John O’Brien

Two-dimensional photonic crystal Mach–Zehnder interferometers

Mach-Zehnder interferometers were fabricated from suspended membrane photonic crystal waveguides. Transmission spectra were measured and device operation was shown to be in agreement with theoretical predictions.

Operation of photonic crystal membrane lasers above room temperature

Operation of photonic crystal lasers for substrate temperatures as high as 50 °C is reported. The temperature dependence of the lasing wavelength and the threshold pump power is also investigated. The characteristic temperature To is 37.7 K.

High-quality-factor photonic crystal heterostructure laser

A high-quality-factor (Q) photonic crystal heterostructure laser was designed and characterized. Good agreement was obtained between the experimental lasing data and three-dimensional finite-difference time-domain numerical predictions.

Quality factors in single-defect photonic-crystal lasers with asymmetric cladding layers

We present quality factors of single-defect photonic-crystal resonant cavities with asymmetric cladding layers. The resonators studied here are dielectric slabs patterned with two-dimensional photonic crystals on a sapphire substrate. Three-dimensional finite-element and finite-difference time-domain routines were used to analyze the electromagnetic properties of these cavities. We observe that high quality factors (∼800) can be obtained in these cavities for reasonable structures with thick enough dielectric slabs. This work was motivated by the need to place photonic-crystal resonators on a substrate to improve heat dissipation in photonic-crystal lasers.

Nanofabrication of photonic crystal membrane lasers

We present techniques for fabricating photonic crystal (PC) membrane defect lasers. These nanostructures operate as optically pumped lasers under pulsed conditions at room temperature. The thin membrane PC defect structures are formed by transferring an electron-beam lithographically defined lattice pattern into an epitaxial layer structure by a sequential process of ion beam etching, reactive ion etching, and electron cyclotron resonance etching steps. A V-shape undercut channel is formed by a wet chemical etching using a 4:1 mixture of HCl and H2O to create the suspended membrane. We include a detailed description of a dependable and repeatable HCl undercut process for the PC structure.

Threshold dependence on the spectral alignment between the quantum-well gain peak and the cavity resonance in InGaAsP photonic crystal lasers

Lithographically defined multiwavelength photonic crystal laser arrays are reported. The dependence of the threshold pump power on the spectral alignment between the quantum-well gain peak and the cavity resonance wavelength is investigated. This is done at, and slightly above, room temperature.

Optical phase characterization of active semiconductor microdisk resonators in transmission

The optical phase characteristics of an indium phosphide (InP) vertically coupled microdisk were experimentally demonstrated. Overcoming the material losses by injecting current into the active quantum well microdisk layer has allowed us to observe the phase behavior in all three coupling regimes. The ability to tune the resonant wavelength of this device makes it suitable for use as a phase modulator or tunable optical delay element.

120μW peak output power from edge-emitting photonic crystal double-heterostructure nanocavity lasers

As an attempt to collect more in-plane emission power out of wavelength size two-dimensional photonic crystal defect lasers, edge-emitting photonic crystal double-heterostructure quantum well membrane lasers were fabricated by shortening the number of cladding periods on one side. 120μW peak output power was collected from the facet of the single mode laser at room temperature. Laser efficiencies were analyzed and agree very well with three-dimensional finite-difference time-domain modeling.

Double-heterostructure photonic crystal lasers with lower thresholds and higher slope efficiencies obtained by quantum well intermixing

In order to reduce the optical absorption loss, an array of double-heterostructure photonic crystal microcavity lasers was fabricated in which much of the photonic crystal mirror region was disordered by quantum well intermixing. In characterizing these devices, we obtained more than a factor of two increase in slope efficiencies and more than 20% reduction in threshold pump powers compared to devices that were not intermixed.

Room temperature InGaSb quantum well microcylinder lasers at 2μm grown monolithically on a silicon substrate

Room-temperature photopumped lasing operation near 2.0mum is reported from III-Sb microcylinders grown monolithically on silicon. High quality epitaxy is enabled by an interfacial misfit array. Growth, fabrication and device characterization is discussed