Sub-Shot-Noise-Limited Optical Heterodyne Detection Using an Amplitude-Squeezed Local Oscillator

Abstract

We experimentally demonstrate a novel sub-shot-noise-limited heterodyne detection scheme to measure a weak optical signal field by employing amplitude-squeezed light as the local oscillator (LO) field. The amplitude-squeezed LO field at 428.8 nm is generated from a high efficiency single-pass second-harmonic generation in a KNbO 3 crystal pumped by femtosecond (130 fs) pulses at 857.6 nm, and the signal field is combined with the generated squeezed LO field through the crystal. An enhancement of 0.7 dB (1.4 dB inferred) in signal-to-noise ratio beyond the shot-noise limit is directly observed. [S0031-9007(99)09410-7]

Signal-to-noise ratio in squeezed-light laser radar

“…In laser radar applications, loss from spreading and absorption in the target-return beam can be severe [2]. It is therefore natural to investigate the potential of using squeezed light in the local oscillator of a heterodyne laser radar system [3][4][5], since the loss suffered by the local oscillator beam will be minimal. Here we review relevant signal detection theory and quantum optics formalism, and compute the signal-to-noise ratio (SNR) for several application scenarios.…”

Can Signal-To-Noise Be Improved by Heterodyne Detection Using an Amplitude Squeezed Local Oscillator?

“…In "Sub-Shot-Noise-Limited Optical Heterodyne Detection Using an Amplitude-Squeezed Local Oscillator" by Li et al [1], it is claimed that increased signal sensitivity (higher signal-to-noise) is achieved in a novel optical heterodyne detection arrangement by using a squeezed local oscillator. This is a surprising result because (as noted in the first paragraph on p. 5226 of the Letter) ultimately the sensitivity in a standard heterodyne measurement is limited by vacuum fluctuations entering with the signal.…”

“…[1] ] is based on the assumption that the signal field passes unchanged through the nonlinear crystal (fourth paragraph, second page, Ref. [1]). Given that the action of the squeezer is to deamplify amplitude fluctuations, is the signal really unaffected?…”

“…(2), Ref. [1] ] is based on the assumption that the signal field passes unchanged through the nonlinear crystal (fourth paragraph, second page, Ref. [1]).…”

“…[11][12][13][14] in Ref. [1]) where the vacuum modes at the actual signal measurement site are replaced with modes which are squeezed or exhibit nonclassical correlations.…”