Very Small Aperture Laser (VSAL) system is a near field optical data storage system that utilizes a nano-aperture fabricated at the front facet of a semiconductor laser to define a nano-sized spot and hence to achieve ultra-high density storage. However, these nano-apertures typically have very poor power throughput behavior when the sizes of the apertures are much smaller than the wavelength of the incident light. In this paper, we use numerical simulation tool XFDTD, which is a three-dimensional vector electro-magnetic field simulator based on the finite difference time domain (FDTD) method, to study the behavior of the nano-apertures. We show that for square apertures, the power throughput decays as r4 (r is the size of the aperture) when the aperture size r is less than lamda/4 (lamda is the incident light wavelength). To solve the power throughput shortage problem, we present our novel nano-aperture design -'C'-aperture. Compared with a conventional 100nm square aperture, the 'C'-aperture provides 1000x higher power throughput while maintaining a comparable near field spot size. We show that the greatly enhanced power throughput is due to both the polarization and resonance effects.
We report on our efforts to develop a laser printbar consisting of a very dense array of independently addressable laterally-oxidized top-emitting VCSELs. In order to maintain wafer planarity for easy electrical routing, the buried oxidation layer in our structure is accessed through small via holes instead of a more typical mesa etch. Unlike most VCSELs, our devices utilize transparent indium-tin- oxide top contacts that allow for a more compact device design. The 200-element array we fabricated has a linear density of one device every 3 micrometers .
We disclose a method of eliminating the polarization instability in laterally-oxidized vertical-cavity surface- emitting lasers. By employing an appropriately-shaped device aperture, we are able to make the lasers operate in a single polarization direction through their entire L-I curve.
We present a study on a novel method for the determination of the quality factor and the cavity loss in semiconductor lasers. The method we use involves Fourier analysis of the Fabry-Perot mode spectrum when operating the device below lasing threshold. The observation of the decay rate of higher order harmonics in the Fourier analysis of the spectra allows us to determine the amount of cavity propagation loss/gain. As an illustrative example, a Fourier analysis on experimental data for lasers fabricated in the AlGaAs material system will be given. In addition to the measurements on propagation loss/gain, this method allowed also the identification of the density and strength of intra-cavity scattering centers in optically pumped AlGaInN lasers. This is an important capability for the fabrication of blue diode lasers in the gallium-nitride material system.
We present the primary laser printing system performance issues which are the driving forces for multiple beam laser printing. Although edge emitting semiconductor lasers have allowed progress in this area, vertical cavity lasers have substantial advantage in the longer term. We further present needs and issues with VCSEL performance which must be addressed for the application of VCSELs to high performance laser printing. Finally, we explore advanced print architectures which would be enabled by the VCSEL device.
The longer-wavelength quantum well in an AlGaAs/GaAs asymmetric dual quantum well laser structure was selectively removed by localized intermixing. High Si-doping on each side of the longer-wavelength well caused intermixing during an anneal under a SiN<SUB>x</SUB> cap, while leaving the other nearby well intact. During an anneal under an exposed GaAs surface layer, both quantum wells remained intact. By patterning the surface with alternating SiN<SUB>x</SUB> and exposed GaAs, the longer-wavelength quantum well was selectively intermixed under the SiN<SUB>x</SUB>. Integrated broad area lasers were fabricated with threshold current density and external quantum efficiency of 260 A/cm<SUP>2</SUP> and 30%/facet at a wavelength of 751 nm in capped regions and 195 A/cm<SUP>2</SUP>, 32%/facet at 824 nm in the uncapped regions. This technique can be used to fabricate close spacing multi-wavelength laser arrays.
The discovery of the phenomenon of impurity induced layer disordering (IILD) has enabled novel device
geometries to be applied to the task of patterning heterostructure layers for the realization of high performance
optoelectronic devices. In this paper we will review progress in the various ways of implementing and controlling
the IILD process, and discuss several of the potentially important device concepts for optoelectronic integration
that are enabled by this technology.