Electron beam pumping for high power deep-UV emitters

Abstract

High-power optical sources that emit in the UV spectral range have applications that include bio-chem identification, decontamination, medical diagnostic and treatment, communications, and materials curing. Attempts to realize semiconductor UV sources by the conventional approach with a current-injection p-/n-junction diode have encountered numerous difficulties. This presentation will discuss the challenges, illustrate the current status of materials/device development, and describe the necessary building blocks, which include highly conductive p-type cladding layers, sophisticated electron-blocking layers, and high performance active zones. High current densities of more than 20kA/cm2 of a full LD heterostructure have been achieved. Optically pumped lasers have been demonstrated with low pump threshold down to a wavelength of 237nm. However, issues related to effective carrier injection and low absorption losses remain challenging when using high band gap p-type materials. Thus, a laser configuration that omits the use of p-doped materials is an attractive alternative. We will present recent results towards realizing deep-UV lasers in the AlGaN materials system using electron beam excitation as the laser pumping strategy. A custom-built e-beam-pumping system has been developed that enables excitation of AlGaN gain chips with high-energy electrons (10-30keV) and high-power densities exceeding 1 MW/cm2. AlGaN gain chip heterostructures for vertical laser emission will be described. Toward development of a compact deep-UV laser source, we report record high pulsed peak optical output power of more than 200mW of spontaneous emission at ?=246nm.