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Semiconductor nanostructures with low dimensionality like quantum dots and quantum dashes are one of the best attractive and heuristic solutions for achieving high performance photonic devices. When one or more spatial dimensions of the nanocrystal approach the de Broglie wavelength, nanoscale size effects create a spatial quantization of carriers leading to a complete discretization of energy levels along with additional quantum phenomena like entangled-photon generation or squeezed states of light among others. This article reviews our recent findings and prospects on nanostructure based light emitters where active region is made with quantum-dot and quantum-dash nanostructures. Many applications ranging from silicon-based integrated technologies to quantum information systems rely on the utilization of such laser sources. Here, we link the material and fundamental properties with the device physics. For this purpose, spectral linewidth, polarization anisotropy, optical nonlinearities as well as microwave, dynamic and nonlinear properties are closely examined. The paper focuses on photonic devices grown on native substrates (InP and GaAs) as well as those heterogeneously and epitaxially grown on silicon substrate. This research pipelines the most exciting recent innovation developed around light emitters using nanostructures as gain media and highlights the importance of nanotechnologies on industry and society especially for shaping the future information and communication society., Quantum dot are one of the best practical examples of nanotechnologies. Owing to the discrete energy levels, quantum dot lasers output unique features like thermal stability, feedback insensitivity and spectral purity.

57Fe-ZSM-5 catalysts were prepared by solid-state ion exchange of 57FeCl3 into H-ZSM-5, the exchange capacity of which had been blocked by Na+ or Ca2+ to ≈50, ≈25, and 0%. Their Fe site structure w...

This paper investigates the intensity noise and pulse oscillation characteristics of an InAs/GaAs quantum dot laser epitaxially grown on germanium. We show that the relative intensity noise of the free-running laser generally decreases with increasing pump current, and the minimum value reaches down to about $-$ 126 dB/Hz. The intensity noise is hardly affected by the optical feedback, unless there is a resonance or pulse oscillation in the noise spectrum. The laser pumped at a high current is more sensitive to the optical feedback. Interestingly, it is found that the free-running Ge-based quantum dot laser generates self-sustained pulse oscillations with one period or two periods upon the pump current, without incorporating saturable absorbers. This behavior is valuable for both self-generation of photonic microwaves and for understanding nonlinear dynamics of semiconductor lasers.

This letter reports on a 1.3- $\mu \text{m}$ reflection insensitive transmission with a quantum dot laser directly grown on silicon in the presence of strong optical feedback. These results show a penalty-free transmission at 10 GHz under external modulation with −7.4-dB optical feedback. The feedback insensitivity results from the low linewidth enhancement factor, the high damping, the absence of off-resonance emission states, and the shorter carrier lifetime. This letter paves the way for future on chip high-speed integrated circuits operating without optical isolators.

Quantum dot lasers directly grown on silicon are excellent candidates to achieve energy and cost-efficient optical transceivers thanks to their outstanding properties such as high temperature stability, low threshold lasing operation, and high feedback tolerance. In order to reach even better performance, p-type doping is used to eliminate gain saturation, gain broadening due to hole thermalization and to further reduce the linewidth enhancement factor. Optical transceivers with low relative intensity noise are also highly desired to carry broadband data with low bit-error rate. Indeed, the intensity noise stemming from intrinsic optical phase and frequency fluctuations caused by spontaneous emission and carrier noise degrades the signal-to-noise ratio and the bit-error rate hence setting a limit of a highspeed communication system. This paper constitutes a comprehensive study of the intensity noise properties of epitaxial quantum dot lasers on silicon. Results show minimal values between - 140 dB/Hz and - 150 dB/Hz for doping level between 0 and 20 holes/dot in the active region. In particular, the intensity noise is insensitive to temperature for p-doped QD laser. Modulation properties such as damping, carrier lifetime, and K-factor are also extracted from the noise characteristics and analyzed with respect to the doping level. We also provide numerical insights based on an excitonic model illustrating the effects of the Shockley-Read-Hall recombination on the intensity noise features. These new findings are meaningful for designing high speed and low noise quantum dot devices to be integrated in future photonic integrated circuits.

