Lecture Gabriel Santamaria - "Avoiding thermal noise in photonic up-converters: Can a mm-wave detector's sensitivity approach the quantum limit at room temperature?"

12.07.2018, 13:30

Universidad Carlos III de Madrid


Max Planck Institute for the Science of Light
Leuchs Division

Time and place:

1:30 p.m., July 12, 2018, Seminarroom, A.2.500, Staudtstr. 2


Room-temperature detection of mm-wave and THz radiation can be performed in the optical domain by porperly up-converting the signal with efficient electro-optic modulators made of nonlinear crystals. As the parametric up-conversion is intrinsically noiseless, the noise performance of such a receiver concept will be ultimately limited by the conversion efficiency (shot noise) as well as the ambient and internally-generated thermal radiation (thermal noise). High-Q whispering-gallery resonators allow for efficient up-conversion by pumping them with continuous-wave laser sources of just few milliwatts of power, in presence of a mm-wave resonant mode. On the other hand, the mm-wave mode in the crystal can be strongly decoupled from the thermal bath provided that the crystal has low absorption at such frquencies. In this talk, we discuss the advances in whispering-gallery-based electro-optic modulators, and show promising techniques for approaching the conversion efficiency to unity. Additionally, we make a thermal noise study of the concept, and show that it can be significantly reduced by designing properly the geometries of both, resonator and coupler, such that the THz mode is radiatively cooled. Moreover, some approaches currently under research to achieve broadband up-conversion are discussed. Due to its high sensitivity at room temperature, this technique finds applications of technological and scientific interests such as radio astronomy, earth observation and planetary missions.