PHASE STABILIZED LASER DIODE

WE PROPOSE TO CARRY OUT RESEARCH LEADING TO THE DEVELOPMENT OF A STABILIZED LASER DIODE WHICH CAN BE LOCKED TO THE FREQUENCY OF ANY ATOMIC OR MOLECULAR ABSORPTION LINE LYING WITHIN THE TUNING RANGE OF THE DIODE. WATER VAPOR IS A PARTICULARLY CONVENIENT SOURCE OF AN ABUNDANT NUMBER OF ABSORPTION LINES IN THE SPECTRAL REGION OF INTEREST. THE UNIQUE FEATURE OF THE PROPOSED STABILIZATION TECHNIQUE IS THE USE OF INTERFEROMETRIC PHASE DETECTION OF THE ZERO-CROSSING POINT OF THE ANOMALOUS DISPERSION CURVE AT THEPOSITION OF LINE CENTER. PHASE DETECTION HAS THE ADVANTAGE OF BEING INSENSITIVE TO INTENSITY FLUCTUATIONS AND TO DYNAMIC IMBALANCES BETWEEN THE INTERFERING BEAMS. OPTRA PROPOSES TO USE A POWERFUL PHASE MEASUREMENT ALGORITHM AND ASSOCIATED ELECTRONIC PROCESSOR, DEVELOPED FOR A DIFFERENT APPLICATION IN PRECISION METROLOGY, TO SENSE PHASE WITH A PRECISION OF BETTER THAN 0.001 RADIAN-CORRESPONDING TO A LASER DIODE FREQUENCY STABILITY OF BETTER THAT 1 PART IN 10(8) FOR A 10 KHZ MEASUREMENT BANDWIDTH. OUR PRIMARY MOTIVATION IN THIS PROGRAM IS THE DEVELOPMENT OF A SMALL, EFFICIENT AND INEXPENSIVE REPLACEMENT FOR THE GAS LASERS PRESENTLY USED FOR PRECISION METROLOGY. ANOTHER APPLICATIONOF POTENTIAL COMMERCIAL VALUE IS THE GENERATION OF STABLE MICROWAVE FREQUENCIES WITH AN ENORMOUS TUNING RANGE (BY MIXING THE OUTPUTS FROM TWO STABILIZED LASERS).