Dynamically controlled light delivery over large brain volumes through tapered optical fibers

ABSTRACTOptogenetics promises spatiotemporal precise control of neural processes using light. However, the spatial extent of illumination within the brain is difficult to control and cannot be adjusted using standard fiber optics. We demonstrate that optical fibers with tapered tips can be used to illuminate either large brain volumes or dynamically selectable subregions. Remotely adjusting the light input angle to the fiber varies the light-emitting portion of the taper over several millimeters without movement of the implant. We use this mode to activate dorsal versus ventral striatum of individual mice and reveal different effects of each manipulation on motor behavior. Conversely injecting light over the full numerical aperture of the fiber results in light emission from the entire taper surface, achieving broader and more efficient optogenetic activation of neurons when compared to the standard flat-faced fiber stimulation. Thus, tapered fibers permit focal or broad illumination that can be precisely and dynamically matched to experimental needs.

Download Full-text

Shaping Beam Profiles Using Plastic Optical Fiber Tapers with Application to Ice Sensors

Sensors ◽

10.3390/s20092503 ◽

2020 ◽

Vol 20 (9) ◽

pp. 2503

Author(s):

Kostas Amoiropoulos ◽

Georgia Kioselaki ◽

Nikolaos Kourkoumelis ◽

Aris Ikiades

Keyword(s):

Fiber Optics ◽

Optical Fibers ◽

Laser Cooling ◽

Detection Efficiency ◽

Numerical Aperture ◽

Beam Profile ◽

Hollow Beam ◽

Enhanced Sensitivity ◽

Surface Irregularities ◽

Plastic Optical Fibers

Using either bulk or fiber optics the profile of laser beams can be altered from Gaussian to top-hat or hollow beams allowing enhanced performance in applications like laser cooling, optical trapping, and fiber sensing. Here, we report a method based on multimode Plastic Optical Fibers (POF) long-tapers, to tweak the beam profile from near Gaussian to a hollow beam, by generating surface irregularities on the conical sections of the taper with a heat-and-pull technique. Furthermore, a cutback technique applied on long tapers expanded the output beam profile by more than twice the numerical aperture (NA) of the fiber. The enhanced sensitivity and detection efficiency of the extended profile was tested on a fiber optical ice sensor related to aviation safety.

Download Full-text

Light-Emitting Textiles: Device Architectures, Working Principles, and Applications

Micromachines ◽

10.3390/mi12060652 ◽

2021 ◽

Vol 12 (6) ◽

pp. 652

Author(s):

Marco Cinquino ◽

Carmela Tania Prontera ◽

Marco Pugliese ◽

Roberto Giannuzzi ◽

Daniela Taurino ◽

...

Keyword(s):

Optical Fibers ◽

Light Emission ◽

Light Therapy ◽

Organic Leds ◽

Electrochemical Cells ◽

Electronic Components ◽

Electroluminescent Devices ◽

Light Emitting ◽

Polymer Optical Fibers ◽

Critical Aspects

E-textiles represent an emerging technology aiming toward the development of fabric with augmented functionalities, enabling the integration of displays, sensors, and other electronic components into textiles. Healthcare, protective clothing, fashion, and sports are a few examples application areas of e-textiles. Light-emitting textiles can have different applications: sensing, fashion, visual communication, light therapy, etc. Light emission can be integrated with textiles in different ways: fabricating light-emitting fibers and planar light-emitting textiles or employing side-emitting polymer optical fibers (POFs) coupled with light-emitting diodes (LEDs). Different kinds of technology have been investigated: alternating current electroluminescent devices (ACELs), inorganic and organic LEDs, and light-emitting electrochemical cells (LECs). The different device working principles and architectures are discussed in this review, highlighting the most relevant aspects and the possible approaches for their integration with textiles. Regarding POFs, the methodology to obtain side emissions and the critical aspects for their integration into textiles are discussed in this review. The main applications of light-emitting fabrics are illustrated, demonstrating that LEDs, alone or coupled with POFs, represent the most robust technology. On the other hand, OLEDs (Organic LEDs) are very promising for the future of light-emitting fabrics, but some issues still need to be addressed.

Download Full-text

Source numerical aperture control for efficient light emission from notched side-lighting fiber optics

10.1117/12.559858 ◽

2004 ◽

Cited By ~ 3

Author(s):

Sheldon Sillyman ◽

Kenneth K. Li ◽

Seiji Inatsugu

Keyword(s):

Fiber Optics ◽

Light Emission ◽

Numerical Aperture ◽

Aperture Control

Download Full-text

Exploiting modal demultiplexing properties of tapered optical fibers for tailored optogenetic stimulation

10.1101/199273 ◽

2017 ◽

Author(s):

Marco Pisanello ◽

Filippo Pisano ◽

Leonardo Sileo ◽

Emanuela Maglie ◽

Elisa Bellistri ◽

...

Keyword(s):

Optical Fibers ◽

Neural Activity ◽

Propagation Constant ◽

Numerical Aperture ◽

Brain Regions ◽

Brain Volumes ◽

Light Delivery ◽

Multiple Wavelengths ◽

Active Segment ◽

Site Selective

AbstractOptogenetic control of neural activity in deep brain regions requires precise and flexible light delivery with non-invasive devices. To this end, Tapered Optical Fibers (TFs) represent a minimally-invasive tool that can deliver light over either large brain volumes or spatially confined subregions. This work links the emission properties of TFs with the modal content injected into the fiber, finding that the maximum transversal propagation constant (kt) and the total number of guided modes sustained by the waveguide are key parameters for engineering the mode demultiplexing properties of TFs. Intrinsic features of the optical fiber (numerical aperture and core/cladding diameter) define the optically active segment of the taper (up to ∼3mm), along which a linear relation between the propagating set of kt values and the emission position exists. These site-selective light-delivery properties are preserved at multiple wavelengths, further extending the range of applications expected for tapered fibers for optical control of neural activity.

