Detection Of Microwave Radiation Research Articles

Studies on DC transport and terahertz conductivity of granular molybdenum thin films for microwave radiation detector applications

The morphological, transport, and terahertz optical properties of DC magnetron-sputtered granular molybdenum thin films with nano-grains embedded in an amorphous molybdenum/molybdenum oxide matrix have been studied in their normal and superconducting states. The superconducting transition temperatures of these films are much higher than that of bulk molybdenum. The optical properties of these thin films have been studied using terahertz time-domain spectroscopy. Their properties have been compared with those of the existing materials used for the development of radiation detectors. The films' resistivity lies in the >100 μΩ cm range, ideal for making highly sensitive radiation detectors. Hall measurements indicate holes as the dominant carriers with very small mean free path and mobility. In the normal state, the films are disordered bad metals. However, they have a large superfluid density and stiffness in their superconducting state. The properties of the films in the normal and superconducting states are promising for their use in cryogenic radiation detectors for microwave, terahertz, and far-infrared frequency ranges.

Microwave Radiation Detection with an Ultrathin Free-Standing Superconducting Niobium Nanohelix.

We present a superconducting bolometer fabricated by a rolled-up technology that allows one to combine the two-dimensionality (2D) of the superconducting layer with a helical spiral curvature. The bolometer is formed as a free-standing Nb nanohelix acting as an ultrathin transition-edge sensor (TES) and having a negligible thermal contact to the substrate. We demonstrate the functionality of the thin-film TES by examining its microwave-detection performance in comparison with a commercial cryogenic bolometer from QMC Instruments. The nanohelix has been revealed to feature a noise equivalent power (NEP) of about 2 × 10-10 W Hz-1/2 at a microwave radiation power of 9 W m-2, which is 4 orders of magnitude smaller than the NEP of the QMC sensor at a similar radiation power. Furthermore, the forecast for the nanohelix is a 1 to 2 orders of magnitude shorter response time as compared to sensors based on commonly used 1 μm thick Si3N4 membranes. The reason is the extremely low heat capacity of the 50 nm thick supporting material and the few contact points between the TES and the substrate. Our findings indicate that microwave radiation detection can be substantially improved by extending 2D superconducting structures into the 3D space.

Ultrathin Flexible Carbon Fiber Reinforced Hierarchical Metastructure for Broadband Microwave Absorption with Nano Lossy Composite and Multiscale Optimization.

The implementation of thin structure for broadband microwave absorption is challenging due to the requirement of impedance match across several frequency bands and poor mechanical properties. Herein, we demonstrate a carbon fiber (CF) reinforced flexible thin hierarchical metastructure (HM) composed of lossy materials including carbonyl iron (CI), multiwall carbon nanotube (MWCNT), and silicone rubber (SR) with thickness of 5 mm and optimal concentration selected from 12 formulas. Optimization for the periodical unit size is applied, and impacts of structural sizes on absorption performance are also investigated. An effective process combining the vacuum bag method and the hand lay-up technique is used to fabricate the HM. Experimental reflectivity of the absorber achieves broadband absorption below -10 dB in 2-4 GHz and 8-40 GHz. The full band in 2-40 GHz is covered below -8 dB. Yielding stress of the HM is increased to 24 MPa with attachment of CF, while the fracture strain of the composite reaches 550%. The soft HM is suitable to adhere to the curved surface of objects needed to be protected from microwave radiation detection and electromagnetic interference. Enhanced mechanical properties make it possible for further practical applications under harsh service environments such as the ocean and machines with constant vibration.

After-effect induced by microwave radiation in human electroencephalographic signal: a feasibility study

Purpose: This feasibility study is aimed to clarify the possibility of detection of microwave radiation (MWR)-induced event related potential (ERP) in electroencephalographic (EEG) signal.Methods: To trigger onset and offset effects in EEG, repetitive MWR stimuli were used. Four 30-channel EEG recordings on a single subject were performed, each about one month apart. The subject was exposed to 450 MHz MWR modulated at 40 Hz at the 1 g peak spatial average specific absorption rate of 0.3 W/kg. During a recording, 40 cycles of 30 s on–off MWR exposure were used. The artifact-free responses to 126 MWR-ON stimuli and 134 MWR-OFF stimuli were averaged over stimuli and channels.Results: Regarding EEG signals locked to MWR-OFF stimulus, the enhanced signal level at alpha frequency band and about twice higher signal to noise ratio at 200 to 440 ms after the stimulus have been detected. No remarkable response in EEG signals locked to MWR-ON stimulus.Conclusions: The detection of offset effect confirms that there should be an imprint generated by MWR in brain. The results of this preliminary study provide evidence for the detection of MWR-induced ERP in EEG signal and encourage further research in this direction.

