Apparatus, method and computer-readable storage medium for determining the ring-down time in a spectrometer system

A method comprising:

• transmitting a continuous-wave electromagnetic signal at each of one or more selectable, transmission frequencies in the Terahertz region of the electromagnetic spectrum, the electromagnetic signal being transmitted from a transmitter in a cavity ring-down spectrometer;
• modulating the electromagnetic signal at a modulation frequency;
• passing at least a portion of the modulated electromagnetic signal through a cavity resonator, wherein the transmitter and cavity resonator are configured so as to excite a single resonant mode of the cavity resonator;
• receiving a measurement of the portion of the modulated electromagnetic signal passing the cavity resonator;
• determining a phase shift of the modulated electromagnetic signal at the modulation frequency based upon the measurement;
• and
• calculating a ring-down time of the cavity resonator as a function of the phase shift.

A computer-readable storage medium having computer-readable program code portions stored therein, the computer-readable program portions comprising:

• a first executable portion configured to receive a measurement, the measurement having been received from a spectrometer system configured to:
• transmit a continuous-wave electromagnetic signal at each of one or more selectable, transmission frequencies in the Terahertz region of the electromagnetic spectrum, the electromagnetic signal being transmitted from a transmitter in a cavity ring-down spectrometer;
• modulate the electromagnetic signal at a modulation frequency;
• and
• pass at least a portion of the modulated electromagnetic signal through a cavity resonator, wherein the transmitter and cavity resonator are configured so as to excite a single resonant mode of the cavity resonator, the measurement comprising a measurement of the portion of the modulated electromagnetic signal passing the cavity resonator;
• a second executable portion configured to determine a phase shift of the modulated electromagnetic signal at the modulation frequency based upon the measurement;
• and
• a third executable portion configured to calculate a ring-down time of the cavity resonator as a function of the phase shift.