【正文】 crystal substrates．Optics Letters ， ．2022．36(7):12301242．[18] 方安樂(lè)，戴小玉，凌曉輝等．太赫茲超常材料及應(yīng)用．激光與光電子進(jìn)展．2022．44(5): 051601(19)[19] Shuang Zhang， YongShik Park， Jensen Li et al．Negative index bulk Metamaterial at terahertz frenquency． Phys． Rev． Lett． 2022． 102: 023901(19)．[20] HouTong Chen， Willie J． Padilla， Joshua M． O． Zide ．Ultrafast optical switching of terahertz metamaterials fabricated on ErAs/GaAsnanoisland superlattices． Optics Express．2022．32(12): 16201622．[21] Oliver Paul， Christian Imhof， Bert L228。gel， Sandra Wolff， Jan Heinrich， Sven H246。?ing， Alfred Forchel， Remigius Zengerle， Ren233。 Beigang， Marco Rahm． Polarizationindependent active metamaterial for highfrequency　terahertz modulation．Opt．Express．2022． 17(2):819827． [22] R． Kcrsling， G． Sifiuscr， K． Unierrainer． Terahertz phase modulator． ElectronicsL Leters ．2022．36(13):11561158． [23] HouTong Chen ．Active Thz metamaterial divce．US2022/0262766 AL [24] Ranjan Singh， Evgenya Smirnova， Antoite J． Taylor et al．Optically thin terahertz metamaterials． Optics Express．2022 ．16(9):65376543．[25] HouTong Chen， Hong Lu， Abul K． Azad et al．Electronic control of extraordinary terahertz transmission throughsubwavelength metal hole arrays． Optics Express．2022．16(11):733783．致 謝 辭衷心地感謝李德華老師，在我的畢業(yè)設(shè)計(jì)完成過(guò)程中給予的指導(dǎo)和幫助，使我學(xué)到了很多專業(yè)知識(shí)，為以后的研究生學(xué)習(xí)提供了一個(gè)良好的開(kāi)端．感謝我在大學(xué)中的老師，不僅教了我專業(yè)知識(shí)，而且還教了我怎樣學(xué)習(xí)、做人做事，使我受益匪淺．同時(shí)他們?yōu)槲姨峁┝藢捤傻膶W(xué)習(xí)環(huán)境，使我有機(jī)會(huì)學(xué)習(xí)更多的知識(shí)．還要感謝在學(xué)習(xí)和生活上幫助和支持過(guò)我的同學(xué)們，是他們使我的大學(xué)過(guò)得更有意義．附 錄英文文獻(xiàn)翻譯A terahertz modulatorDaniel MittlemanTiny metal resonators can be used to create a material with tunable responses to an applied voltage． Combined with a semiconductor substrate， they can be used to control technologically promising terahertz radiation． Electromagic radiation with frequencies lying between the microwave region and the infrared — socalled terahertz radiation —holds great promise for imaging and sensing applications． It is nonionizing， and therefore causes less damage to biological tissue than conventional， higherenergy Xrays． It perates plastics and clothing， but not metal， and so is ideal for security screening and noncontact testing or inspection． But to realize the full potential of terahertz radiation， more sophisticated techniques for its generation， manipulation and detection are required． In this issue， Chen et al． (page 597) fill an important gap in our capabilities． They report the development of an efficient， electrically driven modulator for terahertz signals that functions at room temperature． This work builds on exciting developments in the field of Metamaterials． These are materials engineered to have electromagic responses that are impossible in naturally occurring materials， such as a negative refractive index． The refractive index of a material， n， is a measure of the speed of light in the material， and is given by n ， where 181。 is the material’s ???‘permeability’ to magic fields， andε its ‘permittivity’ to electric fields． All naturally occurring materials have positive 181。 transparent materials have positive ε， too． In these normal materials， therefore， the refractive index is a real and positive number．In 1968， the Soviet physicist Victor Veselago showed that a hypothetical material with negative ε and 181。 would also have a real refractive index， meaning that light waves could propagate through the material， but would behave as though its refractive index were negative． This material would have unusual and potentially valuable properties． A flat slab of negativeindex material， for example， would focus light in much the same way as a curved slab of ordinary material (a lens)， but with a smaller focal spot．Although negativeindex materials do not violate any laws of physics， the absence of a medium with negative 181。 confined the idea to the realm of speculation． But in the late 1990s， John Pendry found that， by assembling a collection of appropriately designed metallic structures， a material can be fabricated that has both negativeε and negative 181。 for incident electromagic radiation of a particular frequency． Furthermore， if the metal structures are each much smaller than the wavelength of the incident radiation， the radiation interacts with them not individually， but collectively， according to their average properties． These are the engineered materials now known as Metamaterials．Engineering a material with negative ε was easy: this equates to opacity， a property of all metals for incident radiation below a certain frequency． It was necessary to show only that a discrete set of thin metallic structures could mimic this property of the bulk metal． The more difficult task was achieving a negative 181。． It turned out that this could be done using a pair of concentric metallic rings with gaps that prevent current from circulating． Because these rings are both capacitors (they store electric charge) and inductors (they induce magic fields that selfsustain any current flowing through them)， the presence of gaps leads to a resonant response， with charge accumulating alternately on one side of the gap and then the other， sloshing back and forth through the rings rather as a mass vibrates back and forth on a spring． At frequencies near the characteristic frequency of this resonant electron flow，ε and 181。 can vary dramatically as a function of frequency． Indeed， either one can bee negative if the resonance is strong enough．The development of the splitringresonator concept was significant not only because it permits a negative refractive index， but more generally because it represents a new technique for ‘designing’ the optical response of a medium．