*Widely Tunable Quantum-Well Laser: OPO Diode Around 2 μm Based on a Coupled Waveguide… DOI: http://dx.doi.org/ 10.5772/intechopen.80517*

high reflectivities at signal/idler wavelengths and low reflectivities at the pump wavelength, as present, for example, in [6]. Furthermore, stability of the device is improved by in situ control of the phase mismatch, through shift of the pump wavelength or of the OPO cavity temperature. These two factors can be tuned independently if the laser and OPO temperatures are set separately. This is possible if the two areas are separated by at least 100 μm and are controlled by individual heaters.

Thermal behavior and contact geometry are also expected to be critical. III/V on Si laser typically emits powers in the 10 mW range [11], while the pump power for OPO threshold is a few tens of mW in our case. The laser should be single mode for stable OPO operation, which imposes a maximal ridge width and thus a minimum optical power density. Furthermore, high-power single-mode lasers are usually shallowly etched (for single-mode operation) and mounted epi-down to limit thermal resistance [12]. In our case, these two aspects cannot be implemented at the same time. Indeed, if the laser is grown on top, the insulating section between laser and doped substrate makes it necessary to use lateral contacts, which requires deep lateral etching and compromises laterally monomode operation. On the opposite, if the laser is grown under the nonlinear (NL) waveguide, shallow etches are possible but epi-down mounting is impossible.

We also carefully examine fabrication tolerances in the region of parametric conversion and assess their impact on conversion efficiency.
