Parallel magneticcontrolled THz modulator based on two-dimensional magnetized plasma photonic crystal

Abstract

THz waves are very good candidates for high-capacity wireless links since they offer a much higher bandwidth than RF frequencies. Photonic crystal (PC) offers a new opportunity for integrated THz wave devices. It permits the integrated devices to be miniaturized to a scale comparable to the wavelength of the electromagnetic wave. Considering their governing properties such as photonic band gap (PBG) and photon localization effect to control electromagnetic wave propagations, PC-based THz modulator has attracted much attention. Tunability strategies include mechanical control, electrical control, magneto static control, temperature control and optical pumping. However, the development of high-speed THz wireless communication system is limited by the low modulation depth and rate of previously reported modulators. In this paper, we propose a novel magnetic-controlled THz modulator based on a magnetized plasma PC consisting of line defects and a point defect. InSb, a semiconductor with high electron mobility, is introduced into the point defect. According to the magneto-optical effect, the refractive index of InSb changes rapidly under the control of the applied magnetic field (MF) intensity. Then the mode frequency in the point defect changes dynamically. The structure is based on a two-dimensional PC constructed by triangular lattice of Si rods in air. Based on the magneto-optic effect, the magnetized plasma defect mode in the THz regime can be decomposed into the left- and right-handed circularly polarized light when the applied magnetic field is parallel to the direction of the THz wave. And the difference in effective refractive index between the left- and right-handed circularly polarized light increases with the applied uniform magnetic field increasing. Therefore the on/off modulation of left- and right-hand circularly polarized light can be realized. The steady-state field intensity distribution and the time domain steady state response of TE wave propagating parallelly to the external magnetic field are simulated by the finite-difference-time-domain and finite element method. The simulation results show that PC-based mode transfer modulator has the potential application to THz wireless broadband communication system with a good performance of high contrast ratio (25.4 dB), low insertion loss (0.3 dB) and high modulation rate (～4 GHz). It is convenient to load the modulation signals in an easy MF application way. The device designed is leading the way to extend the application of THz wireless communication filed with advantages of small size, low insertion loss, and high extinction ratio.

Frequency response range of terahertz pulse coherent detection based on THz-induced time-resolved luminescence quenching

“…The luminescence intensity is directly proportional to the number of electrons in the Γ valley, which has been demonstrated in previous studies. [6,[11][12][13][14] To investigate the distributions of the electrons in the three valleys corresponding to different incident THz pulses, the Boltzmann equation is used to describe the motion of electrons in the THz field, which is studied by the ensemble Monte Carlo method [9,10,[15][16][17][18][19][20][21][22][23]…”

“…In order to enhance the performance and functionalities of the detectors for various applications, a novel theoretical THz pulse detection method was proposed in a previous study. [6] The electron transport caused by a THz pulse has aroused significant interest, [6][7][8][9][10] which is the basis of the new de-tection theory. In our earlier work, it has already been suggested that the coherent detection of THz pulses can be realized based on the THzinduced time-resolved luminescence quenching, [6] because the changes in the luminescence and THz pulse waveforms are reversed when the THz pulse irradiates the semiconductor under a direct-current (DC) voltage at room temperature.…”

Linear and nonlinear characteristics of time-resolved photoluminescence modulation by terahertz pulse

“…THz pulse based on its high-field transport and ultrafast characteristics has been applied to semiconductor modulation technology which has seen rapid development in recent years. [1][2][3][4][5][6][7][8][9][10][11][12] Especially, it is possible to study the nonlinear modulation of the carriers by THz pulse precision delay in semiconductors. For example, scholars have observed nonlinear ultrafast modulations of intense terahertz pulses in Ge, Si, GaAs, and InGaAs.…”