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Softwaretechnik-Trends

Large bandwidth of NbN phonon-cooled hot-electron bolometer mixers on sapphire substrates.

Serguei Cherednichenko, Pavel A. Yagoubov, K. Ilin, Gregory N Gol'tsman, E. Gershenzon

Published Jan 1, 1997• 39 citations
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Abstract

The bandwidth of NbN phonon-cooled hot electron bolometer mixers has been systematically investigated with respect to the film thickness and film quality variation. The films, 2.5 to 10 mm thick, were fabricated on sapphire substrates using DC reactive magnetron sputtering. All devices consisted of several parallel strips, each 1 1.1 wide and 211 long, placed between Ti-Au contact pads. To measure the gain bandwidth we used two identical BWOs operating in the 120-140 GHz frequency range, one functioning as a local oscillator and the other as a signal source. The majority of the measurements were made at an ambient temperature of 4.5 K with optimal LO and DC bias. The maximum 3 dB bandwidth (about 4 GHz) was achieved for the devices made of films which were 2.5-3.5 nm thick, had a high critical temperature, and high critical current density. A theoretical analysis of bandwidth for these mixers based on the two-temperature model gives a good description of the experimental results if one assumes that the electron temperature is equal to the critical temperature.

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Large Bandwidth of NbN Phonon-Cooled Hot-Electron Bolometer Mixers

Serguei Cherednichenko, Pavel A. Yagoubov, K. Ilin +2 more

The bandwidth of NbN phonon-cooled hot electron bolometer mixers has been systematically investigated with respect to the film thickness and film quality variation. The films, 2.5 to 10 nm thick, were fabricated on sapphire substrates using DC reactive magnetron sputtering. All devices consisted of several parallel strips, each 1 μ wide and 2 μ long, placed between Ti-Au contact pads. To measure the gain bandwidth we used two identical BWOs operating in the 120-140 GHz frequency range, one functioning as a local oscillator and the other as a signal source. The majority of the measurements were made at an ambient temperature of 4.2 K with optimal LO and DC bias. The maximum 3 dB bandwidth (about 4 GHz) was achieved for the devices made of films which were 2.5-3.5 nm thick, had a high critical temperature, and high critical current density. A theoretical analysis of bandwidth for these mixers based on the two-temperature model gives a good description of the experimental results if one assumes that the electron temperature is equal to the critical temperature.

European Microwave Conference (EuMC)•Sep 1, 1997•25 citations

Comparative Study of the Bandwidth of Phonon-Cooled NbN Hot-Electron Bolometers in Submillimeter and Optical Wavelength Ranges

K. Ilin, Serguei Cherednichenko, Gregory N Gol'tsman +2 more

We report the results of the bandwidth measurements of NbN hot-electron bolometers, perfomied in the terahertz frequency domain at 140 GHz and 660 GHz and in time domain in the optical range at the wavelength of 395 nm.. Our studies were done on 3.5-nm-thick NbN films evaporated on sapphire substrates and patterned into ilin-size microbridges. In order to measure the gain bandwidth, we used two identical BWOs (140 or 660 GHz), one functioning as a local oscillator and the other as a signal source. The bandwidth we achieved was 3.5-4 GHz at 4.2 K with the optimal LO and DC biases. Time-domain measurements with a resolution below 300 fs were performed using an electro-optic sampling system, in the temperature range between 4.2 K to 9 K at various values of the bias current and optical power. The obtained response time of the NbN hot-electron bolometer to —100fs-wide Ti:sapphire laser pulses was about 27 ps, what corresponds to the 5.9 GHz gain bandwidth. Introduction The bandwidth of hot-electron bolometer (HEB) mixers has reached values which are record for bolometers. The gain bandwidth for phonon-cooled NbN HEB mixers of 4 GHz for 140 GHz and 650 GHz frequencies [1, 2] and the noise bandwidth of 8 GHz for 650 GHz [2] have been demonstrated. For diffusion-cooled Nb HEB mixers, the bandwidth has reached 6 GHz, when measured at 20--40 GHz [3]. However, there is a definite practical interest to even further extend the bandwidth of these devices. The possibilities of the HEB mixer technology in this direction are far from being exhausted. For example, the future of the NbN HEB technology requires that critical temperature Tc > 10 K and critical current density j c > 10 6 Akm at 4.2 K are simultaneously obtained for d < 3 nm-thick films M. The reduction of the optimal power of the local oscillator PLID below 100 nW leads to the decrease of the device length down to L < 0.2 pm, which, in turn, should bring an additional cooling channel for hot electrons—diffusion into metal contacts and a further bandwidth extension.

