The thermal response of a tunable laser is analyzed by using a mode density method based on a Fourier-Laplace analysis. This method introduces a mode density function for mode distribution of the Fourier-Laplace transform and gives temperature time-dependency in an integral form instead of an infinite weighted summation. When symmetric structures are assumed, the mode density method gives the transient thermal response in a simple form: error functions (spherical-symmetry case) and exponential integral functions (cylindrical-symmetry case). The cylindrical-symmetry analysis was extended to the noncylindrical-symmetry model and the thermal response of the tunable laser was calculated by the mode density method. The result shows good agreement with a Fourier-Laplace analysis (deviation 2%) and experimental results. As a rough estimation, the thermal response of the laser is in proportion to the logarithm of time in some range that depends on the chip and tuning-section size of the laser.

We introduce the characteristics for continuous wave operation at room temperature of InGaN laser diodes fabricated on SiC substrates. The threshold current was 60 mA, the threshold voltage was 8.3 V, and the oscillation wavelength was 404.4 nm. The lifetime of the laser diodes with a constant light output of 1 mW at 25 was 57 hours. The heat dissipation of the devices mounted p-side-up on a stem without using a heat sink was shown to be as good as that of devices mounted p-side-down with an external heat sink, owing to the high thermal conductivity of SiC substrates.

Laser diodes in the (Al, Ga, In) N system are attractive for many applications. Due to the wurtzite crystal structure, cleaved facets are not easily produced. We have investigated distributed feedback (DFB) laser diodes employing embedded dielectric gratings with the grating located above the active region. The dielectric gratings are incorporated via epitaxial lateral overgrowth. The DFB laser diodes had reduced threshold current densities over the etched cavity devices, with a minimum of 15 kA/cm2. The spectral emission width was considerably reduced for the DFB devices. Voltages for the DFB devices were high due to the presence of the Si3N4 grating within the p-type material.

Continuous-wave operation at room-tempera-ture has been demonstrated for InGaN multi-quantum-well (MQW) laser diodes (LDs) grown on FIELO GaN substrates with a backside n-contact. This was made possible by introducing important new concept of reducing threading dislocations that occur during the growth of the GaN substrates. We found that InGaN active layers grown on FIELO GaN are superior to those grown on conventional sapphire substrates in terms of their growth mode and the resultant In compositional fluctuation. The fabricated laser diode shows the threshold current, the threshold current density and the threshold voltage were 36 mA, 5.4 kA/cm2 and 7.5 V, respectively, with the lasing wavelength of 412 nm and internal quantum efficiency as high as 98%.

This paper was written for LSI engineers in order to demonstrate the effect of optical interconnections in LSIs to improve both the speed and power performances of 0.5 and 0.2 µm CMOS microprocessors. The feasibilities and problems regarding new micronsize optoelectronic devices as well as associated electronics are discussed. Actual circuit structures clocks and bus lines used for optical interconnection are discussed. Newly designed optical interconnections and the speed power performances are compared with those of the original electrical interconnection systems.

The static characteristics of GaInAs(P)/GaInAsP quantum well laser diodes (QW LDs), with graded-index separate-confinement-heterostructure (GRIN-SCH) grown by metalorganic chemical vapor deposition (MOCVD), have been investigated experimentally in terms of threshold current density, internal waveguide loss, differential quantum efficiency and light output power. Very low threshold current density of 410 A/cm2, high characteristic temperature of 113 K, low internal waveguide loss of 5 cm-1, high differential quantum efficiency of 82% and high light output power of 100 mW were obtained in 1.3 µm GRIN-SCH multiple quantum well (MQW) LDs by optimizing the quantum well structure including confinement layer and cavity design. Excellent uniformity for the threshold current, quantum efficiency and emission wavelength was obtained in all MOCVD grown buried heterostructure GRIN-SCH MQW LDs. Lasing characteristics of 1.5 µm GRIN-SCH MQW LDs are also described.