Kais Dridi

Narrow Linewidth 1550 nm Corrugated Ridge Waveguide DFB Lasers

We report on the design and characterization of InP-based multiple quantum well corrugated ridge waveguide distributed feedback diode lasers operating at 1550 nm. Third-order gratings have been etched along the sidewalls of the ridge waveguide using the standard I-line stepper lithography technique with an inductively coupled reactive ion etching process. An as-cleaved 1500-μm-long laser diode shows stable continuous wave single-mode operation at 1550 nm with high side-mode suppression ratios (>50 dB), a temperature-dependent wavelength shift dλ/dT ~0.095 nm/°C, and output powers ≥7 mW at 25 °C. Linewidth determination has been carried using the delayed self-heterodyne interferometric technique. Narrow linewidths (≤250 kHz) have been observed for a wide range of current injection, with a minimum of 184 kHz at 300 mA.

Dynamic Analysis of High-Order Laterally Coupled DFB Lasers Using Time-Domain Traveling-Wave Model

This paper describes the application of a time-domain modeling approach for a laterally coupled distributed feedback (LC-DFB) semiconductor laser for the first time. We numerically study the effect of the radiation modes on LC-DFB laser properties. We integrate the Streifers coefficients, which represent the effects of radiation and evanescent modes into the time-domain coupled-wave equations. High-order corrugated gratings with λ/4 phase-shift are analyzed, where the degree of longitudinal spatial hole burning can be effectively reduced by means of fine tuning of the grating duty cycle. Additionally, we show a remarkably enhanced side-mode suppression ratio (SMSR). For example, for the third-order gratings with a 50% duty cycle, an SMSR as high as 45 dB can be predicted.

Narrow linewidth two-electrode 1560 nm laterally coupled distributed feedback lasers with third-order surface etched gratings

We report on the design and characterization of a re-growth free InGaAsP/InP multiple quantum well two-electrode laterally coupled distributed feedback (LC-DFB) lasers. Third-order surface etched gratings have been defined on the ridge sidewalls along the laser cavity by means of stepper lithography. The lasers oscillate in single-mode around 1560 nm with high side mode suppression ratios (>52 dB), a wavelength tuning (≥ 3nm), an output power (≥ 6 mW), and narrow linewidth (<170 kHz) under various current injection ranges at room temperature. A minimum linewidth of 94 kHz has been recorded for 1500 µm-long two-electrode LC-DFB laser while providing non-uniform current injection through the two electrodes. The effect of the width of the inter-electrode gap on these different performance measures is also studied.

Numerical Study of Dual Mode Generation Using a Sampled-Grating High-Order Quantum-Dot Based Laterally-Coupled DFB Laser

We propose a fabrication-friendly dual-mode laser source based on a sampled surface-grating, quantum-dot (QD), third-order, and laterally-coupled distributed feedback (LC-DFB) laser composed of alternating grating and Fabry-Perot sections. The dynamic behavior of this device is investigated through numerical modelling, and mode spacing in the millimeter-wave domain (60 GHz) was achieved. We extended a time-domain travelling-wave algorithm, including Streifers terms, to numerically study the dynamic behavior of the modified high-order LC-DFB lasers. We also incorporated an active QD region via a set of rate equations that considers both in homogeneous broadening because of spatial distribution of QD and homogeneous broadening because of the scattering or polarization dephasing rate. It was found that stable dual mode operation in the millimeter-wave range can be achieved with a dual-side-mode-suppression-ratio as high as ~ 50 dB.

Time-Domain Analysis of Third-Order Quantum-Dot-Based Laterally-Coupled Distributed Feedback Lasers Using Travelling-Wave Approach

In this paper, we present a time-domain (TD) coupled model suitable to investigate high-order λ/4 phase-shift grating quantum-dot (QD) based laterally-coupled distributed feedback (LC-DFB) laser. First, by integrating the Streifers coefficients, we include the effects of radiation and evanescent modes into the TD coupled wave equations, and hence we investigate the effect of the radiation modes. Then, via a well-established set of rate equations coupled with the travelling field propagation equations, population dynamics in the QD region are modeled and the homogeneous and inhomogeneous broadening of, respectively, the whole QD ensemble and each QD inter-band transition are properly taken into account in the model. Finally, we consider the coupling between forward and backward electric fields due to the grating via the travelling-wave approach. This approach advances the impact of radiating partial waves in high-order QD-LC-DFB lasers. It is shown that, in particular for third-order rectangular grating, longitudinal spatial hole-burning is highly reduced, high single mode suppression ration (60 dB) is obtained and larger frequency modulation is achieved thanks to the fine engineering of the grating features and the particular properties of QD. Eventually, such results highlight the beneficial effect of considering high-order grating QD-LC-DFB lasers for better longitudinal-mode discrimination and high device performances.

