Mid-IR photonic integrated circuits

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On-chip mid-infrared photothermal spectroscopy using suspended silicon-on-insulator microring resonators

Mid-infrared spectroscopic techniques rely on the specific "fingerprint" absorption lines of molecules in the mid-infrared band to detect the presence and concentration of these molecules. Despite being very sensitive and selective, bulky and expensive equipment such as cooled mid-infrared detectors is required for conventional systems. In this paper, we demonstrate a miniature CMOS-compatible Silicon-on-Insulator (SOI) photothermal transducer for mid-infrared spectroscopy which can potentially be made in high volumes and at a low cost. The optical absorption of an analyte in the mid infrared wavelength range (3.25-3.6 mu m) is thermally transduced to an optical transmission change of a microring resonator through the thermo-optic effect in silicon. The photothermal signal is further enhanced by locally removing the silicon substrate beneath the transducer, hereby increasing the effective thermal isolation by a factor of 40. As a proof-of-concept, the absorption spectrum of a polymer that has been locally patterned in the annular region of the resonator was recovered using photothermal spectroscopy. The spectrum is in good agreement with a benchmark Fourier-transform infrared spectroscopy (FTIR) measurement. A normalized noise equivalent absorption coefficient (NNEA) of 7.6 X 10(-6) W/Hz(1/2) is estimated

Germanium-on-silicon mid-infrared waveguides and Mach-Zehnder interferometers

In this paper we describe Ge-on-Si waveguides and Mach-Zehnder interferometers operating in the 5.2 - 5.4 mu m wavelength range. 3dB/cm waveguide losses and Mach-Zehnder interferometers with 20dB extinction ratio are presented

Location Problems in Supply Chain Design: Concave Costs, Probabilistic Service Levels, and Omnichannel Distribution

Location of facilities such as plants, distribution centers in a supply chain plays critical role in efficient management of logistics activities. Real-life supply chains are generally large in size with multiple echelons, prone to disruptions and uncertainties, and constantly evolving to meet customer demands in a fast and reliable way. Therefore, it is quite challenging to identify these locations while balancing the trade-off between costs and service levels. In this thesis, we investigate three supply chain design problems addressing various issues that complicate the location of facilities in a supply chain. The first paper investigates a multilevel capacitated facility location problem. Such problems commonly arise in large scale production-distribution supply chains with plants at one echelon, and distribution centers / warehouse at another, and there is hierarchy of flow between facilities and to the end customers such as retail stores. The operating costs at facilities and transportation costs on arcs are assumed to be concave. The concave functions model economies of scale in operations (such as production, handling, transportation) performed at large scale and emission of green house gases from transportation activities. The mathematical model for our problem is nonlinear (concave) for which we present two formulations. The first formulation is a prevalent mixed-integer nonlinear program, and second is a purely nonlinear programming problem. Extensive computations are performed to measure the efficiency of two formulations, and managerial insights are provided to understand the behavior of the model under different scenarios of concavities. The second work focuses on e-commerce supply chains that have a common objective of providing fast and reliable deliveries of customers’ orders. The order delivery time primarily depends on the time taken to process the order at the facilities and travel time from facilities to customers. These two times are uncertain in practice, therefore, to capture the combined effect of both uncertainties, we introduce a mathematical model with a requirement that all customer orders should be delivered within a committed time with some probabilistic guarantee. The problem is formulated as a dynamic (multiperiod) capacitated facility location problem with modular capacities. The probabilistic service level constraints make the problem nonconvex. We present two linear binary programming reformulations, and develop an exact branch-and-cut algorithm utilizing the reformulations to solve large size instances. We also include sensitivity analysis to study the change in network configuration under various modeling parameters. An increase in online sales every year is driving many brick-and-mortar retailers to follow an omni-channel retailing approach that would integrate their online sales channel with store sales. Omnichannel retailing requires a considerable change in current practices. For instance, a retailer generally decides if there is a need of new distribution facilities, which stores should be used as fulfillment centers as well, where to keep safety stocks, from where to serve online demand, among others. To study these aspect, in the third paper, we propose a novel mathematical model for the design of omnichannel distribution network along with allocation of safety stock to the facilities. The original problem is nonlinear which can be reformulated as conic quadratic mixed integer programming problem. The problem is solved using a branch-and-cut solution algorithm. Further, we present several managerial insights related to fulfillment and safety stock decisions using a small example

Germanium-on-silicon planar concave grating wavelength (de)multiplexers in the mid-infrared

Mid-infrared wavelength (de)multiplexers based on planar concave gratings (PCGs) fabricated on a germanium-on-silicon waveguide platform are presented. PCGs with two different types of gratings (flat facet and distributed bragg reflectors) are analyzed for both transverse electric (TE) and transverse magnetic (TM) polarizations. The insertion loss and cross talk for flat facet PCGs are found to be -7.6/-6.4¿dB and 27/21¿dB for TE/TM polarization. For distributed bragg reflector PCGs the insertion loss and cross talk are found to be -4.9/-4.2¿dB and 22/23¿dB for TE/TM polarization

Analisis Factor Penyebab Angkutan Umum Perkotaan Tidak Berkembang

Pengembangan angkutan umum perkotaan penting dilakukan oleh pemerintah dalam rangka menekan persoalan perkotaan yang disebabkan oleh kondisi transportasi yang buruk. Responden ahli yang menjadi responden dalam penelitian ini terdiri dari aparatur pemerintah, akademiksi, konsultan dan tokoh masyarakat. Ada 10 pertanyaan utama yang diajukan untuk melihat pandangan mereka tentang kondisi angkutan umum perkotaan dan empat factor utama yang mempengaruhinya yaitu kebijakan, anggaran, persepsi tentang masyarakat dan persepsi tentang jenis angkutan umum yang sesuai dengan kota. Hasilnya menunjukkan bahwa factor P1 (-92%), P2 (-62%), P3 (-56%), P4 (-56%), P5 (-64%), P6 (-95,8%), P7 (-76%), P8 (+80%), P9 (+92%), P10 (bus 56%). Kesimpulannya adalah angkutan umum perkotaan mengalami kondisi belum baik disebabkan oleh adnaya permasalahan pada factor kebijakan dan pembiayaan. Sementara potensi pengguna diperkirakan besar dan jenis angkutan umum yang bisa dikembangkan adalah bus kot

Germanium-on-silicon mid-infrared arrayed waveguide grating multiplexers

In this letter, we describe the use of a germanium-on- silicon waveguide platform to realize an arrayed waveguide grating (AWG) operating in the 5 mu m wavelength range, which can be used as a wavelength multiplexer for mid-infrared (midIR) light engines or as the core element of a midIR spectrometer. Ge-on-Si waveguide losses in the range 2.5-3.5 dB/cm for TE polarized light and 3-4 dB/cm for TM polarized light in the 5.15-5.4 mu m wavelength range are reported. A 200 GHz channel spacing 5-channel AWG with an insertion loss/crosstalk of 2.5/3.1 dB and 20/16 dB for TE and TM polarization, respectively, is demonstrated