High Temperature Superconductor Terahertz Emitters: Fundamental Physics and Its Applications

Abstract

Coherent and continuous radiation sources of the electromagnetic (EM) waves at terahertz (1 THz = 10 12 c/s) frequencies using a mesa structure fabricated from high temperature superconducting Bi 2 Sr 2 CaCu 2 O 8þ single crystals are described with a special emphasis on the physics of the radiation mechanism and the applications. After the intensive studies of many mesas fabricated with different conditions, it is revealed that the ac-Josephson effect works as a primary driving mechanism of the radiation and the cavity resonance needed for stronger radiation plays an additional role to the mechanism, although both are working together while radiating. A prototype of the imaging machine for multipurpose uses has successfully been developed. #

Local SiC photoluminescence evidence of hot spot formation and sub-THz coherent emission from a rectangularBi2Sr2CaCu2O8Minami1, Watanabe2, Sato3 et al. 2014Phys. Rev. BSelf Cite668501View full textAdd to dashboardCite

“…Based on their observations that the sub-THz emission can occur even with such a highly nonuniform T (r) variation containing a local hot spot with T (r) > T c in the higher I bias regime of the IVCs, these authors suggested that the hot spot formation may be beneficial to the synchronization of the N IJJs, an essential ingredient for obtaining intense sub-THz radiation. Numerical simulations of a hot spot [29], the fact that the c-axis resistance R c (T ) can be shunted by the hot spot due to T regions of negative differential resistivity, dρ c (T )/dT < 0 [5,29], the much narrower linewidth of 23 MHz in the high-I bias hot spot region than in the retrapping, low-I bias regime [30,31], and the lack of radiation from mesas with thicker Au electrodes [32] all tend to support their hypothesis that the hot spots play an essential role in the synchronization of the IJJs.…”

“…In rectangular mesas, the standing waves observed either by LTSLM or by rare-earth embedded polymer films formed along the mesa's length [6][7][8][9], although usually the observed f = f cav = c 0 /(2nw) [33], by excitation of the TM(1,0) thin rectangular EM cavity mode, where w is the mesa width both in the high-I bias reversible (R-type) region and in the low-I bias retrapping irreversible (IR-type) region, regardless of hot spot formation [19,20,[25][26][27][28]31,34]. Unfortunately, angular distribution experiments in the planes normal to the length and width of the rectangular mesa could not distinguish the difference between those associated standing wave models [35].…”

Three-Dimensional Simulations of the Electrothermal and Terahertz Emission Properties ofBi2Sr2CaCu2Rudau1, Wieland2, Langer3 et al. 2016Phys. Rev. Applied290270View full textAdd to dashboardCite

“…IJJ stacks, containing 500 -2000 junctions, have been patterned as mesas but also as bare IJJ stacks contacted by Au layers (GBG structures) 16,17,20,24 and as all-superconducting structures 11 . Emission frequencies range from 0.3 to 2.4 THz.…”

Reflection type of terahertz imaging system using a high-Tc superconducting oscillator

“…7,8 The radiation frequency can be tuned in a frequency range between 0.3 and 1.0 THz. 7,9 The characteristic properties of the superconducting THz emitter have been studied by many researchers. [10][11][12][13][14][15][16][17][18][19][20][21][22] In our previous study, 23 we proposed a transmission type of imaging system for application purpose using superconducting THz emitter, where the higher power THz emission is more desirable.…”

“…Figure 2(a) shows current-voltage (I-V) characteristics of the IJJ-THz emitter used for the present experiment at the bath temperature of 45 K. The dimensions of the mesa device are 80 Â 400 Â 2.4 lm 3 fabricated by the Ar ion milling technique with a metallic mask. 9 The sub-THz wave radiation with a monochromatic frequency of 440 GHz was estimated by using interference pattern technique developed previously 23 at the bias point of I ¼ 60 mA and V ¼ 1.61 V as shown by the dotted line in Fig. 2.…”