A mode-adapted semiconductor optical amplifier (SOA) has been fabricated and packaged. At the gain peak, 1500 nm, the fiber to fiber gain was measured to be 32.5 dB. Statistics for eight packaged devices indicate that a fiber-to-fiber gain of 26.3 dB /spl plusmn/ 1.3 dB and a saturation output power of 12.4 dBm /spl plusmn/ 0.4 dBm are typical at a bias of 500 mA for /spl lambda/ = 1550 nm. Polarization sensitivity at 1550 nm was measured to be 1.1 dB /spl plusmn/ 0.4 dB and the transverse electric (TE) polarization state noise figure (NF) was determined to be 7.0 dB /spl plusmn/ 0.5 dB. The coupling loss was 1.3 dB /spl plusmn/ 0.1 dB per facet. This SOA, with a 1.3-nm filter, was used as an optical preamplifier in a 10-Gb/s return-to-zero (RZ) system testbed with a pseudorandom binary sequence (PRBS) of 2/sup 31/ -1. A 14.5-dB improvement in receiver sensitivity was observed at a bit error rate (BER) of 10/sup -11/.

Successful growth of 1.3 and 1.55 μm GaInAsP/InP multiquantum well lasers directly on a distributed feedback (DFB) grating substrate using all solid-source molecular beam epitaxy was demonstrated. A 1.12 μm wavelength GaInAsP planarization layer with a nominal thickness of 500–650 Å was first grown on the DFB gratings at an elevated temperature to create a smooth surface for subsequent layer growth. Transmission electron micrograph showed smooth interfaces after the growth of this GaInAsP planarization layer. Low threshold current density and high quantum efficiency were obtained from these index-coupled DFB lasers.

Summary form only given. In this paper, we report a new laser transmitter device that utilizes a simple, low-amplitude voltage dither signal to realize a high stimulated Brillouin scattering (SBS) threshold with low residual amplitude modulation (AM). This method relies on an intracavity phase modulator to dither the lasing wavelength, thereby broadening the optical spectrum with high uniformity. We demonstrate an SBS threshold of 25.0 dBm by applying a 100 kHz, 95 mV/sub pp/ triangle wave to the on-chip phase modulator. The resultant residual AM is only 1.2%. In addition, this laser transmitter may be tuned between four wavelength-division multiplexing (WDM) channels and permits data encoding without an external amplitude modulator.

This paper describes the fabrication techniques pertaining to the on-wafer lasing wavelength control of an electroabsorption modulated laser (EML) using both a direct approach and a tunable wavelength sources. The direct approach utilizes multiple grating pitches to control the on-wafer lasing wavelength of the DFB arrays. High resolution E-beam lithography was used to generate a phase mask to produce seven grating pitches separated by 0.25 nm pitch intervals. In a tunable wavelength sources approach, we used a multi-electrodes DFB lasers integrated with a bent waveguide for the wavelength tuning. These fabrication techniques show a promising low cost way of mass producing either sets of discrete DFB devices with different wavelengths or a more complicated integrated devices with wavelength combiner and a modulator.

Successful growth of GaInAsP/InP multi-quantum well lasers directly on a distributed feedback (DFB) grating substrate using all solid source molecular beam epitaxy (MBE) was demonstrated. A 500 /spl Aring/ thick 1.12 /spl mu/m wavelength GaInAsP planarization layer was first grown on the DFB gratings at an elevated temperature to create a smooth surface for subsequent layer growth. Transmission electron micrograph showed smooth interfaces after the growth of this GaInAsP planarization layer. Low threshold current density and high quantum efficiency were obtained from these index-coupled DFB lasers grown by solid source MBE.

Sub-micron periodic gratings with pitch ∼3,000Å were formed in GaN and InGaN using holographic lithography and room temperature ECR BCl 3 /N 2 dry etching at moderate microwave (500W) and rf (100W) powers. The process produces uniform gratings without the need for elevated sample temperatures during the etch step.

