Cavity-enhaced and quasi-phase-matched optical frequency doublers in surface-emitting geometry

We show that we can efficiently achieve surface-emitting second-harmonic generation in vertical and horizontal cavities. The fundamental beam is coupled into the waveguide, which consists of III–V or II–VI semiconductor multilayers or asymmetric quantum-well domain structures. The generated second-harmonic radiation propagates along the growth direction of these layers (which is normal to the propagation direction of the fundamental beam). The quasi-phase matching is achieved when second-order susceptibility is modulated along the growth direction in these structures. By the proper design of these structures, the frequency doublers based on these structures together can cover the spectrum of 0.8–2.0 μm. If the pump power density is sufficiently large, the conversion efficiency approaches saturation. The saturation power per unit waveguide width is between ~0.9 and ~435 mW/μm. At such a power density, 72% conversion efficiency can be achieved. In addition, the proposed frequency doublers are, in principle, broadband.