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2.5 Designs for Related Problems of an ESEC LD 67

Ridged
Waveguide

LD Facet
Fig. 2.44. SEM photograph of LD facet after 10,000 contact start/stop (CSS)cycles
in an office environment (class 350,000). The disk has an SiN/SbTeGe/SiN/plastic
substrate structure and is used at low rotation of 900 rpm
still good after more than 50,000 cycles in a class 30,000 environment (30,000
particles larger than 0.5 µm/ft −3 ).
The main factors contributingto the high reliability of the head/medium
interface are the oxidation-free InGaAsP LD–PD, the high thermal conduc-
tivity of the slider, and the low residual stress and high adhesion strength
of the SiN protective layer on the recordingmedium. Moreover, as the LD
facet is about 1 µm behind the slider surface, it does not directly contact the
medium.
The small optical head with only an LD–PD on a slider shows ex-
cellent read/write characteristics and reliability. An antireflection-coated
LD combined with a taper-ridged waveguide has a high-SNR readout and
high-resolution write-down performance. An oxidation-free InGaAsP LD
(λ =1.3 µm), a high thermal conductivity AlN slider, and a SiN pro-
tective layer (0.24 µm) on a phase change recording medium contribute
to the high reliability of this flying optical head. Some kind of cartridge
mechanism or dust-wipingmethod should be developed to allow removal
and replacement of the recordingmedium. For high-performance use,
a high-speed track following method and a multibeam head should be
developed.

2.5 Designs for Related Problems of an ESEC LD
2.5.1 Enlargement of a Photothermal MC Deflection
for a Tunable LD
A photothermally driven MC tunable LD that needs no electrode to apply
voltage has been proposed. The advantages of the optical method in such in-
tegrated systems are that it is controlled remotely and not affected by electro-
magnetic interference; these factors are especially critical for highly integrated
devices.