Search

We present a 56Gbaud/s $13\mu{m}$ electro-absorption modulated laser, based on semi-insulated buried waveguide technology. A dynamic extinction ratio of 8.4dB, with 1. 8dBm fiber coupled average power, and 112Gb/s PAM4 transmission, with a $BER=10^{-3}$ , are demonstrated.

This paper describes a high quality factor III-V on silicon hybrid laser consisting in a harmonic optical potential well cavity. We measured a photon lifetime as high as 103 ps and a relative intensity noise below 147 dB/Hz with a constant level over 20 GHz.

We present an electro-absorption modulated laser with 6dBm modulated power leading to record power budget NRZ transmissions at 1.55μm: 37dB at 10Gb/s over 50km and 30dB at 28Gb/s over 10km with a pre-amplified photodiode.

To solve the problem of thermally-induced frequency drift in burst-mode transmitters for TWDM access networks, we propose a laser with reduced self-heating, and a simple counter-heating method that demonstrates clear improvement in burst-mode BER measurements.

We demonstrate a tunable transmitter, integrating a III-V/Si laser and electro-absorption modulator. This transmitter exhibits a 10nm wavelength tunability and shows error free transmission up to 50km at 10.3Gb/s.

International audience; Quantum-dot (QD) lasers exhibit many useful properties such as low threshold current, temperature and feedback insensitivity, chirpless behavior, and low linewidth enhancement factor (alphaH-factor). Although many breakthroughs have been demonstrated, the maximum modulation bandwidth remains limited in QD devices, and a strong damping of the modulation response is usually observed pointing out the role of gain compression. This paper investigates the influence of the gain compression in a 1.3-mum InAs-GaAs QD laser and its consequences on the above-threshold alphaH-factor. A model is used to explain the dependence of the alphaH-factor with the injected current and is compared with AM/FM experiments. Finally, it is shown that the higher the maximum gain, the lower the effects of gain compression and the lower the alphaH-factor. This analysis can be useful for designing chirpless QD lasers with improved modulation bandwidth as well as for isolator-free transmission under direct modulation.

A new laser suitable for access-systems with FM efficiency up to 7 GHz/mA and negligible amplitude modulation is presented. It enables 1.25/2.5 Gb/s operations with extremely low driving signals: 70 mV pk-pk and 250 mV pk-pk respectively.

Optimization and characterization of multiple InGaAsN/GaAs quantum-well laser diodes for high frequency operation are reported. From the modelling of the dilute nitride quantum well, we investigate how to design the structure to achieve a high frequency operation. The gain characteristics are optimized by incorporating the minimum amount of nitrogen in the well to obtain the emission at 1.3 μm with a low transparency density and a high differential gain. We show that the number of wells must be adjusted to three to benefit of the best compromise between the threshold current and the differential gain. The effects of the cavity losses on the dynamic characteristics are evaluated and demonstrate the interest for high cavity losses to reach high relaxation frequency despite a lower characteristic temperature. An optimized structure has been realized and exhibits an emission at 1.34 μm with a transparency current density of 642 A/cm2 and a characteristic temperature T0 ~ 80 K. Dynamic properties for ridge devices are evaluated from relative intensity noise measurements and small-signal modulation. A relaxation frequency as high as 7.4 GHz and a 9.7 GHz small-signal bandwidth are reported. We demonstrate transmission up to 10 Gb/s at 25°C without penalty and bit error floor.

Static performances and high-frequency characterisation of a GaInNAs/GaAs laser diode emitting at 1.35 μm are reported. Optimised molecular beam epitaxial (MBE) growth has allowed the achievement of a triple quantum well stack for improved dynamic properties. Broad area lasers exhibit a transparency current density of 642 A/cm2 at 20°C under pulsed operation and a characteristic temperature T0 of 80 K. Single-mode narrow-ridge waveguide devices emitting at 1.34 μm demonstrate a low threshold current of 26 mA under continuous wave (CW) operation at 25°C for an HR/as-cleaved cavity. The maximum output power reaches 9 mW with a slope efficiency of 0.13 W/A under CW operation. Intrinsic dynamic properties of the devices have been evaluated through relative intensity noise (RIN) measurements and small signal modulation. The dependence of the relaxation frequency on the bias current shows a slope of 0.92 GHz/mA1/2. The evolution of the damping factor against the squared relaxation frequency gives a K factor of 0.44 ns. RIN measurements yield a record relaxation frequency of 7.4 GHz for this triple-QW device. Small signal modulation shows a 3 dB bandwidth of 9.7 GHz for this new material system, compatible with 10-Gbit/s applications.

