Single Microcavity Research Articles

Characteristics of a photonic bandgap single defect microcavity electroluminescent device

A microcavity surface-emitting coherent electroluminescent device operating at room temperature under pulsed current injection is described. The microcavity is formed by a single defect in the center of a 2-D photonic crystal consisting of a GaAs-based heterostructure. The gain region consists of two 70-/spl Aring/ compressively strained In/sub 0.15/Ga/sub 0.85/As quantum wells, which exhibit a spontaneous emission peak at 940 nm. The maximum measured output power from a single device is 14.4 /spl mu/W. The near-field image of the output resembles the calculated TE mode distribution in a single defect microcavity. The measured far-field pattern indicates the predicted directionality of a microcavity light source. The light-current characteristics of the device exhibit a gradual turn-on, or a soft threshold, typical of single- or few-mode microcavity devices. Analysis of the characteristics with the carrier and photon rate equations yields a spontaneous emission factor /spl beta//spl ap/0.06.

Optical Properties and Lasing in (In, Al)GaN Structures

We achieved low-threshold ultra-violet lasing in optically pumped GaN/AlGaN separate confinement heterostructures over a wide temperature range. Lasing modes of a single microcavity were examined from 20 to 300 K and gain mechanisms were compared to those of a thick GaN epilayer. We have also systematically studied InGaN/(In)GaN multiple quantum wells as a function of well and barrier thickness. We demonstrate that the stimulated emission threshold and photoluminescence (PL) decay time are strongly dependent on the well and barrier thickness. The experimental results indicate that the enhanced optical quality of samples with larger barrier thicknesses can he readily applied to the fabrication of InGaN/(In)GaN laser diodes.

Light emission from porous silicon single and multiple cavities

Experimental and theoretical techniques are used to examine the effects of microstructuring on the optical properties of multilayer, single and multiple microcavity structures fabricated from porous silicon. Measurements of the reflectivity and photoluminescence spectra of three multilayer samples are presented. The results are modelled using a transfer matrix technique including a negative absorption term to represent the effect of spontaneous emission which gives luminescence. The emitted light is strongly controlled by the optical modes of the structures and very good agreement is observed between theory and experiment.

GaAs microcavity quantum-well laser with enhanced coupling of spontaneous emission to the lasing mode

We have observed low-threshold lasing in a GaAs single quantum-well vertical microcavity. At 4 K the quantum-well emission linewidth is reduced, and the coupling efficiency β of the spontaneous emission to the lasing mode is improved. The laser threshold pump power obtained for a 200 Å GaAs quantum well pumped by a continuous wave Ti:sapphire laser was 5 mW, corresponding to 85 μW absorbed power. We have compared the experimental results with the theoretical prediction, and estimated the value of β to be 10−2.

Temperature-tunable, single frequency microcavity lasers fabricated from flux-grown YCeAG:Nd

Data are presented on a single-frequency, diode-pumped, microcavity YCeAG:Nd laser. The maximum output power was 45 mW in continuous operation, limited by the available pump power of 250 mW. The output was single-frequency, TEM00 at all powers. The lasing frequency was continuously temperature-tunable over a range greater than 180 GHz, with a stability of better than 10 MHz.

Enhanced and inhibited spontaneous emission of free excitons in GaAs quantum wells in a microcavity

Spontaneous emission of the free excitons in GaAs quantum wells in a microcavity is enhanced (x 130) or inhibited (x 1 30 ) by placing excitonic dipoles at either a resonant wavelength and anti-node position or an off-resonant wavelength and node position of the standing-wave vacuum field fluctuations. The resulting spontaneous radiation pattern is highly concentrated into the normal direction for the enhancement case and the spontaneous emission coupling efficiency into a single microcavity resonant mode is estimated to be 0.3. It is expected that semiconductor lasers with substantially reduced threshold currents can be constructed using such a structure.