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Spatial coherence is one of the signature properties of traditional lasers. While spatial coherence allows laser emission to be focused to a small volume or collimated over long distances, it is also the cause of deleterious effects such as speckle which has limited the adoption of lasers in most imaging applications [1]. In this work, we show that random lasers have the unique ability to exhibit...
Diffusion is a statistical description of random walk of a classical particle, and the diffusion constant D0 is the only parameter in the diffusion equation. For light as well as for other kinds of waves, this is an approximation, because the interference of partial waves is ignored [1]. Such interference is essential to Anderson localization. Proper account of the interference effects in random samples...
Traditional grating based spectrometers rely on a one-to-one spectral-to-spatial mapping. However, this one-to-one mapping is not required as long as distinct spectral signals are mapped to unique spatial intensity distributions. A calibration step is required to record this complex spectral-to-spatial mapping, but after calibration, the input spectra can be reconstructed simply by measuring the intensity...
Spectrometers are widely used tools in chemical and biological sensing, material analysis, and light source characterization. The development of a high-resolution on-chip spectrometer could enable compact, low-cost spectroscopy for portable sensing as well as increasing lab-on-a-chip functionality. However, the spectral resolution of traditional grating-based spectrometers scales with the optical...
We present a simple and robust approach to achieve low-loss, high-speed speckle reduction using a colloidal dispersion. This approach is compact, low cost, requires no external power, and is compatible with commercially available lasers.
We demonstrate unidirectional evanescent coupling of lasing emission from a deformed microdisk to a waveguide. The clockwise and counter-clockwise propagating ray orbits are spatially separated by wave optics effects, enabling selective coupling.
We design and fabricate an on-chip spectrometer based on random arrays of scatterers. Multiple scattering of light increases the effective optical pathlength, allowing us to dramatically reduce the device size without sacrificing spectral resolution.
Speckle and related coherent artifacts limit the use of lasers for imaging, despite their potential advantages (i.e. brightness). We demonstrate speckle-free laser imaging using a random laser designed to produce spatially incoherent emission.
We demonstrate control of the spatial coherence of random laser emission by tuning the scattering strength and excitation volume. The optimized, spatially incoherent source is applied to full-field optical coherence tomography to mitigate crosstalk.
We propose a two-stage lasing device in which an electroluminescent Si nanocrystal (Si-nc) disk optically pumps a concentric Er:SiO2 toroid. We also present fabrication and characterization of an Er:SiO2 microdisk and demonstrate coupling of Si-nc emission to a concentric SiO2 ring.
Si-nc light emission, overcoming limitations of c-Si, is described by a rate equation formalism within the ADE-FDTD scheme. Following this scheme, we design a series of resonant devices which tune and enhance the Si-nc luminescence.
We demonstrate enhanced photoluminescence from silicon nanocrystals using a DBR microcavity. We also show a candidate electroluminescent device which can be embedded into a similar DBR cavity for enhancement.
In this paper, we present an electromagnetic analysis of ring-cavity-assisted amplified spontaneous emission in Er3+-doped SiO2 (Er:SiO2 ). A horizontal slot geometry, consisting of a low-index Er:SiO2 layer embedded between high-index a-Si layers, allows for a planar ring-cavity design which maintains high optical confinement in the active Er:SiO2 material. The simulations are performed within the...
We present the design of a 1D microcavity with an active silicon nanocrystal (Si-nc) region for enhanced photo- and electro-luminescence. Microcavity enhanced photoluminescence is realized experimentally and incorporation with a presented electroluminescent structure is discussed.
The electro-optic properties of InAs/GaAs quantum dots are studied in an external Mach-Zehnder Interferometer setup. The InAs/GaAs quantum dots are found to increase modulation relative to bulk GaAs and exhibit an electro-optic coefficient of 26pm/V.
The electro-optic properties of InAs/GaAs quantum dots are studied in an external Mach-Zehnder interferometer setup. The InAs/GaAs quantum dots are found to increase modulation relative to bulk GaAs and exhibit an electro-optic coefficient of 26 pm/V.
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