Mathieu Gagné

Demonstration of a 3 mW threshold Er-doped random fiber laser based on a unique fiber Bragg grating

We demonstrate a novel random laser based on a single fiber Bragg grating. A long fiber Bragg grating fabrication technique allows the insertion of a large number of randomly distributed phase errors in the structure of the grating which induces light localization. By writing such a grating in a polarisation maintaining Er-doped fiber, a random laser is demonstrated by pumping the fiber with 976 and 1480 nm pump lasers. The number of emitted modes is observed to be a function of the length of the grating and of the pump power and single-mode operation is shown to be possible. The random fiber laser shows low-threshold (approximately 3 mW) and measured approximately 0.5 pm emission linewidth at a wavelength of around 1534 nm.

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.

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.

Rayleigh scatter based order of magnitude increase in distributed temperature and strain sensing by simple UV exposure of optical fibre

We present a technique to improve signal strength, and therefore sensitivity in distributed temperature and strain sensing (DTSS) using Frequency domain Rayleigh scatter. A simple UV exposure of a hydrogen loaded standard SMF-28 fibre core is shown to enhance the Rayleigh back-scattered light dramatically by ten-fold, independent of the presence of a Bragg grating, and is therefore created by the UV exposure alone. This increase in Rayleigh back-scatter allows an order-of-magnitude increase in temperature and strain resolution for DTSS compared to un-exposed SMF-28 fibre used as a sensing element. This enhancement in sensitivity is effective for cm range or more sensor gauge length, below which is the theoretical cross-correlation limit. The detection of a 20 mK temperature rise with a spatial resolution of 2 cm is demonstrated. This gain in sensitivity for SMF-28 is compared with a high Ge doped photosensitive fibre with a characteristically high NA. For the latter, the UV enhancement is also present although of lower amplitude, and enables an even lower noise level for sensing, due to the fibre’s intrinsically higher Rayleigh scatter signal.

Random fiber Bragg grating Raman fiber laser

We demonstrate for the first time to our knowledge a Raman random fiber laser (RRFL) based on a long random fiber Bragg grating (RFBG-RRFL). Unlike other recently demonstrated random fiber lasers that rely on incoherent Rayleigh scattering feedback, the present scheme uses randomly distributed phase shifts inside a fiber-meter long Bragg grating as a random coherent feedback mechanism. The laser is pumped at 1480 nm and emits a CW signal at 1576 nm. The emission spectrum is dependent on pump intensity and is shown to exhibit single and multi-mode characteristics. The RRFL shows a relatively low threshold (2.2 W) and a ∼430 kHz FWHM linewidth.

Fiber Bragg gratings for low-temperature measurement.

We demonstrate the use of fiber Bragg gratings (FBGs) as a monolithic temperature sensor from ambient to liquid nitrogen temperatures, without the use of any auxiliary embedding structure. The Bragg gratings, fabricated in three different types of fibers and characterized with a high density of points, confirm a nonlinear thermal sensitivity of the fibers. With a conventional interrogation scheme it is possible to have a resolution of 0.5 K for weak pure-silica-core FBGs and 0.25 K using both boron-doped and germanium-doped standard fibers at 77 K. We quantitatively show for the first time that the nonlinear thermal sensitivity of the FBG arises from the nonlinearity of both thermo-optic and thermal expansion coefficients, allowing consistent modeling of FBGs at low temperatures.

Novel custom fiber Bragg grating fabrication technique based on push-pull phase shifting interferometry

A new UV-writing technique is proposed for fabricating custom fiber Bragg gratings (FBGs). A continuously moving fringe pattern is generated by use of two electro-optical UV modulators and synchronized with a moving fiber. This scheme potentially enables the fabrication of infinitely long FBGs with arbitrary profiles and chirp without any mechanical perturbation of the writing interferometer. Preliminary results of this technique are presented and discussed.

Surface plasmon resonance sensor interrogation with a double-clad fiber coupler and cladding modes excited by a tilted fiber Bragg grating.

We present a novel optical fiber surface plasmon resonance (SPR) sensor scheme using reflected guided cladding modes captured by a double-clad fiber coupler and excited in a gold-coated fiber with a tilted Bragg grating. This new interrogation approach, based on the reflection spectrum, provides an improvement in the operating range of the device over previous techniques. The device allows detection of SPR in the reflected guided cladding modes and also in the transmitted spectrum, allowing comparison with standard techniques. The sensor has a large operating range from 1.335 to 1.432 RIU, and a sensitivity of 510.5 nm/RIU. The device shows strong dependence on the polarization state of the guided core mode which can be used to turn the SPR on or off.

Creation of backdoors in quantum communications via laser damage

Practical quantum communication (QC) protocols are assumed to be secure provided implemented devices are properly characterized and all known side channels are closed. We show that this is not always true. We demonstrate a laser-damage attack capable of modifying device behavior on demand. We test it on two practical QC systems for key distribution and coin tossing, and show that newly created deviations lead to side channels. This reveals that laser damage is a potential security risk to existing QC systems, and necessitates their testing to guarantee security.

Glassy behavior in a one-dimensional continuous-wave erbium-doped random fiber laser

Anderson S. L. Gomes, ∗ Bismarck C. Lima, Pablo I. R. Pincheira, André L. Moura, 2 Mathieu Gagné, Raman Kashyap, Ernesto P. Raposo, and Cid B. de Araújo Departamento de F́ısica, Universidade Federal de Pernambuco, 50670-901, Recife-PE, Brazil Grupo de F́ısica da Matéria Condensada, Núcleo de Ciências Exatas NCEx, Campus Arapiraca, Universidade Federal de Alagoas, 57309-005, Arapiraca-AL, Brazil Fabulas Laboratory, Department of Engineering Physics, Department of Electrical Engineering, Polytechnique Montreal, Montreal, H3C 3A7, Canada Laboratório de F́ısica Teórica e Computacional, Departamento de F́ısica, Universidade Federal de Pernambuco, 50670-901, Recife-PE, Brazil (Dated: January 8, 2016)