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In this work, a passive reservoir computing scheme is presented, which relies on the excitation and guiding of transverse modes in a large cross-section photonic waveguide. The optical modes act similar to conventional waveguide-based reservoir nodes, whereas random defects act as the operational equivalent of internode connections. Therefore, the proposed scheme’s number of nodes and connections can scale with the waveguide’s volume, contrary to planar implementations. The principle of operation, alongside the role of mode defects to performance, is validated through a numerical model, whereas the classification of time-dependent, 2D analog/digital image streams is used as an application-relevant benchmark test. © 2019 Optical Society of America.

In an environment where cyber attacks are increasing, both in frequency and complexity, novel ways to shield data, users, and procedures have to be envisioned. Physical unclonable functions (PUFs) are the physical equivalent of one-way mathematical transformations with the exception that their inherent physical complexity renders them resilient to cloning. One interesting deployment scenario includes PUFs as random key generators. The deterministic nature of their operation alleviates the necessity to store the keys in non-volatile means. Along the same lines, blockchain is inherently resistant to modification of the data once stored while their overall security depends on the quality and secrecy of users' keys. Here, the authors propose a novel optical PUF implementation that can be combined with private blockchain modalities in order to cyber-harden Internet of things ecosystems. PUF-related experimental results are presented, alongside implementation scenarios. © 2018 The Institution of Engineering and Technology.

Physical unclonable functions are the physical equivalent of one-way mathematical transformations that, upon external excitation, can generate irreversible responses. Exceeding their mathematical counterparts, their inherent physical complexity renders them resilient to cloning and reverse engineering. When these features are combined with their time-invariant and deterministic operation, the necessity to store the responses (keys) in non-volatile means can be alleviated. This pivotal feature, makes them critical components for a wide range of cryptographic-authentication applications, where sensitive data storage is restricted. In this work, a physical unclonable function based on a single optical waveguide is experimentally and numerically validated. The system's responses consist of speckle-like images that stem from mode-mixing and scattering events of multiple guided transverse modes. The proposed configuration enables the system's response to be simultaneously governed by multiple physical scrambling mechanisms, thus offering a radical performance enhancement in terms of physical unclonability compared to conventional optical implementations. Additional features like physical re-configurability, render our scheme suitable for demanding authentication applications. © 2018 The Author(s).

In this work, a photonic physical unclonable function module, based on an optical waveguide, is demonstrated. The physical scrambling mechanism is based on the random and complex coherent interference of high order optical transverse modes. The proposed scheme allows the generation of random bit- strings, through a simple wavelength tuning of the laser source, that are suitable for a variety of cryptographic applications. The experimental data are evaluated in terms of unpredictability, employing typical information theory benchmark tests and the NIST statistical suit. © 2018, The Author(s).

Neuro-inspired implementations have attracted strong interest as a power efficient and robust alternative to the digital model of computation with a broad range of applications. Especially, neuro-mimetic systems able to produce and process spike-encoding schemes can offer merits like high noise-resiliency and increased computational efficiency. Towards this direction, integrated photonics can be an auspicious platform due to its multi-GHz bandwidth, its high wall-plug efficiency and the strong similarity of its dynamics under excitation with biological spiking neurons. Here, we propose an integrated all-optical neuron based on an InAs/InGaAs semiconductor quantum-dot passively mode-locked laser. The multi-band emission capabilities of these lasers allows, through waveband switching, the emulation of the excitation and inhibition modes of operation. Frequency-response effects, similar to biological neural circuits, are observed just as in a typical two-section excitable laser. The demonstrated optical building block can pave the way for high-speed photonic integrated systems able to address tasks ranging from pattern recognition to cognitive spectrum management and multi-sensory data processing.

In this Letter, we present and fully model a photonic scheme that allows the high-speed identification of images acquired through the dispersive Fourier technique. The proposed setup consists of a photonic reservoir-computing scheme that is based on the nonlinear response of randomly interconnected InGaAsP microring resonators. This approach allowed classification errors of 0.6%, whereas it alleviates the need for complex high-cost optoelectronic sampling and digital processing. © 2015 Optical Society of America.

