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Low-excess-loss arrayed waveguide gratings are enabled by unique application of deep UV lithography in InP integrated photonics through reduced feature sizes and, more specifically, well-resolved inter-waveguide gap dimensions. Submicrometer wafer-flatness is shown to be required to achieve the critical dimension uniformity better than 10 nm on 3-in substrates. Arrayed waveguide grating devices were fabricated and the effect of inter-waveguide gap scaling on the excess losses was measured and compared to simulations. Excess losses down to 0.15 dB were demonstrated to be lower than predicted with the 2-D simulations. The tapering of the etch depth inside the gaps due to the lag effect of the etch process may explain the improvements.

An array of monolithic wide-tunable lasers is integrated using selective area growth to shift the bandgap of their gain section. A gap-free tuning is demonstrated from the combination of the tuning ranges of the lasers, and single-mode operation is verified.

Selective area growth is used for the first time in the TU/e generic integration platform to modify independently the bandgap of active sections. A chip combining 4 tunable lasers with shifted wavelength ranges has been fabricated. A 96 nm wide tuning range is demonstrated.

We present our work on the realization of integrated III/V-on-silicon integrated mode-locked lasers. We demonstrate 1 GHz repetition rate mode-locked lasers with a spectrum spanning more than a 1 THz.

ArF deep UV (193 nm) lithography was successfully applied to fabricate Arrayed Waveguide Gratings in generic Indium Phosphide technology. The sub-dB transmission losses demonstrate the advantages of scaling down the minimum feature size to 100 nm.

We report a novel type of monolithically integrated tunable semiconductor laser. The tuning is achieved by three intracavity Mach–Zehnder interferometers, realized in passive waveguides and using voltage-controlled electro-optic phase modulators requiring only four control voltages. The potential of the design is demonstrated by a realized laser system that shows an optical linewidth of 363 kHz, output power of 3 mW, and a record tuning range of 74.3 nm. Such a continuous wavelength span is in excess of any monolithic semiconductor laser reported up to date. Precision of the tuning mechanism is demonstrated by a scan over a 0.89-GHz-wide absorption line of acetylene. The laser design is suitable for a number of applications, including gas spectroscopy, telecommunication, and optical coherence tomography. The laser has been fabricated in a multi-project wafer run on an indium phosphide-based generic photonic foundry platform and demonstrates the potential of these technology platforms.

Picosecond-pulse III-V-on-silicon mode-locked lasers based on linear and ring extended cavity geometries are presented. In passive mode-locked operation a 12 kHz -3dB linewidth of the fundamental RF tone at 4.7 GHz is obtained for the linear cavity geometry and 16 kHz for the ring cavity geometry. Stabilization of the repetition rate of these devices using hybrid mode-locking is also demonstrated.

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 (

In this paper, we present the detailed characterization of a semiconductor ring passively mode-locked laser with a 20 GHz repetition rate that was realized as an indium phosphide based photonic integrated circuit (PIC). Various dynamical regimes as a function of operating conditions were explored in the spectral and time domain. A record bandwidth of the optical coherent comb from a quantum well based device of 11.5 nm at 3 dB and sub-picosecond pulse generation is demonstrated.

Optical sensing offers unrivalled precision with real-time monitoring, but the complexity in implementing the optical sources has so far limited deployments to high value measurement systems. Innovations in photonic integration are beginning to enable breakthroughs in terms of cost, size and performance. Integrated sources and readouts can be created with large-scale semiconductor wafer production techniques. InP integrated photonics is able to combine best-in-class components including the lasers and amplifiers within one photonic chip. The chip-scale integration of complete circuits enables on-chip stabilisation and environmental corrections for further advances in measurement precision and at lower power consumption.

