Deep-ultraviolet second harmonic generation down to 150 nm in a quartz crystal with chirped dual-periodic superstructure

Deep-ultraviolet (DUV) second harmonic generation (SHG) can realize the coherent sources for some modern equipment and optical spectroscopy measurements, however, that with nonlinear crystals is still a long-standing challenge due to the difficulty in phase-matching dependent on refractive dispersion relationship ruled by Lorentz model. Herein, we originally introduced the chirp into the additional periodic phase (APP) phase-matching and realized novel phase-matching conditions with the chirped additional periodic phase (CAPP) for DUV SHG with a CAPP quartz. The unprecedented tunable DUV SHG was realized with a wavelength from 150 to 203 nm (corresponding to a photon energy of 8.26∼6.1 eV). The developed light source presents the first SHG below 165 nm and would find promising applications in modern equipment such as angle-resolved photoemission spectroscopy (ARPES), optical atomic clocks, and DUV photodissociation dynamics. This strategy breaks the limitation of the Lorentz model for SHG and would be applicable for the extreme SHG approaching the transmittance edge of the nonlinear solid media.