We proposed superresolution nonlinear fluorescence microscopy with pump-probe setup that utilizes repetitive stimulated absorption and stimulated emission caused by two-color laser beams. The resulting nonlinear fluorescence that undergoes such a repetitive stimulated transition is detectable as a signal via the lock-in technique. As the nonlinear fluorescence signal is produced by the multi-ply combination of incident beams, the optical resolution can be improved. A theoretical model of the nonlinear optical process is provided using rate equations, which offers phenomenological interpretation of nonlinear fluorescence and estimation of the signal properties. The proposed method is demonstrated as having the scalability of optical resolution. Theoretical resolution and bead image are also estimated to validate the experimental result.
In this work, we study the influence of optical process on the resolution limit of laser microscopy. We formulate the calculation rules of the resolution limits for all types of laser microscopy that employ a variety of optical processes occurring in a sample. By replacing the field with the creation/annihilation operators, we develop a theoretical framework to unify the image-forming formulas that cover all interactions between molecules in the sample and the excitation light including vacuum field. To determine the simple rules for the evaluation of optical resolution, our theoretical framework provides the diagram method that describes linear, nonlinear, coherent, and incoherent optical processes. According to our formulas, the type of optical process decisively influences the resolution limit if no a priori information on the sample exists.
We propose a two-photon imaging system and formulate the property of the system into an image-formation formulae. The idea of two-photon image-formation, in which the entangled photon pairs are utilized, unveils the possibility of the advancement in resolution. We show that the two-photon microscopy beats the diffraction limit and discuss the resolution of this high-resolving optical system.
We formulate an image-forming optical theory of quantum lithography in which Entangled-photon pairs generated by spontaneous parametric down-conversion play an important role. Our optical system consists of an image-forming system, an illumination system with a second-order nonlinear medium, and two-photon absorbing materials. We evaluate the resolution of the quantum lithography system by using the optical transfer function and show a super-resolving condition which is, however, difficult to achieve.
At the end of last century, the name of “quantum lithography” has been emerged. This exciting approach was proposed for making a resolution two times higher than that of the conventional optics without changing a wavelength and a numerical aperture. For those who want optical lithography to last long, this has been thought to be a great technology. However, an applicability of the proposed method to the current exposure system i.e., reduced projection exposure system has not yet been examined clearly. We have investigated the proposed quantum lithography to apply into the current exposure system using reticle. For simplicity, coherent illumination i.e. sigma is zero condition is used for calculation. Our quantum lithography compatible to mask exposure system explains probability of one and two photon absorption on the image plane i.e. on wafer. We have shown that the half-wavelength quantum lithography using conventional mask exposure system is impossible because diffraction at the mask makes biphoton into two photon. We have found that there is still super-resolution quantum lithography using mask exposure, however, there is little possibility of quantum lithography practically today because biphoton light source is as dark as stars. To realize quantum lithography practically, further development of not only biphoton light source but also two-photon absorption resist is indispensable.