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Pavlovian associative learning, a form of classical conditioning, has significantly impacted the development of psychology and neuroscience. However, the realization of a prototypical photonic neural network (PNN) for full-function Pavlov associative learning, encompassing both photonic synapses and photonic neurons, has not been achieved to date. In this study, we propose and experimentally demonstrate the first InP-based full-function Pavlov associative learning PNN. The PNN utilizes semiconductor optical amplifiers (SOAs) as photonic synapses and the distributed feedback laser with a saturable absorber (DFB-SA) as the photonic spiking neuron. The connection weights between neurons in the PNN can be dynamically changed based on the fast, time-varying weighting properties of the SOA. The optical output of the SOA can be directly coupled into the DFB-SA laser for nonlinear computation without additional photoelectric conversion. The results indicate that the PNN can successfully perform brain-like computing functions such as associative learning, forgetting, and pattern recall. Furthermore, we analyze the performance of PNN in terms of speed, energy consumption, bandwidth, and cascadability. A computational model of the PNN is derived based on the distributed time-domain coupled traveling wave equations. The numerical results agree well with the experimental findings. The proposed full-function Pavlovian associative learning PNN is expected to play an important role in the development of the field of photonic brain-like neuromorphic computing. [ABSTRACT FROM AUTHOR]

A novel high-speed directly modulated two-section distributed-feedback (TS-DFB) semiconductor laser based on the detuned-loading effect is proposed and simulated. A grating structure is designed by the reconstruction-equivalent-chirp (REC) technique. A π phase shift is introduced into the reflection grating, which can provide a narrow-band reflection region with a sharp falling slope on both sides of the reflection spectrum, thus enhancing the detuned-loading effect. Owing to its unique dual-falling-edges structure, the bandwidth can be improved even when the lasing wavelength shifts beyond the left falling edge due to a thermal effect in the actual test, in which condition the detuned-loading effect can be used twice, which greatly improves the yield. The modulation bandwidth is increased from 17.5 GHz for a single DFB laser to around 24 GHz when the lasing wavelength is located on the left falling edge of the TS-DFB laser based on the detuned-loading effect, and it can be increased to 22 GHz for the right side. An eight-channel laser array with precise wavelength spacing is investigated, with a side-mode suppression ratio (SMSR) >36 dB. In addition, TS-DFB lasers with uniform reflection gratings are studied, and simulated results show that the modulation characteristic is far inferior to the laser with a phase-shifted grating reflector. [ABSTRACT FROM AUTHOR]

The tunable laser based on distributed feedback (DFB) laser array has a good single-longitudinal-mode property, high wavelength stability, narrow spectrum linewidth, and feasibility for monolithic integration. The tunable in-series DFB laser array (TIDLA) was proposed to avoid the large extra power loss by the optical combiner. But in the TIDLA, a large laser count will cause a large chip length, which brings about low utilization ratio of material, poor mechanical strength, and large power consumption. In this paper, we demonstrated a 4-channel TIDLA with duplex DFB sections. The total chip length was greatly shortened owing the duplexing of DFB sections. A long linearly chirped Bragg grating is implemented in the laser cavity to reduce the grating interference among different lasers. Multiple π phase shifts and two reflector sections are introduced to improve the mode stability. The designed channel spacing is 100 GHz, and the reconstruction-equivalent-chirp technique is used to provide high precision control of the grating phase. Noted that a variation of 0.1 nm in grating period will cause that of 0.65 nm in wavelength. Output power of above 4 mW, SMSR of above 42 dB, and small wavelength deviation of within 0.15 nm was obtained. Besides, fast channel switches of less than 1 μs are obtained by laser on/off switching. The proposed TIDLA might be applied in the NG-PON2 network where the dense wavelength division multiplexing technique and fast channel switching are required. [ABSTRACT FROM AUTHOR]

We propose and experimentally demonstrate a high-power eight-wavelength distributed feedback (DFB) laser array with 100 GHz spacing using the grating reflector (GR). The GR, which is a uniform sampled grating, can provide light reflection instead of high reflection (HR) facet coating. Thus, the front and rear facets are both coated with anti-reflection coatings (AR/AR) to avoid the influence of a random grating phase at the HR facet. Therefore, more output power, better single-longitudinal-mode operation, and higher wavelength precision can be simultaneously achieved, compared with traditional DFB lasers with HR/AR facet coatings. The maximum output power and side mode suppression ratio of the fabricated eight-channel GR-DFB laser array as high as 70 mW and 55 dB can be achieved, which may benefit wavelength division multiplexing transmission systems, gas sensors, optical computing systems, and microwave photonic signal processing. [ABSTRACT FROM AUTHOR]

