Research On On-chip Integrated Terahertz Electronically Controlled High-Speed Modulator

Terahertz(0.1-10THz)electromagnetic radiation with electronics and photonics characteristics,has shown important scientific value and broad application prospects in many fields such as communication and information engineering,biomedicine,astronomy,non-destructive testing.As key components of terahertz systems,the improvement and development of terahertz functional devices is very important to promote the application of terahertz technology.Among many terahertz functional devices,terahertz modulators have always been an important research hotspot.Especially in recent years,with the explosive growth of the amount of information and data,terahertz communication technology has shown obvious advantages in the field of wireless communication due to its rich spectrum resources and high communication rate characteristics,therefore,the terahertz modulator has attracted much attention as a key component in the system.However,the current research on terahertz modulation devices is facing technical challenges with low modulation rate,complicated structure and difficult to be integrated.Therefore,this dissertation focuses on the research of high speed terahertz modulator with compact structure and low complexity.Several on-chip terahertz modulators with different structure types are proposed.Based on theoretical analysis,simulation research and experimental test verification are completed.The research work of this dissertation has an important role in promoting the development and application of terahertz modulators.The main contents and innovations of this dissertation are showing as follows:1.aiming at the development needs of miniaturization of terahertz systems,applying ultra-thin double-sided metal gratings combined with VO2 materials,a terahertz wave amplitude manipulation mechanism based on on-chip tunable SSPPs is proposed in this dissertation.Utilizing the insulator-metal phase transition characteristics of the VO2 component,the transmission characteristics of the SSPP in the composite double-sided metal grating structure are controlled,thereby achieving the terahertz wave amplitude control.During this process,the SSPPs amplitude manipulation mechanism based on the grating structure reconstruction and the duty cycle reconstruction are proposed.The control mechanisms of the two schemes are analyzed in detail and the effects of changes in the grating structure parameters on the dispersion characteristics,group speed,and transmission characteristics of the SSPPs in the two structural forms are studied.Applying an external excitation to induce phase transition of VO2 in the composite structure,the performance of terahertz wave amplitude manipulation based on SSPPs was preliminarily verified by using of a vector network analyzer.The test results and simulation results both show that two kind of schemes can achieve a control depth of more than 10 d B in the frequency range of 0.22 THz-0.28 THz.2.aiming at the challenge that existing quasi-optical terahertz modulator is difficult to increase modulate rate,while taking into account the systems requirements with onchip and low-power consumption,a microstrip line-type on-chip terahertz amplitude modulator based on microstructure nested with HEMT is proposed.Nesting HEMT with the microstructure unit to form a composite modulation unit,which can be controlled by voltage,then applying an external voltage signal to control the modulation unit to achieve high-speed modulation of the terahertz wave transmitted on the microstrip line.Exploiting theoretical analysis and simulation research,the electromagnetic response characteristics of the modulation unit and the overall performance of the device are studied.A series of experimental samples of terahertz on-chip modulators are fabricated.Using the vector network analyzer and the external DC voltage control,the static experimental tests are completed one by one,and the detailed comparison and analysis of the resonance characteristics of the microstructure and the performance of the modulator are completed.On this basis,a 0.34 THz dynamic test system is built using the proposed modulator.The mesasurement results show that the modulators with the scheme can effectively control the terahertz wave amplitude and has a high-speed modulation capability of 20 GHz.Compared with terahertz quasi-optical modulators,which have been widely studied and reported,the modulation rate has been greatly improved.3.Aiming at the high transmission loss of the microstrip line,the terahertz transmission properties of finline and terahertz wave transmission characteristics of the finline loaded with microstructures are studied.Based on the electrical resonance response of the complementary split-ring resonator and the magnetic resonance response characteristics of the split-ring resonator,an on-chip absorber suitable for a finline transmission line is proposed.The absorption characteristics of the on-chip terahertz absorber are theoretically analyzed and simulated.The research shows that the absorption coefficient reaches 98.76% at 0.213 THz.By studying the the relationship between absorption bandwidth and the number of resonance ring pairs that have different structural parameters,an on-chip absorber formed by 6 resonance ring pairs was constructed to achieve bandwidth expansion.The experimental test shows that the finline transmission line has a small insertion loss in the terahertz frequency band,and the absorption coefficient of a single complementary resonance ring pair reaches 74.68%;the test results of the absorber with six complementary resonance ring pairs show that the absorption coefficient can reach more than 90% within the bandwidth of 10 GHz,which indicates that the working bandwidth of the absorber can be effectively expanded by increasing the number of resonance ring pairs.4.An on-chip terahertz wave modulator based on the finline and dynamic microstructure assisted with diode is proposed.In this modulator,applying the microstructured resonant unit with a gallium arsenide diode to the transmission line to achieve on-chip terahertz wave amplitude dynamic modulation.The electromagnetic resonance characteristics of the dynamic microstructure and the overall performance of the modulatior are studied.Meanwhile,a reliable physical research model was established through static testing and simulation research.A 0.22 THz dynamic test link is built by using a modulator with a single diode loaded on the back microstructure.The test results show that the modulator has a high-speed modulation capability of 20 GHz and good flatness in band.A terahertz communication system based on direct modulation is constructed,and eye diagram tests and bit error rate tests are performed.Back-to-back test system results show that the modulator can achieve communication transmission of more than 10 Gbps,the bit error rate can reach 2.617e-11 at a communication rate of 10 Gbps.A terahertz wireless communication system has been built.Under the conditions of the existing experimental supporting devices,the highest rate tested at present is 4 Gbps,which proves that the device can be used in terahertz wireless communication systems.