Stuart M. Jacobsen

Saturation of 1.064 μm absorption in Cr,Ca:Y3Al5O12 crystals

Saturation absorption experiments are conducted on the title compound at 1.064 μm with laser light propagating along both the [001] and [111] crystallographic axes. Rotation of the crystals about these axes during the experiments reveals that the transmission of the polarized 1.064 μm radiation is highly anisotropic in the saturation regime. The details of the anisotropy and saturation curves are explained using a simple model of subsets of optical centers along with a relevant set of rate equations. The ground and excited‐state absorption cross sections at 1.064 μm are calculated to be σgs=5.7(±2)×10−18 cm2 and σes=8(±2)×10−19 cm2, respectively, and the optimum crystallographic orientation for utilization in optical devices is discussed.

Near infrared luminescence properties of the laser material Cr: Y2SiO5

Abstract We report spectroscopic investigations of the near infrared (NIR) laser center in chromium doped Y 2 SiO 5 (YSO). A comprehensive study including polarized absorption and emission spectra, and the temperature dependence of the fluorescence decay time and the integrated emission intensity is presented. In addition, we performed high resolution excitation and emission measurements. The results are most consistent with the NIR center being attributed to Cr 4+ in a distorted tetrahedral site. The assignment of the energy levels and the identification of the metastable level responsible for the NIR laser action will be discussed in detail. The measurements further show that Cr: YSO does not contain octahedrally coordinated Cr 3+ which is in contrast to Cr : YAG and Cr : forsterite. In this sense, Cr: YSO can be regarded as a model system for studying the optical properties of the new NIR center.

On the emission and excitation spectrum of the NIR laser center in Cr:YAG

Abstract We use a tunable narrowband laser operating in the region 1.1–1.3 μm to probe the excitation spectrum of the NIR laser center in Cr doped yttrium aluminum garnet (YAG) at low temperatures. Our results reveal that the sharp emission bands observed at low temperatures around 1.28 μm are true electronic origins. This is in contrast to previous interpretations of this luminophore in which these sharp bands have been interpreted as false origins built on a zero phonon line supposed, but not observed, to lie midway between the 1.28 μm bands in emission and a sharp “false origin” absorption band at 1.125 μm. We discuss the possible nature of this luminophore in light of these new results.

Spectroscopic properties of Cr(4+):Lu(3)Al(5)O(12).

We report on the near-infrared absorption, emission, and lifetime data of Cr(4+):Lu(3)Al(5)O(12) (Cr:LAG) and compare the results with the known laser material Cr(4+)-doped Y(3)Al(5)O(12) (Cr:YAG). Lu(3)Al(5)O(12) has a smaller unit cell than Y(3)Al(5)O(12), and this feature is reflected in its spectroscopic properties. The low-temperature luminescence spectrum is shifted by 85 cm(-1) to higher energy compared with Cr:YAG. The luminescence lifetime of Cr:LAG at 10 K is 28.7 micros (Cr:YAG, 30.6 micros) and at 300 K is 4.3 micros (Cr:YAG, 3.5 micros). From these lifetimes we postulate that the quantum efficiency in Cr:LAG is higher than in Cr:YAG. We discuss the potential of Cr:LAG as a tunable near-infrared laser.

Infrared to violet up-conversion in YLiF4 : Nd3+

Abstract We investigate ultraviolet and visible up-conversion in YLiF4 : Nd3+ (1%). The energy of the ultraviolet emission is more than twice the energy of the infrared pump light. The up-conversion is determined to be dominated by an energy transfer process. Our experimental results are compared with a rate equation analysis.

The near-infrared emission of Cr:Mn2SiO4 and Cr:MgCaSiO4

We report on the near-infrared (NIR) emission of Cr:Mn2SiO4 (tephroite) and Cr:MgCaSiO4 (monticellite). Both systems are related to Cr:Mg2SiO4 (forsterite) which shows laser action in the NIR region. For both tephroite and monticellite the emission is shifted to longer wavelength compared with forsterite. Whilst the low-temperature zero-phonon lines in forsterite are at 1093 nm, they are located at 1141 and at 1226 nm in monticellite and tephroite, respectively. The room-temperature lifetime of Cr:monticellite is 5 μs, around twice as long as the Cr:forsterite lifetime. The emission of Cr:tephroite, on the other hand, is strongly quenched at room temperature.

High-Resolution Spectroscopy of Chromium-Doped Forsterite

We have measured high resolution emission and absorption spectra of the near infrared center in Chromium doped Forsterite. These results are compared to previous interpretations of this optical center. In addition, fluorescence line narrowing of the zero phonon lines has also been measured. To our knowledge this is the first line narrowing experiment performed on a d2 ion. The splittings in the ground and first excited state of the infrared center have been determined. Furthermore, the temperature dependence of the integrated absorbance has been measured and explained using a simple thermodynamic model.