Illumination by Near-Critical-Angle Incidence for Imaging Fluorescence Correlation Spectroscopy with Electron-Multiplying Charge-Coupled Device Camera
We developed a novel illumination method for imaging fluorescence correlation spectroscopy (imaging FCS) with electron-multiplying charge-coupled device (EM-CCD) to regulate the depth of observation volume. In this method, a laser beam for excitation is incident to a glass-water boundary at an angle...
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| Published in: | Japanese Journal of Applied Physics Vol. 49; no. 6; pp. 060208 - 060208-3 |
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| Main Authors: | , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
The Japan Society of Applied Physics
01-06-2010
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| Online Access: | Get full text |
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| Summary: | We developed a novel illumination method for imaging fluorescence correlation spectroscopy (imaging FCS) with electron-multiplying charge-coupled device (EM-CCD) to regulate the depth of observation volume. In this method, a laser beam for excitation is incident to a glass-water boundary at an angle slightly smaller than critical angle. Transmitted light excites molecules only in the vicinity of the boundary. Through an FCS imaging experiment and a simulation based on a finite-difference time-domain (FDTD) method, we have confirmed that field intensity decays exponentially with distance and penetration depth varies with incident angle until 2 \mbox{$\mu$m}, which is more than 10 times larger than that of a typical evanescent field. |
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| Bibliography: | Schematic diagram of critical-angle illumination. When the incident angle is close to the critical angle $\theta_{\text{c}}$, the transmitted light travels in parallel with the boundary. Evanescent-field-like light field is generated near the boundary. (a) Image obtained when the incident angle is 59.4\mbox{ \circ }. We analyzed the penetration lengths of illumination at three positions shown as A--C. (b) Penetration lengths of illumination at A--C derived from the number of particles. (c) Autocorrelation function $G(\tau)$ at B. (a) Field intensity distributions of critical angle illumination calculated by FDTD method at the incident angles of 59.0, 59.5, and 60.0\mbox{ \circ }. Standing wave generated by interference of incident and reflected waves is observed as a stripe pattern near the boundary. (b1)--(b3) Field intensity distributions from the boundary at each angle of incidence are shown as points. We also tried to fit these distributions to exponential decays (shown as lines). |
| ISSN: | 0021-4922 1347-4065 |
| DOI: | 10.1143/JJAP.49.060208 |