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Biomedical Optics Express

Biomedical Optics Express

  • Editor: Joseph A. Izatt
  • Vol. 5, Iss. 7 — Jul. 1, 2014
  • pp: 2125–2134
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Vibrationally resonant sum-frequency generation microscopy with a solid immersion lens

Eun Seong Lee, Sang-Won Lee, Julie Hsu, and Eric O. Potma  »View Author Affiliations


Biomedical Optics Express, Vol. 5, Issue 7, pp. 2125-2134 (2014)
http://dx.doi.org/10.1364/BOE.5.002125


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Abstract

We use a hemispheric sapphire lens in combination with an off-axis parabolic mirror to demonstrate high-resolution vibrationally resonant sum-frequency generation (VR-SFG) microscopy in the mid-infrared range. With the sapphire lens as an immersed solid medium, the numerical aperture (NA) of the parabolic mirror objective is enhanced by a factor of 1.72, from 0.42 to 0.72, close to the theoretical value of 1.76 ( = nsapphire). The measured lateral resolution is as high as 0.64 μm. We show the practical utility of the sapphire immersion lens by imaging collagen-rich tissues with and without the solid immersion lens.

© 2014 Optical Society of America

1. Introduction

Optical microscopy with mid-infrared (MIR; 2.5-25 μm) light enables spectroscopic imaging with contrast based on molecular vibrational modes. Several linear and nonlinear optical imaging techniques with vibrational contrast have been developed for biological applications in the MIR region with high sensitivity [1

1. B. C. Smith, Fundamentals of Fourier Transform Infrared Spectroscopy (CRC Press, Boca Raton, 2011).

7

7. Y. Han, V. Raghunathan, R. R. Feng, H. Maekawa, C. Y. Chung, Y. Feng, E. O. Potma, and N. H. Ge, “Mapping molecular orientation with phase sensitive vibrationally resonant sum-frequency generation microscopy,” J. Phys. Chem. B 117(20), 6149–6156 (2013). [CrossRef] [PubMed]

]. Among these, vibrationally resonant sum-frequency generation (VR-SFG) microscopy is a second-order nonlinear optical imaging technique, which is sensitive to samples with noncentrosymmetry [6

6. V. Raghunathan, Y. Han, O. Korth, N. H. Ge, and E. O. Potma, “Rapid vibrational imaging with sum frequency generation microscopy,” Opt. Lett. 36(19), 3891–3893 (2011). [CrossRef] [PubMed]

12

12. J. H. Jang, J. Jacob, G. Santos, T. R. Lee, and S. Baldelli, “Image contrast in sum-frequency generation microscopy based on monolayer order and coverage,” J. Phys. Chem. C 117(29), 15192–15202 (2013). [CrossRef]

]. VR-SFG is suitable for imaging biopolymers with a nonvanishing second-order susceptibility χ(2), such as collagen, microtubules and cellulose. The molecular modes in VR-SFG are excited with an optical frequency ω1 in the MIR range, followed by an upconversion with a second optical frequency ω2 in the visible/near-infrared range to generate a visible signal at ω1 + ω2. Since χ(2) is frequency dependent in the MIR range, the signal grows stronger when the ω1 frequency approaches resonances of SFG-active molecular vibrational modes.

An attractive feature of objective-based VR-SFG microscopy is that it enables MIR-based imaging with a spatial resolution well below a micrometer, as the size of the probing volume is defined by the product of the MIR and the visible/NIR excitation spots [6

6. V. Raghunathan, Y. Han, O. Korth, N. H. Ge, and E. O. Potma, “Rapid vibrational imaging with sum frequency generation microscopy,” Opt. Lett. 36(19), 3891–3893 (2011). [CrossRef] [PubMed]

,7

7. Y. Han, V. Raghunathan, R. R. Feng, H. Maekawa, C. Y. Chung, Y. Feng, E. O. Potma, and N. H. Ge, “Mapping molecular orientation with phase sensitive vibrationally resonant sum-frequency generation microscopy,” J. Phys. Chem. B 117(20), 6149–6156 (2013). [CrossRef] [PubMed]

]. In addition, the visible signal can be efficiently captured with standard optics and detected with sensitive photodetectors in the visible range. Nonetheless, the VR-SFG resolution is inferior to that of conventional forms of optical microscopy, because the high numerical aperture (NA) refractive objectives that are commonly used in the visible/NIR region are incompatible with MIR excitation light. Objective-based VR-SFG microscopy has been achieved with all-reflective objectives such as Schwarzschild-type lenses [6