Softwaretechnik-Trends•Mar 1, 1998•0 citations

Low Noise NbN Phonon-Cooled Hot-Electron Bolometer Mixers at 810 GHz

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NbN phonon-cooled superconducting hot-electron bolometric mixers with quasi-optical coupling were fabricated in a self-aligned process by means of e-beam-lithography. The mixer element consists of a 5 nm thick NbN film sputtered on a fused quartz substrate. Noise performance was investigated in the frequency range of 798 to 813 GHz for intermediate frequencies from 1.0 to 1.75 GHz. Uncorrected double sideband receiver noise temperatures of about 900 K were measured at an intermediate frequency of 1000 MHz with a 50 MHz bandpass filter. The gain bandwidth was determined by superposing two local oscillator signals and measuring the height of the discrete line at the intermediate frequency output. A 3dB-roll-off-frequency of some 1.3 GHz was obtained.

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Performance of NbN phonon-cooled hot-electron bolometric mixer at Terahertz frequencies

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The performance of a NbN based phonon-cooled Hot Electron Bolometric (HEB) quasioptical mixer is investigated in the 0.65-3.12 THz frequency range. The device is made from a 3 nm thick NbN film on high resistivity Si and integrated with a planar spiral antenna on the same substrate. The in-plane dimensions of the bolometer strip are 0.2/spl times/2 /spl mu/m. The results of the DSB noire temperature are: 1300 K at 650 GHz, 4700 K at 2.5 TBz and 10000 K at 3.12 THz. The RF bandwidth of the receiver is at least 2.5 THz. The amount of LO power absorbed in the bolometer is about 100 nW. The mixer is linear to within 1 dB compression up to the signal level 10 dB below that of the LO. The intrinsic single sideband conversion gain is measured to be -9 dB, the total conversion gain -14 dB.

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Michael Frommberger, Philippe Sabon, Matthias Schicke +2 more

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Heterodyne measurements of a NbN superconducting hot electron mixer at terahertz frequencies

Pavel A. Yagoubov, M. Kroug, H. Merkel +6 more

The performance of a NbN based phonon-cooled Hot Electron Bolometric (HEB) quasioptical mixer is investigated in the 0.65-3.12 THz frequency range. The device is made from a 3 nm thick NbN film on high resistivity Si and integrated with a planar spiral antenna on the same substrate. The in-plane dimensions of the bolometer strip are 0.2/spl times/2 /spl mu/m. The best results of the DSB noise temperature at 1.5 GHz IF frequency obtained with one device are: 1300 K at 650 GHz, 4700 K at 2.5 THz and 10000 K at 3.12 THz. The measurements were performed at 4.5 K ambient temperature. The amount of local oscillator (LO) power absorbed in the bolometer is about 100 nW. The mixer is linear to within 1 dB compression up to the signal level 10 dB below that of the LO. The intrinsic single sideband conversion gain measured at 650 GHz is -9 dB, the total conversion gain is -14 dB.