Multi-wavelength distributed feedback laser array (DFB-MLA) based tunable semiconductor lasers have been widely used owing to the high mode stability and simple wavelength tuning scheme. In this paper, we proposed and experimentally demonstrated a matrix-grating tunable DFB laser array. And the reconstruction-equivalent-chirp (REC) technique is utilized to simplify grating fabrication and realize precise control of the grating phase. Traditionally, the laser is tuned by thermal-electric cooler (TEC), with large power consumption, slow wavelength tuning capability, and added device. To improve the wavelength tuning speed of laser, we varied laser’s injection current instead of adjusting TEC’s temperature. In addition, we analyzed the thermal influence of submount on the laser and then chose the SiO2 as the submount material for its low thermal conductivity and poor heat dissipation, resulting in wide wavelength tuning range via injection current. The DFB-MLA chip achieves a better tunable effect as the lasers can be tuned at 3.5–3.7 nm per channel from 50 to 120 mA with stable output power of over 3 mw as contrasted with the laser on the AlN submount being tuned at 1.4–1.5 nm per channel. And the chip has a side-mode suppressing ratio (SMSR) of over 35 dB and strong stability of wavelength in the repeated experiments. The proposed method may give a new way to realize the wide tuning range tunable DFB laser with a simple wavelength tuning mechanism in the future, especially for the applications of uncooled low-cost tunable lasers. [ABSTRACT FROM AUTHOR]

We propose a new kind of distributed feedback (DFB) semiconductor laser based on the sampled Moiré grating (SMG) integrated with a grating reflector (GR). Coupling coefficient along the laser cavity can be controlled, and $\pi $ phase shift ($\pi $ -PS) can be introduced by SMG. The GR, which is a uniform sampled grating, can provide light reflection instead of high reflection (HR) facet coating. Thus, the front and rear facets are both coated with anti-reflection coatings (AR/AR) to avoid the influence of random grating phase at the HR facet. Therefore, more output power, better single longitudinal mode (SLM) operation, and higher wavelength precision can be simultaneously achieved, compared with traditional DFB lasers with AR/HR facet coatings. As an example, an 8-channel DFB laser array based on the proposed structure has been simulated. The proposed laser may benefit the applications requiring both high output power and wavelength precision, such as wavelength division multiplexing (WDM) transmission systems and gas sensors. [ABSTRACT FROM AUTHOR]

A broadband chromatic dispersion (CD) compensation scheme using optical phase conjugation (OPC) based on a DFB semiconductor laser is proposed and experimentally demonstrated in analog photonic links (APLs). The DFB laser acts as a nonlinear medium to induce four-wave mixing and a pump laser simultaneously. Compared with the conventional OPC based on a semiconductor optical amplifier or a dispersion-shifted fiber, an extra pump laser is no longer required. Experimental results show that the power fading caused by the CD in a 50.4-km APL can be compensated with a 3-dB bandwidth up to 33 GHz. Meanwhile, the spur-free dynamic range is enhanced with 12.6 \textrm dB\cdot \textrm Hz^2/3 ; the transmission performance is also improved. [ABSTRACT FROM PUBLISHER]

A wideband frequency-tunable optoelectronic oscillator using four-wave mixing nonlinear dynamics of an optical-injected distributed feedback (DFB) semiconductor laser is proposed and experimentally demonstrated. Utilizing the wavelength-selective optical gain of the DFB laser under optical injection, a frequency-tunable microwave photonic filter is realized, which is used as the desired oscillation frequency selector. Therefore, the electrical bandpass filter is not required in the proposed scheme. An optoelectronic oscillating signal with a frequency tuned from 9.63 to 19.11 GHz is obtained by changing the injection parameters. The single sideband phase noise of the generated 13.74-GHz microwave signal is measured to be −103.19 dBc/Hz at 10-kHz offset. [ABSTRACT FROM PUBLISHER]

ABSTRACT A distributed-feedback semiconductor laser array with buried heterostructure waveguide based on reconstruction equivalent chirp technique is experimentally demonstrated. The fabricated six-element laser array has channel spacing of 800 GHz and well meets the International Telecommunication Union standard, with relatively low threshold and high efficiency. Good single-longitudinal mode operation has been achieved at high injection current (120 mA) and high temperature (80°C), with side mode suppression ratios not lower than 40 dB, which is promising for the future wavelength division multiplexing systems. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1278-1281, 2015 [ABSTRACT FROM AUTHOR]