6. V. Raghunathan, Y. Han, O. Korth, N. H. Ge, and E. O. Potma, “Rapid vibrational imaging with sum frequency generation microscopy,” Opt. Lett. 36(19), 3891–3893 (2011). [CrossRef] [PubMed]

,7

7. Y. Han, V. Raghunathan, R. R. Feng, H. Maekawa, C. Y. Chung, Y. Feng, E. O. Potma, and N. H. Ge, “Mapping molecular orientation with phase sensitive vibrationally resonant sum-frequency generation microscopy,” J. Phys. Chem. B 117(20), 6149–6156 (2013). [CrossRef] [PubMed]

]. Although Schwarzschild lenses are commercially available, their maximum NA is presently 0.65, which is well below the NA of standard refractive objectives. Moreover, the Schwarzschild objective features a central obscuration that affects the shape and size of the focal volume compared to refractive objectives [13

13. D. S. Grey, “A new series of microscope objectives; Preliminary investigation of catadioptric Schwarzschild systems,” J. Opt. Soc. Am. 39(9), 723–728 (1949). [CrossRef] [PubMed]

,14

14. S. T. Yang, R. L. Hsieh, Y. H. Lee, R. F. W. Pease, and G. Owen, “Effect of central obscuration on image formation in projection lithography,” Proc. SPIE 1264, 477–485 (1990). [CrossRef]

]. The central obscuration produces a point-spread function that exhibits more pronounced diffraction side lobes in the lateral dimension, and an elongated profile in the axial dimension. These unwanted properties of the focal excitation fields produce distorted images, result in exceptionally poor axial resolution and give rise to inefficient nonlinear signal generation [15

15. N. Olivier, D. DéBarre, P. Mahou, and E. Beaurepaire, “Third-harmonic generation microscopy with Bessel beams: a numerical study,” Opt. Express 20(22), 24886–24902 (2012). [CrossRef] [PubMed]

].

Evidently, these complications have prevented VR-SFG microscopy to reach its full potential. Alternative excitation schemes that improve the quality of the focal volume are highly desirable. In this work, we make an important step towards improving the imaging performance of the VR-SFG microscope. Our scheme is based on the use of an all-reflective off-axis parabolic mirror of short focal length and wide aperture. To further enhance the focusing capability of the parabolic mirror, we implement a solid immersion lens (SIL) method, where the high refractive index of the lens material increases the effective NA of the focusing system [16

16. S. M. Mansfield and G. S. Kino, “Solid immersion microscope,” Appl. Phys. Lett. 57(24), 2615–2616 (1990). [CrossRef]

22

22. K. Cohn, D. Simanovskii, T. Smith, and D. Palanker, “Transient photoinduced diffractive solid immersion lens for infrared microscopy,” Appl. Phys. Lett. 81(19), 3678–3680 (2002). [CrossRef]

]. The SIL technology has been previously used in optical pickup devices to increase the data density of optical data storage systems [23

23. B. D. Terris, H. J. Mamin, and D. Rugar, “Near-field optical data storage,” Appl. Phys. Lett. 68(2), 141–143 (1996). [CrossRef]

26

26. T. S. Song, H. D. Kwon, Y. J. Yoon, K. S. Jung, N. C. Park, and Y. P. Park, “Aspherical solid immersion lens of integrated optical head for near-field recording,” Jpn. J. Appl. Phys. 42(Part 1, No. 2B), 1082–1089 (2003). [CrossRef]

]. Here we implement an off-the-shelf, hemispheric sapphire SIL for simultaneously focusing MIR and NIR to demonstrate high-resolution VR-SFG imaging with an effective NA of 0.72. We show that this simple and cost-effective solution produces high quality SFG images of collagen-rich biological tissues such as tendon and cornea.

