  Bound states in the continuum (BICs) have attracted significant interest in
recent years due to their unique optical properties, such as infinite quality
factor and wave localization. In order to improve the optical performance of
BICs based devices, more degrees of freedom are required to tune BICs in
high-dimension parameter space for practical applications. To effectively tune
more BICs, we form a 2D synthetic parameter space based on a nanohole
metasurface array. Multiple symmetry protected BIC modes with high Q factors
can be achieved at high-order symmetry point. Through manipulating asymmetry
parameters, BIC lines formed by a series of BIC modes can be found in the 2D
synthetic parameter space. Moreover, the electric field distributions are
investigated to demonstrate the generation and evolution of BICs. By measuring
the absorption spectra, the tuning of multiple BICs with synthet-ic asymmetry
parameters is experimentally explored, which agrees well with theoretical
results. Therefore, our de-sign can provide new insight for a variety of
on-chip applications, such as non-linear devices, integrated nanolasing array
and high-resolution sensors for infrared molecular detection.
