close

Вход

Забыли?

вход по аккаунту

?

el%3A19930094

код для вставкиСкачать
loops at 20-60"C, which was much shorter than the delay
from compressive-strained QW lasers (175 ps at 70°C) [SI.
.
E.20 -
... %"!
C
:
210 -
2
.I
In summary, we achieved 1 Gbit/s, zero-bias modulation
with wide phase margins over a 20-100°C temperature range.
0
A
E
A
A
R 8
A
a
60
,
501
0
0
40
20
60
80
100
20
120
heatsink temperature,*C
a
2400
1
I
I
LO
60
80
1.00
heatsink temperature, C
1
120
Fig. 4 Phase marginsfor I n , nsCu, bsA.s Q W laser under I Gbirjs zerobias modulation
Dnve current IS 40mA, x = 0-35, 1.1ym SCH, I , = 40mA, 1 Gblt/
s, NRZ, BER = 10-9
-
The extremely short lasing delay suggests that the tensilestrained Q W laser is a promising candidate for light sources
in high-speed optical interconnection.
1
.
2300m
*
C
;2 0 0 '00-
.
o
=
2
8
A
o
0
n
A c k n o w l e d g m e n t : We thank T. Inoue, T. Machida, T. Abe and
S . Ide for their contribution to device fabrication, T. Yamamoto, S . Yamazaki and T. Horimatsu for their helpful discussions, and H. Imai for his continuous encouragement.
A
a
20th November 1992
0-
H. Nobuhara, K. Nakajima, K. Tanaka, T. Odagawa, T. Fujii and K.
Wakao (Optical Devices Laboratory, Optical Interconnection Division,
Fujitsu Laboratories Ltd., 10-1 Morinosato- Wakamiya, Atsuyi 243-01,
Japan)
b
Fig. 2 Threshold current dependence on temperature and lasing delay
dependence on temperature
a Threshold current dependence
x = 0.40,1.2 pm SCH
A x = 0.35, 1.1 pm SCH
0 x = 0.30, 1.2 prn SCH
0 x = 0-30, 1 1 prn SCH
b Lasing delay dependence
I , = 40mA
A x = 0.35,1 - 1 ym SCH
0 x = 0.30, 12pm SCH
0 x = 0.30, 1.1 pm SCH
Fig. 3 shows the eye patterns for an In, 35Ga,,5As Q W
laser under zero-bias modulation with a 215 - 1 pseudorandom bit stream. The modulation rate was 1 Gbit/s. With a
40mA drive current, the lasing wavelength was 1.51pm and
light output peak power was -1'5mW. Wide eye openings
were obtained, even at 100°C. Fig. 4 shows phase margins
measured at bit error rate of lo-' under zero-bias modulation
of 1 Gbit/s. The threshold for determining whether the signal
is 0 or 1 was set at the centre level of eye openings. Phase
margins wider than 62% (620ps for 1 Gbit/s) were obtained
over a 20-IO0"C temperature range. T o our knowledge, these
phase margins are the best to date.
References
and VAN DONGEN, I.:
'Improved performance 1.5 Nm wavelength tensile and compressively strained InCaAs-InCaAsP quantum well lasers'. Tech. Dig.
