A. Kock

Optimization of the emission characteristics of light emitting diodes by surface plasmons and surface waveguide modes

In this letter, the influence of metal films and dielectric waveguides on the radiation characteristics of light emitting diodes (LEDs) is investigated. Cross and hexagonal surface grating structures are used to excite surface plasmons and waveguide modes in these media. A beam divergence as small as 17° is achieved for a hexagonal grating coated with a 40 nm Ag film. The maximum quantum efficiency is found for a hexagonal grating with a 10-nm-thick Au film and a 250-nm-thick dielectric layer. The optical power emitted by this LED into the solid angle from −30° to 30° is 10% higher than that of an LED without metal film and dielectric layer.

Novel surface emitting GaAs/AlGaAs laser diodes based on surface mode emission

We present a novel concept to achieve surface emission from conventional semiconductor laser diodes. This new type of laser diode is modified to allow a coupling of the laser mode to a transverse electric polarized surface mode. As a result we achieve surface emission from GaAs/AlGaAs double heterostructure laser diodes with a beam divergence of 0.2%. This novel concept has a high potential for the realization of a beam steering device.

Frequency tuning of a double‐heterojunction AlGaAs/GaAs‐vertical‐cavity surface‐emitting laser by a serial integrated in‐cavity modulator diode

The frequency tuning of a vertical‐cavity surface‐emitting laser through current injection is reported herein. This was achieved by integrating an AlGaAs graded‐index p–n‐modulator diode with a double‐hetero GaAs/AlGaAs laser diode in a vertical cavity formed by an AlAs/AlGaAs‐Bragg reflector and a metallic mirror. Experimental results show an obtained gradient of frequency shift up to 0.93 GHz/mA by the modulator current. This effect is at present restricted to approximately 40 mA due to thermal effects. A theoretical model based on the plasma effect and thermal effects agrees with the experimental values and predicts a maximum value for the gradient of frequency shift of 1.15 GHz/mA with the presented structure.

Single-mode and single-beam surface emission from visible red GaInP/AlGaInP laser diodes

Single-mode and single-beam surface emission (675–680 nm) has been achieved from visible red GaInP/AlGaInP laser diodes by applying the surface mode emission technique. The laser diodes emit a single beam via the surface with a beam divergence of 0.16° and show single-mode emission both in ac as well as in dc operation with a minimum spectral linewidth of 0.07 nm. The highest sidemode suppression achieved at present in ac operation is 19 dB.

Adjustable surface emission from AlGaAs/GaAs laser diodes based on first‐order‐grating coupled surface mode emission

Strongly improved surface emitting laser diodes based on surface mode emission are presented. A first‐order‐grating was utilized for the excitation of the surface modes. This results in an efficient quasi‐single‐beam surface emission with low divergence and a significant narrowing in the emission spectrum. A variation in the emission wavelength of up to 4 nm is achieved by adjusting the surface waveguide thickness, which demonstrates the wavelength selection mechanism of the SME technique. The decisive advantage of the SME laser diodes in comparison to DFB/DBR laser diodes is their high flexibility in fabrication, which makes them very suitable for wavelength division multiplexing applications.

Single‐mode and single‐beam emission from surface emitting laser diodes based on surface‐mode emission

Single‐mode and single‐beam emission have been achieved from surface emitting laser diodes based on the surface‐mode‐emission technique. By employing an optimized device design and a first‐order grating coupler, the laser diodes show under pulsed operation condition a single‐mode emission with a linewidth of 0.11 nm. A power up to 3.6 mW is emitted into a single, surface‐emitted beam, which has a beam divergence of 0.20°.

Surface mode coupling in GaAs/AlGaAs laser diodes—A novel concept for a single laser mode emission

We demonstrate a novel concept for a mode selection mechanism in surface emitting laser diodes. This concept is based on a strong coupling process between the laser mode and a surface mode on top of the laser diode. The mode selection mechanism is the result of a strong feedback from the surface mode into the laser diode. Nearly single‐modelike emission spectra are achieved from surface emitting GaAs/AlGaAs laser diodes and qualitatively explained by a model based on ray optics. The main advantage of this type of laser diode is its simple fabrication and the possibility of adjusting the desired wavelength independent of the growth process by external technological parameters.

A novel surface emitting GaAs/AlGaAs laser diode beam steering device based on surface mode emission

We present a novel surface emitting laser diode beam steering device based on the excitation and emission of surface modes. This new device is a wavelength tunable GaAs/AlGaAs laser diode, which is modified to allow a coupling of the laser mode to a transverse electric polarized surface mode. A steering of the surface emitted farfield pattern is achieved by a variation of the emission wavelength. By electrically switching the emission wavelength from 877.54 run to 879.13 nm the dominant surface emitted peak is steered by 0.4°.

Surface emitting semiconductor laserdiodes based on surface mode emission

We present novel surface emitting semiconductor laserdiodes based on the excitation and emission of surface modes. By coupling the laser mode to a surface mode we achieve surface emission from conventional laserdiodes with extreme narrow beam divergence. In addition we demonstrate a steering of the beam emission angle by changing the wavelength of the laser light.

12-wavelength array of single-mode surface-emitting laser diodes based on surface mode emission

Fig. 2 the image of the spectrally resolved near field of the laser diode with an external cavity terminated by a conventional plane mirror. In this picture, the horizontal axis represents the wavelength (increasing from left to right) and the vertical axis represents the lateral axis (parallel to the junction) of the laser diode. In this configuration, the laser emits on several longitudinal modes, spaced by 0.2 nm. The highorder lateral modes begin to oscillate as soon as the output power exceeds 1 mW. These modes can be identified by their shorter wavelength and their multilobe intensity lateral distribution. From the picture, we could observe seven longitudinal modes; at least nine lateral modes can be distinguished for the longitudinal mode that is shown as magnified. When the external cavity is terminated by an apodizing grating, single longitudinal and single lateral mode operation has been observed over the full range of allowed injection currents as shown on Fig. 3. Our approach further allows tuning of the laser frequency by tilting the grating; that feature should lead to applications in the technology of single-mode tunable dye or solid-state lasers. 1. H. Zucker, Bell Syst. Tech. J. 49, 2349-2376 (1970). 2. G. Giuliani, Y. K. Park, R. L. Byer, Opt. Lett. 5,491-493 (1980). 3. N. McCarthy, P. Lavigne, Opt. Lett. 10,