We propose a new approach to improve the mode beamwidth and power efficiency of laser systems rel... more We propose a new approach to improve the mode beamwidth and power efficiency of laser systems relying on a stable resonator geometry. The algorithm is simple and straightforward. The desired output beam profile (e.g. super-Gaussian) is propagated in the intracavity medium, and its wavefront is then determined for the design of a graded-phase mirror. A numerical analysis of the influence of practical design parameters, such as geometrical factor and Fresnel numbers, indicates a very low loss for the fundamental mode as well as a very high discrimination of higher modes. It has also been found that this type of resonator is not very sensitive to various types of perturbation. In particular, gain saturation has little effect on the mode shapes and the desired fundamental mode remains predominating. Phase perturbations (including possible thermal lensing effects) have also been considered. We conclude that this resonator can increase significantly the mode volume and favor the single-mode operation of laser systems using a stable configuration.
The phenomenon of self-trapping has been extensively studied in the past for both cubic and satur... more The phenomenon of self-trapping has been extensively studied in the past for both cubic and saturable nonlinearity.1 In this paper, by using a modified nonlinear Schrodinger equation, we analyze the possibility of a self-trapped beam propagating in a weakly saturated amplifying/absorb- ing medium. We consider the case of only one transverse dimension (for example, a semiconductor laser medium or a nonlinear planar waveguide structure such as the one used by Maneuf and Reynaud2 for their recent observation of spatial solitary waves). A simple exact analytical solution is obtained with a sechlike amplitude profile and a nonuniform phase front. Near this axis, this wavefront is parabolic but becomes progressively linear off-axis. Selftrapping is also predicted for a defocusing nonlinearity. The stability of the solution is investigated by using the adiabatic approximation as well as by solving the equation of propagation numerically.
All-optical switching in a nonlinear directional coupler and the evolution of the state of polari... more All-optical switching in a nonlinear directional coupler and the evolution of the state of polarization in a nonlinear biréfringent fiber represent two important practical problems of propagation in a two-mode, nonlinear dispersive system. Both cases are described by a nonintegrable system of coupled nonlinear Schrödinger equations. On the basis of numerical simulations,1 it has already been shown that solitons present important advantages over differently shaped pulses. To improve our physical insight into the dynamics resulting from the complex interplay between nonlinearity (self- and cross-phase modulation), dispersion, and linear coupling, we have developed an approximate all-analytical model of soliton interaction. An extension of a variational method2 has been used, and the results can be recast in a suggestive potential-well picture. Besides improved estimates of optical switching powers, a symmetry-breaking instability can easily be anticipated. A detailed comparison with numerical simulations, showing a good overall agreement between exact and approximate results, will be presented.
The second-moment method permits one to follow the propagation of a general optical beam through ... more The second-moment method permits one to follow the propagation of a general optical beam through a paraxial system (described by an ABCD ray matrix) by using the generalized complex radius of curvature Q1.
The recent introduction of the beam quality factor1 can be thought of as a major forward step tow... more The recent introduction of the beam quality factor1 can be thought of as a major forward step towards the assessment of the spatial quality of general optical beams with a sole numerical parameter.
Nonlinear Guided Waves and Their Applications, 1996
In optical communication systems, the use of alternating dispersion is a common way to deal with ... more In optical communication systems, the use of alternating dispersion is a common way to deal with bit-rate limitations caused by dispersive pulse broadening. An alternative to this technique was proposed by Yariv et al[1] some time ago. It was suggested that a phase-conjugate conversion of the signal at the middle of the propagation length would cancel, at the line output, the accumulated dispersive effects over the first half propagation. Although more complicated than the first technique, this approach has the advantage of also being able to compensate for the self-phase modulation effects incurred through the Kerr nonlinearity of silica fibers, as first demonstrated experimentally by Watanabe et al[2].
1994 Conference on Lasers and Electro-Optics Europe, 1994
The advent of lossless graded-reflectivity mirrors (GRMs) is now widely recognized as an importan... more The advent of lossless graded-reflectivity mirrors (GRMs) is now widely recognized as an important headway in the field of optical resonators.1 When used as the feedback output mirror inside an unstable resonator cavity (Fig. 1), a GRM greatly improves the quality of the nearfield by yielding a wide beam with reduced ripples thanks to its tapered edges. In contrast, the more conventional unstable cavity yields an annular output beam with hard-edge truncation and disappointing beam quality for near-field applications.