2. Experimental setup

Before focusing, the ω1 and ω2 beams are linearly polarized in parallel fashion. The expanded beams are incident on a short focal length off-axis parabolic mirror (Edmund Optics, focal length = 25.4 mm), which acts as an objective lens and forms a focal spot in the sample. When the aperture of the mirror is filled, the effective NA of the focusing element is 0.42. The sapphire SIL is placed above the parabolic mirror in such a way that the focal point is just above the SIL flat surface, as illustrated in Fig. 1. To do so, we observe the partially reflected beam from the SIL spherical surface and retrace it to the incoming beam path. The MIR wavelength was tuned to 3.4 μm (2945 cm−1) corresponding to the methylene mode of collagen, and the associated NIR beam was set at 775 nm. The samples are put on the SIL surface and raster-scanned using a two-axis piezo translation stage for generating 2D images. The SFG signal is detected in the forward propagation direction by a photomultiplier tube (PMT) via the condenser lens and a 632 ± 22 nm bandpass filter.

3. Ray tracing through the sapphire SIL

To optimize the experimental layout, we perform ray tracing and point spread function (PSF) simulations using commercial software (ZEMAX) for modeling the performance of the sapphire SIL in combination with the off-axis parabolic mirror. To model the effect of the reflective mirrors, we assume that the radiation after the last focusing mirror can be described as a perfect converging spherical wavefront, which is incident on the SIL. After passing through the SIL, the light propagates into the water medium, which closely mimics the experimental situation. The refractive indices of sapphire used in the simulations are 1.76 and 1.70 at the wavelengths 775 nm and 3.4 μm respectively, while those of water are 1.33 and 1.42 respectively. The diameter of the hemispheric SIL is 6.35 mm. Only the ordinary wave for birefringent sapphire is considered here. Because the polarization of incident laser beams can be adjusted precisely to either orientation in actual experiments, and the refractive index difference is less than 0.5% between two polarizations, the assumption of one ordinary index value is appropriate.

The ray tracing and focal intensity calculation results for three cases are shown in Fig. 2
Fig. 2 Ray tracing and PSF calculation results of solid immersion VR-SFG microscopy. Traced rays from the parabolic mirror (a) without SIL and (b),(c) with SIL. (c) represents the situation that the laser beam focuses 10 μm deep into the water medium. The ray tracing is performed at 775 nm. Focal spot intensity distributions of the corresponding cases calculated (d),(e),(f) at 775 nm and (g),(h),(i) at 3.4 μm. The scale bars are (d),(e),(f) 1 μm and (g),(h),(i) 2 μm. The ray tracings at 3.4 μm are not presented here due to the similarity with those at 775 nm. It is noticeable that no appreciable aberration is induced even though the laser beams focus far beyond the SIL surface.
. Figure 2(a) represents the focusing beam from the parabolic mirror (at the bottom; not shown) with an effective NA 0.42 without SIL, where the wavelength is set to 775 nm. The beam is focused onto the air-water interface and produces a diffraction-limited spot, as shown in Fig. 2(d). The full-width at half-maximum (FWHM) of the spot is 1.07 μm. Figure 2(b) and 2(e) show the corresponding results with the SIL inserted. The FWHM at the flat SIL surface is reduced by nsapphire (nsapphire = refractive index of sapphire, 1.76) to provide a focal spot with a width of 0.61 μm; a direct manifestation of the increased NA. These results model the situation relevant to SIL focusing in optical pickup applications, where the evanescent field within ~200 nm from SIL surface plays an important role in reducing the focal spot size relative to the focus formed through free-space diffraction. In the present study, however, because the incident converging angle is below the critical angle at the sapphire-water interface, no evanescent field is generated. This implies that focusing with an increased effective NA is not limited to the region near the interface, but can instead be achieved deeper into the water medium. Figure 2(c) shows the case in which the focal point is placed 10 μm above the SIL surface. Figure 2(f) shows that the FWHM of the focal intensity in this case is comparable to the situation in Fig. 2(e). The result is intriguing in that high-resolution imaging is still possible for objects placed away from the SIL surface.

To model the situation of deeper focusing in Fig. 2(c), we decrease the distance between parabolic mirror and SIL by 20 μm to raise the focus above the SIL surface. We find that the reduced FWHM persists up to ~20 μm from the SIL surface. Beyond this distance, spherical aberration starts to become more significant, which broadens the focal volume. The 20 μm range is relevant for the present study because the penetration depth of water is around 10 μm in the MIR region of interest [27

27. M. K. Hong, A. G. Jeung, N. V. Dokholyan, T. I. Smith, H. A. Schwettman, P. Huie, and S. Erramilli, “Imaging single living cells with a scanning near-field infrared microscope based on a free electron laser,” Nucl. Instrum. Methods Phys. Res. B 144(1-4), 246–255 (1998). [CrossRef]

]. The PSF calculation results for the MIR excitation wavelength of 3.4 μm are shown in Fig. 2(g)-2(i) for similar scenarios. We note that as the focal point is removed farther away from the SIL surface (as in Fig. 2(c)), chromatic aberrations in the sapphire material grow more significant. The refractive index difference between the 775 nm and 3.4 μm excitation wavelengths amounts to 3.4%, which introduces a small chromatic focal shift of ~1.2 μm when focusing 10 μm deep into the sample. This chromatic focal shift is small compared to the axial extent of the focal volume, which amounts to 3.5 μm FWHM at a focusing depth of 10 μm.