Generic photonic integration technology platforms allow for design and fabrication of large complexity application specific photonic integrated circuits. Monolithic active-passive integration on indium phosphide substrate naturally enables a reliable co-integration of optical gain elements and therefore on-chip realization of advanced laser systems. An overview of multi-wavelength sources in the form of photonic integrated circuits fabricated using such integration technology for applications in telecommunications, sensing, millimeter and terahertz generation will be given.

Progress on the development of a long wavelength (∼2 µm) generic monolithic photonic integration technology on indium phosphide substrate and a novel concept of a tunable laser realized as a photonic integrated circuit using such technology are presented. Insights into the development of active and passive waveguide structures which are used to define a limited set of on-chip functionalities in the form of building blocks will be given. A novel tunable laser was proposed and designed using such predefined set of basic building blocks. The laser geometry features an intra-cavity wavelength tuning mechanism based on asymmetric Mach-Zehnder interferometers in a nested configuration. The photonic integrated circuit chip was fabricated within the first long wavelength multi-project wafer run. The experimental evaluations of the fabricated device show a record tuning range of 31 nm around 2027 nm and successful measurements of a 0.86 GHz wide absorption line of carbon dioxide. These results provide a demonstration of a fully functional photonic integrated circuit operating at wavelengths that are much longer than those in the typical telecommunication windows as well as the use of indium phosphide based generic photonic integration technologies for gas sensing applications.

The performance of integrated planar waveguide mode locked lasers can be enhanced using the available photonic integration platform technology in indium-phosphide. Extended cavity mode locked oscillators including DBR mirrors and phase modulators can be realized at telecom wavelengths to improve performance and control over the device. Integrated pulse shapers and special amplifiers can be used to improve the output properties further.

A novel operation mode field reconfigurable DBR laser is designed, realized and investigated experimentally. With different controlling of the same hardware, a shared-cavity six-section DBR laser diode can be flexibly configured to operate as a continuous wave or a pulsed wave laser.

We present our recent work on the realization of III-V-on-silicon mode-locked lasers and integrated nonlinear waveguides for the realization of integrated frequency combs.

Monolithic integration of four widely tunable extended cavity lasers suitable for gas detection is presented. Each laser features a precise, grid-less tuning mechanism with a low-linewidth, single-mode output over a wide wavelength range of 74nm.

The authors present the design and characterization of a novel integrated two-section discrete mode index patterned diode laser source. The two slotted regions etched into the laser ridge waveguide are formed in the same fabrication step as the ridge, thus avoiding the requirement for complex lithography and regrowth steps. The laser is encased in a temperature-controlled butterfly package, which simplifies the static and dynamic measurements. Initial static characterization of this two-section laser shows that the injection, from the master laser to the slave laser, enhances the slave's emission side-mode suppression ratio from 30 dB to over 50 dB and its relative intensity noise is reduced from about -129.3 dB/Hz to -142.6 dB/Hz. Subsequent dynamic characterization then shows that the modulation bandwidth of the laser can be improved via injection to about three times the inherent free-running bandwidth. Hence, optical injection from master section into slave section enables the improvement of various parameters, which makes this two-section device attractive as a transmitter in optical communication systems.

For the first time we demonstrate an anti-colliding mode-locked laser implemented on a III-V-on-silicon platform. In passive mode-locked operation a 1.7kHz 3dB linewidth of the fundamental RF tone at 4.83GHz is obtained.

A review is given of a number of lasers in a form of photonic integrated circuits realized on InP substrate using a generic integration approach. The potential of these photonic circuits lies in their compactness, low power consumption, and significant reduction of fabrication cost by realization in generic foundry runs. Generic integration platforms offer the possibility of realizing functionally advanced photonic circuits using combinations of just a few standardized and parameterized building blocks. This vibrant field opens new doors to innovative product development for SMEs as well as curiosity-driven research.

A tunable laser for single line gas spectroscopy is realized as a monolithic photonic integrated circuit in an InP based generic foundry platform. The laser operates at wavelengths around 2.0 μm and has a tuning range of 22 nm.

