An InGaAs-cap-monitor photodiode is monolithically integrated with a 1. 55 mu m InGaAsP/InP lambda /4-shifted DFB laser that has a higher output design. The optical coupling between the laser and the monitor is calculated using a Gaussian beam approximation, which shows that 20-40 percent of the rear light output can be monitored. The actual ratio of monitor current to front output at a temperature of 10-40 degree C is typically 0. 1-0. 2 mA/mW. It is shown that the integrated cap-monitor can be used, not only for the control of the laser power, but also for probing the threshold current and the single-wavelength property of an individual laser in a wafer, without cleaving out into chips. For the laser part with an antireflecting coating on the front facet, the maximum output power of 30 mW at 25 degree C and the highest CW temperature (as high as 100 degree C in p-side-up bonding) were obtained.
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