The sensitivity of a hybrid distributed feedback semiconductor (DFB) laser heterogeneously integrated onto silicon (Si) is extensively characterized in the presence of external optical feedback at different bias and temperature conditions. The unique modal engineering approach of the device allows the light generated in the III-V material to be stored in the low-loss Si region to significantly enhance the quality (Q) factor of the cavity resonator. This design leads to an increased temperature tolerance of the laser without impacting the transmission efficiency even under the most severe feedback conditions. At a temperature of T = 35◦C, the laser continuous to unveil optimal performance and exhibits feedback insensitivity when externally modulated at 10 Gbps transmission over a 10 km fiber coil. The study presented here demonstrates the ability of a high-Q laser to achieve floor-free transmission at different operating conditions with a power penalty degradation no greater than 1.5 dB. The prolonged transition to the coherence collapse regime at a much higher reflection level evidenced by this device when compared to its III-V counterparts in addition to its ability to withstand perturbations associated with temperature variations and unintentional back-reflections delivers a step forward towards isolator-free applications. This work suggest that this type of semiconductor lasers can serve as a promising solution for the development of compact and reliable photonic integrated circuits (PICs).

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.

Photonic integrated circuits enable energy efficient and compact technologies for modern information communications. Here, we explore semiconductor epitaxial quantum dots lasers on silicon and demonstrate their high suitability for addressing the important issues associated to photonic integration on silicon.

This work experimentally investigates the impact of p-doping on the relative intensity noise (RIN) properties and subsequently on the modulation properties of semiconductor quantum dot (QD) lasers epitaxially grown on silicon. Owing to the low threading dislocation density and the p-modulation doped GaAs barrier layer in the active region, the RIN level is found very stable with temperature with a minimum value of − 150 d B / H z . The dynamical features extracted from the RIN spectra show that p-doping between zero and 20 holes/dot strongly modifies the modulation properties and gain nonlinearities through increased internal losses in the active region and thereby hinders the maximum achievable bandwidth. Overall, this Letter is important for designing future high-speed and low-noise QD devices integrated in future photonic integrated circuits.

This work reports on an investigation of the optical feedback in an InAs/InGaAs passively mode-locked quantum dot (QD) laser epitaxially grown on silicon. Under the stably-resonant optical feedback condition, experiments demonstrate that the radio-frequency linewidth is narrowed whatever the bias voltage applied on the saturable absorber (SA) is; on the other hand, the effective linewidth enhancement factor of the device increases with the reverse bias voltage on the SA, hence it is observed that such an increase influences the mode-locking dynamic and the stability of device under optical feedback. This work gives insights for stabilizing epitaxial QD mode-locked lasers on silicon which is meaningful for their applications in future large-scale silicon electronic and photonic applications requiring low power consumption as well as for high-speed photonic analog-to-digital conversion, intrachip/interchip optical clock distribution and recovery.

International audience; This work reports on the optical feedback dynamics of InAs/GaAs QD lasers epitaxially grown on silicon operating in both the short and long delay regimes. Both undoped and p-doped QD lasers are considered. Whatever the external cavity length, no chaotic oscillations are observed on both samples as a result of the small α-factor observed in the silicon QD lasers. Despite that, experiments conducted in the short-cavity region raise period-one oscillation for the undoped QD laser. In addition, the transition from the short to long delay regimes can be finely covered by varying the external cavity length from 5 cm to 50 cm, and the boundaries associated to the appearance of the periodic oscillation are identified. In the short-cavity region, boundaries show some residual undulations resulting from interferences between internal and external cavity modes; whereas in the long-delay regime, the feedback ratio delimiting the boundaries keeps decreasing, until it progressively becomes rather independent of the external cavity length. Overall, our results showed that the p-doped device clearly exhibits a much higher tolerance to the different external feedback conditions than the undoped one, seeing that its periodic oscillation boundaries are barely impossible to retrieve at the maximum feedback strength of-7 dB. These results show for the first time the p-modulation doping effect on the enhancement of feedback insensitivity in both short-and long-delay configurations, which is of paramount importance for the development of ultra-stable silicon transmitters for photonic technologies.