of ECOC/IOOC '91, Paris, 1991, pp. 31-38
2 YAMAMOTO, I.,NOBUHARA, H., SUGAWARA, M., FUJII, I., and WAKAO.
K.: 'Low threshold operation of tensile strained InCaAs/InGaAsP
quantum well lasers with simple separate-confinement heterostructures'. Devices and Materials, Tukuba, Japan, August 1992,
B-6-2, pp. 607-609
3 ODAGAWA, I., NAKAJIMA, K., TANAKA, K., INOUE, T., OKAZAKI, N., and
WAKAO, K
'High-speed operation of strained InCaAs/lnGaAsP
MQW lasers'. Conf. Dig. 13th IEEE Int. Semiconductor Laser
Conf., Takamatsu, Japan, September 1992, H-3, pp. 170- I71
1
lHIJS, P. J. A., BINSMA, J . J., TIEMEIJFR, L. F.,
'
ERBIUM-DOPED PHOSPHOSILICATE GLASS
WAVEGUIDE AMPLIFIER FABRICATED BY
PECVD
K. S h u t o , K. Hattori, T. K i t a g a w a , Y. Ohmori a n d
M. H o r i g u c h i
Indexing terms: Integrated optics, Optical waveguides. Amplifiers
I
I
I
1
i -
t
f
An Er-doped waveguide amplifier fabricated by plasma
enhanced chemical vapour deposition is described. A
maximum net gain of 5dB and a gain coefficient of 0.67dB/
cm are obtained in a 0.48 wt% Er-doped waveguide pumped
at 420mW at a wavelength of 0.98prn. The 0dB gain threshold is 23 mW.
i---T--
I
i
I
'
200ps/ dlvision
/076111
Fig. 3 Eye-patterns for In, ,sCao 6 5 A QW
~ laser under I Gbltls zerobias modulation at I W C
Dnve current IS 40mA
ELECTRONICS LETTERS 21st January 1993
Vol. 29
No. 2
Er-doped waveguide amplifiers are very attractive in optical
communication systems for the amplification of signals at
wavelengths around I.5pm. They are fabricated by several
139
kinds of fabrication technique [l-51. It is, however, necessary
to improve their performance in order to apply them to singlemode circuits and to increase their gain. It is feasible to use
the plasma enhanced chemical vapour deposition (PECVD)
technique for these purposes because it is essentially a thin
film technique and employs a nonequilibrium deposition
mechanism for high phosphorus doping. We propose the
application of PECVD to Er-doped waveguide fabrication
and report the first demonstration of optical amplification in a
PECVD fabricated Er-doped waveguide.
The Er-doped waveguide has a core of Er-doped phosphosilicate glass formed by PECVD, which is clad with silica
glass formed by flame hydrolysis deposition (FHD) on an Si
substrate. The core layer was deposited on the F H D undercladding layer at a substrate temperature of 400'C with conventional PECVD equipment using SiH, and N,O gases. P
alkoxide and Er chelate [SI. The P and Er doping were controlled by carefully transporting the vapour of the heated
sources into the plasma region with N, carrier gas. The core
layer was annealed at a higher temperature for densification
after deposition. Channels were formed in the core layer by
reactive ion etching and then embedded with an F H D overcladding layer. The buried waveguide had a refractive index
difference of 1.6% between the core and the cladding which
corresponds to high phosphorus doping. The Er concentration was 0.48wt"h. The Er concentration is determined by
tradeoffs between the linear gain increase with concentration
and the decrease caused by quenching [l]. The waveguide is
7.5 cm long and has a spot size of 8 x 1 1 pm2 at a wavelength
of 1.55 pm.
First we measured the propagation loss in the waveguide.
The propagation loss was low at 0.17dB/cm around the
1.3pm wavelength, where the loss is not influenced by Er
absorption. Fig. 1 shows the propagation loss spectrum of the
waveguide in the 1.5 pm wavelength region. It has an absorption peak of l.OdB/cm at 1.533~111in addition to the loss
mentioned above.
gain is almost saturated and a gain coefficient of 0.67 dB/cm is
obtained. The OdB gain threshold is 23mW. The waveguide
has almost the same gain coefficient and threshold as an Erdoped silica based waveguide [2].
1450
1500
1550
wavelength, n m
1600
1650
Fig. 2 Fluorescence spectrum o f erbium-doped pkospkosilicate glass
n,aveguide
Pump Wavelength: 0.98 pm
0
5C
100 150 200
25C
30C 350 AOC A50
pump p o w e r , m W
Fig. 3 Net gain at signal Wavelength in 7.5cm long erbium-doped phospkosilicare glass waveguide asfunction of pump power
Pump wavelength:0.98pm, signal wavelength: I.533pm
0 01
:LOG
I
1650
1500
1550
wavelength, nm
1600
I650
pjFq
Fig. I Propagation loss spectrum of 7 5 c m long erbium-doped phosphosilicate glass waveguide
The fluorescence spectrum of the waveguide is shown in
Fig. 2. For the measurement, the waveguide was pumped with
a Ti : sapphire laser at a wavelength of 0.98pm. The fluorescence peak is at 1.533pm.