Measurements on 1.3-/spl mu/m quantum-dot lasers are presented that reveal a number of interesting effects. 1) At high bias, a second lasing line appears, corresponding to the excited state transition. 2) The linewidth enhancement factor increases dramatically above threshold. 3) The modulation performance is degraded when the second lasing line appears. A comprehensive numerical model is developed to explain this behavior. We attribute it to incomplete gain clamping above threshold. This is caused by a combination of the finite intraband relaxation time and the limited density of states.

Compact parallel transmitters and receivers with an aggregate capacity of 107 Gb/s are built through hybrid integration of arrays of ten 100-GHz spaced directly modulated lasers, arrays of ten avalanche photodiodes, and high-index contrast silica arrayed waveguide grating multi- and demultiplexers. Unamplified transmission over 75 km of standard single-mode fiber and 155-km amplified links is demonstrated in the C-band, by using a modulation format based on spectral offset filtering and electronic dispersion compensation.

We present a 75km-reach 100Gb/s DWDM transmitter based on a fully passive, hybrid assembly of a 10x10Gb/s laser array with a low-loss SiO2 AWG, and its optimization for thermal management, low cost and high yield.

International audience; Injection-locked quantum dash laser exhibits a different FM-to-AM ratio as compared to the solitary one.Optical injection enhances the FM-AM phase difference. The linewidth enhancement factor can no longer becharacterized by the FM/AM technique.

The modulation bandwidth has been identified as a specific limitation of quantum-dot or quantum-dash (QDash) lasers for direct modulation application. Solutions using tunnel injection and p-doping have already been demonstrated to increase the modulation bandwidth above 10 GHz, but with complex tunnel injection design and p-doping induced high internal losses. We show in this letter that the use of optimized QDashes and waveguide structure is sufficient to reach such high bandwidth at 1.55 mum. The device is validated by a large signal modulation demonstration at 10 Gb/s.

Tolerance to optical feedback is investigated on quantum-dash-based lasers emitting at 1.51 mum. The onset of coherence collapse regime is experimentally determined using three criteria: optical spectrum broadening, relative intensity noise increase, and bit-error-rate degradation. Measurements were first performed in static operation at different current values, using the first and second criteria. The onset of coherence collapse was found to increase from ~-41 to -27 dB with the bias current. Then tolerance to optical feedback was assessed in dynamic operation at 10 Gb/s, using the third criterion. In spite of a relatively high linewidth enhancement factor , (alphaH ~4.5) a -32-dB onset of coherence collapse corresponding to -24-dB maximum optical return loss tolerance was achieved at 10-Gb/s rate.

Among the new semiconductor materials for telecom devices, the GaInNAs-GaAs structure presents interesting properties for low-cost applications, like high differential gain and high T/sub 0/. Another key aspect of the performance is the behavior of the GaInNAs-GaAs based lasers under high bit rate direct modulation. Here, we demonstrate the dynamic capabilities of GaInNAs-GaAs three-quantum-well ridge structure through 2.5-Gb/s directly modulated laser emission and transmission on standard fiber, in the temperature range 25/spl deg/C-85/spl deg/C. Besides transmission is demonstrated up to 10 Gb/s at 25/spl deg/C on the same fiber, without penalty and bit-error-rate floor.

Phase correlation leading to self-pulsation (SP) in semiconductor distributed Bragg reflector (DBR) lasers is investigated experimentally and theoretically. Under proper biasing conditions, the laser oscillates with three main modes and we observe that each two-modes beating provides SP with identical spectral linewidth. Under the same operating conditions, the measured spectral linewidths of the beating modes are much larger than the linewidth of the self-pulsating signal. These results demonstrate the natural occurrence of passive mode-locking (PML) and phase correlation in semiconductor DBR lasers. A model based on multimode coupled-wave rate equations, including four-wave mixing (FWM), is developed to describe PML and SP in the gain region of the laser cavity. This model demonstrates that the existence of phase correlation between longitudinal modes is due to FWM.

