Employing a Twin-Slot Quasi-Optical Mixer

**Last Updated May 5, 2001 by Jacob W. Kooi
**

"Low Loss NbTiN Films for THz SIS Mixer Tuning Circuits" ,

J. Zmuidzinas, ** J. W. Kooi, **, J. Kawamura, G. Chattopadhyay, B. Bumble, H. G. LeDuc, and J. A. Stern,

"Development of SIS mixers for 1 THz",

Proc. SPIE, vol. 3357, pp. 53-61

J.A. Stern, B. Bumble, H.G. LeDuc, **J.W. Kooi**, J. Zmuidzinas,

"Fabrication and DC-Characterization of NbTiN Based SIS Mixers for the Use betwen 600 and 1200 GHz".

**Calculated Losses for microstrip thin-film transmission line at 4.2 K.
**

The microstrip width is 5um and the SiO dielectric (Er=5.6) is
400 nm

**July 1997 mask with a full 2-Dimensional calculation of a NbTiN/MgO/NbTiN junction.**

The first number is the design frequency, the number in
parenthesisis the actual 2_D simulated frequency.

**July 1997 mask with a full 2-Dimensional calculation of a Nb/AlOx/Nbjunction.**

The first number is the design frequency, the number in
parenthesis is the actual 2_D simulated frequency.

**Below we present a full 2-Dimensional calculation with an E-beam
NbTiN/MgO/NbTiN 0.2um x 3.6um junction. **

From the above it is quite aparent that a square 0.8um x 0.8um
junction is far from optimal.

(Same size junction as in the above
simulations).

Note the tremendous improvement in coupling efficiency and center
frequency, even at 1200 GHz!

**NbTiN Groundplane, Nb Wiring, Nb/AlOx/Nb Junction, Batch-L970218 **

**NbTiN Groundplane and Wiring, Nb/AlOx/Nb Junction, Batch-970312**

**All NbTiN Device, MgO barrier. Batch-L970318**

**All NbTiN Device, MgO barrier. Batch-L970701**

**All NbTiN Wiring and Ground plane, NbTiN/AlN/Nb
junction. Batch-L970811**

**NbTiN Wiring and Ground plane(with a 1nm Nb layer), Nb/AlN/Nb junction. Batch-J970826**

resulting in a 13dB mixer conversion loss and 790K noise-temperature. (note Vgap=3.5 mV)

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