Investigation of the I – V characteristics asymmetry in semiconducting Y–Ba–Cu–O diodes

Thin films of YBa2Cu3O7–x (YBCO) oxygen-deficient superconductor were used to manufacture asymmetric microdiodes and investigate their asymmetric non-linear current–voltage (I –V) dependences at temperatures T > Tc, where Tc is the temperature of the onset of superconductivity in the material. The diodes are based on being asymmetrically narrowed down to a 10-μm-wide–neck mesa exhibit voltage asymmetry depending on the current bias conditions, the mesa's temperature, and a residual oxygen content in its neck region. The intrinsic electric field in the biased diode causes free-carrier drift velocity saturation, initiated in the mesa's neck and following its asymmetric enlarging towards the mesa's electrodes depending on the biasing pulsed current amplitude, polarity, and rise time/fall time of the pulse's leading/trailing edges. The variation of the I –V characteristics asymmetry has been associated with change in the mesa's electric resistivity, affected by the electric field's asymmetric distribution in the YBCO mesa. It has been also demonstrated that our asymmetric diodes with the reduced oxygen content are sensitive detectors of microwave radiation.

SENSITIVITY IMPROVEMENT IN POROUS SILICON MICROWAVE DETECTOR

Attempts to use microporous silicon structures in detection of microwave radiation were investigated. Point-contact-like samples containing microporous silicon layers were manufactured using traditional technique of electrochemical etching of p-type crystalline silicon. The response of the structures to microwave radiation of 10 GHz frequency was studied. It is shown that the microporous silicon containing samples exhibited sensitivity by several orders higher than that of similar detectors having no porous layers. The results were analysed within the model of hot carrier effects.

Sensitivity improvement in porous silicon microwave detector

Attempts to use microporous silicon structures in detection of microwave radiation were investigated. Point-contact-like samples containing microporous silicon layers were manufactured using traditional technique of electrochemical etching of p-type crystalline silicon. The response of the structures to microwave radiation of 10 GHz frequency was studied. It is shown that the microporous silicon containing samples exhibited sensitivity by several orders higher than that of similar detectors having no porous layers. The results were analysed within the model of hot carrier effects.

Switching and Hysteresis on the I-V Curves of Submicron BSCCO (2212) Bridges

In thin BSCCO (2212) whisker-based superconducting bridges with width and length ≤ 1 μm we observe random telegraph noise at discrete values of current. We show that the noise is associated with spontaneous processes of addition and removal of discrete vortex trains and reflects the regular structure of steps on the I–V curves. The average lifetime of the trains τ falls down with increasing temperature T in a complex way: intervals of steep drop (∼ an order of magnitude per Kelvin) are separated with a plateau of τ(T) with τ ∼ 10−2 s. The 70 GHz irradiation with 100 μW power results in the growth of the average switching frequency by 5 orders of magnitude; thus the HTSC bridges could be efficient detectors of microwave radiation. We discuss the peculiar features of τ(T).

Thin-Film Aluminium Microstructure as a Hot-Electron Microwave Radiation Detector

We have found that the thin film aluminum structures shaped into a chain of micron sized islands connected by narrow isthmuses, can modify their electrical and structural properties under microwave radiation. As a result, at the temperature of 4.2 K the film structures turn into a kind of lateral periodic structure N-S-N, where N is for normal islands, S is for superconducting isthmuses. Current-voltage characteristics of the samples, as well as changes of these characteristics under low power radiation, have been studied over the temperature range from 1.3 to 10 K. The sensitivity of a structure as a microwave detector runs 105 V/W.

