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In this study, we developed a microbolometer chip fabricated from high temperature superconducting Bi2Sr2CaCu2O8+δ (Bi2212) single crystals for the terahertz (THz) detection. For the manufacturing of the microbolometer chips, Bi2212 single crystals were transferred on substrate in the thin film like form and electron beam lithography, ion beam etching techniques were used. Resistance versus temperature behavior of the bolometer chips were performed by four probe technique in liquid nitrogen cryostat. Bi2212 microchips were integrated and characterized using in our custom-designed cryogenic bolometer system instead of expensive and massive cooling systems. The fabricated microchips significantly detected signals from the Stefan-Boltzmann lamp which includes a portion of THz radiation. The detected power and response time were studied for Bi2212 thin film like microbolometer chips. Our results demonstrated the feasibility of improved Bi2212 microchips could be used for bolometric detection for THz applications., Ministry of Science, Industry and Technology (SANTEZ 1386.STZ.2012-1)

In this study, we have investigated the spectral performance of resonant terahertz (THz) bandpass filters which were produced from thin films with a metal-mesh shape. The aforementioned filters were fabricated from titanium, copper and indium tin oxide thin films on fused silica substrates by UV lithography with an array of cross-shaped apertures. Since the mesh period, cross-arm length and its width specify the spectral characteristics of the filters, we were able to reveal the performance of these filters experimentally using both a THz time domain spectrometer and a Fourier transform infrared spectrometer. A commercial electromagnetic simulation software, CST microwave studio, was used to verify the experimental data. The transmission of the filters are in the range 20–55 % at their relevant center frequencies. To our knowledge this study is the first to show that fabricated patterns based on ITO thin films can be used to filter THz radiation., TUBITAK (114F091)

The rapid increase in applications of terahertz waves requires new techniques to obtain continuous wave terahertz sources. Mesa structures fabricated from high-Tc superconductor Bi2Sr2CaCu2O8+δ (Bi2212) single crystal have been observed as an intense, coherent, continuous electromagnetic wave source in the terahertz (THz) frequency region. However, in order to produce coherent radiation with high applicable power, we need large mesa structures that enter a collective electromagnetic state in which their oscillations are largely synchronized in phase. On the other hand, large mesa structures cause a heating problem. In this study, we report on the critical current density dependence of mesa area and the crystal inhomogeneity to understand heating problems in large area mesas for terahertz radiation. Since the doping dependence of Bi2212 is an important parameter, the as-grown Bi2212 crystals were heat-treated at various temperatures under vacuum conditions. We have fabricated triple mesa structures from Bi2212 single crystal using e-beam lithography and argon ion beam etching techniques with same area and with different area on the same chip. We investigated and compared characteristics of triple mesas which are on the same chip and next to each other. In this way, we searched the crystal inhomogeneity in triple mesa structures and studied the critical current density dependence of mesa area to obtain high emission power for the THz radiation. Our experimental results clearly show that the Josephson critical current density is decreasing when the area of mesa is increasing. © 2015 Elsevier Ltd. All rights reserved., TUBITAK (110T248); SANTEZ (1386.STZ.2012-1)

The effect of electromagnetic wave irradiation on the phase dynamics of intrinsic Josephson junctions in high temperature superconductors is investigated. We predict three novel effects by variation of the radiation amplitude and frequency: changing of the longitudinal plasma wavelength at parametric resonance; double resonance of the Josephson oscillations with radiation and longitudinal plasma wave; charging of superconducting layers in the current interval corresponding to the Shapiro step. The "bump" structure in IVC recently observed experimentally is demonstrated. We also observe ragged Shapiro steps at double resonance.