In this paper we present our recent progress on 2.5 GHz mode-locked, quantum well lasers operating at 1550 nm. Two such lasers are monolithically integrated on an InP substrate. Stable passive and hybrid mode-locking of both lasers operating at the same time with a small repetition rate difference is demonstrated.

We propose a simple potentially integrable configuration for expanding a wavelength tunable comb by cascading gain switched Fabry-Pe´rot lasers. A 10GHz spaced comb, exhibiting 13 coherent low-linewidth tones within a 3 dB window, and tunable over 20 nm is demonstrated.

A passively mode locked extended cavity quantum well ring laser at 1.58 µm with 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 33mm long cavity contains gain, saturable absorption and passive waveguide sections as well as a phase shifter sections to enable fine tuning of the spectral position of the lasing modes. Passive mode-locked operation and with wavelength tuning of the laser modes are experimentally demonstrated. This laser is the lowest reported repetition rate for a monolithically integrated ring laser.

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.

A tunable laser operating from 2015 – 2040 nm realized as a monolithic InP photonic integrated circuit is presented. The laser uses an intracavity tuning mechanism based on parallel asymmetric Mach-Zehnder interferometers with electro-refractive modulators. The device is intended for a single line gas spectroscopy and was designed and fabricated using a generic integration technology platform.

Spectral phase control of optical pulses is often required to generate short pulses, and an important application of a pulse shaper is spectral chirp/dispersion (pre-) compensation. In this paper, we present the pulse shaping/compression capability of a monolithically integrated optical pulse shaper. Chip fabrication has been carried out in a standardized generic photonic integration platform which is available in the framework of European FP7 project EuroPIC. A key capability of this platform is the active-passive integration scheme which allows direct integration of active components such as semiconductor optical amplifiers (SOAs) with passive elements such as arrayed waveguide gratings (AWGs) and phase modulators (PMs) on a single photonic chip.

Modal gain characterization of mid-infrared semiconductor optical amplifiers intended for an active-passive integration platform is presented. Measured gain profiles reveal the peak values at around 2.07μm and 3dB bandwidth up to 27nm.

We present the first 320Gb/s all-optical clock recovery by exploiting single Quantum Dash MLL to generate 40GHz synchronized optical clock pulse with 71fs timing jitter. 320Gb/s all-optical demultiplexing operation with 1dB BER penalty was demonstrated.

In this paper, we present the experimental investigation of the switching-on and passive mode-locking times of a Fabry-Perot quantum dash laser diode. Their values are 30ns and 8ns respectively. These times are measured in order to study the phenomenon of mode-locking in this device and its potential application for packet switching networks.

A wavelength tunable optical comb is generated based on the gain-switching of an externally seeded Fabry-Pérot laser diode. The comb consists of about eight clearly resolved 10 GHz coherent sidebands within 3 dB spectral envelope peak and is tunable over the entire C-band (1530 to 1570 nm). The optical linewidth of the individual comb tones is measured to be lower than 100 kHz, and the RIN of the individually filtered comb tones (-120 dB/Hz) is shown to be comparable to the entire unfiltered comb (-135 dB/Hz). Besides, expansion of the tunable gain switched comb is achieved with the aid of an optical phase modulator, resulting in near doubling of the number of comb tones.

Linewidth narrowing of the radio frequency beat-tones and the optical-modes is experimentally investigated in a ∼40 GHz quantum-dash mode-locked laser diode subject to optical injection of 10 GHz pulses. In comparison to the 75 kHz linewidth exhibited by the beat-tones in passive mode-locking conditions, a remarkable reduction to less than 8 Hz is achieved when the laser is under optical injection. From this beat-tone signal, an integrated root-mean-square timing jitter of 64 fs is calculated. In addition, a quadratic profile of the optical linewidth with the wavelength is observed in active locking, reaching a minimum of 1.7 MHz for the longitudinal modes around 1530 nm and progressively increasing to 37.4 MHz for modes at 1525 nm.

