Method for imaging or spectroscopy with a non-linear interferometer

Apparatus for imaging and/or spectroscopy using an interferometer setup, comprising

• a pump source to generate a pump beam, and
• a first signal s1 and idler i1 field generation means pumped by the pump beam, and
• a second signal s2 and idler i2 field generation means pumped by the pump beam,
• wherein the first and the second field generation means are
• two spatial separated non-linear media pumped by the pump beam, or
• one non-linear medium, pumped by the pump beam a first time to generate a first signal s1 and idler i1 field and pumped a second time to generate a second signal s2 and idler i2 field, and
• an object to be measured which is illuminated, respectively by transmission or reflection, by the first idler field i1, and
• a signal combining means to overlap the first signal s1 and second signal s2 fields, such that the two fields interfere, and
• an idler combining means to overlap the first idler i1 and second idler i2 fields, such that the two fields are indistinguishable, and
• a detection means to detect the intensity and/or phase of the interfered signal field, characterized in that,
• a phase shifter is arranged in the first signal s1 field, and/or in the second signal s2 field, and/or in the pump beam, and/or in the indistinguishable first and second signal fields s1 and s2, wherein the phase shifter is adapted to introduce a phase shift α in the apparatus during the measurement in order to get an image and/or a spectrum of the object, and the phase shift α is varied during the measurement in a known manner.

A non-transient computer-readable medium having stored thereon a computer-readable program for executing a method for at least one of imaging or spectroscopy using an interferometer setup, the method comprising the steps of:

• i) generation of a first signal field s1 and a first idler field i1, by pumping a first non-linear medium with a pump beam, such that the two fields are correlated,
• ii) illumination of an object with the first idler i1 field, respectively by transmission and/or reflection,
• iii) generation of a second signal field s2 and a second idler field i2,
• by pumping a spatial separate second non-linear medium with the pump beam, or
• by pumping the first non-linear medium a second time with the pump beam,
• such that the two fields are correlated,
• iv) combination of the first i1 and second i2 idler fields, such that the two fields are indistinguishable, and
• combination of the first s1 and second s2 signal fields, such that the two fields interfere,
• v) first measurement of the interfered signal field s12 by a detection means,
• vi) one or more additional measurements of the interfered signal field sit by the detection means,
• wherein for each additional measurement in step vi) a phase shift α is generated in the interferometer setup, and the phase shift α is varied from measurement-to-measurement in a known manner, and
• wherein the first measurement in step v) and the one or more additional measurements in step vi) are all carried out within a stability time of the interferometer setup, and vii) calculation of a phase function Φ of the object out of the measurements from step v) and step vi) in order to get an image and/or a spectrum of the object.