REMOTE SENSING APPPLICATIONS

DIFFERENTIAL ABSORPTION LIDAR (DIAL) WITH HETERODYNE DETECTION IS THE MOST SENSITIVE KNOWN TECHNIQUE FOR THE REMOTE SENSING OF TRACE CONCENTRATIONS OF GASES IN THE ATMOSPHERE. A DIAL SYSTEM BASED ON THE CO2 LASER HOLDS THE GREATEST NEAR TERM PROMISE FROM THE STANDPOINTS OF EFFICIENCY, VERSATILITY, AND RELIABILITY. TO ACHIEVE MAXIMUM ACCURACY WITH SUCH A SYSTEM, THE SIMULTANEOUS PROVISION OF TWO FREQUENCY STABILIZED PULSED LASER BEAMS ANDTWO FREQUENCY STABILIZED CW LASER BEAMS IS REQUIRED. THE PROPOSED PROGRAM IS CONCERNED WITH THE DEVELOPMENT OF A FIELDABLE CO2 LASER BASED DIAL SYSTEM WITH HETERODYNE DETECTION. THE SYSTEM WILL EMPLOY A SINGLE CO2 GAIN TUBE TOPRODUCE THE TWO FREQUENCY STABILIZED CW OUTPUTS AS WELL AS ASINGLE CO2 GAIN MEDIUM TO GENERATE THE TWO FREQUENCY STABILIZED PULSED OUTPUTS. DURING PHASE I OF THIS PROGRAM, THE RELATIVE MERITS OF TWO CONCEPTS FOR A FREQUENCY STABILIZED DUAL WAVELENGTH CW CO2 LASER WILL BE EVALUATED. THE APPROACH WITH GREATER OVERALL FREQUENCY AND AMPLITUDE STABILITY WILL BE ADOPTED AS THE LOCAL OSCILLATOR SOURCE FORTHE DIAL SYSTEM. ALSO DURING PHASE I THE CROSS SATURATION BEHAVIOUR IN A DUAL WAVELENGTH PULSED CO2 LASER WITH A NOVELDESIGN TO MINIMIZE THE MUTUAL INTERACTION OF THE TWO LASER LINES WILL BE EVALUATED.