Raman spectroscopy system with standoff detection

A method for measuring a Raman signal, the method comprising:

• producing a pump beam of light at a pump frequency;
• producing a Stokes beam of light at a Stokes frequency, wherein the pump and Stokes frequencies are offset by a frequency offset Ω, and wherein the pump and Stokes beams are directed to an object;
• collecting a Raman signal produced by coherent Raman scattering of the pump and Stokes beams of light at the object;
• detecting the Raman signal, comprising:
• producing a probe beam of light at a probe frequency;
• coherently mixing the Raman signal with the probe beam of light to produce a corresponding photocurrent signal;
• and
• producing a digital output signal corresponding to the photocurrent signal;
• and
• determining a characteristic of the photocurrent signal based on the digital output signal.

One or more computer-readable non-transitory storage media embodying software that is operable when executed to:

• produce a pump beam of light at a pump frequency;
• produce a Stokes beam of light at a Stokes frequency, wherein the pump and Stokes frequencies are offset by a frequency offset Ω, and wherein the pump and Stokes beams are directed to an object;
• collect a Raman signal produced by coherent Raman scattering of the pump and Stokes beams of light at the object;
• detect the Raman signal, comprising:
• produce a probe beam of light at a probe frequency;
• coherently mix the Raman signal with the probe beam of light to produce a corresponding photocurrent signal;
• and
• produce a digital output signal corresponding to the photocurrent signal;
• and
• determine a characteristic of the photocurrent signal based on the digital output signal.