This letter presents for the first time the dynamic characteristics of a tunable optically pumped 1.6-/spl mu/m vertical-cavity surface-emitting laser (VCSEL) based on micromechanic wavelength tuning. The study includes analysis of the small-signal amplitude modulation response, the relative intensity noise, and the influence of different pump lasers on the VCSEL noise. From the measurements, characteristic semiconductor parameters have been derived and are presented.

Integrated laser modulators are attractive devices for wavelength-division-multiplexing optical systems due to their compactness, high output power, and low cost. Their fabrication simplicity is a way to decrease further the transmitter cost and address new opening markets of short range and metropolitan networks. We report a new integration scheme electroabsorption-modulator distributed feedback (DFB) laser based on well-established industrial solutions for discrete buried ridge (BRS) DFB lasers and discrete shallow ridge modulators. Processing simplification with an identical active layer has been possible due to a good behavior of strongly positively detuned BRS lasers. The integrated devices demonstrated 30-dB extinction ratio with 10-GHz bandwidth and P/sub out/=10 dBm for emission in 1.55-/spl mu/m range.

International audience; It is well known that current modulation in diode lasers generates amplitude (AM) and optical frequency (FM) modulations. The frequency chirp under direct current modulation originates from variations in the carrier density and from the finite difference in carrier density between the laser on and off states. Modulation of the carrier density modulates the gain and the optical index causing the resonant mode to shift. This frequency chirp broadens the spectrum, which is a serious limitation for high-speed applications and optical fiber communications. At low frequencies, thermal effects also alter the frequency chirp. The aim of this paper is to show that the laser’s frequency chirp can be modified using an external control technique. The chirp response is evaluated via the determination of the chirp-to-power ratio (CPR) through a Mach-Zehnder interferometer. Experiments demonstrate that when an external optical feedback is properly adjusted, the CPR can be severely decreased over a wide range of modulation frequencies as compared to the free-running case. These preliminary results obtained on quantum well distributed feedback lasers (QW DFB) with low normalized coupling coefficient (􏰀L) demonstrate how to stabilize the CPR through the DFB facet phase effects or parameters such as the linewidth enhancement factor. In order to confirm this frequency chirp engineering, self- consistent calculations based on the transfer matrix method are also presented.

Measurement of the Henry factor over large optical bandwidth is carried out in a single step without any filtering, using a technique based on the sinusoidal phase modulation method. This fast technique was successfully applied to a directly modulated Fabry Perot laser to obtain simultaneously the linewidth enhancement factor (LEF) of 14 longitudinal modes. It is also well suited for electro-absorption modulators (EAM) for which the α-factor is determined over 15 nm optical bandwidth. A very good agreement is found with the well established fiber transfer function method.

International audience; The temperature dependence of the dynamic performance of p-doped InAs/GaAs quantum-dot distributed feedback (DFB) lasers emitting at 1.3 µm is investigated. A maximum relaxation frequency of ~7 GHz is demonstrated for a constant bias current over the whole 25°C-85°C temperature range. The Henry factor is temperature independent and remains constant at ~2.5. The effect of external optical feedback is assessed on the same device in a 10-Gb/s transmission over 20 km

This work reports the optimization of the design 1.55µm QDashes directly modulated lasers. Non-amplified 10Gb/s transmission in standard single mode fibre is demonstrated from back-to-back up to 65km at constant operating conditions.

The nearly degenerate four-wave mixing technique is used to investigate the physical origin of period doubling in the route toward chaos. This spectroscopic approach identifies resonantly enhanced nearly degenerate four-wave mixing processes as being responsible for the generation of subharmonic frequencies. The technique presented in the case of GaAlAs semiconductor lasers could be applied to the study of monomode instabilities occurring in any laser or bistable devices.

International audience; This paper reports on the tolerance of low-dimensional InAs/InP quantum-dash- and quantum-dot-based semiconductor lasers to optical feedback in the 1.55 mum window. For this purpose, the onset of coherence collapse (CC) is experimentally determined and systematically investigated as a function of different laser parameters, such as the injection current, differential gain, temperature, and photon lifetime. It is in particular found that for both material systems the onset of CC increases with the injection current in a similar way to bulk or quantum-well-based devices. Of most importance, we experimentally show that the differential gain plays a key role in the optical feedback tolerance. It is indeed shown to determine not only the range of the onset of CC but also the dependence of this threshold both on the temperature and laser cavity length. Increasing the operating temperature from 25degC to 85degC leads to a decrease of the onset of CC by a factor of only ~3 dB, well accounted for by the variation of the differential gain in this temperature range. We find no difference in the tolerance to external reflections of a truly 3-D confined quantum-dot-based laser and a quantum dash device of the same cavity length, which have similar differential gains. A tentative analysis of our data is finally carried out, based on existing models.

