Over the last several years, it has become widely recognized that electromagnetic interference (EMI), electromagnetic Pulse (EMP), High-Intensity Radio Frequency (HIRF), and new threats, such as directed-energy weapons, can jeopardize the flight safety of vehicles equipped with Fly-By-Wire (FBW) systems, unless adequate shielding precautions are taken. This leads to weight penalties which can be avoided through implementation of Fiber-optic systems.
InGaAs/GaAs strained-layer quantum well lasers have been successfully demonstrated for very high temperature CW operation up to 200 C. The lasers show promising reliability data at 70 C, 100 C, and 125 C and high output power of about 300 mW with a 3-micron ridge-waveguide structure.
The effect of high temperature on the threshold gain and threshold current density of an InGaAs (GaAs based) strained quantum well laser is examined both theoretically and experimentally. It is shown that designing a quantum well laser for low threshold gain through the use of a long laser cavity and/or high reflectivity facet coatings will reduce the temperature induced threshold current increase. This result is related to the nonlinear dependence of quantum well gain and current density on carrier density. The high temperature characteristics of strained InGaAs and GaAs QWs are also compared.
Predictions of the threshold current density of GaAs/AlGaAs graded refractive index (GRIN), separate confinement heterostructure (SCH), single potential well (SW) diode lasers at 25 degree(s)C and 125 degree(s)C using strict k-selection theory are made. A reasonable fit to the experimental data at both temperatures can be obtained without including carrier scattering. It is concluded that good predictions of threshold current density and differential quantum efficiency can be made provided one knows how to predict the temperature dependence of internal quantum efficiency.
This short article reviews the key technologies required for implementation of future Photonic and in particular FBL systems. These technologies include fiber— optic position sensors, multiplexers, fiber—optic data O-8194-0508-6/91/$4.OO SPIE Vol. 1418 Laser Diode TechnologyandApplications /11(1991) / 153 buses, and transceivers. Some of Boeing's work in these technologies is described briefly in this article, and is covered more completely in Reference 1.
InGaAs/GaAs strained-layer quantum well (SQW) laser structures have been investigated for avionic applications requiring high-temperature performance. These lasers offer availability of wavelengths in the range of 0.9-1.1 micrometers for important applications in Er-doped fiber amplifiers and optoelectronic integrated circuits. For the first time, InGaAs/GaAs SQW lasers capable of cw operation up to 200 degree(s)C have been successfully demonstrated. The lasers show threshold current density of 200 A/cm2, differential quantum efficiency of 60%, output power of approximately equals 1 W for 50-micrometers oxide-stripe and 120 mW for 3-micrometers ridge- waveguide lasers, and characteristic temperature (TO) of 130-140K. In this paper, the optimization of the stripe width, orientation and cavity length for the laser performance have been studied. The characteristics of these devices are described. Measured I-V, L-I, spectrum, farfield pattern and reliability data are presented.