Alfonso R. Alija

Coupled-cavity two-dimensional photonic crystal waveguide ring laser

Coupled-cavity hexagonal ringlike photonic crystal lasers are fabricated as a class of single mode photonic crystal laser light sources. The structures are formed by placing one missing hole nanocavity (H1 type) between each two segments at 60° that form the hexagonal ringlike photonic crystal laser. The H1 cavities act as a mode filter, clamping the frequency of emission of the laser device. The emission frequency in these rings with cavities varies as the filling factor is changed, allowing the tuning of the laser emission. Stable single mode lasing occurs with side mode suppression greater than 20dB. This kind of devices may be used as an efficient selective filter of modes and may have important applications in future photonic devices for optical communications and optical sensing.

Theoretical and experimental study of the Suzuki-phase photonic crystal lattice by angle-resolved photoluminescence spectroscopy

A complete theoretical and experimental analysis of the photonic band structure for the Suzuki-phase lattice is presented. The band diagrams were calculated by two-dimensional plane wave expansion and three-dimensional guided-mode expansion methods. Angle resolved photoluminescence spectroscopy has been used to measure the emission of the photonic crystal structure realized in active InAsP/InP slabs. Photonic bands with a very low group velocity along an entire direction of the reciprocal lattice have been measured, which may have important applications on future photonic devices. The experimentally determined dispersion is in very good agreement with the calculated photonic bands. The presence of defect modes produced by microcavities in the Suzuki-phase lattice has also been established.

Tuning of spontaneous emission of two-dimensional photonic crystal microcavities by accurate control of slab thickness

We have found a blueshift in the cavity modes confined in two-dimensional photonic crystal microcavities when the thickness of the slab was varied uniformly by accurate dry etching. The shifts in the wavelength of the cavity modes were around 2nm towards shorter wavelengths per nanometer reduced in the thickness of the slab. Three-dimensional plane wave expansion calculations showed that the observed shifts are inside the calculated photonic band gap of the structures. The variation in the energy position of the peaks with the thickness has been analyzed by three-dimensional finite difference time domain calculations for a one missing hole microcavity. This tuning of the emission wavelength with the change in the thickness slab shows the important effect of the third dimension in photonic crystals made out of semiconductor slabs and it can be of interest for its application in the final processed photonic devices like photonic crystal lasers.

Effect of implementation of a Bragg reflector in the photonic band structure of the Suzuki-phase photonic crystal lattice

We investigate the change of the photonic band structure of the Suzuki-phase photonic crystal lattice when the horizontal mirror symmetry is broken by an underlying Bragg reflector. The structure consists of an InP photonic crystal slab including four InAsP quantum wells, a SiO(2) bonding layer, and a bottom high index contrast Si/SiO(2) Bragg mirror deposited on a Si wafer. Angle- and polarization-resolved photoluminescence spectroscopy has been used for measuring the photonic band structure and for investigating the coupling to a polarized plane wave in the far field. A drastic change in the k-space photonic dispersion between the structure with and without Bragg reflector is measured. An important enhancement on the photoluminescence emission up to seven times has been obtained for a nearly flat photonic band, which is characteristic of the Suzuki-phase lattice.

High-speed 1.55 μm operation of low-temperature-grown GaAs-based resonant-cavity-enhanced p–i–n photodiodes

We report the design, growth, fabrication, and characterization of GaAs-based high-speed p–i–n photodiodes operating at 1.55 μm. A low-temperature-grown GaAs (LT-GaAs) layer was used as the absorption layer and the photoresponse was selectively enhanced at 1.55 μm using a resonant-cavity-detector structure. The bottom mirror of the resonant cavity was formed by a highly reflecting 15-pair GaAs/AlAs Bragg mirror. Molecular-beam epitaxy was used for wafer growth, where the active LT-GaAs layer was grown at a substrate temperature of 200 °C. The fabricated devices exhibited a resonance around 1548 nm. When compared to the efficiency of a conventional single-pass detector, an enhancement factor of 7.5 was achieved. Temporal pulse-response measurements were carried out at 1.55 μm. Fast pulse responses with 30 ps pulse-width and a corresponding 3 dB bandwidth of 11.2 GHz was measured.

Modal suppression and single-mode emission in photonic crystal coupled-cavity ring-like lasers

We have designed and fabricated a new class of photonic crystal ring-like laser structure with hexagonal shape on InGaAsP/InP semiconductor slabs by introducing nanocavities in the corners of the hexagonal ring. Different structures have been designed and fabricated by shifting the position of the nanocavity by one lattice parameter around the corners. Laser emission has been measured and characterized. The global effect of the introduction of an H1 cavity located in the six corners of a hexagonal waveguide ring-like resonator promotes a strong modal suppression compared to the ring structure without cavities. The introduction of the nanocavities reduces the many modes of the regular hexagonal ring-like structure, as finite element calculations show. Ring-like structures without cavities show multimode spectra while structures with cavities present strong mode reduction in the studied range. For a specific design of the structures with the cavities inside the hexagon area a clearly single mode emission is observed with a side mode suppression ratio higher than 20 dB.

New Technological Approaches for the Fabrication of Planar Photonic Crystals on III-V Compounds

Summary form only given: We have developed new technological approaches for the fabrication of planar photonic crystals on III-V compounds. We have used electron beam (e-beam) lithography in combination with reactive ion beam etching (RIBE) and reactive ion etching (RIE) and different reactive and non-reactive chemistries (Ar, CCl2F2 and Cl2) to fabricate two-dimensional photonic crystals (planar) on GaAs-based semiconductor compounds. Also, we have used e-beam lithography on flowable oxides and epitaxial regrowth by molecular beam epitaxy (MBE) to obtain a photonic crystal nanopattern. Finally, focused ion beam etching (FIB) has been used to successfully fabricate photonic crystal structures on III-V semiconductor heterostructures