We present a small footprint and affordable implementation of a multifocal image scanning microscope (ISM), utilizing both a microelectromechanical system (MEMS) micromirror for flexible optical excitation control, and multifocal patterned illumination using a custom 3D printed optical quality lenslet array. We highlight the individual element performance and demonstrate its use in fluorescence imaging to allow comparison of the affordable and customizable approach with its commercial counterpart.
We present our latest results on a structured illumination microscope (SIM) implementation using individual microelectromechanical systems (MEMS) micromirrors with three-axis full angular, radial and phase control of the illumination pattern in the sample. Results of a simultaneous multi-color 2D SIM and 3D SIM implementation are shown with digital system adjustment to select the optimal imaging conditions and adapt to variable microscope objectives used in the system. Calibration and cell images of 2D and 3D samples will be shown to verify the resolution enhancement and axial sectioning potential.
Photonics is a broad research area that underpins many different areas of science and engineering. The future of the United Kingdom (UK) photonics industry depends on training the next generation of photonic engineers and scientists to lead research and innovation across a wide range of industrial applications. In 2018, the UK government invested £446 million through the Engineering and Physical Sciences Research Council (EPSRC) in 75 Centres for Doctoral Training (CDT), of which one is focused on industry inspired Photonics, Imaging, Sensing and Analysis (CDT in Applied Photonics). A key element of these CDTs is the increase in formal taught components to enhance technical interdisciplinary knowledge and broaden the postgraduate research student’s skills and knowledge base. This paper presents the development, implementation and evaluation of a new taught course for the CDT in Applied Photonics to broaden the skills of photonics researchers to integrate analogue and programmable digital electronics in to photonic systems. The course builds fundamental theoretical knowledge in digital and analogue electronics and provides practical laboratories using accessible programmable digital hardware. It also provides the opportunity to apply this knowledge through a practical group project developing an integrated photonic system, culminating in an assessed practical presentation and demonstration of the working systems. The course uses National Instrument’s myRIO, designed to allow access to industry-grade embedded system technology combining LabVIEW’s graphical programming environment with a processor, reconfigurable field programmable gate array (FPGA) and convenient hardware interfaces. This facilitates access to the technology for postgraduate students from a range of undergraduate backgrounds, yet also provides a pathway to develop similar technology used in industrial photonic research.
A 3D photoacoustic microscopy (PAM) system is presented and characterized, using optical MEMS and fibre tip transducers as active elements to provide all-optical positioning and read-out. The excitation beam position is controlled using an electrostatically actuated 2-axis MEMS scanner. This allows for fast 3D scanning without motion-induced artefacts caused by stage scanning, and selective imaging of regions of interest. A 20 MHz fibre tip transducer is used for acoustic detection, which allows a variety of sample holders to be used including common approaches such as multi-well plates and petri-dishes.
We present the development and application of a novel structured illumination microscope (SIM) in which the grating pattern is generated using two optical beams controlled via two micro-electro-mechanical system (MEMS) 3D scanning micromirrors, each having static angular and piston control. This arrangement enables the generation of a fully controllable spatial interference pattern at the focal plane by adjusting the positions of the beams in the back-aperture of a high numerical aperture (NA) microscope objective. The utilization of MEMS micromirrors to control angular, radial and phase positioning for the structured illumination patterns has advantages of flexible control of the fluorescence excitation illumination, with achromatic beam delivery through the same optical path, reduced spatial footprint and cost-efficient integration.