The performances of a novel low-chirp electroabsorption modulator laser module are presented. Transmission is analysed in standard singlermode fibre at 40 Gbit/s. Propagation without chromatic dispersion compensation up to 2 km exhibits a low penalty variation over a wide temperature range. A propagation scheme with compensation leads to negligible impairment at 88 km.

We study modulation properties of state-of-the-art quantum dot lasers and compare them with state-of-the-art Al-based quantum well lasers. In particular, we demonstrate uncooled transmission over 20 km at 10 Gbit/s, limited by a large adiabatic chirp.

A modulation bandwidth up to 10 GHz in continuous wave mode operation is demonstrated using optimized 1.55 mum InAs/InP (100) quantum dashes based lasers.

We report on the recent advances in InP-based Quantum Dashes (Qdashes) material for 1.55μm optoelectronic devices. We achieve highly uniform, reproducible and wavelength-controlled Qdashes, with a length ranging from 50nm to 500nm depending on the growth conditions. These Qdashes lead either to high modal gain distributed feedback (DFB) lasers or low chirp semiconductor optical amplifier (SOA). Moreover, we demonstrate that Qdashes are compatible with buried ridge stripe and shallow ridge technology and lead to very reliable lasers. Directly modulated lasers with 10GHz bandwidth are demonstrated in continuous wave mode operation. 10Gb/s transmission over 25km in semi-cooled operation is achieved using DFB buried lasers. Qdashes optimization leads to SOA with internal gain of 10 dB and a -3dB optical bandwidth of 120 nm at 50°C, paving the way for semi-cooled CWDM optical sources. Furthermore, low chirp Qdashes SOA are evaluated as optical boosters after a modulated source. Although we still observe overshoots on the amplified signal, the chirp, even in their saturation regime, is low enough to allow for 50 km of transmission at 10Gb/s.

The alphaH-factor behavior with current is investigated in a 1.52 mum InAs/InP (311B) QD laser. It is shown that due to low gain compression effects, no divergence of the alphaH-factor occurs unlike 1.3 mum InAs/GaAs QD lasers.

This paper summarizes recent advances on InAs/InP mode-locked quantum dashes (QD) lasers, and their applications for all-optical clock recovery, short pulse generation and millimeter wave generation. We demonstrate that QD FP lasers, owing to the small confinement factor and the 3D quantification of electronic energy levels, exhibit a beating linewidth as narrow as 15 kHz. Such an extremely narrow linewidth, compared to their QW or bulk counterparts, leads to the excellent phase noise and time jitter characteristics when QD lasers are actively mode-locked. We report also on an actively mode-locking tunnel injection quantum dash Fabry-Perot laser diode at 42.7GHz, generating nearly Fourier transform limited pulses with a pulse width of 2ps over 16nm.

Optically-pumped vertical-external-cavity surface-emitting laser at 1.55 μm emits 77 mW CW single-mode output power with a SMSR above 60 dB at 20°C. Linewidth measurements showed the importance of low frequency fluctuation stabilization.

Tolerance to optical feedback is investigated on quantum-dash based lasers emitting at 1.55 μm on both static and dynamic regimes. The onset of coherence collapse regime is experimentally determined using three criteria: optical spectrum broadening, relative intensity noise increase and bit error rate degradation. In spite of a relatively high linewidth enhancement factor (αH˜4.5), a -32 dB onset of coherence collapse corresponding to -24 dB maximum optical return loss tolerance from the system was achieved at 10 Gbps rate.

New self thermal compensated Single Active Layer AlGalnAs EML demonstrates 43 Gb/s open-eye operation for temperatures ranging between 10°C and 70°C. The dynamic extinction ratio over the whole temperature range was above 10 dB.

10 Gbps operation of quantum-dash based lasers emitting at 1.55 μm is investigated under optical feedback. -24 dB maximum optical return loss tolerance is achieved, in spite of a relatively high linewidth enhancement factor.

Dynamic measurements of the Henry factor showed that, while α H dramatically increases with the bias current for 3- and 5-QD layer laser structures, α H doesn't diverge for a 10-stack QD and amounts to 4.

