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This paper presents low phase noise optical heterodyne millimeter-wave signals generation and data transmission using an ultra-low noise InAs/InP quantum-dash dual-wavelength DFB laser for potential applications in high capacity 5G mm-wave-over fiber mobile fronthaul links., Laser Applications Conference 2020, October 13–16, 2020, Washington, D.C. US

We report the first demonstration of electrically-pumped continuous wave (CW) lasing of 1.5 µm quantum dash lasers directly grown on (001) silicon. Preliminary results include lowest threshold current density of 1.3 kA/cm2, and high temperature operation up to 59 oC in CW mode operation.

Subwavelength metamaterial structures in silicon waveguides open new degrees of freedom to control on-chip light propagation. They have been applied to many silicon photonic devices such as fiber-chip couplers, waveguide crossings, microspectrometers, ultra-fast optical switches, athermal waveguides, evanescent field sensors, polarization rotators and colorless interference couplers [1]. Here we report a demonstration of a metamaterial coupler and an InAs-on-InP quantum dash buried heterostructure laser optimized for mutual integration by direct facet-to-facet coupling with -1.2 dB coupling efficiency, coupled laser relative intensity noise (RIN) of -150 dB/Hz and 152 kHz linewidth. We further demonstrate the design of multi-line spectral notch filters based on narrow linewidth metamaterial Bragg filters synthesized using the layer-peeling method., 2020 Photonics North (PN), May 26-28, 2020, Niagara Falls, ON, Canada

Quantum dot and quantum dash (QDash) lasers exhibit lower threshold, less temperature sensitivity, and larger modulation bandwidths than the conventional quantum well lasers. For III–V lasers monol...

International audience; A continuous-wave 1.6 µm-emitting InAs Quantum Dash-based Optically-Pumped Vertical-External-Cavity Surface-Emitting Laser on InP is demonstrated. The laser emits in the L-band with a stable linear polarization. Up to 163 mW output power has been obtained in multi-transverse mode regime. Single-frequency regime is achieved in the 1609-1622 nm range, with an estimated linewidth of 22 kHz in a 49 mm cavity, and a maximum emitted power of 7.9 mW at 1611 nm. In such conditions, the laser exhibits a Class-A behavior, with a cut-off frequency of 800 kHz and a shot-noise floor of −158 dB/Hz for 2 mA of detected photocurrent.

We report experimental studies of the influence of symmetric dual-loop optical feedback on the RF linewidth and timing jitter of self-mode-locked two-section quantum dash lasers emitting at 1550 nm. Various feedback schemes were investigated and optimum levels determined for narrowest RF linewidth and low timing jitter, for single-loop and symmetric dual-loop feedback. Two symmetric dual-loop configurations, with balanced and unbalanced feedback ratios, were studied. We demonstrate that unbalanced symmetric dual loop feedback, with the inner cavity resonant and fine delay tuning of the outer loop, gives narrowest RF linewidth and reduced timing jitter over a wide range of delay, unlike single and balanced symmetric dual-loop configurations. This configuration with feedback lengths 80 and 140 m narrows the RF linewidth by 4-67x and 10-100x, respectively, across the widest delay range, compared to free-running. For symmetric dual-loop feedback, the influence of different power split ratios through the feedback loops was determined. Our results show that symmetric dual-loop feedback is markedly more effective than single-loop feedback in reducing RF linewidth and timing jitter, and is much less sensitive to delay phase, making this technique ideal for applications where robustness and alignment tolerance are essential., Comment: 14 Pages, 10 Figures. arXiv admin note: text overlap with arXiv:1705.09145

The dynamics of C-band quantum-dot and quantum-dash lasers under small-signal modulation are compared. We show a strong influence of the density of states function on the cut-off frequency, being much higher for QDs at low currents, but reaching similar values for QDashes at higher currents.

Sub-kHz RF-linewidth was demonstrated in two-section quantum-dash mode-locked lasers emitting near 1550 nm and 20 GHz repetition-rate using symmetric dual-loop and fiber delay. Compared to free-running lasing, RF-linewidth and timing-jitter reduced by ∼100× and ∼10×.

