Line-by-line control of 10,000 modes in a 20 GHz laser frequency comb

The independent manipulation of each line in a laser frequency comb is a powerful resource for emerging applications in optical waveform synthesis, spectroscopy, quantum technology, microwave photonics, astrophotonics, and metrology. Previous demonstrations of line-by-line modulation reported the control of hundreds of comb modes, with bandwidth:resolution ratios of a few thousand. Here, we present a spectral shaper concept achieving precise amplitude control of 10,000 comb modes spanning 580–950 nm (200 THz), with a bandwidth:resolution ratio exceeding 20,000. We demonstrate its application to the dynamic flattening and free spectral range control of an astrocomb, together with fully arbitrary line-by-line grayscale modulation. Our approach is directly extendable to dual amplitude and phase shaping as an enabler for high-repetition-rate optical waveform synthesis and precision spectral shaping across unprecedented bandwidths.