Secure optical communications involve securing data transmitted over optical networks, primarily using technologies like optical encryption to protect data in transit. We have developed an optical steganography communication technique based on a quantum dot coherent comb laser, laser channels have strong correlated phase relationship. Each stealth channel uses two comb lines, which operates through two paired Mach-Zehnder interferometers. One line carries data, while the other serves as a reference. At the transmitter, phase modulation adds data to one comb line. An optical delay introduces a mismatch between the two lines to make the data undetectable to others. At the receiver, a programmable tunable delay matches the assigned delays from the different stealth channels. If the tunable delay matches the delay difference between the two-comb lines, the signal is recovered. The system uses physical-layer encryption instead of digital encryption to ensure robust security, scalability, and real-time data protection without computational processing.

In buried heterostructure (BH) lasers, leakage current becomes a problem at high input currents, wasting power and reducing optical efficiency. This article introduces an electrical model that represents the voltagecurrent (VI) characteristics of forward-biased BH lasers. This model can be used to explain and predict leakage current. It also gives a diagnostic tool to compare experimental BH lasers, using simple VI measurements. In this experiment, 72 BH lasers with three different mesa top layer doping levels were measured. Then, a curve fit was performed on the VI measurements using the proposed model, extracting the model parameters for each device. Nearly all the extracted model parameters, which were resistances and diode properties such as ideality factor and saturation current, had clear trends that help explain the impact of varying mesa top layer doping levels. The results showed, as discussed in previous literature, that high mesa top layer doping level reduces laser leakage current, but increases cavity loss. It was also found that by using only the fit on electrical characteristics, the model can roughly predict the measured drop in optical efficiency that the BH lasers experience at high input currents. The better understanding of leakage current that comes from this model can be used to further the development of BH lasers. As well, the model and curve fit can be used as a diagnostic tool to aid in the testing of these experimental devices.

The rapid expansion of global data, driven by advances in artificial intelligence and the increasing demand for reliable sensor performance in automotive and other technologies, is driving significant growth in the photonics market. Laser longevity and stability are essential for these applications, and while design improvements can extend device lifetime, success ultimately requires an optimized fabrication process. The Canadian Photonics Fabrication Centre has developed an advanced in-situ cleaning technique that significantly enhances the lifetime of buried heterostructure lasers, achieving up to an order-of-magnitude improvement. Furthermore, for any laser design, precise control and execution of doping techniques are essential to realizing high performance. This presentation will demonstrate that design excellence alone cannot deliver reliable, high-performance photonic devices—it must be complemented by excellence in fabrication.

Microwave photonics (MWP) represents a significant optical signal processing system, standing at the confluence of microwave engineering and photonics. It presents a promising way for meeting the growing demands of contemporary communication systems, radar, sensing, and signal processing. Driving the rapid advancement of MWP are pivotal technologies such as optical frequency combs, photonic integrated circuits, and advanced modulation formats. The integration of photonic integrated circuit technology with hybrid integration techniques holds the promise of realizing MWP systems on a single chip, while comb shaping technology endows MWP systems with programmable and reconfigurable capabilities. In this paper, we present a review of our recent research, which focused on exploring the full spectrum of potential applications for quantum dash lasers in MWP systems. Leveraging principles of finite impulse response filters, our MWP system not only facilitates conventional filtering but also enables instantaneous frequency measurement and waveform generation. A distinguishing feature of MWP filters is their uniform delay. After converting it into a uniform phase difference, it underpins the development of MWP-based phase antenna array systems. Furthermore, this uniform delay finds application in time-interleaved photonic analog-to-digital conversion.

This paper demonstrates an InAs/InP quantum-dash semiconductor optical amplifier (QD-SOA) with 20.2dB gain and 6.08dB noise figure which has less gain competition. The steady state gain competition of QD-SOA is measured and compared with EDFA, which is significantly lower.

Microwave photonic (MWP) signal processing offers the advantage of large time-bandwidth capability to overcome the inherent limitations of electronic systems. Optical frequency combs (OFC), providing many wavelengths, are particularly useful for transversal filter systems, while quantum-dash mode-locked lasers (QD-MLL), known for their ability to generate flat OFCs with low power consumption and simple operation, are promising candidates as the OFC sources. Here, we demonstrate for the first time a versatile MWP signal processor using a QD-MLL that generates an OFC with 49 comb lines and a free spectral range of 25 GHz. By tailoring the OFC spectrum, the MWP signal processor can be reconfigured to perform a variety of functions, including integral and fractional Hilbert transform (HT), differentiator, and integrator, with operation bandwidths of 7.5 GHz, 20 GHz, and 25 GHz, respectively. Owing to the large number of comb lines, the proposed HT exhibits small amplitude and phase and ripples, which are +/- 1.66 dB and +/- 6.2 degrees, respectively, for integral HT. We also simulate the time-domain response for the different signal-processing functions based on the measured frequency responses. Our simulation and experimental results show that the QD-MLL is a promising OFC source for developing a high-speed, reconfigurable MWP processing engine.

