Mark E. Heimbuch

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.

Tertiarybutylarsine and tertiarybutylphosphine for the MOCVD growth of low threshold 1.55 mm In x Ga 1−x As/InP quantum-well lasers

Tertiarybutylarsine (TBA) and teriarybutylphosphine (TBP) are liquid organometallic sources that are a safer alternative to arsine and phosphine. In this work, we have grown high-quality In0.53Ga0.47As/InP quantum wells at a temperature of 590° with TBA and TBP partial pressures of 0.4 and 2.5 Torr, respectively. A low-temperature photoluminescence study indicated optimized column V growth interruption times of 0.5 s for In0.53Ga0.47As wells with InP barriers. Using the optimized growth conditions, we have obtained lattice matched In0.53Ga0.47As/InxGa1-xAsyP1-x single quantum-well lasers emitting at 1.55 μm. Broad-area devices with a length of 3.5 mm exhibit a low threshold current density of 220A/cm2. Broad-area lasers containing four quantum wells had a threshold current density of 300A/cm2 for a 3.0 mm cavity length and CW powers of 40 mW per facet for an as-cleaved 4 × 750 μm device.

Integration of semiconductor laser amplifiers with sampled grating tunable lasers for WDM applications

A semiconductor laser amplifier is integrated with a sample grating distributed Bragg reflector (SGDBR) laser to act as an external modulator. The fabrication, characterization, and device characteristics of this integrated tunable transmitter are reported. The integrated tunable laser can have up to 75 nm of tuning range and more than 30 dB of side-mode suppression ratio (SMSR). The integrated amplifier can provide at most 8 dB of gain and more than 25 dB of contrast ratio for all the channels. Its RF modulation bandwidth can achieve 1.5 GHz, and the dynamic chirp is as good as a directly modulated laser. A simple model is proposed to explain the measured modulation responses and gain saturation is found to be the main cause of the resonant peaks in the dynamics.

K-band operation of asymmetric Fabry-Perot modulators

The authors report preliminary high-frequency, small-signal optical measurements of asymmetric multiple-quantum well (MQW) Fabry-Perot electrooptic modulators which indicate that the electrical bandwidth for these devices is about 15 GHz at the onset of saturation, and as high as 21 GHz at low optical intensity-higher than any other measurements published to date. The modulators, 30 mu m*30 mu m in size, are integrated with on-chip microwave probe pads. The authors detail the fabrication process developed to achieve these high operating frequencies and predict from device models the maximum RC-limited operating frequencies for these devices.<<ETX>>

Reduced temperature sensitivity of the wavelength of a diode laser in a stress‐engineered hydrostatic package

By using the effects of increasing hydrostatic pressure to counteract the effects of rising temperature, we demonstrate a technique to stabilize the wavelength of an uncooled diode laser. We use the differential thermal expansion between various materials incorporated into the laser package to automatically generate a temperature‐dependent pressure, and obtain a 50% reduction in the temperature sensitivity of the wavelength of a 1.55 μm GaInAsP/InP laser.

Strained GaInAsP single‐quantum‐well lasers grown with tertiarybutylarsine and tertiarybutylphosphine

We report on low threshold current densities in GaInAsP single‐quantum‐well (SQW) lasers grown with the metalorganic column‐V precursors, tertiarybutylarsine and tertiarybutylphosphine, instead of the conventional compressed gas sources, arsine and phosphine. Threshold current densities of 121 A/cm2 for a 1.6% compressive strained SQW laser and 249 A/cm2 for an unstrained SQW laser have been measured and are among the lowest values seen in this material system.

Dynamic responses of widely tunable sampled grating DBR lasers

The modulation bandwidth, dynamic mode suppression ratio, and wavelength chirp of directly modulated sampled grating DBR lasers have been measured. Although the tuning range can be up to an order of magnitude larger than in simple DBR lasers, the chirp is about the same or better over a wide range of operation parameters. The modulation bandwidth was in excess of 4 GHz and the dynamic MSR remained larger than 40 dB as long as the current did not swing below threshold. The linewidth enhancement factor was extracted from the measured chirp parameters and ranged from three to eight for different lasing wavelengths of the tunable lasers. The dispersion of the linewidth enhancement factor is consistent with published theoretical predictions.

Continuous-wave operation of sampled grating tunable lasers with 10 mwatt output power, >60 nm tuning, and monotonic tuning characteristics

We describe recent results in widely tunable sampled grating lasers grown with tertiarybutylphosphine (TBP) and tertiarybutylarsine (TBA) column V sources. These devices exhibit 62 nm CW tuning range, 30-50 dB MSR, 10 mW output power, and monotonic tuning.<<ETX>>

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.

InP-based multiple quantum well structures grown with tertiarybutylarsine (TBA) and tertiarybutylphosphine (TBP): effects of growth interruptions on structural and optical properties

In this paper, we investigate the effect of interfacial layers on GalnAs(P)/GalnAsP and GalnAs/InP multiple quantum well structures with x-ray diffraction and photoluminescence. We observe a decrease in the room temperature and low temperature photoluminescence intensity as the number of periods is increased which we attribute to the interfaces. Furthermore, different growth interruption schemes show that decomposed As species from TBA have an effect on the structural and optical quality of these structures at both the lower and upper interfaces due to As carry-over. The effect of this carry-over is shown in structural measurements and laser diode results.