Analysis of an integrated optical coherent receiver with optical state of polarization control

An integrated optical coherent receiver with continuous state of polarization control is proposed and analyzed. The receiver consists of an integrated optical polarization rotator, a state of polarization detector and a balanced mixer receiver. Continuous state of polarization control can be achieved by using two polarization rotators in series and feeding the polarization rotator outputs into the state of polarization detector whose subsequent output is used to control the voltage settings on the polarization rotator. For the general case, the polarization rotator is comprised of two phase shifters and a TE - TM mode converter. The state of polarization detector stage consists of a δβ directional coupler mode splitter. A novel fabrication technique for achieving efficient polarization splitting is discussed. A balanced mixer receiver is implemented using a passive directional coupler with 50/50 power splitting. The need for a passive device is demonstrated and a method for achieving accurate power splitting ratios using the proton exchange fabrication technique is discussed and experimentally demonstrated. An analysis of the performance of such a system including the balanced mixer receiver is carried out to identify the critical areas of fabrication. Discussion is also given to the function and characteristics of the electronic control loop.     

Low noise Schottky barrier diode mixers for wavelengths < 1 mm

Recent progress in realizing low noise Schottky diode mixers in the submillimetre region is reviewed. Schottky diodes built on epitaxial material must be carefully optimized through use of E-beam lithography to obtain lowest conversion loss in a particular frequency region. Satisfactory diplexing schemes exist and a number of promising mixer configurations have been developed. The principal problem is a lack of suitable tunable sources of local oscillator power.     

Development of SRAO 3MM SIS Receiver

We have developed a 3 mm band receiver for SRAO. The receiver employs an Nb-based SIS junction in the mixer and operates at 85–115 GHz with single polarization. The receiver noise temperature is 40–50 K in DSB. It is equipped with an MPI-type filter for single-side band observations. We present the design, construction, and test results for individual components of the receiver optics, heterodyne system, and cryogenics. The receiver has been installed on the 6 m SRAO telescope and tested toward astronomical sources. The beam-measurement experiment suggests that the edge taper is smaller than the designed 12 dB.     

Development of the physical principles of the design and implementation of a 500–700 GHz spectrometer with a superconducting integrated receiver

A spectrometer based on the effect of freely decaying polarization in the frequency range 500–700 GHz has been designed. Radiation sources are harmonics from a quantum semiconductor superlattice frequency multiplier. The receiving system of this spectrometer is constructed using a superconducting integrated receiver based on a superconductor-insulator-superconductor mixer and a flux-flow oscillator operating as a heterodyne oscillator. The spectrometer has been used to measure absorption lines of NH₃ in a sample of expired air (572 GHz).     

180–425 GHz low noise SIS waveguide receivers employing tuned Nb/AIOx/Nb tunnel junctions

We report recent results on a 20% reduced height 270–425 GHz SIS waveguide receiver employing a 0.49 µm² Nb/AlO _x /Nb tunnel junction. A 50% operating bandwidth is achieved by using a RF compensated junction mounted in a two-tuner reduced height waveguide mixer block. The junction uses an end-loaded tuning stub with two quarter-wave transformer sections. We demonstrate that the receiver can be tuned to give 0–2 dB of conversion gain and 50–80% quantum efficiency over parts of it's operating range. The measured instantaneous bandwidth of the receiver is 25 GHz which ensures virtually perfect double sideband mixer response. Best noise temperatures are typically obtained with a mixer conversion loss of 0.5 to 1.5 dB giving uncorrected receiver and mixer noise temperatures of 50K and 42K respectively at 300 and 400 GHz. The measured double sideband receiver noise temperature is less than 100K from 270 GHz to 425 GHz with a best value of 48K at 376 GHz, within a factor of five of the quantum limit. The 270–425 GHz receiver has a full 1 GHz IF passband and has been successfully installed at the Caltech Submillimeter Observatory in Hawaii. Preliminary tests of a similar junction design in a full height 230 GHz mixer block indicate large conversion gain and receiver noise temperatures below 50K DSB from 200–300 GHz. Best operation is again achieved with the mixer tuned for 0.5–1.5 dB conversion loss which at 258 GHz resulted in receiver and mixer noise temperature of 34K and 27K respectively.     

