Dual laser frequency combs can rapidly measure high resolution linear absorption spectra. However, one-dimensional linear techniques cannot distinguish the sources of resonances in a mixture of different analytes, nor separate inhomogeneous and homogeneous broadening. These limitations are overcome by acquiring high resolution multi-dimensional non-linear coherent spectra with frequency combs.

Methods of performing dual-comb interferometry using a dual-comb interferometer and methods of characterizing a volume using dual-comb interferogram data are described.

An apparatus, including: an electromagnetic radiation source producing radiation for illuminating a sample located at an optical path depth, the electromagnetic radiation source providing the radiation to the sample to facilitate determining the optical path depth within the sample: an interferometer including: a reference arm a first portion of the radiation is delivered to, a sample arm to which a second portion of the radiation is delivered, a first optical subsystem coupled to the sample arm to interrogate the sample with the radiation delivered to the sample arm and to collect backscattered radiation from the sample, and a second optical subsystem coupled to the reference arm and the first optical subsystem to generate interference fringes between the collected backscattered radiation and the radiation delivered to the reference arm; and a data collection and processing system configured to compute the optical path depth of the sample from the received interference fringes.

A method including: scanning a sample over a period of time using an electro-magnetic radiation source, the period of time including a first time period and a second time period, a sample portion of the electro-magnetic radiation source being directed to the sample in a sample arm of an optical interferometric system, and a reference portion of the electro-magnetic radiation source being directed to a reference arm of the optical interferometric system; applying, using a phase modulator, a phase shift comprising a first phase shift and a second phase shift to at least one of the reference portion or the sample portion of the electro-magnetic radiation source, the first phase shift being applied during the first time period and the second phase shift being applied during the second time period, the second phase shift having a difference of 90 degrees from the first phase shift.

Provided is an optical self-heterodyne detection system. The system includes a light source configured to generate light, a photodetector configured to detect the light, a programmable filter provided between the photodetector and the light source, and an electrical spectrum analyzer connected to the photodetector and configured to analyze a frequency and wavelength of the light using a detection signal of the photodetector. The light source may include a frequency comb light source.

An optical comb filter, comprising an input/output collimator (50), an output collimator (60), a spectroscope (10), and first, second and third GT resonant cavities (20, 30, 40), wherein each GT resonant cavity comprises a transparent solid block coated with a membrane layer and a spacing part, a through hole is provided on the transparent solid block, and the transparent solid block and the spacing part form a hollow cavity; and rectangular orientation of an insertion loss curve is realized, and the bandwidth utilization rate is high.

An apparatus can be provided which can include a laser arrangement which can be configured to provide a laser radiation, and can include an optical cavity. The optical cavity can include a dispersive optical first arrangement which can be configured to receive and disperse at least one first electro-magnetic radiation so as to provide at least one second electro-magnetic radiation. Such cavity can also include an active optical modulator second arrangement which can be configured to receive and modulate the at least one second radiation so as to provide at least one third electro-magnetic radiation. The optical cavity can further include a dispersive optical third arrangement which can be configured to receive and disperse at least one third electro-magnetic radiation so as to provide at least one fourth electro-magnetic radiation. For example, actions by the first, second and third arrangements can cause a spectral filtering of the fourth electro-magnetic radiation(s) relative to the first electro-magnetic radiation(s). The laser radiation can be associated with the fourth radiation(s), and a wavelength of the laser radiation can be controlled by the spectral filtering caused by the actions by the first, second and third arrangements.

A shape measurement method of the present invention includes: a step of irradiating a measurement object with an optical pulse train in which a plurality of optical pulses that have predetermined frequency distributions on a time axis are disposed chronologically in numerical order; and a step of measuring an optical shape of the measurement object in accordance with a correspondent relation between numbers of the optical pulses of a plurality of detection target optical pulse trains after the emitted optical pulse train acts on the measurement object and a correspondent relation between the frequency distributions in the optical pulses.

An optical coherence tomography (OCT) system combining multiple wavelengths is generally described. In an example, the OCT system includes multiple wavelength swept light sources. The system further includes an interferometer into which light from the light sources is directed and a detector configured to produce an imaging sample signal based on light received from the interferometer. The system also includes a splitter configured to split light from at least one of light sources before the light reaches the interferometer. The system also includes a wavelength reference filter having an equal interval frequency comb and a signal processing circuit. The wavelength reference filter is configured to produce a sequential clock waveform from light received from the splitter, and the signal processing circuit is configured to resample the imaging sample signal based on the sequential clock waveform.

An optical coherence tomography (OCT) system combining multiple wavelengths is generally described. In an example, the OCT system includes multiple wavelength swept light sources. The system further includes an interferometer into which light from the light sources is directed and a detector configured to produce an imaging sample signal based on light received from the interferometer. The system also includes a splitter configured to split light from at least one of light sources before the light reaches the interferometer. The system also includes a wavelength reference filter having an equal interval frequency comb and a signal processing circuit. The wavelength reference filter is configured to produce a sequential clock waveform from light received from the splitter, and the signal processing circuit is configured to resample the imaging sample signal based on the sequential clock waveform.