Abstract: An apparatus is provided that includes a field reflector and a plurality of pairs of object reflectors. The apparatus also includes a plurality of source and detector port pairs, where each source port is configured to pass a beam of radiation, and each detector port is configured to receive a beam of radiation. The source and detector ports of each pair are positioned proximate an outer edge of the field reflector such that an optical axis of the field reflector lies between the respective source port and detector port. The object reflectors and source and detector port pairs are arranged such that each source and detector port pair is associated with a respective pair of object reflectors forming a distinct channel, where the source and detector port pair, and centers of the associated pair of object reflectors, of each channel lie in a distinct plane.

Abstract: A method is provided that includes receiving and processing a sample signal scan. Processing the sample signal scan includes applying an inner-product operation on the sample signal scan and each of a plurality of eigenvectors to generate a plurality of corresponding coefficients, and subtracting the sample signal scan from a linear combination of the eigenvectors and corresponding coefficients to thereby produce a corrected sample signal scan. In this regard, the eigenvectors have been generated by decomposing a plurality of background reference signal scans according to a singular value decomposition technique. The signal scans include a plurality of electromagnetic signal measurements at a discrete set of frequencies, where each measurement has been taken by a spectrometer system passing an electromagnetic signal through a sample cell including just a base medium (for the background reference signal scans), or both a base medium and a sample medium (for the sample signal scan).

Abstract: A system is provided that includes a cavity ring-down spectrometer and a processor. The spectrometer is configured to pass, through a cavity resonator, a modulated, continuous-wave electromagnetic signal at each of one or more selectable, transmission frequencies in the Terahertz region of the electromagnetic spectrum. The spectrometer includes a transmitter that, with the cavity resonator, is configured so as to excite a single resonant mode of the cavity resonator. The processor is configured to receive a measurement of the passed portion of the modulated electromagnetic signal, and determine a phase shift of the modulated electromagnetic signal based upon the measurement. The processor is then configured to calculate a ring-down time of the cavity resonator as a function of the phase shift.

Abstract: An apparatus is provided that includes a field reflector and a plurality of pairs of object reflectors. The apparatus also includes a plurality of source and detector port pairs, where each source port is configured to pass a beam of radiation, and each detector port is configured to receive a beam of radiation. The source and detector ports of each pair are positioned proximate an outer edge of the field reflector such that an optical axis of the field reflector lies between the respective source port and detector port. The object reflectors and source and detector port pairs are arranged such that each source and detector port pair is associated with a respective pair of object reflectors forming a distinct channel, where the source and detector port pair, and centers of the associated pair of object reflectors, of each channel lie in a distinct plane.

Abstract: A system is provided that includes a cavity ring-down spectrometer and a processor. The spectrometer is configured to pass, through a cavity resonator, a modulated, continuous-wave electromagnetic signal at each of one or more selectable, transmission frequencies in the Terahertz region of the electromagnetic spectrum. The spectrometer includes a transmitter that, with the cavity resonator, is configured so as to excite a single resonant mode of the cavity resonator. The processor is configured to receive a measurement of the passed portion of the modulated electromagnetic signal, and determine a phase shift of the modulated electromagnetic signal based upon the measurement. The processor is then configured to calculate a ring-down time of the cavity resonator as a function of the phase shift.

Abstract: A system includes a transmitter is configured to transmit an electromagnetic signal to a receiver, which is configured to receive the electromagnetic signal and another electromagnetic signal for mixing therewith. Propagation paths of the signals to the transmitter and receiver include a first propagation path of the electromagnetic signal to the transmitter, and a second propagation path of the other electromagnetic signal to the receiver. The arrangement, which is located along either or each of the propagation paths of signals to the transmitter and receiver, is configured to alter the length of a respective propagation path. And the processor configured to recover an amplitude and phase of the transmitted electromagnetic signal, including being configured to receive a sequence of samples of the received electromagnetic signal, and Discrete Fourier Transformation process the sequence of samples.

Abstract: A system includes a transmitter is configured to transmit an electromagnetic signal through a sample cell (including a sample medium) to a receiver, which is configured to receive the electromagnetic signal and another electromagnetic signal for mixing therewith. Propagation paths of the signals to the transmitter and receiver include a first propagation path of the electromagnetic signal to the transmitter, and a second propagation path of the other electromagnetic signal to the receiver. The arrangement, which is located along either or each of the propagation paths of signals to the transmitter and receiver, is configured to alter the length of a respective propagation path. And the processor configured to recover an amplitude and phase of the transmitted electromagnetic signal, and calculate a complex index of refraction of the sample medium as a function of the amplitude and phase of the transmitted electromagnetic signal.

Abstract: A system includes a transmitter is configured to transmit an electromagnetic signal through a sample cell (including a sample medium) to a receiver, which is configured to receive the electromagnetic signal and another electromagnetic signal for mixing therewith. Propagation paths of the signals to the transmitter and receiver include a first propagation path of the electromagnetic signal to the transmitter, and a second propagation path of the other electromagnetic signal to the receiver. The arrangement, which is located along either or each of the propagation paths of signals to the transmitter and receiver, is configured to alter the length of a respective propagation path. And the processor configured to recover an amplitude and phase of the transmitted electromagnetic signal, and calculate a complex index of refraction of the sample medium as a function of the amplitude and phase of the transmitted electromagnetic signal.

Abstract: A system includes a transmitter is configured to transmit an electromagnetic signal to a receiver, which is configured to receive the electromagnetic signal and another electromagnetic signal for mixing therewith. Propagation paths of the signals to the transmitter and receiver include a first propagation path of the electromagnetic signal to the transmitter, and a second propagation path of the other electromagnetic signal to the receiver. The arrangement, which is located along either or each of the propagation paths of signals to the transmitter and receiver, is configured to alter the length of a respective propagation path. And the processor configured to recover an amplitude and phase of the transmitted electromagnetic signal, including being configured to receive a sequence of samples of the received electromagnetic signal, and Discrete Fourier Transformation process the sequence of samples.

Abstract: A system for processing signals includes a receiver assembly for receiving a signal. The signal has a sample component with a sample electric field and a sample polarization, and has a reference component with a reference electric field and a reference polarization. The receiver assembly includes an analyzer for polarimetrically processing the signal, including differencing the signal to generate a difference electric field proportional to the difference of the sample and reference electric fields. By polarimetrically differencing the signal, the analyzer reduces the magnitude of the common-mode signal at the difference signal receiver. The receiver assembly includes an electric-field detector for measuring the difference electric field such that the reduction in common-mode amplitude decreases the noise equivalent power of the electric-field detector.