Direct epitaxial growth of III-V lasers on silicon provides the most economically favorable means of photonic integration but has traditionally been hindered by poor material quality. Relative to commercialized heterogeneous integration schemes, epitaxial growth reduces complexity and increases scalability by moving to 300 mm wafer diameters. The challenges associated with the crystalline mismatch between III-Vs and Si can be overcome through optimized buffer layers including thermal cyclic annealing and metamorphic layers, which we have utilized to achieve dislocation densities 10,000,000 h). At 60°C, lasers with extrapolated time-to-failure >50,000 h have been demonstrated for >4,000 h of continuous aging. Lasers have also been investigated for their performance under optical feedback and showed no evidence of coherence collapse at back-reflection levels of 100% (minus 10% tap for measurement) due to the ultralow linewidth enhancement factor (αH < 0.2) and high damping of the optimized quantum dot active region.

This work investigates the performance of 1.3-μm quantum dot lasers epitaxially grown on silicon under optical feedback sensitivity with different temperature and doping profiles. Experiments show that these quantum dot lasers exhibit a very high degree of resistance to both incoherent and coherent optical feedbacks. 10 Gbps penalty-free transmissions are also unveiled under external modulation and at different temperatures. The paper draws attention on quantum dot lasers with p-doping that exhibit a better thermal resistance, a lower linewidth enhancement factor, a higher critical feedback level, and a better spectral stability with less intensity noise. Together, these properties make epitaxial quantum dot lasers with p-doping more promising for isolator-free and Peltier-free applications, which are meaningful for future high-speed photonic integrated circuits.

Achieving high-performance by an effective and convenient preparation method is of great significance to the application of thermoelectric materials. Herein, we propose a facile method combined one-step solid state reaction (SSR) with hot pressing (HP) to fabricate Mg2(Si0.3Sn0.7)0.99Sb0.01. Although the main products after the SSR are Mg2Si and Mg2Sn compounds as well as various Mg2Si1−xSnx phases, the compact bulk sample with anti-fluorite structure is obtained in 2 h of HP process by controlling HP temperature. The obtained Mg2(Si0.3Sn0.7)0.99Sb0.01 exhibits a decent figure of merit of 1.37 at 673 K associated with a flexural strength of 74 MPa, which is fully comparable with the samples prepared by the method of two-step SSR combined with sintering technique, but the process of our method is obviously simplified.

Achieving the simultaneous improvement of thermoelectric and mechanical properties is of great significance for the application of thermoelectric materials. Here, we fabricate the bulks of Mg2(Si0.3Sn0.7)0.99Sb0.01 hybrid composites reinforced by graphene oxide nanosheets (GOs) and multi-walled carbon nanotubes (MWCNTs). The influences of GOs and MWCNTs on the thermoelectric and mechanical properties of the composites are characterized in detail. It is found that the hybrid composites exhibit obvious improvements in flexural strength and fracture toughness with respect to both the matrix and the samples reinforced by GOs or MWCNTs alone, owing to the remarkable synergistic effect of GOs and MWCNTs. Meanwhile, the dimensionless figures of merit are basically maintained or even slightly enhanced when dual reinforcements of GOs and MWCNTs are introduced. Our work provides a feasible path to obtain excellent mechanical and thermoelectric properties simultaneously.

This work investigates the reflection sensitivity of a hybrid III-V on silicon narrow line semiconductor laser based on a high quality factor grating. Experimental results reveal a floor-free operation under optical feedback hence indicating that such lasers can function without optical isolators.

