Search

We have designed, fabricated and characterized an electro-absorption modulator integrated with generic technology on a semi-insulating substrate. The modulator operates at 64Gb/s with 6dB dynamic extinction ratio, a bias voltage of -2.2V and a voltage swing of 3.5V.

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 demonstrate a SOA-UTC receiver PIC in O-band with up to 90 A/W responsivity, NF below 8-dB, >−10 dBm saturation input power and 33 GHz bandwidth which shows a 10−9 sensitivity at 32 Gb/s of −20.5 dBm.

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.

Recent progress in the field of quantum dot/dash based semiconductor optical amplifiers (SOAs) for slow and fast light is discussed. Room temperature fast light has been obtained in InAs/InP QDash based SOAs by means of coherent population oscillation and four wave mixing (FWM) effects. Typical optical delays amount to 55 ps at 2 GHz. Growth optimization of the QDashes allowed us to achieve high modal gain, leading to very similar performances, e.g. gain and FWM efficiency, to those of a bulk SOA. A novel approach based on linear spectrograms is also introduced to measure the phase shift induced by wave mixing in an SOA.

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.

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.

We demonstrate an InP-based photonic multiwavelength transmitter realized by integrating an array of distributed Bragg reflector lasers with modulators in Mach-Zehnder configuration. An arrayed waveguide grating is used to multiplex the generated signals into a common optical output. The device is designed according to a generic integration concept, using standardized building blocks, and is fabricated in a multiproject wafer run. The device delivers up to 4 dBm of optical power into the fiber with a modulation data rate of 12.5 Gbps per transmission channel. The obtained performance makes it very promising for application in the next generation optical access networks as a key source in the central office part of the telecommunication systems.

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.

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.

Unprecedented high modal gain of ~100 cmµ1 is obtained for an optimized structure based on InAs/InP quantum dashes (QDash) emitting at 1.55 µm. This structure allows achieving ~10 GHz direct modulation bandwidth. P-type doping reduces the Henry factor value down to 2.7.

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.

This letter describes a judicious implication of optical low-coherence reflectometry (OLCR) measurements to evaluate the principal characteristics of an electroabsorption modulator with passive sections on either ends of its active layer fabricated on an InP substrate. We show here that careful monitoring of the reflections at the transition regions (passive to active and vice versa), and also transmission of a broadband OLCR (∼55 nm wide and centered at ∼1.56 μm) probe light as a function of applied reverse bias, permit a nearly complete assessment of the device. For example, in addition to assessing the quality of the transition regions, such a study further leads to the determination of the optimal operation wavelength and also the modulation depth of the device.

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

We show for the first time the potential of the linear spectrogram method for the extraction of phase shifts induced by slow and fast light in an InGaAsP/InP semiconductor optical amplifier. Optical filtering using this technique exhibits a 6-fold improvement of the optical delay at 10 GHz and an enhanced slow-light related effect bandwidth.

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.

A 1.55 mum VECSEL with a metal-GaAs/AlAs hybrid metamorphic mirror optimized for high power operation has been assembled with a fast saturable absorber mirror (SESAM) in a four mirror cavity to generate mode-locked pulses with an RF linewidth < 20 kHz at a frequency of 2 GHz.

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.

Microwave frequency properties of truly 3-dimensional confined quantum dot lasers on InP substrate are thoroughly investigated for the first time. A relaxation frequency of 3.7 GHz and a Henry factor of ~7 are measured.

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.

Electrical spectrum line-width is reduced in mode-locked FP 1.55 μm-QD laser diode through optical confinement factor optimization. From optimized structures, we obtained nearly Fourier-transform limited pulses at 10 GHz, with an averaged width of 8 ps over 10 nm.

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.

Large positive detuning is used for self thermal compensation of threshold and power variation in AlGalnAs DFB. 25 km uncompensated and non-amplified SMF transmissions are demonstrated at a constant bias current from 20°C to 90°C.

Quantum dot material offers new perspectives for the development of low-cost, high performing semiconductor laser and amplifiers. The 3D quantification of the energy levels in quantum dots leads to potentially high optical gain and efficiency, and thus the possibility of operation at lower currents than quantum well devices. Better resistance to temperature change, lower linewidth enhancement factor and lower noise are also expected. The elaboration and the basic properties of the quantum dot material for laser and amplifiers will be first presented. Then the main device performance will be detailed, as well as the disruptive properties already obtained. Potentials for microwave photonic applications will be discussed.

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.

For high speed remote colorless modulation in FTTH technology, a new 10Gbit/s monolithically integrated amplified reflective electroabsorption modulator (R-EAM-SOA) is demonstrated over 50nm spectral range and over 20°C-60°C, with excellent eye diagrams.

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.

By enhancing excitonic absorption in a new design of a polarization independent EA modulator, a 50 nm flat absorption spectrum, 42 GHz bandwidth devices together with 14-30 dB/V modulation sensitivity are obtained for 75 /spl mu/m long devices.

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.