Jerome Lapointe

Fabrication of high quality, ultra-long fiber Bragg gratings: up to 2 million periods in phase

The fabrication and characterization of high quality ultra-long (up to 1m) fiber Bragg gratings (FBGs) is reported. A moving phase mask and an electro-optic phase-modulation (EOPM) based interferometer are used with a high precision 1-meter long translation stage and compared. A novel interferometer position feedback scheme to simplify the fabrication process is proposed and analyzed. The ultra-long uniform FBGs show near perfect characteristics of a few picometers bandwidth, symmetrical, near theory-matching group-delay and transmission spectra. Grating characterization using optical backscattering reflectometry and chirped FBGs are also demonstrated. Limitations of the schemes are discussed.

Direct laser-writing of ferroelectric single-crystal waveguide architectures in glass for 3D integrated optics.

Direct three-dimensional laser writing of amorphous waveguides inside glass has been studied intensely as an attractive route for fabricating photonic integrated circuits. However, achieving essential nonlinear-optic functionality in such devices will also require the ability to create high-quality single-crystal waveguides. Femtosecond laser irradiation is capable of crystallizing glass in 3D, but producing optical-quality single-crystal structures suitable for waveguiding poses unique challenges that are unprecedented in the field of crystal growth. In this work, we use a high angular-resolution electron diffraction method to obtain the first conclusive confirmation that uniform single crystals can be grown inside glass by femtosecond laser writing under optimized conditions. We confirm waveguiding capability and present the first quantitative measurement of power transmission through a laser-written crystal-in-glass waveguide, yielding loss of 2.64 dB/cm at 1530 nm. We demonstrate uniformity of the crystal cross-section down the length of the waveguide and quantify its birefringence. Finally, as a proof-of-concept for patterning more complex device geometries, we demonstrate the use of dynamic phase modulation to grow symmetric crystal junctions with single-pass writing.

Making smart phones smarter with photonics

Smart phones and tablets have become ubiquitous. Corning® Gorilla® Glass is well-known to provide durability and scratch-resistance to many smart phones and other mobile devices. Using femtosecond lasers, we report high quality photonic devices, such as a temperature sensor and an authentication security system, we believe for the first time. It was found that this kind of glass is an exceptional host for three dimensional waveguides. High quality multimode waveguides are demonstrated with the lowest measured loss value (0.027 dB/cm loss) to our knowledge in any glass using fs laser inscription. High quality (0.053 dB/cm loss) single-mode waveguides have been also fabricated using a fs laser scan speed of 300 mm/s, the fastest fabrication speed reported to date. The longest high quality waveguides (up to 1m) are also reported. Experiments reveal that Gorilla Glass seems to be an ideal glass to write waveguides just below the surface, which is of great interest in sensing applications.

Fabrication of ultrafast laser written low-loss waveguides in flexible As₂S₃ chalcogenide glass tape.

As2S3 glass has a unique combination of optical properties, such as wide transparency in the infrared region and a high nonlinear coefficient. Recently, intense research has been conducted to improve photonic devices using thin materials. In this Letter, highly uniform rectangular single-index and 2 dB/m loss step-index optical tapes have been drawn by the crucible technique. Low-loss (<0.15  dB/cm) single-mode waveguides in chalcogenide glass tapes have been fabricated using femtosecond laser writing. Optical backscatter reflectometry has been used to study the origin of the optical losses. A detailed study of the laser writing process in thin glass is also presented to facilitate a repeatable waveguide inscription recipe.

A ‘living’ prosthetic iris

AimTo design and demonstrate dynamic pupils, which react to light for use with ocular prostheses.MethodsThe realism of ocular prostheses is limited by the immobility of the pupil. Our solution is to use a liquid crystal display (LCD) in the prosthesis to vary the pupil size as a function of the ambient light. Several liquid crystal cells were fabricated and tested for survivability through the ocular prosthesis manufacturing process. The dynamic pupil is controlled by a novel and entirely autonomous, self-powered passive electronic circuit using a solar cell, matching the minimum diameter of the pupil.ResultsThe first LCD surviving the rugged conditions of the ocular prosthesis manufacturing steps and an entirely passive circuit controlling the pupil have been demonstrated for the first time to our knowledge. A design for a complete prosthesis with a dynamic pupil has been proposed. Finally, a standard device for the mass production of ocular prostheses is presented.ConclusionWe have shown that a practical solution for an autonomous self-powered dynamic pupil is possible, given the constraints of size, fabrication process, weight, cost and manufacturability on a mass scale. We envision that the LCD could be mass produced, and only the final steps for the integration of the iris matched to a patient would be necessary before assembly using standard processing steps for the production of the prosthesis. Using a clinical trial, we hope to demonstrate that the dynamic pupil will have a positive impact on the quality of life of patients.

