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(a) A cross sectional SEM image of the five-layer InAs/InP QDlaser core region and (b) a detailed structure for a single InAs/InP dot layer.
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We have developed an InAs/InP quantum dot (QD) C-band coherent comb laser (CCL) module with actively stabilized absolute wavelength and power, and channel spacing of 34.462 GHz with ± 100 ppm accuracy. The total output power is up to 46 mW. The integrated average relative intensity noise (RIN) values of the lasing spectrum and a filtered single cha...
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We have used an external cavity self-injection feedback locking (SIFL) system to simultaneously reduce the optical linewidth of over 39 individual wavelength channels of an InAs/InP quantum dot (QD) coherent comb laser (CCL). Linewidth reduction from a few MHz to less than 200 kHz is observed. Measured phase noise spectra clearly indicate a signifi...
Citations
... The most common family of devices used for the generation of wideband optical frequency combs are mode-locked lasers which emit short optical pulses by setting a fixed phase relationship between many lasing longitudinal modes [1,8]. The semiconductor laser-based frequency combs are a simple and low-cost solution with potential for use in photonic integrated circuits (PICs), exhibit a broad range of emission wavelengths, and have been demonstrated for a variety of laser technologies such as quantum well [9,10], quantum dot [11][12][13], quantum dash [14,15], and quantum cascade lasers [16]. Special attention has been drawn on quantum dot/dash combs as they promise ultrabroad gain bandwidth and ultrafast carrier dynamics, low threshold, low spontaneous emission rate, as well as large gain and saturable absorber saturation energy ratio, a critical parameter for the implementation of high-performance mode-locked lasers [17]. ...
We experimentally investigate the unidirectional coupling between two semiconductor frequency combs generated by two passively mode-locked quantum dot lasers. We show that synchronization of the combs in terms of repetition rate and phase locking is possible for a wide range of detuning between the combs. Repetition rate locking of the combs leading to reduced phase noise operation for the slave comb can occur independently of phase locking. Furthermore, we study the synchronization with respect to specific features of the two lasers, such as the optical bandwidth, the peak wavelength mismatch, and the injected power levels.
... An alternative method of stabilising the absolute frequency/wavelength of a comb generator [235] involves using (electrically) active wavelength locking with a stabilised narrowband optical filter (etalon) used to determine the desired optical frequency of one of the modes. ...
Edge-emitting mode-locked quantum-dot (QD) lasers are compact, highly efficient sources for the generation of picosecond and femtosecond pulses and/or broad frequency combs. They provide direct electrical control and footprints down to few millimeters. Their broad gain bandwidths (up to 50 nm for ground to ground state transitions as discussed below, with potential for increase to more than >200 nm by overlapping ground and excited state band transitions) allow for wavelength-tuning and generation of pico- and femtosecond laser pulses over a broad wavelength range. In the last two decades, mode-locked QD laser have become promising tools for low-power applications in ultrafast photonics. In this article, we review the development and the state-of-the-art of edge-emitting mode-locked QD lasers. We start with a brief introduction on QD active media and their uses in lasers, amplifiers, and saturable absorbers. We further discuss the basic principles of mode-locking in QD lasers, including theory of nonlinear phenomena in QD waveguides, ultrafast carrier dynamics, and mode-locking methods. Different types of mode-locked QD laser systems, such as monolithic one- and two-section devices, external-cavity setups, two-wavelength operation, and master-oscillator power-amplifier systems, are discussed and compared. After presenting the recent trends and results in the field of mode-locked QD lasers, we briefly discuss the application areas.
... In comparison, semiconductor MLLs have the advantages of being electrically driven, while not requiring external high-power optical pumping, which makes them a great candidate for highly efficient, small-footprint, and low power consumption solutions for optical timedivision multiplexing [10] and wavelength-division multiplexing (WDM) systems [11]. In recent years, there has been significant attention paid to quantum dash (Q-dash) [12][13][14] and quantum dot (QD) MLLs [9,15,16] as flat-top comb sources, due to their properties of small linewidth enhancement factor, fast carrier dynamic-induced self-frequency modulation, and defect insensitivity, which make them an ideal platform for a reflection insensitive [17,18], temperature insensitive [19,20], and most importantly, direct-grown-on-Si light source [21][22][23][24][25][26]. ...