We experimentally study the generation and amplification of stable picosecond-short optical pulses by a master oscillator power-amplifier configuration consisting of a monolithic quantum-dot-based gain-guided tapered laser and amplifier emitting at 1.26 μm without pulse compression, external cavity, gain-or Q-switched operation. We report a peak power of 42 W and a figure-of-merit for second-order nonlinear imaging of 38.5 W2 at a repetition rate of 16 GHz and an associated pulse width of 1.37 ps. © 2015 Optical Society of America.

The intensity and timing noise of a 40-GHz quantum dot passively mode-locked laser with noncolliding cavity is numerically investigated and compared with the corresponding performance of the conventional self-colliding cavity. A detailed mapping of the pulse and noise properties versus the bias conditions shows that the devices based on the noncolliding cavities can generate shorter and stronger pulses with lower intensity and timing noise compared with the self-colliding counterparts if the gain to absorber length ratio is optimized. © 1989-2012 IEEE.

Mid-infrared silicon photonics emerge as the dominant technology to bridge photonics and electronics in multifunctional high-speed integrated chips. The transmission and processing of optical signals lying at the mid-infrared wavelength region is ideal for sensing, absorption-spectroscopy and free-space communications and the use of group IV materials becomes principally promising as the vehicle towards their realization. In parallel, optical forces originating from modes and cavities can reach to outstandingly large values when sizes drop into the nanoscale. In this work, we propose the exploitation of large gradient optical forces generated between suspended silicon beams and optomechanical transduction as a means of converting signals from the mid-infrared to the near-infrared region. A mid-infrared signal is injected into the waveguide system so as to excite the fundamental symmetric mode. In the 2-5 mu m wavelength range, separation gaps in the 100nm order and waveguide widths ranging from 300-600nm, the mode is mostly guided in the air slot between the waveguides which maximizes the optomechanical coupling coefficient and optical force. The resulting attractive force deflects the waveguides and the deflection is linearly dependent on the mid-infrared optical power. A simple read-out technique using 1.55 mu m signals with conventional waveguiding in the directional coupler formed by the two beams is analyzed. A positive conversion efficiency (>0dB) is foreseen for waveguides with suspending lengths up to 150 mu m. The converter could be ideal for use in sensing and spectroscopy rendering the inefficient mid-infrared detectors obsolete. The low-index unconventional guiding in mid-infrared could be a key component towards multifunctional lab-on-a-chip devices.

We present a numerical analysis that focuses on the temporal pulse properties of a monolithic two-section passively mode locked quantum dot laser subject to optical feedback from a very long external cavity. Pulse duration, shape and intensity noise are studied for the first time to our knowledge versus feedback delay and strength for the case of a passively mode locked semiconductor laser. These temporal characteristics are correlated to the previously observed dependence of repetition rate and timing jitter on cavity parameters in order to highlight the dynamics and complete the corresponding theoretical explanations. © 2013 Elsevier B.V.

In this paper, an alternative approach for an integrated photonic reservoir computer is presented. The fundamental building block of the reservoir is based on the nonlinear response of a ring resonator, where effects such as twophoton absorption and nonlinear refractive index variation were taken into consideration. In order to investigate the validity of this scheme, the response of a single add/drop micro ring was simulated through a traveling wave numerical model, and the parameters that affect the nonlinearity of the response were identified. Based on these results, a 5 × 5 matrix of randomly interconnected resonators was utilized in order to classify different high-bit-rate digital patterns. Simulations confirmed that the proposed system could offer a classification error of 0.5% for bit rates up to 160 Gbps and for 8-bit-length digital words. © 2013 Optical Society of America.

In this paper, we present a theoretical study on the optimization of passively mode-locked quantum dot lasers based on an alternative cavity design. In particular, we investigate a geometry in which the saturable absorber is located near the low reflection facet of the chip (output facet). The investigation is carried out by means of a time-domain traveling wave numerical model for quantum-dot active medium for both the gain and absorbing sections. The analysis shows superior performance in terms of pulsewidth and peak power of devices based on the new geometry compared to devices based on the conventional geometry, where the saturable absorber is placed near the high reflectivity facet. The optimization relies on the enhanced bleaching of the saturable absorber when the latter is located near the output facet, which prevents the generation of colliding or self-colliding pulse effects. © 2012 IEEE.

