Ultra-flat NIR-to-MIR supercontinuum source with all-silica fibers based on rectangular NLP pumping

We present, for the first time, a watt-level ultra-flat all-silica fiber supercontinuum (SC) source spanning from the near-infrared (NIR) to mid-infrared (MIR) region with negligible pump residuals. This SC source is pumped by amplified 1.57-μm rectangular noise-like pulses (NLPs), whose broad spectral and flat-top temporal characteristics enhance the spectral flatness and coverage of SC spectra. By cascading a piece of highly nonlinear silica fiber (HNLF), a SC ranging from 0.91 to 2.92 µm is obtained with a 3-dB bandwidth of ∼ 716.1 nm, a 10-dB bandwidth of ∼ 1533.6 nm, and an average power of 2.08 W. To our best knowledge, the spectral coverage, 3-dB, and 10-dB bandwidths represent the highest achieved levels for a watt-level all-silica fiber SC source covering the range from the NIR to MIR. Our system offers a simple and easily implemented solution for an ultra-flat NIR-to-MIR SC source, promising significant applications in optical coherence tomography and chemical detection.