Hyper-numerical aperture (NA = 2.8) microscope using λ = 1.56 μm femtosecond source for multi-photon imaging

Youngsik Kim, Phat Lu, Tom D. Milster, Khanh Kieu

Research output: Contribution to journalArticle

5 Scopus citations


A new microscope is discussed, where the scanning illumination has a numerical aperture of 2.8 with λ = 1.56 μm femtosecond fiber laser. Samples are placed or grown on a silicon substrate. Multi-photon emission is imaged in transmission on a cooled CCD. Two-photon and three-photon effects are observed from the silicon/water interface and gold nanoparticles. Images of cells, reference spheres and gold nanoparticles illustrate imaging properties of the microscope. Spectral characteristics of individual particles are achieved with a blazed transmission grating. Emission properties of differently sized gold nanoparticles are studied in detail, which indicate that their emission is a two-photon effect due continuum generation. Interestingly, spectral shape and emission power are similar for 20nm, 40nm and 60nm diameter gold nanoparticles for the cases studied.

Original languageEnglish (US)
Pages (from-to)1786-1794
Number of pages9
JournalBiomedical Optics Express
Issue number10
StatePublished - Jan 1 2013


ASJC Scopus subject areas

  • Biotechnology
  • Atomic and Molecular Physics, and Optics

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