Tuning of 2D rod-type photonic crystal cavity for optical modulation and impact sensing

We propose a novel way of mechanical perturbation of photonic crystal cavities for on-chip applications. We utilize the equivalence of the 2D photonic crystals with perfect electric conductor (PEC) boundary conditions to the infinite height 3D counterparts for rod type photonic crystals. Designed structures are sandwiched with PEC boundaries above and below and the perturbation of the cavity structures is demonstrated by changing the height of PEC boundary. Once a defect filled with air is introduced, the metallic boundary conditions is disturbed and the effective mode permittivity changes leading to a tuned optical properties of the structures. Devices utilizing this perturbation are designed for telecom wavelengths and PEC boundaries are replaced by gold plates during implementation. For 10 nm gold plate displacement, two different cavity structures showed a 21.5 nm and 26 nm shift in the resonant wavelength. Optical modulation with a 1.3 MHz maximum modulation frequency with a maximum power consumption of 36.81 nW and impact sensing with 20 μs response time (much faster compared to the commercially available ones) are shown to be possible

Optik biyo-tespit uygulamaları amacıyla tasarlanmış tek boyutlu yarık modlu fotonik kristal kavite.

In this thesis, we presented a refractive index based optical bio-sensor, utilizing a slot mode one dimensional photonic crystal cavity as a transducing element. We benefited from the suitability of slotted one dimensional photonic crystal cavities for optical bio-sensing applications, owing to their capability of confining the light strongly in the low dielectric media. We described the theory behind the design, and also provided numerical analyses, characterizing the device performance. We also demonstrated a performance enhancement method, relying on an optomechanical feedback loop, which can enhance both the quality factor and the sensitivity of the resonant cavity. The enhancement mechanism is triggered when the target analyte enters the background medium and modifies the cavity slot width, by benefiting from the optical transverse gradient forces inside the cavity. By the help of the optomechanical feedback loop, the intrinsic trade-off between the performance factors can be eliminated, resulting in an improved figure of merit. In the thesis, we demonstrated the operation principle of the enhancement method, together with the numerical calculations necessary for the investigation of the level of enhancement. Our optomechanical feedback loop can be appended to any resonant structure vi without any modification, proposing a strong potential for our enhancement method to be utilized in other refractive index based optical bio-sensing schemes.Thesis (M.S.) -- Graduate School of Natural and Applied Sciences. Electrical and Electronics Engineering

Breaking the trade-off between Q-factor and sensitivity for high-Q slot mode photonic crystal nanobeam cavity biosensors with optomechanical feedback

Here, a method to eliminate the trade-off between quality factor (Q-factor) and sensitivity of a one dimensional slot mode photonic crystal nanobeam cavity biosensor is presented. Applied method utilizes an optomechanical feedback mechanism in order to generate transverse gradient optical forces inside the cavity. A pump mode is utilized in order to generate the optical force, triggered by intrusion of analyte into the background medium. The amount of generated force is controlled via an interference mechanism at the output realized by the feedback loop. By utilizing created optical force, slot width of the nanobeam cavity is dynamically tuned and the quality factor degradation due to the decrease in the refractive index contrast of the cavity is compensated by enhancing the field confinement inside the cavity. With the contribution of the slot width tuning to the resonant wavelength shift, sensitivity of the biosensor is increased without any degradation of the Q-factor. Numerical analyses regarding the cavity design and the elimination of trade-off are provided. Obtained results show that the both performance can be increased at the same time

Optomechanically Enhanced High-Q Slot Mode Photonic Crystal Nanobeam Cavity

A high-Q slot mode photonic crystal nanobeam cavity based biosensor design with positive optomechanical feedback is presented. Detailed analysis of sensitivity enhancement due to feedback shows a fourfold improvement without any compromise in quality factor

High-Q Slot-Mode Photonic Crystal Nanobeam Cavity Biosensor With Optomechanically Enhanced Sensitivity

A biosensor design based on a photonic crystal nanobeam cavity with an optomechanical positive feedback mechanism is proposed. Design of the cavity and optomechanical sensitivity enhancement method are numerically analyzed and the results show that fourfold improvement is possible without any degradation of the Q-factor

High-Q Slot-Mode Photonic Crystal Nanobeam Cavity Biosensor With Optomechanically Enhanced Sensitivity

A biosensor design based on a photonic crystal nanobeam cavity with an optomechanical positive feedback mechanism is proposed. Design of the cavity and optomechanical sensitivity enhancement method are numerically analyzed and the results show that fourfold improvement is possible without any degradation of the Q-factor

Advanced Design of Schottky Photodiodes in Bulk CMOS for High Speed Optical Receivers

status: publishe

Advanced Design of Schottky Photodiodes in Bulk CMOS for High Speed Optical Receivers

This paper provides theoretical insight on how circular Schottky photodiodes in bulk CMOS can be optimized for certain integrated receiver applications. An optimal photodiode size is analytically demonstrated and the effects of a metal plate reflector are simulated using a transfer-matrix method, both for frontside and backside illumination. Finally, a distributed circuit model is presented, which deviates from the classical lumped model for large photodiodes or sheet resistances. The presented methodologies can also be extended to other types of photodetectors

A 2D Slotted Rod Type PhC Cavity Inertial Sensor Design for Impact Sensing

A tunable 2D rod type Si Photonic Crystal cavity based impact sensing configuration is proposed and numerically analyzed. The cavity is sandwiched by perfect electric conductor (PEC) boundaries in order to provide out-of-plane light confinement. An on-purpose air slot is introduced between the Si rods and top PEC plate moving the light confinement into the slotted region and making the cavity highly responsive to the displacement of top PEC boundary. Optomechanical coupling strength is calculated to be on the order of 300 GHz/nm. Proposed light confinement inside the slot shows similar characteristics to slot waveguiding phenomenon and offers valuable opportunities for mechanical sensing applications. For a practical approach, PEC boundaries are replaced by Gold plates and the potential of the structure as an inertial sensor is investigated with a specific focus on impact sensing applications to be used in automotive security systems. Numerical analyses indicate that the device, whose sensing area is only 106.6 mu m2, has a response time of 16.6 mu s asserting that the proposed sensor can sense the presence of an impact faster than several commercially available ones, in a much more compact form

Flexible waveguides with amorphous photonic materials

Amorphous photonic materials offer an alternative to photonic crystals as a building block for photonic integrated circuits due to their shared short-range order. By using the inherent disorder of amorphous photonic materials, it is possible to design flexible-shaped waveguides that are free from restrictions of photonic crystals at various symmetry axes. Effects of disorder on photonic crystal waveguide boundaries have examined before, and it is shown that flexible waveguides with high transmission are possible by forming a wall of equidistant scatterers around the defect created inside amorphous material configuration. Based on this principle, waveguides with various flexible shapes are designed and fabricated for planar circuit applications. A silicon-on-insulator (SOI) slab with random configuration of air hole scatterers is used. The amorphous configuration is generated through realistic Monte Carlo simulations mimicking crystalline-to-amorphous transition of semiconductor crystals via an assigned Yukawa potential to individual particles. The design parameters such as average hole distance, slab thickness and hole radius are adjusted so that the waveguide is utilizable around 1550 nm telecommunications wavelength. Such waveguides on slab structures are characterized here and the level of randomness and band gap properties of amorphous configurations are analyzed in detail. These efforts have the potential to lead easier design of a wide range of components including but not limited to on-chip Mach-Zehnder interferometers, splitters, and Y-branches