Abstract-Terahertz detection by upconversion to the near-infrared using picosecond pulses

 

 Schematic of the experimental setup. A pulsed laser at about 1550 nm (orange) is used to pump the terahertz source and a frequency-doubling crystal to generate the NIR pump beam (red). Reflective bandpass filters are used to narrow the spectrum before the pump enters the nonlinear medium together with the terahertz radiation (green). SHG: second harmonics generation, PPLN: periodically poled lithium niobate crystal, RBP: reflective bandpass, M: mirror, ITO: indium-tin-oxide coated glass, PCA: photoconductive antenna, f1,f2${\mathrm{f}}_1,{\mathrm{f}}_2$: lenses (focal lengths of f1${\mathrm{f}}_1$: 125 mm, f2${\mathrm{f}}_2$: 400 mm).

Tobias Pfeiffer, Daniel Molter, and Georg von Freymann

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-28-20-29419

The detection of terahertz photons by using silicon-based devices enabled by visible photons is one of the fundamental ideas of quantum optics. Here, we present a classical detection principle using optical upconversion of terahertz photons to the near-infrared spectral range in the picosecond pulse regime, which finally enables the detection with a conventional sCMOS camera. By superimposing terahertz and optical pump pulses in a periodically poled lithium-niobate crystal, terahertz photons at 0.87 THz are converted to optical photons with wavelengths close to the central pump wavelength of 776 nm. A tunable delay between the pulses helps overlap the pulses and enables time-of-flight measurements. Using a sCMOS camera, we achieve a dynamic range of 47.8 dB with a signal to noise ratio of 23.5 dB at a measurement time of one second, in our current setup.

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