Wavelength Conversion Devices Research Articles

Synthesis and growth processes for zinc germanium diphosphide

Zinc germanium diphosphide (ZnGeP 2) has useful properties for wavelength conversion devices in the mid-in-frared (IR) spectral range. It has a high figure of merit as an optical parametric oscillator (OPO) and it also performs efficiently as a frequency doubler. Present crystal growth technology has been restricted to small volume charges because of the pressure limits of quartz containment vessels. The authors discuss a new approach to synthesis based on direct injection of phosphorus through a B 2O 3 encapsulant and reaction with the zinc germanium melt, resulting in synthesis of a large melt (350 g) of ZnGeP 2. When crystallization is followed by cooling the congruent melt down through the α-β transition temperature (952°C) as is typical for bulk growth processes, the result is the growth of partially disordered material. An alternative approach for the growth of ZnGeP 2 below the phase transition temperature by chemical vapor transport (CVT) is discussed. The results of crystal growth below the α-β phase transition temperature are reported.

Tunable lasers. General remarks: Tunable sources between vacuum ultraviolet and far infrared region.

This preface to the special issue on 'Tunalbe lasers' briefly reviews the present status of tunable coherent sources covering a wide spectral region from vacuum ultraviolet to far infrared, and mentions a guideline for the selection of these sources. The tunable sources are classified into three groups: tunable lasers, nonlinear wavelength-conversion devices, and free electron lasers.