We present a scheme to produce the selected left or right elliptically polarized high-order harmonic generation. By adopting bichromatic counter-rotating colinear elliptically polarized pulses, their interaction with oxygen molecule are calculated under the framework of time-dependent density functional theory. Here we show that the helicity-selective high harmonics with tunable ellipticity are generated by changing the ellipticity of one of the pump pulses. Because of the interference of the degenerate highest occupied molecular orbitals, tunable ellipticity in a wide spectral range is obtained. This scheme can be used to synthesize attosecond pulses with controlled ellipticity and helicity.

High harmonic generation (HHG) driven by counter-rotating bicircular (CRB) pulses excitation has been observed from several solid targets, where circularly polarized harmonics are emitted. We study this process using time-dependent density functional theory (TDDFT) to calculate the crystal orientation dependence of the circularly polarized high harmonics from a monolayer h-BN. The resulted can be interpreted by the real space electron dynamics of electrons in polar chemical bonds. The yield of circularly polarized high harmonics (CHHs) can be optimized by controlling the direction of valence electron dynamics. Our findings pave the way for exploring the binding potential from spectrum and all-optically processing information.