Nanopositioning Stages Help Create And Characterize Laser-Written Waveguides Inside Silicon

Nanopositioning Stages Help Create And Characterize Laser-Written Waveguides Inside Silicon

Nanopositioning Stages Help Create And Characterize Laser-Written Waveguides Inside Silicon

The future of computing and data communications will rely on a combination of optics and electronics. Silicon photonics circuits are gaining in importance; new techniques and tools for test and production of SiP related technologies are being researched and developed around the world.

Direct laser writing of waveguides deep inside the bulk of monolithic crystalline silicon (c-Si) has been recently demonstrated by researchers at the National Center for Scientific Research Center and Aix-Marseille University (LP3 laboratory, Marseille, France). A crucial part in the waveguide characterization is the measurement of the refractive index with a customized Mach-Zehnder-type phase-shift interference microscope.

Principle schematic of the experimental set-up dedicated to the inscription of waveguides inside monolithic crystalline silicon, and characterization of the refractive index change of the produced modification. (Image: LP3 Laboratory)
Principle schematic of the experimental set-up dedicated to the inscription of waveguides inside monolithic crystalline silicon, and characterization of the refractive index change of the produced modification. (Image: LP3 Laboratory)

Basically, this interferometer is composed of two infrared beams with an optical delay precisely controlled by means of a mirror mounted on a P-721.LLQ PIFOC® piezo flexure nanopositioning stage with position feedback. The refractive index is obtained by making four interference images with precise increments of 162.5 nm (i.e., λ/8) on the stage so that a π/2 relative phase delay is added between acquisitions. By choosing appropriate laser writing parameters, the relative change of the refractive index exceeds 10-3 which is sufficient to guide light inside c-Si.

Phase images of modifications produced at the indicated writing speeds. (a), (c), and (d) exhibit unwanted micro-cavities (dark spots), while (b) shows a homogeneous positive phase shift, corresponding to a refractive index change ∆n≈5.3×〖10〗^(-3), which is sufficient to guide light. (Source: LP3 Laboratory)
Phase images of modifications produced at the indicated writing speeds. (a), (c), and (d) exhibit unwanted micro-cavities (dark spots), while (b) shows a homogeneous positive phase shift, corresponding to a refractive index change ∆n≈5.3×〖10〗^(-3), which is sufficient to guide light. (Source: LP3 Laboratory)

These developments pave the way toward the capability of producing and imaging 3D architectures for the rapidly growing field of silicon photonics.

P-721 PIFOC® (left) piezo flexure nanopositioning stage shown in experimental set-up. (Source: LP3 Laboratory)
P-721 PIFOC® (left) piezo flexure nanopositioning stage shown in experimental set-up. (Source: LP3 Laboratory) Learn more
A P-721 PIFOC® closed-loop piezo flexure nanopositioning stage, shown with a microscope lens (Image: PI)
A P-721 PIFOC® closed-loop piezo flexure nanopositioning stage, shown with a microscope lens (Image: PI) Learn more

Piezo flexure positioner background: Due to the lack of friction, closed-loop piezo flexure stages can provide nanometer resolution and below, as well as very smooth and uniform motion. Depending on the control signal, velocities down to nanometers per second are possible.  On the other end of the spectrum, fast step and settle in milliseconds is also possible. A variety of position feedback sensors are available to match the requirements of the application (resolution, linearity, noise floor, bandwidth).

Nanometer resolution: Piezo flexure positioners can provide resolution significantly smaller than the wavelength of light. The graph shows response of a P-630 piezo flexure nanopositioning stage to a square wave control signal equivalent to one nanometer. The positioner is capable of resolving motion in the 0.1 nanometer range. Measured with Zygo Laser Interferometer. (Image: PI)
Nanometer resolution: Piezo flexure positioners can provide resolution significantly smaller than the wavelength of light. The graph shows response of a P-630 piezo flexure nanopositioning stage to a square wave control signal equivalent to one nanometer. The positioner is capable of resolving motion in the 0.1 nanometer range. Measured with Zygo Laser Interferometer. (Image: PI)

Product Overview

More Reading

Subscribe to Tech Blog

Sign up to receive an email of new blog posts.

Please read the following and confirm your consent to the processing of your data.

By submitting this form, you consent to the PI Group contacting you through the communication channels you specify. Additionally, you acknowledge that the PI Group may store, process, and analyze the necessary data.

For further information, see our >> Privacy Policy.

Each email includes an unsubscribe link that allows you to withdraw your consent.

Privacy Policy*
spacer

contact@pi-usa.us

EAST & MIDWEST
(508) 832-3456
WEST
(949) 679-9191

spacer