A rapid and efficient procedure for deprotection of 1,1-diacetates catalysed by silica sulfate

Article abstract of DOI:10.1109/ISDRS.2005.1596174

An efficient procedure for converting a number of 1,1-diacetates into the corresponding aldehydes was developed with silica sulfate as catalyst. The advantages of this procedure is its brevity, and high yield. It is environmentally friendly and the catalyst is also inexpensive and reusable.

Full text of DOI:10.1109/ISDRS.2005.1596174

INJECTION-LOCKING IN FABRY-PEROT QUANTUM-WELL LASERS
X. Jin and S. L. Chuang
Optoelectronic devices and fiber optic communication have revolutionized the Internet, long-
distance phone calls, and cable TV for the past few years. The massive amounts of data
transmission require large amounts of bandwidth, achievable through high-speed modulation of
the laser sources. In this study, we report experiment results and theoretical calculations of dc and
small-signal modulation of a side-mode injection-locked Fabry-Perot (FP) laser.
We first measure the lasing spectra of the master laser and the injection-locked quantum-well
test laser. The master laser is a tunable laser source emitting at 1557.45 nm, which is close to the
fifth side-mode on the longer wavelength side of the lasing mode of the test laser. In Fig. 1, the
dashed line shows the laser emission spectrum of the test laser with the main peak wavelength at
1
551.2 nm. This is a typical FP laser spectrum, and the side-mode suppression ratio (SMSR) of
the laser is around 20 dB. When the external master laser light is injected into the test laser
biased above threshold, the injected light competes with the spontaneous emission of the laser for
amplification. When the external light is strong enough and close to the eigen-frequency of the
test laser, it is amplified since there is gain available. At the same time it saturates the gain of the
other modes and extinguishes all the other free-running modes. Once a perfect locking state is
reached, all of the power of the test laser is emitted at the optical frequency of the master laser, as
shown by the solid line in Fig. 1. Injection locking greatly improves the SMSR of the test laser
and shifts the lasing wavelength from 1551.2 nm to 1557.45 nm. This side-mode injection
locking of a FP laser has the advantage of mode selection over that of a single-mode DFB laser.
This intermodal injection locking can switch the information from the free-running mode to any
side mode as long as the injection-locking condition is satisfied, and can be used for optical
wavelength conversion in wavelength division multiplexing (WDM) channel selection [1][2].
-1
-2
-3
-4
-5
-6
-7
-8
-9
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
No injection
3.96 mW injection power
Itest =25 mA
1545
1550
1555
1560
1565
1570
Wavelength (nm)
Fig. 1 Measured optical spectrum of the test laser without injection (dashed line) and with
injection (solid line) at 25 mA bias.
20
Unlocked range
10
0.0
Locked range
-
-
-
-
10
20
30
40
Unlocked range
0
0.5
1
1.5
2
2.5
3
1
/2
Square root of minimum injection power (mW)
Fig. 2 Locking range dependence on both injected power and detuning for a fixed test laser bias
o
of 30 mA at 25 C.
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-4244-0084-8/05/$20.00/©2005 IEEE

We also measure the overall locking range of a FP semiconductor laser, which is determined
by both frequency detuning and the external injection power at a fixed test laser bias, shown in
Fig. 2. By fitting the data, we obtain the linewidth enhancement factor of the test laser is 1.8,
which is in agreement with a measurement using an independent method based on amplified
spontaneous emission spectroscopy [3]. We will use this value in our theoretical calculation of
the modulation response.
The small-signal amplitude-modulation response of the injection-locked test signal is
measured when a dc master laser signal is injected into the test laser biased above the threshold
with small-signal modulation. Fig. 3 shows the modulation response of the injection-locked test
laser under a constant test laser bias I=30 mA at different injection powers. We show the
improvement of 3 dB modulation bandwidth of an injection-locked FP laser, which is twice of its
free-running value. The relaxation frequency is 3.5 times of its free-running value. The injected
signal reduces more unwanted fluctuations and feedback, more stimulated emission than random
spontaneous emission occurs, and enhances the peaks. For injection locking laser system, the
photon density of the slave laser is coupled in phase, which enhances the bandwidth. Our
theoretical model also requires setup coupling between the photon density and its phase terms.
This important characteristic of injection-locked semiconductor lasers is called amplitude and
phase coupling. We also point out that the small-signal modulation of injection-locked lasers still
suffers low frequency roll-off, which comes from the carrier transport effect and parasitic effect
of the bias circuit. This phenomenon is also shown in the data of distributed feedback (DFB) laser
provided by Ref. [4]. Finally, we improve the existing small-signal model for injection locking by
adding the optical confinement factor of separate-confinement-heterostructure (SCH) QW lasers,
nonlinear gain saturation of the slave laser due to the master laser, and low frequency roll-off due
to carrier transport and parasitic effects. Our model includes all relevant phenomena, either
observed experimentally or predicted theoretically and shows good agreement with our
experimental results.
1
0
1
0
5
0
5
1
4
-3
Injection locking (Exper im ent)
No injection
Injection locking (Theory)
S
i
(x10 cm )=
0
0
.34 mW
.65 mW
5
0
(
No injection)
.005
0
1
1
.32 mW
.98 mW
0
0.2
1
2
2
.79 mW
-
-5
3.5
-
-
-
10
15
20
-10
Itest=30 mA
14
-3
-15 S0=6.2x10 cm
-20
0
3
6
9
12
15
18
0
3
6
9
12
15
18
Frequency (GHz)
b)
Frequency (GHz)
a)
(
(
Fig. 3 Experiment data (a) Theoretical calculation (b) of the small-signal modulation response of
an injection-locked test laser.
REFERENCES
[
1] Y. Hong and K. A. Shore, ``Locking characteristics of a side-mode injected semiconductor
laser," IEEE J. Quantum Electron., vol. 35, pp. 1713-1717, 1999.
2] J. Horer and E. Patzak, ``Large-signal analysis of all-optical wavelength conversion using
two-mode injection-locking in semiconductor lasers," IEEE J. Quantum Electron., vol. 33, pp.
96-608, 1997.
3] T. Keating, S. H. Park, J. Minch, and S. L. Chuang, ``Optimal refractive index changes for
cross-gain and cross-phase modulation," Proc. SPIE, vol. 3283, pp. 314-322, 1998.
4] X. J. Meng, T. Chau, and M. C. Wu, ``Experimental demonstration of modulation bandwidth
[
5
[
[
enhancement in distributed feedback lasers with external light injection," Electron. Lett., vol. 34,
pp. 2031-2032,1998.