Marc de Cea’s research while affiliated with Massachusetts Institute of Technology and other places

Optical phased arrays (OPAs) are a promising technology for the realization of fast and compact non-mechanical optical beam steering. While many experimental demonstrations of integrated OPAs exist in the literature, it is challenging to evaluate their suitability for real-world applications due to the lack of system-level performance requirements. Here, we derive such performance requirements for two of the most promising OPA applications - namely free space optical communications (FSOC) and light detection and ranging (LIDAR) - and show that traditional uniformly spaced OPA architectures likely cannot reach the required performance. In response, we propose the use of non-uniformly spaced OPAs, analyze its performance tradeoffs and show that in certain scenarios they can offer superior performance with decreased complexity.

We show that the use of colorimetric compounds in integrated optical refractometric sensors can enhance the response to the presence of analytes of interest by virtue of the Kramers-Konig relations.

We realize single-mode, waveguide-coupled, electrically driven silicon light emitting diodes in commercial, unmodified silicon photonics foundry processes and develop a model of both the electrical and optical behavior to understand the performance limitations. We measure a center wavelength of 1130 nm, a 90 nm 3 dB optical bandwidth, and 200 pW of optical power propagating in each direction. We show on-chip modulation and detection of the generated light using native resonant photodetectors integrated in the same chip. Our work unveils a new native light source available in silicon photonics processes, which can find applications ranging from device screening and fabrication quality assessment to imaging, refractive index sensing, or intra-chip communication.

A nanoscale on-chip light source with high intensity is desired for various applications in integrated photonics systems. However, it is challenging to realize such an emitter using materials and fabrication processes compatible with the standard integrated circuit technology. In this letter, we report an electrically driven Si light-emitting diode with sub-wavelength emission area fabricated in an open-foundry microelectronics complementary metal-oxide-semiconductor platform. The light-emitting diode emission spectrum is centered around 1100 nm and the emission area is smaller than 0.14 μm² (~∅400$\varnothing 400$ nm). This light-emitting diode has high spatial intensity of >50 mW/cm² which is comparable with state-of-the-art Si-based emitters with much larger emission areas. Due to sub-wavelength confinement, the emission exhibits a high degree of spatial coherence, which is demonstrated by incorporating the light-emitting diode into a compact lensless in-line holographic microscope. This centimeter-scale, all-silicon microscope utilizes a single emitter to simultaneously illuminate ~9.5 million pixels of a complementary metal-oxide-semiconductor imager.

Nanoscale, sub-wavelength size light-emitting diodes (LEDs) have attractive features including high spatial coherence, fast modulation, and high array density. Here we present digital holography and time-of-flight ranging using nanoscale CMOS LEDs.

Lensless holography promises compact, low-cost optical apparatus designs with similar performance to traditional imaging setups. Here, we propose the use of a silicon micro-LED fabricated in a commercial CMOS microelectronics process as the illumination source in a lensless holographic microscope. Its small emission area ( {\lt}4\,\unicode{x00B5}{\rm m}^2 < 4 µ m 2 ) ensures high spatial coherence without the need for a pinhole and results in a large NA setup, circumventing the limits to the source-to-sample distance encountered by conventional lensless holography apparatus. The scene is reconstructed using an untrained deep neural network architecture that simultaneously performs spectral recovery by learning from the given single experimental diffraction intensity. We envision this synergetic combination of CMOS micro-LEDs and the machine learning framework can be used in other computational imaging applications, such as a compact microscope for live-cell tracking or spectroscopic imaging of biological materials.

A nanoscale on-chip light source with high intensity is desired for various applications in integrated photonics systems. However, it is challenging to realize such an emitter using materials and fabrication processes compatible with the standard integrated circuit technology. In this letter, we report an electrically driven Si light-emitting diode (LED) with sub-wavelength emission area fabricated in an open-foundry microelectronics CMOS platform. The LED emission spectrum is centered around 1100 nm and the emission area is smaller than 0.14 μm<2>( ≈ 400 nm diameter). This LED has high spatial intensity of > 50 mW/cm<2> which is comparable with the state-of-the-art Si-based emitters with much larger emission areas. Due to sub-wavelength confinement, the emission exhibits a high degree of spatial coherence, which is demonstrated by incorporating the LED into a compact lensless in-line holographic microscope. This centimeter-scale, all-silicon microscope utilizes a single emitter to simultaneously illuminate ≈ 9.5 million pixels of a CMOS imager.

We demonstrate electrically driven, native silicon waveguide LEDs in silicon photonic fabrication processes. The emission wavelength is centered at 1130 nm and the optical power is > 100 pW, allowing for on-chip detection of the generated light.