Conference on Lasers and Electro-Optics Europe, 1996
The problem of controlling the parameters of laser radiation becomes particularly topical in view... more The problem of controlling the parameters of laser radiation becomes particularly topical in view of the widespread use of lasers in medicine and technological processes. In this paper, we present the results of investigations of the possibility to form beams with different orders of super-Gaussian profile at the output of a stable laser cavity with the help of an active mirror. As shown in Ref.[1], in order to get these intensity profiles, it is necessary to construct specially calculated profiles of minor surface. As an example, on Fig.1 curve "A" represents such a surface profile. We tried to reproduce this shape with the help of a deformable bimorph minor (curve "B" on Fig.1). Since this profile was symmetrical, we used a minor with ring control electrodes. Such minor was a circular concave semipassive bimorph one with three electrodes. To minimize the root-mean-square (RMS) error between our profile and the necessary one, we combined the real (measured by interferometer) response functions of our minor with different weights. In practice, this amounts to applying a particular voltage to the electrodes of the deformable minor. As shown in Fig.1 (corresponding to a super-Gaussian of order 8), we were able to reproduce the appropriate minor profiles with a corresponding RMS enor of only 0.03% (curve "B"). Figure 2 compares the corresponding calculated near-field distributions (including saturation and edge diffraction effects) for a 2 m long stable cavity. The nearly identical associated far-fields are depicted on Fig. 3. A comparison with a conventional spherical resonator designed to yield a similar output beam divergence allows us to expect ≈ 30% power increase owing to the higher extraction efficiency of super-Gaussian beam profiles. Similar conclusions have been reached for a super-Gaussian of order 6. These calculations make us believe that our intracavity bimorph deformable mirror with only three control elements is able to reproduce super-Gaussian output radiation of the CW CO2 laser with a stable cavity. An experiment to verify this is under way.
Conference on Lasers and Electro-Optics Europe, Aug 24, 2005
Optical resonators designed for lowto medium-gain lasers generally consist of “stable” cavities u... more Optical resonators designed for lowto medium-gain lasers generally consist of “stable” cavities using spherical mirrors. The nearly ideal Gaussian fundamental mode profile of such resonators is advantageous in terms of beam quality and reduced diffraction losses. However, for laser applications requiring single transverse mode operation, the stable geometry presents a serious drawback in terms of energy efficiency. The small beamwaist of the confined fundamental mode exploits only a reduced fraction of the available gain section and the poor modal selectivity limits the degree of saturation that can be reached in the single mode regime. The idea of using aspherical mirrors (graded-phase mirrors GPMs) has been proposed in the early days of laser development. The objective was to increase the effective mode cross section by improving the uniformity of the fundamental mode. However, in absence of guidelines, those studies were made on a trial-and-error basis and the conclusions were far from exhaustive. The interest for aspherical mirrors was also refrained by limitations in technology. Over the last few years, we have proposed’ and experimentally demonstrated* a different approach in the design of stable resonators using GPMs. These so-called ”custom phase-conjugate resonators” make it possible for the user to specify the output profile, which is the most appropriate to a given application. The design procedure exploits the fact that the wavefront of a lossless mode matches the mirror surfaces so that the reflected field is the phase-conjugate version of the incident field; the beam retums on itself after reflection (Fig. 1). So, in order to shape the fundamental mode as desired, the trick simply consists in deforming the mirror profile to make it correspond to the wavefront of this mode once propagated (numerically) up to the mirror position.’ Because the phase conjugation process here is passive and,
ABSTRACT Citation C. Paré, A. Villenueve, P. -. Bélanger, N. Bélanger, and N. J. Doran, &quot... more ABSTRACT Citation C. Paré, A. Villenueve, P. -. Bélanger, N. Bélanger, and N. J. Doran, "Dispersion and Self-Phase Modulation Compensation Based on a Negative Nonlinearity," in Integrated Photonics Research, Vol. 6 of 1996 OSA Technical Digest Series (Optical Society of America, 1996), paper IThA7. http://www.opticsinfobase.org/abstract.cfm?URI=IPR-1996-IThA7
Nonlinear Guided Waves and Their Applications, 1998
It is now widely recognized that the so-called technique of dispersion management represents a ma... more It is now widely recognized that the so-called technique of dispersion management represents a major headway for both NRZ and soliton communication systems (for a recent review, see [1,2]). Thanks to a low average dispersion, the Gordon-Haus timing jitter, deleterious to soliton systems, can be minimized and the observed enhancement of the pulse's energy implies a better signal-to-noise ratio, hence improving the bit-error rate at the reception. The main predictions of numerical simulations having been confirmed experimentally [3,4], it now seems natural to look for simple design tools in order to optimize future dispersion-managed soliton communication links.
