F. Pommereau

Recent Advances on InAs/InP Quantum Dash Based Semiconductor Lasers and Optical Amplifiers Operating at 1.55

This paper summarizes recent advances on InAs/InP quantum dash (QD) materials for lasers and amplifiers, and QD device performance with particular interest in optical communication. We investigate both InAs/InP dashes in a barrier and dashes in a well (DWELL) heterostructures operating at 1.5 mum. These two types of QDs can provide high gain and low losses. Continuous-wave (CW) room-temperature lasing operation on ground state of cavity length as short as 200 mum has been achieved, demonstrating the high modal gain of the active core. A threshold current density as low as 110 A/cm2 per QD layer has been obtained for infinite-length DWELL laser. An optimized DWELL structure allows achieving of a T0 larger than 100 K for broad-area (BA) lasers, and of 80 K for single-transverse-mode lasers in the temperature range between 25degC and 85degC. Buried ridge stripe (BRS)-type single-mode distributed feedback (DFB) lasers are also demonstrated for the first time, exhibiting a side-mode suppression ratio (SMSR) as high as 45 dB. Such DFB lasers allow the first floor-free 10-Gb/s direct modulation for back-to-back and transmission over 16-km standard optical fiber. In addition, novel results are given on gain, noise, and four-wave mixing of QD-based semiconductor optical amplifiers. Furthermore, we demonstrate that QD Fabry-Perot (FP) lasers, owing to the small confinement factor and the three-dimensional (3-D) 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. These advances constitute a new step toward the application of QD lasers and amplifiers to the field of optical fiber communications

\mu

Self-organized InAs quantum-dot (QD) lasers emitting at 1.5 /spl mu/m were grown by gas source molecular beam epitaxy on (100) InP substrates. Room temperature continuous-wave (CW) operation of QD-based buried ridge stripe lasers is reported. We investigated experimentally the relevant CW performances of as-cleaved InP-based QD lasers for telecom applications such as temperature properties (T/sub 0/=56 K), infinite length threshold current density (J/sub /spl infin///spl sim/150 A/cm/sup 2/ per QDs layer) and internal efficiency (0.37 W/A). Lasing in pulsed mode is observed for cavity length as short as 200 /spl mu/m with a threshold current of about 37 mA, demonstrating the high gain of the QDs active core. In addition, the Henry parameter of these InP-based QD lasers is experimentally determined using the Hakki-Paoli method (/spl alpha//sub H//spl sim/2.2).

m

Reference LOEQ-ARTICLE-2004-023View record in Web of Science Record created on 2007-08-31, modified on 2017-05-12

Room temperature continuous-wave operation of buried ridge stripe lasers using InAs-InP (100) quantum dots as active core

We have fabricated and characterized two high-power high-linearity uni-traveling-carrier photodiode (UTC-PD) structures. The UTC performances are compared regarding their respective collector design. A -3-dB bandwidth improvement (from 16-25 GHz to 19-32 GHz) is achieved when the collector layer thickness is increased (from 250 to 350 nm, respectively). The bandwidth improvement for large photocurrent is at the origin of a ldquosupra-linearityrdquo effect. Photocurrent saturation effects are investigated and -1-dB compression current measurements at 20 GHz show saturation currents as high as 70 mA at -4 V. We also report third-order intermodulation distortion measurements at 20 GHz. The ldquosupra-linearityrdquo effect enhances the PD linearity with increased photocurrent, leading to a record third-order intercept point of 35 dBm at 40 mA.

Fabrication of low loss two-dimensional InP photonic crystals by inductively coupled plasma etching

A device concept for laterally extracting selected wavelengths from an optical signal traveling along a waveguide, for operation in metropolitan area networks, is presented. The signal on the fundamental mode of a multimode photonic crystal waveguide is coupled to a higher-order mode, at a center frequency that spatially depends on the slowly varying guide parameters. The device is compact, intrinsically fault tolerant, and can split any desired fraction of the signal for monitoring purpose. Characterizations by the internal light source technique validate the optical concept whereas an integrated device with four photodiodes qualifies its potential with respect to real-world applications.

High-Power High-Linearity Uni-Traveling-Carrier Photodiodes for Analog Photonic Links

We have developed a high-performance uni-traveling-carrier (UTC) and a modified uni-traveling-carrier (MUTC) photodiode (PD). We report a comparison between the two devices comprising both a 1.5- μm-thick absorption layer followed by a 0.5-μm-thick transparent collector layer. Both devices showed simultaneously a high responsivity (larger than 0.92 A/W at 1.55 μm), a high saturation current (larger than 100 mA at 10 GHz), and a high linearity (OIP3 of 35 dBm at 10 GHz). Thanks to a partly depleted absorber, the MUTC-PD is demonstrated to achieve a higher bandwidth (more than 20 GHz at high current), while the UTC-PD is demonstrated to achieve a higher saturation current and a less voltage dependent radio-frequency and linearity characteristics.

Compact wavelength monitoring by lateral outcoupling in wedged photonic crystal multimode waveguides

The authors report the growth of 6-, 9-, and 12-layer InAs∕InP quantum-dash-in-a-well (DWELL) laser structures using gas source molecular beam epitaxy. Broad area laser performance has been investigated as a function of number of layers. The highest modal gain at 48cm−1 is achieved for an optimized nine-DWELL layer structure. The effect of layer stacking and p-type doping on the characteristic temperature is also reported. Nine-DWELL layer single mode ridge waveguide lasers showed high slope efficiency (0.2W∕A per facet) and output power (Pout=20mW), close to those of conventional quantum well devices.

High Responsivity and High Power UTC and MUTC GaInAs-InP Photodiodes

We report on comb generation at 1.55 mum using a mode-locked quantum-dash-based laser. A flat optical spectrum with a ~10-nm width consisting of eight 100-GHz-spaced channels is demonstrated. Separate error-free transmission of each channel is achieved at 10 Gb/s over 50-km-long single-mode fiber. Compared to an ideal external cavity continuous-wave laser, a penalty of only 1.5 dB is measured for each filtered channel. This is attributed to the higher relative intensity noise level of a filtered mode.

Effect of layer stacking and p-type doping on the performance of InAs∕InP quantum-dash-in-a-well lasers emitting at 1.55μm

This letter demonstrates a planar junction GalnAs-AlInAs avalanche photodiode using back-side illumination through thinned InP substrate covered with chemical vapor deposition SiNx antireflection coating. The combined properties of very low dark current (I dark(M = 0) = 17 nA), low excess noise factor (f(M = 10) = 3.5), and high gain x bandwidth product over 140 GHz were simultaneously achieved with a high primary responsivity of 0.95 A/W at 1.55 mum.

Separate Error-Free Transmission of Eight Channels at 10 Gb/s Using Comb Generation in a Quantum-Dash-Based Mode-Locked Laser

We report two uni-traveling-carrier photodiode (PD) structures, for high-power and high-linearity applications. Using a thick collection layer (500 nm), the fabricated 25-m-diameter PDs achieve a 3-dB bandwidth up to 29 GHz, and a maximum dissipated heat power of about 480 mW, simultaneously. A new collector design with a nonuniform doping profile is proposed to better relax the space charge effect. Its performances are compared to a uniformly doped collector layer. Saturation currents and third-order intermodulation distortion measurements at 20 GHz confirm the advantage of the new collector design for high-power and high-linearity performances: 1-dB saturation current as high as 120 mA and a third-order intercept point in excess of 35 dBm at 70 mA are recorded.