On the performance of fabricated third order laterally coupling distributed feedback 1310nm lasers

We report here on the design, fabrication and performance characteristics of 1310 nm laterally coupled distributed-feedback (LC-DFB) semiconductor lasers. We describe the epidesign of these InGaAsP/InP quantum-well ridge waveguide LC-DFB lasers, which were fabricated in a single epitaxial growth step using stepper lithography and inductively-coupled reactive-ion as well as wet chemical etching. Such a DFB fabrication process avoids the commonly required regrowth steps in conventional DFB laser fabrication processes. The lithographic tolerance has been enhanced by employing higher order gratings, yielding lasers more amenable to mass-manufacturing. In this work, uniform third-order gratings have been lithographically patterned out of the waveguide ridge built on an epitaxial structure conceived for 1310 nm lasing wavelength. We now report on L-I measurements, threshold determination and sidemode suppression ratios (SMSR) for a broad distribution of devices. These fabricated lasers achieve stable single mode lasing with SMSR as high as 54 dB under CW operation at room temperature, albeit with thresholds higher than anticipated.

Narrow linewidth 1560 nm InGaAsP split-contact corrugated ridge waveguide DFB lasers.

We demonstrate a split-contact corrugated ridge waveguide InGaAsP distributed feedback laser at 1560 nm. The laser cavity has been defined with uniform third-order gratings etched along the sidewalls of the ridge waveguide. The gratings were fabricated using a standard I-line stepper lithography technique along with an inductively coupled reactive ion-etching process. Stable single-mode operation has been achieved with side-mode suppression ratios ≥50  dB, output powers ≥7  mW, a wavelength tuning range ≥2.3  nm, and narrow linewidths (≤140  kHz) for different biasing conditions, with a minimum of 70 kHz. The effect of p-contact partition on device performance is also studied.

Multi-electrode laterally coupled distributed feedback InGaAsP/InP lasers: a prescription for longitudinal mode control

Photonic Integrated Circuits (PICs) enable photons as data carriers at a very high speed. PIC market opportunities call for reduced wafer dimensions, power consumption and cost as well as enhanced reliability. The PIC technology development must cater for the latter relentless traits. In particular, monolithic PICs are sought as they can integrate hundreds of components and functions onto a single chip. InGaAsP/InP laterally-coupled distributed feedback (LC-DFB) lasers stand as key enablers in the PIC technology thanks to the compelling advantages their embedded high-order surface-gratings have. The patterning of the spatial corrugation along the sidewalls of the LC-DFB ridge, has been established to make the epitaxial overgrowth unnecessary thereby reducing the cost and time of manufacturing, and ultimately increasing the yield. LC-DFBs boast a small footprint synonymous of enhanced monolithic integrate-ability. Nonetheless, LC-DFBs suffer from the adverse longitudinal spatial hole burning (LSHB) effects materialized by typically quite high threshold current levels. Indeed, the carrier density longitudinal gradient- responsible for modes contending for the available material gain in the cavity- may be alleviated somewhat by segmenting the LC-DFB electrode into two or three reasonably interspaced longitudinal sections. In this work we report on the realization and performance of various electrode partition configurations. At room temperature, the experimental characterization of many as-cleaved LC-DFB devices provides ample evidence of superior performance such as a narrow linewidth (less than 400 kHz), a wide wavelength tune-ability (over 4 nm) and a hop-free single mode emission (side mode suppression ratio (SMSR) exceeding 54dB).

Narrow-linewidth three-electrode regrowth-free semiconductor DFB lasers with uniform surface grating

There has been much interest in developing low-cost laser sources for applications such as photonics integrated circuits and advanced coherent optical communications. The ultimate objectives in this development include wide wavelength tunability, a narrow linewidth, and an ease of integration with other devices. For this purpose, semiconductor surface grating distributed feedback (SG-DFB) lasers have been introduced. SG-DFB manufacturing consists of a unique sequence of planar epitaxial growth resulting in a major simplification to the fabrication process. SG-DFB lasers are highly monolithically integrate-able with other devices due to their small footprint. The segmentation of the built-in top electrode helps to alleviate the adverse spatial-hole burning effects encountered in single-electrode devices and brings hence significant enhancements to the laser performance. For the first time, we report here on the design, fabrication, and characterization of InGaAsP/InP multiple-quantum-well (MQW) SG-DFB lasers with uniform third-order surface grating etched by means of stepper lithography and inductively-coupled reactive-ion. The uncoated device reported here is 750 μm-long SG-DFB laser whose central and lateral top electrodes are 244 μmlongs each, separated by two 9 μm-long grooves. The experimental characterization shows stable single mode operation at room temperature under uniform and non-uniform injection. High side mode suppression ratios (SMSRs) (50-55dB) under a wide range of injection current have been discerned as well. A relatively broad wavelength tuning (<4nm) has also been observed. Moreover, a narrow linewidth (<300 kHz) has been recorded for different injection currents.

Dynamic analysis of high-order quantum dot based laterally-coupled distributed feedback lasers

A time-domain traveling wave algorithm is extended to investigate high-order quantum dot based laterally-coupled distributed feedback semiconductor lasers. The effect of radiation modes in laser performance is included via Streifer’s terms. We calculate the optical gain spectra based on a coupled set of rate equations and taking into account both inhomogeneous broadening due to dot size fluctuation and homogeneous broadening due to polarization dephasing. It was found that, for third-order quantum dot based laterally-coupled distributed feedback lasers; a stable single mode operation with high SMSR can be achieved by means of fine tuning of the grating duty cycle