High-resolution adaptive interferometer with dynamic population grating recorded at 1064  nm in ytterbium-doped fiber

Abstract

An adaptive optical fiber sensor/demodulator of an optical phase modulation with a Sagnac interferometer configuration is reported. The dynamic population grating recorded in ytterbium-doped fiber (YDF) at a wavelength of 1064 nm enables adaptive properties of this configuration with a high-pass transfer function and with the cut-off frequency of about 260 Hz at ∼ 10 m W cw recording power. A linear response with nearly 100% modulation depth is ensured by effective formation of the nonshifted phase dynamic grating with the amplitude one order of magnitude greater than can be expected from the saturation of the YDF absorption at the recording wavelength. This is associated with the photoinduced changes in the UV optical absorption of the YDF and enables minimal detected amplitude of the phase modulation ≈ 0.7 ∗ 10 − 7 H z in our experimental configuration. We believe that, in general, this mechanism of the phase grating formation can ensure the sensor resolution limited by the photonic noise of the utilized light power only.

Brillouin-like effects in rare-earth-doped bi-directional optical fiber amplifiers

“…In open-cavity fiber lasers, the slowly-moving dynamical population inversion gratings inscribed in an active medium by intracavity radiation have a reverse effect on the inscribing waves via feedback they provide leading to so called "mode-pulse" laser operation different from mode-locked and Q-switched laser regimes 11,12 . Among other PIDG applications are adaptive interferometry 13,14 and nonlinear filtering enabling narrowband operation of semiconductor and fiber laser configurations [15][16][17][18] .…”

Optical-fiber ring cavity with saturable rare-earth-doped fiber

“…Below, we present the results of the experimental investigation of the ring fiber-optic cavity with the saturable ytterbium-doped fiber (YDF) in it. The saturation of the optical absorption in YDF in the wavelength range λ > 1000 nm [10,11] is also accompanied by a significantly larger photoinduced change of the doped fiber refractive index ∆n as compared with that of the optical absorption ∆α(∆n ∆αλ/4π). Simplifying, we can neglect the photoinduced changes of the doped fiber absorption and consider the saturable YDF as a Kerr media with the refractive index dependent on the incident light (I 4 in Fig.…”