An important advantage of the current configuration is the lack of a central obscuration in the focusing geometry. To illustrate this point, we have performed calculations of the axial FWHM at the focusing depth of 10 μm when the central portion of the incident beam is blocked by an opaque pupil. We find that, if the pupil area is 15% of the total beam area, the axial FWHM is increased by 26%. When the pupil area is increased to 25% of the total beam area, elongation along the axial dimension is increased by 43%. These calculations confirm that central obscuration of the beam significantly affects confinement along the axial coordinate.

We note that a maximum NA of up to 1.33 for water-dipped samples is, in principle, possible by either increasing the mirror diameter or further decreasing the focal length of the parabolic mirror.

4. Experimental results and discussion

Finally we apply the solid immersion VR-SFG microscope to imaging collagen fibers in rat tail tendons and hawk cornea. The MIR wavelength is tuned to the 2945 cm−1 resonance of the methylene modes in collagen. The tissue samples are put directly on top of the flat SIL surface. A drop of water is used for immersion, and the sample is covered with a glass coverslip. The power levels of the parallel polarized NIR and MIR beams are 16 mW and 5 mW at 775 nm and 3.4 μm, respectively, as measured before the SIL. In Fig. 5
Fig. 5 (b),(d) Solid immersion VR-SFG microscopic images of biological samples compared to (a),(c) the corresponding images measured without SIL. (a),(b) Rat tail tendon collagen and (c),(d) hawk cornea collagen. The fields of view are 80 μm x 80 μm. The power levels of the parallel polarized NIR and MIR beams were 16 mW and 5 mW at 775 nm and 3.4 μm, respectively.
, VR-SFG images are shown for the situation with (5b, d) and without (Fig. 5(a), 5(c)), the sapphire SIL. The total acquisition time for each image was 1 minute for an image with 256 × 256 pixels, primarily limited by the scan speed of the piezo translation stage rather than the magnitude of the VR-SFG signal. In general, we observe that the images obtained with the SIL show finer collagen structures and more details compared to the images without the SIL. The more pronounced details are a direct consequence of the improved lateral resolution provided by the solid immersion.

Although this performance rivals the lateral resolution attained with commercial Schwarzschild objectives, it is important to underline that the images obtained with SIL focusing are not distorted by side lobes of the PSF and that the axial extent of the focal volume is markedly reduced. Our calculations show an axial resolution of 3.5 μm, which is significantly higher than what can be theoretically obtained with Schwarzschild-type lenses. Even though the current mounted SIL configuration prevents us from performing an axial scan to experimentally verify the axial resolution, it is clear from focal volume simulations that the absence of the center obscuration significantly improves the confinement along the axial dimension.

An important shortcoming of the current implementation is the fact that the SIL is mounted directly to the sample. In this configuration, the optical axis of the SIL is continuously displaced relative to optical axis of the system while scanning the translation stage. As the SIL axis moves away from the system axis, aberrations are introduced, which consequently limit the extent of the field-of-view (FOV). The effective FOV is a function of wavelength, lens diameter, incident NA, and refractive index of the SIL [28

28. M. Baba, T. Sasaki, M. Yoshita, and H. Akiyama, “Aberrations and allowances for errors in a hemisphere solid immersion lens for submicron-resolution photoluminescence microscopy,” J. Appl. Phys. 85(9), 6923–6925 (1999). [CrossRef]

]. A larger SIL provides a larger FOV. In our case, the diameter of the FOV is as large as 140 μm, much larger than the FOV of the images presented here. However, this limited area eventually makes it difficult to access different regions in the sample as the lens is mounted directly to the specimen. To solve this problem, we are currently considering a new design of the SIL that is composed of two elements, consisting of a thin plan-parallel plate and a thick planar convex spherical lens. The combined thickness of two pieces can be manufactured to match the radius of the original SIL. The sample is then positioned on the plate, while sliding over the flat surface of the lens, with the lens axis fixed while scanning.

