Physics and Applications of Laser Diode Chaos

An overview of chaos in laser diodes is provided which surveys experimental achievements in the area and explains the theory behind the phenomenon. The fundamental physics underpinning this behaviour and also the opportunities for harnessing laser diode chaos for potential applications are discussed. The availability and ease of operation of laser diodes, in a wide range of configurations, make them a convenient test-bed for exploring basic aspects of nonlinear and chaotic dynamics. It also makes them attractive for practical tasks, such as chaos-based secure communications and random number generation. Avenues for future research and development of chaotic laser diodes are also identified.Comment: Published in Nature Photonic

Tunable two color emission in a compact semiconductor ring laser with filtered optical feedback

We report on an integrated approach to obtain two color emission from a semiconductor ring laser with filtered optical feedback. This feedback is realized on-chip by employing two arrayed waveguide gratings to split/recombine light into different wavelength chan nels. Semiconductor optical amplifiers are used in the feedback loop to control the feed back strength of each wavelength channel independently. Results show that the effective gain of the d(tferent anodes is the key parameter which has to be balanced to obtain two color emission. This can be aclueved by tuning the injection current in each amplifie

Switchable multiwavelength emission using semiconductor ring laser with optical filtered feedback

Email Print Request Permissions Summary form only given. Single laser chips that emit multiple wavelengths simultaneously are interesting for a range of applications including wavelength division multiplexing, optical instrument testing and optical sensing. A number of approaches have been proposed to achieve multiple wavelength emission (MWE) by e.g. using multiple lasers, but they tend to be bulky and/or expensive. Some of these structures need thermal tuning of the emission wavelengths, which is relatively slow and requires precise control of the chip temperature. In this work we report on a novel integrated approach in order to obtain MWE from a single semiconductor laser based on on-chip filtered optical feedback. The layout of our device is shown in Fig.1(a). It consists of semiconductor ring laser (SRL), two arrayed waveguide gratings which are used to split/recombine light into 4 different wavelength channels, four semiconductor optical amplifier gates and passive and active waveguides to connect these different components.We can select either triple wavelength emission, dual wavelength emission (DWE) or single longitudinal mode emission (SME) by properly adjusting the currents in the semiconductor optical amplifier gates of the feedback loop. An advantage of our device is that we can select the lasing longitudinal modes, and thus the emitted wavelengths, in a simple manner by changing the current in the feedback amplifiers. Wavelength selection is done in a non-thermal fashion, which can in principle be done fast. MWE is achieved in a SRL, which has the additional advantage that it can easily be integrated with other photonic components on a chip.Experimentally the device output without feedback is multi-mode above the threshold current (64 mA). SME can be achieved by pumping one gate with a suitable current [1]. When current is applied to two gates at the same time while the SRL is biased above threshold current, SRL shows DWE for a range of currents on gate 4 and gate 2. This DWE can b- observed in the optical spectrum shown in Fig.1(b), at the top of this figure we show a schematic plot of the filter passband of each of the gate channels. The selected longitudinal modes are spectrally positioned within the arrayed waveguide gratings filter passbands corresponding to gate 2 and gate 4 which are chosen to be pumped. The two peak wavelengths are ¿1 = 1580.788 nm (gate 4 channel), ¿2 = 1583.288 nm (gate 2 channel). This DWE can be explained by the fact that a suitable amount of feedback cancels the gain difference between the wavelength channels due to fabrication and material dichroism. By increasing or decreasing the current injected in one of the pumped gates, we notice switching from two modes in the output to one of them. By pumping three gates instead of two and by precise adjustment of the currents in the gates, triple wavelength emission was observed with similar switching behavior to DWE and then to SME just by changing one of the gate currents. In this contribution we will further discuss the precise behavior of the MWE from the device. We will also show results from numerical simulations based on two directional-mode model[2] extended with Lang-Kobayashi terms to take into account for optical feedback. Some of these numerical results are shown in Fig.1(c). We plot in this figure the maxima of the intensities of the three modes when the feedback phase is equal to 0.5p for each mode. The first modes feedback strength ¿1 is fixed while the feedback strength ¿2 and ¿3 of the second and third modes are kept equal ¿2 = ¿3 and are increased simultaneously. As can be seen from Fig1.(c), the device output is changing from SME when (¿2 = ¿3) ¿1. The numerical results are in qualitative agreement with the

Fast random bit generation based on a single chaotic semiconductor ring laser

Here, we numerically and experimentally demonstrate that, by combining two post-processing methods (multi-bit extraction and bitwise OR-exclusive (XOR) operations). in a single chaotic semiconductor ring laser (SRL), it is possible to generate true random bits with a bit rate up to 40 Gb/s from a chaos bandwidth of ˜ 2 GHz, thanks to the device ability of lasing in two directional modes and the fact that the two mode signals have low correlations. In addition, SRLs can be easily implemented on chip

Fully analogue photonic reservoir computer

Introduced a decade ago, reservoir computing is an efficient approach for signal processing. State of the art capabilities have already been demonstrated with both computer simulations and physical implementations. If photonic reservoir computing appears to be promising a solution for ultrafast nontrivial computing, all the implementations presented up to now require digital pre or post processing, which prevents them from exploiting their full potential, in particular in terms of processing speed. We address here the possibility to get rid simultaneously of both digital pre and post processing. The standalone fully analogue reservoir computer resulting from our endeavour is compared to previous experiments and only exhibits rather limited degradation of performances. Our experiment constitutes a proof of concept for standalone physical reservoir computers.SCOPUS: ar.jinfo:eu-repo/semantics/publishe