This work investigates the effect of the polarization anisotropy on the linewidth enhancement factor and the reflection sensitivity of InAs/InP quantum dash semiconductor lasers. The results show that the small linewidth enhancement factor and high stability against external optical feedback are obtained for nanostructures oriented perpendicular to the cavity axis as opposed to those oriented parallel to the cavity axis. Effective simulations on the critical feedback level of these two lasers are also in agreement with experimental results. Such anisotropy is attributed to the polarization dependence of the transition matrix element in these quantum nanostructures.

InAs/GaAs quantum dot (QD) lasers monolithically grown on Ge or Si are a promising method to achieve low cost, large scale, and high yield optical sources for photonic integrated circuits [1]. This work shows that a free-running Ge-based QD laser can output periodic pulse oscillations with one, two and three periods, without incorporating saturable absorber or employing any external perturbations [2,3]. The QD laser under study was epitaxially grown on a 4-inch Ge-wafer by the gas-source molecular beam epitaxy, and the active region consists of five stacked dot-in-well layers [4]. The wafer was fabricated into a ridge-waveguide laser with a ridge width of 4.0 μm and a cavity length of 4.4 mm. The laser shows a lasing threshold of 60 mA at 20 °C, and the lasing peak is at 1213 nm. Figure 1(a) shows that the relative intensity noise (RIN) of the Ge-based laser pumped at 80 mA exhibits a common resonance with continuous-wave output. However, the resonance of the laser pumped at 160 mA does not become overdamped, but evolves into pulse oscillations with a high and sharp peak. Figure 1(b) shows the resonance frequency and the damping factor extracted from the RIN spectra. The resonance frequency increases with the pump current from 0.4 GHz at 80 mA up to 1.1 GHz at 170 mA, whereas the damping factor declines from 4.0 GHz down to 0.03 GHz. The damping reduction confirms the onset of peculiar pulsing dynamics for pump currents above 140 mA.

International audience; This work experimentally investigates the relative intensity noise (RIN) of semiconductor quantum dot (QD) lasers epitaxially grown on silicon. Owing to the low threading dislocations density and the p-modulation doped GaAs barrier layer in the active region, a RIN level as low as-150 dB/Hz at 9 GHz is demonstrated. The results show that the p-doping decreases the high-frequency RIN and the damping factor. In the latter, a damping factor up to 30 GHz at three times the threshold is extracted from the RIN spectrum along with a K-factor of 1.7 ns. These results pave the way for high speed and low noise QD devices for future integrated photonics technologies.

This paper experimentally investigates the thermal dependence of the emission linewidth of $\mathbf{1.52}-\mu \mathbf{m}$ single mode InAs/lnP quantum dot lasers. Using a distributed feedback cavity made with symmetric antireflection coatings, a minimum linewidth of 300 kHz is unveiled. This narrow line is found rather constant with the injection current and the temperature range (293 K – 313 K). However, under certain operating conditions, a linewidth rebroadening is also observed, which may be attributed to the spectral hole burning and to the variations of the alpha-factor with the temperature and bias current. Nevertheless, these results confirm the potential of this technology for manufacturing low-phase noise oscillators for coherent optical communications.

The integration of optical functions on a microelectronic chip brings many innovative perspectives, along with the possibility to enhance the performances of photonic integrated circuits (PIC). Owing to the delta-like density of states, quantum dot lasers (QD) directly grown on silicon are very promising for achieving low-cost transmitters with high thermal stability and large insensitivity to optical reflections. This paper investigates the dynamical and nonlinear properties of silicon based QD lasers through the prism of the linewidth broadening factor (i.e. the so-called α-factor) and the optical feedback dynamics. Results demonstrate that InAs/GaAs p-doped QD lasers epitaxially grown on silicon exhibit very low α-factors, which directly transform into an ultra-large resistance against optical feedback. As opposed to what is observed in heterogeneously integrated quantum well (QW) lasers, no chaotic state occurs owing to the high level of QD size uniformity resulting in a near zero α-factor. Considering these results, this study suggests that QD lasers made with direct epitaxial growth is a powerful solution for integration into silicon CMOS technology, which requires both high thermal stability and feedback resistant lasers.