A gain study was performed using the same laser pump
source at 0.98pm wavelength. The pump light and a 1.533pm
signal light provided by a tunable laser diode were coupled
together in a fibre coupler and launched into the Er-doped
waveguide via a singlemode optical fibre. The output signal
light from the waveguide was collected with a multimode fibre
and was guided into an optical spectrometer through a
dichroic mirror to remove residual pump light.
The signal intensity at the output of the waveguide is
plotted in Fig. 3 as a function of the pump power. The light
output changes from a loss of 9 d B at aero pump power to a
net gain of 5 d B at a pump power of 420mW. At 420mW the
140
In conclusion, we have demonstrated the first amplification
in a 7.5 cm Er-doped phosphosilicate glass waveguide fabricated by PECVD. The waveguide has a low propagation loss
of 0.17 dB/cm. A maximum net gain of 5 dB and a gain coefficient of 0.67dB/cm are obtained in a 0.48wtY0 Er-doped
waveguide pumped at 420mW at a wavelength of 0.98 pm. The
OdB gain threshold is 23mW. The waveguide has almost the
same gain coeflicient and threshold as an Er-doped silicabased waveguide [2]. These results show that the PECVD
technique is applicable to the fabrication of Er-doped waveguide amplifiers and also has the potential to enable a singlemode circuit to be realised [7] and to improve gain, because
the technique has superior thin film thickness controllability
and high phosphorus doping ability.
A c k n o w l e d g m e n t : The authors would like to thank K. Onose,
M. Yasu and Y. Hibino for their help in waveguide fabrication. They are also grateful to T. Izawa and M. Nakahara for
their encouragement.
20th November 1992
K. Shuto, K. Hatton, T. Kltagawa, Y. Ohmori and M. Horiguchi
( N T T Opto-Electronlcc Laboratories, Tokai-Mura, Ibaraki-Ken,
3/9-11,Japan)
ELECTRONICS LETTERS Zlst January 7993 Vol. 29 N o . 2
section of the investigated D F B laser by a taper. The emitted
light of the laser diode was directed into a 3 d B coupler via a
KITAGAWA, I., HATTORI, K., SHUTO, K., YASU, M., KOHAYASHI, M., and
HORIGUCHI,
M.:‘Amplification in erblum-doped silica-based planar
ZS-DFB-LD
lightwave circuits’. Optical Amplifiers and Their Applications
po1arisation controller
1 I
Tech. Dig., Santa Fe, 1992, PD-1
3dBcoupler
KITAGAWA, T., HATTORI, K., SHUTO, K., YASU, M., KOBAYASHI, M., and
HORIGUCHI, M.: ‘Amplification in erbium-doped silica-based planar
5
lightwave circuits’, Electron. Lett., 1992, 28, pp. 1818-1819
SHYULOVICH, J., WONG, A., WONG, W. H., BECKEK, P. C., BRUCE, A. I.,
and ADAR, R . : ‘Er3+ glass waveguide amplifier at 1 5pm on
O S C I lloscope
@detector
silicon’, Electron. Lett., 1992, 28, pp. 1181-1182
m
FEUCHTER, T., MWARANIA, E K., WANG,
I., REEKIE,
L., and WILKINSON,
J. s.: ‘Erbium-doped ion-exchanged waveguide lasers in BK-7
glass’, IEEE Photonics Technol. Letr., 1992,4, pp. 542-544
POL.\LAN, A., JACOBSON, D. C., EAGLESHAM, U. I., KISTLER, R. C., and
PCATE, J. M.:‘Optical doping of waveguide materials by MeV Er
implantation’,J. Appl. Phys., 1991,70, pp. 3778-3784
Fig. 1 Schematic diagram of experimental setup
TUMMINELLI, R., HAKIMI, F., and HAAVISTO, J:
‘Integrated-optlc
ZS-DFB-LD: two-section DFB laser diode, LD: DFB laser diode,
Nd : glass laser fabricated by flame hydrolysis deposition using
OSA: optical spectrum analyser, ESA: electrical RF-spectrum
chelates’, Opt. Lett., 1991, 16, pp. 1098-1 100
analyser
KITAGAWA, T., HATTORI, K., HIBINV, Y., OHMORI, Y., and HORIGUCHI,
M.: ‘Laser oscillation in Er-doped silica-based planar ring resonSELFOC lens-isolator-SELFOC lens combination and simulator’. Proc. ECOC ’92,1992,pp. 907-910
taneously detected by both an optical spectrum analyser
(OSA) and a fast InGaAs PINFET detector, whose electrical
signal was further measured by an electrical R F spectrum
analyser (ESA) and a digital sampling oscilloscope.
