Mode-Coupling Control in Resonant Devices: Application to Solid-State Ring Lasers

Abstract

A theoretical and experimental investigation of the effects of mode coupling in a resonant macroscopic quantum device is achieved in the case of a ring laser. In particular, we show both analytically and experimentally that such a device can be used as a rotation sensor provided the effects of mode coupling are controlled, for example through the use of an additional coupling. A possible generalization of this example to the case of another resonant macroscopic quantum device is discussed.PACS numbers: 42.65. Sf, 42.62.Eh, 06.30.Gv, 42.55.Rz Devices using macroscopic quantum effects [1] and their associated phenomenon of interference to detect rotations can be arbitrarily divided into two classes [2], namely non-resonant and resonant devices. In devices of the first class, the rotation-induced phase shift is detected by looking at the displacement of an interference pattern. Among such devices are the fiber optic gyroscope [3], the gyromagnetic gyroscope [4], the superfluid gyrometer [5] and the atomic interferometer [6]. In devices of the second class, the rotation is detected through a beat signal. Two examples of resonant and potentially rotation-sensitive devices are the ring laser [7] and the superfluid (e.g. liquid helium or Bose-Einstein condensed gas) in a ring container [8]. In these two examples, it has been shown [9, 10] that a non-linear mode coupling effect plays a crucial role in the system dynamics, usually preventing it from operating in a rotation sensitive regime, unless an additional adequate coupling is set.For example, in the case of the ring laser, the bidirectional emission regime, required for rotation sensing, can be inhibited because the counter-propagating modes share the same gain medium and can be subject to mode competition. This problem is usually circumvented by choosing for the gain medium a two isotopes mixture of helium and neon and by tuning the laser emission frequency out of resonance with the atoms at rest. Provided the detuning value is bigger than the atomic natural linewidth, the gain medium can then be considered as being inhomogeneously broadened and coexistence of the counter-propagating modes occurs [11]. In the case of solid-state ring lasers, the gain medium is homogeneously broadened, leading to a strongly coupled situation resulting in laser emission in only one direction [10].We report in this Letter theoretical and experimental investigation of mode coupling control in a solid-state (Nd:YAG) ring laser. The main natural sources of coupling between the counter-propagating modes are identified, and their role in the laser dynamics is discussed. An additional coupling source is introduced in order to ensure the coexistence of the counter-propagating modes.A condition for rotation sensing is then analytically derived, and an experimental confirmation of this theoretical investigation is reported. It is eventually pointed out that the two-level toy model developed in [9] to describe a superfluid placed in a rotating ring container leads to a similar rotation sens...

Resonance Assisted Synchronization of Coupled Oscillators: Frequency Locking without Phase Locking

“…On the contrary, no theoretical analysis of the phase dynamics is at present available in the ''intermediate coupling'' regime [8] where f A % f R . Finally, we note that our observations can be relevant for semiconductor lasers also, and find application in solid-state gyros [17]. It would also be interesting to observe the effect of a resonant delayed coupling [18].…”

Ring-laser gyroscope without the lock-in phenomenon

“…(1), (10), (11), and (13) in ring lasers, we expand these equations by the eigenmode basis of a rotating cavity derived in subsection II A and derive the amplitude-and the phase-equations of the modes, although in conventional theoretical approaches, CW-and CCW-rotating wave basis has been frequently used [2,3,4,5,6,10,11,12,13]. As demonstrated in Ref.…”

“…Equations (1), (10), (11), and (13) are the fundamental ones describing the light field and the gain medium mentioned above.…”

“…As is well-known, the nonlinearity inherent in these gain media leads to a spatial hole burning effect and suppresses one of the counter-propagating waves due to gain competition (in an ideal ring laser without backscattering and noise sources), unlike in the case of gaseous medium [4,5]. While several theoretical and experimental works exist for solidstate RLGs, many of the investigations have so far focused on overcoming or controlling such a nonlinearity [9,11,12,14]. Meanwhile, backscatter-induced phenomenon, such as lock-in, and the properties of the RLGs at slow rotation rates have not yet been examined in detail.…”

“…While conventional RLGs utilize a gaseous medium (He-Ne) as a gain medium, a new type of RLG using solid states and a semiconductor material have recently received research attention [7,8,9,10,11,12,13,14,15,16]. As is well-known, the nonlinearity inherent in these gain media leads to a spatial hole burning effect and suppresses one of the counter-propagating waves due to gain competition (in an ideal ring laser without backscattering and noise sources), unlike in the case of gaseous medium [4,5].…”