Microring cavities (diameter D = 2.7-7 μm) with an active region based on InAs/InGaAs quantum dots are fabricated and their characteristics are studied by the microphotoluminescence method and near-field optical microscopy. A value of 22 000 is obtained for the Q factor of a microring cavity with the diameter D = 6 μm. Lasing up to room temperature is obtained in an optically pumped ring microlaser with a diameter of D = 2.7 μm. © 2013 Pleiades Publishing, Ltd.

In this Letter, a design for a tapered InAs/InGaAs quantum dot semiconductor optical amplifier is proposed and experimentally evaluated. The amplifier's geometry was optimized in order to reduce gain saturation effects and improve gain efficiency and beam quality. The experimental measurements confirm that the proposed amplifier allows for an elevated optical gain in the saturation regime, whereas a five-fold increase in the coupling efficiency to a standard single mode optical fiber is observed, due to the improvement in the beam quality factor M2 of the emitted beam. © 2013 Optical Society of America.

The phase and intensity noise of microring lasers coupled with passive waveguides are examined through linewidth and relative intensity noise measurements. Laser linewidth down to 500 KHz was measured through the self-homodyne technique and a direct association is established between the linewidth and the two main structural parameters of a microring, the ring radius and coupling efficiency with the bus waveguide. Coupling efficiency is estimated through waveguiding analysis by means of 3-D finite difference in time domain techniques. © 2006 IEEE.

In this paper, a series of quantum-dot passively mode-locked Fabry-Perot lasers has been experimentally investigated. The devices vary in terms of number of quantum dot layers, thus allowing the extraction of guidelines regarding the impact of this parameter on the quality of mode locking. Although, theoretical estimations imply that the increase of the quantum dot layers can enhance the emitted optical power but degrade mode-locking stability, the experimental evaluation proved that the existence of dual wavelength emission can affect this trend and allow better performance from devices that do not exhibit excited state emission. © 2012 American Institute of Physics.

In this paper we present experimental results related to the dynamic switching of the emission wavelength of a passively mode-locked InAs/InGaAs quantum dot laser. The wavelength switching is achieved through application of varying optical feedback, as opposed to varying electrical biasing conditions, whereas the different regimes of operations include pulse operation either from the ground or the excited state and dual mode locking. Furthermore, through the same technique, Q-switching elimination was achieved, allowing stable pulse amplitude, which is a highly desired feature in many applications. © 2012 Optical Society of America.

A broadly tunable master-oscillator power-amplifier (MOPA) picosecond optical pulse source is demonstrated, consisting of an external cavity passively mode-locked laser diode with a tapered semiconductor amplifier. By employing chirped quantum-dot structures on both the oscillator's gain chip and amplifier, a wide tunability range between 1187 and 1283 nm is achieved. Under mode-locked operation, the highest output peak power of 4.39 W is achieved from the MOPA, corresponding to a peak power spectral density of 31.4 dBm/nm. © 1989-2012 IEEE.

In this paper, we present the generation of high peak-power picosecond optical pulses in the 1.26 μm spectral band from a repetitionrate- tunable quantum-dot external-cavity passively mode-locked laser (QDECMLL), amplified by a tapered quantum-dot semiconductor optical amplifier (QD-SOA). The laser emission wavelength was controlled through a chirped volume Bragg grating which was used as an external cavity output coupler. An average power of 208.2 mW, pulse energy of 321 pJ, and peak power of 30.3 W were achieved. Preliminary nonlinear imaging investigations indicate that this system is promising as a high peakpower pulsed light source for nonlinear bio-imaging applications across the 1.0 μm - 1.3 μm spectral range. © 2012 Optical Society of America.

In this paper, we numerically investigate the role of gain and absorber dynamics on the operation of monolithic two-section mode-locked quantum-dot lasers under optical feedback. The analysis is carried out by means of a time-domain traveling wave model for propagation in the gain and absorbing sections. The obtained results indicate that in devices with slow dynamics, pulse duration tends to increase significantly with feedback. On the contrary, devices with fast dynamics exhibit an operation that depends primarily on the external cavity length. © 2012 IEEE.

The relation between the structural parameters and the operating characteristics of microring lasers is examined through theoretical estimations, waveguiding simulations, and experimental measurements. The effects of ring radius, waveguide profile, and overall geometry on the coupling efficiency and subsequently on threshold and spectral characteristics are thoroughly investigated. Coupling efficiency is calculated through 3-D finite difference in time domain methods. Fabricated devices consist of active microrings integrated with passive bus waveguides using wafer bonding techniques.

