Computational dual comb broadband spectroscopy method and system

A method for operating a mid-IR DCS system which functions in a control regime for periodically controlling a PRF difference between two FCs of the DCS, and a monitoring regime for continuously monitoring the PRF difference with free running FCs, wherein the method of operating the DCS in the monitoring regime comprising:

• combining the outputs of respective FCs into a combined output and splitting the combined output into two beams with a uniform spectrum;
• guiding the split beams along respective sample-investigating and reference channels through a sample to be tested and a cell with etalon material, thereby generating respective sample investigating (SI) and cell signals, the cell signal containing a spectrum of the etalon material;
• detecting SI and cell signals by respective PDs which output respective heterodyned SI and cell signals whose interferograms are recorded;
• slicing the interferograms of respective heterodynes SI and cell signals each into a sequence of uniform frames and processing each frame of the heterodyned cell signal by:
• mathematically transforming the frame to a corresponding spectrum which includes one or more molecular lines of the etalon material spectrum;
• filtering out a single molecular line from the corresponding spectrum;
• determining a phase change in the filtered single molecular line based on a reference value, thereby restoring the spectrum of each frame to the desired spectrum.

A computational mid-IR dual comb spectroscopy (DCS) system operating in a control regime and a monitoring regime, the DCS system operating in the monitoring regime comprising:

• free running frequency combs (FCs) generating respective outputs at pulse repetition frequencies (PRF) which are offset relative to one another, wherein the outputs are optically combined into a system output which is split into first and second beams propagating along respective sample investigating (SI) and reference optical channels;
• a cell with etalon material located in the reference channel and interacting with the first beam so as to output a cell signal including an etalon cell spectrum of the etalon material;
• and
• a data processing unit (DPU) receiving the cell signal and executing a program for
• filtering a single molecular line of the etalon cell spectrum,
• determining a phase change in the filtered molecular line, and
• comparing the determined phase change to a reference value and, if needed, correcting the determined phase change which is used to restore a desired etalon spectrum of the cell signal.