James P. Wittke

Y2O3 : Yb : Er‐New Red‐Emitting Infrared‐Excited Phosphor

Y2O3 : Yb : Er and Gd2O3 : Yb : Er are efficient phosphors that emit red light when excited by the absorption of ir radiation. A number of processes are important in suppressing the green emission normally seen in erbium‐ytterbium double‐doped phosphors, and in emphasizing the often weak red emission. These processes are discussed in detail. An over‐all electrical‐to‐light power conversion efficiency of (3–5) × 10−4 was observed, from which an internal ir‐to‐visible conversion efficiency of 30–55% was inferred. It is concluded that, regardless of coupling efficiency, GaAs : Si ir generation efficiencies and inherently broad incoherent infrared diode emission spectra will limit over‐all efficiencies in diode‐excited phosphors to about 1%.

Effects of Elevated Temperatures on the Fluorescence and Optical Maser Action of Ruby

Measurements are made of the wavelengths, linewidths, and fluorescent efficiencies of the fluorescent R1 and R2 lines in ruby, in the temperature range 300° to 500°K. The results are used to explain the degradation of ruby optical maser performance at elevated temperatures.

Rare-earth-doped oxysulfides for GaAs-pumped luminescent devices

There has been much recent interest in phosphors that emit visible radiation when excited with infrared light from a semiconductor injection diode source. Various fluoride hosts-LaF3, YF3, and BaYF5—have been reported to give efficient green emission when doubledoped with ytterbium and erbium. We have found that rare-earth oxysulfides—La2O2S, Gd2O2S, and Y2O2S—are also efficient phosphors for this application when properly prepared. Green emission is obtained from phosphors doped with ytterbium and erbium, the green emission arising from erbium ions in the2H11/2 and4S3/2 excited states. The emission is accompanied by red emission from the lower4F9/2 states, but this is sufficiently weak that the apparent color of the emitted light is only slightly altered by the red emission. The green emission is in a group of lines near 5500Å, near the peak of the eye sensitivity. By using thulium doping instead of erbium, blue emission is obtained from the1G4 states of thulium. This is accompanied by red emission, also from the1G4 states. The comparative performance of La2O2S, Gd2O2S, and Y2O2S is presented.

Lateral mode selection in semiconductor injection lasers

Various methods have been used to control the lateral modes of injection lasers. We report on lateral mode selection in continuous‐wave double‐heterojunction lasers using the differential diffraction losses of different modes at a narrow reflector stripe on one emitting facet. Power output curves and far‐field beam patterns scanned in the lateral (junction) plane are shown both before and after an antireflection coating was deposited on one facet except in a narrow stripe. The stripe defines the mode‐selecting reflective region. Calculations, based on a simple model of DH injection lasers, are made by estimating the magnitude of the effect. Output powers of 12 mW from one facet were obtained.

Direct Observation of Longitudinal Modes in the Output of Optical Masers

Longitudinal modes in the output of pulsed U: CaF2 and ruby optical masers have been observed directly by means of a high resolution, high‐dispersion grating spectrometer. The mode spacings are in reasonable agreement with the expected values. The linewidth of the individual modes is instrument‐limited at about 0.05 cm−1. Maser action is observed to occur simultaneously in the various modes.

Properties of a blue-emitting IR pumped YF 3 :Yb, Tm diode

A practical blue-light-emitting diode using the IR pumped phosphor YF 3 :Yb, Tm is described. The emission spectrum of the coated GaAs:Si diode exhibits peaks at 4750, 6450, 7000, 8000, and 9500 A. Visually, the unfiltered emission appears blue with a purple cast due to the red 6450 A peak. A luminance as high as 60 fL in the blue has been achieved using reasonable current densities for the pump diode.