Atsushi Shibukawa, Ryota Higuchi, Gookho Song, Hideharu Mikami, Yuki Sudo and Mooseok Jang : Large-volume focus control at 10 MHz refresh rate via fast line-scanning amplitude-encoded scattering-assisted holography, Nature Communications, 15, 1, 2024.
(要約)
Abstract The capability of focus control has been central to optical technologies that require both high temporal and spatial resolutions. However, existing varifocal lens schemes are commonly limited to the response time on the microsecond timescale and share the fundamental trade-off between the response time and the tuning power. Here, we propose an ultrafast holographic focusing method enabled by translating the speed of a fast 1D beam scanner into the speed of the complex wavefront modulation of a relatively slow 2D spatial light modulator. Using a pair of a digital micromirror device and a resonant scanner, we demonstrate an unprecedented refresh rate of focus control of 31 MHz, which is more than 1,000 times faster than the switching rate of a digital micromirror device. We also show that multiple micrometer-sized focal spots can be independently addressed in a range of over 1 MHz within a large volume of 5 mm × 5 mm × 5.5 mm, validating the superior spatiotemporal characteristics of the proposed technique – high temporal and spatial precision, high tuning power, and random accessibility in a three-dimensional space. The demonstrated scheme offers a new route towards three-dimensional light manipulation in the 100 MHz regime.
Masuzu Kikuchi, Keiichi Kojima, Shin Nakao, Susumu Yoshizawa, Shiho Kawanishi, Atsushi Shibukawa, Takashi Kikukawa and Yuki Sudo : Functional expression of the eukaryotic proton pump rhodopsin OmR2 in Escherichia coli and its photochemical characterization., Scientific Reports, 11, 1, 14765, 2021.
(要約)
Microbial rhodopsins are photoswitchable seven-transmembrane proteins that are widely distributed in three domains of life, archaea, bacteria and eukarya. Rhodopsins allow the transport of protons outwardly across the membrane and are indispensable for light-energy conversion in microorganisms. Archaeal and bacterial proton pump rhodopsins have been characterized using an Escherichia coli expression system because that enables the rapid production of large amounts of recombinant proteins, whereas no success has been reported for eukaryotic rhodopsins. Here, we report a phylogenetically distinct eukaryotic rhodopsin from the dinoflagellate Oxyrrhis marina (O. marina rhodopsin-2, OmR2) that can be expressed in E. coli cells. E. coli cells harboring the OmR2 gene showed an outward proton-pumping activity, indicating its functional expression. Spectroscopic characterization of the purified OmR2 protein revealed several features as follows: (1) an absorption maximum at 533 nm with all-trans retinal chromophore, (2) the possession of the deprotonated counterion (pKa = 3.0) of the protonated Schiff base and (3) a rapid photocycle through several distinct photointermediates. Those features are similar to those of known eukaryotic proton pump rhodopsins. Our successful characterization of OmR2 expressed in E. coli cells could build a basis for understanding and utilizing eukaryotic rhodopsins.
Keiichi Kojima, Natsuki Miyoshi, Atsushi Shibukawa, Srikanta Chowdhury, Masaki Tsujimura, Tomoyasu Noji, Hiroshi Ishikita, Akihiro Yamanaka and Yuki Sudo : Green-Sensitive, Long-Lived, Step-Functional Anion Channelrhodopsin-2 Variant as a High-Potential Neural Silencing Tool, The Journal of Physical Chemistry Letters, 11, 15, 6214-6218, 2020.
(要約)
Anion channelrhodopsin-2 (GtACR2) was identified from the alga Guillardia theta as a light-gated anion channel, providing a powerful neural silencing tool for optogenetics. To expand its molecular properties, we produced here GtACR2 variants by strategic mutations on the four residues around the retinal chromophore (i.e., R129, G152, P204, and C233). After the screening with the Escherichia coli expression system, we estimated spectral sensitivities and the anion channeling function by using the HEK293 expression system. Among the mutants, triple (R129M/G152S/C233A) and quadruple (R129M/G152S/P204T/C233A) mutants showed the significantly red-shifted absorption maxima (λmax = 498 and 514 nm, respectively) and the long-lived channel-conducting states (the half-life times were 3.4 and 5.4 s, respectively). In addition, both mutants can be activated and inactivated by different wavelengths, representing their step-functional ability. We nicknamed the quadruple mutant "GLaS-ACR2" from its green-sensitive, long-lived, step-functional properties. The unique characteristics of GLaS-ACR2 suggest its high potential as a neural silencing tool.