Although sapphire is a hard material with a high refractive index, its birefringence complicates the alignment procedure. Other high refractive index materials that are optically isotropic, such as ZnSe, would simplify the alignment of the microscope. Future studies will focus on finding alternative materials for the solid immersion lens to improve the imaging properties of the microscope.

Because of the vast chromatic shifts between the excitations wavelengths, achieving high-resolution VR-SFG is a challenge. In this work, we show that some of these challenges can be overcome with relatively inexpensive focusing optics. The combination of an off-axis parabolic mirror and a sapphire SIL yields a lateral resolution of 0.64 μm, with a higher degree of 3D confinement than what was previously obtained with Schwarzschild objectives. Improving the lateral resolution further is relatively straightforward by increasing the aperture of the off-axis parabolic mirror. The possibility to reach higher resolution in VR-SFG with off-the-shelf optical components is significant, as it avoids the need for expensive, custom-designed reflective objectives, thus opening up the way for further development of VR-SFG microscopy into a practical high-resolution imaging technique.

5. Conclusion

We demonstrate high spatial resolution solid immersion VR-SFG microscopy in the MIR region by combining an off-axis parabolic mirror and a hemispheric sapphire SIL. Using the parabolic mirror as an objective lens, the central obscuration inherent to Schwarzschild objectives can be avoided, producing clean diffraction-limited focal volumes. The implementation of a sapphire solid immersion lens improved the effective NA of 0.42 to NA 0.72, in close agreement with theory. This focusing configuration can be extended to design NAs of up to 1.33 in aqueous media, without relying on evanescent near-field effects. We show that this simple and inexpensive focusing system is suitable for generating high quality VR-SFG images in biological samples such as rat tail tendon and hawk cornea.

Acknowledgment

We thank Prof. James Jester for providing the hawk cornea sample. We acknowledge support from Bio-signal Analysis Technology Innovation Program funded by the Ministry of Science, ICT and Future Planning, Republic of Korea. E. O. Potma is grateful for the support from NSF grant CHE-0847097, and NIH grant P41-RR01192 (Laser Microbeam and Medical Program, LAMMP). JH acknowledges support from the NSF IGERT program in biophotonics at UCI (NSF-DGE-1144901).

References and links

1.

B. C. Smith, Fundamentals of Fourier Transform Infrared Spectroscopy (CRC Press, Boca Raton, 2011).

2.

F. Garczarek and K. Gerwert, “Functional waters in intraprotein proton transfer monitored by FTIR difference spectroscopy,” Nature 439(7072), 109–112 (2006). [CrossRef] [PubMed]

3.

R. Mendelsohn, H. C. Chen, M. E. Rerek, and D. J. Moore, “Infrared microspectroscopic imaging maps the spatial distribution of exogenous molecules in skin,” J. Biomed. Opt. 8(2), 185–190 (2003). [CrossRef] [PubMed]

4.

K. Inoue, N. Bokor, S. Kogure, M. Fujii, and M. Sakai, “Two-point-separation in a sub-micron nonscanning IR super-resolution microscope based on transient fluorescence detected IR spectroscopy,” Opt. Express 17(14), 12013–12018 (2009). [CrossRef] [PubMed]

5.

E. S. Lee and J. Y. Lee, “High resolution cellular imaging with nonlinear optical infrared microscopy,” Opt. Express 19(2), 1378–1384 (2011). [CrossRef] [PubMed]

6.

V. Raghunathan, Y. Han, O. Korth, N. H. Ge, and E. O. Potma, “Rapid vibrational imaging with sum frequency generation microscopy,” Opt. Lett. 36(19), 3891–3893 (2011). [CrossRef] [PubMed]

7.

Y. Han, V. Raghunathan, R. R. Feng, H. Maekawa, C. Y. Chung, Y. Feng, E. O. Potma, and N. H. Ge, “Mapping molecular orientation with phase sensitive vibrationally resonant sum-frequency generation microscopy,” J. Phys. Chem. B 117(20), 6149–6156 (2013). [CrossRef] [PubMed]

8.

M. Flörsheimer, C. Brillert, and H. Fuchs, “Chemical imaging of interfaces by sum frequency microscopy,” Langmuir 15(17), 5437–5439 (1999). [CrossRef]

9.

