Coherent perfect absorption in unpatterned thin films of intrinsic semiconductor

We analyze the coherent perfect absorption (CPA) in unpatterned thin films in intrinsic semiconductor using the admittance matching method. The CPA is obtained at the phase and irradiance matching conditions. Controlling the modulation of relative input irradiances, a sharply single dip of CPA transforms to the broadband perfect absorption. The CPA parameters of admittance matching method are well agreement with the transfer matrix method. We analyze also coherently controlling the phase mechanism that is applicable for optical switching and modulation. This method provides the precision in design at visible regime. The method can enhance the design of future photonics devices for sensors and modulators.