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212 5 Near Field

80 50
Reflectivity V 1 , V 2 (%) 80 V 1 2 80 50
100
10

V
10

60 Duty (%)
50 100 200 300 400 500 600 700 800 900 1000 2000 3000
Mark length (nm)
Fig. 5.59. Relationships between reflectivity V 1 (non-mark), V 2 (mark), and mark
length for super-RENS readout (P r = 4 mW), with optical pulse duty as parameter

50
Duty (%) 30 40
40
20
CNR (dB) 30 10 50
20
10 80
0
50 100 200 300 400 500 600 700 800 900 1,000 2,000 3,000
Mark length (nm)
Fig. 5.60. Relationship between CNR and mark length for super-RENS readout
(P r = 4 mW), with optical pulse duty as parameter
mark length becomes shorter as the optical pulse duty ratio decreases, and
reaches 50 nm (CNR = 17 dB) at the duty ratio of 10%.
In summary, the scattered-type super-RENS usingZnSiO 2 /AgO /ZnSiO 2 /
x
GeSbTe/ZnSiO 2 has the followingcharacteristics:
1. The mask layer and the recordinglayer have five possible states depending
on the write power P w : as-depo, Agparticles uniformly dispersed and crys-
tallized (after initialization), Agcluster and half amorphous, Agdiffusion
and completely amorphous, and Agringand bubble pit.
2. The mask layer for the super-RENS readout has an Agringstructure,
and the aperture is filled with O 2 , which increases both the CNR and the
resolution limit.
3. The smallest mark length of 50 nm is reproduced at 17 dB by decreasing
the optical pulse duty ratio of 10% under the experimental condition of
λ/4NA = 413 nm.

Problems

5.1. How is the force F =2kT/d (due to Brownian motion) dependence on
the diameter d of a microsphere? The microsphere is suspended in water,
where k is the Boltzman constant, and T is 298 K.