P.I. Kuindersma

High-performance 1.5 mu m wavelength InGaAs-InGaAsP strained quantum well lasers and amplifiers

Improved performance of 1.5- mu m wavelength lasers and laser amplifiers using strained In/sub x/Ga/sub 1-x/As-InGaAsP quantum well devices is reported. The device structures fabricated to study the effects of strained quantum wells on their performance are described. These devices showed TM mode gain, demonstrating the strain-induced heavy-hole-light hole reversal in the valence band. Lasers using these tensile strained quantum wells show higher and narrower gain spectra and laser amplifiers have a higher differential gain compared to compressively strained quantum well devices. Consequently, the tensile strained quantum well lasers show the smallest linewidth enhancement factor alpha =1.5 (compression alpha =2.5) and the lowest K-factor of 0.22 ns (compression K=0.58 ns), resulting in an estimated intrinsic 3 dB modulation bandwidth of 40 GHz (compression 15 GHz). >

Yield and device characteristics of DFB lasers: statistics and novel coating design in theory and experiment

Uncoated 1.55- mu m InGaAsP distributed-feedback (DFB) lasers show superior properties e.g. smaller linewidth and lower feedback sensitivity, in comparison to devices with low reflective facet(s). However, the phases of both front and rear mirror reflectivities, with respect to the grating, must be within sharp tolerances to get a stable dynamic single longitudinal mode device. These sharp tolerances lead to rather poor yield figures. A type of coating that allows the change of effective mirror phase by an arbitrary angle while preserving the superior high facet reflectivity is presented. To know what coating is optimum when applied to the batchwise process, a thorough statistical investigation in lasing behavior as a function of random facet phases, kL product, and front facet reflectivity is needed. Theoretical predictions of these quantities are presented, and also more general validity. The predictions on optimum phase rotation and the influence of absolute reflectivity values are verified experimentally and are found to very accurate. >

Low-pressure MOVPE growth and characterization of strained-layer InGaAs-InGaAsP

Abstract High-quality strained-layer InxGa1-xAs-InP quantum well structures, as revealed by photoluminescence and transmission electron microscopy studies, were grown by low-pressure metalorganic vapour phase epitaxy (MOVPE). Laser diodes at 1.5 μm wavelength employing compressively as well as tensile strained InxGa1-xAs-InGaAsP quantum wells with better performance than the much more extensively studied bulk InGaAsP and unstrained quantum well lasers are demonstrated. Threshold current densities as low as 92 and 147 A/cm2 were measured from tensile and compressively strained single quantum well lasers. For both signs of the strain, 0.8 mA threshold current operation is achieved of all-MOVPE grown semi-insulating planar buried heterostructure (SIPBH) lasers. These data represent, to the best of our knowledge, the lowest values reported so far for 1.5 μm wavelength lasers grown by any technique. Compressively strained multiple quantum well (MQW) lasers are found to excel in high power operation, as demonstrated by the record CW output power of 325 mW, resulting from improved threshold current, temperature sensitivity of the threshold current and external differential efficiency. The tensile strained MQW lasers show very high differential and total gain, resulting in very high operating temperature up to 140°C. Three-section distributed feedback lasers employing a compressively strained InGaAs MQW active region showed very large wavelength tuning ranges as high as 7.2 nm with a minimum linewidth as low as 700 kHz.

Wavelength-independent output power from an injection-tunable DBR laser

Injection-tunable three-section distributed Bragg reflector lasers emitting near 1.55 /spl mu/m have been fabricated employing bulk 1.48-/spl mu/m-bandgap InGaAsP in the tuning layer of the phase and Bragg sections. The gain in this material compensates for the increased absorption loss during tuning, which results in a nearly wavelength-independent optical output power. The maximum obtained output power is 28 mW ex facet, with a spectral linewidth around 5 MHz.<<ETX>>

High-output-power (+15 dBm) unidirectional 1310-nm multiple-quantum-well booster amplifier module

A unidirectional multiple-quantum-well booster amplifier module for the 1310-nm transmission window with a high 3-dB gain saturation output power of 18 dBm and a fiber-to-fiber gain of 17 dB is demonstrated. The module is equipped with a polarization-maintaining input fiber and optical isolators have been included. The booster amplifier was tested with a 1310-nm DFB laser directly modulated at 10 Gb/s, showing that 14.6 dBm of average fiber-launched output power could be obtained at 1 dB BER penalty, and that power budgets of 26.8 dB and 39.4 dB could be realized for a PIN photodiode receiver and an optically preamplified receiver, respectively, making repeaterless 10 Gb/s transmission over 70 to 100 km of standard single-mode optical fiber at 1310 nm a practical option.