electron beam is generated with a modified projection television gun. It has an energy of 7-15 ke... more electron beam is generated with a modified projection television gun. It has an energy of 7-15 keV and a current of up to 1 mA. The focussed electron beam has an elongated spot size of approximately 200 pm by 20 pm and can be magnetically scanned along the bar length with frequencies up to 100 kHz. The optical near field (NF), the far field parallel to the epitaxial layers (FF,,), and the output power are given in Fig. 2 as a function of input current. These are measured at one position with a nonscanning pulsed electron beam at 8 keV. The output power shows the well-known threshold behaviour. At threshold, the input power is about a factor of 4-6 times higher than the power required to operate a similar laser structure as a diode laser. This can be understood quantitatively, as energy is lost by backscattering and heat generation. At the laser threshold, the NF narrows appreciably to values below 20 pm (FWHM), indicating that more than 50 laser positions can be resolved per millimeter bar length. The FF,, is 5" (FWHM) as can be seen in the figure, and it does not depend on the input power. The Far Field perpendicular to the epitaxial layers was measured to be 50" (FWHM), a value that was expected from the thickness and composition of the epitaxial layers. The light output as a function of position on the bar is given in Fig. 3. A fairly homogeneous emission is observed at an output power of more than 20 mW. Some local dips indicate the presence of defects and/or damage originating from handling and mounting the laser bar. The electron beam has a scan velocity of 1000 m/s, scanning 5 mm in 5 ps. With 50 addressable lasers per millimeter of bar length, this corresponds to a laser scanner data rate of 50 Mbit/s. New applications such 5 30 g 20 ; 10
17th International Conference on Optical Fibre Sensors, 2005
ABSTRACT A quasi-distributed fibre optics polarimetric sensor has been studied both theoretically... more ABSTRACT A quasi-distributed fibre optics polarimetric sensor has been studied both theoretically and experimentally. Theoretical results demonstrate the feasibility of such a sensor when a polarization-maintaining optical fibre has been properly designed. Two designs are proposed. Distributed detection of water has been demonstrated with a standard polarization-maintaining fibre whose cladding was locally removed by chemical etching.
Abstract Ion-selective optodes offer potential for in-line monitoring of various processes. Fibre... more Abstract Ion-selective optodes offer potential for in-line monitoring of various processes. Fibre sensors were developed for H+, Ca2+, K+, Na+, NH4+ and NO3-. Applications in hydroponic culture optimization, soil characterization and anaerobic digester process ...
The translation of CARS imaging towards real time, high resolution, chemically selective endoscop... more The translation of CARS imaging towards real time, high resolution, chemically selective endoscopic tissue imaging applications is limited by a lack of sensitivity in CARS scanning probes sufficiently small for incorporation into endoscopes. We have developed here a custom double clad fiber (DCF)-based CARS probe which is designed to suppress the contaminant Four-Wave-Mixing (FWM) background generated within the fiber and integrated it into a fiber based scanning probe head of a few millimeters in diameter. The DCF includes a large mode area (LMA) core as a first means of reducing FWM generation by ~3 dB compared to commercially available, step-index single mode fibers. A micro-fabricated miniature optical filter (MOF) was grown on the distal end of the DCF to block the remaining FWM background from reaching the sample. The resulting probe was used to demonstrate high contrast images of polystyrene beads in the forward-CARS configuration with > 10 dB suppression of the FWM background. In epi-CARS geometry, images exhibited lower contrast due to the leakage of MOF-reflected FWM from the fiber core. Improvements concepts for the fiber probe are proposed for high contrast epi-CARS imaging to enable endoscopic implementation in clinical tissue assessment contexts, particularly in the early detection of endoluminal cancers and in tumor margin assessment.
Using a variational method, we have developed an approximate model of the dynamics of soliton cou... more Using a variational method, we have developed an approximate model of the dynamics of soliton coupling described by coupled nonlinear Schrodinger equations. The results are analytical and can be recast into a suggestive particlelike description providing a physical insight into the problem. The particular case of the nonlinear coherent coupler is emphasized, and an estimate of the soliton switching peak power is obtained. A symmetry-breaking instability is also described, in a simple way, with the potential-well picture.