International audience; Combining theoretical and experimental studies show that optical injection strongly changes the behavior of the linewidth enhancement factor (αH-factor) and the FM-to-AM indices ratio (FAIR) in quantum dash/dot semiconductor lasers. In contrast to solitary lasers, both the αH-factor and the FAIR at low-frequency modulation are reduced by optical injection. At high modulation frequency, however, the phase-amplitude coupling characteristics are little influenced by optical injection.

Single-mode diode lasers on an InP(001) substrate have been developed using InAs/In0.53Ga0.47As quantum dash (Qdash) active regions and etched lateral Bragg gratings. The lasers have been designed to operate at wavelengths near 2 μm and exhibit a threshold current of 65 mA for a 600 μm long cavity, and a room temperature continuous wave output power per facet >5 mW. Using our novel growth approach based on the low ternary In0.53Ga0.47As barriers, we also demonstrate ridge-waveguide lasers emitting up to 2.1 μm and underline the possibilities for further pushing the emission wavelength out towards longer wavelengths with this material system. By introducing experimentally the concept of high-duty-cycle lateral Bragg gratings, a side mode suppression ratio of >37 dB has been achieved, owing to an appreciably increased grating coupling coefficient of κ ∼ 40 cm−1. These laterally coupled distributed feedback (LC-DFB) lasers combine the advantage of high and well-controlled coupling coefficients achieved in conventional DFB lasers, with the regrowth-free fabrication process of lateral gratings, and exhibit substantially lower optical losses compared to the conventional metal-based LC-DFB lasers.

J.M. acknowledges the financial support from COPERNICUS Award of the Foundation for Polish Science (FNP) and Deutsche Forschungsgemeinschaft (DFG). The fellowship co-financed by the European Commission within European Social Fund is also acknowledged. The influence of acoustic phonons on the emission spectra of quantum dashes (QDashes), that are quasi-zero-dimensional epitaxial nanostructures with significant shape anisotropy, is investigated both experimentally and theoretically. Photoluminescence (PL) spectra of single InAs/InGaAlAs/InP (001) QDashes exhibit sidebands of the main emission peak, clearly indicating the contribution of phonon-assisted emission to the exciton luminescence, which dominates the PL line shape at higher temperatures (between 50 and 100 K, usually). By utilizing the independent boson model we perform systematic and comprehensive studies of the influence of the overall geometry of quantum confinement on this spectral feature in an uncommon quantum system. A comparison of the experimental data and the results of modeling have confirmed the existence of two types of states differing in the spatial confinement and symmetry within one sample, i.e., typical for large elongated objects or characteristic for smaller and more symmetric structures. The latter are supposed to correspond to local widenings or zigzag bends present in some of the dashes and acting as additional localization centers, which confine excitons in a much smaller volume and decrease effectively the resulting in-plane anisotropy. Those observations evidence a nontrivial spatial character of the quantum confinement in these structures. They are consistent with our previous polarization-resolved study on the QDash ensemble and correlate well with the exciton decay times, and the spectral-diffusion-dominated line broadenings at low temperatures reflecting the effect of electric field fluctuations on the excitons of a different spatial extension. Finally, we demonstrate a pronounced suppression of phonon-induced decoherence for such strongly elongated nanostructures. Publisher PDF

InAs-InGaAlAs-InP quantum-dash lasers have been fabricated showing continuous-wave operation up to 100degC with a characteristic temperature of 88 K between 25degC and 85degC and output powers above 27 mW at room temperature (RT). The small-signal modulation bandwidth of 10 GHz at RT amounts still to 4 GHz at 85degC. The linewidth enhancement factor above threshold is evaluated by means of the frequency-modulation/amplitude-modulation method in dependence on modulation frequency and drive current, exhibiting a value of 2.5 slightly above threshold.