Keiichi Kojima, Atsushi Shibukawa and Yuki Sudo : The Unlimited Potential of Microbial Rhodopsins as Optical Tools, Biochemistry, 59, 3, 218-229, 2019.
(要約)
Microbial rhodopsins, a photoactive membrane protein family, serve as fundamental tools for optogenetics, an innovative technology for controlling biological activities with light. Microbial rhodopsins are widely distributed in nature and have a wide variety of biological functions. Regardless of the many different known types of microbial rhodopsins, only a few of them have been used in optogenetics to control neural activity to understand neural networks. The efforts of our group have been aimed at identifying and characterizing novel rhodopsins from nature and also at engineering novel variant rhodopsins by rational design. On the basis of the molecular and functional characteristics of those novel rhodopsins, we have proposed new rhodopsin-based optogenetics tools to control not only neural activities but also "non-neural" activities. In this Perspective, we introduce the achievements and summarize future challenges in creating optogenetics tools using rhodopsins. The implementation of optogenetics deep inside an in vivo brain is the well-known challenge for existing rhodopsins. As a perspective to address this challenge, we introduce innovative optical illumination techniques using wavefront shaping that can reinforce the low light sensitivity of the rhodopsins and realize deep-brain optogenetics. The applications of our optogenetics tools could be extended to manipulate non-neural biological activities such as gene expression, apoptosis, energy production, and muscle contraction. We also discuss the potentially unlimited biotechnological applications of microbial rhodopsins in the future such as in photovoltaic devices and in drug delivery systems. We believe that advances in the field will greatly expand the potential uses of microbial rhodopsins as optical tools.
(キーワード)
脳 (brain) / Drug Delivery Systems / Gene Expression Regulation, Bacterial / Humans / Optogenetics / Rhodopsins, Microbial
Taro Yamanashi, Misayo Maki, Keiichi Kojima, Atsushi Shibukawa, Takashi Tsukamoto, Srikanta Chowdhury, Akihiro Yamanaka, Shin Takagi and Yuki Sudo : Quantitation of the neural silencing activity of anion channelrhodopsins in Caenorhabditis elegans and their applicability for long-term illumination, Scientific Reports, 9, 1, 7863, 2019.
(要約)
Ion pumps and channels are responsible for a wide variety of biological functions. Ion pumps transport only one ion during each stimulus-dependent reaction cycle, whereas ion channels conduct a large number of ions during each cycle. Ion pumping rhodopsins such as archaerhodopsin-3 (Arch) are often utilized as light-dependent neural silencers in animals, but they require a high-density light illumination of around 1 mW/mm2. Recently, anion channelrhodopsins -1 and -2 (GtACR1 and GtACR2) were discovered as light-gated anion channels from the cryptophyte algae Guillardia theta. GtACRs are therefore expected to silence neural activity much more efficiently than Arch. In this study, we successfully expressed GtACRs in neurons of the nematode Caenorhabditis elegans (C. elegans) and quantitatively evaluated how potently GtACRs can silence neurons in freely moving C. elegans. The results showed that the light intensity required for GtACRs to cause locomotion paralysis was around 1 µW/mm2, which is three orders of magnitude smaller than the light intensity required for Arch. As attractive features, GtACRs are less harmfulness to worms and allow stable neural silencing effects under long-term illumination. Our findings thus demonstrate that GtACRs possess a hypersensitive neural silencing activity in C. elegans and are promising tools for long-term neural silencing.
Atsushi Shibukawa, Keiichi Kojima, Yu Nakajima, Yosuke Nishimura, Susumu Yoshizawa and Yuki Sudo : Photochemical Characterization of a New Heliorhodopsin from the Gram-Negative Eubacterium Bellilinea caldifistulae (BcHeR) and Comparison with Heliorhodopsin-48C12, Biochemistry, 58, 26, 2934-2943, 2019.