High quality InGaAsPInP for multiple quantum well laser diodes grown by low-pressure OMVPE

Abstract InGaAsP/InP and InGaAs/InGaAsP multiple quantum well (QW) structures were grown by LP-OMVPE. Atomically flat interfaces were demonstrated by growing on (001) InP substrates with different (0.2° and 2°) misorientation. Multiple line photoluminescence (PL) emission at 2 K is observed for the first time from thin QWs which were grown on 0.2° misoriented (001) InP substrates. Corresponding QWs grown on 2° misoriented substrates showed single line PL emission. The multiple line spectra are ascribed to thickness variations within one QW with lateral sizes larger than the excitonic radius. In InGaAsP/InP QWs half-monolayer and in InGaAs/InGaAsP QWS monolayer well width variations were obtained from the analysis of the PL spectra. The studies well thicknesses ranged from 90 A down to ≈ 4 A for InGaAsP, with maximum spectral upshifts of 514 meV. The very high quality of the QWs is also indicated by FWHM linewidths of 8.8 meV for a ≈ 6 A well of InGaAsP and 12.5 meV for a ≈ 10 S well of InGaAs. Two populated subbands were observed for the first time in the two-dimensional electron gas at InP-InGaAsP heterojunctions; a mobility of 80000 cm 2 /V·s was measured at 30 mK. DCPBH multiple quantum well lasers consisting of 12 InGaAsP wells and 11 InP barriers with threshold currents of 20 mA at an emission wavelength of 1.5 μm were fabricated.

DFB lasers with integrated electroabsorption modulator

We present high-performance 1550 nm DFB lasers with butt-coupled, bulk type integrated electroabsorption modulators of good manufacturability and reliability. Key issues in device design are reviewed and the strong influence of the exact detuning between lasing wavelength and modulator bandgap is demonstrated. Fibre-coupled output powers as large as 6 dBm and attenuation efficiencies as high as 12 dB V−1 are obtained. Butterfly-packaged devices show only 1 dB penalty for 10 Gbit s−1 NRZ transmission over 50-km standard single-mode fibre (SMF) without the use of an optical amplifier. With an optical booster amplifier, self-phase-modulation in the fibre is exploited and repeaterless 10 Gbit s−1 transmission is possible over 150-km standard SMF.

114 km, repeaterless, 10 Gbit/s transmission at 1310 nm using an RZ data format

There is an increasing interest in 1310-nm optical amplification as more than 50 million km of standard single-mode fiber (SSMF) has been installed worldwide. Consistent developments in the field of 1310-nm optical amplification have resulted in high-gain (>30 dB) polarization-insensitive semiconductor optical amplifiers (SOAs) for optical pre-amplification and high saturation output power (14 dBm) SOA boosters. These devices were implemented in a repeaterless transmission system. Here a DFB laser diode operating at 1310 nm was gain switched at 10 GHz to produce return-to-zero (RZ) pulses of 30 ps at FWHM that were subsequently de-chirped and compressed to 18 ps at FWHM using 4.4 km of dispersion-shifted fiber. After boosting the 10-GHz pulse train up to 10 dBm, the pulse train was modulated with a 10 Gbit/s, 2/sup 31/-1 pseudorandom bit sequence by the LiNbO/sub 3/ electro-optic modulator with an extinction ratio of 15 dB. Finally, the signal is boosted up to 12 dBm and launched into 114 km of SSMF (zero dispersion at 1309 nm) with a total attenuation of 42.9 dB. The signal at the output of the second booster did not show any pattern effects. A 400-mA bias current was applied to each of the two boosters. The boosters exhibited a fiber-to-fiber gain of 13.6 dB and 15.4 dB and a 3-dB saturation output power of 16 dBm and 13 dBm, respectively.

Universality of the chirp-parameter of bulk active electro absorption modulators

The universal behavior of chirp-parameter, modulation efficiency, output power and photocurrent of bulk active electro absorption modulators is experimentally and theoretically demonstrated the voltage over the EAM is scaled with an EAM threshold field.

Fabrication and spectral characteristics of a 1.55‐μm distributed feedback laser with a tunable integrated external cavity

The fabrication and lasing characteristics of a 1.5‐μm distributed feedback laser with a butt‐coupled tunable integrated resonator are described. An additional modulation of the distributed feedback laser spectrum introduced by the external cavity is clearly demonstrated. Optical bistability has been observed in the power versus tuning current characteristic. The device has a limited continuous tuning range of 4.2 A. Tuning current change allows for the selection of compound cavity mode and one of the distributed feedback laser modes, while maintaining single‐mode operation. Linewidth reduction due to the integrated cavity is clearly demonstrated, and linewidths <10 MHz have been obtained.