Introduction

The LASS-II(Laser Amplitude Stabilization System) is an electro-optic feedback loop designed to reduce amplitude variations commonly associated with most gas lasers. This system is capable of significantly enhancing the signal/noise ratio of the laser over a much broader bandwidth than typical optically coupled current modulation of the plasma tube. Both an internal and external reference input are provided, allowing analog programming of the laser through-put. This is particularly convenient for use in recording systems where laser power must be varied as a function of position on the recording medium i.e., video disc, flat bed recorders, etc. The system is composed of three separable units; feedback electronics, power supply, and electro-optic modulator with integral beamsplitter and photodiode amplifier.

LONG TERM DC STABILITY
HORIZONTAL-6 INCHES=1 HOUR
TOP TRACE·DETECTED LASER
OUTPUT
VERTICAL-1 VOLT FULL SPAN;
1 INCH=100 MV

BOTTOM TRACE·DETECTED
OUTPUT OF LASS II AT
0.5 lo MAX: FROM INITIAL TURN ON

VERTICAL-0.5 VOLT FULL SPAN;
1 INCH=50 MV
(OFFSET ADJUSTED TO CENTER TRACE)

Performance Specifications

Operating Conditions
514nm, laser power-50mw, IO=.5 lmax.,
Beam dia 1.4mm(1/e2) TEMOO

Noise Reduction(f).
  1/1@500khz(Int. Ref. mode)
  5/1@100khz
 18/1@50khz
100/1@10khz
200/1@1khz
250/1@200khz

Noise Floor - 458nm - 100db Relative to F.S.
D.C. Satability - Short Term < .02% Relative to value(@.5 lmax), T=O -> 1Hr. - 8Hr < .06% Relative to value (@.5 lmax.)
Ext. Modulation Bandwidth -(-3 db), Dc - > 50kHz (.2 - > .8 lmax)
Ext. Input Voltage. 0 - > +1 V max

Optical

Two different types of beamslitters are available so as to optimize both efficiency and finesse.
Static Transmission - 80% (excluding beamsplitter)
Useable Aperture - 2.5mm square
Optical Bandwidth - 400-800nm
Maximum Throughput Power - 3.5w/mm2 TEMOO