Massachusetts Institute of Technology

Bo Zhen

Marin Soljacic

Ofer Shapira

Chia Wei Hsu

Wenjun Qiu

John Dimitris Joannopoulos

Song-Liang Chua

Jeongwon Lee

Yi Yang

Ido Kaminer

Nicholas H Rivera

Emma Anquillare

Marin Soljaic

Ultra-thin conductors are employed to generate plasmon fields near the surface of the conductors. Emitters, such as atoms, molecules, quantum dots, or quantum wells, in the plasmon fields can emit and absorb light via transitions that are otherwise forbidden in the absence of the plasmon fields. Applications using these forbidden transitions include spectroscopy, organic light sources, and broadband light generation. For example, in a spectroscopic platform, an emitter is disposed in the plasmon fields to excite electronic transitions that are otherwise unexcitable. In organic light sources, plasmon fields quench excited triplet states, allowing fast singlet decay with the emission of light. In broadband light generation, strong two-plasmon spontaneous emission of emitters near ultrathin conductors is employed to produce a broad spectrum of light.

Apparatus and methods for spectroscopy and broadband light emission using two-dimensional plasmon fields

A transparent display includes nanoparticles having wavelength-selective scattering (e.g., resonant scattering) to preferentially scatter light at one or more discrete wavelengths so as to create images. The nanoparticles transmit light at other wavelengths to maintain a high transparency of the display. The nanoparticles are disposed in proximity to a thin film, which can enhance the scattering the process by reflecting light back to the nanoparticles for re-scattering or increasing the quality factor of the resonant scattering.

Transparent displays with scattering nanoparticles and thin films for enhanced scattering

Transparent displays enable many useful applications, including heads-up displays for cars and aircraft as well as displays on eyeglasses and glass windows. Unfortunately, transparent displays made of organic light-emitting diodes are typically expensive and opaque. Heads-up displays often require fixed light sources and have limited viewing angles. And transparent displays that use frequency conversion are typically energy inefficient. Conversely, the present transparent displays operate by scattering visible light from resonant nanoparticles with narrowband scattering cross sections and small absorption cross sections. More specifically, projecting an image onto a transparent screen doped with nanoparticles that selectively scatter light at the image wavelength(s) yields an image on the screen visible to an observer. Because the nanoparticles scatter light at only certain wavelengths, the screen is practically transparent under ambient light. Exemplary transparent scattering displays can be simple, inexpensive, scalable to large sizes, viewable over wide angular ranges, energy efficient, and transparent simultaneously.

Methods and apparatus for transparent display using scattering nanoparticles

Disclosed herein are transparent color displays with nanoparticles made with nonlinear materials and/or designed to exhibit optical resonances. These nanoparticles are embedded in or hosted on a transparent substrate, such as a flexible piece of clear plastic or acrylic. Illuminating the nanoparticles with invisible light (e.g., infrared or ultraviolet light) causes them to emit visible light. For example, a rare-earth doped nanoparticle may emit visible light when illuminated simultaneoulsy with a first infrared beam at a first wavelength &#x3bb;and a second infrared beam at a second wavelength &#x3bb;. And a frequency-doubling nanoparticle may emit visible light when illuminated with a single infrared beam at the nanoparticle's resonant frequency. Selectively addressing these nanoparticles with appropiately selected pump beams yields visible light emitted from the nanoparticles hosted by the transparent substrate in a desired pattern.

Methods and apparatus for transparent display using up-converting nanoparticles

Disclosed herein is a system for stimulating emission from at least one an emitter, such as a quantum dot or organic molecule, on the surface of a photonic crystal comprising a patterned dielectric substrate. Embodiments of this system include a laser or other source that illuminates the emitter and the photonic crystal, which is characterized by an energy band structure exhibiting a Fano resonance, from a first angle so as to stimulate the emission from the emitter at a second angle. The coupling between the photonic crystal and the emitter may result in spectral and angular enhancement of the emission through excitation and extraction enhancement. These enhancement mechanisms also reduce the emitter's lasing threshold. For instance, these enhancement mechanisms enable lasing of a 100 nm thick layer of diluted organic molecules solution with reduced threshold intensity. This reduction in lasing threshold enables more efficient organic light emitting devices and more sensitive molecular sensing.

Excitation enhancement and extraction enhancement with photonic crystals

An organic dye laser produces a continuous-wave (cw) output without any moving parts (e.g., without using flowing dye streams or spinning discs of solid-state dye media to prevent photobleaching) and with a pump beam that is stationary with respect to the organic dye medium. The laser's resonant cavity, organic dye medium, and pump beam are configured to excite a lasing transition over a time scale longer than the associated decay lifetimes in the organic dye medium without photobleaching the organic dye medium. Because the organic dye medium does not photobleach when operating in this manner, it may be pumped continuously so as to emit a cw output beam. In some examples, operation in this manner lowers the lasing threshold (e.g., to only a few Watts per square centimeter), thereby facilitating electrical pumping for cw operation.

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Cambridge, MA, United States of America

Bo Zhen