IEEE Transactions on Applied Superconductivity•Jun 1, 1999•6 citations
The bandwidth of NbN phonon-cooled hot electron bolometer mixers has been systematically investigated with respect to the film thickness and film quality variation. The films, 2.5 to 10 mm thick, were fabricated on sapphire substrates using DC reactive magnetron sputtering. All devices consisted of several parallel strips, each 1 1.1 wide and 211 long, placed between Ti-Au contact pads. To measure the gain bandwidth we used two identical BWOs operating in the 120-140 GHz frequency range, one functioning as a local oscillator and the other as a signal source. The majority of the measurements were made at an ambient temperature of 4.5 K with optimal LO and DC bias. The maximum 3 dB bandwidth (about 4 GHz) was achieved for the devices made of films which were 2.5-3.5 nm thick, had a high critical temperature, and high critical current density. A theoretical analysis of bandwidth for these mixers based on the two-temperature model gives a good description of the experimental results if one assumes that the electron temperature is equal to the critical temperature.
The bandwidth of NbN phonon-cooled hot electron bolometer mixers has been systematically investigated with respect to the film thickness and film quality variation. The films, 2.5 to 10 nm thick, were fabricated on sapphire substrates using DC reactive magnetron sputtering. All devices consisted of several parallel strips, each 1 μ wide and 2 μ long, placed between Ti-Au contact pads. To measure the gain bandwidth we used two identical BWOs operating in the 120-140 GHz frequency range, one functioning as a local oscillator and the other as a signal source. The majority of the measurements were made at an ambient temperature of 4.2 K with optimal LO and DC bias. The maximum 3 dB bandwidth (about 4 GHz) was achieved for the devices made of films which were 2.5-3.5 nm thick, had a high critical temperature, and high critical current density. A theoretical analysis of bandwidth for these mixers based on the two-temperature model gives a good description of the experimental results if one assumes that the electron temperature is equal to the critical temperature.
We report the results of the bandwidth measurements of NbN hot-electron bolometers, perfomied in the terahertz frequency domain at 140 GHz and 660 GHz and in time domain in the optical range at the wavelength of 395 nm.. Our studies were done on 3.5-nm-thick NbN films evaporated on sapphire substrates and patterned into ilin-size microbridges. In order to measure the gain bandwidth, we used two identical BWOs (140 or 660 GHz), one functioning as a local oscillator and the other as a signal source. The bandwidth we achieved was 3.5-4 GHz at 4.2 K with the optimal LO and DC biases. Time-domain measurements with a resolution below 300 fs were performed using an electro-optic sampling system, in the temperature range between 4.2 K to 9 K at various values of the bias current and optical power. The obtained response time of the NbN hot-electron bolometer to —100fs-wide Ti:sapphire laser pulses was about 27 ps, what corresponds to the 5.9 GHz gain bandwidth. Introduction The bandwidth of hot-electron bolometer (HEB) mixers has reached values which are record for bolometers. The gain bandwidth for phonon-cooled NbN HEB mixers of 4 GHz for 140 GHz and 650 GHz frequencies [1, 2] and the noise bandwidth of 8 GHz for 650 GHz [2] have been demonstrated. For diffusion-cooled Nb HEB mixers, the bandwidth has reached 6 GHz, when measured at 20--40 GHz [3]. However, there is a definite practical interest to even further extend the bandwidth of these devices. The possibilities of the HEB mixer technology in this direction are far from being exhausted. For example, the future of the NbN HEB technology requires that critical temperature Tc > 10 K and critical current density j c > 10 6 Akm at 4.2 K are simultaneously obtained for d < 3 nm-thick films M. The reduction of the optimal power of the local oscillator PLID below 100 nW leads to the decrease of the device length down to L < 0.2 pm, which, in turn, should bring an additional cooling channel for hot electrons—diffusion into metal contacts and a further bandwidth extension.
NbN phonon-cooled superconducting hot-electron bolometric mixers with quasi-optical coupling were fabricated in a self-aligned process by means of e-beam-lithography. The mixer element consists of a 5 nm thick NbN film sputtered on a fused quartz substrate. Noise performance was investigated in the frequency range of 798 to 813 GHz for intermediate frequencies from 1.0 to 1.75 GHz. Uncorrected double sideband receiver noise temperatures of about 900 K were measured at an intermediate frequency of 1000 MHz with a 50 MHz bandpass filter. The gain bandwidth was determined by superposing two local oscillator signals and measuring the height of the discrete line at the intermediate frequency output. A 3dB-roll-off-frequency of some 1.3 GHz was obtained.
The performance of a NbN based phonon-cooled Hot Electron Bolometric (HEB) quasioptical mixer is investigated in the 0.65-3.12 THz frequency range. The device is made from a 3 nm thick NbN film on high resistivity Si and integrated with a planar spiral antenna on the same substrate. The in-plane dimensions of the bolometer strip are 0.2/spl times/2 /spl mu/m. The results of the DSB noire temperature are: 1300 K at 650 GHz, 4700 K at 2.5 TBz and 10000 K at 3.12 THz. The RF bandwidth of the receiver is at least 2.5 THz. The amount of LO power absorbed in the bolometer is about 100 nW. The mixer is linear to within 1 dB compression up to the signal level 10 dB below that of the LO. The intrinsic single sideband conversion gain is measured to be -9 dB, the total conversion gain -14 dB.
The performance of a NbN based phonon-cooled Hot Electron Bolometric (HEB) quasioptical mixer is investigated in the 0.65-3.12 THz frequency range. The device is made from a 3 nm thick NbN film on high resistivity Si and integrated with a planar spiral antenna on the same substrate. The in-plane dimensions of the bolometer strip are 0.2/spl times/2 /spl mu/m. The best results of the DSB noise temperature at 1.5 GHz IF frequency obtained with one device are: 1300 K at 650 GHz, 4700 K at 2.5 THz and 10000 K at 3.12 THz. The measurements were performed at 4.5 K ambient temperature. The amount of local oscillator (LO) power absorbed in the bolometer is about 100 nW. The mixer is linear to within 1 dB compression up to the signal level 10 dB below that of the LO. The intrinsic single sideband conversion gain measured at 650 GHz is -9 dB, the total conversion gain is -14 dB.