Cr:ZnSe laser crystal grown by Bridgeman technique: characteristics and laser performance

Abstract

Cr:ZnSe crystals grown by the Bridgeman technique from the melt in inert gas (argon) under pressure were characterized and utilized as effective laser active material. Large crystalline boules with a necessary concentration of Cr²⁺ ions 10¹⁹ cm^-3, practically homogeneously distributed throughout the crystal bulk (50 mm in diameter and up to 100 mm in length), were prepared. For the laser evaluation the Cr:ZnSe samples in the form of 6 mm thick blocks were polished. Cr:ZnSe laser was longitudinally coherently pumped either with flashlamp-pumped Er:YAP laser radiation (emission wavelength 1658 nm) or with diode-pumped Tm:YAP laser radiation (emission wavelength 1980 nm). In the first case, the Cr:ZnSe laser was pumped with radiation of Er:YAP laser working in free-running regime (pulse length 200 &mgr;s, pulse energy 200 mJ, repetition rate 1 Hz). The maximal obtained Cr:ZnSe laser pulse energy was 14 mJ (slope-efficiency 73%). Using the dispersive prism inside the resonator, the output laser radiation was broadly tunable from 2150 nm up to 2600 nm. In the second case, the Cr:ZnSe laser was pumped with radiation of diode-pumped solid-state Tm:YAP laser working in pulsed as well as continuous-wave regime, for which the maximal obtained Cr:ZnSe laser output power was 200 mW (slope-efficiency 67%). The output spectrum of generated radiation covered the range from 2100 nm to 2400 nm. The temporal profile and spatial structure of laser beam were measured. The Cr:ZnSe crystal grown by the Bridgeman method was demonstrated as an efficient broadly tunable laser active material generated radiation in the mid-infrared spectrum and operated in room-temperature.