Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.ipa.nw.ru/conference/wpltn2012/docs/27/1100%20Nonlinear-optical%20Approach.pdf Дата изменения: Mon Oct 1 12:30:10 2012 Дата индексирования: Sun Feb 3 20:36:18 2013 Кодировка: Поисковые слова: m 2

Nonlinear-optical Approach to overcome industrial pollution of space
O. Kulagin, I. Gorbunov
Institute of Applied Physics Russian Academy of Sciences, N.Novgorod, Russia


Space debris threats and application of phase conjugation methods for concentrating the debris illumination
· Nearly 90% of orbital debris has dimensions ~ 1-5 cm. This debris is not tracked and is only detectable using special phased array radars. · Debris removal demands an increase in illumination laser energy, though the concentration of the orbital debris reflected laser illumination (debris signal) is restricted by the influence of atmospheric turbulence. · Space debris illumination concentration by laser point narrowing can be achieved by means of non-linear optical phase conjugation of the debris scattered illumination. · When phase conjugation compensates for turbulent distortions, conjugated signal will be concentrated on the debris to an accuracy is determined not by the turbulent scattering angle (~10-5 rad), instead by the receiving aperture of the nonlinear optical amplifier ( ~ 510-7 rad for a receiving aperture of 200 cm). the that but e.g.,


What is phase conjugation and four wave mixing?

n=1 n

mirror

E Q

S

E E
L

R

E

+

E n=1 n

-

E

L

+

Brillouin enhanced four wave mixing

Phase conjugation mirror

E

+

E

-


Non- linear optical (BEFWM) laser image amplifier
PC-mirror lens Object plane Input lens

Laser amplifier Beam-splitter Image plane

PC- mirror via BEFWM

· The sensitivity is limited by quantum noise and is near 4.810-19 J (approximately two photons) per pixel; · Extremely narrow frequency band corresponds to two frequency-temporal modes (input spectral band ~ 0.001 nm and response time of ~ 30 nsec); · Comparatively wide field of view (350 350 pixels in image); · High coefficient of amplification (amplifies weak signal by ~ 1012).
Kulagin .V., Pasmanik G.., Shilov .. «Amplification and phase conjugation of weak signals», Sov. Phys. Usp. Vol. 35, 6, pp. 506­519. (1992)


Efficient enhancement of space debris illumination by nonlinear-optical image amplifier with BEFWM
D
SD

L

0
LA BEFWM

D

IL

MO

Pump Laser

LA ­ laser amplifier, MO ­ laser­master oscillator, IL ­ illumination laser, L ­ distance to target, D ­ primary mirror diameter, 0 ­ illumination angle

A two-step concentration of orbital debris laser illumination is sufficient for debris observation by the nonlinear optical system at distances from 600 to 800 km. The observations can be made any 5 time of the day


The scheme for concentrating illumination
/2

7
R ~ 50%
/4 CCl4-1 PA 20300

Two-pulse master oscillator

PA 20300 / 2 FR-8

1

2
PA 20300

6
PA 20300 /4 TiCl4-1

/ 2 FR-8

3

4
/2 FR-20-2

8 9

13
PA 10300

14

CCl4-2

TiCl4-2

PA 10300 /4

9

/4

11

Laser facility for model experiments at open-air test field with turbulence scaling
Photo-diode +oscilloscope o r p h o to p a p e r

turbulence

Object plane


Creation of artificial turbulence
r

Desired

0 ~ 1-2
-3 / 5

2 r0 (k 2Cn L)
=[ ], =[ ].

2 Cn 10

-12

2 CT

C

2 n=

[cm

-2 / 3

]

2 CT

=

[d

eg 2 / cm

2/3

]

CT 2|z1-z2|2/3 = (dT/dz)2 |z1-z2|2
Three heating-fans (MASTER B15) provide the required 50 kW


Measurements of turbulent strength along the path

Cn ,

2

-2/ 3

( ( ( (
08.09.09 1 1 :5 1

With heating

Cn2

= (4-20-170)*10 m

-14

-2/3 ( (

Without heating Cn2 = (2-5-7)*10-14m

-2/3
,


Detection of illumination concentration on remote target


Active action on space debris using intense lasers

Physical mechanisms of recoil impulse generation: · Developed surface evaporation of the debris
The maximum efficiency of recoil impulse at a laser intensity of I ~ 106 W/cm2

· Optical breakdown in the vapor. Laser-plasma absorption
For near IR lasers (=1.06 µm): I > 5в108 W/
2


Propulsion of SD object to elliptical lowperigee orbit
mv 2 G M m E= - 2 r
Total energy of SD object v = vr + v
rmin


p

p1
45

p0 p0

L = [ r, p ] = m v r

r0
vr = 0 Elliptical orbit: E1 , v1 , L1 , p
1

- GMm 2 L2 E = (1 - 1 + ) 23 2E ( GM ) m
0

Round orbit: E0 , v0 , L0 , p

Recoil change of energy and angular momentum:

m2 p2 p v 2 E = E1 - E0 = ( v1 - v0 ) = - 2 2m 2
L = L1 - L0 = - p r0 2

0

SD object: m = 1 kg; v0 = 7.62 km/ at r0 = R + h0 = 6371 km + 500 km this SD object shifts to desirable r
min

= 200 km

if recoil momentum is provided p = 114 kgm/

taking into consideration a mass defect m caused by evaporation we have p = 106.7 kgm/


Laser energy evaluation for SD object propulsion
It is assumed for SD m = 1 kg, velocity v0 = 7.62 km/c -p a rebound velocity of vapoured part ­ vAl (in the movable frame of reference) we have got vAl from relation: m1 2 m Al v Al 3 = kT m2 2 2 -2 6 p For Aluminium atom m Al = 4.484 10 And temperature T = 2770 K vAl = 1.60 km/ and m = 6.7% m
We have got a desirable energy of laser pulse by using Aluminium parameters

m1 v1

m1 v0
m2 v0

m2 v

2

Melting heat = 3.9105 J/kg Evaporation heat L = 9.22106 J/kg Heat capacity c = 930 J/(kg)

W As a conclusio conversion into of SD object by

= m(+L+cT) = m(3.9105 + 9.22106 + 9302770) = 807 kJ n, a laser pulse energy of 1 kJ (at repetition rate of 100 Hz and efficiency of the recoil pulse ~10%) is acceptable to provide desirable propulsion during one pass orbit

Hence, a laser output ~ 1kJ x 10 ns x 100 Hz looks sufficient for small LEO orbital 12 debris removal using non-linear optical laser energy concentration.