**Acknowledgements**

*Nonlinear Optics - Novel Results in Theory and Applications*

To limit its temperature rise, the laser should be at the least 2 mm long. This size is above the average for common sources in integrated optics, which often favor compactness. Large DFB grating lengths increase modal reflectivity, not only lowering threshold but also degrading differential efficiency. Furthermore, the laser mode is only partially confined before the taper, so we estimate the impact of

In order to achieve high optical powers and single-mode operation, we propose a DFB laser with low grating reflectivity and high reflectivity (HR) coating on the external facet. We assume that the DFB grating is etched at the interface between laser core and top cladding. To avoid regrowth, gratings can also be etched on the surface [16]. However, optimization of surface gratings depends on the top contact geometry, which has not been defined yet. Therefore, we present only the buried

If the laser is 1–2 mm long to limit temperature rise, an etch depth of 10–20 nm is necessary to provide a *κL* product of ∼0.5 (where κ is the coupling constant of the fundamental mode). This value is realistically achievable with a shallow etch and

For a laser of length 2 mm with a coating of reflectivity 90% on the external

tial efficiency is 0.38. The modal gain needed to reach laser oscillation is 19 cm<sup>−</sup><sup>1</sup> [17]. QW lasers at 980 nm commonly achieve modal gains in excess of this value [18]; however, the threshold is also affected by the confinement factor. For a single QW of thickness (10 nm), we find that the confinement of lasing mode

Assuming a recombination time of 3 ns, the threshold current density is then

We have defined the main conditions required for a diode-OPO structure based on a vertical coupler, and we have described the passive properties of this source. Phase matching can be dynamically controlled through wavelength and temperature tuning. We achieve transfer to a higher order mode of the structure, with sufficient efficiency. The taper layout can still be improved via further

Overall, this design predicts promising results for the fabrication of an integrated diode-OPO based on GaAs. Unlike all-in-one DOPO configurations, this

While fabrication of this device is complex, epitaxy regrowth can be avoided completely if the laser DFB grating can be defined at the surface. Most of the technological complexity occurs in the various etching levels necessary to define the

To ensure feasibility of this project, future work should focus on laser design,

particularly on expected optical power and impact of doping on the transfer.

device does not require record-low propagation losses in the laser diode.

structure, from tapers to DFB grating to DBRs.

In conclusion, we have shown that the key parameters (threshold and efficiency) of this laser are not affected by its unusual design and that they are compatible with

, comparable to the range of 120–150 A/cm<sup>2</sup>

and internal efficiency is 80%, external differen-

[17].

at thresh-

measured

in the well [19].

facet, assuming a κL product of 0.5, total output coupling losses are 9 cm<sup>−</sup><sup>1</sup>

in the well is 1.2%, which corresponds to a material gain of 1600 cm<sup>−</sup><sup>1</sup>

old. This is achieved under a carrier density of 2.5 × 1018 cm−<sup>3</sup>

**5.2 Key parameters**

grating case.

epitaxy regrowth.

If parasitic losses are 10 cm<sup>−</sup><sup>1</sup>

expected to be 130 A/cm<sup>2</sup>

in similar lasers [13, 18].

**6. Conclusion**

optimization.

operation in excess of 100 mW.

confinement on the modal gain.

**122**

This work is supported by a public grant overseen by the French National Research Agency (ANR) as part of the project DOPO. The authors thank the Commissariat à l'Energie Atomique and Direction Générale de l'Armement for the PhD funding. We thank Michel Krakowski and Bruno Gérard for their information and stimulating discussions.