Subharmonic locking in Josephson junctions

We have designed and tested a coplanar waveguide configuration which allows for coupling and detection of microwave radiation to planar and stacked Josephson junctions structures. The design is particularly versatile for experiments such as phase-locking of Josephson oscillations to external signals and detection of low frequency components in the waveform of a pumped junction. Using this design we have measured subharmonic phase-locking in long Josephson junctions and performed a first quantitative check of the existing theoretical models.

Detection of microwave radiation by electronic fluid in high electron mobility transistors

The authors present a microwave detector which utilises the nonlinear properties of 2D electronic fluid in a high electron mobility transistor (HEMT). The detector operates between 8 and 18 GHz and the measured responsivity is in good agreement with the recent theory of 2D electronic fluids.

The single-electron transistor as an ultrasensitive microwave detector

We have measured single-electron tunneling transistors with superconducting islands and conclude that they may be used as ultrasensitive detectors of microwave radiation for frequencies /spl ges/80 GHz. These devices contain a small superconducting Al island that is weakly coupled to a bias circuit through two small-capacitance tunnel junctions and a capacitive gate. At low bias voltages and temperatures, a single quasiparticle may only be introduced to the island through photon-assisted tunneling. Once this occurs, the quasiparticle is trapped on the island for /spl sim/1 /spl mu/s because it takes a relatively long time for this specific quasiparticle to tunnel off. While it is trapped, charge is transported through the system two electrons at a time. Since the photon-assisted transition merely switches the detector current on, this device is not limited to one electron tunneled through the system per absorbed photon. Measurements indicate that at least 100 electrons can tunnel for every absorbed photon, which corresponds to a noise-equivalent power of 3/spl times/10/sup -20/ W//spl radic/Hz at 80 GHz if the current is measured with a commercial current amplifier. >

Effect of cyclotron resonance on the microwave detection properties of a glow discharge plasma

The effect of cyclotron resonance on the detection of microwave radiation by a glow discharge tube has been investigated. This effect was reported about a decade ago for the detection of 70-GHz millimeter-wave radiation using a magnetic field of 26 kG. In the present work a similar experiment has been carried out with 9.1-GHz microwave radiation a resonance in the detection signal at a magnetic field of 3.1 kG has been found. This experiment, which involves the use of an X-band microwave source, a moderate magnetic field, and the plasma of a simple glow discharge tube, can easily be adopted in a physics student laboratory.

Antenna properties of glow-discharge detectors of microwave radiation

Investigations of X-band directionality of response by sensitive d.c. glow-discharge detectors of microwave radiation indicate no noticeable dependence on the d.c. field being parallel or perpendicular to the microwave field, thus supporting a previously developed modol of detection by the plasma. However, if the microwave frequency is such that the electrode dimension tangential to the microwave field approaches one-half the wavelength, changes in response directionality occur which appear to result possibly from diffraction and scattering by the glass envelope, resulting in mode conversion and transmission line resonance by the electrodes. Lack of noticeable antenna properties by these devices at X-band suggests the detection mechanism is based primarily in the discharge itself and that ‘ probe ’ rectification by the anode, though not excluded completely, is not too significant at X-band (⋍ 3 cm wavelength) in view of the small inter-electrode space ( 1–2 mm) of such devices. Inter-electrode distances ...

Internal signal gain in subnormal glow-discharge detection of microwave radiation†

The high response of a subnormal as compared to an abnormal glow discharge to microwave radiation is a result, of large internal amplification within the discharge composed of ionizing collisions involving signal electrons and secondary emission processes. Diffusion current losses in the cascade ionization process are analysed and are found to be significant in the subnormal glow. Rise-time limitations indicate that the positive ion signal gain cannot be neglected. Treatments involving ionization and secondary emission coefficients are amended accordingly.

Detection of microwave radiation using thin film superconducting loops containing weak links

Detection of microwave radiation using thin film superconducting loops containing weak links

Response of superconducting point contacts to high frequency radiation

The high frequency response predicted by a perturbation approach for a highly damped current driven Josephson junction agrees in its parameter dependence remarkably well with observations on point contacts used as video type detectors of microwave radiation.

Detection of Microwave Radiation from the ^{2}Π_{1/2}, J = 1/2 State of OH

Detection of Microwave Radiation from the ^{2}Π_{1/2}, J = 1/2 State of OH