A wideband tunable single bandpass microwave photonic filter (MPF) based on the four‐wave mixing (FWM) nonlinear dynamics of a distributed feedback (DFB) semiconductor laser under optical injection is proposed and experimentally demonstrated. Utilising the wavelength‐selective optical gain of the optical‐injected DFB laser, phase‐modulation to intensity‐modulation conversion is obtained, leading to the realisation of a single bandpass MPF. By changing the injection parameters, an MPF with a frequency tuning range of 27.72 GHz has been achieved. The minimum 3 dB bandwidth and the out‐of‐band suppression ratio are measured to be 61.2 MHz and 25 dB, respectively. [ABSTRACT FROM AUTHOR]

A low-cost tunable semiconductor distributed feedback (DFB) laser design in access networks is proposed and experimentally demonstrated. It covers 9 nm continuous tuning range by changing the temperature. The side mode suppression ratios are above 42 dB over the tuning range. The current and temperature coefficients of wavelength tuning are 0.0124 nm mA−1 and 0.0875 nm °C, respectively. The results indicate that the reconstruction-equivalent-chirp (REC) technique is promising to fabricate low-cost tunable DFB lasers meeting the requirement of wavelength-division-multiplexing passive optical networks (WDM-PONs). It should be also noted that the tuning range can be easily extended by using more sections. [ABSTRACT FROM AUTHOR]

To assess the impact of Doppler frequency shift and channel crosstalk on the performance of a four-channel free-space optically switched communication network, particularly in scenarios involving low Earth orbit satellites, we derived a bit error rate model under the influence of satellite-ground Doppler frequency shift and channel crosstalk in atmospheric turbulence. This model focuses on studying a four-channel distributed feedback (DFB) laser array through numerical simulation. We initially analyzed the effect of crosstalk on the system's switching time in the absence of Doppler frequency shift. Our research revealed that as the channel spacing increased, the impact of crosstalk on the system's optical switching time decreased. We utilized a primary power compensation solution, adjusting the output optical power for different channel spacings, to mitigate the influence of crosstalk on the system's switching time. After eliminating the effects of crosstalk, we further examined the impact of Doppler frequency shift on the system's switching time for different channel spacings. We proposed a secondary power compensation solution to mitigate the effects of both crosstalk and Doppler frequency shift on the system's switching time. Finally, through simulation experiments, we set the output optical power of the laser to 10.42mw when switching from channel 1 to channel 2, 9.05mw when switching from channel 1 to channel 3, and 8.68mw when switching from channel 1 to channel 4, ensuring a uniform switching time of 10ns. Our research results provide a solid theoretical foundation for enhancing the performance of free-space optically switched communication networks and for mitigating the impact of Doppler frequency shift on system switching time. [ABSTRACT FROM AUTHOR]

Metalens have the advantages of ultra-thin, low loss, easy integration and flexible phase control mechanism, which have attracted intensive attention in the field of on-chip photonic chips. By designing Si nanocylinder meta-atom on SiO 2 substrate, the structure size is optimized to achieve the optimal light transmittance and phase change covers the range of 2π. In order to achieve the effect of coupling Distributed Feedback Laser (DFB) array into a fiber, it is necessary to accurately arrange the above optimized Si nanocylinder according to a certain phase profile to achieve the effect of off-axis focusing. Here, we designed an off-axis focusing metalens array to efficiently couple the parallel 4-channel DFB laser array into the few-mode fiber (FMF), and the total coupling efficiency reaches 56.48 %. This result provides a new idea for compact, low loss on-chip light sources. • A novel and reliable low loss laser array combining scheme is proposed. • An off-axis focusing metalens array is designed for multi-channel laser combining. • The combiner has the advantages of high integration, low loss, polarization insensitivity, and mode insensitivity. • In the parallel 4-channel laser array, the metalens array exhibits a coupling efficiency of 56.48 %. • The loss of the proposed combiner does not increase with the increase of the laser channels number. [ABSTRACT FROM AUTHOR]

