Dichroic Scanning Nonlinear Optical Microscope With Photodetecting Polymer Scanner and Objective Lens With External Back Focal Plane

Naitao Xu,Weiguo Liu,Menghua Wang,Jin Cheng,Bei Fang,Xin Li,Yingshun Xu

doi:10.1109/jphot.2021.3115402

Naitao Xu, Weiguo Liu + Show 5 more

Open Access

https://doi.org/10.1109/jphot.2021.3115402

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Abstract

In this article authors present a prototype of a dichroic scanning nonlinear optical microscope with a photodetecting polymer Scanner and a customized objective lens with an external back focal plane. Two types of two-axis electromagnetic actuated polymer scanners are manufactured by a standard printed circuit board (PCB) fabrication process. Both scanners share the same overall dimensions of 45 mm by 45 mm. The maximum optical scan angle of a type I scanner is 13 degrees at 420 Hz by the fast axis in resonance and 4 degrees by the slow axis in the linear mode. The type II scanner shows similar performance. A scan lens as well as a tube lens in a conventional nonlinear optical microscope are replaced by placing such a polymer scanner on the external back focal plane of a customized water immersion objective lens. The objective lens has the back working distance of 6 mm, the numerical aperture of 0.7, the front working distance of 1.16 mm, a field of view of 1.67 mm in the diameter and the angle of view of +/−15 degrees. Preliminary imaging results are also presented.

Highlights

N ONLIEAR optical microscopes (NOM) including well known multiphoton microscopes (MPM) [1]–[6], harmonic generation microscopes (HGM) [7]–[10] as well as coherent anti-stokes Raman scattering (CARS) microscopic imaging modalities [11]–[15] have been widely used in subcellular resolution imaging of biological samples and live animals
A customized Labview program is used to control a DAQ card (PCI-8554B, Art Technology, China) and a multifunction I/O card (PCI-8103, Art Technology, China) for digitalize signals converted by a transimpedance amplifier (TIA60, Thorlabs, NJ, USA) and manipulate the FR4 scanner. 920 nm laser pulses are generated by an ultrafast fiber laser
In this article authors have demonstrated a prototype of a compact dichroic scanning (DS)-NOM highlighting two types of FR4 scanner as well as a customized objective lens with external back focal plane (BFL)

Summary

Introduction

N ONLIEAR optical microscopes (NOM) including well known multiphoton microscopes (MPM) [1]–[6], harmonic generation microscopes (HGM) [7]–[10] as well as coherent anti-stokes Raman scattering (CARS) microscopic imaging modalities [11]–[15] have been widely used in subcellular resolution imaging of biological samples and live animals. Based on the flying spot scanning scheme, two-dimensional or threedimensional high-resolution images are generated by swinging. High photon intensity within the tiny focal region leads to the generation of a variety of nonlinear optical signals, which enhances specific contrasts of microscopic images. In order to collect very weak and scattered nonlinear optical signals in high efficiency, a large aperture photodetector, for example, a gallium arsenide phosphide (GaAsP) photomultiplier tube (PMT) with the 5 mm sensitive area, together with a focusing lens is placed next to a main dichroic filter which locates between a tube lens and an infinity corrected objective lens for the separation of the excitation and the emission light. Since emission photons never pass the scanner, it is called the non-descanned detection (NDD) photodetection scheme

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