THE DEVELOPMENT OF A MOLECULAR INTRACAVITY DIODE-LASER ABSORPTION SPECTROMETER (MIDAS)

THERE IS A NEED FOR CHEMICAL VAPOR MONITORS THAT ARE VERY SENSITIVE AND SELECTIVE. OPTICAL TECHNIQUES ARE WELL SUITEDFOR THIS PROBLEM, BECAUSE THEY OFFER SELECTIVITY, SENSITIVITY, RAPID RESPONSE, AND CAN BE USED IN EXTREME TEMPERATURE AND PRESSURE ENVIRONMENTS. HOWEVER, IT IS DIFFICULT TO COMBINE THESE FEATURES IN A SINGLE SIMPLE DEVICE. INTRACAVITY DIODE LASER ABSORPTION OFFERS THE PROMISE OF COMBINING THESE FEATURES. INTRACAVITY ABSORPTIONINVOLVES PLACING THE SAMPLE WITHIN A LASER CAVITY, WHICH PROVIDES MULTIPLE PASSES THROUGH THE SAMPLE. VERY LONG ABSORPTION PATH LENGTHS CAN BE ATTAINED ON THE ORDER OF HUNDREDS OF KILOMETERS FOR A 10-CM LASER CAVITY. FURTHERMORE, THE DIODE LASERS CAN BE TUNED TO SPECIFIC WAVELENGTHS SO THAT PARTICULAR MOLECULAR SPECIES CAN BE MONITORED. IN PHASE I, AN EXTENDED CAVITY DIODE LASER WILL BE CONSTRUCTED TO DEMONSTRATE THE FEASIBILITY OF USING GAALAS DIODES FOR INTRACAVITY ABSORPTION DETECTION. THE RESULTS OBTAINED FROM THE PHASE I MEASUREMENTS WILL BE USED TO DESIGN A BREADBOARD MOLECULAR INTRACAVITY DIODE-LASER ABSORPTION SPECTROMETER (MIDAS) TO BE BUILT IN PHASE II.