International audience; A common way of extracting the chirp parameter (i.e., the α-factor) of semiconductor lasers is usually performed by extracting the net modal gain and the wavelength from the amplified spontaneous emission (ASE) spectrum. Although this method is straightforward, it remains sensitive to the thermal effects hence leading to a clear underestimation of the α-factor. In this work, we investigate the chirp parameter of InAs/GaAs quantum dot (QD) lasers epitaxially grown on silicon with a measurement technique evaluating the gain and wavelength changes of the suppressed side modes by optical injection locking. Given that the method is thermally insensitive, the presented results confirm our initial measurements conducted with the ASE i.e. the α-factor of the QD lasers directly grown on silicon is as low as 0.15 hence resulting from the low threading dislocation density and high material gain of the active region. These conclusions make such lasers very promising for future integrated photonics where narrow linewidth, feedback resistant and low-chirp on-chip transmitters are required.

The high-speed dynamics of a hybrid distributed feedback semiconductor laser heterogeneously integrated onto silicon is experimentally investigated in the presence of external optical feedback. The laser fabrication relies on a proper modal engineering in which light is generated in the III–V material and stored in the low-loss silicon region in order to substantially enhance the quality factor of the cavity resonator. In this work, the hybrid laser is found to be insensitive to parasitic reflections leading to a 10 Gbps floor-free transmission with a power penalty no greater than 1.5 dB at room temperature. As a conclusion, owing to the large quality factor, a high coherence collapse level is unveiled in such laser indicating its vast potential to serve as an alternative solution for the development of isolator-free applications in future photonics integrated circuits. A qualitative interpretation is also provided by linking the standard feedback equations to the quality factor of the resonator.

The nonlinear dynamics of InAs/GaAs quantum dot lasers emitting exclusively on single lasing states, either ground or excited state, is investigated. While a laser emitting on the ground state is of importance for the development of isolator-free transmitters, lasers emitting on the excited states are essential for chaos-based applications, microwave photonics, and self-pulsating devices.

Quantum dot nanostructures are one of the best practical examples of emerging nanotechnologies hence offering superior properties as compared to their quantum well counterparts. InAs/GaAs quantum dots allow producing energy- and cost-efficient devices with outstanding temperature stability, lowest threshold current, ultrafast gain dynamics, and low amplified spontaneous emission. This paper reports on the recent achievements in ultrafast and nonlinear dynamics properties of InAs/GaAs quantum dot lasers for radar systems, wireless communications and high-speed optical communications. Passive mode-locking is shown to exhibit a great potential for microwave, millimeter-wave and Terahertz signal generation with high repetition frequency tuning and jitter reduction. The optical feedback is also used to stabilize the pulse emission leading an integrated timing jitter as low as 90 fs without consuming additional power. Lastly, multimode optical feedback dynamics of InAs/GaAs QD lasers emitting on different lasing states is also studied. In particular, a chaos free operation is observed for the first time from the ground state lasing operation.

In this paper, we investigate the temperature dependence of spectral linewidth of InAs/InP quantum dot distributed feedback lasers. In comparison with their quantum well counterparts, results show that quantum dot lasers have spectral linewidths rather insensitive to the temperature with minimum values below 200 kHz in the range of 283K to 303K. The experimental results are also well confirmed by numerical simulations. Overall, this work shows that quantum dot lasers are excellent candidates for various applications such as coherent communication systems, high-resolution spectroscopy, high purity photonic microwave generation and on-chip atomic clocks.

International audience; This work reports on the ultra-low linewidth enhancement factor (αH-factor) of semiconductor quantum dot lasers epitaxially grown on silicon. Owing to the low density of threading dislocations and resultant high gain, an αH value of 0.13 that is rather independent of the temperature range (288 K–308 K) is measured. Above the laser threshold, the linewidth enhancement factor does not increase extensively with the bias current which is very promising for the realization of future integrated circuits including high performance laser sources.

