Abstract
We report the experimental realization of deformed microcavity quantum cascade lasers (QCLs) with a Limaçon-shaped chaotic resonator. Directional light emission with a beam divergence of θ∥≈33° from QCLs emitting at λ≈10 μm was obtained in the plane of the cavity for deformations in the range 0.37<ε<0.43. An excellent agreement between measured and calculated far-field profiles was found. Both simulations and experiments show that the Limaçon-shaped microcavity preserves whispering gallery-like modes with high Q-factors for low deformations (ε<0.50). In addition, while the measured spectra show a transition from whispering gallery-like modes to a more complex mode structure at higher pumping currents, we observed ‘universal far-field behavior’ for different intracavity mode distributions in the Limaçon microcavity, which can be explained by the distribution of unstable manifolds in ray optics simulations. Furthermore, the performance of the deformed microcavity lasers is robust with respect to variations of the deformation near its optimum value ε=0.40, which implies that this structure reduces the requirements on photolithography fabrication. The successful realization of these microcavity lasers may lead to applications in optoelectronics.
Highlights
We report the experimental realization of deformed microcavity quantum cascade lasers (QCLs) with a Limaçon-shaped chaotic resonator
The deformed microcavity QCL was based on lattice matched Ga0.47In0.53As/Al0.48In0.52As heterostructures grown by molecular beam epitaxy (MBE) on top of an n-doped (3 × 1018 cm−3) InP substrate
The active region consists of 35 periodic stages, each consisting of a fourwell double-phonon active region structure [38], targeted for light emission around 10 μm and a superlattice injector that serves as an energy relaxation region for electrons exiting the previous stage
Summary
The deformed microcavity QCL was based on lattice matched Ga0.47In0.53As/Al0.48In0.52As heterostructures grown by molecular beam epitaxy (MBE) on top of an n-doped (3 × 1018 cm−3) InP substrate. A 0.5 μm-thick n-doped (5 × 1018 cm−3) InP layer was deposited on the top of the cladding layer, followed by a 10 nm highly n-doped (1 × 1019 cm−3) InP contact layer. The QCL material was processed into a Limaçon-shaped structure, which is defined by R(θ ) = R0(1 + ε cos θ ), where ε is the deformation factor and R0 is the radius of curvature when θ = π/2; see figure 1(a) for the optical microscope image of the top view of a device with R0 = 80 μm and ε = 0.40. A scanning electron microscope (SEM) image of the device sidewall (figure 1(b)) shows a roughness of about 300 nm, which gives minor scattering considering that the wavelength of the laser is in the mid-infrared range. For each size and deformation of the structure, several samples were cleaved and tested to allow a repeatable and meaningful statistical analysis
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