(要約)
Many microorganisms express rhodopsins, pigmented membrane proteins capable of absorbing sunlight and harnessing that energy for important biological functions such as ATP synthesis and phototaxis. Microbial rhodopsins that have been discovered to date are categorized as type-1 rhodopsins. Interestingly, researchers have very recently unveiled a new microbial rhodopsin family named the heliorhodopsins, which are phylogenetically distant from type-1 rhodopsins. Among them, only heliorhodopsin-48C12 (HeR-48C12) from a Gram-positive eubacterium has been photochemically characterized [Pushkarev, A., et al. (2018) Nature 558, 595-599]. In this study, we photochemically characterize a purple-colored heliorhodopsin from Gram-negative eubacterium Bellilinea caldifistulae (BcHeR) as a second example and identify which properties are or are not conserved between BcHeR and HeR-48C12. A series of photochemical measurements revealed several conserved properties between them, including a visible absorption spectrum with a maximum at around 550 nm, the lack of ion-transport activity, and the existence of a second-order O-like intermediate during the photocycle that may activate an unidentified biological function. In contrast, as a property that is not conserved, although HeR-48C12 shows the light adaptation state of retinal, BcHeR showed the same retinal configuration under both dark- and light-adapted conditions. These comparisons of photochemical properties between BcHeR and HeR-48C12 are an important first step toward understanding the nature and functional role of heliorhodopsins.
Yuta Goto, Atsushi Okamoto, Atsushi Shibukawa, Kazuhisa Ogawa and Akihisa Tomita : Virtual phase conjugation based optical tomography for single-shot three-dimensional imaging, Optics Express, 26, 4, 3779-3790, 2018.
(要約)
We propose a virtual phase conjugation (VPC) based optical tomography (VPC-OT) for realizing single-shot optical tomographic imaging systems. Using a computer-based numerical beam propagation, the VPC combines pre-modulation and post-demodulation of the probe beam's wavefront, which provides an optical sectioning capability for resolving the depth coordinates. In VPC-OT, the physical optical microscope system and VPC are coupled using digital holography. Therefore, in contrast to conventional optical tomographic imaging (OTI) systems, this method does not require additional elements such as low-coherence light sources or confocal pinholes. It is challenging to obtain single-shot three-dimensional (3D) tomographic images using a conventional OTI system; however, this can be achieved using VPC-OT, which employs both digital holography and computer based numerical beam propagation. In addition, taking into account that VPC-OT is based on a complex amplitude detection using digital holography, this method allows us to simultaneously obtain quantitative phase contrast images. Using an objective lens with a numerical aperture (NA) of 0.8, we demonstrate a single-shot 3D imaging of frog blood cells with a depth resolution of 0.94 μm.
Edward Haojiang Zhou, Atsushi Shibukawa, Joshua Brake, Haowen Ruan and Changhuei Yang : Glare suppression by coherence gated negation, Optica, 3, 10, 1107-1113, 2016.
(要約)
Imaging of a weak target hidden behind a scattering medium can be significantly confounded by glare. We report a method, termed coherence gated negation (CGN), that uses destructive optical interference to suppress glare and allow improved imaging of a weak target. As a demonstration, we show that by permuting through a set range of amplitude and phase values for a reference beam interfering with the optical field from the glare and target reflection, we can suppress glare by an order of magnitude, even when the optical wavefront is highly disordered. This strategy significantly departs from conventional coherence gating methods in that CGN actively "gates out" the unwanted optical contributions while conventional methods "gate in" the target optical signal. We further show that the CGN method can outperform conventional coherence gating image quality in certain scenarios by more effectively rejecting unwanted optical contributions.
Nicolino Stasio, Atsushi Shibukawa, Ioannis N. Papadopoulos, Salma Farahi, Olivier Simandoux, Jean-Pierre Huignard, Emmanuel Bossy, Christophe Moser and Demetri Psaltis : Towards new applications using capillary waveguides, Biomedical Optics Express, 6, 12, 4619-4631, 2015.
(要約)
In this paper we demonstrate the enhancement of the sensing capabilities of glass capillaries. We exploit their properties as optical and acoustic waveguides to transform them potentially into high resolution minimally invasive endoscopic devices. We show two possible applications of silica capillary waveguides demonstrating fluorescence and optical-resolution photoacoustic imaging using a single 330 μm-thick silica capillary. A nanosecond pulsed laser is focused and scanned in front of a capillary by digital phase conjugation through the silica annular ring of the capillary, used as an optical waveguide. We demonstrate optical-resolution photoacoustic images of a 30 μm-thick nylon thread using the water-filled core of the same capillary as an acoustic waveguide, resulting in a fully passive endoscopic device. Moreover, fluorescence images of 1.5 μm beads are obtained collecting the fluorescence signal through the optical waveguide. This kind of silica-capillary waveguide together with wavefront shaping techniques such as digital phase conjugation, paves the way to minimally invasive multi-modal endoscopy.
