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The authors use high-resolution charge-coupled device based thermoreflectance to derive two dimensional facet temperature maps of a =1.55 m InGaAsP/InP watt-class laser that has a large 55 m2 fundamental optical mode. Recognizing that temperature rise in the laser will lead to refractive index increase, they use the measured temperature profiles as an input to a finite-element mode solver, predicting bias-dependent spatial mode behavior that agrees well with experimental observations. These results demonstrate the general usefulness of high-resolution thermal imaging for studying spatial mode dynamics in photonic devices. © 2006 American Institute of Physics. DOI: 10.1063/1.2388884 In semiconductor lasers, key parameters such as thresh-old current, efficiency, and wavelength are closely related to temperature. These dependencies are especially important for high-power lasers, in which device heating is the main cause of decreased performance and failure. Heat sources such as nonradiative recombination in the active region typically cause the temperature to be highly peaked within the device

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We demonstrate a high-power on-chip 1550-nm laser implemented by passive flip-chip integration of a curved-channel, double-pass InGaAsP/InP slab-coupled optical waveguide amplifier (SCOWA) onto a photonic integrated circuit (PIC) containing a silicon nitride (SiN) waveguide and distributed Bragg reflector (DBR) grating. The combined chip-scale SCOW external cavity laser (SCOWECL) has single mode emission with 312 mW of optical power at a drive current of 2.5 A, and exhibits a side mode suppression ratio (SMSR) of 55 dB, peak photon conversion efficiency (PCE) of 10%, low relative-intensity noise (RIN) of ∼160 dB/Hz, and an integrated linewidth of 192 kHz. Additionally, we demonstrate a multi-wavelength SCOWECL array comprised of four SCOWAs coupled to SiN-waveguide DBR gratings. The four-element array generates 80 mW per channel when the SCOWAs are driven in parallel (1.25 A/channel) with ∼1-nm wavelength spacing centered at 1533 nm. We describe the fabrication and hybrid integration processes. The measured SCOWA-to-waveguide coupling loss is estimated to be 1.6 +/−1.0 dB which agrees well with the simulation.