Semiconductor lasers present several challenges in terms of both design and understanding. Their numerous epitaxial layers, material properties, and physical structures generate a complex and high-dimensional space of parameters that must be optimized. We develop and demonstrate the use of a computational model capable of exploring this high-dimensional space. We validate this model against experimentally obtained data to ensure high-quality inputs are generated for use in future machine learning analyses.

We demonstrate on a series of C-Band and L-band quantum dash (QD) semiconductor optical amplifiers (SOAs) with different numbers of QD stacked layers. The overall preformation was investigated. The small-signal gain and noise figure were obtained at about 26.4 dB and 6.3 dB, respectively, at 1550 nm. Less gain competitions were observed from our QD-SOAs comparing to EDFA. The QD-SOAs were verified in a millimeter-wave (mmW) radio-over-fiber (RoF) fronthaul wireless link with 24-Gb/s (64QAM 4GBaud).

Photonics offers a transformative approach to artificial intelligence (AI) and neuromorphic computing by enabling low-latency, high-speed, and energy-efficient computations. However, conventional photonic tensor cores face significant challenges in constructing large-scale photonic neuromorphic networks. Here, we propose a fully integrated photonic tensor core, consisting of only two thin-film lithium niobate (TFLN) modulators, a III-V laser, and a charge-integration photoreceiver. Despite its simple architecture, it is capable of implementing an entire layer of a neural network with a computational speed of 120 GOPS, while also allowing flexible adjustment of the number of inputs (fan-in) and outputs (fan-out). Our tensor core supports rapid in-situ training with a weight update speed of 60 GHz. Furthermore, it successfully classifies (supervised learning) and clusters (unsupervised learning) 112 * 112-pixel images through in-situ training. To enable in-situ training for clustering AI tasks, we offer a solution for performing multiplications between two negative numbers.

Future mobile and terrestrial communication systems B5G/6G are strongly expected to heterogeneously realize typically diversified performances, i.e. high-data-rate, high-mobility, low-latency, high-capacity, massive-connectivity and low-energy in order to satisfy the highly diversified application requirements. To achieve those goals the operation band of B5G/6G should be primarily in the millimeter-wave (mmW) range. Generation and distribution of mmW with traditional methods is limited by electronic bottleneck and associated complexity. Consequently broad bandwidth, simple, efficient, and cost-effective photonic mmW-over-fiber (mmWoF) transmission systems are solutions for B5G/6G. The spectral purity of mmW carriers is necessary. Numerous approaches have been proposed to generate pure mmW signals. Compared with other technologies, quantum dash or dot (QD) coherent comb lasers (QD CCLs) have great advantages for mmW generation because QD-CCLs with low power consumption and chip-scale integration capacity with silicon can provide multiple highly correlated and low noise optical channels. In this paper we will present our developed InAs/InP QD-CCLs around 1550 nm with the channel spacing from 10 GHz to 1000 GHz and the output power up to 50 mW. By using a C-band QD CCL and based on the single- and dual-optical carrier modulation schemes, an up to 16-Gb/s mmWoF optical heterodyne wireless signal at 28 GHz through a 25-km single mode fiber before the mmW carrier is optically synthesized remotely for detection over a 2-m free space. The data capacity and performance of the proposed mmWoF link can be significantly increased by utilizing a duplex mmWoF link with MIMO and WDM technique, which provides a cost-efficient and promising solution for Terabit/s capacity mmWoF fronthaul systems of B5G/6G networks.

We present the theory and experimental results of a microwave photonic (MWP) filter based instantaneous frequency measurement system. A quantum dash mode-locked laser is used as an optical frequency comb source. With up to 41 flat comb lines and a real-time feedback loop for comb shaping, a set of MWP filters with linear frequency responses for either linear unit or dB unit are experimentally demonstrated. The maximum measurement frequency can be up to 20 GHz limited by the available test-and-measurement instruments. By using one MWP filter, the root-mean-square error is 51∼66 MHz, which can be improved to 42.2 MHz for linear unit, and 30.7 MHz for dB unit by using two MWP filters together.

In this work, we have investigated self-injection locking effects on a full spectral system with selective single-channel injection and full-channel injection in a quantum dot mode-locked comb laser through an optical feedback loop. It has been noticed that self-injection locking can not only improve the performance of a single-channel laser system but also has a strong effect on the whole spectral behavior. In the case of single-channel self-injection, we investigated the effects under a locked regime above the injection-locking threshold P-SIL. The locked lines were strongly enhanced with intensities high above the broad spectrum and also intensified even outside of the original spectral bandwidth. The typical feature is a big dip (or hole) appearing on the high-energy side of the lines if it is within the free-running spectral region. We have investigated this asymmetric phenomenon. It is considered that the locked modes are highly intensified at the expense of higher energy carriers excited by currents. The locking process transferred the energy from the lasing mode to the locked mode. For the full channel self-injection, the system was set under a controllable self-injection locking condition. A bandwidth enhancement phenomenon can be observed when injected power reaches the self-injection locking threshold P-SIL, and the broadening gets stronger till to the locked regime. Finally, the original spectral bandwidth had been significantly broadened. This bandwidth broadening goes to both sides of the free-running spectrum and the broadening is remarkable.

