We present a novel miniaturization strategy that allows us to create versatile compact Raman spectrometers and microscopes based on cheap non-stabilized laser diodes, densely-packed optics, and non-cooled small pixel size sensors. We demonstrate that the achieved performance is comparable with expensive and bulky research-grade Raman systems. Our miniaturization concept is based on real-time calibration of Raman shift and Raman intensity using a built-in reference channel that is independent of the main optical path.
In the QuantERA project QURAMAN (Quantum Raman) are we aiming for a combination of breakthroughs and improvements of existing components and already existing setups for building a commercial quantum Raman microscope. By combining the project partners’ expertise and skills in quantum optics, nonlinear optics, Raman spectroscopy and medical device design we will develop the next-generation Raman microscope for bio-imaging with quantum-enhanced sensitivity. The background knowledge and idea behind the QuRAMAN project is described in our recent publications (Optica 7, 470-475 (2020)). Where we have demonstrated that the use of continuous wave (CW) squeezed light can improve the SNR of weak Raman signals. However, to beat the performance of state-of-the-art SRS microscopes by means of squeezed light, one must employ amplitude squeezed picosecond pulses in a strongly focusing configuration (using an objective with a numerical aperture above unity). This will enable the imaging of weak Raman features and will push the Raman technology beyond the state of the art by applying pulsed amplitude squeezed light for signal enhancement.
It is challenging for stereolithography systems to print submicron features without two-photon lasers. For the first time, we implement an HD-DVD optical pickup unit (OPU) for building a customized stereolithography 3D printer. The OPU equips a 405 nm single-photon laser and an objective lens with a numerical aperture of 0.65. This has a focal laser spot diameter of 430 nm (1/e2) and can thereby, achieve submicron scale features photopolymerization. Moreover, the OPU embeds astigmatic optical path and voice coil motor which can be used for closed-loop printing alignment and this increases printing stability significantly. The OPU 3D printing system integrates an XYZ linear stage, providing nanoscale positioning resolution and macroscale printing area (c.a. 50 X 50 X 25 mm). A commercial photo-resin is utilized for the assessment of the system performance. The OPU printer crosslinks structures ranging from tens of microns down to submicron scale by tuning the printing parameters (laser intensity, printing speed, and photo-resin thickness). After optimization of the system, the OPU printer achieved the highest printing resolution of 210 nm which is beyond conventional stereolithography systems. Furthermore, several microstructures have been printed for verifying multiple layer printing performance. In conclusion, the mass-produced, low-cost and compact size OPU can not only dramatically simplify the stereolithography 3D printer design, but also achieve submicron printing performance.
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