Synthesis of the D2O laser frequency (λ =84 μ) using a superconducting nonlinear device

Experiments are described on multiplying the frequency (7.4×10¹⁰ Hz) of a klystron and mixing the multiplied frequency with radiation of frequency 3.6×10¹² Hz from a D₂O laser. The nonlinearity of superconducting point contacts and the experimental method employed made it possible to multiply and mix at frequencies exceeding several times the ultimate frequency, and to investigate the mixing mechanism. The amplitude of the beat signal between the laser radiation and the multiplied klystron frequency was proportional to the differential resistance of the contact. Over a wide range of contact bias voltages, the frequency of the beat signal was independent of the Josephson emission frequency. No substantial difference was discovered between the nonlinear properties of the contacts at frequencies of 10¹⁰ and 3.6×10¹² Hz. It was found that superconducting point contacts enabled a considerable simplification to be made in the frequency synthesis chain of an He–Ne laser by excluding several klystrons, metal–oxide–metal diodes, and a bulky submillimeter HCN laser.