... For the extended time stability test that is also applied to a comb channel at 1317.69 nm, the wavelength variation is less than 1 GHz, as shown in the inset of Fig. 4(d). All the measurements are under free-running conditions, and it is believed that the combs can be further stabilized by the wavelength locker design with a feedback control loop [14]. ...
A quantum dot (QD) mode-locked laser as an active comb generator takes advantage of its small footprint, low power consumption, large optical bandwidth, and high-temperature stability, which is an ideal multi-wavelength source for applications such as datacom, optical interconnects, and LIDAR. In this work, we report a fourth-order colliding pulse mode-locked laser (CPML) based on InAs/GaAs QD gain structure, which can generate ultra-stable optical frequency combs in the O-band with 100 GHz spacing at operation temperature up to 100°C. A record-high flat-top optical comb is achieved with 3 dB optical bandwidth of 11.5 nm (20 comb lines) at 25°C. The average optical linewidth of comb lines is measured as 440 kHz. Single-channel non-return-to-zero modulation rates of 70 Gbit/s and four-level pulse amplitude modulation of 40 GBaud/s are also demonstrated. To further extend the comb bandwidth, an array of QD-CPMLs driven at separate temperatures is proposed to achieve 36 nm optical bandwidth (containing 60 comb lines with 100 GHz mode spacing), capable of a total transmission capacity of 4.8 Tbit/s. The demonstrated results show the feasibility of using the QD-CPML as a desirable broadband comb source to build future large-bandwidth and power-efficient optical interconnects.
... In recent years we have reported several InAs/InP QDot and QDash-MLLs operating in the Cand L-band with channel spacings from tens of GHz to THz [17,18,27,[37][38][39][41][42][43], focusing on the performance of QDash based lasers for high speed data communications. Compared to their QDash counterparts, it has been suggested that QDots are favorable for lasers as the improved height-diameter aspect provides a deeper confinement of the charge carriers [44]. ...
Chip-scale optical frequency comb sources are ideal compact solutions to generate high speed optical pulses for applications in wavelength division multiplexing (WDM) and high-speed optical signal processing. Our previous studies have concentrated on the use of quantum dash based lasers, but here we present results from an InAs/InP quantum dot (QDot) C-band passively mode-locked laser (MLL) for frequency comb generation. By using this single-section QDot-MLL we demonstrate an aggregate line rate of 12.544 Tbit/s 16QAM data transmission capacity for both back-to-back (B2B) and over 100-km of standard single mode fiber (SSMF). This finding highlights the viability for InAs/InP QDot lasers to be used as a low-cost optical source for large-scale networks.
... Thus, the received signal showed an eye-opening of 723 ps in the best case. Later reports on C-band Qdash MLL were towards either generation of MMW equivalent to the FP cavity FSR [89] or deployment in nonlinear phenomena applications [90] [91]. For instance, Qdash MLL was utilized in [90], where the comb of the 100 GHz FSR was used with a frequency-selective filter to provide two tunable wavelength pumps for wavelength conversion of optical channels in a dual-pump four-wave-mixing scheme. ...
... This work used Qdash MLL as a dual pump source for a wavelength conversion system. Next, another Qdot/Qdash MLLs were reported in [89], comprised of five layers and emitting in the C-band. By beating any consecutive modes of the comb lines of the Qdash MLLs, a high-quality beat tone of 34.46 GHz was generated. ...
The unprecedented increase in internet traffic witnessed in the last few years has pushed the community to explore heterogeneous optical networks, including free-space-optics (FSO) communication, radio-over-fiber (RoF), wireless (WL), and their convergent hybrid technologies. This stems from the possibility of seamless integration with the existing fiber-optic backhaul networks while providing much-needed flexibility and scalability. Moreover, efficient optical transceivers, particularly light sources in the form of semiconductor laser diodes, are key in meeting the future demands of the next generation green optical access networks. In this respect, InAs/InP Quantum-dash (Qdash) nanostructure-based lasers have shown tremendous progress in the past few years with applications spanning from a wavelength division multiplexed (WDM) optical communication to recently, millimeter-wave (MMW) over fiber networks. This waveguide-based laser diode (LD) has demonstrated a rule-changing broad multi-wavelength lasing emission, thanks to the inherent and wavelength-tunable wide gain profile offered by the Qdash active-gain region covering S- to U-band regions. Moreover, exploiting mode-locking and optical injection locking assisting techniques, highly coherent InAs/InP Qdash comb laser source at 1550 nm and 1610 nm have been respectively realized, thus opening a new paradigm for their potential applications in green optical and 5G access networks. In this work, progress on utilizing InAs/InP Qdash LD, supporting several sub-carriers, in energy-efficient ~1550 nm and ~1610 nm WDM heterogeneous optical networks with single-mode-fibers (SMF) has been highlighted, exhibiting aggregate data rates of 11 – 12 Tb/s by employing a single device, and accommodating PAM4 and higher-order 32-QAM modulation schemes. Moreover, the recent deployment of this LD in the RoF domain, targeting MMW frequency band, for convergent fiber-wireless networks, is also summarized, with demonstrated 25 to > 100 GHz MMW beat-tone frequency generates and transmission of up to 24 Gb/s.