Buried ridge distributed feedback lasers operating at 1.55 μm wavelength range are fabricated based on dashes-in-the-well InAs/InP. The first floor free 10 Gb/s direct modulation is demonstrated for back-to-back and an accumulated dispersion of 100 ps/nm.

We investigate the devices performances of InAs/InP (100) quantum dash buried stripe ridge lasers. We demonstrate high-gain quantum dash based lasers whose dynamic properties are compatible with high-speed devices requirements. The good temperature characteristic of such lasers allows 10 Gb/s direct modulation in the temperature range of 25-75/spl deg/C. The mode-beating RF spectrum of passively locked FP quantum dashes laser shows a very narrow spectral linewidth (50 kHz) attributed to a strong phase correlation between modes.

We present a 4 section DBR laser which can be used either as a low chirp tunable source or as a tunable FSK transmitter with a high and flat FM response up to 1 GHz.

The high frequency properties of three-quantum well GaInNAs/GaAs lasers emitting at 1.35 /spl mu/m have been investigated. A relaxation frequency of 7.4 GHz and a 9.7 GHz small signal bandwidth are reported for this material system, showing potential for high-bit rate (10 Gbit/s) direct modulation.

10 Gb/s operation at 1.55 μm of an InAs/InP (001) dots-in-a-well buried ridge stripe Fabry-Perot laser is demonstrated for the first time, in the temperature range 25-75°C. (2 pages)

40 GHz self-pulsating distributed Bragg reflector lasers with a polarization insensitive bulk active layer of 0.7/spl times/0.5 /spl mu/m/sup 2/ showed enhanced non-linear behavior at low power level, and nearly 1 GHz of continuous self-pulsation frequency tunability using two active sections.

The variability of optical frequency modulation with electric field in an electro-optical phase section is analysed. When configured for maximum sensitivity, the electro-optical phase section was used to compensate for the chirp of the gain section: 48 ps and 8.5 GHz wide transform-limited pulses were obtained at 5 GHz.

Summary form only. We experimentally show that laser and modulator facet phases with respect to the DFB laser grating are as important for the chirp as the modulator facet reflectivity given a 10 Gbit/s integrated laser-modulator source. We have presented a way to assess not only the modulator induced chirp but also the laser induced chirp of an integrated laser-modulator device. We have shown the influence of the modulator facet reflectivity and the major role of the facet phase versus the DFB laser grating on the chirp. We conclude that the facet reflectivity determines the 10 Gbit/s performance yield rather than individual chip behaviour.

The realization of standard heterojunction and multiple quantum well (MQW) 1.55- mu m lasers in the GaInAsP system grown by gas source molecular beam epitaxy (GSMBE) on [110] InP is discussed. It is shown that high-performance transmitters suitable for the polarization scrambling scheme can be achieved by integrating, on the same substrate, lasers and efficient polarization modulators. >

The feedback induced chirp in an integrated laser Mach-Zehnder modulator is for the first time monitored by measuring the AM response of the laser and compared to theory. The method simplifies investigation of facet phases effect and allows the comparison between different ILMZ configurations.

The adiabatic chirp of DFB semiconductor lasers is shown to be power and facet phase dependent. Importance of this effect on transmission is demonstrated using BER measurements, showing an advantage for gain-coupled lasers versus index-coupled devices.

In this paper, we report the characteristics of InAs/InP quantum dashes (QDash) based lasers emitting around 1.55 μm. An unprecedented high modal gain of ∼100 cm−1 is obtained for an optimized active structure by stacking 12 QDash layers. Directly modulated lasers allowed achieving a modulation bandwidth of ∼10 GHz and a Henry factor around 5. Thanks to p-type doping, the Henry factor value is reduced down to 2.7 while the modulation bandwidth still amounts to ∼10 GHz. This shows that doping of the active region is important to improve the dynamic characteristics of QDash lasers.

The performance of a logic inverter based on injection locking in laser diodes is presented. The fast commutation rise and fall times (5 and 2 ns, respectively) allow a 150 MHz repetition rate. Due to the gain existing in laser diodes, low optical switching energies (50 fJ) and large fan‐out rates (30) are also obtained, making such an inverter attractive for the purpose of parallel optical computing, particularly if semiconductor laser arrays are used in place of single laser diodes.