References
‘
Results: Fig. 2a shows the R F spectrum of the selfpulsating
laser at currents I , = 137mA, I , = 48mA and a temperature
of 25°C. The fundamental frequency of selfpulsation at
506MHz and its higher harmonics can be clearly seen. The
full width at half maximum (FWHM) of the fundamental
CLOCK RECOVERY BASED O N A NEW
TYPE OF SELFPULSATION I N A 1.5pm
TWO-SECTION InGaAsP-lnP DFB LASER
D. J. As, R. Eggemann, U. Feiste, M. Mohrle,
E. P a t z a k a n d K. Weich
lnderiny terms: Clock recovery, Semiconductor lasers, Lasers
Clock extraction from an optically or electrically injected
Zz3- 1 PRBS RZ data signal in a two-section ridge waveguide DFB laser with a new type of selfpulsation is demonstrated between 0 4 and 0-7GHz. A locking range of 50 MHz
is measured.
I n t r o d u c t i o n : The optical and electrical locking of selfpulsat-
ing laser diodes to an injected data signal is one of the key
factors in all-optical clock recovery. Jinno et al. [I] demonstrated optical clock extraction at 200MHz based on a selfpulsating three-section D F B laser. Barnsley et al. [2] showed
the same for selectively doped two-section Fabry-Perot (FP)
lasers covering frequencies from 0.8 to 5.2GHz. In both cases
one section of the laser was operated as a saturable absorber.
Recently we demonstrated selfpulsation in InGaAsP/InP twosection D F B lasers with both sections having gain [3]. This
new type of selfpulsation has two advantages: first, selfpulsation frequencies between several hundreds of megahertz and
more than 2 0 G H z [4] are observed, and secondly no selective
doping is required to achieve fast recombination in the
absorber section. In this Letter we demonstrate all-optical
clock extraction o n our devices with this type of selfpulsation.
As a first step the optical and electrical locking behaviour is
investigated for the frequency range 0.4-0.7 GHz.
E x p e r i m e n t . A two-electrode D F B laser of ridge waveguide
type with first order grating was prepared for the experiment.
Details of the preparation are described in Reference 3. Both
facets were uncoated and the section lengths were 300 and
70 pm, respectively. The selfpulsation frequency of the device
could continuously be tuned from 400 to 800MHz by either
increasing the different section currents I, (longer section) or
I , (shorter section) or by decreasing the temperature. During
selfpulsation the laser emitted light at 1530nm.
The experimental setup is shown schematically in Fig. 1.
Optical injection was provided by an externally modulated
D F B laser module with an emission wavelength of 1535x1111.
For modulation, a 223 1 PRBS RZ data signal with bit
rates up to 700 Mbit/s was supplied by a pulse pattern generator. 100pW of optical power was coupled into the shorter
0 010
1455
2 890
frequency. GHz
a
-46
Y
-60
~
-
ELECTRONICS LETTERS
21st Januarv 1993 Vol. 29
No. 2
141
Документ
Категория
Без категории
Просмотров
0
Размер файла
251 Кб
Теги
3a19930094
1/--страниц
Пожаловаться на содержимое документа