K. Kuhnke, D. M. P. Hoffmann, X. C. Wu, A. M. Bittner, and K. Kern, “Chemical imaging of interfaces by sum-frequency generation microscopy: application to patterned self-assembled monolayers,” Appl. Phys. Lett. 83(18), 3830–3832 (2003). [CrossRef]

10.

K. A. Cimatu and S. Baldelli, “Chemical microscopy of surfaces by sum frequency generation imaging,” J. Phys. Chem. C 113(38), 16575–16588 (2009). [CrossRef]

11.

H. C. Hieu, N. A. Tuan, H. Li, Y. Miyauchi, and G. Mizutani, “Sum frequency generation microscopy study of cellulose fibers,” Appl. Spectrosc. 65(11), 1254–1259 (2011). [CrossRef] [PubMed]

12.

J. H. Jang, J. Jacob, G. Santos, T. R. Lee, and S. Baldelli, “Image contrast in sum-frequency generation microscopy based on monolayer order and coverage,” J. Phys. Chem. C 117(29), 15192–15202 (2013). [CrossRef]

13.

D. S. Grey, “A new series of microscope objectives; Preliminary investigation of catadioptric Schwarzschild systems,” J. Opt. Soc. Am. 39(9), 723–728 (1949). [CrossRef] [PubMed]

14.

S. T. Yang, R. L. Hsieh, Y. H. Lee, R. F. W. Pease, and G. Owen, “Effect of central obscuration on image formation in projection lithography,” Proc. SPIE 1264, 477–485 (1990). [CrossRef]

15.

N. Olivier, D. DéBarre, P. Mahou, and E. Beaurepaire, “Third-harmonic generation microscopy with Bessel beams: a numerical study,” Opt. Express 20(22), 24886–24902 (2012). [CrossRef] [PubMed]

16.

S. M. Mansfield and G. S. Kino, “Solid immersion microscope,” Appl. Phys. Lett. 57(24), 2615–2616 (1990). [CrossRef]

17.

L. P. Ghislain and V. B. Elings, “Near-field scanning solid immersion microscope,” Appl. Phys. Lett. 72(22), 2779–2781 (1998). [CrossRef]

18.

Q. Wu, R. D. Grober, D. Gammon, and D. S. Katzer, “Imaging spectroscopy of two-dimensional excitons in a narrow GaAs/AlGaAs quantum well,” Phys. Rev. Lett. 83(13), 2652–2655 (1999). [CrossRef]

19.

Q. Wu, G. D. Feke, R. D. Grober, and L. P. Ghislain, “Realization of numerical aperture 2.0 using a gallium phosphide solid immersion lens,” Appl. Phys. Lett. 75(26), 4064–4066 (1999). [CrossRef]

20.

D. A. Fletcher, K. B. Crozier, C. F. Quate, G. S. Kino, K. E. Goodson, D. Simanovskii, and D. V. Palanker, “Near-field infrared imaging with a microfabricated solid immersion lens,” Appl. Phys. Lett. 77(14), 2109–2111 (2000). [CrossRef]

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S. B. Ippolito, B. B. Goldberg, and M. S. Unlu, “High spatial resolution subsurface microscopy,” Appl. Phys. Lett. 78(26), 4071–4073 (2001). [CrossRef]

22.

K. Cohn, D. Simanovskii, T. Smith, and D. Palanker, “Transient photoinduced diffractive solid immersion lens for infrared microscopy,” Appl. Phys. Lett. 81(19), 3678–3680 (2002). [CrossRef]

23.

B. D. Terris, H. J. Mamin, and D. Rugar, “Near-field optical data storage,” Appl. Phys. Lett. 68(2), 141–143 (1996). [CrossRef]

24.

T. D. Milster, “Near-field optical data storage: avenues for improved performance,” Opt. Eng. 40(10), 2255–2260 (2001). [CrossRef]

25.

Y. Lu, J. Xie, J. Jhang, H. Ming, and P. Wang, “Increased the storage density of solid immersion lens system by high-pass angular spectrum filter method,” Opt. Commun. 203(1-2), 87–92 (2002). [CrossRef]

26.

T. S. Song, H. D. Kwon, Y. J. Yoon, K. S. Jung, N. C. Park, and Y. P. Park, “Aspherical solid immersion lens of integrated optical head for near-field recording,” Jpn. J. Appl. Phys. 42(Part 1, No. 2B), 1082–1089 (2003). [CrossRef]

27.