In this paper, a detection scheme based on four wave mixing in a semiconductor optical amplifier (SOA) is used to measure the frequency and bandwidth of the optical terahertz beat-tone signal generated by a passively mode locked semiconductor laser. Two signals from external cavity lasers are injected into an SOA, which acts as a local oscillator at their detuning frequency. The device under test is a passively mode locked laser with a beat-tone frequency in the terahertz spectrum. Its optical signal is injected in the SOA, which also acts as a frequency mixer. The frequency and linewidth of the terahertz signal are then measured by retrieving the intermediate frequency detected by a low bandwidth photodiode and an electrical spectrum analyser.

We present a linear self-referenced measurement of the spectral amplitude and phase of a free-running quantum-dash modelocked laser diode. The technique is suitable for measuring optical signals with repetition rates up to 100 GHz. In contrast to many other linear techniques it requires no external electronic clock synchronized to the signal under test. Using this method we are able to compensate for the intracavity dispersion of the diode to demonstrate 500 fs pulses at a repetition rate of 39.8 GHz. We also use the technique to characterize the dependence of the diode’s intracavity dispersion on the applied current.

Optical frequency comb sources (OFCS) have recently attracted a lot of interest due to wide ranging applications such as optical arbitrary waveform generation [1], photonic microwave signal generation [2], optical signal processing [3] and multi-carrier spectrally efficient transmission techniques with the sub-channel spacing equal to the symbol rate of each sub-channel [4]. OFCS with good spectral flatness, stability and low linewidth are highly desirable for such applications. One of the conventional approaches used in realizing a comb source is based on mode-locked semiconductor and fibre lasers [5]. Although this technique can generate multi-carrier signals spanning over a wide bandwidth, it inherently suffers from cavity complexity and does not offer the free spectral range (FSR) tunability since the comb line spacing is fixed by the cavity length of the laser. Moreover, the optical linewidth of the individual comb lines can be relatively large (several MHz) preventing higher order (or low baud rate) advanced modulation formats to be imposed. Another technique that has been reported entails the use of a single, cascaded or dual drive Mach-Zehnder modulators (MZM) to generate the phase correlated optical frequency comb [6]. Although this technique provides a relatively flat optical comb, the large insertion loss of the modulator coupled with the modulation efficiency can prove prohibitive. The extra optical component also adds to the cost and complexity of the transmitter, rendering this technique unsuitable for short reach applications.

There is a vast interest in multi-wavelength light sources which can find applications in optical communications [1], and photonic generation of millimetre and terahertz signals [2]. For such applications highly coherent and stable optical comb sources, with uniform power distribution among frequency components are desirable. Conventional comb sources are mainly based on mode-locked semiconductor and fibre lasers. Both are penalized by fixed free spectral range (FSR), and complexity of the epitaxial growth in the first case, and stability issues due to long cavity lengths in the latter. Another technique, which offers the advantage of tuneable FSR, entails the use of electro-optic modulators. This however, requires the use of expensive dual drive modulators [3], or a series of cascaded modulators [4], in order to achieve a broad and relatively flat comb.

Synchronization of a 40 GHz quantum-dash mode-locked (ML) Fabry-Perot laser diode with optically injected pulse streams is experimentally studied. Injected signals consist of nonmodulated and modulated trains of 1.6 ps pulses at various repetition rates, ranging from 10 to 160 GHz and 10 to 160 Gbps, respectively. Subharmonic, fundamental, and harmonic synchronization of the ML laser allows retrieval of stable 40 GHz clock pulses featuring a width of 1.8 ps. Frequency components at 10 and 20 GHz do not create any amplitude modulation on the recovered 40 GHz clock pulses when injecting signals at 10 and 20 GHz/Gbps. In addition, external synchronization of the laser with pulse streams at 80 and 160 GHz/Gbps is sustained despite the absence of significant components at or below 40 GHz.

