We report on the design, fabrication, and characterization of the first photonic crystal (PhC)-based red multiple-quantum-well (MQW) color converters fully optimized for augmented reality (AR) microdisplays through a quasi-3D light harnessing principle. This principle leverages an aluminum (Al) bottom reflector and a silicon dioxide (SiO2) gap to harness the bottom-emitted light, along with copper (Cu) lateral mirrors and a silicon nitride (SiN) phase-matcher for Bloch-mode replication. These structures were designed using 3D-FDTD simulations. As a proof-of-principle, we fabricated corresponding devices that exhibit promising characteristics, including record light extraction efficiencies over 40% for 4µm pixels and emission patterns with high directionality. Time-resolved photoluminescence (TRPL) analyses, along with a four-wave intensity model developed in this work, indicate that there is still room for improvement. We believe that the guidelines established in this study could pave the way for the use of MQW color converters in the next generation of very bright, high-resolution RGB microdisplays for AR glasses and beyond.
While state-of-the-art RGB microdisplays rely on quantum-dot color-converters (CC), the next generation of very bright and high-resolution AR microdisplays could be based on MQW CC due to their better photostability and higher blue-light absorption. However, their practical implementation is still hindered by their low light extraction efficiency (LEE), their Lambertian-like emission patterns, as well as the challenges related to their integration on on-Silicon blue µLED arrays (transfer and pixelization). In this work, we use photonic-crystals (PhCs) as light extractors and investigate all the challenges related to the design, integration & fabrication as well as testing of novel MQW based CC.
Historically LYNRED (created from the merger of SOFRADIR and ULIS in 2019) has used amorphous silicon materials (“a-Si”) as thermistor materials for its uncooled microbolometer products. If a-Si materials present several advantages that made the success of LYNRED’s products (easy to use and integrate in thermal camera), their intrinsic bolometric performances (i.e. TCR and 1/f noise) are still lower than the commonly used oxides thermistors[1] (i.e. VOx[2] and TiOx[3]). In order to stay in a leading position regarding sensor performances without any trade-off, LYNRED, with the support of its historical R&D partner the CEA-LETI, developed new materials. This strategy has led to new cutting edge products. At the end of 2020 a new 17 µm pixel pitch product (Pico640s[4]), with one of the highest sensor performance reported on the market (typical thermal sensitivity of 25 mK (f/1, 300K, 30Hz)), has been introduced in our product portfolio. We also launched our state of the art 12 µm product range with performances equivalent to our current 17µm product range. More generally, these developments open up new opportunities toward smaller pixel pitch. The symposium presentation and the associated article will present how we have increased the "Signal to Noise Ratio" (SNR) of our products while keeping all the elements which have been our hallmark. Special attention will be paid to NETD, stability of product characteristics during operation and manufacturing excellence. All these features were obtained only by hardware (at the pixel level) improvements without the need to use sophisticated algorithms or specific ROIC functions, in the spirit of LYNRED’s FPA products.
Hybrid III-V/Si laser integration on silicon photonic platform has been demonstrated several time using III-V direct bonding on top of patterned silicon [1-3]. Most of these former works have been achieved using small wafer diameter III-V fabrication line for post bonding process steps. The expected low-cost added value of silicon photonics cannot be sustained with such integration scheme. More recently, we present III-V laser integration with a CMOS compatible process using wafer to wafer bonding and 1 level of contact [4]. In this paper, we present the technological progresses on a 200mm fully CMOS compatible hybrid III-V/Si laser technology. We introduced an improved backend of line for hybrid lasers with 2 interconnection levels, W-plugs and fully planarized process offering a state of the art access resistance and a homogeneous current density distribution over the gain material. Second, in order to optimize the use of the costly III-V material and enable the laser large scale integration on silicon we present fabrication process with die to wafer molecular bonding with high bonding yield at wafer scale. These process features will be detailed and the impact of laser performances will be presented. Finally, the scalability towards 300mm for the overall platform will be discussed.
Silicon photonic platforms are becoming more and more mature with competitive devices suitable for increasing needs of HPC (High Performance Computing) systems and datacenters. Compared to bulk III-V technologies, Si photonic technologies are suffering from the lack of integrated light source. Several works have been done in the past years to integrate laser on silicon using III-V direct bonding on top of patterned silicon. These demonstrations were using a CMOS compatible process for the silicon part but all the process steps following the introduction of the III-V material were done with small wafer diameter III-V fabrication lines. With such integrations, the cost advantage of silicon photonics based on the use of CMOS platforms and large wafer format is no more valid.
In this paper we present the integration of a hybrid III-V/Si laser using a fully CMOS compatible 200mm technology. The laser is integrated in a mature photonic platform. The additional process modules required for this integration will be deeply described. These modules are localized silicon thickening using damascene process, Bragg reflector patterning with DUV lithography, III-V patterning and ohmic contact formation with no lift-off and without noble metal. This integration is compatible with a multi metal levels planar BEOL, mandatory for photonic circuit design.
The first DFB lasers fabricated with this new platform are operating at 1310nm with a threshold current around 60mA, a SMSR larger than 45dB and more than 1.5mW optical power in the output waveguide. New laser designs, specifically adapted for this new process, will be introduced and fabricated.
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