A 10 Gb/s transmission by direct modulation of a distributed feedback semiconductor laser heterogeneously integrated onto silicon is studied with optical feedback. Its impact on the bit error rate and power penalty degradation is analyzed.

International audience

We investigate the interplay between linewidth and $\alpha$ -factor in quantum dot lasers using experimental data and a minimal quantum dot laser rate equation model. The rebroadening of the laser linewidth found experimentally at high injection currents is explained by analytical means and traced back to nonlinear scattering processes. Important differences of the pump current dependent linewidth evolution of quantum dot lasers are highlighted especially if compared to conventional laser devices. Furthermore, we provide a scheme to extract the amplitude-phase coupling as well as effective carrier scattering rates with standard characterization techniques, i.e., linewidth, light versus injected pump current and modulation response measurements.

This work investigates the dynamic and nonlinear properties of quantum dot (QD) lasers directly grown on silicon with a view to isolator-free applications. Among them, the chirp parameter, also named the αH factor, is featured through a thermally insensitive method analyzing the residual side-mode dynamics under optical injection locking. The αH at threshold is found as low as 0.32. Then, the nonlinear gain is investigated from the gain compression factor viewpoint. The latter is found higher for epitaxial QD lasers on silicon than that in heterogeneously integrated quantum well (QW) devices on silicon. Despite that, the power dependence of the αH does not lead to a large increase of the chirp coefficient above the laser’s threshold at higher bias. This effect is confirmed from an analytical model and attributed to the strong lasing emission of the ground-state transition, which transforms into a critical feedback level as high as −6.5 dB, which is ∼19 dB higher than a comparable QW laser. Finally, the intensity noise analysis confirms that QD lasers are overdamped oscillators with damping frequencies as large as 33 GHz. Altogether, these features contribute to fundamentally enhancing the reflection insensitivity of the epitaxial QD lasers. This last feature is unveiled by the 10 Gbit/s error-free high-speed transmission experiments. Overall, we believe that this work is of paramount importance for future isolator-free photonics technologies and cost-efficient high-speed transmission systems.

Bovine serum albumin coated magnetic iron oxide nanoparticles (IONPs), which were synthesized using a co-precipitation method with 57Fe have been subject to a combined study using atomic force microscopy (AFM) and nuclear inelastic scattering (NIS). The obtained partial density of vibrational states (pDOS) shows evidence for lattice stiffening and a pronounced mode at 23 meV compared to thin film magnetite at room temperature.

International audience; Frequency conversion using highly non-degenerate four-wave mixing is investigated in optically injection-locked InAs/GaAs quantum-dot Fabry-Perot lasers with different ridge waveguide dimensions. Conversion efficiencies up to -16 dB with a large optical signal-to-noise ratios of 36 dB are unveiled. The conversion bandwidth is extended to 4 THz with a quasi-symmetrical response between up- and down-converted signals.

Frequency conversion using highly non-degenerate four-wave mixing is reported in InAs/GaAs quantum-dot Fabry- Perot lasers. In order to compress the spontaneous emission noise, the laser is optically injection-locked. Under proper injection conditions, the beating between the injected light frequency and the cavity resonant frequency dominates the dynamic behavior and enhances a carrier modulation resonance at frequencies higher than the relaxation oscillation frequency. Conversion efficiencies as high as -12 dB associated to a large optical signal-to-noise ratio of 36 dB are reported. The conversion bandwidth is extended up to 2.1 THz for down-conversion (resp. 3.2 THz for up-conversion) with a quasi-symmetrical response between up- and down-converted signals.

