The use of nanometer-sized probes for single-cell studies is presented by Gary Shambat of Adamant Technologies (USA) in, "Single-cell Photonic Nanocavity Probes." This work, conducted by Shambat at Stanford University in Jelena Vukovic's lab, seeks to extend traditional nanoprobe work by being able to insert a nanobeam into a single cell without damaging the cell. By functionalizing the beam, the team enables single-cell studies, essentially taking the lab to the biological system instead of extracting the biological system for study in a lab.
The probe consists of a nanobeam optical cavity resulting from the tapering a GaAs device containing InAs quantum dots and coupled to an optical fiber to enable handling. The team demonstrated the ability to insert and retract the beam from PC3 cells (prostate cancer cells) in a reversible and elastic fashion.
Using this technique allowed a study of the optical properties of the cell. Cell viability in this initial work was 75%. Future work includes in vitro protein sensing and adapting chemistries for studies of intracellular targets such as proteins, all of which may find applications in fields such as drug screening.
We model conduction and free-carrier injection in laterally doped GaAs p-i-n diodes formed in one and twodimensional photonic crystal (PC) nanocavities. Finite element simulations show that the lateral geometry exhibits high electrical conductivity for a wide range of PC parameters and allows for precise control over current flow, enabling efficient carrier injection despite fast surface recombination. Thermal simulations indicate that the temperature increase during steady-state operation is only 3.3K in nanobeams and 0.29K in L3 defect nanocavities. The results affirm the suitability of lateral doping in PC devices and indicate criteria for further design optimization.
A fabrication procedure for electrically pumping photonic crystal membrane devices using a lateral p-i-n junction has
been developed and is described in this work. The lateral junction is optimized to efficiently inject current into a
photonic crystal nanocavity. We have demonstrated electrically pumped lasing by using the lateral junction to pump a
quantum dot photonic crystal nanocavity laser. Continuous wave lasing is observed at temperatures up to 150K, and a
threshold of 181nA at 50K is demonstrated - the lowest threshold ever demonstrated in an electrically pumped laser. At
room temperature we find that our devices do not lase, but behave as single-mode light-emitting diodes (LEDs). When
directly modulated, we find that our LEDs have an ultrafast electrical response up to 10 GHz corresponding to less than
1 fJ/bit energy operation. In addition, we have demonstrated electrical pumping of photonic crystal nanobeam LEDs, and
have built fiber taper coupled electro-optic modulators in the same lateral junction platform.
A fabrication procedure for electrically pumping photonic crystal membrane devices using a lateral p-i-n junction has
been developed and is described in this work. The lateral junction is optimized to efficiently inject current into a
photonic crystal nanocavity. We have demonstrated electrically pumped lasing by using the lateral junction to pump a
quantum dot photonic crystal nanocavity laser. Continuous wave lasing is observed at temperatures up to 150K, and a
threshold of 181nA at 50K is demonstrated - the lowest threshold ever demonstrated in an electrically pumped laser.
We have demonstrated electrical pumping of photonic crystal nanobeam light emitting diodes, and observe linewidth
narrowing at room temperature.
We demonstrate photonic interfaces between infrared and visible wavelength ranges by employing enhanced nonlinear
frequency conversion in photonic crystal cavities in GaP or GaAs. We first show resonantly enhanced
second harmonic and sum frequency generation in GaP photonic crystal cavities. We then integrate these nonlinear
frequency conversion elements with a single InAs quantum dot to produce a fast single photon source
that is optically triggered at telecommunications wavelength. These frequency conversion techniques are critical
for applications including light sources at wavelengths that are difficult to access with existing lasers, IR
upconversion-based detectors, and photonic quantum interfaces between the fiber-optic networks and quantum
emitters.
Many applications require the ability to image a scene in several different narrow spectral bands simultaneously. Conventional multi-layer dielectric filters require control of film thickness to change the resonant wavelength. This makes it difficult to fabricate a mosaic of multiple narrow spectral band transmission filters monolithically. We adjusted the spectral transmission of a multi-layer dielectric filter by drilling a periodic array of subwavelength holes through the stack. Multi-band photonic crystal filters were modeled and optimized for a specific case of filtering six optical bands on a single substrate. Numerical simulations showed that there exists a particular air hole periodicity which maximizes the minimum hole diameter. Specifically for a stack of SiO2 and Si3N4 with the set of filtered wavelengths (nm): 560, 576, 600, 630, 650, and 660, the optimal hole periodicity was 282 nm. This resulted in a minimum hole diameter of 90 nm and a maximum diameter of 226 nm. Realistic fabrication tolerances were considered such as dielectric layer thickness and refractive index fluctuations, as well as vertical air hole taper. Our results provide a reproducible methodology for similar multi-band monolithic filters in either the optical or infrared regimes.
Many applications require the ability to image a scene in several different narrow spectral bands simultaneously.
Absorption filters commonly used to generate RGB color filters do not have the flexibility and narrow band filtering
ability. Conventional multi-layer dielectric filters require control of film thickness to change the resonant wavelength.
This makes it difficult to fabricate a mosaic of multiple narrow spectral band transmission filters monolithically. This
paper extends the previous work in adjusting spectral transmission of a multi-layer dielectric filter by drilling a periodic
array of subwavelength holes through the stack. Multi-band photonic crystal filters were modeled and optimized for a
specific case of filtering six optical bands on a single substrate. Numerical simulations showed that there exists a
particular air hole periodicity which maximizes the minimum hole diameter. Specifically for a stack of SiO2 and Si3N4 with the set of filtered wavelengths (nm): 560, 576, 600, 630, 650, and 660, the optimal hole periodicity was 282 nm. This resulted in a minimum hole diameter of 90 nm and a maximum diameter of 226 nm. Realistic fabrication tolerances
were considered such as dielectric layer thickness and refractive index fluctuations, as well as vertical air hole taper. It
was found that individual layer fluctuations have a minor impact on filter performance, whereas hole taper produces a
large peak shift. The results in this paper provide a reproducible methodology for similar multi-band monolithic filters in
either the optical or infrared regimes.
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