Optical system, method of forming and operating the same

A method of forming an optical system for determining a refractive index of a sample, the method comprising:

• providing a laser source configured to emit a laser beam;
• providing a non-linear crystal configured to generate, based on the laser beam, an infrared light beam which passes through the sample, and a visible signal light beam;
• providing a first mirror configured to reflect the visible signal light beam;
• providing a second mirror configured to reflect the infrared light beam so that the reflected infrared light beam interacts with the reflected visible signal light beam in the non-linear crystal;
• and
• providing a photodetector configured to determine a property of the reflected visible signal light beam which has interacted with the reflected infrared light beam for determining the refractive index of the sample;
• and
• providing an adjusting system configured to adjust a position of the second mirror;
• wherein the first mirror is configured so that the reflected visible signal light beam is coherently overlapped with the visible signal light beam,
• wherein the second mirror is configured so that the reflected infrared light beam is coherently overlapped with the infrared light beam;
• and
• wherein the adjustment of the position of the second mirror varies an offset between the reflected visible signal light and the reflected infrared light, thereby varying an intensity of the reflected visible signal light beam so as to determine a real part and an imaginary part of the refractive index.

A method of operating an optical system for determining a refractive index of a sample, the method comprising:

• emitting, using a laser source, a laser beam;
• generating, based on the laser beam and using a non-linear crystal, an infrared light beam which passes through the sample, and a visible signal light beam;
• reflecting, using a first mirror, the visible signal light beam;
• reflecting, using a second mirror, the infrared light beam so that the reflected infrared light beam interacts with the reflected visible signal light beam in the non-linear crystal;
• and
• determining, using a photodetector, a property of the reflected visible signal light beam which has interacted with the reflected infrared light beam to determine the refractive index of the sample;
• adjusting, using an adjustment system, a position of the second mirror to vary an offset between the reflected visible signal light and the reflected infrared light, thereby varying an intensity of the reflected visible signal light beam so as to determine a real part and an imaginary part of the refractive index;
• wherein the first mirror is configured so that the reflected visible signal light beam is coherently overlapped with the visible signal light beam, and
• wherein the second mirror is configured so that the reflected infrared light beam is coherently overlapped with the infrared light beam.