Measurements and Modeling of a Monolithically Integrated Self-Spiking Two-Section Laser in InP

Abstract

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.

First-Passage-Time Analysis of the Pulse-Timing Statistics in a Two-Section Semiconductor Laser under Excitable and Noisy Conditions

“…In excitable conditions, the laser emits a short optical pulse when triggered by an optical input pulse of sufficiently large energy and thus can operate as an Photonics 2022, 9, 860 2 of 13 artificial neuron. We will demonstrate, both experimentally [15] and in simulations, that near the lasing threshold, such an optical trigger can also be caused by a sufficiently large positive intensity fluctuation due to spontaneous-emission noise. As this "spontaneous" emission of output pulses is a source of errors in the functionality of this artificial neuron, it is relevant to investigate this phenomenon in more detail as to its statistics, which is the purpose of the present study.…”

“…A schematic of the two-section laser and a photograph of one of the fabricated devices can be seen in Figure 1. The measurement set up and method are described in [15].…”

“…apart from self-pulsations and CW operation, a form of excitability when operating near, but below threshold [12][13][14]. In excitable conditions, the laser emits a short optical pulse when triggered by an optical input pulse of sufficiently large energy and thus can operate as an artificial neuron.…”

“…One successful realization of a photonic spiking neuron is by using an integrated two-section Fabry-Pérot-type (FP) semiconductor laser, where one section operates as the gain and the other as saturable absorber. This configuration is known to exhibit, apart from self-pulsations and CW operation, a form of excitability when operating near, but below threshold [12][13][14]. In excitable conditions, the laser emits a short optical pulse when triggered by an optical input pulse of sufficiently large energy and thus can operate as an Photonics 2022, 9, 860 2 of 13 artificial neuron.…”

“…A semiconductor laser with saturable absorber is accurately described by the wellknown Yamada model [12,16,17], which will be used in this paper to investigate the effects of optical noise on the laser's self-spiking behaviour and in simulations. By interpreting the noise-triggered self-pulsations in the excitability parameter region, in terms of first-passage events for the intensity, we derive analytic approximations for the self-pulsation timing statistics, which can be compared with simulated and observed timing statistics [15].…”