Download Full-text

Effect of Laser Irradiation on Emissivity of Flame-Generated Nanooxides

Materials ◽

10.3390/ma14092303 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2303

Author(s):

Silvana De Iuliis ◽

Roberto Dondè ◽

Igor Altman

Keyword(s):

Laser Irradiation ◽

Light Emission ◽

Energy Gap ◽

Particle Temperature ◽

Electron Excitation ◽

Flame Spray ◽

Energy Bands ◽

Light Emitting ◽

Spectral Behavior ◽

The Difference

The application of pyrometry to retrieve particle temperature in particulate-generating flames strictly requires the knowledge of the spectral behavior of emissivity of light-emitting particles. Normally, this spectral behavior is considered time-independent. The current paper challenges this assumption and explains why the emissivity of oxide nanoparticles formed in flame can change with time. The suggested phenomenon is related to transitions of electrons between the valence and conduction energy bands in oxides that are wide-gap dielectrics. The emissivity change is particularly crucial for the interpretation of fast processes occurring during laser-induced experiments. In the present work, we compare the response of titania particles produced by a flame spray to the laser irradiation at two different excitation wavelengths. The difference in the temporal behavior of the corresponding light emission intensities is attributed to the different mechanisms of electron excitation during the laser pulse. Interband transitions that are possible only in the case of the laser photon energy exceeding the titania energy gap led to the increase of the electron density in the conduction band. Relaxation of those electrons back to the valence band is the origin of the observed emissivity drop after the UV laser irradiation.

Download Full-text

Recent advancements and perspectives on light management and high performance in perovskite light-emitting diodes

Nanophotonics ◽

10.1515/nanoph-2021-0033 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Shaoni Kar ◽

Nur Fadilah Jamaludin ◽

Natalia Yantara ◽

Subodh G. Mhaisalkar ◽

Wei Lin Leong

Keyword(s):

High Performance ◽

Light Propagation ◽

Light Emission ◽

Review Article ◽

Rapid Progress ◽

Light Emitting ◽

Materials Engineering ◽

Perovskite Materials ◽

Light Management ◽

Photon Recycling

Abstract Perovskite semiconductors have experienced meteoric rise in a variety of optoelectronic applications. With a strong foothold on photovoltaics, much focus now lies on their light emission applications. Rapid progress in materials engineering have led to the demonstration of external quantum efficiencies that surpass the previously established theoretical limits. However, there remains much scope to further optimize the light propagation inside the device stack through careful tailoring of the optical processes that take place at the bulk and interface levels. Photon recycling in the emitter material followed by efficient outcoupling can result in boosting external efficiencies up to 100%. In addition, the poor ambient and operational stability of these materials and devices restrict further commercialization efforts. With best operational lifetimes of only a few hours reported, there is a long way to go before perovskite LEDs can be perceived as reliable alternatives to more established technologies like organic or quantum dot-based LED devices. This review article starts with the discussions of the mechanism of luminescence in these perovskite materials and factors impacting it. It then looks at the possible routes to achieve efficient outcoupling through nanostructuring of the emitter and the substrate. Next, we analyse the instability issues of perovskite-based LEDs from a photophysical standpoint, taking into consideration the underlying phenomena pertaining to defects, and summarize recent advances in mitigating the same. Finally, we provide an outlook on the possible routes forward for the field and propose new avenues to maximally exploit the excellent light-emitting capabilities of this family of semiconductors.

Download Full-text

Tunable Light‐Emission Properties of Solution‐Processable N‐Heterocyclic Carbene Cyclometalated Gold(III) Complexes for Organic Light‐Emitting Diodes

Chemistry - A European Journal ◽

10.1002/chem.202100499 ◽

2021 ◽

Author(s):

Robert Malmberg ◽

Tobias Arx ◽

Monirul Hasan ◽

Olivier Blacque ◽

Atul Shukla ◽

...

Keyword(s):

Light Emitting Diodes ◽

Light Emission ◽

Organic Light Emitting Diodes ◽

Light Emitting ◽

Emission Properties ◽

Organic Light ◽

Solution Processable

Download Full-text

Non-linear light emission of inorganic protonic diodes, H+LEDs

Journal of Materials Chemistry C ◽

10.1039/d0tc05935h ◽

2021 ◽

Vol 9 (9) ◽

pp. 3052-3057

Author(s):

Jerzy J. Langer ◽

Ewelina Frąckowiak

Keyword(s):

Light Emission ◽

Stimulated Raman Scattering ◽

Light Emitting ◽

Light Emitting Devices ◽

Light Pulses ◽

Optical Effects ◽

Non Linear ◽

Intense Light ◽

Light Beams ◽

Intense Light Pulses

H+LEDs are light emitting devices based on a protonic p–n junction; now with no organic polymers. The unique are non-linear optical effects: collimated light beams and stimulated Raman scattering (SRS), observed while generating intense light pulses.

Download Full-text