Tetravalent Chromium (Cr 4+) as Laser-Active Ion for TunableSolid-State Lasers

在提出的研究计划中，我们计划开发一系列以四价铬(Cr4)为激光活性离子的新型可调谐固体激光材料，并研究它们的光谱和激光性质。这些新型的可调谐固体激光器有望工作在技术上重要的近红外光谱区1-2微米。传统的掺铬激光器是基于Cr3作为活性离子的。为了更好地理解这些可调谐固体激光器中的激光机制，我们将研究各种新的四价铬掺杂激光晶体的光谱和激光特性。每年将选择一个具有合适的四面体位置的主体晶体候选晶体，其中Cr4离子可能取代四价阳离子，并生长用于光谱和激光研究。最有希望的晶体基质是晶格中含有SiO4或GeO4四面体的各种氧化物晶体。将测量吸收光谱、激发光谱、荧光光谱和荧光寿命随温度和波长的变化，以确定光学活性中心。将测量增益和激发态吸收，以确定四价铬掺杂晶体中可能的损耗机制。将研究不同的激光操作模式。由二次谐波产生的预期激光(1-2微米)和形成(500-1000 nm)波长对于光通信、相干激光雷达、夜视技术、遥感、测距、反措施、红外半导体诊断和医疗应用。

In the proposed research program we plan to develop a series of new tunable solid-state laser materials based on tetravalent chromium (Cr4+) as laser-active ion in various low field dielectric crystal hosts and study their spectroscopic and laser properties. These novel tunable solid state lasers are expected to operate in the technologically important near infrared spectral region between 1 - 2 um. Conventional chromium-doped lasers are based on Cr3+ as an active ion. The spectroscopic and lasing properties of the various new tetravalent chromium-doped laser crystals will be investigated in order to obtain better understanding of lasing mechanisms in these tunable solid-state lasers. One host crystal candidate with suitable tetrahedral sites where Cr4+ ion may substitute for a tetravalent cation will be selected and grown for spectroscopic and laser studies each year. Most promising crystal hosts are various oxide crystals containing the SiO4 or GeO4 tetrahedra in its crystal lattice. Measurements of the absorption spectra, excitation spectra, fluorescence spectra, and fluorescence lifetime as a function of temperature and wavelength will be performed to identify optically active centers. Gain and excited state absorption will be measured to determine possible loss mechanisms in tetravalent chromium-doped crystals. Different modes of laser operation will be investigated. The expected lasing (1-2 um) and forming (500-1000nm) wavelengths by second harmonic generation are important for many possible applications in optical communication, coherent laser radar, night vision technology, remote sensing, range finding, counter measure, infrared semiconductor diagnosis, and medical applications.