Publisher Summary This chapter describes the symmetry aspects of the crystal field and the parametrization of the energy level scheme. It provides an overview of the experimental data of trivalent lanthanide ions doped into crystalline host matrices. The selection rules for induced electric dipole (ED) and magnetic dipole (MD) transitions for systems with even or odd numbers of f electrons in different site symmetries are presented. Methods for the assignment of crystal-field levels are discussed and the determination of phenomenological crystal-field parameters is described. Such a set of crystal-field parameters in combination with a suitable set of free-ion parameters allows calculating crystal-field energy levels and reconstructing the energy diagram of the 4fn configuration. In this way, it is not only possible to check the validity of the crystal-field model but also to get information about energy levels, which cannot be detected experimentally.

Chapter 155 Rationalization of crystal-field parametrization

Publisher Summary The intensities of intraconfigurational f–f transitions are reviewed in the chapter The chapter presents the transition mechanisms for lanthanide ions—namely, the magnetic dipole transition, the induced electric dipole transition, and the electric quadrupole transition It discusses the way experimental intensities can be determined from the spectra The chapter also focuses on the expression of the dipole strength and the oscillator strength in oriented and in randomly-oriented systems Correction factors for lanthanide ions in a dielectric medium are described in the chapter Although only a few magnetic dipole transitions exist for the trivalent lanthanide ions, magnetic dipole transitions are of interest, because their intensities are in a first approximation independent of the ligand environment and can, thus, be used as intensity standards The intensity of a magnetic dipole transition can be calculated exactly, provided that suitable wavefunctions are available These wavefunctions can be obtained from diagonalization of the energy matrix

Chapter 167 Spectral intensities of f-f transitions

After a brief examination of known insulating laser crystals and the stimulated emission channels of their generating activator ions, this article reviews recent advances in the development of novel lasing crystals and ceramics, as well as inorganic and organic nonlinear-laser crystals for χ(3) and cascaded χ(3) ↔ χ(2) frequency converters Several new modern attractive technologies in the physics and techniques of crystalline lasers are also discussed

https://onlinelibrary.wiley.com/doi/pdf/10.1002/lpor.200710008

Laser crystals and ceramics: recent advances

Frequency down-conversion of solid-state laser sources to the mid-infrared spectral range using non-oxide nonlinear crystals

A diode‐array side‐pumped Er, Yb: phosphate glass laser has been constructed. Pumped with two 970 nm, InGaAs strained‐layer diode arrays, a long pulse slope efficiency of 14% was obtained, with thresholds of 60 mJ input, a maximum output pulse energy of 20 mJ, and with output wavelengths at 1545±12 nm. When Q‐switched, the laser generated 0.3 mJ, 50 ns FWHM pulses at an output wavelength of 1533±1 nm. Visible upconversion emission in the laser rod was observed.

Diode array‐pumped Er, Yb: Phosphate glass laser

Nd:YAG (YAG) and Nd:Lu:YAG (LYAG) are investigated as high-efficiency laser materials utilizing a diode-array side-pump geometry. We demonstrate higher laser efficiencies than previously reported for transversely pumped YAG. A YAG rod yielded an optical slope efficiency of 47.7%, while a LYAG rod yielded an optical slope efficiency of 50.3%. Increased performance of these materials is attributed to higher pump absorption and lower losses.

Efficient diode-array-pumped Nd:YAG and Nd:Lu:YAG lasers.

A 100 Hz, optical parametric oscillator (OPO) lidar breadboard is designed, built and tested for remote chemical sensing in the 8 - 12 micrometers range. Continuous tuning is achieved by angle tuning a type II, silver gallium selenide (AgGaSe2) OPO crystal pumped in a single step by a 2.088-micrometers pump laser. The pump source for the OPO consists of a temperature stabilized, continuously pulsed, resonantly pumped Ho:YAG (2.088-micrometers ) laser, end-pumped by a diode- end-pumped Tm:YLF (1.9-micrometers ) laser. The 9 mm X 5 mm X 25 mm-long OPO crystal was mounted on a computer-controlled galvanometer scanner for rapid wavelength tuning (1.5 micrometers between shots). Continuous tunability was demonstrated from 7.9 to 12.6 micrometers with energies in the 50 - 400 (mu) J range. Quantum slope conversion efficiencies up to 40% were obtained. Far-field beam divergence measurement showed the output of the OPO to be 2.6 times diffraction limit. The improved OPO beam quality over previous studied tandem OPO systems is attributed to the reduced Fresnel number of the OPO cavity (idler resonating) and the better beam quality of the pump source. A LabWindows based data collection and analysis system is implemented. The effectiveness of the OPO as a source for chemical sensing is demonstrated by the collection of the absorption spectrum of ammonia.

2-μm-pumped 8-12-μm OPO source for remote chemical sensing

Preparation, structure, and spectroscopic properties of Nd3+:{La1-xLux}3

Nd3+:Ba2ZnGe2O7 (BZAG) is an attractive material to be pumped by laser diodes because its fluorescence lifetime is 305 μsec and it has a broad absorption centered at 806 nm. In addition, Nd3+:BZAG has a broad fluorescence spectrum and offers the potential for tunable laser output wavelengths centered at 1.05 and 1.34 μm. Time-resolved, site-selection spectroscopy measurements revealed ten different crystal-field sites for Nd3+ in BZAG, but strong energy transfer between nonequivalent ions at room temperature results in emission from only one major site. Diode-array side pumping of 5-mm-diameter rods produced optical slope efficiencies of 22.8%. Crystal structure, Judd–Ofelt analysis, and laser performance are discussed.

Crystallography, spectroscopic analysis, and lasing properties of Nd 3+ :Ba 2 ZnGe 2 O 7

In this paper, we review some recent advances in optical parametric oscillator (OPO) technology, discuss major coherentsource issues and then propose possible solutions that have relevance to remote chemical sensing. The authors discuss theirlatest results on two OPO schemes. 1) Energies up to 1.2 mJ/pulse and continuously tunable OPO output from 6.7 to 9.8 m was obtained using a 5 x 5 x 25 mm type II AgGaS2 crystal, pumped directly by a 10 ns, 1.06 .tm Nd:YAG laser. 2)The 3.5 pm idler output from a Nd:YAG pumped KTA OPO was used to pump a second OPO using NCPM ZnGeP2 togenerate output near 8 pm. The tandem OPO produced pulse energies of > 1 . 5 mJ at 7. 8 m with an energy conversion efficiency of 6.8%. Finally, we describe schemes for generating multiple photons in the 8 - 12 j.tm band from one initial 1im pump photon, and thereby increase the quantum efficiency when OPOs are pumped by Nd:YAG lasers.Keywords: LIDAR laser technology, optical parametric oscillators, 8  12 p.m coherent sources, nonlinear optics, andinfrared laser sources.

Wayne W. Hovis

Papers

Efficient diode-array-pumped Nd:YAG and Nd:Lu:YAG lasers.

2-μm-pumped 8-12-μm OPO source for remote chemical sensing

Preparation, structure, and spectroscopic properties of Nd3+:{La1-xLux}3

Crystallography, spectroscopic analysis, and lasing properties of Nd 3+ :Ba 2 ZnGe 2 O 7

Advances in optical parametric oscillators with application to remote chemical sensing