Fig. 1. Schematic of a spectrum shuttle. (a) Top view of the overall optical configuration. (b) Pulse separation by a pair of parallel mirrors (mirrors 1 and 2) indicated by the orange dashed square in (a). (c) Pulse traveling between parallel mirrors indicated in the blue dashed square in (b). BS, beam splitter; SLM, spatial light modulator.

Fig. 2. Relationships of the basic parameters in a spectrum shuttle. (a) Variations of the temporal delay derived from the parallel mirrors, Tpm, with a distance between the parallel mirrors in the z direction, Z. (b) Rotation angles of the mirrors around the y and x axes, θ and ϕ, according to Tpm, respectively. Here, the absolute shifts in the x and y directions in each lap, X and Y are fixed at 5 and 2 mm, respectively, for both (a) and (b).

Fig. 3. Production of spectrally separated pulse trains by a spectrum shuttle. (a)–(d) Time-varying signals and spectra of five pulses with the intervals of 250 ps in the 800- and 400-nm bands. (e), (f) Spectra of the pulse trains discretized by shielding at one end between mirrors 2 and 3. (g), (h) Time-varying signals when the number or time interval of the pulses is changed in the 800-nm band.

Fig. 4. Single-shot transmission spectroscopic imaging of laser ablation dynamics using pulse trains produced by spectrum shuttles in the 800- and 400-nm bands as probes. (a) Experimental setup. (b) Two-color transmittance distributions, T800 and T400, and transmittance ratio between two wavelength bands, T400/T800, during the laser ablation dynamics. BS, beam splitter; BBO, beta barium borate; DM, dichroic mirror; L, lens; Obj., objective lens; SF, spectral filtering; DOE, diffractive optical element; BPF, bandpass filter.

Fig. 5. Production of individually spatially shaped pulse trains by a spectrum shuttle with an SLM. (a) Experimental setup for modulating the third pulse only. (b) Phase patterns of the third pulse modulated by the SLM. (c) Beam profiles of the pulse propagated at ∼1700mm from the SLM under three conditions. On the right side, the average intensities of the pulses in the range of 2 mm at each y coordinate are shown.