Mode behavior in ultralarge ring lasers

Abstract

Contrary to expectations based on mode spacing, single-mode operation in very large He-Ne ring lasers may be achieved at intracavity power levels up to approximately0.15 times the saturation intensity for the He-Ne transition. Homogeneous line broadening at a high total gas pressure of 4-6 Torr allows a single-peaked gain profile that suppresses closely spaced multiple modes. At startup, decay of initial multiple modes may take tens of seconds. The single remaining mode in each direction persists metastably as the cavity is detuned by many times the mode frequency spacing. A theoretical explanation requires the gain profile to be concave down and to satisfy an inequality related to slope and saturation at the operating frequency. Calculated metastable frequency ranges are > 150 MHz at 6 Torr and depend strongly on pressure. Examples of unusual stable mode configurations are shown, with differently numbered modes in the two directions and with multiple modes at a spacing of approximately 100 MHz.

ZAIGA: Zhaoshan long-baseline atom interferometer gravitation antenna

“…Improving sensitivity of gyroscopes is very important to more precisely measure the Lense-Thirring effect. Large-scale ground laser ring gyroscopes with the aim for geophysical applications and for measuring the Lense-Thirring effect, are under development [124][125][126][127][128]. Atom gyroscope has a high potential sensitivity [129,130] and dual Raman-type atom interferometers can cancel the common noise.…”

Controlling the non-linear intracavity dynamics of large He–Ne laser gyroscopes

“…To this aim, we propose an experimental method based on the observation of the birth of additional longitudinal modes of the laser while rising up the laser excitation power. This dynamical change is known as "multimode transition", and has been widely studied in the literature, mainly for medium size and large size ring laser [13,19]. The value of the mean light intensity for the multimode transition expressed in Lamb units I th , is commonly defined multimode threshold.…”

Self-locked operation of large He–Ne ring laser gyroscopes

“…We have usually operated this laser (and our other large ring lasers) with oscillation on a single longitudinal mode. The single-mode behaviour has been described in detail in [19]. Despite the close mode spacing in large cavities, singlemode oscillation is readily achieved [4], but it necessitates low intra-cavity beam intensity.…”