• The quarter-wavelength-shifted DFB laser is firstly reported to generate optical chaos. • Two paths of complex optical chaotic signals with a bandwidth above 10 GHz are simultaneously generated using just one laser diode. • A parallel physical random number generator (Ph-RNG) with a bit rate of 1.04 Tbps/channel is realized. We propose and experimentally demonstrate a parallel physical random number generator (Ph-RNG) based on a single quarter-wavelength-shifted distributed feedback laser (QWS-DFB LD). Though simply connecting the two output ports of the QWS-DFB LD to form a cross-coupled perturbation, we simultaneously produce two paths of complex optical chaotic signals with a bandwidth above 10 GHz. Furthermore, a dual-channel Ph-RNG with a bit rate of order terabit per second (Tbps) is implemented by combining a multi-bit extraction method. Final results show that our generated physical random numbers can successfully pass standard benchmark tests for randomness. [ABSTRACT FROM AUTHOR]

In this paper, a strain sensing system based on Distributed-Feedback (DFB) laser array and a high effective demodulate algorithm is proposed. The uniqueness and innovation of the algorithm is in the following two aspects: one is that accurate demodulation can be achieved by scanning only 0.4 nm bandwidth of fiber Bragg grating (FBG) spectrum instead of relying on scanning FBG’s principal power peak; and the other is that the scanned spectrum can be any part of reflected spectrum of FBG sensor, which make it possible of using wavelength-division multiplexing (WDM) for FBG sensing network. In the experiment, DFB laser array with single-channel and four-channel are used to demonstrate the proposed algorithm. Experiments results show that the single-channel’s error is below 5 pm, four-channel’s is below 2 pm, strain and algorithm results show good linearity. [ABSTRACT FROM AUTHOR]

The tunable distributed feedback (DFB) semiconductor lasers with cascaded configuration were designed and fabricated using equivalent phase shift (EPS) technique. 32-wavelength division multiplexing (WDM) channels with 50-GHz and 100-GHz wavelength spacing were experimentally demonstrated. In such a tunable laser, single mode operation can be ensured by introducing EPS and the wavelength tuning can be realized by cascaded sections with specific sampling periods combining with chip heating. The proposed approach has some advantages such as good single mode property, low fabrication cost and feasibility of monolithic integration. The experimental results show that the tuning range can be nearly up to 25 nm and the side mode suppression ratios (SMSRs) of most channels are above 40 dB. The proposed laser should be promising for cost-effective applications in WDM systems. [ABSTRACT FROM AUTHOR]

An equivalent corrugation pitch-modulated (ECPM) distributed feedback (DFB) semiconductor laser with two equivalently assisted phase shifts (EAPS) was theoretically studied and experimentally demonstrated. The simulated results showed that the longitudinal photon density distribution of the ECPM + EAPS DFB lasers was much more uniform than that of a sole ECPM DFB laser without EAPS, and the longitudinal spatial hole burning was therefore suppressed more effectively. The results of experiment showed that good single longitudinal mode operation was achieved, with side mode suppression ratio (SMSR) being over 35 dB, and the wavelength range was from 1,559.64 to 1,563.02 nm when the operation current was from 50 to 160 mA at the temperature of 25 °C, and the SMSR increased to 46.29 dB when the injection current was 130 mA. [ABSTRACT FROM AUTHOR]

Abstract: The phase-shifted distributed feedback (DFB) semiconductor laser with linearly chirped grating based on reconstruction equivalent chirp (REC) technique is theoretically analyzed and experimentally demonstrated for the first time. The asymmetric property of the lasing spectrum is analyzed according to the normalized threshold gain, and the different spectra from each facet of the laser are compared. Due to the low cost and fabrication flexibility, REC technique provides a promising way for the future practical applications of DFB lasers with chirped gratings. [Copyright &y& Elsevier]

Packaging of distributed feedback (DFB) laser array based on reconstruction-equivalent-chirp (REC) technology is a bridge from chip to system, and influences the practical process of REC chip. In this paper, DFB laser arrays of 4-channel @1310nm and 8-channel @1550nm are packaged. Our experimental results show that both these laser arrays have uniform wavelength spacing and larger than 35dB average Side Mode Suppression Ratio (SMSR). When I=35mA, we obtain the total output power of 1mW for 4-channel @1310nm, and 227μw for 8-channel @1550nm respectively. The high frequency characteristics of the packaged chips are also obtained, and the requirements for 4×10G or even 8×10G systems can be reached. Our results demonstrate the practical and low cost performance of REC technology and indicate its potential in the future fiber-to-the-home (FTTH) application. [ABSTRACT FROM AUTHOR]