Quantum-dash modelocked laser diodes (QD-MLLD) are capable of producing short optical pulses at extremely high repetition rates. As such they are ideally suited to many telecommunications applications [1]. In this paper we present a linear self-referenced measurement of the spectral amplitude and phase of a free-running quantum-dash modelocked laser diode. The technique is suitable for measuring optical signals with repetition rates up to 100 GHz. In contrast to many other linear techniques it requires no external electronic clock synchronized to the signal under test. Using this method we show that compensating for the intra-cavity dispersion of the diode results in 500 fs pulses at a repetition rate of 39.8 GHz. The measurement technique is based on the stepped-heterodyne method presented in Ref. [2]. The signal under test is mixed with a CW narrowband optical local oscillator (LO) and the combined signal detected by a high-speed photodiode, mixed with an electronic LO, and then recorded on a real-time oscilloscope. When the optical LO is placed between two adjacent signal modes the resultant beat signals can be analysed to determine not only the power of each of the signal modes, but also the phase difference between them [2]. Stepping the optical LO across all signal modes allows for a complete measurement of the spectral amplitude and phase of the signal.

An all-optical approach based on nonlinear interactions inside a semiconductor optical amplifier for measuring the THz beat-tone of a passively mode-locked laser is proposed. This novel approach can be applied to beat-tones in the range from GHz to few THz.

A narrowband terahertz signal generated by a uni-travelling carrier photodiode (UTC-PD) interfaced with a dual-mode Fabry-Perot laser diode is demonstrated. A beat tone corresponding to the free spectral range is generated on the UTC-PD, and radiated by a transverse-electromagnetic-horn antenna. All components involved in this experiment operate at room temperature. The terahertz signal at a frequency of 372 GHz is recorded, and the linewidth is 17 MHz. The linewidth and the tunability of the emitted terahertz wave are analyzed, as a function of the laser bias.

An experimental analysis of the timing jitter associated with sub-picosecond pulses produced from a quantum dash passively mode-locked Fabry-Perot laser is produced. Moreover, application as an all-optical clock recovery function for a 40Gb/s data rates with non-return-to-zero (NRZ) modulation format is demonstrated using this laser.

A bulk semiconductor optical amplifier (SOA) utilizing a multi-contact biasing method is characterized as a function of the bias current supplied to each section Firstly, amplified spontaneous emission spectra and characteristic light-current profiles are analyzed. Single-pass gain and noise figure of the SOA are then assessed by injecting a continuous wave input beam. Finally, the amplification of a 10 Gb/s (215-1) long pseudo random bit sequence signal is analysed. The obtained results, particularly at a bias condition of 90mA-50mA-10mA, reveal the potential of this device as a low noise figure in-line amplifier.

Timing-jitter measurements in optically generated subpicosecond pulses by a quantum-dash passively mode-locked semiconductor laser as a function of the bias current are reported. All the measurements are retrieved from a second-harmonic-generation frequency-resolved optical gating system. A decreasing trend in the pulse width and the associated timing jitter is found with the bias current. Additionally, the optical and mode-beating linewidths are analyzed in terms of both the mode wavelength and the bias current. From our results, we can conclude that once the optical modes are phase locked, the optical linewidth associated to every individual longitudinal mode of the device under test does not have a significant impact on the mode-beating signal on neither the pulse width nor its respective timing jitter.

Wave-mixing at 370-GHz in a SOA and FP semiconductor laser is investigated by using a FROG-system. A comparison of the optical time-fluctuations measured at their output stresses the importance of a resonant cavity in THz-signals generation from semiconductor optical devices.

