Multiple advanced spectro-temporal characterization modalities and mid-infrared generations

Abstract

Spectral and temporal waveform characterization have been increasingly demanding in various fields including optical dynamics capture, chemical and biological observation, and medical diagnosis. Resolving those processes in ultra-short time scales with MHz frame rate would not only benefit better perception of our surrounding environment but also facilitate the understanding of the intrinsic mechanism and principles such as the formation of soliton explosion or collision. However, such a conception has an inherent gap with the current detection instruments. Due to the lack of more advancing devices, based on space-time duality, temporal imaging technique has been proposed and developed constantly to process the signal. Through the interaction between the signal and pump, the requirement for high-speed instruments is largely alleviated. In the spectral domain, for example, the time lens maps the spectrum to the temporal domain to generate a much higher frame rate. Comprehensive work has been demonstrated on temporal and spectral characterization. In the spectral domain, based on time lens, a parametric spectro-temporal analyzer (PASTA) has been brought up to collect the spectrum with higher resolution and frame rate. Compared to conventional dispersive Fourier transform (DFT), PASTA distinguishes itself from better sensitivity and larger bandwidth. In the temporal domain, a panoramic-reconstruction temporal imaging (PARTI) system was built and extremely extends the recording length of a conventional time magnifier. Nevertheless, the potential of the time lens in spectral and temporal signal processing has not been completely unleashed especially the polarization information. In the field of imaging, a temporal encoded amplified tomography is constructed combined with an optical time-domain reflectometer. The promising temporal resolution provided by the temporal magnifier has enhanced the axial resolution to tens of microns. Compared to conventional tomography, it has a faster imaging speed and larger imaging depth. In the temporal domain, to capture the pure intensity information, a polarization-independent time magnifier with the sub-ps temporal resolution is proposed to extract the polarization information. Such a modality bridged the gap that conventional time magnifier is unable to detect. In the spectral domain, most spectrum analysis techniques focus on intensity capture, while the polarization information is neglected for a long period. To reveal the polarization distribution, a polarization reconstructed PASTA is demonstrated first, in which the polarization of the signal has been characterized on an ultrafast scale and MHz frame rate. Finally, since the spectral and temporal characterization of telecom bands has been explored relatively thoroughly, novel optical generations are desired to perform more powerful techniques. Mid-infrared (MIR) sources, thanks to their resonance with certain molecules, have been increasingly attractive recently. Besides, the commercial detection devices are not mature to achieve ultrafast temporal characterization. There would be great potential remained to be dug out in this special region. In summary, the characterization of temporal and spectral information in ultrafast optics is of great merit for tremendous applications. This thesis presents multiple advanced modalities that are based on the time magnifier and extend the optical source to longer regimes to better demonstrates its capability.