ETC SLD1236VL

High-Power Red Laser Diode Supports ×16-Speed DVD Recording
SLD1236VL
The DVD recording market is developing rapidly.
Following the ×4, ×8, and ×12 speeds, high-speed recording has already evolved to the ×16-speed level.
To respond to this market trend, Sony has now developed the
SLD1236VL 250 mW optical power output laser diode that supports
×16-speed DVD recording.
■
Maximum optical power output :
250 mW (in pulse drive mode)
■
High-temperature (75°C) operation
guaranteed
■
New user-friendly actual refracting
waveguide window structure
In addition to the optical power output being increased by 50 mW over
earlier products, the SLD1236VL also achieves guaranteed operation
under the severe environmental conditions of temperatures up to 75°C.
Maximum Optical Power Output:
250 mW (in pulse drive mode)
Increasing the recording speed in
DVD+R/RW and DVD-R/RW requires
that the optical power output of the laser
diode used as the light source be
increased. This is because the material
characteristics of the recording medium
must be changed in a period of time that
becomes shorter as the recording speed is
increased. Sony has already released
laser diodes with optical power output levels of 100, 140, and 200 mW to support
recording speeds of ×4, ×8, and ×12. The
SLD1236VL of this release achieves an
even higher optical power output, and can
be driven at an optical power output of
250 mW, which supports ×16-speed
recording.
V
O
I
C
Despite this being a difficult device
to design, we only had a short
development period and the road
to commercial release was perilous. However, thanks to much
assistance from the staff and our
cohesion as a group, we succeed
in making it safely to commercial
release. Our next step is to proceed
with development aimed at even
higher output to support two-layer
discs.
E
High-Temperature (75°C)
Operation Guaranteed
When recording at speeds as high as ×16,
the heat released by the various system
components increases due to the spindle
motor that turns the disc running faster,
the laser diode power being increased, and
other changes. As a result, the ambient
temperature inside the case increases. This
there is demand for laser diodes whose
operation is guaranteed at temperatures as
high as 75°C. Sony introduced new structures in the areas surrounding the light
emitting regions of the newly-developed
SLD1236VL, and as a result, operation is
guaranteed under severe operating conditions up to 75°C.
User-Friendly Actual
Refracting Waveguide
Window Structure
To respond to calls for the lower aspect
ratios demanded for optical pickups, Sony
has adopted, in the previously released
SLD1234VL (pulse drive: up to 140 mW)
and SLD1235VL (pulse drive: up to 200
mW), designs that reduces the radiation
angle in the perpendicular direction (θ⊥)
at the end surface of the laser. The
SLD1236VL inherits the structure that
results in the same θ⊥ angle of 17.5
degrees (typical) achieved in the
SLD1234VL and SLD1235VL, thus creating a user friendly laser diode product.
In addition, the SLD1236VL adopts a lowloss actual refracting waveguide window
structure that improves the low threshold
current and temperature characteristics. As
a result, the SLD1236VL achieves a
threshold current of 50 mA (typical) and
current value of 130 mA (typical) in 80
mW CW drive mode. The reduction in the
threshold current also reduces the noise
levels.
■ Table 1 SLD1236VL Main Specifications
Symbol
Typ.
Threshold current
Ith
50
Operating current
Iop
130
Operating voltage
Item
Dual layer
×16-speed
recording
Output power
×12-speed
recording
×8-speed
recording
300 mW
Under development
Vop
2.5
V
λp
658
nm
Radiation Parallel
angle
Perpendicular
θ//
9.0
θ⊥
17.5
SLD1236VL
250 mW
SLD1234VL
140 mW
SLD1233VL
100 mW
2004
2005
Year
■ Figure 1 DVD Recording Laser Diode Development Trends
(1) FFP
(2) L - I Temperature Dependency
250
Pulse width = 40 ns
CW drive
Tc = 25°C
Po = 80 mW
Power [mW]
Intensity [a.u.]
200
θ⊥ = 17.5 deg.
θ// = 9.0 deg.
150
100
20°C
30°C
40°C
50°C
60°C
70°C
75°C
50
–40
–30
–20
–10
10
0
Angle [deg.]
20
30
■ Figure 2 SLD1236VL Representative Characteristics
deg.
Condition: Tc = 25°C
Po = 80 mW@CW
SLD1235VL
200 mW
2003
mA
Wavelength
×4-speed
recording
2002
Unit
40
0
0
100
200
300
Current [mA]
400
500