Bistability and intensity fluctuations in Zeeman lasers and amplifiers

Matthew Adams

Matthew Adams, H.J. Westlake, M.J. O’Mahony

M.J. Adams, H.J. Westlake, M.J. O’Mahony

Angela Hohl, Rajarshi Roy

Optical bistability in a semiconductor laser-amplifier system has been investigated previously and found to exhibit switching at very low intensities.

Zeqi Pan, T. N. Ding, M. Dagenais

We report the demonstration of cascadability in bistable diode laser amplifiers operated below threshold. A schematic of the experimental set-up is shown in Figure 1. There it is shown that the optical input to the first bistable diode laser amplifier is modulated by a mechanical chopper at frequency Ω1. The output from the first bistable diode laser amplifier is then modulated at Ω2= 2Ω1using a second mechanical chopper. The light is thereafter used as the input to the second bistable device. When the input intensity to the second device is higher than a certain threshold, the output switches. These results are shown in Figure 2. For these experiments, each of the bistable diode laser amplifiers were carefully studied. Detailed bistability measurements at different bias currents and different cavity detuning's were performed. It was found that both the bistability loop and the switching power gets larger as the detuning increases. The size of the hysteresis loop also increased as the laser was operated closer to threshold. In a two beam experiment, it was found that the switching power in the data beam can be as small as 25 nW. Gains larger than 1000 have been demonstrated, indicating the large fan-out capability of these devices. The turn-on and turn-off times in these bistable diode laser amplifiers was measured to be faster than 1 ns and detector limited. These bistable diode laser amplifiers are the most efficient optical devices that have yet been demonstrated and will find applications in photonic switching networks.

P G Fernandez, Luigi A. Lugiato, Francisco Javier Bermejo

It is shown that a laser with a two-photon saturable absorber exhibits a phase instability similar to that of two-photon optical bistability. The authors calculate the spectrum of the intensity fluctuations in the output field under conditions of exact resonance between the amplifier and the absorber. In the bad-cavity limit the relevant part of the spectrum assumes a simple Lorentzian form; as the phase-instability threshold is approached, the reduction of quantum noise becomes perfect for small frequencies.