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Optical frequency combs emerge as a promising technology that enables highly sensitive, near-real-time spectroscopy with a high resolution. The currently available comb generators are mostly based on bulky and high-cost femtosecond lasers for dense comb generation (line spacing in the range of 100 MHz to 1 GHz). However, their integrated and low-cost counterparts, which are integrated semiconductor mode-locked lasers, are limited by their large comb spacing, small number of lines and broad optical linewidth. In this study, we report a demonstration of a III-V-on-Si comb laser that can function as a compact, low-cost frequency comb generator after frequency stabilization. The use of low-loss passive silicon waveguides enables the integration of a long laser cavity, which enables the laser to be locked in the passive mode at a record-low 1 GHz repetition rate. The 12-nm 10-dB output optical spectrum and the notably small optical mode spacing results in a dense optical comb that consists of over 1400 equally spaced optical lines. The sub-kHz 10-dB radio frequency linewidth and the narrow longitudinal mode linewidth (

We present an investigation of an InP quantum-well-based integrated extended cavity passively mode-locked laser which shows extra broad frequency comb generation. The ring laser was characterized in frequency and time domains for a range of the current levels injected in the semiconductor optical amplifier. The study showed an increase of the bandwidth to over 40 nm at the −20 dB −20 dB level. The coherence between the longitudinal modes in the wide comb is demonstrated by the characterization of a spectrally filtered signal in time and RF domains. The relative time delay across the optical comb was measured.

Residual amplitude modulation in integrated electro-optic InP-based phase modulators is measured and its effect in the Pound-Drever-Hall frequency stabilization aimed at 10kHz stability is investigated. Optimum operating conditions are presented.

Similarities and differences between photonic and microelectronic integration technology are discussed and a vision of the development of InP-based photonic integration in the coming decade is given.

In this paper a model and simulation results of integrated semiconductor passively modelocked ring lasers are presented. The model includes nonlinear effects such as two-photon absorption and a non-linear refractive index, a logarithmic gain-carrier relation, and concentration dependent radiative and non-radiative carrier recombination rates. The optical bandwidth of the system is controlled by a digital filter. The model has been used to simulate two geometries of ring modelocked lasers. The first is a symmetric design, where the two counter propagating pulses in the cavity experience the same amplification and absorption. The second is an asymmetric design where the differences for the two directions of pulse propagation are maximised. Simulation results show that a symmetrical cavity shows a several times wider window for its operating parameters for stable modelocking.

International audience; Measurements of the optical gain in a semiconductor laser using a 20 MHz resolution optical spectrum analyzer are presented for what is believed to be the first time. The high resolution allows for accurate gain measurements close to the lasing threshold. This is demonstrated by gain measurements on a bulk InGaAsP 1.5 m Fabry-Perot laser. Combined with direct measurement of transparency carrier density values, parameters were determined for characterizing the gain at a range of wavelengths and temperatures. The necessity of the use of a logarithmic gain model is shown.

International audience; We report on an extensive characterization of a 15GHz integrated bulk InGaAsP passively modelocked ring laser at 1530 nm. The laser is modelocked for a wide range of amplifier currents and reverse bias voltages on the saturable absorber. We have measured a timing jitter of 7.1 ps (20 kHz – 80 MHz), which is low for an all-active device using bulk material and due to the ring configuration. Measured output pulses are highly chirped, a FWHM bandwidth is obtained of up to 4.5 nm. Such lasers with high bandwidth pulses and compatible with active-passive integration are of great interest for OCDMA applications.

Using monolithic integration technology we have designed and fabricated tunable lasers in the 1.5 µm region with a demonstrated tuning range of 60 nm and single mode operation. This performance is achieved using intracavity tunable Mach-Zehnder interferometers that use voltage controlled phase modulators. In this paper we will discuss design considerations and advantages of such tunable lasers.

A ring mode-locked laser fabricated as a monolithic photonic integrated circuit using a InP based integration technology is presented. It generates an optical coherent comb around 1542 nm with a record 11.5 nm 3 dB bandwidth.

In this paper a study of waveguide photodetectors based on InAs/InP(100) quantum dot (QD) active material are presented for the first time. These detectors are fabricated using the layer stack of semiconductor optical amplifiers (SOAs) and are compatible with the active-passive integration technology. We investigated dark current, responsivity as well as spectral response and bandwidth of the detectors. It is demonstrated that the devices meet the requirements for swept-source optical coherent tomography (SS-OCT) around 1.7 µm. A rate equation model for QD-SOAs was modified and applied to the results to understand the dynamics of the devices. The model showed a good match to the measurements in the 1.6 to 1.8 µm wavelength range by fitting only one of the carrier escape rates. An equivalent circuit model was used to determine the capacitances which dominated the electrical bandwidth.

Using an integrated colliding-pulse mode-locked semiconductor laser, we demonstrate the existence of nonlinear dynamics and chaos in photonic integrated circuits (PICs) by demonstrating a period-doubling transition into chaos. Unlike their stand-alone counterparts, the dynamics of PICs are more stable over the lifetime of the system, reproducible from batch to batch and on faster time scales due to the small sizes of PICs.