Recently, an easily scalable process for the production of small (3 −7 nm) monodisperse superparamagnetic ferrite nanoparticles MeFe2O4 (Me = Zn, Mn, Co) from iron metal and octanoic acid has been reported (Salih et al., Chem. Mater. 25 1430–1435 2013). Here we present a Mossbauer spectroscopic study of these ferrite nanoparticles in external magnetic fields of up to B = 5 T at liquid helium temperatures. Our analysis shows that all three systems show a comparable inversion degree and the cationic distribution for the tetrahedral A and the octahedral B sites has been determined to (Zn0.19Fe0.81) A [Zn0.81Fe1.19] B O4, (Mn0.15Fe0.85) A [Mn0.85Fe1.15] B O4 and (Co0.27Fe0.73) A [Co0.73Fe1.27] B O4. Spin canting occurs presumably in the B-sites and spin canting angles of 33°, 51° and 59° have been determined for the zinc, the manganese, and the cobalt ferrite nanoparticles.

Similar InAs/GaAs quantum-dot lasers emitting on either the ground or excited state are studied under optical feedback. The feedback-sensitivity and dynamics of the excited-state laser are investigated and compared to that of the ground-state laser.

Within this work we report a Mossbauer spectroscopic study of uncoated and bovine serum albumin (BSA-) passivated magnetic iron oxide particles. Electron microscopy confirms the successful preparation of the particles with sizes in the 10 to 30 nm range. The analysis of the Mossbauer spectra at high fields shows that only 20% of the iron is present in form of Fe3O4–nanoparticles. The majority (80%) of the iron is present as maghemite (γ–Fe2O3). Coating with BSA does not influence the particle morphology and does also not affect the magnetite to maghemite ratio.

This work reports on a systematic investigation of the influence of optical feedback in InAs/GaAs quantum dot lasers epitaxially grown on silicon. The boundaries associated to the onset of the critical feedback level corresponding to the first Hopf bifurcation are extracted at different bias conditions with respect to the onset of the first excited state transition. Overall, results show that quantum dot lasers directly grown onto silicon are much more resistant to optical feedback than quantum well lasers, mostly resulting from a small linewidth enhancement factor of high-quality quantum dot material. However, results also unveil that the onset of the critical feedback level strongly depends on the excited-to-ground-state ratio, hence a figure of merit showing that a small ratio of the excited-to-ground-state lasing thresholds is not beneficial for maintaining a high degree of stability. This work brings further insights in the understanding of quantum dot laser physics and is useful for designing feedback resistant lasers for isolator-free transmission in metro, access, and data center optical networks, as well as for integrated photonics.

This paper reports on the spectral linewidth of InAs/InP quantum dot distributed feedback lasers. Owing to a low inversion factor and a low linewidth enhancement factor, a narrow spectral linewidth of 160 kHz (80 kHz intrinsic linewidth) with a low sensitivity to temperature is demonstrated. When using anti-reflection coatings on both facets, narrow linewidth operation is extended to high powers, believed to be due to a reduction in the longitudinal spatial hole burning. These results confirm the high potential of quantum dot lasers for increasing transmission capacity in future coherent communication systems.

Micro-flow channel is basic functional component of microfluidic chip, and every step-forward of its construction technique has been receiving concern all over the world. This article presents a notcomplicated but flexible method for fabrication of micro-flow channels. This method mainly utilizes the conventional molding capability of polydimethylsiloxane (PDMS) and widespread commercial microwires as templates. We have fabricated out some conventional types of microchannels with different topological shapes, as examples for the demonstration of this flexible fabrication route which was not dependent on the stringent demands of photolithographical or microelectromechanical system (MEMS) techniques. The smooth surface, high-intensity, and high flexibility of the wires made it possible to create many types of topological structures of the two-dimensional or three-dimensional microchannel or channel array. The geometric shape of the cross-section of thus forming microchannel in PDMS was the negative of that of embedded-in microwire, in high-fidelity if suitable measures were taken. Moreover, such a microchannel fabrication process can easily integrate the conductivity and low resistivity of the metal wire to create micro-flow devices that are suitable for the electromagnetic control of liquid or the temperature regulation in the microchannel. Furthermore some preliminary optical analysis was provided for the observation of thus forming rounded microchannel. Based on this molding strategy, we even made some prototypes for functional microflow application, such as microsolenoids chip and temperature control gadgets. And an experiment of forming a droplet in the cross channel further confirmed the feasibility and applicability of this flexible microchannel forming technique.

