K. H. Gulden

Highly uniform vertical-cavity surface-emitting lasers integrated with microlens arrays

In this paper, work is described on the fabrication of highly uniform 8/spl times/8 arrays of GaAs-AlGaAs vertical-cavity surface-emitting lasers (VCSELs). Oxide-confined VCSEL arrays show an average threshold current of 0.74/spl plusmn/0.02 mA, an average output power of 2.05/spl plusmn/0.03 mW at 8 mA and an average power conversion efficiency of 14.3%. Their wavelength is measured to be 967/spl plusmn/0.35 nm over the array. In addition, we describe the alignment and integration of these device arrays with arrays of refractive microlenses to allow beam shaping typically required in system applications.

Continuous-wave dual-wavelength lasing in a two-section vertical-cavity laser

A vertical-cavity surface-emitting laser with two monolithically grown cavities is presented. The three-terminal device allows current injection into the active regions of both cavities. Under various injection conditions, the device lases continuous wave on either one of the two longitudinal modes supported by the cavity, or on both wavelengths simultaneously. By using a constant injection current in the bottom cavity, and adjusting the current in the top cavity, the device shows all four possible emission states. These are the off states, lasing at the short wavelength /spl lambda//sub S/, at the long wavelength /spl lambda//sub L/, and at both /spl lambda//sub S/ and /spl lambda//sub L/ at the same time.

Thermal lensing effects in small oxide confined vertical-cavity surface-emitting lasers

The thickness and position of an oxide layer inside a vertical-cavity surface-emitting laser structure have been optimized for minimum optical scattering loss. In the resulting structure, the index guiding provided by the oxide aperture is very small. Consequently, for an oxide aperture radius <2 μm, the optical mode is only weakly confined. In devices using such small apertures, the formation of a thermal lens has a strong influence on optical guiding. The thermal lens leads to lower threshold currents and increased differential efficiency with continuous wave as compared to pulsed injection operation in devices with small apertures.

Narrow-linewidth vertical-cavity surface-emitting lasers for oxygen detection.

The use of vertical-cavity surface-emitting lasers (VCSELs) for optical detection of atmospheric oxygen is described. The VCSELs were custom designed for single-mode emission in the 763-nm wavelength range, with low noise and narrow optical linewidth. Using standard wavelength modulation spectroscopy and a second-harmonic detection scheme with a 1-m air path, we determined an oxygen concentration resolution of 0.2%. Because of its small size, low power dissipation, and good tunability characteristics, the VCSEL promises to be an attractive light source for use in compact, low-cost optical sensor microsystems for trace gas detection.

Design and construction of an optoelectronic crossbar switch containing a terabit per second free-space optical interconnect

The completed detailed design and initial phases of construction of an optoelectronic crossbar demonstrator are presented. The experimental system uses hybrid very large scale integrated optoelectronics technology whereby InGaAs-based detectors and modulators are flip-chip bonded onto silicon integrated circuits. The system aims to demonstrate a 1-Tb/s aggregate data input/output to a single chip by means of free-space optics.

MODE BEHAVIOR AND HIGH RESOLUTION SPECTRA OF CIRCULARLY-SYMMETRIC GAAS-ALGAAS AIR-POST VERTICAL CAVITY SURFACE EMITTING LASERS

The mode behavior of symmetric air‐post vertical cavity surface emitting lasers is investigated using a unique tandem triple‐pass Fabry–Perot interferometer as well as standard characterization techniques. A series of high resolution spectra taken at various current levels demonstrates relaxation oscillations of the fundamental mode and the lifting of mode degeneracy by crystal birefringence and structural anisotropy. Near field images and L–I measurements identify the discontinuous jumps in mode number and polarization.

Electro-optic birefringence in semiconductor vertical-cavity lasers

Birefringence induced by the electro-optic effect is demonstrated in vertical-cavity surface-emitting lasers (VCSEL). This is done by comparing two types of optically pumped VCSELs: VCSELs with standard pin-doping and VCSELs with symmetrical pip-doping. The observed birefringence in these VCSELs differs by an order of magnitude, a difference that we ascribe to the presence and absence, respectively, of electro-optic birefringence.

Polarization effect in light emitting diodes with ordered GaInP active layers

We report on polarization effects in surface emitting light emitting diodes based on p‐i‐n AlGaInP/GaInP double heterostructures grown by metal organic vapor phase epitaxy. Devices with an ordered GaInP active layer show polarized light output with a ratio of 4:3 for polarization along the [011] and [011] crystal direction, respectively. This polarization is nearly independent of diode current and mesa geometry, but is not observed if disordered GaInP active layers are used. The effect is considered to be an important means for polarization control in vertical cavity surface emitting lasers.

Polarization anisotropy in the electroabsorption of ordered GaInP

The polarization dependence of the Franz–Keldysh effect (FKE) in metalorganic vapor phase epitaxially grown AlGaInP/GaInP/AlGaInP p-i-n double heterostructures was investigated for samples with different ordering parameters. We determine an ordering induced shift of the FK spectra of up to 13 meV between light polarized along the [011] and [01-1] crystal directions. Due to the FKE the transmitted light intensity ratio between the respective polarizations was changed from 0.2 to 2.8 dB by applying an electric field of 335 kV/cm.

Novel shadow mask molecular beam epitaxial regrowth technique for selective doping

We present a novel molecular beam epitaxial regrowth technique which provides a simple and convenient way for the in situ lateral structuring of the doping profiles and growth rates on a μm scale. We achieve excellent selective contacts to the respective doping layers for device dimensions varying from several 100 μm down to several μm. Keldysh based n‐i‐p‐i modulator structures, fabricated with our new method, exhibit an on/off ratio of 6:1 for a voltage swing of 7 V without enhancement by additional Bragg mirrors.