Ultrasensitive Terahertz Hot-Electron Mixers

基金将用于开发用于外差接收器的超导热电子热辐射计（HEB）混频器，波长范围为1 mm至0.1 mm （300 GHz - 3 THz）。辐射热计混频器由一条亚微米的超导体带组成，该超导体带偏置在其电阻跃迁的中间。HEB混频器最近显示出宽中频带宽（6 GHz）和低噪声以及极低的本地振荡器功率要求（TR = 650 K DSB和PLO = 15 nW在530 GHz）。热电子的外扩散实现了快速的热响应和大的中频带宽。这种混合器没有能量间隙限制（例如，在超导SIS混合器中发现），预计可以运行到几个10太赫兹。将研究器件材料、几何形状、转变温度、转变宽度和薄片电阻，以优化与当前和即将到来的观测计划和任务直接相关的应用程序的混合器性能。在改善条件下沉积的Nb桥，以及在极低转变温度下沉积的Al和Ti桥将被测试以产生具有增强灵敏度的接收器。

Abstract PROBER, D. E. AST-9618705 Funds will be used to develop superconductive hot-electron bolometer (HEB) mixers for heterodyne receiver application in the wavelength range from 1 mm to 0.1 mm (300 GHz - 3 THz). The bolometer mixer consists of a submicron strip of superconductor biased in the middle of its resistive transition. HEB mixers have recently shown broad IF bandwidths ( 6 GHz) and low noise along with extremely low local oscillator power requirements (TR = 650 K DSB and PLO = 15 nW at 530 GHz). Rapid thermal response and hence large IF bandwidth is achieved by out-diffusion of hot electrons. This mixer has no energy gap limitation (as for example is found in superconductive SIS mixers) and is expected to operate up to several 10's of THz. Device material, geometry, transition temperature, transition width, and sheet resistance will be investigated to optimize mixer performance for applications directly related to current and upcoming observational programs and missions. Nb bridges deposited with improved conditions, and Al and Ti bridges with very low transition temperatures will be tested to produce receivers with enhanced sensitivity.