International audience; We report an InP based vertical cavity surface emitting laser (VCSEL) achieving a lasing operation between 1529 and 1646 nm. This optically-pumped VCSEL includes a wide-gain bandwidth active region based on InAs quantum dashes and wideband dielectric Bragg mirrors. Based on a wedge microcavity design, we obtain a spatial dependence of the resonant wavelength along the wafer, enabling thus to monitor the gain material bandwidth. We demonstrate a 117 nm continuous wavelength variation of the VCSEL emission, a consequence of the important and wide gain afforded by the use of optimized quantum dashes.

International audience; We present an InP-VCSEL based on optimized InAs quantum-dashes (QDHs) nanostructures operating at telecommunication wavelength. Contrary to conventional quantum-wells (QWs) based VCSELs, InAs QDHs can be used as gain media in InP-VCSEL to achieve a stable and polarized laser emission. Here, we demonstrate an optically-pumped QDH based VCSEL, with a constant and control linear state of polarization, and showing a CW laser emission from 1647 down to 1542 nm, covering thus a spectral window as large as 105 nm.

We report spectrally resolved dynamical properties of 1550nm quantum-dash lasers. The dynamics are governed by the inhomogeneous broadening of the gain medium and by wavelength-dependent carrier capture and escape rates.

The dynamic properties of MOVPE grown InP/InAs quantum-dot and quantum-dash lasers, showing identical structural design, emitting in the C-band are investigated and compared to each other. Based on the small-signal measurements, we show the impact of the density of states function on the cut-off frequency, being larger for quantum dots at low currents, and reaching similar values for quantum dashes only at higher currents. The large-signal measurements show error-free data transmission at 22.5 and 17.5 Gbit/s for the quantum-dot and quantum-dash lasers.

A review is given on the recent progress in 1.55 μm QD laser material based on an improved geometry control of QDs and its application in high speed optoelectronic devices. Also a prospect will be given for the realization of high speed directly modulated QD lasers having the potential to reach data rates of 25 GBit/s.

The effect of carrier relaxation process into the quantum dash (Qdash) ground state (GS) is examined theoretically by carrier-photon rate equation model incorporating the inhomogeneous broadening. Increase in the relaxation time and the inhomogeneous broadening degrades the threshold current density. Moreover, our results show that a relaxation time of less than 2 ps gives optimum laser performance.

First observations of 2-section InAs/InP quantum-dash passive mode locking at 48 GHz are presented. Mode locking trends are compared to those of a 1-section device and to the ones reported for InAs/GaAs quantum-dot lasers.

The performance of a quantum-dash Fabry-Perot laser is experimentally characterized for 40 Gb/s RZ-DPSK and NRZ-DPSK clock recovery, 40 Gb/s RZ-OOK all-optical 3R regeneration, and 160 Gb/s OTDM sub-harmonic clock recovery.

The authors report on the effect of quantum-dash (Qdash) inhomogeneity on the characteristics of InAs/InP Qdash laser utilizing a single state rate equation model. The inhomogeneity is assumed to follow the Gaussian approximation. From our observation, an increased in Qdash inhomogeneity results in increasing of threshold current density and redshifting of the peak lasing wavelength. The lasing linewidth of the Qdash lasers has also found to increase under large injection current, attaining a full width at half maximum (FWHM) of ∼ 17 nm.

The bandwidth of quantum-dash lasers under optical injection modulation is sharply enhanced when the injection photons are ∼33 meV more energetic than the laser emission. This new bandwidth-enhancement mechanism is attributable to stimulated Raman scattering.

International audience; Low-threshold current density InAs quantum dash lasers are demonstrated by reducing the energy inhomogeneous broadening through an optimised double-cap technique. A threshold current density for an infinite cavity length of 225 A/cm² (~45 A/cm² per stack) is obtained from a five-stack laser structure. The characteristic temperature above room temperature is 52 K, and this relatively low value results from the carrier leakage from the dash into the barrier (waveguide) region.

The intrinsic response of quantum dash lasers are measured using a pulse optical modulation technique. Our results show fast well-to-dash carrier capture and intra-dash carrier relaxation with K-factors independent on the pump wavelengths.

Life tests on our quantum dash lasers were carried out at 10 mW at 70 and 90degC. Highly stable static and noise characteristics prior and after 11200 hours of ageing tests are analysed.

