Real-time displacement measurement immune from atmospheric parameters using optical frequency combs

Abstract

We propose a direct and real-time displacement measurement using an optical frequency comb, able to compensate optically for index of refraction variations due to atmospheric parameters. This scheme could be useful for applications requiring stringent precision over a long distance in air, a situation where dispersion becomes the main limitation. The key ingredient is the use of a mode-locked laser as a precise source for multi-wavelength interferometry in a homodyne detection scheme. By shaping temporally the local oscillator, one can directly access the desired parameter (distance variation) while being insensitive to fluctuations induced by parameters of the environment such as pressure, temperature, humidity and CO2 content.

Experimental single-photon pulse characterization by electro-optic shearing interferometry

“…The time-frequency (TF) degree of freedom constitutes an infinite Hilbert space [1], allowing an information content per photon limited only by the encoder and detector resolution. Accessing the information contained in both the spectral amplitude and phase domains of ultrafast pulsed modes of quantum light raises the possibility of surpassing the standard quantum limit in precision measurements such as pulse time-of-flight [2] and atmospheric characteristics [3]. Furthermore, the freedom to encode quantum information in multiple spectral-temporal modes, and then to recover that information, extends the usefulness of quantum secure information protocols such as quantum key distribution (QKD) [4].…”

Quantum limited measurements with optical frequency combs

“…Usually, this problem is tacked by measuring separately the environmental parameters or using several wavelengths, which can be difficult and require post-processing. We show that using the same technique as previously shown, the parasitic effects due to the medium in a distance measurement can be canceled by shaping properly the local oscillator [3]: we choose for the local oscillator a mode that is orthogonal to the environmental effects, so the homodyne detection is insensitive to them, at the expense of a lower sensitivity. This scheme is an all-optical and real-time measurement of distance in a dispersive medium.…”

Influence of Diverse Atmospheric Conditions on Optical Properties of a Pulse Laser in a Time-of-Flight Laser Range Finder

“…Recently, a femtosecond laser was implemented for the precise measurement of distance in the TOF-LRF system to effectively improve the resolution [6,7]. For the TOF-LRF system, however, the main limitation of the precise measurement of distance is the unexpected property change of the pulse laser caused by the variation of the standard atmospheric conditions [8]. The measurement error of distance is usually induced by the variation of group velocity because of the pulse width broadening [8][9][10][11].…”

“…For the TOF-LRF system, however, the main limitation of the precise measurement of distance is the unexpected property change of the pulse laser caused by the variation of the standard atmospheric conditions [8]. The measurement error of distance is usually induced by the variation of group velocity because of the pulse width broadening [8][9][10][11]. The refractive index of air is analyzed with respect to the atmospheric conditions [12,13].…”