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1. Experimental Realization of an Extremely Low-cost Quadrature Optical Interferometer

   https://doi.org/10.1364/CLEO_AT.2023.JTh2A.95  

   Melody, Tanner M; Patel, Krishna H; Nguyen, Peter K; Smallwood, Christopher L (January 2023, Optica Publishing Group)

   We report on the construction and characterization of a quadrature-detected optical interferometer that can be assembled on a budget of less than US$500, and in which quadrature detection is achieved by means of polarization control. 

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2. Makerspace microfabrication of a stainless steel 3D microneedle electrode array (3D MEA) on a glass substrate for simultaneous optical and electrical probing of electrogenic cells

   https://doi.org/10.1039/d0ra06070d  

   Morales-Carvajal, Paola M.; Kundu, Avra; Didier, Charles M.; Hart, Cacie; Sommerhage, Frank; Rajaraman, Swaminathan (November 2020, RSC Advances)

   null (Ed.)

   Microfabrication and assembly of a Three-Dimensional Microneedle Electrode Array (3D MEA) based on a glass-stainless steel platform is demonstrated involving the utilization of non-traditional “Makerspace Microfabrication” techniques featuring cost-effective, rapid fabrication and an assorted biocompatible material palette. The stainless steel microneedle electrode array was realized by planar laser micromachining and out-of-plane transitioning to have a 3D configuration with perpendicular transition angles. The 3D MEA chip is bonded onto a glass die with metal traces routed to the periphery of the chip for electrical interfacing. Confined precision drop casting (CPDC) of PDMS is used to define an insulation layer and realize the 3D microelectrodes. The use of glass as a substrate offers optical clarity allowing for simultaneous optical and electrical probing of electrogenic cells. Additionally, an interconnect using 3D printing and conductive ink casting has been developed which allows metal traces on the glass chip to be transitioned to the bottomside of the device for interfacing with commercial data acquisition/analysis equipment. The 3D MEAs demonstrate an average impedance/phase of ∼13.3 kΩ/−12.1° at 1 kHz respectively, and an average 4.2 μV noise. Lastly, electrophysiological activity from an immortal cardiomyocyte cell line was recorded using the 3D MEA demonstrating end to end device development. 

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3. Oxide-Confined VCSELs for High-Speed Optical Interconnects

   Feng, M; Holonyak, N. Jr.; Wu, C.-H. (July 2018, IEEE journal of quantum electronics)

   The electrically pumped vertical-cavity surface- emitting laser (VCSEL) was first demonstrated with metal cavities by Iga (1979); however, the device threshold current was too high. Distributed Bragg reflector cavities proposed by Scifres and Burnham (1975) were adopted to improve the optical cavity loss. Yet, it was not a practical use until the discovery of the native oxide of AlGaAs and the insertion of quantum wells to provide simultaneous current and optical confinement in semiconductor laser by Holonyak and Dallesasse (1990). Later, the first “low- threshold” oxide-confined VCSEL was realized by Deppe (1994) and opened the door of commercial application for a gigabit energy-efficient optical links. At present, we demonstrated that the oxide-confined VCSELs have advanced error-free data trans- mission [bit-error rate (BER) ≤ 10−12]to 57 Gb/s at 25 °C and 50 Gb/s at 85 °C, and also demonstrated that the pre-leveled 16-quadrature amplitude modulation orthogonal frequency- division multiplexing data were achieved at 104 Gbit/s under back-to-back transmission with the received error vector mag- nitude, SNR, and BER of 17.3%, 15.2 dB, and 3.8 × 10−3, respectively. 

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4. Experimental demonstration of the near-quantum optimal receiver

   https://doi.org/10.1364/OSAC.409200  

   Jabir, M_V; Burenkov, I_A; Annafianto, N_Fajar_R; Battou, A.; Polyakov, S_V (November 2020, OSA Continuum)

   We implement the cyclic quantum receiver based on the theoretical proposal of Roy Bondurant and demonstrate experimentally below the shot-noise limit (SNL) discrimination of quadrature phase-shift keying signals (PSK). We also experimentally test the receiver generalized for longer communication alphabet lengths and coherent frequency shift keying (CFSK) encoding. Using off-the-shelf components, we obtain state discrimination error rates that are 3 dB and 4.6 dB below the SNLs of ideal classical receivers for quadrature PSK and CFSK encodings, respectively. The receiver unconditionally surpasses the SNL for M=8 PSK and CFSK. This receiver can be used for the simple and robust practical implementation of quantum-enhanced optical communication. 

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5. Assembly of multicomponent structures from hundreds of micron-scale building blocks using optical tweezers

   https://doi.org/10.1038/s41378-021-00272-z  

   Melzer, Jeffrey E.; McLeod, Euan (June 2021, Microsystems & Nanoengineering)

   Abstract The fabrication of three-dimensional (3D) microscale structures is critical for many applications, including strong and lightweight material development, medical device fabrication, microrobotics, and photonic applications. While 3D microfabrication has seen progress over the past decades, complex multicomponent integration with small or hierarchical feature sizes is still a challenge. In this study, an optical positioning and linking (OPAL) platform based on optical tweezers is used to precisely fabricate 3D microstructures from two types of micron-scale building blocks linked by biochemical interactions. A computer-controlled interface with rapid on-the-fly automated recalibration routines maintains accuracy even after placing many building blocks. OPAL achieves a 60-nm positional accuracy by optimizing the molecular functionalization and laser power. A two-component structure consisting of 448 1-µm building blocks is assembled, representing the largest number of building blocks used to date in 3D optical tweezer microassembly. Although optical tweezers have previously been used for microfabrication, those results were generally restricted to single-material structures composed of a relatively small number of larger-sized building blocks, with little discussion of critical process parameters. It is anticipated that OPAL will enable the assembly, augmentation, and repair of microstructures composed of specialty micro/nanomaterial building blocks to be used in new photonic, microfluidic, and biomedical devices. 

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