A II-VI compound semiconductor laser diode (10) is formed from overlaying layers of material including an n-type single crystal semiconductor substrate (12), adjacent n-type and p-type guiding lasers (14) and (16) of II-VI semiconductor forming a pn junction, a quantum well active layer (18) of II-VI semiconductor between the guiding layers (14) and (16), first electrode (32) opposite the substrate (12) from the n-type guiding layer (14), and a second electrode (30) opposite the p-type guiding layer (16) from the quantum well layer (18) Electrode layer (30) is characterized by a Fermi energy A p-type ohmic contact layer (26) is doped, with shallow acceptors having a shallow acceptor energy, to a net acceptor concentration of at least 1 x 1017 cm-3, and includes sufficient deep energy states between the shallow acceptor energy and the electrode layer Fermi energy to enable cascade tunneling by charge carriers

Blue-green laser diode

The combination of decreasing feature sizes and increasing chip sizes is leading to a communication crisis in the area of VLSI circuits and systems. It is anticipated that the speeds of MOS circuits will soon be limited by interconnection delays, rather than gate delays. This paper investigates the possibility of applying optical and electrooptical technologies to such interconnection problems. The origins of the communication crisis are discussed. Those aspects of electrooptic technology that are applicable to the generation, routing, and detection of light at the level of chips and boards are reviewed. Algorithmic implications of interconnections are discussed, with emphasis on the definition of a hierarchy of interconnection problems from the signal-processing area having an increasing level of complexity. One potential application of optical interconnections is to the problem of clock distribution, for which a single signal must be routed to many parts of a chip or board. More complex is the problem of supplying data interconnections via optical technology. Areas in need of future research are identified.

Optical interconnections for VLSI systems

Gain and threshold current density are analyzed for quantum-box lasers where electrons are confined in quantum well three-dimensionally, based on the density-matrix theory of semiconductor lasers with relaxation broadening. The electronic dipole moment and its polarization dependence are first analyzed, and it is shown that the gain becomes maximum when the electric field of light is parallel to the longest side of the quantum box. Calculated gain is about 10 times that of bulk crystal for 100 A × 100 A × 100 A GaAs/Ga 0.8 Al 0.2 As quantum box, and 15 times for Ga 0.47 In 0.53 As/InP quantum box with the same size, respectively. The threshold current density are 45 A/cm2and 62 A/cm2for GRINSCH GaAs/(Ga 0.8 Al 0.2 As-Ga 0.4 Al 0.6 As) and Ga 0.47 In 0.53 As/(Ga 0.28 In 0.72 As 0.6 P 0.4 -InP), respectively, where for the GaInAs/ GaInAsP/InP system the intervalence band absorption and nonradiative recombinations have been assumed to be the same as those obtained for bulk crystals experimentally. These results show the possibility of remarkable reduction in the laser threshold by the quantum-box structures.

Gain and the threshold of three-dimensional quantum-box lasers

Diffraction characteristics of general dielectric planar (slab) gratings and surface-relief (corrugated) gratings are reviewed. Applications to laser-beam deflection, guidance, modulation, coupling, filtering, wavefront reconstruction, and distributed feedback in the fields of acoustooptics, integrated optics, holography, and spectral analysis are discussed. An exact formulation of the grating diffraction problem without approximations (rigorous coupled-wave theory developed by the authors) is presented. The method of solution is in terms of state variables and this is presented in detail. Then, using a series of fundamental assumptions, this rigorous theory is shown to reduce to the various existing approximate theories in the appropriate limits. The effects of these fundamental assumptions in the approximate theories are quantified and discussed.

Analysis and applications of optical diffraction by gratings

Beam combining of laser arrays with high efficiency and good beam quality for power and radiance (brightness) scaling is a long-standing problem in laser technology. Recently, significant progress has been made using wavelength (spectral) techniques and coherent (phased array) techniques, which has led to the demonstration of beam combining of a large semiconductor diode laser array (100 array elements) with near-diffraction-limited output (M/sup 2//spl sim/1.3) at significant power (35 W). This paper provides an overview of progress in beam combining and highlights some of the tradeoffs among beam-combining techniques.

Laser beam combining for high-power, high-radiance sources

Impurity‐free selective layer disordering, utilizing Si3N4 masking stripes and SiO2 defect (vacancy) sources, is used to realize room‐temperature continuous AlxGa1−xAs‐GaAs quantum well heterostructure lasers.

Stripe‐geometry quantum well heterostructure AlxGa1−xAs‐GaAs lasers defined by defect diffusion

A phase-locked multiple-quantum-well (GaAl)As injection laser with a highly reflective rear facet coating and a low reflective front facet coating is reported to emit 2.6 W CW at room temperature from the front facet.

Phase-locked (GaAl)As laser diode emitting 2.6 W CW from a single mirror

Data are presented showing that the Al‐Ga interdiffusion coefficient (DAl‐Ga) for an AlxGa1−xAs‐GaAs quantum‐well heterostructure, or a superlattice, is highly dependent upon the crystal encapsulation conditions. The activation energy for Al‐Ga interdiffusion, and thus layer disordering, is smaller for dielectric‐encapsulated samples (∼3.5 eV) than for the case of capless annealing (∼4.7 eV). The interdiffusion coefficient for Si3N4‐capped samples is almost an order of magnitude smaller than for the case of either capless or SiO2‐capped samples (800≤T≤875 °C). Besides the major influence of the type of encapsulant, the encapsulation geometry (stripes or capped stripes) is shown, because of strain effects, to be a major source of anisotropic Al‐Ga interdiffusion.

Effects of dielectric encapsulation and As overpressure on Al‐Ga interdiffusion in AlxGa1−x As‐GaAs quantum‐well heterostructures

Laser operation utilizing distributed feedback (DFB) in single heterojunction (SH) GaAs/GaAlAs diodes is reported. Laser wavelengths ranging from 8430 to 8560 A were observed in various samples depending on grating period. The threshold current densities required were comparable to those of normal SH diodes.

Distributed‐feedback single heterojunction GaAs diode laser

Experimental and analytic studies of coupled multiple stripe (CMS) phase-locked, room-temperature diode lasers are reported. Such devices generate high-power well-collimated beams, which potentially may be electronically scanned in the manner of phased array radar. For the tested devices with ten conducting 3 μm stripe contacts on centers separated by D and coupled by curved waveguide sections, data from four stripe geometries with D ranging from 10 μm to 27.4 μm are compared and overall optimal characteristics occur for D = 10 \mu m. In that case, threshold current densities are comparable to solid area lasers, differential quantum efficiency is approximately 60 percent, and maximum observed pulsed power per facet is on the order of 1 W.

Robert D. Burnham

Papers

Stripe‐geometry quantum well heterostructure AlxGa1−xAs‐GaAs lasers defined by defect diffusion

Phase-locked (GaAl)As laser diode emitting 2.6 W CW from a single mirror

Effects of dielectric encapsulation and As overpressure on Al‐Ga interdiffusion in AlxGa1−x As‐GaAs quantum‐well heterostructures

Distributed‐feedback single heterojunction GaAs diode laser

Experimental and analytic studies of coupled multiple stripe diode lasers