Terahertz frequency domain spectrometer with discrete coarse and fine tuning
AssigneeEmcore Corporation
InventorsRonald T. Logan, Joseph R. Demers
Life of this patent
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Abstract
An apparatus for analyzing, identifying or imaging an target including first and second laser beams coupled to a pair of photoconductive switches to produce CW signals in one or more bands in a range of frequencies greater than 100 GHz focused on and transmitted through or reflected from the target; and a detector for acquiring spectral information from signals received from the target and using a multi-spectral heterodyne process to generate an electrical signal representative of some characteristics of the target. The lasers are tuned to different frequencies and a frequency shifter in the path of one laser beam allows the terahertz beam to be finely adjusted in one or more selected frequency bands.
Claims20
A method for terahertz spectroscopy comprising:
- sweeping a CW radiative beam over at least one frequency band in a range of frequencies greater than 100 GHz;
- directing the radiative beam to a target;
- acquiring spectral information from the target;
- and
- finely adjusting the frequency of the CW radiative beam in frequency increments of less than 100 MHz for generating additional electrical signals representative of some characteristic of the target in the selected frequency band.
A method for analyzing, identifying, or imaging a target, said method comprising:
- providing first and second lasers having tunable frequencies, said first laser to produce a first output beam and said second laser to produce a second output beam, said first output beam and said second output beam having different frequencies;
- which may be coarsely adjusted by temperature adjustment of one of said lasers;
- producing a first composite output beam from a first portion of said first output beam and a first portion of said second output beam;
- coupling a second portion of the first output beam to a frequency control element for controllably finely adjusting the frequency of the second portion of the first output beam;
- producing a second composite output beam from the frequency adjusted second portion of said first output beam and a second portion of said second output beam;
- generating CW signals in the range of frequencies from 100 GHz to over 2 THz using said second composite output beam;
- causing said CW signals to be substantially simultaneously focused on or through said target;
- acquiring a spectral information signal from said target;
- and
- generating an electrical signal representative of a characteristic of said target based on said spectral information signal and said first composite output beam.
An apparatus for analyzing, identifying, or imaging a target, said apparatus comprising:
- first and second lasers having tunable frequencies, said first laser to produce a first output beam and said second laser to produce a second output beam, said first output beam and said second output beam having different frequencies, wherein a first portion of said first output beam and a first portion of said second output beam produce a first composite output beam which may be swept over a frequency band as the frequencies of at least one of the lasers is swept;
- a frequency shifting element coupled to a reference oscillator and positioned to receive a second portion of said first output beam to controllably shift the frequency of said second portion of said first output beam;
- a beam combiner coupled to the output the frequency shifting element and to a second portion of the second output beam to produce a second composite beam;
- a first photoconductive switch activated by said second composite output beam to produce CW signals in the range of frequencies from 100 GHz to over 2 THz;
- a radiative element for causing said CW signals to be substantially simultaneously focused on or through said target;
- a second photoconductive switch activated by said first composite output beam and positioned with respect to the target so as to acquire s spectral information signal from the target, and generating, based on said spectral information and said second composite output beam and heterodyne down conversion, an electrical signal representative of a characteristic of said target.
Dependencies are inferred from the claim text.