Transcript ВКР генерация антистоксового излучения

Combined Stokes-anti-Stokes Raman
amplification in fiber
Nikolai S. Makarov
Saint-Petersburg State
Institute of Fine Mechanics
and Optics (Technical
University)
Victor G. Bespalov
All Russian Research Center
"S. I. Vavilov State Optical
Institute"
Outline
• Main goals
• Principle of quasi-phase matching
• System of SRS equations
• Properties of quasi-phase matched SRS
•Numerical simulations results for fibers
• Conclusions
• References
EDFA-amplification
- It is
necessary to
provide
amplification
with an error
no more than 
5 dB in the
whole spectral
band of the
amplifier.
SRS amplification in silica fiber
- With
pump=1480
nm, due to
the broadband
of SRSamplification
stokes=1550 1580 nm.
Combined EDFA and
Stokes SRS amplification
- Flattening of
amplification
curve is possible
with combined
using of EDFA
and Stokes SRS
amplifier.
- For improvement of amplification curve and creating of a
new channel in 1310 nm we propose to use simultaneous
Stokes and anti-Stokes SRS amplification at QPM.
Principle of quasi-phase matching
Nonlinearity (2)
Nonlinearity (3)
Raman active medium
3
Principle
of quasi-phase matching at SRS
- Generalized phase
(3)0
(3)=0
=2p-a-s-(ka+ks-2kp)r,
where ki – is the wave vector of
interacting wave, that describes
the direction of energy
conversion “pump – Stokes –
anti-Stokes”, on passive layers
input (0, 2) and active layers
input (1, 3) do not practically
change, that in a final result
provides a realization of quasiphase matching conditions.
System of steady-state SRS equations
In this system the waves mismatching
and Raman gain are the functions of
coordinate for nonlinear ((3)0) and
linear ((3)=0) layers.
 – waves
mismatching, g
– steady-state
Raman gain
coefficient, i –
frequencies of
interacting
waves, Aj –
complex wave
amplitudes.
5
Efficiency of anti-Stokes
SRS generation in Raman-active media
Hydrogen
 = 3.84 rad/cm
g = 3.0 cm/GW.
- There is an optimal ratio Is/Ip, for maximal conversion
efficiency.
- The ratio depended from waves mismatching and steadystate Raman gain coefficient.
6
Energy conversion at
quasi-phase matching
Hydrogen
 = 3.84 rad/cm
g = 3.0 cm/GW
Is(0) = 0.0023
GW/cm2
efficiency  30%
- At optimum ratio Is/Ip, conversion efficiency reached more
than 30%, but Stokes intensity is higher then anti-Stokes
intensity.
7
Comparison of
quasi-phase and phase matching
Hydrogen
 = 3.84 rad/cm
g = 3.0 cm/GW
1 - quasi-phase
matching
2 - without (quasi-)
phase matching
3 - phase matching
- Conversion efficiency at quasi-phase matching is lower than
at phase matching and higher than at simple focusing in
Raman media.
8
Lengths of active and passive zones
1,4
- Similar plot can be
1,2
1
L, cm 0,8
achieved for barium
nitrate.
H2
0,6
- Structure of layers is
0,4
0,2
0
10
20
30
40
zone, ed
Lact
50
60
not periodical.
Lpass
- Lengths of active/passive layers are monotonously
decreased/ increased.
- It is essentially different from quasi-phase matching in (2)
media.
9
Characteristic zone lengths
1
- It is possible
0,5
0
to approximate
this
dependence as
La = 2.6/ and
Lp = 3.9/.
log L, log cm -0,5
-1
-1,5
-2
0
50
100
150
delta, rad/cm
ln act
ln pass
- With increasing of waves mismatching structure become
more periodical.
10
Critical pump wave intensity
- There is a
critical value
of pump
intensity.
- This
dependence
can be
approximated
as Icr.p=0.4Δ/g
11
SRS in silica fiber
- For amplification
in both windows it is
possible to use
simultaneously
amplification of
Stokes and antiStokes radiation at
condition of quasiphase matching.
- The structure is quasi-periodic.
Simultaneously
Stokes and anti-Stokes amplification
- Stokes and
anti-Stokes
amplification
provides
amplification
peaks at
wavelengths of
1389 and 1583
nm with pump
1480 nm.
EDFA and anti-Stokes SRS amplification
- Combined
EDFA and
simultaneously
Stokes and antiStokes
amplification
provides the
amplification in
both windows.
Conclusions
• Stokes-Anti-Stokes SRS amplification is useful for
improvement of EDFA amplification curve and creating of
amplified channel in 1310 nm transparency window.
• Quasi-phase matching structure in silica fibers is quasiperiodic.
• Layers lengths do not depend on input waves intensities if
the ratio between pump/Stokes/anti-Stokes waves intensities
does not change.
• For more effective flattening of the amplification curve and
broadening of amplified channel in 1310 nm transparency
window we can use pump at several wavelengths.
References
•G. Randy, L. I. Tingyc, "Optical amplifiers transform long distance
lightvoice telecommunications", Proc. IEEE, 84, pp. 870-883, 1996.
•P. Urquhart, "Review of rare-earth-doped fiber lasers amplifiers", IEE
Proc, 6, 385-407, 1988.
•M. H. Ahmed, M. Shalaby, F. M. Misk, "Combined erbium and Raman
amplification at 1.55 m in submarine links using backward pumping at
1.48 m", Pure Appl. Opt., 7, 659-666, 1998.
•V. G. Bespalov, N. S. Makarov, "Quasi-phase matching anti-Stokes SRS
generation", Proc. SPIE, vol. 4268, 2001 (accepted for publication).
•J. J. Ottusch, M. S. Mangir, D. A. Rockwell, "Efficient anti-Stokes
Raman conversion by four-wave mixing in gases", J. Opt. Soc. Am., 8,
pp. 68-77, 1991.