Photonic Crystal QCLs
Analytical coupled-wave model for photonic crystal surface-emitting quantum cascade lasers
An analytical coupled-wave model is developed for surface-emitting photonic-crystal quantum cascade lasers (PhC-QCLs). This model provides an accurate and efficient analysis of full three-dimensional device structure with large-area cavity size. Various laser properties of interest including the band structure, mode frequency, cavity loss, mode intensity profile, and far field pattern (FFP), as well as their dependence on PhC structures and cavity size, are investigated. Comparison with numerical simulations confirms the accuracy and validity of our model. The calculated FFP and polarization profile well explain the previously reported experimental results. In particular, we reveal the possibility of switching the lasing modes and generating single-lobed FFP by properly tuning PhC structures.
See external page Opt. Express. 25, 11997 (2017) for more details.
Room temperature surface emission on large-area photonic crystal QCLs
We design and fabricate large-area (1.1mm × 1.1mm) photonic crystal quantum cascade lasers, enabling single-mode (wavelength ~ 8.5 μm) surface emission at room temperature, with a maximum peak power up to 176 mW. The beam divergence is <1° and with no side-lobes. Moreover, by introducing asymmetry into the photonic crystal pillar shape, a single-lobed far-field pattern is realized. The photonic band structure is measured with high spectral (0.72cm-1 ) and angular (0.1°) resolution by using the photonic crystal quantum cascade laser itself as a detector.
See external page Appl. Phys. Lett. 114, 031102 (2019) for more details.
High power (5W in peak) photonic crystal QCL
Room temperature surface emission is realized on a large area (1.5 mm × 1.5 mm) photonic crystal quantum cascade laser (PhC-QCL) driven under pulsed mode, at the wavelength around 8.75 µm. By introducing in-plane asymmetry to the pillar shape and optimizing the current injection with a grid-like window contact, the maximum peak power of the PhC-QCL is up to 5 W. The surface emitting beam has a crossing shape with 10° divergence.
See external page Opt. Express 27, 22708-22716 (2019) for more details.
Topological charge of finite-size photonic crystal modes
Topological charges are the winding numbers of polarization vectors around the vortex centers of far-field radiation. In this work, the topological charge of photonic crystal modes is theoretically analyzed using an envelope function approach. A group of modes is discovered with unique polarization properties dictated by their nontrivial envelope functions. Experimentally, lasing operation on such a mode is demonstrated in an electrically pumped mid-infrared photonic crystal surface-emitting laser with high slope efficiency. The topological charge is directly observed from the polarization properties of single-mode laser emission. Furthermore, it is shown that envelope functions may bring a new possibility to control the polarization profiles of photonic crystal lasers.
See external page Phys. Rev. B 102, 045122 (2020) for more details.
