CN-122015797-A - Integrated Sagnac type sensor based on magneto-optical nonreciprocal phase-shifting waveguide

CN122015797ACN 122015797 ACN122015797 ACN 122015797ACN-122015797-A

Abstract

The invention belongs to the technical field of optics, and particularly relates to an integrated Sagnac type sensor based on a magneto-optical nonreciprocal phase shift waveguide. The integrated Sagnac type sensor based on the magneto-optical nonreciprocal phase shift waveguide provided by the invention is used for replacing a traditional phase modulator by integrating the magneto-optical nonreciprocal phase shift waveguide in the traditional Sagnac sensor, so that the modulation of the phase in the Sagnac interference arm is performed, and the integrated Sagnac type sensor is used for realizing passive high-sensitivity magnetic field or inertial sensing. Providing a viable path for improving sensitivity and engineering feasibility of the Sagnac type magnetic field/inertial sensor.

Inventors

BI LEI
WEI ZIXUAN
ZHENG LITING
WU DI

Assignees

电子科技大学

Dates

Publication Date: 20260512
Application Date: 20251126

Claims (7)

1. The integrated Sagnac type sensor based on magneto-optical nonreciprocal phase-shifting waveguide, the Sagnac interference structure is composed of a coupler, a nonreciprocal phase shifter and a section of closed loop optical waveguide, incident light is divided into two beams at the coupler to propagate in two directions of clockwise and anticlockwise in the loop respectively, and the incident light is coupled at the coupler to interfere after passing through the optical waveguide for one circle, and the integrated Sagnac type sensor is characterized in that: The non-reciprocal phase shifter is a passively biased magneto-optical non-reciprocal phase shifter, and a magneto-optical waveguide for non-reciprocal phase shifting is manufactured by integrating a magneto-optical material rare earth iron garnet RIG film on an optical waveguide, so that the magneto-optical non-reciprocal phase shifter is formed; When the sensing part waveguide does not generate non-reciprocal phase shift due to rotation or magnetic field, the light intensity output by the end waveguide is 1/2 of the incident light intensity, and when the sensing part waveguide generates non-reciprocal phase shift due to rotation or external magnetic field, the intensity output by the end waveguide can be measurably changed, thereby realizing angular velocity or magnetic field sensing.
2. The integrated Sagnac sensor based on magneto-optical nonreciprocal phase-shifting waveguides of claim 1 wherein the rare-earth element R of the rare-earth iron garnet RIG film is Ce, bi, Y, tb or Dy.
3. The integrated Sagnac sensor based on magneto-optical nonreciprocal phase shifting waveguides of claim 1 wherein the magneto-optical waveguides are designed to have lengths that produce nonreciprocal phase shifts that are 90 degrees out of phase.
4. The integrated Sagnac type sensor based on magneto-optical nonreciprocal phase shift waveguide according to claim 3, wherein the magneto-optical waveguide length is designed specifically as follows: The 90-degree nonreciprocal phase shift of the magneto-optical waveguide is realized by the nonreciprocal phase shift effect of the magneto-optical material, the magneto-optical effect of the magneto-optical material is described by the off-diagonal element of the dielectric tensor of the material, the direction of light propagation is set as the z direction, the magneto-optical material is lossless, and the direction of an in-plane magnetic field which is externally applied and perpendicular to the direction of light propagation is set as the x direction, and then the dielectric tensor is expressed as: ε = where j is the imaginary unit of the number, = For the dielectric tensor off-diagonal element, Vacuum wave number, n is refractive index of magneto-optical material, Is Faraday rotation angle; Considering that in a two-dimensional waveguide model, a perturbation theory pair is adopted to calculate the nonreciprocal phase shift, light is set to be a TM mode, the light propagates along the z direction, and the nonreciprocal phase shift is expressed as follows according to the perturbation theory: ( )= wherein N is the normalization constant of the waveguide mode; The magnitude and sign of the non-reciprocal phase-shifting NRPS is thus dependent on the magnitude and sign of the faraday rotation angle and the cross-sectional geometry of the waveguide; obtaining effective refractive index of magneto-optical waveguide by setting off-diagonal element of dielectric tensor of magneto-optical material by adopting finite element simulation software Propagation constant beta, and thus calculate the non-reciprocal phase shift per unit length Section length l=of non-reciprocal phase shift 。
5. The integrated Sagnac-type sensor based on magneto-optical nonreciprocal phase-shifting waveguides according to claim 1, wherein the coupler is a3 dB directional coupler or a multimode interferometer.
6. The integrated Sagnac type sensor based on magneto-optical nonreciprocal phase shifting waveguides according to claim 1, wherein: The Sagnac normalized output intensity is: wherein A minute phase change caused by a change in magnetic field or a change in rotational angular velocity; In the case of a magnetic field sensor, = Wherein For the length of the magnetic field sensing section, Then the magnitude and direction of the magnetic field; among the inertial sensors, as for the rotational angular velocity sensor, = Wherein For the number of turns of the waveguide, a is the annular area, As the wavelength of the light, For the speed of light in vacuum, Is the rotation angular velocity; At the offset point For small signals : And then obtain I Thus the response slope at 90℃offset is 。
7. The integrated Sagnac sensor based on magneto-optical nonreciprocal phase-shifting waveguides of claim 1 wherein the magneto-optical material of the magneto-optical waveguides is integrated by chemical vapor deposition or wafer bonding.

