Beck Mason

Widely tunable sampled grating DBR laser with integrated electroabsorption modulator

We report on the development of the first widely tunable semiconductor laser with an integrated electroabsorption modulator. The laser is a four-section buried-ridge sampled-grating distributed Bragg reflector design. It has a 41-nm continuous tuning range with a maximum tuning current of 23.5 mA for the hack mirror and 21 mA for the front mirror. The modulator is based on a 0.87-eV bandgap bulk waveguide structure. It is capable of producing more than 22 dB of optical extinction over the entire tuning range of the laser with a -4.0-V bias.

Design of sampled grating DBR lasers with integrated semiconductor optical amplifiers

High output powers and wide range quasicontinuous tuning have been achieved in a sampled-grating distributed Bragg reflector laser with an integrated semiconductor-optical-amplifier. Using an amplifier with a curved passive output waveguide to suppress back reflection, we have achieved a quasicontinuous tuning range of over 50 nm and peak output powers greater than +8 dBm. Optimizing the device structure and the sampled-grating mirror design has enabled tuning ranges of up to 72 nm in devices without amplifiers.

Directly modulated sampled grating DBR lasers for long-haul WDM communication systems

The limitations on high-speed data transmission, using widely tunable sampled-grating distributed Bragg reflector (SGDBR) lasers, are investigated. We demonstrate 1.244-Gb/s data transmission over a wavelength range of 45 nm using a single directly modulated tunable SGDBR laser diode. Data transmission was evaluated on four separate wavelength channels each spaced 15 nm apart. Less than 0.6 dB of dispersion penalty was measured on all four channels for transmission over 50 km of standard single-mode optical fiber.

Tunable sampled-grating DBR lasers with integrated wavelength monitors

We report on the design and development of a wavelength monitor for use with tunable semiconductor lasers. The device is based on two-mode interference in an asymmetrically excited waveguide that is coupled to a Y-branch splitter. The monitoring range of the device is 30 nm. The wavelength monitor is capable of operating over an input power range of 34 dB, and the waveguide detectors do not saturate at photocurrents as high as 1.2 mA. The sensitivity of the monitor is only 1.24 nm for an isolated device, but improves to 0.44 nm when it is integrated on chip with the laser.

Ridge waveguide sampled grating DBR lasers with 22-nm quasi-continuous tuning range

We demonstrate a ridge waveguide sampled-grating distributed-feedback laser with continuous wavelength coverage over a 22-nm tuning range, the largest ever reported for a ridge waveguide structure. The design is based on a 400-nm-thick 1.4-/spl mu/m bandgap waveguide optimized for carrier injection tuning with offset quantum wells used to form the active region. The offset quantum wells enabled the device to be fabricated with only a single metal-organic chemical vapor deposition regrowth step. By tuning both mirror sections and the phase control section we were able to obtain 27 wavelength-division-multiplexed channels spaced at 100 GHz and precisely centered on the ITU grid with equal output power and greater than 40 dB of sidemode suppression ratio.

Compact, 4 x 4 InGaAsP-InP optical crossconnect with a scaleable architecture

An InP-InGaAsP 4/spl times/4 optical crossconnect occupying only 2/spl times/2 mm/sup 2/ was demonstrated by combining 16 1/spl times/2 optically amplified suppressed interference switches (OASIS) in a square array architecture. On/off ratios of 33/spl plusmn/4 dB were measured by a majority of these elements and fiber-to-fiber insertion loss of 3 dB was obtained using additional on-chip amplification stages.

Improved compositional uniformity of InGaAsP grown by MOCVD through modification of the susceptor temperature profile

The uniformity of InGaAsP layers is becoming increasingly important for optoelectronic devices. We present the results of an investigation where the susceptor temperature profile of a horizontal MOCVD reactor with substrate rotation is modified to achieve enhanced uniformity. Radial variations in room temperature photoluminescence (RTPL) peak wavelength were reduced from over 15 nm variation from center to edge (1 in. radius) to less than 6 nm variation using this technique. Similar improvements of lattice-mismatch (LMM) deviation were also observed. InGaAsP layers with band-gap wavelengths of both 1.1 μm (1.1 Q) and 1.4 μm (1.4 Q) were used to study the effect of the required As/P ratio on the temperature compensation technique. The results displayed that although the more difficult to control 1.1 Q responded more readily to the temperature profile modification, excellent uniformity (<6 nm variation) was achieved for both compositions. Combined RTPL and X-ray diffraction (XRD) measurements, used to evaluate the uniformity improvements of Group III and V sublattices separately, showed that the homogeneity of not only the As solid mole fraction (y), but the Ga solid mole fraction (x) benefited as well from the modified temperature profile. Accompanying the experimental observations, current theory on MOCVD growth of InGaAsP is applied to a state-of-the-art reactor to explain the source of the nonuniformities observed, their sensitivity to the reactor environment, and how their magnitude was reduced using the proper temperature profile.

Widely tunable lasers for wavelength-division multiplexed communications

Recently developed very wide tuning range semiconductor lasers have potential for use as sources in wavelength-division multiplexing (WDM) communications systems. The low-chirp and high-bandwidth modulation capabilities of sampled grating distributed Bragg reflector (DBR) lasers make them well suited for this application. SGDBR lasers have been fabricated with 62-nm cw tuning ranges, 5-MHz linewidths, and >40 dB mode suppression ratios. In this paper, we investigate the data transmission characteristics of directly modulated SGDBR lasers. The bit error rates were measured for both back-to-back and 50-km transmission on four separate wavelengths.

Characteristics of sampled grating DBR lasers with integrated semiconductor optical amplifiers

A state-of-the-art demonstration of photonic integration with results illustrating integrated widely-tunable lasers capable of high output power (>8 dBm), wide tuning ranges (50-70 nm), and modulation (2.488 Gb/s) is presented.

Optical crossbar switches on InP

Increasingly, optical cross connects are being proposed as the basis for various photonic packet switching nodes. Combining optical switches with semiconductor optical amplifiers (SOA) has been shown to be a very effective method in creating a more scaleable cross connect which can have lower loss and crosstalk than a simple gate array. Building upon this concept, we demonstrate a very compact 4/spl times/4 (2/spl times/2 mm/sup 2/) monolithic optical cross connect using sixteen 1/spl times/2 optically amplified suppressed interference switches (OASIS) While good crosstalk suppression performance (>35 dB) was achieved, practical devices will require a reduction of the insertion loss. Two efforts devoted to this goal, namely, the addition of a spot-size convertor and a waveguide tuning mirror were demonstrated to good effect.