Superconducting Coplanar Waveguide Filters for Submillimeter Wave On-Chip Filterbank Spectrometers

We show the first experimental results which prove that superconducting NbTiN coplanar–waveguide resonators can achieve a loaded Q factor in excess of 800 in the 350 GHz band. These resonators can be used as narrow band pass filters for on-chip filter bank spectrometers for astronomy. Moreover, the low-loss coplanar waveguide technology provides...

The non-equilibrium response of a superconductor to pair-breaking radiation measured over a broad frequency band

We have measured the absorption of terahertz radiation in a BCS superconductor over a broad range of frequencies from 200 GHz to 1.1 THz, using a broadband antenna-lens system and a tantalum microwave resonator. From low frequencies, the response of the resonator rises rapidly to a maximum at the gap edge of the superconductor. From there on,...

The ALMA Band 9 receiver: Design, construction, characterization, and first light

Aims. We describe the design, construction, and characterization of the Band 9 heterodyne receivers (600–720 GHz) for the Atacama Large Millimeter/submillimeter Array (ALMA). First-light Band 9 data, obtained during ALMA commissioning and science verification phases, are presented as well. Methods. The ALMA Band 9 receiver units (so-called ...

High optical efficiency and photon noise limited sensitivity of microwave kinetic inductance detectors using phase readout

We demonstrate photon noise limited performance in both phase and amplitude readout in microwave kinetic inductance detectors (MKIDs) consisting of NbTiN and Al, down to 100 fW of optical power. We simulate the far field beam pattern of the lens-antenna system used to couple radiation into the MKID and derive an aperture efficiency of 75%. This...

On-chip filter bank spectroscopy at 600–700?GHz using NbTiN superconducting resonators

We experimentally demonstrate the principle of an on-chip submillimeter wave filter bank spectrometer, using superconducting microresonators as narrow band-separation filters. The filters are made of NbTiN/SiNx/NbTiN microstrip line resonators, which have a resonance frequency in the range of 614-685?GHz, two orders of magnitude higher in...

Design of an integrated filterbank for DESHIMA: On-chip submillimeter imaging spectrograph based on superconducting resonators

An integrated filterbank (IFB) in combination with microwave kinetic inductance detectors (MKIDs), both based on superconducting resonators, could be used to make broadband submillimeter imaging spectrographs that are compact and flexible. In order to investigate the possibility of adopting an IFB configuration for DESHIMA (Delft SRON High...

Magnetic field dependence of the coupling efficiency of a superconducting transmission line due to the proximity effect

The coupling efficiency of a Nb superconducting transmission line has been measured using a Fourier transform spectrometer for different magnetic fields. It is found that the coupling decreases with increasing magnetic field when the frequency is close to the gap of the Nb superconductor. This is attributed to the changes of the surface...

Phase locking of a 2.7 THz quantum cascade laser to a microwave reference

We demonstrate the phase locking of a 2.7 THz metal–metal waveguide quantum cascade laser (QCL) to an external microwave signal. The reference is the 15th harmonic, generated by a semiconductor superlattice nonlinear device, of a signal at 182 GHz, which itself is generated by a multiplier chain (x12) from a microwave synthesizer at ~15 GHz....

Bandwidth Limitations of Nb/AlN/Nb SIS Mixers Around 700 GHz

We study, using niobium-technology, the bandwidth of SIS mixers operating at frequencies close to the energy-gap frequency. Microstriplines of niobium-silicon dioxide-niobium have different properties for the top and bottom superconductor, which we find to depend on the used fabrication process. Replacing the AlOx tunnel barrier by AlN, the...

An SIS-based sideband-separating heterodyne mixer optimized for the 600 to 720 GHz band

IF impedance and mixer gain of NbN hot electron bolometers

The intermediate frequency (IF) characteristics, the frequency dependent IF impedance, and the mixer conversion gain of a small area hot electron bolometer (HEB) have been measured and modeled. The device used is a twin slot antenna coupled NbN HEB mixer with a bridge area of 1×0.15??m2, and a critical temperature of 8.3?K. In the experiment the...

Influence of the direct response on the heterodyne sensitivity of hot electron bolometer mixers

We present a detailed experimental study of the direct detection effect in a small volume (0.15??m×1??m×3.5?nm) quasioptical NbN phonon cooled hot electron bolometer mixer at 673?GHz. We find that the small signal noise temperature, relevant for an astronomical observation, is 20% lower than the noise temperature obtained using 300 and 77?K...

Full characterization and analysis of a terahertz heterodyne receiver based on a NbN hot electron bolometer

We present a complete experimental characterization of a quasioptical twin-slot antenna coupled small area (1.0×0.15??m2) NbN hot electron bolometer (HEB) mixer compatible with currently available solid state tunable local oscillator (LO) sources. The required LO power absorbed in the HEB is analyzed in detail and equals only 25?nW. Due to the...

Stability of heterodyne terahertz receivers

In this paper we discuss the stability of heterodyne terahertz receivers based on small volume NbN phonon cooled hot electron bolometers (HEBs). The stability of these receivers can be broken down in two parts: the intrinsic stability of the HEB mixer and the stability of the local oscillator (LO) signal injection scheme. Measurements show that...

CHAMP+: A powerful array receiver for APEX

CHAMP+, a dual-color 2 × 7 element heterodyne array for operation in the 450 ?m and 350 ?m atmospheric windows is under development. The instrument, which is currently undergoing final evaluation in the laboratories, will be deployed for commissioning at the APEX telescope in August this year. With its state-of-the-art SIS detectors and wide...

Terahertz heterodyne receiver based on a quantum cascade laser and a superconducting bolometer

We report the first demonstration of an all solid-state heterodyne receiver that can be used for high-resolution spectroscopy above 2?THz suitable for space-based observatories. The receiver uses a NbN superconducting hot-electron bolometer as mixer and a quantum cascade laser operating at 2.8?THz as local oscillator. We measure a double...

Direct detection effect in small volume hot electron bolometer mixers

We measure the direct detection effect in a small volume (0.15??m×1??m×3.5?nm) quasioptical NbN phonon cooled hot electron bolometer mixer at 1.6?THz. We find that the small signal sensitivity of the receiver is underestimated by 35% due to the direct detection effect and that the optimal operating point is shifted to higher bias voltages when...