In this paper, some factors governing the evaporation rate of aqueous microdroplets generated in a newly developed PDMS (polydimethylsiloxane) microchannel device were examined. Microdroplets of about 0.25nL, composed of any one of the conventional solvents (including water, ethanol, and hexane) were found to be disappearing in about 1 h in a PDMS microchannel (diameter 80μm) when exposed to heating under light microscopy, although this slightly slowed down when placed in an ambient environment. Furthermore, when the inner wall of the PDMS microchannel was microfluidic coated by phospholipid solution, aqueous microdroplets could be maintained with no volume-loss up to at least 1 h.

Non-linear properties of quantum-dot and quantum-dash lasers under dual-mode optical injection are investigated experimentally, showing higher nonlinearity of quantum-dash lasers. Frequency response measurements show equal 3 dB modulation bandwidth of 8 GHz.

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.

Non-degenerate four-wave mixing effects are investigated in an injection-locked InAs/InP nanostructure Fabry-Perot laser. Locking a longitudinal mode at various wavelengths within the gain spectrum and using the locked mode as the pump for the wave mixing shows different levels of asymmetry between up- and down-conversion. Experiments reveal that the normalized conversion efficiency is less asymmetric when the pump is locked at wavelengths below that of the gain peak. The values of nonlinear conversion efficiencies are maintained above -60 dB for pump-probe frequency detunings up to 3.5 THz. The role of the linewidth enhancement factor on the asymmetry is discussed and the value of the nonlinear susceptibility is compared to similar InAs/InP nanostructure semiconductor optical amplifiers. From an end-user viewpoint, data transmission experiments have also confirmed the possibility to propagate up-converted signals over 100 km at a 5 Gb/s bit rate under an OOK modulation format. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only., SPIE OPTO, 7 February 2015, San Francisco, California, United States, Series: Proceedings of SPIE; no. 9357

Non-degenerate four-wave mixing in an InAs/InP quantum dot Fabry–Perot laser is investigated with an optical injection-locking scheme. Wavelength conversion is obtained for frequency detunings ranging from +2.5 THz to −3.5 THz. The normalized conversion efficiency is maintained above −40 dB between −1.5 and +0.5 THz with an optical signal-to-noise ratio above 20 dB and a maximal third-order nonlinear susceptibility normalized to material gain of 2 × 10−19 m3/V2. In addition, we show that injection-locking at different positions in the gain spectrum has an impact on the nonlinear conversion process and the symmetry between up- and down- converted signals.

This work reports on non-degenerate four-wave mixing under dual-mode injection in metalorganic vapor phase epitaxy grown InP/InAs quantum-dash and quantum dot Fabry-Perot laser operating at 1550 nm. High values of normalized conversion efficiency of −18.6 dB, optical signal-to-noise ratio of 37 dB, and third order optical susceptibility normalized to material gain χ(3)/g0 of ∼4 × 10−19 m3/V3 are measured for 1490 μm long quantum-dash lasers. These values are similar to those obtained with distributed-feedback lasers and semiconductor optical amplifiers, which are much more complicated to fabricate. On the other hand, due to the faster gain saturation and enhanced modulation of carrier populations, quantum-dot lasers demonstrate 12 dB lower conversion efficiency and 4 times lower χ(3)/g0 compared to quantum dash lasers.

Highly efficient wavelength conversion is observed by non-degenerate four-wave mixing in an InAs/GaAs quantum dot Fabry-Perot laser. A maximum normalized conversion efficiency of −3 dB, along with a high 35 dB optical SNR are reported.