Jin Nozawa, Atsushi Okamoto, Atsushi Shibukawa, Masanori Takabayashi and Akihisa Tomita : Two-channel algorithm for single-shot, high-resolution measurement of optical wavefronts using two image sensors, Applied Optics, 54, 29, 8644-8652, 2015.
(要約)
We propose a two-channel holographic diversity interferometer (2ch-HDI) system for single-shot and highly accurate measurements of complex amplitude fields with a simple optical setup. In this method, two phase-shifted interference patterns are generated, without requiring a phase-shifting device, by entering a circularly polarized reference beam into a polarizing beam splitter, and the resulting patterns are captured simultaneously using two image sensors. However, differences in the intensity distributions of the two image sensors may lead to serious measurement errors. Thus, we also develop a two-channel algorithm optimized for the 2ch-HDI to compensate for these differences. Simulation results show that this algorithm can compensate for such differences in the intensity distributions in the two image sensors. Experimental results confirm that the combination of the 2ch-HDI and the calculation algorithm significantly enhances measurement accuracy.
Atsushi Shibukawa, Atsushi Okamoto, Masanori Takabayashi and Akihisa Tomita : Spatial cross modulation method using a random diffuser and phase-only spatial light modulator for constructing arbitrary complex fields, Optics Express, 22, 4, 3968-3982, 2014.
(要約)
We propose a spatial cross modulation method using a random diffuser and a phase-only spatial light modulator (SLM), by which arbitrary complex-amplitude fields can be generated with higher spatial resolution and diffraction efficiency than off-axis and double-phase computer-generated holograms. Our method encodes the original complex object as a phase-only diffusion image by scattering the complex object using a random diffuser. In addition, all incoming light to the SLM is consumed for a single diffraction order, making a diffraction efficiency of more than 90% possible. This method can be applied for holographic data storage, three-dimensional displays, and other such applications.
Tomohiro Maeda, Atsushi Okamoto, Yuki Hirasaki, Atsushi Shibukawa and Akihisa Tomita : Reconfigurable spatial mode conversion using a phase-type spatial light modulator, 2014 OptoElectronics and Communication Conference, OECC 2014 and Australian Conference on Optical Fibre Technology, ACOFT 2014, 517-518, 2014.
Atsushi Shibukawa, Atsushi Okamoto, Yuta Wakayama, Akihisa Tomita, Hisatoshi Funakoshi and Kunihiro Sato : Digital Image Diffusion Technique for Suppressing Interpage Crosstalk in Holographic Data Storage, Japanese Journal of Applied Physics, 52, 9, 09LD03, 2013.
(要約)
<jats:p> To suppress interpage crosstalk that strongly restricts holographic data storage capacity, a digital image diffusion technique was proposed. In this technique, signal and crosstalk components are separated from the propagation angle difference produced by using a random diffuser and the nature of phase conjugate lights. The most attractive feature of the technique is that crosstalk suppression can be conducted while mostly keeping the conventional holographic data storage system unchanged by integrating optical processing and digital processing effectively. The connection between the two types of processing is realized by using two spatial light modulators for complex amplitude generation and phase detection methods for complex amplitude measurement. The simulation results showed that the proposed technique could increase the recording density 5.5-fold and reduce the shift pitch by a factor of 5 in comparison with conventional multiplexing methods when the diffusion angle of the diffuser is 10°. </jats:p>
Keisuke Zukeran, Atsushi Okamoto, Masanori Takabayashi, Atsushi Shibukawa, Kunihiro Sato and Akihisa Tomita : Double-Referential Holography and Spatial Quadrature Amplitude Modulation, Japanese Journal of Applied Physics, 52, 9, 09LD13, 2013.
