Optical refraction barometer

An optical refraction barometer for measuring pressure based on refractivity changes between a fixed length optical reference cavity and a fixed length optical sample cavity of a dual fixed length optical cavity refractometer, the optical refraction barometer comprising:

• an optical light source that produces laser light;
• an optical frequency controller in optical communication with the optical light source and that:
• receives the laser light from the optical light source;
• receives an optical feedback signal from an electronic reference arm;
• and
• produces primary light from the laser light based on the optical feedback signal;
• a first optical phase controller in optical communication with the optical frequency controller and that:
• receives the primary light from the optical frequency controller;
• receives a reference phase control signal;
• and
• produces an input reference light from the primary light based on the reference phase control signal;
• a first polarization controller in optical communication with the first optical phase controller and that:
• receives the input reference light from the first optical phase controller;
• communicates the input reference light to a dual fixed length optical cavity refractometer;
• receives an output reference light from the dual fixed length optical cavity refractometer;
• and
• communicates the output reference light to an electronic reference arm;
• the electronic reference arm in optical communication with the first polarization controller and that:
• receives the output reference light from the first polarization controller;
• produces the reference phase control signal from the output reference light and communicates the reference phase control signal to the first optical phase controller;
• produces the optical feedback signal and communicates the optical feedback signal to the optical frequency controller and optionally communicates the optical feedback signal to the optical light source;
• a second optical phase controller in optical communication with the optical frequency controller and that:
• receives the primary light from the optical frequency controller;
• receives a sample phase control signal from an electronic sample arm;
• and
• produces an input sample light from the primary light based on the sample phase control signal;
• a second polarization controller in optical communication with the second optical phase controller and that:
• receives the input sample light from the second optical phase controller;
• communicates the input sample light to the dual fixed length optical cavity refractometer;
• receives an output sample light from the dual fixed length optical cavity refractometer;
• and
• communicates the output sample light to the electronic sample arm;
• the electronic sample arm in optical communication with the second polarization controller and in electrical communication with the second optical phase controller, the electronic sample arm comprising:
• a detector that receives the output sample light from the second polarization controller and produces a reference cavity signal from the output sample light;
• a second sideband frequency generator that produces a second sideband frequency;
• a mixer in electrical communication with the detector and the second sideband frequency generator and that produces an error signal that comprises the reference cavity signal and the second sideband frequency;
• and
• a first sideband frequency generator in electrical communication with the mixer and that receives the error signal from the mixer and produces a first sideband frequency from the error signal from which the sample phase control signal is produced by the electronic sample arm for communication to the second optical phase controller;
• and
• the dual fixed length optical cavity refractometer comprising:
• the fixed length optical reference cavity in optical communication with the first polarization controller and that:
• receives the input reference light from the first polarization controller;
• propagates the input reference light through fixed length optical reference cavity;
• and
• produces the output reference light by reflecting input reference light from a mirror disposed at a terminus of the fixed length optical reference cavity disposed optically distal to the first polarization controller;
• and
• the fixed length optical sample cavity in optical communication with the second polarization controller and that:
• receives the input sample light from the second polarization controller;
• propagates the input sample light through the fixed length optical sample cavity;
• and
• produces the output sample light by reflecting the input sample light from a second mirror disposed at a terminus of the fixed length optical sample cavity disposed optically distal to the second polarization controller.