An adaptive interrogation technique that employs integrated semiconductor micro-ring resonators (MRR) for fast-response sensing applications is proposed and numerically studied. The basic sensing scheme consists of two MRRs in an add/drop signal configuration; the first MRR plays the role of the measuring sensor, while the second one acts as a reference optical filter that converts any frequency shift induced in the spectral characteristics of the measuring sensor into optical power variations. The proposed photonic sensor has the potential to adjust its transfer function dynamically, due to the varying response of the MMRs to different operating conditions, exhibiting either an ultra-low resolution operation capable of detecting extremely small refractive index changes, or an operation with a wide dynamic range. Finally, we propose a more sophisticated approach for simultaneous interrogation that incorporates multiple MRR sensors, based on thermal heaters that modulate the response of each MRR sensor with different modulation frequencies. In contrast to the conventional interrogation techniques, the proposed configurations enable ultra-high sampling rates crucial for studying fast biochemical reactions, such as enzyme kinetics. © 2011 IEEE.

In this paper, we present experimental results related to tunable dual wavelength passive mode locking of two independent ground state sub-bands in a multi section InAs/InGaAs quantum dot laser. The emission of these sub-bands is related to gain suppression at the center of the ground state emission, whereas their wavelength separation is tunable with injection current. Through the mechanism of passive mode locking two independent pulses were obtained, with typical pulse width in the order of 17 ps. © 2011 American Institute of Physics.

The relation between the structural parameters and the operating characteristics of microring lasers is examined through theoretical estimations, waveguiding simulations, and experimental measurements. The effects of ring radius, waveguide profile, and overall geometry on the coupling efficiency and subsequently on threshold and spectral characteristics are thoroughly investigated. Coupling efficiency is calculated through 3-D finite difference in time domain methods. Fabricated devices consist of active microrings integrated with passive bus waveguides using wafer bonding techniques. © 2011 IEEE.

We present an experimental study on the effect of optical feedback in both ground and excited emission of a GaAs quantum dot passively mode locked laser. The experimental setup consisted of a long external cavity with variable cavity length and feedback level ranging from -50 to -20dB. The obtained experimental results show dependence of the emission properties on the cavity length regarding both the ground and excited state. In addition a strong tolerance of the laser operation to feedback at the excited state operation regime is observed. © 2010 American Institute of Physics.

A novel biochemical sensing method is presented, relying on an optical microring resonator (MRR). The corresponding interrogation procedure based on the above method is suitable for highly sensitive optical phase detection. The proposed principle is related to the interaction of two optical inputs to the micro ring, which have a phase mismatch due to a biochemical event. This mismatch creates asymmetric and shifted mode resonances (Fano resonances) inside the microcavity, extending the inesse of the system. So as to evaluate the proposed scheme, a transfer matrix and a numerical model have been utilized. In order to detect the agent, a separate element is utilized which can be realized as a silicon waveguide monolithically integrated with the related components. © 2009 IEEE.

In this paper, the impact of the simultaneous presence of input and add signals in add/drop filters realized with microring resonators is numerically investigated. It is shown that the notch spectral response of output ports is responsible for the intraband crosstalk appearing on the dropped signals in add/drop operation. The investigation of the filter performance is performed with modulated signals at both the input and the add port. The analysis highlights the strong competition between the levels of induced intraband crosstalk and the wavelength selectivity at high bit rate add/drop operation, even in higher order filters. Multistage add/drop topologies that address the inefficiencies of the single-stage add/drop filters are proposed, and successful operation at 40 Gbps nonreturn to zero and return to zero signals is numerically demonstrated . © 2009 IEEE.

The dynamic operation of add-drop filters based on active microring cavities is numerically investigated for the first time to our knowledge, with high bit-rate return-to-zero (RZ) input signals at both the input and the add port. The use of an active ring cavity allows the complete loss compensation, which has been suggested in order to eliminate the intraband crosstalk between the incoming signals. Strong degradation of the dropped and added signals is observed due to the imperfect spectral response of the through and drop ports. A double-stage topology that addresses the inefficiencies of the single add-drop ring is proposed and the successful operation of 40-Gb/s RZ signals is numerically demonstrated. © 2007 IEEE.