YBCO Terahertz Detectors at Room Temperature and at 77K.
Paper in proceedings, 2014
The diversity of THz detectors is as wide as the range of applications for THz waves. Requirements for the detectors vary and so do the detectors. Extremely high sensitivities (NEP<10-18 W/Hz0.5) for the cosmic microwave background and extragalactic observations can only be achieved with detectors cooled below 1K. Whereas, simplicity and robustness are required for generic THz detectors in a lab and industry. Security imaging needs THz detectors in large arrays, preferably at ambient temperature operation or with compact and lightweight cooling. Until recently, such characteristics as good sensitivity (NEP<1 nW/Hz0.5), high speed (<1ms), potential for integration in arrays (solid state technology), room temperature operation have been demonstrated only with Schottky barrier diodes. Si FET detectors have also shown a good performance below 1THz. Application of YBa2Cu3O7-x, (YBCO) thin films for THz wave detection both direct and heterodyne has been discussed back to 1990s. Cooled to 77K (or so) both bolometers and Josephson junctions have shown prospect to develop in this field.
In this contribution we will discuss recent results and prospects for performance improvement and applications for YBCO nano-bolometers. Interestingly, we will consider YBCO nano-bolometers both at 77K and at room temperature. The later has been demonstrated very recently as a very prospective direction for THz detectors with sensitivity close to the Schottky diodes (<1THz) and exceeding that for frequencies above 1THz .
In our previous work we demonstrated [2,3] that with a micrometer scale bolometers based on YBa2Cu3O7-x, (YBCO) thin films, an NEP of 200 pW/Hz0.5 is achievable at room temperature, with a response rate as short as a few nanoseconds (2-5ns). Recently, we obtained YBCO nano bolometers as small as 300nm. It has led to a large increase in the responsivity (>200V/W) for frequencies from 100GHz to 2THz and a drop of NEP to about 70 pW/Hz0.5. As the responsivity grows, the nano bolometers become more sensitive to the external electrical disturbances, as well as to the internal 1/f noise. We will discuss the noise properties of the YBCO nano bolometers, their optical characterization, as well as some of their application for the gas spectroscopy and prospects of the array integration.
high speed THz detector
room temperature bolometer