Enhancement of accuracy in shape sensing of surgical needles using optical frequency domain reflectometry in optical fibers

We demonstrate a novel approach to enhance the precision of surgical needle shape tracking based on distributed strain sensing using optical frequency domain reflectometry (OFDR). The precision enhancement is provided by using optical fibers with high scattering properties. Shape tracking of surgical tools using strain sensing properties of optical fibers has seen increased attention in recent years. Most of the investigations made in this field use fiber Bragg gratings (FBG), which can be used as discrete or quasi-distributed strain sensors. By using a truly distributed sensing approach (OFDR), preliminary results show that the attainable accuracy is comparable to accuracies reported in the literature using FBG sensors for tracking applications (~1mm). We propose a technique that enhanced our accuracy by 47% using UV exposed fibers, which have higher light scattering compared to un-exposed standard single mode fibers. Improving the experimental setup will enhance the accuracy provided by shape tracking using OFDR and will contribute significantly to clinical applications.

High sensitivity inline fiber Mach-Zehnder interferometer bend sensor using a twin core fiber

A novel Mach-Zehnder interferometer based on a multimode fiber combined with a twin-core fiber is proposed. The section of twin-core fiber is spliced between a section of multimode fiber and a single mode fiber. The curvature induced wavelength shifts on the interference fringes is experimentally monitored. A blue shift is observed. This device is simple to fabricate, and is used as a bend sensor with good sensitivity.

Toward the integration of optical sensors in smartphone screens using femtosecond laser writing

We demonstrate a new type of sensor incorporated directly into Corning Gorilla glass, an ultraresistant glass widely used in the screen of popular devices such as smartphones, tablets, and smart watches. Although physical space is limited in portable devices, the screens have been so far neglected in regard to functionalization. Our proof-of-concept shows a new niche for photonics device development, in which the screen becomes an active component integrated into the device. The sensor itself is a near-surface waveguide, sensitive to refractive index changes, enabling the analysis of liquids directly on the screen of a smartphone, without the need for any add-ons, thus opening this part of the device to advanced functionalization. The primary function of the screen is unaffected, since the sensor and waveguide are effectively invisible to the naked eye. We fabricated a waveguide just below the glass surface, directly written without any surface preparation, in which the change in refractive index on the surface-air interface changes the light guidance, thus the transmission of light. This work reports on sensor fabrication, using a femtosecond pulsed laser, and the light-interaction model of the beam propagating at the surface is discussed and compared with experimental measurement for refractive indexes in the range 1.3-1.7. A new and improved model, including input and output reflections due to the effective mode index change, is also proposed and yields a better match with our experimental measurements and also with previous measurements reported in the literature.

Laser Processed Photonic Devices

The last century was that of electronics; it is now one of photonics. As Richard Feynman (Nobel Prize, 1965) suggested in 1959, “Smaller, Faster, Cheaper” would lead the world, and in many ways he has proven to be correct. Over the past decades, photonics devices and integrated optics have been among the most revolutionary areas of research and advances. Although integrated optics devices are well advanced these days, there is still much to do and most of these components are still expensive to manufacture for mass deployment. In fact, most of these require clean room facilities, as well as several expensive manufacturing steps such as phase mask fabrication or photolithography. This chapter aims at explaining a potential solution to fast manufacturing of cheap integrated optics by laser writing.

An ocular prosthesis which reacts to light

The realism of an ocular prosthesis is limited by the immobility of the pupil. Our method to solve this problem is to use a liquid crystal display (LCD) to control the pupil size as a function of the ambient light. This study demonstrates the first LCD to our knowledge surviving the ocular prosthetic manufacturing steps. The dynamic pupil is controlled by a novel, entirely autonomous and self-powered passive electronic circuit using photodiodes in a high voltage configuration. Future work for a complete prosthesis with a dynamic pupil is discussed. Finally, a standard device for the mass production of ocular prostheses is presented.