We propose a new approach to improve the mode beamwidth and power efficiency of laser systems rel... more We propose a new approach to improve the mode beamwidth and power efficiency of laser systems relying on a stable resonator geometry. The algorithm is simple and straightforward. The desired output beam profile (e.g. super-Gaussian) is propagated in the intracavity medium, and its wavefront is then determined for the design of a graded-phase mirror. A numerical analysis of the influence of practical design parameters, such as geometrical factor and Fresnel numbers, indicates a very low loss for the fundamental mode as well as a very high discrimination of higher modes. It has also been found that this type of resonator is not very sensitive to various types of perturbation. In particular, gain saturation has little effect on the mode shapes and the desired fundamental mode remains predominating. Phase perturbations (including possible thermal lensing effects) have also been considered. We conclude that this resonator can increase significantly the mode volume and favor the single-mode operation of laser systems using a stable configuration.
The phenomenon of self-trapping has been extensively studied in the past for both cubic and satur... more The phenomenon of self-trapping has been extensively studied in the past for both cubic and saturable nonlinearity.1 In this paper, by using a modified nonlinear Schrodinger equation, we analyze the possibility of a self-trapped beam propagating in a weakly saturated amplifying/absorb- ing medium. We consider the case of only one transverse dimension (for example, a semiconductor laser medium or a nonlinear planar waveguide structure such as the one used by Maneuf and Reynaud2 for their recent observation of spatial solitary waves). A simple exact analytical solution is obtained with a sechlike amplitude profile and a nonuniform phase front. Near this axis, this wavefront is parabolic but becomes progressively linear off-axis. Selftrapping is also predicted for a defocusing nonlinearity. The stability of the solution is investigated by using the adiabatic approximation as well as by solving the equation of propagation numerically.
All-optical switching in a nonlinear directional coupler and the evolution of the state of polari... more All-optical switching in a nonlinear directional coupler and the evolution of the state of polarization in a nonlinear biréfringent fiber represent two important practical problems of propagation in a two-mode, nonlinear dispersive system. Both cases are described by a nonintegrable system of coupled nonlinear Schrödinger equations. On the basis of numerical simulations,1 it has already been shown that solitons present important advantages over differently shaped pulses. To improve our physical insight into the dynamics resulting from the complex interplay between nonlinearity (self- and cross-phase modulation), dispersion, and linear coupling, we have developed an approximate all-analytical model of soliton interaction. An extension of a variational method2 has been used, and the results can be recast in a suggestive potential-well picture. Besides improved estimates of optical switching powers, a symmetry-breaking instability can easily be anticipated. A detailed comparison with numerical simulations, showing a good overall agreement between exact and approximate results, will be presented.
The second-moment method permits one to follow the propagation of a general optical beam through ... more The second-moment method permits one to follow the propagation of a general optical beam through a paraxial system (described by an ABCD ray matrix) by using the generalized complex radius of curvature Q1.
The recent introduction of the beam quality factor1 can be thought of as a major forward step tow... more The recent introduction of the beam quality factor1 can be thought of as a major forward step towards the assessment of the spatial quality of general optical beams with a sole numerical parameter.
Nonlinear Guided Waves and Their Applications, 1996
In optical communication systems, the use of alternating dispersion is a common way to deal with ... more In optical communication systems, the use of alternating dispersion is a common way to deal with bit-rate limitations caused by dispersive pulse broadening. An alternative to this technique was proposed by Yariv et al[1] some time ago. It was suggested that a phase-conjugate conversion of the signal at the middle of the propagation length would cancel, at the line output, the accumulated dispersive effects over the first half propagation. Although more complicated than the first technique, this approach has the advantage of also being able to compensate for the self-phase modulation effects incurred through the Kerr nonlinearity of silica fibers, as first demonstrated experimentally by Watanabe et al[2].
1994 Conference on Lasers and Electro-Optics Europe, 1994
The advent of lossless graded-reflectivity mirrors (GRMs) is now widely recognized as an importan... more The advent of lossless graded-reflectivity mirrors (GRMs) is now widely recognized as an important headway in the field of optical resonators.1 When used as the feedback output mirror inside an unstable resonator cavity (Fig. 1), a GRM greatly improves the quality of the nearfield by yielding a wide beam with reduced ripples thanks to its tapered edges. In contrast, the more conventional unstable cavity yields an annular output beam with hard-edge truncation and disappointing beam quality for near-field applications.