The reliability potentiality of quantum dash lasers was investigated. During 7000 hours under CW operation at 60/spl deg/C junction temperature, no failure was observed. The results of static and dynamic characterisations after ageing are presented.

We report the first experimental characterization of the room temperature gain dynamics of InAs quantum dash optical amplifiers operating at wavelength of 1550 nm. A gain recovery time of 150 ps was observed.

Summary form only given. In this work 1.55 /spl mu/m emitting quantum dash (QDash) lasers were realized by self organized growth of InAs quantum dashes on InGaAlAs surfaces lattice matched to InP. The influence of the number of QDash layers in the active region of a laser on device performances was studied. Device results from broad area as well as from cw operating ridge waveguide (RWG) QDash-lasers are presented and discussed in relation to telecommunication applications.

We study the enhanced inhomogeneity across the InAs quantum-dash (Qdash) layers by incorporating a chirped AlGaInAs barrier thickness in the InAs/InP laser structure. The lasing operation is investigated via Fabry-Pérot ridge-waveguide laser characterization, which shows a peculiar behavior under quasi-continuous-wave (QCW) operation. Continuous energy transfer between different dash ensembles initiated quenching of lasing action among certain dash groups, causing a reduced intensity gap in the lasing spectra. We discuss these characteristics in terms of the quasi-zero-dimensional density of states (DOS) of dashes and the active region inhomogeneity.

We report a theoretical model for InAs/InP quantum-dash (Qdash) lasers incorporating a coupled set of rate equations taking into account the inhomogeneous broadening due to Qdash size fluctuation, the homogeneous broadening due to optical gain of a single Qdash, and the longitudinal cavity modes. The role of cavity length on the Qdash lasing characteristics, particularly the redshift in the peak lasing wavelength, is analyzed and compared with the experimental results by attributing it to the active region inhomogeneity.

InAs columnar quantum dash (CQDash) structures on (100) InP have been realized by gas source molecular beam epitaxy for stacking numbers of up to 24. Laser devices show low threshold current densities between 0.73 and 3.5 kA/cm(2), dependent on the CQDash orientation within the cavity. Photoluminescence and electroluminescence measurements confirm a strong relationship between the polarization degree of the emission and the orientation of the CQDashes. Eventually, the polarization of the CQDash emission could be changed from predominantly transverse electric to transverse magnetic by simply altering the dash alignment relative to the light propagation axis.

The static and dynamic properties of state-of-the-art InP-based QDash lasers around 1.55 µm are reported. Demonstrated are ridge waveguide lasers with a total output power of 37 mW and a total slope efficiency of 0.40 W/A that show a 3 dB modulation bandwidth of 8.0 GHz and a modulation efficiency of 0.76 GHz/√mA in continuous-wave operation.

Laterally coupled, complex distributed feedback lasers based on AlInGaAs/InAs/InP quantum dash layers were fabricated by maskless focused ion beam lithography. Continuous-wave powers above 30 mW at room temperature, sidemode suppression ratios of 44 dB and a modulation bandwidth of 7.6 GHz were demonstrated.

Room temperature operation of a quantum dash-in-a-well (DWELL) laser based on InP at 2.03 µm wavelength has been achieved. An uncoated laser employing five DWELL layers in the active region shows threshold current densities between 540 and 950Acm-2. Slope efficiencies range from 3.5 to 6.8 %. The internal efficiency was estimated at 52 % and the internal losses at 55cm-1. This is the longest wavelength reported so far for quantum DWELL lasers.

We demonstrate Tbit/s transmission with a Q-Dash mode-locked laser using coherent detection. The aggregate capacity achieved with PDM-QPSK was 1.8Tb/s over 50km of SSMF, using 36 channels from the 34.5GHz FSR Q-Dash PMLL.

We present what we believe to be the first ever high-pressure and spontaneous emission measurements on quantum dash lasers. The results show that temperature sensitivity of these lasers is caused by nonradiative processes, which depend on the lasing wavelength.