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Materials Science in Additive Manufacturing Additive manufacturing of active optics

can be tailored to emit light in highly specific, confined UV to NIR range. Figure 2B demonstrates UCNP‑based
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geometries, facilitating the illumination of narrow or new wavelength generation for display. Furthermore, as
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deep biological structures without introducing excessive illustrated in Figure 2C, the design of optical cavities, such
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heat or noise (Figure 1C, and D). Moreover, the angular as micro-wires, micro-plates, and micro-rings, significantly
distribution of emitted light plays a crucial role in linear enhances the optical performance of these materials,
and non-linear imaging spectroscopy (Figure 1E and F). leading to efficient micro-lasing. 25,26
Controlling this property allows for fine-tuning of the
angular resolution and the efficiency of light-matter 2.2. Active directional control
interaction, which is essential for high-precision metrology Active steering of emitted light plays a pivotal role in
and the inspection of semiconductor and flat-panel structured illumination microscopy (SIM), optical
displays. In these applications, additive manufacturing tweezers, and holographic 3D display systems. Techniques
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technologies such as two‑photon polymerization (2PP) such as SIM use structured beams with varying patterns to
provide the versatility needed to produce complex light- enhance resolution beyond the diffraction limit, enabling
emitting geometries that precisely control these beam super-resolution imaging. By controlling the emission
properties. 5 direction during fluorescence processes, it is possible to
Overall, the beam control requirements for active 3D reduce out-of-focus light and increase image clarity. This
optical structures are fundamental to their performance in approach is especially valuable in microscopy applications
demanding applications. The integration of advanced light- where high resolution and contrast are paramount. 27
emitting materials and the precision offered by additive Conventionally, photoluminescence from QDs is
manufacturing enable unprecedented control over these omnidirectional and exhibits limited spatial coherence,
beam properties, opening up new possibilities in photonics making it challenging to achieve directional control.
and optical measurement. 3,4 However, recent advancements in QD‑hydrogel integrated
gratings have enabled switchable unidirectional emission,
2.1. Active wavelength control allowing for more precise light path optimization in
Control over the emission wavelength is crucial for complex optical systems (Figure 3A). This technology can
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enhancing resolution, contrast, and signal-to-noise ratio in be used to optimize beam paths in SIM setups, improving
imaging, spectroscopy, microscopy, and communication image quality and resolution.
systems. Shorter wavelengths offer higher spatial In optical tweezers, highly focused laser beams trap and
resolution but have limited penetration depth, while longer manipulate small particles, requiring precise directional
wavelengths provide deeper tissue penetration at the control for accurate positioning and orientation
cost of reduced resolution. In cell imaging, wavelength (Figure 3B). This technique has broad applications
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tuning is essential for selective visualization of specific in biological sciences, nanotechnology, and ultracold
structures tagged with fluorophores, enabling the study matter physics. Figure 3C illustrates holographic display
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of dynamic cellular processes. Spectroscopy techniques, systems, where active directional control technologies help
such as Raman and infrared spectroscopy, rely on precise overcome limitations in viewing angle and color fidelity,
wavelength control to identify molecular structures and enhancing the performance of spatial light modulator
chemical bonds by detecting specific vibrational modes. 5 (SLM) and other components for 3D display applications. 30
Active wavelength control can be achieved by employing
various materials, such as organic/inorganic compounds, 2.3. Span angle control
QDs, up‑conversion nanoparticles (UCNPs), and non‑ Span angle control is essential in scanning systems such
linear optical media. Wavelengths can be tuned across a wide as light detection and ranging (LiDAR), microscopy, and
optical range from the ultraviolet (UV) to the near infrared display, where the ability to dynamically adjust the span
(NIR). QDs are well‑known for their tunable emission angle directly impacts field-of-view coverage and image
properties, which depend on their size and composition, resolution. Traditional beam-steering methods using
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making them ideal for multi-wavelength applications. passive components often result in power losses and slower
UCNPs, in particular, can absorb low‑energy NIR photons scanning speeds due to mechanical constraints, limiting
and emit higher-energy visible photons, taking advantage resolution, and response time. Active beam steering
of anti-Stokes shifts – a non-linear optical process. presents a promising alternative, offering enhanced
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Figure 2A illustrates the use of printable ink containing performance in these applications. Figure 4 shows the
graphene QDs, UCNPs, and Lead sulfide (PbS) QDs to active beam steering to realize span angle control in the
generate light sources with tunable wavelengths across the applications of LiDAR, microscopy, and display.

Volume 3 Issue 4 (2024) 4 doi: 10.36922/msam.5748