New enabling technologies are needed for optical communication systems to accommodate rapidly growing traffic demands. Wavelength conversion and high-speed optical packet switching/routing will be key technology components for realizing more flexible and efficient optical networks. Lasers capable of wide-band, high-speed wavelength tuning will be essential to support these advanced functions. Also, many applications will require high launch powers in order to access an increasing number of users, nodes, or base stations. Hence, laser transmitters capable of suppressing stimulated Brillouin scattering (SBS) would be highly desirable. We have developed an ultrafast, broadband tunable laser, based on an electroabsorption modulator laser (EML), which exhibits wavelength switching speeds as fast as 56 ps. Here, we report system performance results on wavelength conversion high-speed optical packet switching, and SBS suppression using this device. We have tested multiple wavelength conversion sequences and demonstrated penalty-free transmission through two cascaded wavelength conversion stages including 200 km of standard non-DS fiber. When used to perform packet switching at 2.5 Gb/s, the tunable laser allows switching between optical packets on 4 wavelength channels in less than 1 bit period, thereby requiring no significant guardband. The modulated data packets have been transmitted through 200 km of non-DSF and yield open eye diagrams. The tunable laser has also been used to perform SBS suppression. We have measured SBS thresholds of approximately 25 dBm on 4 separate WDM channels. The required modulation signal is very small, 95 mVpp, and the residual AM is only approximately 1%.

Distributed-feedback (DFB)-buried heterostructure lasers incorporating a substrate grating require epitaxy of waveguide layers over the corrugated grating surfaces. Unlike epitaxy an planar (100) substrate, the corrugated substrate surface contains undesirable crystal facets which lead to an uncontrollable variation in local composition during epitaxy, and thereby results in strong localized misfit Stresses. These localized misfit stresses further affect the subsequent growth of high quality layers which constitute the active device structures. To address the general issue of epitaxy on corrugated surface, a thermodynamic analysis is performed for surface mass transport on grating surface at normal growth temperature go show that grating wash-out is a thermodynamically favorable process. However, grow th on a perfectly preserved grating is undesirable due to the composition shift on groove facets. A systematic study of substrate orientation dependent composition variation of quaternary lavers indicates a composition shift generally toward In and P rich direction for orientations from (100)-(111). Conditions for a strain free waveguide layer growth are demonstrated. The commonly observed imperfections associated with grating overgrowth are summarized, and their effects on the device reliability are discussed.

Design and fabrication of the first 1.55-/spl mu/m wavelength tunable electroabsorption modulated laser integrated with a bent waveguide distributed-feedback (DFB) laser is reported. A low-threshold high-efficiency and stable single-longitudinal-mode operation is obtained when the electrodes of the bent DFB waveguide were uniformly pumped. In a normal configuration where the modulator part is used as an intensity modulator (i.e., AR coating on the modulator side and HR coating on the DFB side), stable single longitudinal mode output power close to 40 mW in free space is obtained with a 0-V bias to the modulator and an extinction ratio of up to 15 dB at 2.5 V. This single mode stability is due to the continuously distributed phase shift implemented in the structure thus reducing the photon pile-up inside the laser cavity as compared to an abruptly quarter-wave phase shifted DFB laser. With a nonuniform injection in the multiple electrodes, it was possible to select one particular single longitudinal mode out of the three neighboring modes inside the broad reflection band of the reflector. A wavelength tuning range of about 3.5 nm was obtained while maintaining an optical output power of more than 2 dBm from each mode. The device has a very low chirp (0.01-nm peak-to-peak) when modulated with a 2.5 Gb/s pseudorandom binary sequence (PRES) data stream and an error-free transmission over 200 km of non-DSF fiber has been demonstrated for all four wavelength channels separated by 100-GHz spacing. Also, when the modulator part of the structure is used as a phase tuning element (i.e., antireflective (AR) coating on the DFB side and HR coating on the modulator side), we have successfully demonstrated high-speed optical packet switching with a fast and wide tunable wavelength range. The optical packets can be modulated at 2.5 Gb/s and may be switched among four wavelength channels in less than one bit period.

The fabrication of the first 1.55-mu m wavelength tunable electroabsorption modulated laser integrated with a bent waveguide distributed-feedback laser is reported. A low-threshold and stable single-mode operation is obtained when the devices were uniformly pumped. A single-mode output power close to 10 mW from a single-mode fiber (40 mW in free space) Is obtained with a 0 V bias to the modulator and an extinction ratio of up to 15 dB at 2.5 V. This single mode stability is due to the continuously distributed phase shift implemented in the structure, With a nonuniform injection, it was possible to select one particular mode out of the three neighboring modes inside the broad-reflection band of the reflector, A tuning range of 3.5 nm was obtained while maintaining an output power of more than 2 dBm from each mode.