We fabricated rectangular mesa structures of superconducting Bi 2Sr 2CaCu 2O 8+d (Bi2212) using e-beam lithography and Ar ion beam etching techniques for terahertz (THz) emission. c-axis resistance versus temperature (R-T), current-voltage (I-V) characteristics and bolometric THz power measurements were performed to characterize Bi2212 mesas. The emission frequency of mesas was determined using a Michelson interferometer setup which also demonstrates polarized emission. Interference patterns of THz radiation from Bi2212 mesas were detected by various detectors such as a liquid helium cooled silicon composite bolometer, a Golay cell and a pyroelectric detector. An emitted power as high as 0.06mW was detected from Bi2212 mesas. For the first time, most of the pumped power was extracted as THz emission from a Bi2212 mesa. The radiation at 0.54THz was detected using the Michelson interferometric setup., TUBITAK (110T248); Alexander von Humboldt foundation

30th URSI General Assembly and Scientific Symposium, URSIGASS 2011; Istanbul; Turkey; 13 August 2011 through 20 August 201, Rectangular Bi2Sr2CaCu2O 8+δ (Bi2212) mesa structures were fabricated on as-grown Bi2212 single crystal superconductors using standard photolithography and Ar ion beam etching techniques. We have performed c-axis resistance versus temperature (R-T), current-voltage (I-V) characteristics and bolometer measurements. Furthermore, in contrast to previous studies, the emission frequency was determined using interferometer set up instead of FTIR. The interference patterns were detected outside the cryostat after traveling long way through ambient space. The emission frequency calculated by Fourier transform of interference data is consistent with Josephson frequency-voltage relation. © 2011 IEEE., Scientific and Technical Council of Turkey project no. 110T248

30th URSI General Assembly and Scientific Symposium, URSIGASS 2011; Istanbul; Turkey; 13 August 2011 through 20 August 2011, We work on a frequency tunable solid state device to meet the needs of continuous, coherent, powerful terahertz emission sources that fill practically important terahertz gap. High temperature superconducting (HTS) coherently oscillating Josephson junctions in Bi2Sr2CaCu 2O8+δ (Bi2212) crystal make this approach very promising. Since doping dependence of Bi2212 is an important parameter, Bi2212 crystals are annealed in vacuum or purified argon gas flow at 425°C. For further processing we pattern both single and double rectangular mesa structures by using electron beam lithography on the cleaved surface of the crystal. Resistance-temperature (R-T), and current-voltage behavior (I-V) measurements achieved. © 2011 IEEE., Scientific and Technical Council of Turkey project no. 110T248

Thesis (Master)--Izmir Institute of Technology, Physics, Izmir, 2011, Includes bibliographical references (leaves: 81-87), Text in English; Abstract: Turkish and English, xii, 87 leaves, Terahertz radiation is part of the electromagnetic spectrum lying between microwaves and the far-IR. This region has frequencies ranging from 0.1 - 10 THz and wavelengths from 3 mm to 0.03 mm. We work on a frequency tunable solid state device to meet the needs of continuous, coherent, powerful terahertz emission sources that fill practically important terahertz gap. Among the cuprates, single crystal of Bi2Sr2CaCu2O8+ (Bi2212) is a potential candidate of compact solid state devices designed for generating electromagnetic waves in terahertz frequency range. Bi2212 crystals are consisting of natural arrays in the form of identical layers called intrinsic Josephson junctions (IJJ). In this study, under optimized doping conditions we aimed to investigate powerful terahertz emission. THz emission in the μW range can be obtained fabricating rectangular-shaped mesa structures on the Bi2212 crystal. In the experimental procedure, in order to obtain various doping levels, we annealed the high temperature superconducting Bi2212 single crystals at various temperatures in vacuum or under argon flow. By using the thermal evaporation, optic and electron beam lithography, ion beam etching techniques single and double mesa structures were fabricated. For the e-beam lithography process, we optimized and improved the required parameters. After the mesa fabrication, the exact dimensions of the mesas were obtained using surface profilometer and atomic force microscope. In order to characterize the Bi2212 mesas,by three probe contact c-axis resistance versus temperature (R-T), and current-voltage behavior (I -V) were measured in a He flow cryostat. Some of the hysteretic quasiparticle branches are seen in the I-V characteristics of Bi2212 crystals.