Research On The Application Of Dual-optical Comb Imaging Technology Based On Electro-optic Modulation

Microwave and terahertz(THz)devices,such as antennas and reflectors,are useful in the fields of communication,navigation and remote sensing.Laser tracking and measuring technology plays an important role in charactering microwave /THz devices,such as surface measuring.Based on laser interferometry,laser tracking and measuring offers high spatial resolution and accuracy for precise surface topography measurements.However,due to the limitation of optical wavelength,this method has some problems,such as limited dynamic measurement range,low update rate and being difficult to measure the absolute distance.The appearance of Optical frequency comb provides a new light source for optical precision measurement.Dual-comb ranging interferometry that harnesses two asynchronous optical combs for absolute distance measurement,offers high precision,large range ambiguity and high speed.This method,without moving mirrors,has shown great advantages in laser ranging and holographic imaging.However,due to the limited frame read-out speed of cameras,the measurement process can be time-consuming.Consequently,the advantages of dual-comb technology have not been fully utilized in imaging applications.In addition,dual-comb interferometry has yet to be applied to characterization of THz devices,either.Therefore,in this paper,a method of surface shape measurement of antenna and reflector is proposed,which combines the two-optical comb single-point ranging technology with the high-speed two-dimensional galvanometer scanning method.On the other hand,Coherent Anti-Stokes Raman Scattering(CARS)spectroscopy with ultrashort pulses and a fast single-pixel photodetector has shown great potential in chemistry and biological spectroscopic imaging fields as well as transient studies.However,those systems rely on mechanical delay lines or two asynchronous optical combs with inflexible repetition frequencies,technically limiting their spectral acquisition speeds.So far,the excellent flexibility of EOC combs has not been exploited for high-speed CARS measurements.Hence,a hybrid dual-comb CARS technique that combines the advantages of a highly flexible frequency modulation(FM)EOC with the broadband fiber laser to generate ultra-high-speed CARS spectroscopy.The research content of this paper is as follows:1.The surface shape measurement technology of THz devices based on dual-comb was studied,and the surface morphology of terahertz(THz)antennas and reflectors was measured by combining the single-point ranging technology of dual-comb and high-speed two-dimensional galvanometer scanning method.In the experiment,the single scan time of the 3D surface image is 2s and the pixel count is 250 K,that is,8μs/pixel.The longitudinal measurement error is 1.3 μm(down to 5 nm at 0.1 s integration time)and the unambiguity distance can reach300 m.Experiments verify the advantages of dual-comb ranging imaging in terms of measurement time,accuracy and dynamic range,which is expected to provide a new way for high-precision surface shape measurement of microwave/THz devices.2.A hybrid dual-comb CARS technique was demonstrated,which combined the agile frequency characteristics of EOC with the spectral bandwidth of fiber lasers to achieve ultra-high-speed CARS measurements.A coherent Raman spectrum covering 2800-3200 cm-1 with a resolution of 22 cm-1 was obtained,and an acquisition speed of one million spectra per second,that is,1MHz,was achieved,which is a relatively advanced level in its class.