Fig. 4: Spatial mode conversion of ultrashort laser pulses.
From: Precise mode control of laser-written waveguides for broadband, low-dispersion 3D integrated optics
a Schematic diagram of mode conversion from an ultrashort LP01 mode laser pulse (Core 1) to an LP21 mode pulse (Core 2) with negligible time-domain distortion. b The pulse intensity distribution measured by the autocorrelator before entering the waveguide and after propagating through the waveguide. c Supercontinuum spectra measured at pump power of 1–70 nJ. d Measured coupling ratio of Core-2 as a function of the spectral width of the input supercontinuum for directional coupling, where the 0.1 dB deviation in coupling ratios is marked (Inset: measured mode field distributions)
