Generation of circularly polarized high-order harmonics in solids driven by single-color infrared pulses

Strong-field polarization-state control of higher harmonics generated in crystalline solids

“…2(a)) with alternating helicities (not shown here), as determined by using a QWP and measuring the linear polarization angle. This is consistent with the selection rules for cubic crystals [8,9,11,12]. In a trigonal crystal like quartz, we observe circular HH4 and HH5 with alternating helicites, and a strong intensity suppression of HH3 going from linear to circular driver, which is also compatible with the selection rules.…”

“…1 |ε HH | of HH5, HH7, and HH9, determined by rotating a Rochon polarizer. The harmonic ellipticities follow the driving ellipticity for ε = 0 and |ε| = 1, as expected from spin angular momentum conservation [8,9,11,12]. For |ε| = 1, we find that all harmonics are circularly polarized (Fig.…”

“…The asymmetric, non-Gaussian-shaped ellipticity profiles are in strong contrast to the ellipticity dependence in gas-phase HHG. Later works reported the generation of circularly polarized harmonics from single-color driver pulses [8,9]. To understand this peculiar behavior, we recently introduced an ab-initio time-dependent densityfunctional theory (TDDFT) framework that allows us to investigate the complex interplay between the coupled intraand interband dynamics giving rise to HHG without making a-priori assumptions [10], and we theoretically investigated the ellipticity dependence of the HHG yield in Si and MgO [11].…”

“…To understand this peculiar behavior, we recently introduced an ab-initio time-dependent densityfunctional theory (TDDFT) framework that allows us to investigate the complex interplay between the coupled intraand interband dynamics giving rise to HHG without making a-priori assumptions [10], and we theoretically investigated the ellipticity dependence of the HHG yield in Si and MgO [11]. Here, we show that the polarization states of higher harmonics emitted from crystalline Si and quartz samples are determined by both crystal symmetry [8,9,[11][12][13] and nonperturbative dynamics [11], opening the door to strong-field control of the harmonics' polarization states.We irradiated free-standing, 2-µm-thin, (100)-cut crystalline silicon samples with 120-fs, 2.1-µm pulses from a Ti:sapphire-pumped OPA with a maximum peak intensity of 0.7 TW cm −2 (in vacuum). The driver pulse ellipticity ε was varied from ε = 0 (linear) to |ε| = 1 (circular) using a combination of quarter-wave plate (QWP) and half-wave plate (HWP) to keep the major axis of the polarization ellipse constant.…”

“…To understand this peculiar behavior, we recently introduced an ab-initio time-dependent densityfunctional theory (TDDFT) framework that allows us to investigate the complex interplay between the coupled intraand interband dynamics giving rise to HHG without making a-priori assumptions [10], and we theoretically investigated the ellipticity dependence of the HHG yield in Si and MgO [11]. Here, we show that the polarization states of higher harmonics emitted from crystalline Si and quartz samples are determined by both crystal symmetry [8,9,[11][12][13] and nonperturbative dynamics [11], opening the door to strong-field control of the harmonics' polarization states.…”