Recently,the Shenguagn II research team at the Shanghai Institute of Optics and Fine Mechanics (SIOM),Chinese Academy of Sciences,has made progress in the research of high-resolution arbitrary temporal shaping technology for laser pulses. The related research findings have been published in Photonics Research under the title"Nonlinear Spectral-Temporal Manipulation for Chirp-Free Pulse Synthesis at Picosecond Resolution."
Optical arbitrary waveform generation technology holds broad application value in fields such as high-energy-density physics,laser micro-processing, and optical communications. Among these, the Spike Train of Uneven Duration and Delay (STUD) pulse sequence, as a technical solution capable of effectively suppressing various instabilities in laser-plasma interactions, has attracted significant attention. However, current mainstream pulse shaping technologies face challenges such as insufficient temporal resolution, limited record length, and the presence of residual chirp, making it difficult to meet the technical requirements for generating STUD pulses.
Addressing the aforementioned challenges, the research team innovatively proposed a pulse temporal arbitrary shaping technique based on four-wave mixing in optical waveguides, named Four-wave Optical-waveguided Chirp-free Ultrafast Shaping (FOCUS). They successfully demonstrated the generation of a chirp-free pulse sequence with a temporal resolution of 2 ps, a record length of 400 ps, and a center wavelength tunable range of 3.5 nm. This technology provides a viable technical pathway for generating laser pulses required by STUD and other schemes, while also possessing the potential for development towards integrated optical arbitrary waveform generation chips.
This work was supported by projects such as the Chinese Academy of Sciences Strategic Priority Research Program and the Shanghai Oriental Talents Program.
Fig. 1. The principle,experimental setup,analogous representation,and conceptual diagrams of the FOCUS method.(a) Schematic illustration of the FOCUS. (b) Spatial representation of frequency-to-time conversion in FOCUS. (c) Experimental setup of the FOCUS system based on FWM via fiber optics. (d) Conceptual diagram of the on-chip FOCUS system. MLL: mode-locked laser;SMF: single-mode fiber;OC: fiber optical coupler;AMP: amplifier;SS: spectral shaper;PC: polarization controller;BPF: band-pass filter;HNLF: highly nonlinear fiber;COMP: compressor;GVD: group velocity dispersion.
Fig. 4. Experimental results of the FOCUS system. (a) Signal spectrum in the primary configuration for testing system record length. (b) Signal spectrum in the second configuration for testing system resolution. (c) Idler spectrum in the primary configuration. (d) Idler spectrum in the second configuration. (e) Output temporal profile (blue line) in the primary configuration, measured by a 30 GHz oscilloscope with a 45 GHz photodetector. The red line shows alternative output sub-pulse intensity distribution obtained by adjusting the polarization state of the pulses before the FWM process. (f) Output temporal profile measured by an autocorrelator in the second configuration.
The link for the publish：https://doi.org/10.1364/PRJ.562593.