... Other advantages include compact size, simple fabrication, and the ability for hybrid integration with silicon substrates [16]. In recent years we have successfully developed InAs/InP QD MWLs with repetition rates from 10 GHz to 437 GHz and a total output power up to 50 mW per facet at room temperature [17][18][19]. In this paper we give an overview of the performance of the QD MWLs and their applications in Terabit/s optical communication links and 5G wireless networks. ...
We report on the design, growth, fabrication, and performance of InAs/InP quantum dash (QD) multi-wavelength lasers (MWLs) developed by the National Research Council (NRC) Canada. The key technical specifications investigated include optical and RF beating spectra, relative intensity noise (RIN), and optical phase noise of each individual wavelength channel. Data bandwidth transmission capacity of 5.376 Tbit/s and 10.8 Tbit/s respectively in the PAM-4 and 16-QAM modulation formats are demonstrated using only a single C-band QD 34.2-GHz MWL chip. We have also developed a monolithic InAs/InP QD dual-wavelength (DW) DFB laser as a compact optical beat source to generate millimeter-wave (MMW) signals. Due to the common cavity, highly coherent and correlated optical modes with optical linewidth as low as 15.83 kHz, spectrally pure MMW signals around 46.8 GHz with a linewidth down to 26.1 kHz were experimentally demonstrated. By using this QD DW-DFB laser, a one GBaud (2 Gbps) MMW over-fiber transmission link is demonstrated with PAM-4 signals. The results show that the demonstrated device is suitable for high speed high capacity MMW fiber-wireless integrated fronthaul of 5G networks.
... As we will see in the next section, an important parameter for optical communication is the coherence of the comb lines. Compared to the electro-optic modulator where the linewidth RF beat note can be less than 1 Hz, the one of the quantum dot lasers has been found to range from several kHz to MHz [181]. ...
In this work, we study the nonlinear dynamics of laser diodes optically injected with frequency combs.We first theoretically and experimentally analyze the nonlinear dynamics of edge-emitting lasers (EELs) from an optical injection of frequency combs. The injection parameters and injected comb properties are varied to unveil several locked and unlocked dynamics. For large enough injection strength and over a large detuning range, the injection locking bifurcates to a time-periodic dynamics corresponding to an optical frequency comb that extends the injected comb to a much broader optical spectrum. A bifurcation analysis reveals a cascade harmonic frequency comb dynamics leading to a significant increase in the output comb lines. We have also used the injection parameters, comb properties, and injection current to control the new comb properties. We secondly analyze the nonlinear dynamics and polarization properties in vertical-cavity surface-emitting lasers (VCSELs) subject to orthogonal optical injection with frequency combs experimentally. Most importantly, the VCSEL shows two frequency combs with orthogonal polarization from a single device for some injection parameters. We also demonstrate the possibility to control the single or two polarizations comb repetition rate through harmonic frequency combs generation. We finally present experimentally and theoretically the VCSEL injection dynamics from parallel optical frequency comb injection. We show that the two polarizations combperformance is restricted to high current injection in the case of parallel optical injection. For fixed bias current, the two polarization comb dynamics disappear when increasing the injected comb spacing.This thesis therefore demonstrates besides its interest for nonlinear laser dynamics, optical injection is a technique to harness the comb properties in laser diodes.
... With the charge carrier confinement in the three spatial dimensions, the energy levels are completely discrete in those nanostructures with zero dimensionality. Prior studies demonstrated that semiconductor lasers made with these nanocrystals lead to high lasing efficiency [15,16], low relative intensity noise [17][18][19], remarkable temperature stability [20], and high tolerance for EOF [21][22][23]. More recently, it has been shown that epitaxial QD lasers directly grown on silicon are interesting for integrated technologies since they are less sensitive to the dislocations arising during the epitaxial growth of III-V groups on silicon compared to their quantum well (QW) counterparts [24]. ...