Conference on Lasers and Electro-Optics Europe, 1996
The problem of controlling the parameters of laser radiation becomes particularly topical in view... more The problem of controlling the parameters of laser radiation becomes particularly topical in view of the widespread use of lasers in medicine and technological processes. In this paper, we present the results of investigations of the possibility to form beams with different orders of super-Gaussian profile at the output of a stable laser cavity with the help of an active mirror. As shown in Ref.[1], in order to get these intensity profiles, it is necessary to construct specially calculated profiles of minor surface. As an example, on Fig.1 curve "A" represents such a surface profile. We tried to reproduce this shape with the help of a deformable bimorph minor (curve "B" on Fig.1). Since this profile was symmetrical, we used a minor with ring control electrodes. Such minor was a circular concave semipassive bimorph one with three electrodes. To minimize the root-mean-square (RMS) error between our profile and the necessary one, we combined the real (measured by interferometer) response functions of our minor with different weights. In practice, this amounts to applying a particular voltage to the electrodes of the deformable minor. As shown in Fig.1 (corresponding to a super-Gaussian of order 8), we were able to reproduce the appropriate minor profiles with a corresponding RMS enor of only 0.03% (curve "B"). Figure 2 compares the corresponding calculated near-field distributions (including saturation and edge diffraction effects) for a 2 m long stable cavity. The nearly identical associated far-fields are depicted on Fig. 3. A comparison with a conventional spherical resonator designed to yield a similar output beam divergence allows us to expect ≈ 30% power increase owing to the higher extraction efficiency of super-Gaussian beam profiles. Similar conclusions have been reached for a super-Gaussian of order 6. These calculations make us believe that our intracavity bimorph deformable mirror with only three control elements is able to reproduce super-Gaussian output radiation of the CW CO2 laser with a stable cavity. An experiment to verify this is under way.
Conference on Lasers and Electro-Optics Europe, Aug 24, 2005
Optical resonators designed for lowto medium-gain lasers generally consist of “stable” cavities u... more Optical resonators designed for lowto medium-gain lasers generally consist of “stable” cavities using spherical mirrors. The nearly ideal Gaussian fundamental mode profile of such resonators is advantageous in terms of beam quality and reduced diffraction losses. However, for laser applications requiring single transverse mode operation, the stable geometry presents a serious drawback in terms of energy efficiency. The small beamwaist of the confined fundamental mode exploits only a reduced fraction of the available gain section and the poor modal selectivity limits the degree of saturation that can be reached in the single mode regime. The idea of using aspherical mirrors (graded-phase mirrors GPMs) has been proposed in the early days of laser development. The objective was to increase the effective mode cross section by improving the uniformity of the fundamental mode. However, in absence of guidelines, those studies were made on a trial-and-error basis and the conclusions were far from exhaustive. The interest for aspherical mirrors was also refrained by limitations in technology. Over the last few years, we have proposed’ and experimentally demonstrated* a different approach in the design of stable resonators using GPMs. These so-called ”custom phase-conjugate resonators” make it possible for the user to specify the output profile, which is the most appropriate to a given application. The design procedure exploits the fact that the wavefront of a lossless mode matches the mirror surfaces so that the reflected field is the phase-conjugate version of the incident field; the beam retums on itself after reflection (Fig. 1). So, in order to shape the fundamental mode as desired, the trick simply consists in deforming the mirror profile to make it correspond to the wavefront of this mode once propagated (numerically) up to the mirror position.’ Because the phase conjugation process here is passive and,
ABSTRACT Citation C. Paré, A. Villenueve, P. -. Bélanger, N. Bélanger, and N. J. Doran, &quot... more ABSTRACT Citation C. Paré, A. Villenueve, P. -. Bélanger, N. Bélanger, and N. J. Doran, "Dispersion and Self-Phase Modulation Compensation Based on a Negative Nonlinearity," in Integrated Photonics Research, Vol. 6 of 1996 OSA Technical Digest Series (Optical Society of America, 1996), paper IThA7. http://www.opticsinfobase.org/abstract.cfm?URI=IPR-1996-IThA7
Nonlinear Guided Waves and Their Applications, 1998
It is now widely recognized that the so-called technique of dispersion management represents a ma... more It is now widely recognized that the so-called technique of dispersion management represents a major headway for both NRZ and soliton communication systems (for a recent review, see [1,2]). Thanks to a low average dispersion, the Gordon-Haus timing jitter, deleterious to soliton systems, can be minimized and the observed enhancement of the pulse's energy implies a better signal-to-noise ratio, hence improving the bit-error rate at the reception. The main predictions of numerical simulations having been confirmed experimentally [3,4], it now seems natural to look for simple design tools in order to optimize future dispersion-managed soliton communication links.
