thicknesses of 80, 60, 40, and 20 nm, respectively. Within each step the
energy is further linearly graded. The etch stop layer in the p-cap layer in
20 nm thick 150 nm above the SCH region. The p-InP cap layer is linearly
graded doped from a concentration of
2
×
10
17
cm
−
3
to
9
×
10
17
cm
−
3
within 500 nm. The characteristics of the developed SLD are shown in
Table 3
Тable 3
Characteristics of the developed SLD
Parameter
Measured result
Internal quantum efficiency
η
i
= 93%
Internal optical absorption at threshold
α
i
= 11
cm
−
1
Characteristic temperature
(20
−
60
◦
C)
T
0
= 58
.
2
K
In order to suppress the spectrum modulation, facet reflectance must be
minimized. We have designed the SLD, which is composed of a
J
-shape
waveguide with 2-
μ
m ridge and a tapered rear absorption region. The
curvature of the waveguide suppresses the Fabre-Perot (FP) mode so that
the device has only a single-pass amplified spontaneous emission (ASE).
The tapered part is used to enhance the ASE, which has an open angle of
5
◦
. The whole cavity is tilted against the facet with an angle of
8
◦
.
The structure is etched to a depth of
1
.
4
μ
m. The side wall of the
ridge and the surface of the absorption area are coated with 200 nm
SiO
2
deposited by electron-cyclotron plasma-enhanced chemical vaper
deposition (ECP-PECVD). The ridge part of the SLD is 1.4 mm long and
the whole absorption section is 1.5 mm long. After cleavage, the front facet
of the SLD is coated with one layer of SiN
X
as the anti-reflection film
deposited by ECP-PECVD.
Characteristics of the developed SLD chip are shown in Table 4.
Тable 4
Characteristics of the developed SLD chip
Parameter
Test result
Output power at 400mA and
20
◦
C
25mW
Full-width at half-maximum (FWHM)
26–28 nm
Fluctuation on the spectrum (Ripple)
0.2 dB
Experimental investigation.
The setup in closed loop operation is
different from the conventional IFOG. In order to avoid the overlap of the
signals with different numbers of round-trips, a pulsed phase modulation
112 ISSN 0236-3933. Вестник МГТУ им. Н.Э. Баумана. Сер. “Приборостроение”. 2005. № 4
