Principle, applications, evaluation and development of time lens

Time lens is based upon space -time duality and has been contributed much attention during the last decade as a widely used optical instrumentation. Improvement of time lens is always enhanced by development of photonics as both engineering requirements and theoretical driving. A historical overview of how this powerful framework had been exploited to develop ultra -fast optical instruments was presented. Current state of implementing time lens by phase modulator (PM), sum-frequency generation (SFG), cross-phase modulation (XPM) and four-wave mixing (FWM) were summarized and analyzed by mathematic description. Then, limitations of different implementations of time lens for applications above were analyzed, accordingly. In addition, pulse magnification and time to frequency conversion as the main applications for ultra -fast pulse measurement by time lens were outlined with emphasizing on the evaluation by performances including resolution and record length. Furthermore, some ultra-fast nonlinear principle including surface-plasmon enhanced ultra-fast second- and third-order optical nonlinearities in metallic nanostructure, strong third-order optical nonlinearity induced high efficient FWM in graphene as potential theoretical and technological opportunities to improve time lens were presented and discussed.