electron beam is generated with a modified projection television gun. It has an energy of 7-15 ke... more electron beam is generated with a modified projection television gun. It has an energy of 7-15 keV and a current of up to 1 mA. The focussed electron beam has an elongated spot size of approximately 200 pm by 20 pm and can be magnetically scanned along the bar length with frequencies up to 100 kHz. The optical near field (NF), the far field parallel to the epitaxial layers (FF,,), and the output power are given in Fig. 2 as a function of input current. These are measured at one position with a nonscanning pulsed electron beam at 8 keV. The output power shows the well-known threshold behaviour. At threshold, the input power is about a factor of 4-6 times higher than the power required to operate a similar laser structure as a diode laser. This can be understood quantitatively, as energy is lost by backscattering and heat generation. At the laser threshold, the NF narrows appreciably to values below 20 pm (FWHM), indicating that more than 50 laser positions can be resolved per millimeter bar length. The FF,, is 5" (FWHM) as can be seen in the figure, and it does not depend on the input power. The Far Field perpendicular to the epitaxial layers was measured to be 50" (FWHM), a value that was expected from the thickness and composition of the epitaxial layers. The light output as a function of position on the bar is given in Fig. 3. A fairly homogeneous emission is observed at an output power of more than 20 mW. Some local dips indicate the presence of defects and/or damage originating from handling and mounting the laser bar. The electron beam has a scan velocity of 1000 m/s, scanning 5 mm in 5 ps. With 50 addressable lasers per millimeter of bar length, this corresponds to a laser scanner data rate of 50 Mbit/s. New applications such 5 30 g 20 ; 10
17th International Conference on Optical Fibre Sensors, 2005
ABSTRACT A quasi-distributed fibre optics polarimetric sensor has been studied both theoretically... more ABSTRACT A quasi-distributed fibre optics polarimetric sensor has been studied both theoretically and experimentally. Theoretical results demonstrate the feasibility of such a sensor when a polarization-maintaining optical fibre has been properly designed. Two designs are proposed. Distributed detection of water has been demonstrated with a standard polarization-maintaining fibre whose cladding was locally removed by chemical etching.
Abstract Ion-selective optodes offer potential for in-line monitoring of various processes. Fibre... more Abstract Ion-selective optodes offer potential for in-line monitoring of various processes. Fibre sensors were developed for H+, Ca2+, K+, Na+, NH4+ and NO3-. Applications in hydroponic culture optimization, soil characterization and anaerobic digester process ...
The translation of CARS imaging towards real time, high resolution, chemically selective endoscop... more The translation of CARS imaging towards real time, high resolution, chemically selective endoscopic tissue imaging applications is limited by a lack of sensitivity in CARS scanning probes sufficiently small for incorporation into endoscopes. We have developed here a custom double clad fiber (DCF)-based CARS probe which is designed to suppress the contaminant Four-Wave-Mixing (FWM) background generated within the fiber and integrated it into a fiber based scanning probe head of a few millimeters in diameter. The DCF includes a large mode area (LMA) core as a first means of reducing FWM generation by ~3 dB compared to commercially available, step-index single mode fibers. A micro-fabricated miniature optical filter (MOF) was grown on the distal end of the DCF to block the remaining FWM background from reaching the sample. The resulting probe was used to demonstrate high contrast images of polystyrene beads in the forward-CARS configuration with > 10 dB suppression of the FWM background. In epi-CARS geometry, images exhibited lower contrast due to the leakage of MOF-reflected FWM from the fiber core. Improvements concepts for the fiber probe are proposed for high contrast epi-CARS imaging to enable endoscopic implementation in clinical tissue assessment contexts, particularly in the early detection of endoluminal cancers and in tumor margin assessment.
Using a variational method, we have developed an approximate model of the dynamics of soliton cou... more Using a variational method, we have developed an approximate model of the dynamics of soliton coupling described by coupled nonlinear Schrodinger equations. The results are analytical and can be recast into a suggestive particlelike description providing a physical insight into the problem. The particular case of the nonlinear coherent coupler is emphasized, and an estimate of the soliton switching peak power is obtained. A symmetry-breaking instability is also described, in a simple way, with the potential-well picture.
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Papers by Claude Paré