In this work, we present the results of using a commercially available SLA printer for the fabrication of a range of designs of optical components. The optical properties are compared to off-the-shelf optics, including a detailed analysis of optical transmission, part uniformity and surface quality. A post-processing refinement step is introduced whose results are benchmarked against off-the-shelf polished glass lensesto exemplify sub-hundred nanometre surface roughness uniformity with minimal surface defects, and transmission properties as high as 85% at 638 nm for a 1 mm thick optical block without anti-reflection coatings
A miniaturized version of a light-sheet microscopy (LSM) system, with 3D imaging enabled through active optical control, is presented. Even though the field of LSM technology has advanced significantly in recent years, it is still not considered an easily available technique. This is mainly due to its cost compared to epifluorescence setups and the requirement for specific sample mounting techniques in most cases, as well as stringent optical alignment and difficulty to reduce motion artifacts when the sample is moved through the light path to create the imaging slices. In our research, we demonstrate a miniaturized version of an LSM that can reduce size and cost, and is able to achieve 3D imaging through control of multiple active optical elements and MEMS micromirrors used in both the illumination and imaging path instead of moving the sample. The laser excitation is controlled and shaped via multiple MEMS elements for 3D beam position control and multi-lens beam shaping to generate a 2.85 μm wide light-sheet with controllable height of up to 550 μm, and orthogonal positioning over a 200 μm range. Additionally, the focal point of the excitation can be shifted along the laser propagation direction by 200 μm. The orthogonally positioned imaging path incorporates a x20, NA = 0.4 objective and a tunable lens for imaging selected focal planes synchronized with the excitation positioning. The imaging results show sub-micron resolution with a field-of-view of 400 μm x 300 μm. The synchronization of the two active elements allows for fast imaging of different slices of a sample and promises convenient 3D reconstruction and representation of cell tissue.
Active control of the spectral and temporal output characteristics of solid-state lasers through use of MEMS scanning micromirrors is presented. A side-pumped Nd:YAG laser with two intracavity scanning micromirrors, enabling Q-switching operation with controllable pulse duration and pulse-on-demand capabilities, is investigated. Changing the actuation signal of one micromirror allows a variation of the pulse duration between 370 ns and 1.06 μs at a pulse repetition frequency of 21.37 kHz and average output power of 50 mW. Pulse-on-demand lasing is enabled through actuation of the second micromirror. To our knowledge this is the first demonstration of the use of multiple intracavity MEMS devices as active tuning elements in a single solid-state laser cavity. Furthermore, we present the first demonstration of control over the output wavelength of a solid-state laser using a micromirror and a prism in an intracavity Littman configuration. A static tilt actuation of the micromirror resulted in tuning the output wavelength of an Yb:KGW laser from 1024 nm to 1031.5 nm, with FWHM bandwidths between 0.2 nm and 0.4 nm. These proof-of-principle demonstrations provide the first steps towards a miniaturized, flexible solid-state laser system with potential defense and industrial applications.
MEMS scanners are of interest for their potential as low-cost, low operating power devices for use in various photonic systems. The devices reported here are actuated by the electromagnetic force between a static external magnetic field and a current flowing through an SOI MEMS scanner. These scanners have several modes of operation: their mirrors may be rotated and maintained at a static angle (up to ± 1.4 degrees), scanned rapidly (up to 500 Hz); or may be operated in a resonance mode, at the device’s mechanical resonance frequency (~1.2 kHz) for higher rate scanning. The use of these scanners as a Q-switching element within a Nd:YAG laser cavity has been demonstrated. Pulse durations of 400 ns were obtained with a pulse energy of 58 μJ and a pulse peak power of 145 W. The use of an external magnetic field, generated by compact rare-earth magnets, allows a simple and cost-effective commercial fabrication process to be employed (the multi-user SOI process provided by MEMSCAP Inc) and avoids the requirement to deposit magnetic materials on the MEMS structure.
Multiple individually-controllable Q-switched laser outputs from a single diode-pumped Nd:YAG module are presented by using an electrostatic MEMS scanning micromirror array as cavity end-mirror. The gold coated, 700 μm diameter and 25 μm thick, single-crystal silicon micromirrors possess resonant tilt frequencies of ~8 kHz with optical scan angles of up to 78°. Dual laser output resulting from the actuation of two neighboring mirrors was observed resulting in a combined average output power of 125 mW and pulse durations of 30 ns with resulting pulse energies of 7.9 μJ and 7.1 μJ. The output power was limited by thermal effects on the gold-coated mirror surface. Dielectric coatings with increased reflectivity and therefore lower thermal stresses are required to power-scale this technique. An initial SiO2/Nb2O5 test coating was applied to a multi-mirror array with individual optical scan angles of 14° at a resonant tilt frequency of 10.4 kHz. The use of this dielectric coated array inside a 3-mirror Nd:YAG laser cavity led to a single mirror output with average Q-switched output power of 750 mW and pulse durations of 295 ns resulting in pulse energies of 36 μJ.
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