(要約)
<jats:p> We proposed a double-referential holography (DRH) that allows phase-detection without external additional beams. In the DRH, phantom beams, prepared in the same optical path as signal beams and preliminary multiplexed in a recording medium along with the signal, are used to produce interference fringes on an imager for converting a phase into an intensity distribution. The DRH enables stable and high-accuracy phase detection independent of the fluctuations and vibrations of the optical system owing to medium shift and temperature variation. Besides, the collinear arrangement of the signal and phantom beams leads to the compactness of the optical data storage system. We conducted an experiment using binary phase modulation signals for verifying the DRH operation. In addition, 38-level spatial quadrature amplitude modulation signals were successfully reproduced with the DRH by numerical simulation. Furthermore, we verified that the distributed phase-shifting method moderates the dynamic range consumption for the exposure of phantom beams. </jats:p>
Atsushi Shibukawa, Atsushi Okamoto, Akihisa Tomita, Masanori Takabayashi and Kunihiro Sato : Multilayer Collinear Holographic Memory with Movable Random Phase Mask, Japanese Journal of Applied Physics, 50, 9, 09ME10, 2011.
Hisatoshi Funakoshi, Atsushi Okamoto, Masanori Takabayashi, Yuta Wakayama and Atsushi Shibukawa : High-speed full motion analysis based on FFT-BPM for collinear holographic memory, Optics InfoBase Conference Papers, 2011.
Atsushi Shibukawa, Atsushi Okamoto, Akihisa Tomita, Masanori Takabayashi, Kunihiro Sato and Masatoshi Bunsen : Evaluation of the performance in multilayer collinear holographic memory with movable random phase mask, Optics InfoBase Conference Papers, 2011.
Yuta Goto, Atsushi Okamoto, Atsushi Shibukawa, Akihisa Tomita and Masanori Takabayashi : High-resolution and simultaneous measurement along the depth direction using virtual phase conjugation for optical tomography, 2015 20th Microoptics Conference (MOC), 1-2, 2015.
(要約)
To improve the measurement speed of optical tomography based on the virtual phase conjugation, a virtual measurement position control technique is proposed. Tomographic images were observed with high depth-resolution and high acquisition rate in the numerical simulations.
Yuta Goto, Atsushi Okamoto, Atsushi Shibukawa, Akihisa Tomita and Kunihiro Sato : Optical tomography using a random diffuser and digital phase conjugation, Optical Tomography and Spectroscopy of Tissue XI, 9319, 2015.
(要約)
We proposed a new technology for tomographic imaging based on beam diffusion and wavefront reconstruction through digital phase conjugation (DPC). The principle of this technology is highly unique and completely different from that of well-known optical coherence tomography (OCT) because it does not utilize the coherence property of light. In our experiment, it was shown that the depth resolution of smaller than 5μm is obtained when using the objective lens with NA of 0.42. In addition, we achieved the extraction of the information from a specific specimen among several specimens arranged along optical axis.
Mooseok Jang and Atsushi Shibukawa : Accelerating complex wavefront shaping with line-scanning holography using digital micromirror devices, SPIE Photonics West,
2.
Atsushi Shibukawa : Wavefront shaping-assisted subcellular-resolution focus scanning over centimeter-scale field-of-view, The 13th Asia-Pacific Laser Symposium 2025, May 2025.
3.
Hyojeong Shon, Atsushi Shibukawa and Hideharu Mikami : Wavefront shaping-assisted multi-regional two-photon microscopy for recording distributed neuronal activity across the mouse cortex, Focus on microscopy 2025, Apr. 2025.
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Atsushi Shibukawa : Ultra-wide field-of-view optical focus control with high-speed complex wavefront shaping, The 85th JSAP Autumn Meeting 2024, Sep. 2024.
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Atsushi Shibukawa, Yuki Sudo, Hideharu Mikami and Mooseok Jang : Wavefront shaping at 10 MHz refresh rate by exploiting the scan speed of a resonant scanner, The Pacific Rim Conference on Lasers and Electro-Optics (CLEO-PR) 2024, Aug. 2024.
Atsushi Shibukawa, Hideharu Mikami, Mooseok Jang and Yuki Sudo : Megahertz Wavefront Control through Scattering Media, The 22nd RIES-Hokudai International Symposium, Dec. 2021.
Atsushi Shibukawa, Jang Mooseok, Hideharu Mikami and Yuki Sudo : Ultrafast wavefront control involving scattering media, International Symposium on Imaging, Sensing, and Optical Memory 2021, Oct. 2021.