteriorhodopsin modulates the amplitude of light passing through
it.
(c) Bacteriorhodopsin modulates the phase of light passing through it.
(d) Bacteriorhodopsin modulates the frequency of light passing through
it.
8.16 After bleaching out, spectral hole-burning material can be read at the
beached-out band Aj. Is the readout at A± erasing the stored information?
8.17 (a) Do we need polarized light for writing information into magneto-
optic material? Explain why or why not.
(b) Do we need polarized light for reading out the stored information
from magneto-optic material? Explain why or why not.
8.18 Does phase-change material modulate the intensity, phase, or polariz-
ation of the readout light?
8.19 The following figure shows the basic pickup optics for a CD system (LD:
laser diode; PBS: polarizing beam splitter; /L/4: quarter-wave plate).
Assuming that the laser emits linearly polarized light, show that in
principle, we can collect the reflected light 100%.