Arpit Khandelwal

Bio: Arpit Khandelwal is an academic researcher from Indian Institute of Technology, Jodhpur. The author has contributed to research in topics: Gyroscope & Semiconductor ring laser. The author has an hindex of 4, co-authored 22 publications receiving 57 citations. Previous affiliations of Arpit Khandelwal include Birla Institute of Technology and Science & International Institute of Information Technology, Hyderabad.

Semiconductor Ring Laser Gyroscopes Modeling Design and Critical Performance Limiting Parameters

Abstract: Ring laser gyroscopes (RLG) are optical inertial rotation sensors used to measure the rate and direction of rotation. With the help of accelerometers, they provide accurate information about the position and orientation of an object. Their sensitivity depends upon the intended application: military navigation requires gyros with sensitivity of 0.01-0.1 deg/h while automobiles and handheld application need sensitivity of 1-10 deg/h. As the sensitivity of gyro is directly proportional to its size, the high performance military applications are dominated by the bulky He-Ne RLG. Over the past few decades, strong theoretical research backed up by advanced fabrication technologies have improved the performance of He-Ne RLG significantly. In the era of on-chip integrated optical devices, large size and high power requirement of He-Ne RLG limits its applications. This is where Semiconductor RLG (SRLG) provides a viable alternative. SRLG is a compact, low cost and low power inertial rotation sensor working on the principle of Sagnac effect. It offers the promise of fabricating the complete gyro system on a single Photonic Integrated Circuit (PIC). Many implementations of bulk-optic and integrated SRLG have been proposed, but their reported performance has been highly inferior to He-Ne RLG. While bulk-optic SRLG has shown sensitivity of 103 deg/h, the reported sensitivity of integrated SRLG has been 108 deg/h, which is unacceptable even for low performance applications like automobiles. While the poor performance of integrated SRLG has been attributed to phenomena like mode coupling and gain competition, a detailed performance analysis has not yet been reported. Hence, critical performance limiting parameters could not be identified and feasible practical solutions to enhance the performance could not be proposed. This has inhibited the development of SRLG technology towards high performance applications. In this thesis, SRLG has been mathematically modeled using rate equations of counter-traveling electric fields inside the gain medium and the resonant cavity. The Sagnac beat signal obtained by simulating the model is verified by rotating the experimental setup of the gyro. The sensitivity, which is found to be limited by locking of the counter-traveling fields, is enhanced by proposing few novel designs and biasing techniques. Although these techniques improve the sensitivity of SRLG, the overall performance is still very poor compared to the military navigation standards. In order to identify the critical performance limiting parameters and phenomena, every metric of SRLG such as quantum limit, angle random walk, scale factor stability, null shift and lock-in threshold have been thoroughly modeled in terms of material, geometry and environmental parameters. Moreover, effects of nonlinearities such as spatial hole burning, mode coupling, gain saturation etc. on the SRLG sensitivity have been evalu-

Bipolar resistive switching properties of TiO x /graphene oxide doped PVP based bilayer ReRAM

Abstract: In this paper, firstly, some recently explored promising materials and processes for resistive random access memory (ReRAM) devices with bipolar switching mechanism along with their performance are discussed. Further, resistive switching behaviour of TiO x /graphene oxide (GO):poly(4-vinylphenol) (PVP) based bilayer in ReRAM devices is demonstrated. It was found that bipolar resistive switching behaviour is significantly enhanced by embedding 2D material such as GO in the organic polymer acting as switching layer. ReRAM devices with Ag/PVP:GO/TiO x /fluorine doped tin oxide (FTO) structure exhibited high ON/OFF current ratio (>103), low voltage operation, and high retention time. Bipolar resistive switching from these engineered active layers will have great potential for future large area and sustainable electronics.

Analyzing phase-amplitude coupling effects on the dynamics of semiconductor ring laser gyroscope

Abstract: The effects of phase-amplitude interactions on the linearity of semiconductor ring laser gyro output is evaluated. Response of gyro output to the variations in several semiconductor gain medium parameters is studied with a view of performance enhancement through parameter optimization.

Highly sensitive ring resonator based refractive index sensor for label free biosensing applications

Abstract: Ring resonator based label free refractive index biosensor is proposed for detecting glucose and hemoglobin concentrations. To improve device sensitivity and Q factor, various parameters of ring resonator are optimized. The designed ring resonator sensor can sense hemoglobin and glucose concentrations with a high sensitivity of 424 nm/RIU and Q factor of 802.

On the Mechanistic Origins of Toughness in Bone

Abstract: One of the most intriguing protein materials found in nature is bone, a material composed of assemblies of tropocollagen molecules and tiny hydroxyapatite mineral crystals that form an extremely tough, yet lightweight, adaptive and multifunctional material. Bone has evolved to provide structural support to organisms, and therefore its mechanical properties are of great physiological relevance. In this article, we review the structure and properties of bone, focusing on mechanical deformation and fracture behavior from the perspective of the multidimensional hierarchical nature of its structure. In fact, bone derives its resistance to fracture with a multitude of deformation and toughening mechanisms at many size scales ranging from the nanoscale structure of its protein molecules to the macroscopic physiological scale.

Recent advances in miniaturized optical gyroscopes

Abstract: Low-cost chip-scale optoelectronic gyroscopes having a resolution ≤ 10 °/h and a good reliability also in harsh environments could have a strong impact on the medium/high performance gyro market, which is currently dominated by well-established bulk optical angular velocity sensors. The R&D activity aiming at the demonstration of those miniaturized sensors is crucial for aerospace/defense industry, and thus it is attracting an increasing research effort and notably funds. In this paper the recent technological advances on the compact optoelectronic gyroscopes with low weight and high energy saving are reviewed. Attention is paid to both the so-called gyroscope-on-a-chip, which is a novel sensor, at the infantile stage, whose optical components are monolithically integrated on a single indium phosphide chip, and to a new ultra-high Q ring resonator for gyro applications with a configuration including a 1D photonic crystal in the resonant path. The emerging field of the gyros based on passive ring cavities, which have already shown performance comparable with that of optical fiber gyros, is also discussed.

Laser gyro at quantum limit

Abstract: We show that a certain fundamental limit applies to the accuracy of all optical rotation sensors which use laser light as a probe. We derive this fundamental rotation-rate uncertainty from the Heisenberg uncertainty relations and Glauber's minimum uncertainty states. The same relationship is obtained from a spontaneous-emission noise formulation. We present experimental data on a (nondithered) four-frequency ring laser gyroscope for which this limit is attained.