Submillimeter-wave receiver with a balanced monolithic mixer

We describe the design of a superheterodyne receiver with a balanced monolithic integrated mixer and describe the technique and results of parameter measurements of the receiver and mixer over the frequency range 287–365 GHz. In the middle of this range, the double-band noise temperature of the receiver is 1500±50 K, while the double-band noise temperature and conversion loss of the mixer are 1250±50 K and 10±0.5 dB, respectively. Comparison with mixers and receivers of other types is performed. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 6, pp. 573–580, February 1999.     

345 GHZ PROTOTYPE SIS MIXER WITH INTEGRATED MMIC LNA

We report on heterodyne measurements at submillimeter wavelengths using a receiver with a Superconductor-Insulator-Superconductor (SIS) mixer device and a Microwave Monolithic Integrated Circuit (MMIC) cryogenic low noise amplifier (LNA) module integrated into the same block. The mixer characterization presented in this work demonstrates the feasibility of operating a MMIC LNA in close proximity to the SIS device without penalty in mixer performance due to heating effects. Verification of this functionality is crucial for the ongoing development of SuperCam, a 64-pixel focal plane array receiver consisting of eight, 1 × 8 integrated mixer/LNA modules. The test setup included a mixer block modified to accept a MMIC amplifier. Our tests show that the LNA can be operated over a broad range of V_drain voltages from 0.40–1.40 V, corresponding to dissipative powers of 2.6–29 mW. We observe no significant effect on the measured uncorrected receiver noise temperatures in the 345 GHz band.     

A Broad-Band Low-Noise Schottky Diode Full-Height Waveguide Mixer from 80 to 115 GHz

The RF matching problem in the input circuit of the mm-wavelength whisker contacted Schottky diode mixer is studied. The experimental results, obtained on the 3mm wavelength mixer mounts in the broad band of frequencies from 80 to 115 GHz are presented. It is shown that advantage in the receiver noise temperature may be realized by the use of a full-height instead of 1/4-reduced-height waveguide because of reduction loss in the mixer input circuit even beginning from the 3mm-wavelength. With a full-height waveguide mixer the double sideband (DSB) receiver noise temperature is 300 divided by 350K over the 85 to 110 GHz band. Input bandwidth of the fullheight waveguide mixer (cap delta f _S/f _SO greater than 30%) is equal to 1/2-and close to 1/4-reduced-height waveguide mixers.     

A 275–370 GHz Receiver Employing Novel Probe Structure

We present the results of the development of a 275–370 GHz, fixed-tuned double sideband (DSB) receiver based on superconductor-insulator-superconductor (SIS) junction mixer. The mixer block uses a full height rectangular waveguide and employs a novel radial-like probe structure with integrated bias-T. The measured uncorrected receiver noise temperature is 30–50 K corresponding to about 2–3 quantum noise across the full frequency band with an IF from 3.8 to 7.6 GHz. The mixer is to be used on the Atacama Pathfinder EXperiment (APEX) submillimeter telescope in Chile.     

Noise and thermal properties of a submillimeter mixer with the SINS tunnel junction

In this work we present for the first time a low-noise submillimeter receiver with a mixer using Superconductor-Insulator-Normal metal-Superconductor (SINS) junctions. Junctions containing a normal metal layer may be free of the Josephson current and of the related perturbations of mixer operation specific for the standard SIS mixers. This SINS mixer quality is important for the application in the multibeam submillimeter receiver. The SINS mixer stability of operation and independence on the magnetic field have been confirmed in our experiment. Minimum SINS receiver noise in the 290 – 330 GHz band is about 135 K when the junction R_NC is about 30. Noise, conversion gain and thermal properties of the SINS mixer have been studied and compared with the SIS mixers. The limit of SINS mixer operation improvement is discussed at the end of the work.