We demonstrate high-speed optical packet switching using a fast broadband-tunable laser. The optical packets are modulated at 2.5 Gb/s and may be switched among 4 wavelength channels in less than 1 bit period, thereby requiring no significant guardband. The data packets are transmitted through 200 km of non-DSF and yield open eye diagrams.

The explosive growth in internet, multimedia and wireless traffic in recent years is rapidly exhausting capacity in public networks worldwide, forcing network service providers to aggressively install new lines and upgrade old ones. Fortunately, technological breakthroughs in the areas of erbium-doped fiber amplifiers (EDFA's), passive wavelength demultiplexers and low chirp sources have made all-optical dense wavelength-division multiplexed (WDM) systems a cost-effective way to utilize the vast bandwidth already available in the embedded fiber plant. WDM systems offer additional operational advantages, including high ultimate capacity, bit-rate transparency, flexible growth strategies, and the potential to use all-optical wavelength routing in future broadband network architectures, Commercial WDM systems operating at the OC-48 (2.5 Gbit/s) line rate are now available, and OC-192 (10 Gbit/s) terminal equipment which is under development will further enhance the capacity of these systems.One of the keys to viable WDM systems is the availability of inexpensive low-chirp optical transmitters. By taking advantage of photonic integrated circuit technology, it is possible to produce monolithically integrated DFB laser/EA modulators (EML's) with low chirp, low drive voltage and high extinction ratio, in a single compact package, In this talk we will discuss the operating characteristics of these devices and their relationship to WDM system performance.

This paper describes the essential elements for creating a practical wide bandwidth directly modulated laser source. This includes considerations of the intrinsic limitations of the laser structure, due to the resonant frequency and damping of the laser output, together with carrier transport issues to allow carriers in the device active region to be efficiently modulated at high speeds. the use of a P-doped compressively strained multiple-quantum well active region to provide high intrinsic speed and remove transport limitations is described, together with record setting results of 25 GHz modulation bandwidth for a 1.55 micrometer Fabry-Perot laser and 26 GHz bandwidth for a 1.55 micrometer DFB laser. The challenges of providing high bandwidth electrical connections to the laser on a suitable submount, together with fiber attachment and microwave packaging, are discussed. Results of fully packaged 1.55 micrometer DFB lasers with 25 Ghz modulation bandwidth are shown. Digital modulation of the packaged 1.55 micrometer DFB including impedance matching is described, and the transient wavelength chirp is presented. This low chirp is reduced further using an optical filter, to provide a 10 GBit/s source with chirp similar to that of an external electroabsorption modulator.

We have transmitted 10 Gb/s data over 130 km standard fiber without any dispersion penalty in receiver sensitivity (for 10/sup -9/ BER) and with a 7% eye margin for 10/sup -15/ BER by operating an integrated EA/DFB laser with low extinction ratio (/spl epsi/=5 dB) and negative chirp (/spl Delta//spl nu/=-0.01 nm).

Summary form only given. Here we report the first penalty-free transmission results over 48 km of nondispersion-shifted fiber using a 1.3-/spl mu/m wavelength integrated electroabsorption modulated MQW laser (EML) device at a bit rate of 10 Gbit/s.

Summary form only given. In this paper we describe 1.55-/spl mu/m DFB lasers for communications applications using p-doped compressively strained multiple quantum well (MQW) active regions to provide devices with extremely high modulation bandwidths and low wavelength chirp.

The first monolithically integrated DFB laser/Mach-Zehnder interferometric modulator fabricated by the selective area low pressure MOVPE growth technique is reported. A near 3-dB power divider at the Y-branches of the interferometer has been reproducibly achieved by a photolithographically defined dielectric mask used in the selective area growth technology and confirmed by an infrared near field imaging technique. A modulation depth of over 12 dB was achieved both in the forward and reverse bias to the arms of the phase modulator.< >

We have demonstrated the first monolithic integration of a DFB laser with a Mach-Zehnder type modulator fabricated by the selective area MOVPE growth technique and operating at 1.55 μm. A spatially resolved micro photoluminescence setup was used to characterize the crystal quality. We have achieved a low loss and near 3 dB Y-branch power divider in the structure with the modulator achieving an attenuation up to 17 dB and a π phase shift voltage of 2 V