Upconverters

Bhawalkar J D, Swiatkiewicz J, Pan S J, Samarabandu J K, Liou W S, He G S, Berezney R, Cheng P C and Prasad P N 1996 Three-dimensional laser scanning two-photon fluorescence confocal microscopy of polymer materials using a new, efficient upconverting fluorophore Scanning 18 562-6... 

Figure C3.1.13. Experimentai configuration for far-UV nanosecond CD measurements using a frequency-upconverted Ti sapphire iaser as a probe source. Pj and P2 are Mgp2 Rochon poiarizers at cross orientations. SP is a strained transparent piate with about i ° of iinear birefringence for quasi-nuii eiiipsometric CD detection. Prism PMj and the iris Ij seiect the far-UV fourth hannonic of the argon iaser-pumped Ti-sapphire iaser s near-IR fundamentai output to probe the eiiipticity of the sampie. A second iaser beam at 532 nm is used to pump CD...

Upconverting Phosphor Technology (SRI Inti., OraSure) Electrochemical Luminescence (IGEN)... 

The term nonlinear optical property refers to an optical property, which can be modified by exposing the material to intense light irradiation. In this section, we focus on the cascaded first- (/ 1 ) and third-order ( / ) susceptibilities describing nonlinear absorption (ESA and 2PA) and nonlinear refraction (n2) processes. Z-scan, pump-probe, and two-photon upconverted fluorescence techniques are among the most used experimental methods for determining optical nonlinearities. 

The 2PF technique measures the upconverted fluorescence induced by 2PA. This technique allows for the measurement of 2PA cross sections that are less than tens of GMs when the fluorescence quantum yield is large. The technique was first proposed by Kaiser et al. [76] in 1961 and represents an indirect way to measure the 2PA cross section, which can be calculated by comparing the integrated fluorescence signal... 

The intensity of the upconverted beam as a function of the intensity of the exciting radiation for Er3+ doped into CeC>2 is given in the following table. Determine whether the up-conversion is likely to be a two- or three-photon absorption process. 

Input Intensity, /ex (arbitrary units) Upconverted Intensity, /up (arbitrary units)... 

The most prominent nanomaterials for bioanalysis at present are semiconductor QDs. Rare-earth doped upconverting nanocrystals and precious metal nanoparticles are becoming increasingly popular, yet they are still far from reaching the level of use of QDs. Other luminescent nanoparticles like carbon-based nanoparticles start to appear, but the synthesis and application of these materials are still in their infancy and not significant for practitioners in the field of bioanalysis. 

Lanthanide (Ln) - or rare-earth-doped upconverting nanocrystals usually have similar optical properties as their bulk counterparts [45]. Upconversion is characterized by the successive absorption of two or more photons via intermediate... 

This comparison of the spectroscopic properties of the different types of fluorescent reporters underlines that semiconductor QDs and upconverting nanoparticles have no analogs in the field of organic dyes. Therefore, their unique features are unrivaled. The different molecular labels detailed here each display unique advantages that can compete with some of the favorable features of QDs and upconverting phosphors such as long lifetimes in the case of MLC systems and lanthanide chelates or very narrow emission bands for lanthanide chelates beneficial for spectral multiplexing. 

Upconversion is included because it is a case, unlike aU the others presented, where the refractive index is not a concern in the design of the material. For upconversion, the important parameters for the designer include absorption bands and excited-state lifetimes. Einding the blank host to hold the emitters and keep them separated from each other is also part of the design task. In addition, this host often serves as the primary absorber of the tight to be upconverted. In the case of Er" ", the host contains Yb for this purpose. 

Furthermore, the upconverted luminescence phenomena of Er and Sm " have been observed in YVO4 film. Fig. 5(b) shows the upconverted emission spectrum of Er excited with 800nm and that of Sm excited with 940nm. The characteristic green... 

Boyer, J.C., Vetrone, R, Cuccia, L.A., and Capobianco, J.A. (2006) Synthesis of colloidal upconverting NaYR4 nanocrystals doped with Er ", Yb and Tm ", Yb " via thermal decomposition of lanttianide trifluoroacetate precursors. Journal of the American Chemical Society, 128, 7444—7445. 

Sivakumar S, Diamente PR, van Veggel FC. Silica-coated Ln (3-F)-doped LaF3 nanoparticles as robust down- and upconvert- 85. ing biolabels. Chem. Euro. J. 2006 12 5878-5884. 

SFG using femtosecond lasers allows all the resonances within the broad (-200 cm" ) bandwidth of the IR pulse to be probed simultaneously, without scanning the infrared source. To obtain spectral resolution in an SFG spectrum, the IR polarization is upconverted with a narrowband (-8 cm" ) visible beam, which is prepared by pulse shaping the output of a femtosecond laser. Only the frequency components of the pulse that interact resonantly with the vibrational modes are enhanced, resulting in an SFG spectrum [28, 29]. Owing to the use of femtosecond... 

Figure 3.105 shows the emission output by comparison of OP and TP excitation. A clear threshold behavior and linear increase of the intensity with increasing pump power can be seen in both cases. However, the threshold for TP excitation upconverted lasing is about 300 times larger compared to the threshold for OP excitation. Despite these superior properties one still has to keep in mind that the optical feedback has to be properly sealed in order to avoid photodamage during the excitation cycles. 

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