Dual-comb spectrally encoded confocal microscopy by electro-optic modulators

We demonstrate an electro-optic (EO) based dual-comb spectrally encoded confocal microscopy (DC-SECM). With the capability of large comb spacing (∼8.1-GHz) and comb-line to pixel mapping, only thirteen comb lines are used to sample a spatial point of resolution size. Such spatial sampling effectively lessens the required average focal power for a given signal-to-noise ratio (SNR) and contributes to a higher power-efficiency, which alleviates the risk of photodamage. Furthermore, the tunable beating frequency (0–6 MHz) of dual comb interferometry (DCI) renders an achievable ultrafast imaging speed up to MHz level. The image performance was evaluated using a standard resolution target, indicating a lateral resolution of 2.76-μm, and further demonstrated with biological samples. Compared with time-stretch spectrally-encoded microscopy, the DC-SECM can not only achieve low-focal-power (∼30  μW) imaging but also function under minimum settings of both electrical bandwidth (hundreds-of MHz) and digitization sampling rate (1 Gs/s), while simultaneously maintaining a frame rate on the order of MHz.