Abstract
We use low temperature scanning laser microscope (LTSLM) to study the Joule power distribution of superconducting (SC) terahertz (THz) modulator. The LTSLM scanning images record the SC state transformation process under different DC bias voltages. The change of THz transmission spectra can be well explained by the thermal effect in the devices observed by LTSLM. Hotspots are present in one THz modulator and the transmission spectra changes a lot after the hotspots show up. According to theoretical analysis, the appearance of hotspot may be helpful for improving the modulation speed. These results will be useful to understand the mechanism of SC THz modulator and design higher performance THz moduators.
Highlights
With the development of terahertz (THz) technology, a variety of THz functional devices are in great demand
We find that the scanning images experience remarkable changes with the change of bias voltage
In image (II), there are remarkable hotspots formed at the nodes which connect the two unit cells and their ∆V signal is as high as 20 μV
Summary
With the development of terahertz (THz) technology, a variety of THz functional devices are in great demand. The SC-to-normal state transition at different regions may occur at different electric bias. These factors may affect the modulation speed and modulation depth. By taking LTSLM images under different DC bias voltages, we can get localized state transition information of the SC modulator with a resolution of several micron. The LTSLM will be useful for us to evaluate the role of thermal effects in SC modulator and optimize the device design. We perform experimental study on the distribution of SC state transition in SC THz modulator under different DC bias voltages using LTSLM. The relationship between thermal effects and modulation performance is comprehensively studied based on LTSLM images and theoretical analysis
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