Alexandra Rapaport

Review of the properties of up-conversion phosphors for new emissive displays

In this paper, we review the properties of up-conversion (UC) materials and assess their potential for a new display technology. UC materials absorb near infrared light and re-emit in the visible. Some of their most appealing characteristics for displays are: a wide color gamut with very saturated colors, very high brightness operation without damage to the emitters, long lifetimes and efficiencies comparable to those of existing technologies. Other advantages include simplicity of fabrication, versatility of operation modes, and the potential for greatly reduced display weight and depth.

Solid-state laser spectral narrowing using a volumetric photothermal refractive Bragg grating cavity mirror

Dramatic spectral narrowing of two normally broadband lasers, Ti:sapphire and Cr:LiSAF, was achieved by simply replacing the output mirror with a reflective, volumetric Bragg grating recorded in photothermal refractive glass. The output power of each laser was unchanged from that obtained using dielectric coated output mirrors with the same output coupling as the Bragg grating while spectral brightness increased by 3 orders of magnitude.

Temperature dependence of the 1.06-µm stimulated emission cross section of neodymium in YAG and in GSGG

A linear temperature dependence between -70 degrees C and +70 degrees C is reported for the peak stimulated emission cross section of Nd3+ ions in both yttrium aluminum garnet (YAG) and gadolinium scandium gallium garnet (GSGG).

High-brightness white-light source based on up-conversion phosphors

We report the implementation of a new, high brightness, high efficiency white-light source based on up-conversion phosphors. Up-conversion materials absorb near infrared light and re-emit in red, green, and blue. It is possible to combine these colors to create a white-light source. Such a source has the same appealing characteristics as those reported for up-conversion displays: very high brightness operation without damage to the emitters, long lifetimes, and efficiencies comparable to those of existing technologies. In addition, they offer simplicity of fabrication and a variety of operating modes. Here we demonstrate a 7-lm/W D65 white light emitter yielding 2 kcd/m 2 on a simple diffuser

Volume Bragg Gratings as Ultra-Narrow and Multiband Optical Filters

High efficiency volume Bragg gratings (VBGs) in photo-thermo-refractive (PTR) glass provide unmatched optical filtering capabilities with optical densities as high as 50 dB and linewidths as narrow as 1 cm-1. In this work we review recent advances in VBG technologies that enabled key improvements of high efficiency grating properties and led to development of unique VBG based optical filters for Raman spectroscopy and other applications. Such narrow band notch and bandpass filters make ultra-low frequency Raman measurements possible with single stage spectrometers, therefore, largely improving optical throughput of high end Raman instruments while reducing complexity of the measurements. In this work we also present novel volume multiplexed ultra-narrow band VBG filters with high reflection at multiple wavelengths. Such multiband holographic optical elements are formed by overlapping of several high efficiency VBGs in a single glass plate. Raman spectra obtained with multiband VBG filters and single stage spectrometers, show unmatched capability of the filters to provide simultaneous access to Stokes and anti-Stokes Raman modes with frequencies as low as 5 cm-1 at different wavelengths.

Doubling the optical efficiency of a chiral liquid crystal laser using a reflector

A simple method for doubling the laser emission efficiency of Nd:yttrium-aluminum-garnet pumped cholesteric liquid crystal (CLC) photonic band edge lasers is demonstrated. By adding a mirror or a CLC reflector behind the dye-doped CLC cell, the lasing intensity is nearly doubled. For the mirror reflector, due to the mixing of right-handed and left-handed circular polarizations, the output laser is basically unpolarized. However, for the CLC reflector, a partially coherent laser can be built in which either right-handed or left-handed circularly polarized laser could dominate the output, depending on the handedness of the cholesteric structure.

Optical spectroscopy and lasing properties of neodymium-doped lutetium orthophosphate

Studies of the spectroscopic and lasing properties of Nd3+-doped LuPO4 are reported. LuPO4 permits incorporation of lanthanide dopants in high concentration. We report the absorption and luminescence properties of Nd3+ ions doped at 10% in this host. Promising laser performance with diode laser pumping is also described.

Optical spectroscopy of erbium-doped lutetium orthophosphate

Abstract Experimental spectroscopic investigations of the absorption and luminescence properties of Er3+ ions doped into single crystals of the tetragonal-symmetry host LuPO4 are reported. The LuPO4 host permits the incorporation of relatively high concentrations of lanthanide dopants such as Er3+. The fluorescence decay of the 4 I 13/2 – 4 I 15/2 emission was found to be governed by a single exponential decay process when excited with a low-intensity pump source. However, experiments performed on samples of different concentrations show that Er3+ ions in LuPO4 experience concentration quenching as well as self-trapping. Using high-Er-concentration samples, emissions were also observed at visible wavelengths due to up-conversion processes.

Visible light emission from dyes excited by simultaneous absorption of two different frequency beams of light

Emission of visible light by dyes in both liquid and polymer hosts is reported when excited by simultaneous absorption of infrared light from two different wavelength sources. By moving the intersection point of these two beams about within the volume of the dye-doped medium, one can create a true, real-time, three-dimensional display.

Crystal growth, spectroscopic characterization, and laser performance of a new efficient laser material Nd:Ba5(PO4)3F

High quality single crystals of neodymium doped barium fluorapatite have been grown by the Czochralski technique and evaluated as an optical gain medium. A product of the emission cross section and lifetime of Nd3+ luminescence of more than 1.8×10−22 cm2 s at 1055 nm, and laser performance with slope efficiency up to 65% have been obtained.