M. K. Hong, A. G. Jeung, N. V. Dokholyan, T. I. Smith, H. A. Schwettman, P. Huie, and S. Erramilli, “Imaging single living cells with a scanning near-field infrared microscope based on a free electron laser,” Nucl. Instrum. Methods Phys. Res. B 144(1-4), 246–255 (1998). [CrossRef]

28.

M. Baba, T. Sasaki, M. Yoshita, and H. Akiyama, “Aberrations and allowances for errors in a hemisphere solid immersion lens for submicron-resolution photoluminescence microscopy,” J. Appl. Phys. 85(9), 6923–6925 (1999). [CrossRef]

OCIS Codes
(110.3080) Imaging systems : Infrared imaging
(170.0180) Medical optics and biotechnology : Microscopy
(190.4223) Nonlinear optics : Nonlinear wave mixing
(180.4315) Microscopy : Nonlinear microscopy

ToC Category:
Microscopy

History
Original Manuscript: April 9, 2014
Revised Manuscript: May 21, 2014
Manuscript Accepted: May 21, 2014
Published: June 9, 2014

Citation
Eun Seong Lee, Sang-Won Lee, Julie Hsu, and Eric O. Potma, "Vibrationally resonant sum-frequency generation microscopy with a solid immersion lens," Biomed. Opt. Express 5, 2125-2134 (2014)
http://www.opticsinfobase.org/boe/abstract.cfm?URI=boe-5-7-2125


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References

  1. B. C. Smith, Fundamentals of Fourier Transform Infrared Spectroscopy (CRC Press, Boca Raton, 2011).
  2. F. Garczarek and K. Gerwert, “Functional waters in intraprotein proton transfer monitored by FTIR difference spectroscopy,” Nature439(7072), 109–112 (2006). [CrossRef] [PubMed]
  3. R. Mendelsohn, H. C. Chen, M. E. Rerek, and D. J. Moore, “Infrared microspectroscopic imaging maps the spatial distribution of exogenous molecules in skin,” J. Biomed. Opt.8(2), 185–190 (2003). [CrossRef] [PubMed]
  4. K. Inoue, N. Bokor, S. Kogure, M. Fujii, and M. Sakai, “Two-point-separation in a sub-micron nonscanning IR super-resolution microscope based on transient fluorescence detected IR spectroscopy,” Opt. Express17(14), 12013–12018 (2009). [CrossRef] [PubMed]
  5. E. S. Lee and J. Y. Lee, “High resolution cellular imaging with nonlinear optical infrared microscopy,” Opt. Express19(2), 1378–1384 (2011). [CrossRef] [PubMed]
  6. V. Raghunathan, Y. Han, O. Korth, N. H. Ge, and E. O. Potma, “Rapid vibrational imaging with sum frequency generation microscopy,” Opt. Lett.36(19), 3891–3893 (2011). [CrossRef] [PubMed]
  7. Y. Han, V. Raghunathan, R. R. Feng, H. Maekawa, C. Y. Chung, Y. Feng, E. O. Potma, and N. H. Ge, “Mapping molecular orientation with phase sensitive vibrationally resonant sum-frequency generation microscopy,” J. Phys. Chem. B117(20), 6149–6156 (2013). [CrossRef] [PubMed]
  8. M. Flörsheimer, C. Brillert, and H. Fuchs, “Chemical imaging of interfaces by sum frequency microscopy,” Langmuir15(17), 5437–5439 (1999). [CrossRef]
  9. K. Kuhnke, D. M. P. Hoffmann, X. C. Wu, A. M. Bittner, and K. Kern, “Chemical imaging of interfaces by sum-frequency generation microscopy: application to patterned self-assembled monolayers,” Appl. Phys. Lett.83(18), 3830–3832 (2003). [CrossRef]
  10. K. A. Cimatu and S. Baldelli, “Chemical microscopy of surfaces by sum frequency generation imaging,” J. Phys. Chem. C113(38), 16575–16588 (2009). [CrossRef]
  11. H. C. Hieu, N. A. Tuan, H. Li, Y. Miyauchi, and G. Mizutani, “Sum frequency generation microscopy study of cellulose fibers,” Appl. Spectrosc.65(11), 1254–1259 (2011). [CrossRef] [PubMed]
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