ABSTRACT
An advanced optical terahertz (THz) fingerprint sensor based on coherent perfect absorption (CPA) is proposed. Based on a one-dimensional layered photonic structure, the sensor contains a cavity that is developed for THz fingerprint measurement. Utilizing the magneto-optical effect of magnetized InSb, CPA is excited in the structure of the sensor. Taking α-lactose as exemplar material, this numerical simulation is integrated with a Drude-Lorentz model. The transfer matrix method (TMM) is used to calculate the sensitivity (S), linear range (LR), quality (Q), the figure of merit (FOM*), and detection limit (DL) theoretically. Employing the amplitude modulation detection method, the qualitative and quantitative analysis of the α-lactose thickness of 0-0.5 µm could be realized. Because of the fragility of CPA, the S is 0.78255 µm-1, the value of average Q is up to 8019.2, the value of average FOM* is 13 234.4 (THz µm)-1, and the lower DL is 4.21 × 10-6. Moreover, the evolutions of ensemble-averaged absorption in the vicinity of the absorption peaks for different types of disorder effects are considered, which will be considered in the fabrication of sensors.
ABSTRACT
To date there have been many studies on multi-channel absorbers for conventional photonic crystals (PCs). However, the number of absorption channels is small and uncontrollable, which cannot satisfy applications such as multispectral or quantitative narrowband selective filters. To address these issues, a tunable and controllable multi-channel time-comb absorber (TCA) based on continuous photonic time crystals (PTCs), is theoretically proposed. Compared with conventional PCs with fixed refractive index (RI), this system forms a stronger local electric field enhancement in the TCA by absorbing externally modulated energy, resulting in sharp multi-channel absorption peaks (APs). Tunability can be achieved by adjusting the RI, angle, and time period unit (T) of the PTCs. Diversified tunable methods allow the TCA to have more potential applications. In addition, changing T can adjust the number of multi-channels. More importantly, changing the primary term coefficient of n1(t) of PTC1 can control the number of time-comb absorption peaks (TCAPs) in multi-channels within a certain range, and the mathematical relationship between the coefficients and the number of multiple channels is summarized. This will have potential applications in the design of quantitative narrowband selective filters, thermal radiation detectors, optical detection instruments, etc.
