| 摘要 |
A particle detector (10, 12, 70) employs an upconversion laser medium (22, 72) to produce emission radiation (32) at an emission wavelength (56) that is less than the wavelength of the pumping radiation (26). The shorter emission wavelength (56) provides a significant increase in the scattering intensity (Isc) detected by the particle detector (10, 12, 70), based on the equation Isc=Io k/ lambda 4, where Io represents the intensity of emission radiation (32), lambda represents the wavelength (56) of the emission radiation (32), and k represents a coefficient related to particle size. In addition, the emission wavelength (56) of the upconversion laser medium (22, 72) can be frequency doubled to excite biological chromophores such as tryptophan, NADH, and flavin compounds that absorb in the UV spectral range and emit fluorescence at longer wavelengths that can be discretely detected to determine the presence of biological particles.
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