An interferometric modulator manufactured according to a particular set of processing parameters may have a non-zero offset voltage. A process has been developed for modifying the processing parameters to shift the non-zero offset voltage closer to zero. For example, the process may involve identifying a set of processing parameters for manufacturing an interferometric modulator that results in a non-zero offset voltage for the interferometric modulator. The set of processing parameters may then be modified to shift the non-zero offset voltage closer to zero. For example, modifying the set of processing parameters may involve modifying one or more deposition parameters used to make the interferometric modulator, applying a current (e.g., a counteracting current) to the interferometric modulator, and/or annealing the interferometric modulator. Interferometric modulators made according to the set of modified processing parameters may have improved performance and/or simpler drive schemes.

Process for modifying offset voltage characteristics of an interferometric modulator

The silicon nitride (Si3N4) planar waveguide platform has enabled a broad class of low-loss planar-integrated devices and chip-scale solutions that benefit from transparency over a wide wavelength range (400–2350 nm) and fabrication using wafer-scale processes. As a complimentary platform to silicon-on-insulator (SOI) and III–V photonics, Si3N4 waveguide technology opens up a new generation of system-on-chip applications not achievable with the other platforms alone. The availability of low-loss waveguides (<1 dB/m) that can handle high optical power can be engineered for linear and nonlinear optical functions, and that support a variety of passive and active building blocks opens new avenues for system-on-chip implementations. As signal bandwidth and data rates continue to increase, the optical circuit functions and complexity made possible with Si3N4 has expanded the practical application of optical signal processing functions that can reduce energy consumption, size and cost over today’s digital electronic solutions. Researchers have been able to push the performance photonic-integrated components beyond other integrated platforms, including ultrahigh Q resonators, optical filters, highly coherent lasers, optical signal processing circuits, nonlinear optical devices, frequency comb generators, and biophotonic system-on-chip. This review paper covers the history of low-loss Si3N4 waveguide technology and a survey of worldwide research in a variety of device and applications as well as the status of Si3N4 foundries.

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Silicon Nitride in Silicon Photonics

A recent renaissance in Brillouin scattering research has been driven by the increasing maturity of photonic integration platforms and nanophotonics. The result is a new breed of chip-based devices that exploit acousto-optic interactions to create lasers, amplifiers, filters, delay lines and isolators. Here, we provide a detailed overview of Brillouin scattering in integrated waveguides and resonators, covering key concepts such as the stimulation of the Brillouin process, in which the optical field itself induces acoustic vibrations, the importance of acoustic confinement, methods for calculating and measuring Brillouin gain, and the diversity of materials platforms and geometries. Our Review emphasizes emerging applications in microwave photonics, signal processing and sensing, and concludes with a perspective for future directions. Acousto-optical interactions within integrated optics platforms are reviewed with a discussion of the useful chip-based devices such as lasers, amplifiers, filters, isolators and more besides that can result.

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Brillouin integrated photonics

Photonic crystal fibers are a kind of fiber optics that present a diversity of new and improved features beyond what conventional optical fibers can offer. Due to their unique geometric structure, photonic crystal fibers present special properties and capabilities that lead to an outstanding potential for sensing applications. A review of photonic crystal fiber sensors is presented. Two different groups of sensors are detailed separately: physical and biochemical sensors, based on the sensor measured parameter. Several sensors have been reported until the date, and more are expected to be developed due to the remarkable characteristics such fibers can offer.

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Photonic crystal fibers for sensing applications

The authors demonstrate for the first time a near shot noise limited in-line Sagnac interferometer current sensor. It is shown to have a number of advantages over the optical current sensors based on polarimetric Faraday and Faraday/Sagnac loop interferometer topologies, including lower sensitivity to environmental disturbances, less demanding optical components, and easy installation. Its application to power system measurements is also detailed.

In-line Sagnac interferometer current sensor

Two major architectures of fiber optic gyroscopes have been under development at Honeywell in recent years. The interferometric fiber optic gyro (IFOG) has been in production and deployment for various high performance space and marine applications. Different designs, offering very low noise, ranging from better than navigation grade to ultra-precise performance have been tested and produced. The resonator fiber optic gyro (RFOG) is also under development, primarily for its attractive potential for civil navigation usage, but also because of its scalability to other performance. New techniques to address optical backscatter and laser frequency noise have been developed and demonstrated. Development of novel, enhanced RFOG architectures using hollow core fiber, silicon optical bench technology, and highly stable multifrequency laser sources are discussed.

Fiber optic gyro development at Honeywell

Single-mode (SM) fiber which is used in the sensing coil of depolarized interferometric fiber-optic gyroscopes (IFOG's) does not maintain the polarization state of light. As a consequence, the state of polarization evolves freely over the length of the sensing coil and over environment. The polarization evolution is induced by birefringence within the SM coil. Variations of this birefringence may lead to nonreciprocal errors whose treatment is presented in this paper together with signal fading and the mean wavelength stability. Thus, this treatment provides a relatively comprehensive analysis of polarization evolution in depolarized gyroscopes. The analysis leads to the conclusion that the depolarized gyro architecture with two depolarizers on the opposite sides of the gyro loop must be used to obtain low-drift behaviour.

Theory of polarization evolution in interferometric fiber-optic depolarized gyros

Methods and apparatus are provided for stabilizing laser light sources of a resonator gyro. A resonator gyro comprises a first light source configured to produce a first input light, a second light source configured to produce a second input light, a resonator coupled to the first and second light sources, a resonance detection circuit coupled to the resonator, and a controller coupled to the resonance detection circuit and the first and second light sources. The resonance detection circuit detects a resonance frequency for each of the counter-propagating directions of the resonator. The controller tunes the first input light to a clockwise resonance frequency, and tunes the second input light to a counter-clockwise resonance frequency. A difference between the resonance frequencies is proportional to a rotational rate of the resonator gyro.

System and method for stabilizing light sources in resonator gyro

An exciting new fiber optic resonator architecture that addresses performance barriers of the past is presented for applications in rotation sensing. It uses bandgap fiber. Experimental results of first resonators showing encouraging performance are presented.

Hollow Core Fiber Optic Ring Resonator for Rotation Sensing

Fiber-optic gyroscopes (FOGs) are under development at Honeywell as the primary next generation inertial sensor. The open-loop FOG technology has been successfully transitioned to production for attitude heading reference systems and the results of this effort are reported. New developments in closed-loop FOG technology aimed at high performance space applications and at navigation grade aviation applications, are underway. In the former case, results on a high precision FOG are reported. In the latter case, special emphasis is placed on improvements of depolarized FOG technology, which promises to produce a low cost navigation grade sensor.

Glen A. Sanders

Papers

Fiber optic gyro development at Honeywell

Theory of polarization evolution in interferometric fiber-optic depolarized gyros

System and method for stabilizing light sources in resonator gyro

Hollow Core Fiber Optic Ring Resonator for Rotation Sensing

Fiber optic gyros for space, marine, and aviation applications