International audience; A narrowband terahertz signal generated by a unitravelling carrier photodiode (UTC-PD) interfaced with a dual-mode Fabry–Pérot laser diode is demonstrated. A beat tone corresponding to the free spectral range is generated on the UTC-PD, and radiated by a transverse-electromagnetic-horn antenna. A terahertz signal at a frequency of 372 GHz, featuring a linewidth of 17 MHz is recorded by a subharmonic mixer coupled to an electrical spectrum analyzer. All components involved in this experiment operate at room temperature. The linewidth and the frequency of the emitted terahertz wave are analyzed, along with their dependency on dc-bias conditions applied to laser diode.

An experimental analysis on the quality of 40-GHz radio-frequency signals generated by various passively mode-locked semiconductor lasers is addressed. The analysis is performed considering the frequency linewidth of 40-GHz optically generated signals and the number of longitudinal modes selected by the cavity of each laser under study. Four of these devices are multi-quantum wells InAlGaAs Fabry–Perot lasers. They have been engineered to exhibit a specific number of longitudinal modes: 4, 5, 10, and 22 modes, respectively. Another device under test is a bulk distributed Bragg reflector laser exhibiting 3 lasing modes. The last device under study is a quantum-dash Fabry–Perot laser characterized by 40 lasing modes. From our experimental results it appears that, regardless the nature of the device cavity and active media, the strength of the passively mode-locked mechanism might be enhanced with the number of longitudinal modes oscillating into the laser cavity, allowing a reduction in the frequency linewidth.

Generation of sub-picosecond pulses by a dc-biased passively mode-locked Fabry-Perot laser is demonstrated. By using a tunable band-pass filter, it is observed that the width of the generated pulses decreases in direct proportion to the optical modes emitted by the laser. Furthermore, performing a passive compression by a piece of single mode fiber, we demonstrate the generation of 720 fs pulses by this type of mode-locked Fabry-Perot laser.

A technique to measure a terahertz wave generated by spectrum tailored Fabry–Pérot lasers (FP) is assessed. A dc-biased and 25 °C temperature controlled FP is probed by a continuous wave signal, tuned at 20 nm away from its lasing modes. With a 0.02 nm resolution optical spectrum analyzer (OSA), the terahertz generated signal frequency is measured from the interval between the probe and its side-band modulations. The terahertz waves emitted by these FPs are measured at 370±5 GHz and at 1.157±0.005 THz, respectively, within a precision set by our OSA. The origin of the terahertz wave is due to passive mode-locked through intracavity four-wave-mixing processes.

Generation of narrow microwave signals produced from the mode beating of a DBR laser is presented. The application of this process to the cw-THz wave generation is also demonstrated using a slotted FP laser.

In this paper, Cassidy's method is presented and is applied to measure the linewidth enhancement factor (LEF) of a 370 GHz self-pulsating Fabry-Perot laser. The importance of the LEF is addressed, the method is detailed, and the device under test is presented. It exhibits a self-modulation at 370 GHz even though it is DC biased. The measured LEFs vary according to the wavelength, values of 4 have been measured at threshold current, which is typical in the case of multi-quantum well lasers. In this paper we propose to present measurement of the linewidth enhancement factor (LEF) in semiconductor laser based, 370 GHz source generator. First we explain the origin of LEF in semiconductor material, then we present several techniques to measure it. We present a computational simulation using modelled ASE spectra, and in part 4, we detail our device and experimental set-up and provide some results. The linewidth enhancement factor (LEF) or alpha parameter is a distinguishing feature of semiconductor devices. Semiconductor devices generally have a larger linewidth than other solid state lasers. This broadened linewidth leads to effects such as mode instability, filementation in broad area devices and frequency chirping under modulation. This last effect is of particular interest, especially in the field of optical communications. It can be suppressed if the LEF is reduced. Therefore in the design of semiconductor lasers or semiconductor amplifiers (SOA), a number of factors have to be taken into consideration, but one of the most important of these is the linewidth enhancement factor. For instance, when the gain of an SOA is affected by the injection of a pulsed source, refractive index changes caused by changes in carrier density will lead to an instantaneous variation of the frequency. This effect is exacerbated as the gain is saturated.