To avoid the unwanted non-resonant background contribution induced by cross-phase modulation (XPM) in Stimulated Raman Scattering (SRS) microscopy , the collection of forward transmitted signal is normally done with a microscope objective having a numerical aperture (NA) higher than the objective used for excitation. However, while high NA microscope objectives are usually bulky and expensive, because a complex design is needed to achieve good optical imaging performances, only a capability to collimate highly divergent beams is needed for forward detection of signal in SRS microscopy. Additionally, because high NA microscope objectives have a short working distance and are bulky, their use as forward collecting optical element is not compatible with tightly closed top-stage incubators, as used in live-cell experiments.
Here we show the use of a high NA 3D printed ultra-thin optical lens, composed of micro-reflective and -refractive elements, to replace commercial high NA microscope objectives for forward collection of signal in Stimulated Raman Scattering microscopy.
The lens is fabricated on a 170µm thick coverslip with direct laser writing based on Two-Photon Lithography with a commercial system (Nanoscribe) and using the proprietary IP-S photoresist. It has a thickness of 300 µm and a diameter of 1 cm. Thanks to its compactness, this optical element can easily fit inside top-stage microscope incubators. The resulting NA of this catadioptric condenser lens is 1.2 when working in water immersion. We show the complete removal of the non-resonant XPM contribution from SRS spectra of incubated cells.
 Ji-Xin Cheng, Xiaoliang Sunney Xie, Coherent Raman scattering microscopy, CRC press, 2016.
Andrea Bertoncini and Carlo Liberale, "3D printed high-NA ultra-thin catadioptric condenser to minimize background contribution from cross-phase modulation in stimulated Raman scattering microscopy (Conference Presentation)," Proc. SPIE 10882, Multiphoton Microscopy in the Biomedical Sciences XIX, 1088229 (Presented at SPIE BiOS: February 07, 2019; Published: 4 March 2019); https://doi.org/10.1117/12.2510085.6008555588001.
Conference Presentations are recordings of oral presentations given at SPIE conferences and published as part of the proceedings. They include the speaker's narration with video of the slides and animations. Most include full-text papers. Interactive, searchable transcripts and closed captioning are now available for most presentations.
Search our growing collection of more than 18,000 conference presentations, including many plenaries and keynotes.