This work reports on a high-efficiency InAs/GaAs distributed feedback quantum dot laser. The large optical wavelength detuning at room temperature between the lasing peak and the gain peak causes the static, dynamic, and nonlinear intrinsic properties to all improve with temperature, including the lasing efficiency, the modulation dynamics, the linewidth enhancement factor, and consequently the reflection insensitivity. Results reported show an optimum operating temperature at 75°C, highlighting the potential of the large optical mismatch assisted single-frequency laser for the development of uncooled and isolator-free high-speed photonic integrated circuits.
... Among different optical frequency comb technologies, mode-locked laser (MLL) sources are very attractive solutions especially for mmWave RoF communication systems due to suppression of phase noise between correlated optical tones [22][23][24][25][26]. Passively mode-locked lasers based on saturable absorber [23] or quantum dash gain medium [24,26] have been used extensively for optical mmWave generation. Recently, semiconductor based coherent comb laser (CCL) sources that employ quantum dots (QDs) as the active gain medium have demonstrated features such as compact size, low cost, large mode spacing, low optical phase and relative intensity noises and high-power performance [27][28][29][30][31]. The QD CCLs show a great potential as the monolithic light sources in the broadband optical communication systems. ...
... Each of the quantum dots can function as an independent light source and emit light at its own wavelength. As a result, the QD CCL is a stable multi-wavelength coherent comb source without requiring special mode-locking structures [27][28][29]. The control of the QD CCL is very simple which only requires a DC bias. ...
... (1.15Q) barriers embedding five stacked layers of InAs QDs as the active gain region surrounded by nand p-type InP cladding layers. Chemical beam epitaxy (CBE) was used to grow the InAs QD material on exactly (001)-oriented n-type InP substrates in a similar manner to that in [29]. A detailed schematic for a single dot layer is shown in Fig. 1(a). ...
We propose and experimentally demonstrate a converged optical-wireless WDM access network architecture enabled by a highly integrated quantum dot coherent comb laser. The converged optical-wireless WDM network features simultaneous delivery of coherent and millimeter wave (mmWave) / citizens broadband radio service (CBRS) signals over 50-km and 20km fiber links, respectively.
... Over the past decade, we have reported different InAs/InP QDash/QD Fabry-Perot (F-P) MLLs in the C-and L-bands with channel spacing that can cover an RF frequency range from tens of GHz to THz [35,38,44,[59][60][61][62]. In this paper, we report a 25 GHz QDash BH MLL, its design, fabrication, experimental characterization and demonstration in an end-to-end proof-of-concept RoF system with RF wireless links. ...
We have developed and experimentally demonstrated a highly coherent and low noise InP-based InAs quantum dash (QDash) buried heterostructure (BH) C-band passively mode-locked laser (MLL) with a pulse repetition rate of 25 GHz for fiber-wireless integrated fronthaul 5G new radio (NR) systems. The device features a broadband spectrum providing over 46 equally spaced highly coherent and low noise optical channels with an optical phase noise and integrated relative intensity noise (RIN) over a frequency range of 10 MHz to 20 GHz for each individual channel typically less than 466.5 kHz and -130 dB/Hz, respectively, and an average total output power of ∼50 mW per facet. Moreover, the device exhibits low RF phase noise with measured RF beat-note linewidth down to 3 kHz and estimated timing jitter between any two adjacent channels of 5.5 fs. By using this QDash BH MLL device, we have successfully demonstrated broadband optical heterodyne based radio-over-fiber (RoF) fronthaul wireless links at 5G NR in the underutilized spectrum of around 25 GHz with a total bit rate of 16-Gb/s. The device performance is experimentally evaluated in an end-to-end fiber-wireless system in real-time in terms of error vector magnitude (EVM) and bit error rate (BER) by generating, transmitting and detecting 4-Gbaud 16-QAM RF signals over 0.5-m to 2-m free-space indoor wireless channel through a total length of 25.22 km standard single mode fiber (SSMF) with EVM and BER under 8.4% and 2.9 × 10⁻⁵, respectively. The intrinsic characteristics of the device in conjunction with its system transmission performance indicate that QDash BH MLLs can be readily used in fiber-wireless integrated systems of 5G and beyond wireless communication networks.
