title: 10 aJ-level sensing of nanosecond pulse below 10 THz by frequency upconversion detection via DAST crystal: more than a 4 K bolometer.
abstract: By using frequency upconversion detection of terahertz (THz) waves via 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) crystal with an optimized frequency conversion process, ultrahigh sensitivity has been achieved. Direct comparisons with a 4 K bolometer were implemented. By using a simple positive intrinsic negative (PIN) diode without either electrical amplification or optical amplification, frequency upconversion detection can compete with the commercial 4 K bolometer, while by replacing the PIN diode with an avalanche photo diode (APD), it performs more than three orders better than the 4 K bolometer. Based on power calibration, the minimum detectable THz pulse energy is in the order of 10 aJ (9-25 aJ) at 4.3 THz, with a pulse duration of 6 ns. Thus, the minimum number of THz photons that can be detected is down to the order of 10(3) at room temperature. The current THz detection system gives a noise equivalent power (NEP) in the order of 100  fW/Hz(1/2) (50-128  fW/Hz(1/2)). Moreover, by switching current optical detectors, the dynamic range is over six orders.
authors.forename: Feng
authors.initials: F
authors.lastname: Qi
authors.forename: Shuzhen
authors.initials: S
authors.lastname: Fan
authors.forename: Takashi
authors.initials: T
authors.lastname: Notake
authors.forename: Koji
authors.initials: K
authors.lastname: Nawata
authors.forename: Takeshi
authors.initials: T
authors.lastname: Matsukawa
authors.forename: Yuma
authors.initials: Y
authors.lastname: Takida
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Minamide