We have previously proposed and demonstrated the targeted-light delivery capability of wave-guided optical waveguides (WOWs). The full strength of this structure-mediated paradigm can be harnessed by addressing multiple WOWs and manipulating them to work in tandem. We propose the use of diffractive techniques to create multiple focal spots that can be coupled into light manipulated WOWs. This is done by using a spatial light modulator to project the necessary phase to generate the multiple coupling light spots. We incorporate a diffractive setup in our Biophotonics Workstation (BWS) and demonstrate holographic shaping, tracking of light in 3D with the purpose of coupling light in the WOWs.
We demonstrate the efficient generation of line patterns using matched-filtering Generalized Phase Contrast (mGPC). So far, the main emphasis of mGPC light addressing has been on the creation of rapidly reconfigurable focused spots. This has recently been extended to encoding extended line patterns for structured light applications and advanced microscopy.
We are presenting so-called Wave-guided Optical Waveguides (WOWs) fabricated by two-photon polymerization and capable of being optically manipulated into any arbitrary orientation. By integrating optical waveguides into the structures we have created freestanding waveguides which can be positioned anywhere in a sample at any orientation using real-time 3D optical micromanipulation with six degrees of freedom. One of the key aspects of our demonstrated WOWs is the change in direction of in-coupled light and the marked increase in numerical aperture of the out-coupled light. Hence, each light propelled WOW can tap from a relatively broad incident beam and generate a much more tightly confined light at its tip. The presentation contains both numerical simulations related to the propagation of light through a WOW and preliminary experimental demonstrations on our BioPhotonics Workstation. In a broader context, this research shows that optically trapped micro-fabricated structures can potentially help bridge the diffraction barrier. This structure-mediated paradigm may be carried forward to open new possibilities for exploiting
beams from far-field optics down to the sub-wavelength domain.
Robotics can use optics feedback in vision-based control of intelligent robotic guidance systems. With light’s miniscule momentum, shrinking robots down to the microscale regime creates opportunities for exploiting optical forces and torques in microrobotic actuation and control. Indeed, the literature on optical trapping and micromanipulation attests to the possibilities for optical microrobotics. This work presents an optical microrobotics perspective on the optical microfabrication and micromanipulation work that we performed. We designed different three-dimensional microstructures and fabricated them by two-photon polymerization. These microstructures were then handled using our biophotonics workstation (BWS) for proof-of-principle demonstrations of optical actuation, akin to 6DOF actuation of robotic micromanipulators. Furthermore, we also show an example of dynamic behavior of the trapped microstructure that can be achieved when using static traps in the BWS. This can be generalized, in the future, towards a structural shaping optimization strategy for optimally controlling microstructures to complement approaches based on lightshaping. We also show that light channeled to microfabricated, free-standing waveguides can be used not only to redirect light for targeted delivery of optical energy but can also for targeted delivery of optical force, which can serve to further extend the manipulation arms in optical robotics. Moreover, light deflection with waveguide also creates a recoil force on the waveguide, which can be exploited for controlling the optical force.
We propose the use of consumer pico projectors as cost effective spatial light modulators in cell sorting applications. The
matched filtering Generalized Phase Contrast (mGPC) beam shaping method is used to produce high intensity optical
spots for trapping and catapulting cells. A pico projector’s liquid crystal on silicon (LCoS) chip was used as a binary
phase spatial light modulator (SLM) wherein correlation target patterns are addressed. Experiments using the binary
LCoS phase SLM with a fabricated Pyrex matched filter demonstrate the generation of intense optical spots that can
potentially be used for cell sorting. Numerical studies also show mGPC’s robustness to phase aberrations in the LCoS
device, and its ability to outperform a top hat beam with the same power.
The synergy between photonics, nanotechnology and biotechnology is spawning the emerging fields of nano-biotechnology
and nano-biophotonics. Photonic innovations already hurdle the diffraction barrier for imaging with
nanoscopic resolutions. However, scientific hypothesis testing demands tools, not only for observing nanoscopic
phenomena, but also for reaching into and manipulating nanoscale constituents in this domain. This report is two-fold
desribing the new use of proprietary strongholds we currently are establishing at DTU Fotonik on new means of
sculpting of both light and matter for bio-probing at the smallest scales.
The effect of a 1070-nm continuous and pulsed wave ytterbium fiber laser on the growth of Saccharomyces cerevisiae single cells is investigated over a time span of 4 to 5 h. The cells are subjected to optical traps consisting of two counterpropagating plane wave beams with a uniform flux along the x, y axis. Even at the lowest continuous power investigated-i.e., 0.7 mW-the growth of S. cerevisiae cell clusters is markedly inhibited. The minimum power required to successfully trap single S. cerevisiae cells in three dimensions is estimated to be 3.5 mW. No threshold power for the photodamage, but instead a continuous response to the increased accumulated dose is found in the regime investigated from 0.7 to 2.6 mW. Furthermore, by keeping the delivered dose constant and varying the exposure time and power-i.e. pulsing-we find that the growth of S. cerevisiae cells is increasingly inhibited with increasing power. These results indicate that growth of S. cerevisiae is dependent on both the power as well as the accumulated dose at 1070 nm.
We have studied the effect of a 1070 nm continuous wave Ytterbium fiber laser on exponentially growing
Saccharomyces cerevisiae yeast cells over a span of 4 hours. The cells were immobilized onto Concanavalin A covered
microscope slides and the growth was measured using the area increase of the cells in 2D. Using a continuous dual beam
plane wave with a uniform spatial intensity distribution, we found that a continuous radiant flux through a single cell as
low as 0.5 mW in 1.5 hours significantly changed the growth and division rate of S. cerevisiae. With the dual beam setup
used we were able to successfully manipulate single S. cerevisiae cells in 3 dimensions with a minimum flux thorough
the cell of 3.5 mW. In the regime investigated from 0.7 mW to 2.6 mW we found no threshold for the photo damage, but
rather a continuous response to the increased accumulated dose.