We will present different-type InAs/InP quantum dot (QD) coherent comb lasers (CCLs) and semiconductor optical amplifiers (SOAs) around 1550 nm with their detailed technical specifications. By using those QD-CCLs and -SOAs, we have experimentally demonstrated bi-directional millimeter-wave-over-fiber wireless fronthaul transmission links and optical superchannel coherent systems, which have clearly indicated that both QD-CCLs and -SOAs are critical building blocks of achieving broadband and high speed converged optical and wireless access network systems.

We present an approach for microwave photonic (MWP) arbitrary waveform generation utilizing a quantum dash optical frequency comb source. Leveraging the availability of up to 41 comb lines and incorporating a real-time control feedback loop for precise comb shaping, we design a suite of MWP filters. Through the introduction of an ultra-short RF train, we obtain the impulse responses of the MWP filters, facilitating the construction of a versatile MWP arbitrary waveform generation system. In this study, we showcase the generation of rectangular, triangular, and sine burst waveforms. We can achieve an accuracy exceeding 90% in our generated waveform compared to the target waveform. Additionally, we demonstrate the tunability of the pulse width of rectangular and triangular waveforms, ranging from 0.62 ns to 4.56 ns, along with the adjustability of the triangular waveform slope. By manipulating the delay of the MWP filter, our system can also generate sine bursts, periodic sinusoids, and sinusoids with envelopes, with clock frequencies lower than that of the sinusoid itself.

We present results from monolithic QDot MLLs with SOA for mmW signal generation and transmission. Fabricated from identical InAs/InP QDot materials, these devices pave the way for advanced photonic chips with integrated MLL-OFCs, SOAs, and other components.

An optical self-injection-locking feedback loop is designed for quantum-dot coherent-comb lasers to reduce linewidth, achieving significant linewidth reduction from 5.958MHz to 3.483kHz and maximum 35dB intensity enhancement, providing promising potential for diverse applications.

In this work, we demonstrate the establishment of a self-injection locking threshold in a quantum dot (QD) comb laser with a Fabry-Perot cavity and an external feedback loop. This process involves controlling injection power and polarization to inject a controlled fraction of lasing power back into the QD laser source. The study is focused on the single line self-injection locking effects. The self-injection locking process was characterized by a self-injection locking threshold power (PSIL) and a locked power (Plocked). The self-injection locking process begins from the threshold power PSIL and followed by a magnified enhancement till it reaches the locked power (Plocked). Once in the locked region, the enhancement effect starts to stabilize and is only weakly influenced by injection power. The established threshold provides a distinctive condition for the measurements of the modified optical properties of the coupled cavity system. Additionally, the locked single lines tested at different currents indicated a very broad spectral coverage which are much larger than the original bandwidth of free running QD laser.

This paper demonstrates a five-layer InAs/InP quantum-dash semiconductor optical amplifier (QDash-SOA), which will be integrated into microwave-photonic on-chip devices for millimeter-wave (mmWave) over fibre wireless networking systems. A thorough investigation of the QDash-SOA is conducted regarding its communication performance at different temperatures, bias currents, and input powers. The investigation shows a fibre-to-fibre (FtF) small-signal gain of 18.79 dB and a noise figure of 6.3 dB. In a common application with a 300 mA bias current and 25 °C temperature, the peak FtF gain is located at 1507.8 nm, which is 17.68 dB, with 3 dB gain bandwidth of 56.6 nm. Furthermore, the QDash-SOA is verified in a mmWave radio-over-fibre link with QAM (32 Gb/s 64-QAM 4-GBaud) and OFDM (250 MHz 64-QAM) signals. The average error vector magnitude of the QAM and OFDM signals after a 2 m wireless link could be as low as 8.29% and 6.78%, respectively. These findings highlight the QDash-SOA’s potential as a key amplifying component in future integrated microwave-photonic on-chip devices.

This paper presents a photonic analog-to-digital converter (ADC) tailored for RF and mmWave signals, featuring down-conversion to intermediate frequency (IF) to reduce bandwidth requirements for the photodetector (PD) and ADC sampling rate. Demonstrating an operational range of 18-32 GHz, including the 5G NR band, the system achieves a maximum effective number of bits (ENOB) of 11, limited by the performance of hardware. The ADC effectively detects various RF/mmWave communication signals with a 7.5 GHz PD and 12.5 GS/s sampling rate, showing potential for higher frequency applications and complex modulation formats in modern communication systems.