Description

Integrated Sagnac type sensor based on magneto-optical nonreciprocal phase-shifting waveguide Technical Field The invention belongs to the technical field of optics, in particular to an integrated Sagnac sensor based on a magneto-optical nonreciprocal phase shift waveguide, which replaces a traditional phase modulator with the magneto-optical nonreciprocal phase shift waveguide to realize high-sensitivity magnetic field or inertial sensing. Background In inertial gyroscopes and magnetic field optical sensors based on Sagnac interferometric rings, the loop operating point is often placed at the steepest phase response for maximum sensitivity, and therefore conventionally a phase modulator is often introduced in the loop to achieve a 90 ° quadrature bias of the light propagating clockwise and counterclockwise. Common biasing means include electro-optic, acousto-optic or piezoelectric phase modulators, which, while being capable of dynamically adjusting the operating point, present significant problems including the need for additional drive circuitry and power consumption, increased device volume and system complexity, reduced signal-to-noise ratio and device insertion loss due to modulation-induced phase noise and perturbation, and stability due to long-term drift, while many modulating elements are process incompatible, package and reliability challenges when planar integration, and high frequency driving limits bandwidth and low power requirements in certain application scenarios. For integrated optical sensors that are pursued of miniaturization, low power consumption and high stability, conventional active bias devices are significantly limited in practical engineering applications. In order to overcome the above-mentioned shortcomings, the industry also tries to realize passive bias by non-reciprocal element or optical polarization means, but the existing scheme depends on external faraday rotator, magneto-optical isolation element or high-loss magneto-optical film, and often faces the problems of large volume, high loss, poor coupling with waveguide platform, complex process and the like, so that it is difficult to balance between integration level and performance. Therefore, how to provide stable and nearly 90 ° non-reciprocal phase shift to replace the conventional phase modulator on the premise of low loss, integration and no need of dynamic driving is a key and pending problem for improving the overall performance and engineering feasibility of the Sagnac type sensor. Disclosure of Invention Aiming at the problems or the shortcomings, the invention provides an integrated Sagnac type sensor based on a magneto-optical nonreciprocal phase shift waveguide, a magneto-optical material rare earth iron garnet (RIG, R is a rare earth element including but not limited to Ce, bi, Y, tb and Dy) film with high Faraday rotation angle and low loss is integrated on the optical waveguide, and the 90-degree nonreciprocal phase shift (NRPS) with passive and nonreciprocal property is realized by designing the magnetization direction and the magneto-optical segment length, so that the sensor has important application value and technical prospect. The technical scheme of the invention is as follows: The integrated Sagnac sensor based on magneto-optical nonreciprocal phase-shifting waveguide comprises a coupler, a nonreciprocal phase shifter and a section of closed loop optical waveguide, wherein incident light is divided into two beams at the coupler and propagates in clockwise and anticlockwise directions in the loop respectively, and is coupled at the coupler for interference after passing through the optical waveguide for one turn. The non-reciprocal phase shifter is a passive biased magneto-optical non-reciprocal phase shifter, and a magneto-optical waveguide for non-reciprocal phase shifting is manufactured by integrating a magneto-optical material rare earth iron garnet RIG film on an optical waveguide, so that the magneto-optical non-reciprocal phase shifter is formed. The rare earth iron garnet RIG film of the magneto-optical material is a magnetic film material with obvious Faraday effect, the Faraday effect is obviously increased by doping rare earth such as Ce, bi and the like, so that larger nonreciprocal deflection can be generated in extremely short device length in a visible to near infrared band, and the RIG keeps low optical absorption (low insertion loss) under the high-quality film and is used as an insulator to avoid free carrier absorption, thereby meeting the requirements of large Faraday rotation angle and low loss. When the sensing part waveguide does not generate non-reciprocal phase shift due to rotation or magnetic field, the light intensity output by the end waveguide is 1/2 of the incident light intensity, and when the sensing part waveguide generates non-reciprocal phase shift due to rotation or external magnetic field, the intensity output by the end waveguide can be measurably changed, th