This paper reviews the growth, characterization and device applications of self-assembled InAs/InP(1 0 0) quantum dots (QDs) formed by MOVPE. The problematic As/P exchange reaction during QD growth is suppressed by the insertion of a GaAs interlayer together with optimum growth conditions. This produces QDs with continuously tunable emission over the 1.55-μm wavelength region for fiber-based telecom applications. Device quality of these QDs is proven by continuous wave lasing at room temperature from the as-cleaved facets of Fabry–Perot narrow ridge-waveguide lasers implementing widely stacked QDs as gain medium. The low transparency current density of 6 A/cm2 per QD layer and low loss of 4.2 cm−1 are accompanied by a 80-nm wide gain spectrum. The deeply etched QD lasers possess similar threshold current densities as the shallowly etched ones and do not deteriorate with time, revealing that device performance does not suffer from sidewall recombination. This allows the fabrication of mono-mode and more compact devices with small bending radii, as demonstrated by the operation of a QD ring laser with 40-GHz free spectral range. Unpolarized emission from the cleaved side, important for the realization of polarization insensitive semiconductor optical amplifiers, is obtained by close stacking of QDs due to vertical electronic coupling. Sharp exciton–biexciton emission from a single QD around 1.55 μm is observed with clearly resolvable peaks above 70 K, which is required for single photon sources working at liquid nitrogen temperature for fiber-based quantum cryptography systems.

InP integrated photonics has become a critical enabler for modern telecommunications, and is poised to revolutionize data communications, precision metrology, spectrometry, and imaging. The possibility to integrate high-performance amplifiers, lasers, modulators, and detectors in combination with interferometers within one chip is enabling game-changing performance advances, energy savings, and cost reductions. Generic integration accelerates progress through the separation of applications from a common technology development. In this paper, we review the current status in InP integrated photonics and the efforts to integrate the next generation of high-performance functionality on a common substrate using the generic methodology.

In this paper we first present a brief overview of our work on indium phoshide integrated optical circuits. Integrated circuits can be produced that contain active components such as optical amplifiers and passive component such as waveguides, arrayed waveguide gratings and phase modulators. With this set of components complete laser systems can be designed and realized on a chip. Then we will present in what way our integration technology can be used to generate and utilize ultrafast optical pulses. Issues concerning the realization, operation and future developments will be discussed.

Wavelength-tunable InAs quantum dots (QDs) embedded in lattice-matched InGaAsP on InP(100) substrates are grown by metalorganic vapor-phase epitaxy (MOVPE). As/P exchange, which causes a QD size and an emission wavelength that are very large, is suppressed by decreasing the QD growth temperature and V–III flow ratio. As/P exchange, QD size and emission wavelength are then reproducibly controlled by the thickness of ultrathin [0–2 monolayers (ML)] GaAs interlayers underneath the QDs. Submonolayer GaAs coverages result in a shape transition from QDs to quantum dashes for a low V–III flow ratio. It is the combination of reduced growth temperature and V–III flow ratio with the insertion of GaAs interlayers of greater than 1 ML thickness which allows the tuning of the emission wavelength of QDs at room temperature in the 1.55 µm wavelength range. Temperature-dependent photoluminescence (PL) measurements reveal the excellent optical properties of the QDs. Widely stacked QD layers are reproduced with identical PL emission to increase the active volume while closely stacked QD layers reveal a systematic PL redshift and linewidth reduction due to vertical electronic coupling, which is proven by the fact that the linear polarization of the cleaved-side PL changes from in-plane to isotropic. Ridge-waveguide laser diodes with stacked QD layers for their active regions exhibit threshold currents at room temperature in continuous-wave mode that are among the lowest threshold currents achieved for InAs/InP QD lasers operating in the 1.55 µm wavelength range.

In this paper, we present an eight-channel polarization independent multiwavelength receiver which comprises an AWG demultiplexer monolithically integrated with eight twin-waveguide pin-photodetectors.

A mode-locked extended cavity quantum well ring laser at 1.58 μm with a repetition rate of 2.5 GHz in the form of a photonic integrated circuit is presented. The device is realized using InP-based active-passive integration technology. The 33 mm long cavity contains gain, saturable absorption, and passive waveguide sections as well as phase shifter sections to enable fine tuning of the spectral position of the lasing modes. Passive and hybrid mode-locked operation, along with the wavelength tuning of the laser modes, are experimentally demonstrated. In the passive mode-locking regime, a beat signal at the fundamental round trip frequency with a 3 dB bandwidth of 6.1 kHz is produced on a fast photo diode.

A 3 dB multimode interference (MMI) coupler optimised for low reflections is presented. The MMI was designed, fabricated and characterised. For comparison, MMIs with non-optimised layout have been included on the same sample. The measurement results show a reduction in reflectivities of more than 10 dB.

Reported is the first InAs/InP (100) quantum-dot (QD) laser operating in continuous-wave mode at room temperature on the QD ground state transition employing a single-layer of QDs grown by metal organic vapour phase epitaxy. The necessary high QD density is achieved by growing the QDs on a thin InAs quantum well (QW). These QDs on the QW laser exhibit a high slope efficiency and a lasing wavelength of 1.74 µm, which is important for biomedical applications.

The first butt joint integrated extended cavity InAs/InP (100) quantum dot (QD) Fabry-Perot laser emitting around 1.55 mum is demonstrated. Continuous wave lasing at room temperature on the QD ground state transition is achieved. The threshold current is comparable to that of all-active QD lasers. The Butt joint reflectivity for straight waveguides is below -40 dB.

First observation of passive mode-locking in two-section quantum-dot lasers operating at wavelengths around 1.55 mum is reported. Pulse generation at 4.6 GHz from a 9 mm long device is verified by background-free autocorrelation, RF-spectra and real-time oscilloscope traces. The output pulses are stretched in time and heavily up-chirped with a value of 20 ps/nm, contrary to what is normally observed in passively mode-locked semiconductor lasers. The complete output spectrum is shown to be coherent over 10 nm. From a 7 mm long device Q-switching is observed over a large operating regime. The lasers have been realized using a fabrication technology that is compatible with further photonic integration. This makes the laser a promising candidate for e.g. a mode-comb generator in a complex photonic chip.