Noise-induced pulse-timing statistics in an integrated two-section semiconductor laser with saturable absorber

We have analyzed and explained the generation of irregularly timed, spontaneous-emission triggered optical pulses from a two-section semiconductor laser with saturable absorber, operating near threshold in a regime of excitability. Here we focus on the statistics of the spontaneously emitted pulses. The numerical simulations and analytical theory are based on the Yamada model. The observed irregular pulse train intervals exhibit an initial refractory time, followed by a time interval until the next emitted pulse. The latter is analyzed in terms of a first-passage-time distribution for the intensity to diffuse from its equilibrium value to hit a larger threshold intensity for the first time. Analytic asymptotic short-time and long-time approximations have been derived

Measurements and modeling of a monolithically integrated self-spiking two-section laser in InP

The self-spiking behavior of an integrated saturable absorber and gain section laser fabricated in an InP technology platform is analyzed. The gain, absorber and intensity dynamics are first inspected using the normalized Yamada model. This model shows excitable behavior as well as the relative refractory period, both of which are also present in biological neurons. Measurements of a two-section laser show irregular spike generation on the millisecond timescale, with a saturable absorber voltage controlled spike density. From our simulations, and from the quasi-random character and millisecond timescale at which these pulses occur, we conclude the laser is triggered by noise, an important characteristic in the operation of biological neurons. Simulations of the laser around the excitability threshold using a newly proposed model with an optical noise term show qualitatively similar self-spiking behavior as measured.</p

Phase-space analysis of a two-section InP laser as an all-optical spiking neuron:dependency on control and design parameters

Using a rate-equation model we numerically evaluate the carrier concentration and photon number in an integrated two-section semiconductor laser, and analyse its dynamics in threedimensional phase space. The simulation comprises compact model descriptions extracted from a commercially-available generic InP technology platform, allowing us to model an applied reverse-bias voltage to the saturable absorber. We use the model to study the influence of the injected gain current, reverse-bias voltage, and cavity mirror reflectivity on the excitable operation state, which is the operation mode desired for the laser to act as an all-optical integrated neuron. We show in phase-space that our model is capable of demonstrating four different operation modes, i.e. cw, self-pulsating and an on-set and excitable mode under optical pulse injection. In addition, we show that lowering the reflectivity of one of the cavity mirrors greatly enhances the control parameter space for excitable operation, enabling more relaxed operation parameter control and lower power consumption of an integrated two-section laser neuron

Optical Josephson effects using phase-conjugating mirrors: an analogy with superconductors, Journal of Telecommunications and Information Technology, 2000, nr 1-2

Motivated by the analogy between a phaseconjugating mirror (PCM) and a superconductor, we search for optical counterparts of the well-known DC and AC Josephson effects. We show that in a system consisting of two PCM’s separated by vacuum an „optical supercurrent” arises as a function of an applied phase difference between the PCM’s, which is the optical analogue of the DC supercurrent flowing in a superconducting weak link. The corresponding AC effect occurs when the two PCM’s are pumped by light of a different frequency, causing the phase difference to oscillate in time with the frequency difference

Rate Equation Theory for Organic Diode Laser and Experimental Validation with Microcavity OLED

We present a new model for an organic laser diode based on rate equations for polarons, singlet and triplet excitons, both in host and dopant molecules, and photon densities. The model is validated by comparing calculated optical responses with measurements on high-speed low-Q OLEDS under pulsed nanosecond electrical excitation. The model confirms the threshold-current density of ~500A/cm2 observed in the recent first experiment with indication of lasing in an OLED with DFB-grating in the group of Adachi [1], if the Q-factor ~20K and no residual absorption occurs