This paper presents a summary review of some of the available foundry services offering Silicon Photonics, comparing the key technologies available to European technology innovators that drive the technology sector. The foundries providing these unique technologies include AMF, CEA Leti, CORNERSTONE, Global Foundries, ihp, imec, and LioniX International. The review will also show examples of Silicon Photonics in emerging application domains from selected foundries.
We discuss the design and the dynamics of a semiconductor laser integrated with a long on-chip optical feedback (see also [Verschaffelt et al., Chaos: An Interdisciplinary Journal of Nonlinear Science, vol. 27, pp. 114310, 2017]1). Such lasers with optical feedback are interesting for several applications that make use of their rich dynamical behavior. Moreover, they are ideal test-beds to experimentally study delay induced dynamics, because the system's parameters (such as the laser injection current and the optical feedback strength) can be easily accessed and accurately controlled. The system discussed here uses only standard building blocks of the generic Jeppix platform for photonic integrated lasers. The design is based on a DBR-laser with a spiral delay waveguide. We have included several control pads with which we can tune the fabricated laser's emission wavelength, the feedback strength and phase in order to compensate for fabrication tolerances. We have been able to integrate a 10 cm feedback length on a footprint of 5.5 mm2. We illustrate that this delay is sufficiently long to drive the laser into a chaotic regime, and we analyze the chaotic dynamics based on the spectrum, autocorrelation and permutation entropy. We show - using the NIST statistical test suite for random number generators - that the observed delay dynamics is sufficiently complex for random number generation at a rate of 500 Mbits/s.
It is well known that the performance of semiconductor lasers is very sensitive to external optical feedback. This feedback can lead to changes in lasing characteristics and a variety of dynamical effects including chaos and coherence collapse. One way to avoid this external feedback is by using optical isolation, but these isolators and their packaging will increase the cost of the total system.
Semiconductor ring lasers nowadays are promising sources in photonic integrated circuits because they do not require cleaved facets or mirrors to form a laser cavity. Recently, some of us proposed to combine semiconductor ring lasers with on chip filtered optical feedback to achieve tunable lasers. The feedback is realized by employing two arrayed waveguide gratings to split/recombine light into different wavelength channels. Semiconductor optical amplifier gates are used to control the feedback strength. In this work, we investigate how such lasers with filtered feedback are influenced by an external conventional optical feedback.
The experimental results show intensity fluctuations in the time traces in both the clockwise and counterclockwise directions due to the conventional feedback. We quantify the strength of the conventional feedback induced dynamics be extracting the standard deviation of the intensity fluctuations in the time traces. By using filtered feedback, we can shift the onset of the conventional feedback induced dynamics to larger values of the feedback rate [ Khoder et al, IEEE Photon. Technol. Lett. DOI: 10.1109/LPT.2016.2522184]. The on-chip filtered optical feedback thus makes the semiconductor ring laser less senstive to the effect of (long) conventional optical feedback. We think these conclusions can be extended to other types of lasers.
Tunable laser diodes are needed in a range of applications including wavelength division multiplexing, optical instrument testing, optical sensing and tera hertz generation. In this work, we investigate the stability of lasers which use filtered optical feedback for wavelength tuning. We investigate experimentally the dynamics induced by this on-chip filtered optical feedback.
In this study, we choose to use a compact device which combines a semiconductor ring laser with on-chip filtered optical feedback to achieve wavelength tunability. The filtered optical feedback is realized by employing two arrayed waveguide gratings to split/recombine light into different wavelength channels. Semiconductor optical amplifiers are placed in the feedback loop in order to control the feedback of each wavelength channel independently.
Experimental observations show that the stability of the clockwise and counterclockwise propagation modes depends on the feedback strength. Experiments also show that for a specific range of the feedback strength, anti-phase oscillations in the intensity of the clockwise and counterclockwise propagating modes can be induced. These oscillations could not be seen in the same semiconductor ring laser without filtered optical feedback. We investigate how the frequency and the amplitude of these oscillations change under the effect of filtered optical feedback. We also discuss how these anti-phase oscillations can be suppressed by properly choosing the feedback strength.
Laser diodes that emit multiple wavelengths simultaneously are needed in a range of applications including wavelength division multiplexing, high speed optical networks and tera-hertz generation. In this work we report on an integrated approach to obtain multi-wavelength emission from a semiconductor ring laser based on on-chip filtered optical feedback. Semiconductor ring laser have the advantage that they can be easily integrated with other optical components as they do not require mirrors to form the cavity. Moreover, no thermal control of the wavelength emission is needed and therefore the device can be in principle fast. The filtered optical feedback is realized by employing two arrayed waveguide gratings to split/recombine light into different wavelength channels. Semiconductor optical amplifiers are placed in the feedback loop in order to control the feedback strength of each wavelength channel independently. Experimental observations [Khoder et al, Optics. Lett. 38, 2608{2610, 2013] have shown that the effective gain is the key parameter that has to be balanced using the feedback in order to achieve multi-wavelength emission. This can be achieved by tuning the injection current in each amplifier which will change the feedback phase and strength. Numerical simulations using rate equations reproduce the experimental results and show the effects of feedback phase and strength on the multi-wavelength emission.
We present an advanced simulation tool for optical time-domain reflectometry (OTDR) with the ability to incorporate any OTDR pulse shape. According to our knowledge, the proposed OTDR simulator is the first one with this feature, thus progressing beyond the existing state of the art of OTDR simulations. Starting from a mathematical formalism, we develop the numerical implementation of the simulation tool. To include the effects of the OTDR pulse shape, the optical fiber network under test is treated in our approach as a linear time-invariant single-input/single-output system. Furthermore, the limitations of current OTDR equipment such as (nonlinear) power saturation of the OTDR detector, and limited dynamic range due to detector noise are also incorporated into the simulation model. Our simulation results are experimentally verified with OTDR measurements, and we show an excellent agreement between the simulated traces and the measured traces. The advanced OTDR simulation tool has proven to correctly reproduce measured traces of systems for various pulse widths, and is thus very valuable to evaluate the usability of OTDR measurements for a certain application, without the need to run actual OTDR measurements.
Semiconductor ring lasers are promising sources in photonic integrated circuits because they do not require cleaved facets or mirrors to form a laser cavity. In this work, we characterize the wavelength switching speed of a tunable semiconductor ring lasers using filtered optical feedback. The filtered optical feedback is realized by employing two arrayed waveguide gratings to split/recombine light into different wavelength channels. Semiconductor optical amplifiers are placed in the feedback loop in order to control the feedback of each wavelength channel independently. The wavelength switching is achieved by changing the currents injected in the semiconductor optical amplifier gates. Experimentally, we observe a wavelength transition time of 5 ns. However, we also noticed a non-negligible delay in the switching process. [ Khoder et al, IEEE Photon. Technol. Lett. 26, 520{523, 2014]. We numerically reproduce the experimental results using rate equations taking into account the effect of spontaneous emission. The simulations further elaborate on the effect of the noise strength on the wavelength transition time and the delay time.
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