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Stimulated Brillouin scattering laser for precision satellite tracking
V. Burmistrov, A. Koltsov
OJC PRC "Precision Systems and Instruments", Moscow, Russia

I. Gorbunov, O. Kulagin
Institute of Applied Physics, Nizhny Novgorod, Russia


Picosecond Solid-state Lasers
· mode-locked lasers - pulse energy ~ 1mJ, pulse width < 1 ps, but complex optical scheme; diode pumped microchip lasers - pulse width ~ 40-50 ps, but low pulse energy; lasers with SBS and SRS pulse compression ­ any pulse energy, pulse compression of passive Q-switched pulse to 1 ps, simple schematic decisions

·

·


Brillouin (or Raman) pulse compression


Fluorocarbons as Brillouin media


Schemes of SBS-lasers:
Conventional
2 В 5ns; 2 В 5mJ P /4 R = 30 В 40% CCl4, SnCl
4

New, based on fluorocarbons
2 В 5ns; 2 В 5mJ P /4 No Optical Breakdown! R = 97% C8F
18

MO PA
/4 P

MO

PA

160 В 350 ps; up to 0.5 J

90 В 500 ps; up to 0.5 J



small SBS-mirror reflectivity small amplifier energy extraction thermal aberrations in Nd:YAG pulse compression up to 150ps energy stability StDev532nm 6.5%



SBS-mirror reflectivity > 97% Gaussian output beam profile phase-conjugated beam pulse compression up to 90ps energy stability StDev532nm 3%


Example of SBS-pulse compression
From MO: ~2ns, SLM After SBS-Amplifier-Compressor: ~110ps

18 times

Tektronix, 1GHz

Hamamatsu, 2ps


Scheme of SBS-laser
(1) Master-oscillator; (2) Nd:YAG AR@1064+HR@1064 / LR@808; (3) Cr:YAG; (4) polarizer; ( 5) spherical output coupler: resonator length ~30 ; (6) polarizer; (7) +(9) beam expander; (8) Faraday rotator; (10) half-wave plate; (11) (12) turning mirrors; (13) polarizer; (14) quarter-wave plate (15) power amplifier; (16) Nd:YAG laser rod; (17) compensating lens; (18) back miror; (20) negative lens; (21) turning mirror; (22) focusing lens; (23) SBS ­cell; (24) quarter-wave plate; (25) beam expander ; (26) KTP crystal; (27) +(28) turning mirrors; (29) output window


View of SBS-laser

Dimensions:

520 x 315 x 150 mm2

Temperature range: - 400 В + 500


Output energy and beam quality of SBS-laser

Beam quality M2 1.2 at output beam diameter of 1.5 mm W W
532

2 mJ

at

sbs

= 3.5 +/- 0.02 mJ


Output pulse of SBS-laser

At measurements by LeCroy 820Zi
250 ps

(8 GHz, 50 ps/div)

sbs 90 ps

Measurements by streak-camera (maximal resolution of 1 ps) 532 nm 70 В 80 ps


Possible upgrade of SBS-laser
PLR (1064 nm)

MO

FR

/2(1064 nm)

PLR (1064 nm)
/4 (1064 nm)

PA SBS-cell

SHG PLR(532 nm)

/2 (532 nm)

/4 (532 nm)

From theory: minimal SBS-compressed pulse
Here period of hypersound wave Ts = L / 2v
s

sbs

~ 0.1Ts

(L ­ laser pump wavelength, vs ­ hypersound velocity in Brillouin medium)

As for fluorocarbons vs 500 m/s so Ts (1064 nm) 1 ns By transition to SBS at 532 nm we will have
sbs

(532 nm) 50 ps