Short haul applications at 1310 nm require modulated sources with low cost, high performance and small footprint. Our activities target the performance aspects of direct modulation design. We demonstrate a fully packaged laser diode able to deliver a data throughput of 20 Gb/s with 6 dB of extinction ratio under a 3 V peak-to-peak modulation.
The surface temperature distribution of a GaAs wafer, heated under vacuum, has been measured using a
digital camera. A method is proposed to remove parasitic signals from the image. The accuracy of the thermal
image is validated by comparing the results with a separate measurement from absorption band-edge spectroscopy
(ABES). The thermal imaging data are observed to be within the experimental error from the ABES technique
for the entire surface of the wafer. We observe a radial temperature profile with a center-to-edge difference that
varies as a function of the central temperature. A difference of 25 °C is observed for a central temperature of
565 °C. This difference increases with the wafer temperature, confirming that it is due to a net heat flux escaping
the wafer by its edge, which is in contact with a graphite holder. Based on these results, a solution is proposed
in which the graphite wafer holder is replaced by a ceramic version.
Directly modulated lasers (DMLs) have two high performance applications: 1310 nm 10 Gb/s uncooled and 1550 2.5 Gs/s extended reach. Two key elements are gain coupled gratings and buried heterostructures. Gain coupled gratings simultaneously increase the DML's intrinsic relaxation oscillation frequency and damping, while the buried heterostructure reduces thermal chirp and parasitic capacitance. Large relaxation oscillation frequencies and reduced parasitic capacitance allow 85°C operation; large damping and reduced thermal chirp enable extended reach.
A low cost and high performance 4-(lambda) WDM DFB laser array employing a new strong gain-coupling laser design and a novel compact package approach is developed for optical network application. The WDM4 laser array is capable of simultaneous operation with 2.5 Gb/s 100 km NDS fiber transmission.